1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-2016 Free Software Foundation, Inc.
5 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
6 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
23 @c To avoid file-name clashes between index.html and Index.html, when
24 @c the manual is produced on a Posix host and then moved to a
25 @c case-insensitive filesystem (e.g., MS-Windows), we separate the
26 @c indices into two: Concept Index and all the rest.
30 @c readline appendices use @vindex, @findex and @ftable,
31 @c annotate.texi and gdbmi use @findex.
34 @c !!set GDB manual's edition---not the same as GDB version!
35 @c This is updated by GNU Press.
38 @c !!set GDB edit command default editor
41 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
43 @c This is a dir.info fragment to support semi-automated addition of
44 @c manuals to an info tree.
45 @dircategory Software development
47 * Gdb: (gdb). The GNU debugger.
48 * gdbserver: (gdb) Server. The GNU debugging server.
52 @c man begin COPYRIGHT
53 Copyright @copyright{} 1988-2016 Free Software Foundation, Inc.
55 Permission is granted to copy, distribute and/or modify this document
56 under the terms of the GNU Free Documentation License, Version 1.3 or
57 any later version published by the Free Software Foundation; with the
58 Invariant Sections being ``Free Software'' and ``Free Software Needs
59 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
60 and with the Back-Cover Texts as in (a) below.
62 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
63 this GNU Manual. Buying copies from GNU Press supports the FSF in
64 developing GNU and promoting software freedom.''
69 This file documents the @sc{gnu} debugger @value{GDBN}.
71 This is the @value{EDITION} Edition, of @cite{Debugging with
72 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
73 @ifset VERSION_PACKAGE
74 @value{VERSION_PACKAGE}
76 Version @value{GDBVN}.
82 @title Debugging with @value{GDBN}
83 @subtitle The @sc{gnu} Source-Level Debugger
85 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
86 @ifset VERSION_PACKAGE
88 @subtitle @value{VERSION_PACKAGE}
90 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
94 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
95 \hfill {\it Debugging with @value{GDBN}}\par
96 \hfill \TeX{}info \texinfoversion\par
100 @vskip 0pt plus 1filll
101 Published by the Free Software Foundation @*
102 51 Franklin Street, Fifth Floor,
103 Boston, MA 02110-1301, USA@*
104 ISBN 978-0-9831592-3-0 @*
111 @node Top, Summary, (dir), (dir)
113 @top Debugging with @value{GDBN}
115 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
117 This is the @value{EDITION} Edition, for @value{GDBN}
118 @ifset VERSION_PACKAGE
119 @value{VERSION_PACKAGE}
121 Version @value{GDBVN}.
123 Copyright (C) 1988-2016 Free Software Foundation, Inc.
125 This edition of the GDB manual is dedicated to the memory of Fred
126 Fish. Fred was a long-standing contributor to GDB and to Free
127 software in general. We will miss him.
130 * Summary:: Summary of @value{GDBN}
131 * Sample Session:: A sample @value{GDBN} session
133 * Invocation:: Getting in and out of @value{GDBN}
134 * Commands:: @value{GDBN} commands
135 * Running:: Running programs under @value{GDBN}
136 * Stopping:: Stopping and continuing
137 * Reverse Execution:: Running programs backward
138 * Process Record and Replay:: Recording inferior's execution and replaying it
139 * Stack:: Examining the stack
140 * Source:: Examining source files
141 * Data:: Examining data
142 * Optimized Code:: Debugging optimized code
143 * Macros:: Preprocessor Macros
144 * Tracepoints:: Debugging remote targets non-intrusively
145 * Overlays:: Debugging programs that use overlays
147 * Languages:: Using @value{GDBN} with different languages
149 * Symbols:: Examining the symbol table
150 * Altering:: Altering execution
151 * GDB Files:: @value{GDBN} files
152 * Targets:: Specifying a debugging target
153 * Remote Debugging:: Debugging remote programs
154 * Configurations:: Configuration-specific information
155 * Controlling GDB:: Controlling @value{GDBN}
156 * Extending GDB:: Extending @value{GDBN}
157 * Interpreters:: Command Interpreters
158 * TUI:: @value{GDBN} Text User Interface
159 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
160 * GDB/MI:: @value{GDBN}'s Machine Interface.
161 * Annotations:: @value{GDBN}'s annotation interface.
162 * JIT Interface:: Using the JIT debugging interface.
163 * In-Process Agent:: In-Process Agent
165 * GDB Bugs:: Reporting bugs in @value{GDBN}
167 @ifset SYSTEM_READLINE
168 * Command Line Editing: (rluserman). Command Line Editing
169 * Using History Interactively: (history). Using History Interactively
171 @ifclear SYSTEM_READLINE
172 * Command Line Editing:: Command Line Editing
173 * Using History Interactively:: Using History Interactively
175 * In Memoriam:: In Memoriam
176 * Formatting Documentation:: How to format and print @value{GDBN} documentation
177 * Installing GDB:: Installing GDB
178 * Maintenance Commands:: Maintenance Commands
179 * Remote Protocol:: GDB Remote Serial Protocol
180 * Agent Expressions:: The GDB Agent Expression Mechanism
181 * Target Descriptions:: How targets can describe themselves to
183 * Operating System Information:: Getting additional information from
185 * Trace File Format:: GDB trace file format
186 * Index Section Format:: .gdb_index section format
187 * Man Pages:: Manual pages
188 * Copying:: GNU General Public License says
189 how you can copy and share GDB
190 * GNU Free Documentation License:: The license for this documentation
191 * Concept Index:: Index of @value{GDBN} concepts
192 * Command and Variable Index:: Index of @value{GDBN} commands, variables,
193 functions, and Python data types
201 @unnumbered Summary of @value{GDBN}
203 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
204 going on ``inside'' another program while it executes---or what another
205 program was doing at the moment it crashed.
207 @value{GDBN} can do four main kinds of things (plus other things in support of
208 these) to help you catch bugs in the act:
212 Start your program, specifying anything that might affect its behavior.
215 Make your program stop on specified conditions.
218 Examine what has happened, when your program has stopped.
221 Change things in your program, so you can experiment with correcting the
222 effects of one bug and go on to learn about another.
225 You can use @value{GDBN} to debug programs written in C and C@t{++}.
226 For more information, see @ref{Supported Languages,,Supported Languages}.
227 For more information, see @ref{C,,C and C++}.
229 Support for D is partial. For information on D, see
233 Support for Modula-2 is partial. For information on Modula-2, see
234 @ref{Modula-2,,Modula-2}.
236 Support for OpenCL C is partial. For information on OpenCL C, see
237 @ref{OpenCL C,,OpenCL C}.
240 Debugging Pascal programs which use sets, subranges, file variables, or
241 nested functions does not currently work. @value{GDBN} does not support
242 entering expressions, printing values, or similar features using Pascal
246 @value{GDBN} can be used to debug programs written in Fortran, although
247 it may be necessary to refer to some variables with a trailing
250 @value{GDBN} can be used to debug programs written in Objective-C,
251 using either the Apple/NeXT or the GNU Objective-C runtime.
254 * Free Software:: Freely redistributable software
255 * Free Documentation:: Free Software Needs Free Documentation
256 * Contributors:: Contributors to GDB
260 @unnumberedsec Free Software
262 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
263 General Public License
264 (GPL). The GPL gives you the freedom to copy or adapt a licensed
265 program---but every person getting a copy also gets with it the
266 freedom to modify that copy (which means that they must get access to
267 the source code), and the freedom to distribute further copies.
268 Typical software companies use copyrights to limit your freedoms; the
269 Free Software Foundation uses the GPL to preserve these freedoms.
271 Fundamentally, the General Public License is a license which says that
272 you have these freedoms and that you cannot take these freedoms away
275 @node Free Documentation
276 @unnumberedsec Free Software Needs Free Documentation
278 The biggest deficiency in the free software community today is not in
279 the software---it is the lack of good free documentation that we can
280 include with the free software. Many of our most important
281 programs do not come with free reference manuals and free introductory
282 texts. Documentation is an essential part of any software package;
283 when an important free software package does not come with a free
284 manual and a free tutorial, that is a major gap. We have many such
287 Consider Perl, for instance. The tutorial manuals that people
288 normally use are non-free. How did this come about? Because the
289 authors of those manuals published them with restrictive terms---no
290 copying, no modification, source files not available---which exclude
291 them from the free software world.
293 That wasn't the first time this sort of thing happened, and it was far
294 from the last. Many times we have heard a GNU user eagerly describe a
295 manual that he is writing, his intended contribution to the community,
296 only to learn that he had ruined everything by signing a publication
297 contract to make it non-free.
299 Free documentation, like free software, is a matter of freedom, not
300 price. The problem with the non-free manual is not that publishers
301 charge a price for printed copies---that in itself is fine. (The Free
302 Software Foundation sells printed copies of manuals, too.) The
303 problem is the restrictions on the use of the manual. Free manuals
304 are available in source code form, and give you permission to copy and
305 modify. Non-free manuals do not allow this.
307 The criteria of freedom for a free manual are roughly the same as for
308 free software. Redistribution (including the normal kinds of
309 commercial redistribution) must be permitted, so that the manual can
310 accompany every copy of the program, both on-line and on paper.
312 Permission for modification of the technical content is crucial too.
313 When people modify the software, adding or changing features, if they
314 are conscientious they will change the manual too---so they can
315 provide accurate and clear documentation for the modified program. A
316 manual that leaves you no choice but to write a new manual to document
317 a changed version of the program is not really available to our
320 Some kinds of limits on the way modification is handled are
321 acceptable. For example, requirements to preserve the original
322 author's copyright notice, the distribution terms, or the list of
323 authors, are ok. It is also no problem to require modified versions
324 to include notice that they were modified. Even entire sections that
325 may not be deleted or changed are acceptable, as long as they deal
326 with nontechnical topics (like this one). These kinds of restrictions
327 are acceptable because they don't obstruct the community's normal use
330 However, it must be possible to modify all the @emph{technical}
331 content of the manual, and then distribute the result in all the usual
332 media, through all the usual channels. Otherwise, the restrictions
333 obstruct the use of the manual, it is not free, and we need another
334 manual to replace it.
336 Please spread the word about this issue. Our community continues to
337 lose manuals to proprietary publishing. If we spread the word that
338 free software needs free reference manuals and free tutorials, perhaps
339 the next person who wants to contribute by writing documentation will
340 realize, before it is too late, that only free manuals contribute to
341 the free software community.
343 If you are writing documentation, please insist on publishing it under
344 the GNU Free Documentation License or another free documentation
345 license. Remember that this decision requires your approval---you
346 don't have to let the publisher decide. Some commercial publishers
347 will use a free license if you insist, but they will not propose the
348 option; it is up to you to raise the issue and say firmly that this is
349 what you want. If the publisher you are dealing with refuses, please
350 try other publishers. If you're not sure whether a proposed license
351 is free, write to @email{licensing@@gnu.org}.
353 You can encourage commercial publishers to sell more free, copylefted
354 manuals and tutorials by buying them, and particularly by buying
355 copies from the publishers that paid for their writing or for major
356 improvements. Meanwhile, try to avoid buying non-free documentation
357 at all. Check the distribution terms of a manual before you buy it,
358 and insist that whoever seeks your business must respect your freedom.
359 Check the history of the book, and try to reward the publishers that
360 have paid or pay the authors to work on it.
362 The Free Software Foundation maintains a list of free documentation
363 published by other publishers, at
364 @url{http://www.fsf.org/doc/other-free-books.html}.
367 @unnumberedsec Contributors to @value{GDBN}
369 Richard Stallman was the original author of @value{GDBN}, and of many
370 other @sc{gnu} programs. Many others have contributed to its
371 development. This section attempts to credit major contributors. One
372 of the virtues of free software is that everyone is free to contribute
373 to it; with regret, we cannot actually acknowledge everyone here. The
374 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
375 blow-by-blow account.
377 Changes much prior to version 2.0 are lost in the mists of time.
380 @emph{Plea:} Additions to this section are particularly welcome. If you
381 or your friends (or enemies, to be evenhanded) have been unfairly
382 omitted from this list, we would like to add your names!
385 So that they may not regard their many labors as thankless, we
386 particularly thank those who shepherded @value{GDBN} through major
388 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
389 Jim Blandy (release 4.18);
390 Jason Molenda (release 4.17);
391 Stan Shebs (release 4.14);
392 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
393 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
394 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
395 Jim Kingdon (releases 3.5, 3.4, and 3.3);
396 and Randy Smith (releases 3.2, 3.1, and 3.0).
398 Richard Stallman, assisted at various times by Peter TerMaat, Chris
399 Hanson, and Richard Mlynarik, handled releases through 2.8.
401 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
402 in @value{GDBN}, with significant additional contributions from Per
403 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
404 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
405 much general update work leading to release 3.0).
407 @value{GDBN} uses the BFD subroutine library to examine multiple
408 object-file formats; BFD was a joint project of David V.
409 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
411 David Johnson wrote the original COFF support; Pace Willison did
412 the original support for encapsulated COFF.
414 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
416 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
417 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
419 Jean-Daniel Fekete contributed Sun 386i support.
420 Chris Hanson improved the HP9000 support.
421 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
422 David Johnson contributed Encore Umax support.
423 Jyrki Kuoppala contributed Altos 3068 support.
424 Jeff Law contributed HP PA and SOM support.
425 Keith Packard contributed NS32K support.
426 Doug Rabson contributed Acorn Risc Machine support.
427 Bob Rusk contributed Harris Nighthawk CX-UX support.
428 Chris Smith contributed Convex support (and Fortran debugging).
429 Jonathan Stone contributed Pyramid support.
430 Michael Tiemann contributed SPARC support.
431 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
432 Pace Willison contributed Intel 386 support.
433 Jay Vosburgh contributed Symmetry support.
434 Marko Mlinar contributed OpenRISC 1000 support.
436 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
438 Rich Schaefer and Peter Schauer helped with support of SunOS shared
441 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
442 about several machine instruction sets.
444 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
445 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
446 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
447 and RDI targets, respectively.
449 Brian Fox is the author of the readline libraries providing
450 command-line editing and command history.
452 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
453 Modula-2 support, and contributed the Languages chapter of this manual.
455 Fred Fish wrote most of the support for Unix System Vr4.
456 He also enhanced the command-completion support to cover C@t{++} overloaded
459 Hitachi America (now Renesas America), Ltd. sponsored the support for
460 H8/300, H8/500, and Super-H processors.
462 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
464 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
467 Toshiba sponsored the support for the TX39 Mips processor.
469 Matsushita sponsored the support for the MN10200 and MN10300 processors.
471 Fujitsu sponsored the support for SPARClite and FR30 processors.
473 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
476 Michael Snyder added support for tracepoints.
478 Stu Grossman wrote gdbserver.
480 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
481 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
483 The following people at the Hewlett-Packard Company contributed
484 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
485 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
486 compiler, and the Text User Interface (nee Terminal User Interface):
487 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
488 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
489 provided HP-specific information in this manual.
491 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
492 Robert Hoehne made significant contributions to the DJGPP port.
494 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
495 development since 1991. Cygnus engineers who have worked on @value{GDBN}
496 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
497 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
498 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
499 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
500 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
501 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
502 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
503 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
504 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
505 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
506 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
507 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
508 Zuhn have made contributions both large and small.
510 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
511 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
513 Jim Blandy added support for preprocessor macros, while working for Red
516 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
517 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
518 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
519 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
520 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
521 with the migration of old architectures to this new framework.
523 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
524 unwinder framework, this consisting of a fresh new design featuring
525 frame IDs, independent frame sniffers, and the sentinel frame. Mark
526 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
527 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
528 trad unwinders. The architecture-specific changes, each involving a
529 complete rewrite of the architecture's frame code, were carried out by
530 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
531 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
532 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
533 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
536 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
537 Tensilica, Inc.@: contributed support for Xtensa processors. Others
538 who have worked on the Xtensa port of @value{GDBN} in the past include
539 Steve Tjiang, John Newlin, and Scott Foehner.
541 Michael Eager and staff of Xilinx, Inc., contributed support for the
542 Xilinx MicroBlaze architecture.
545 @chapter A Sample @value{GDBN} Session
547 You can use this manual at your leisure to read all about @value{GDBN}.
548 However, a handful of commands are enough to get started using the
549 debugger. This chapter illustrates those commands.
552 In this sample session, we emphasize user input like this: @b{input},
553 to make it easier to pick out from the surrounding output.
556 @c FIXME: this example may not be appropriate for some configs, where
557 @c FIXME...primary interest is in remote use.
559 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
560 processor) exhibits the following bug: sometimes, when we change its
561 quote strings from the default, the commands used to capture one macro
562 definition within another stop working. In the following short @code{m4}
563 session, we define a macro @code{foo} which expands to @code{0000}; we
564 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
565 same thing. However, when we change the open quote string to
566 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
567 procedure fails to define a new synonym @code{baz}:
576 @b{define(bar,defn(`foo'))}
580 @b{changequote(<QUOTE>,<UNQUOTE>)}
582 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
585 m4: End of input: 0: fatal error: EOF in string
589 Let us use @value{GDBN} to try to see what is going on.
592 $ @b{@value{GDBP} m4}
593 @c FIXME: this falsifies the exact text played out, to permit smallbook
594 @c FIXME... format to come out better.
595 @value{GDBN} is free software and you are welcome to distribute copies
596 of it under certain conditions; type "show copying" to see
598 There is absolutely no warranty for @value{GDBN}; type "show warranty"
601 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
606 @value{GDBN} reads only enough symbol data to know where to find the
607 rest when needed; as a result, the first prompt comes up very quickly.
608 We now tell @value{GDBN} to use a narrower display width than usual, so
609 that examples fit in this manual.
612 (@value{GDBP}) @b{set width 70}
616 We need to see how the @code{m4} built-in @code{changequote} works.
617 Having looked at the source, we know the relevant subroutine is
618 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
619 @code{break} command.
622 (@value{GDBP}) @b{break m4_changequote}
623 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
627 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
628 control; as long as control does not reach the @code{m4_changequote}
629 subroutine, the program runs as usual:
632 (@value{GDBP}) @b{run}
633 Starting program: /work/Editorial/gdb/gnu/m4/m4
641 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
642 suspends execution of @code{m4}, displaying information about the
643 context where it stops.
646 @b{changequote(<QUOTE>,<UNQUOTE>)}
648 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
650 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
654 Now we use the command @code{n} (@code{next}) to advance execution to
655 the next line of the current function.
659 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
664 @code{set_quotes} looks like a promising subroutine. We can go into it
665 by using the command @code{s} (@code{step}) instead of @code{next}.
666 @code{step} goes to the next line to be executed in @emph{any}
667 subroutine, so it steps into @code{set_quotes}.
671 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
673 530 if (lquote != def_lquote)
677 The display that shows the subroutine where @code{m4} is now
678 suspended (and its arguments) is called a stack frame display. It
679 shows a summary of the stack. We can use the @code{backtrace}
680 command (which can also be spelled @code{bt}), to see where we are
681 in the stack as a whole: the @code{backtrace} command displays a
682 stack frame for each active subroutine.
685 (@value{GDBP}) @b{bt}
686 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
688 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
690 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
691 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
693 #4 0x79dc in expand_input () at macro.c:40
694 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
698 We step through a few more lines to see what happens. The first two
699 times, we can use @samp{s}; the next two times we use @code{n} to avoid
700 falling into the @code{xstrdup} subroutine.
704 0x3b5c 532 if (rquote != def_rquote)
706 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
707 def_lquote : xstrdup(lq);
709 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
712 538 len_lquote = strlen(rquote);
716 The last line displayed looks a little odd; we can examine the variables
717 @code{lquote} and @code{rquote} to see if they are in fact the new left
718 and right quotes we specified. We use the command @code{p}
719 (@code{print}) to see their values.
722 (@value{GDBP}) @b{p lquote}
723 $1 = 0x35d40 "<QUOTE>"
724 (@value{GDBP}) @b{p rquote}
725 $2 = 0x35d50 "<UNQUOTE>"
729 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
730 To look at some context, we can display ten lines of source
731 surrounding the current line with the @code{l} (@code{list}) command.
737 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
739 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
742 538 len_lquote = strlen(rquote);
743 539 len_rquote = strlen(lquote);
750 Let us step past the two lines that set @code{len_lquote} and
751 @code{len_rquote}, and then examine the values of those variables.
755 539 len_rquote = strlen(lquote);
758 (@value{GDBP}) @b{p len_lquote}
760 (@value{GDBP}) @b{p len_rquote}
765 That certainly looks wrong, assuming @code{len_lquote} and
766 @code{len_rquote} are meant to be the lengths of @code{lquote} and
767 @code{rquote} respectively. We can set them to better values using
768 the @code{p} command, since it can print the value of
769 any expression---and that expression can include subroutine calls and
773 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
775 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
780 Is that enough to fix the problem of using the new quotes with the
781 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
782 executing with the @code{c} (@code{continue}) command, and then try the
783 example that caused trouble initially:
789 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
796 Success! The new quotes now work just as well as the default ones. The
797 problem seems to have been just the two typos defining the wrong
798 lengths. We allow @code{m4} exit by giving it an EOF as input:
802 Program exited normally.
806 The message @samp{Program exited normally.} is from @value{GDBN}; it
807 indicates @code{m4} has finished executing. We can end our @value{GDBN}
808 session with the @value{GDBN} @code{quit} command.
811 (@value{GDBP}) @b{quit}
815 @chapter Getting In and Out of @value{GDBN}
817 This chapter discusses how to start @value{GDBN}, and how to get out of it.
821 type @samp{@value{GDBP}} to start @value{GDBN}.
823 type @kbd{quit} or @kbd{Ctrl-d} to exit.
827 * Invoking GDB:: How to start @value{GDBN}
828 * Quitting GDB:: How to quit @value{GDBN}
829 * Shell Commands:: How to use shell commands inside @value{GDBN}
830 * Logging Output:: How to log @value{GDBN}'s output to a file
834 @section Invoking @value{GDBN}
836 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
837 @value{GDBN} reads commands from the terminal until you tell it to exit.
839 You can also run @code{@value{GDBP}} with a variety of arguments and options,
840 to specify more of your debugging environment at the outset.
842 The command-line options described here are designed
843 to cover a variety of situations; in some environments, some of these
844 options may effectively be unavailable.
846 The most usual way to start @value{GDBN} is with one argument,
847 specifying an executable program:
850 @value{GDBP} @var{program}
854 You can also start with both an executable program and a core file
858 @value{GDBP} @var{program} @var{core}
861 You can, instead, specify a process ID as a second argument, if you want
862 to debug a running process:
865 @value{GDBP} @var{program} 1234
869 would attach @value{GDBN} to process @code{1234} (unless you also have a file
870 named @file{1234}; @value{GDBN} does check for a core file first).
872 Taking advantage of the second command-line argument requires a fairly
873 complete operating system; when you use @value{GDBN} as a remote
874 debugger attached to a bare board, there may not be any notion of
875 ``process'', and there is often no way to get a core dump. @value{GDBN}
876 will warn you if it is unable to attach or to read core dumps.
878 You can optionally have @code{@value{GDBP}} pass any arguments after the
879 executable file to the inferior using @code{--args}. This option stops
882 @value{GDBP} --args gcc -O2 -c foo.c
884 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
885 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
887 You can run @code{@value{GDBP}} without printing the front material, which describes
888 @value{GDBN}'s non-warranty, by specifying @code{--silent}
889 (or @code{-q}/@code{--quiet}):
892 @value{GDBP} --silent
896 You can further control how @value{GDBN} starts up by using command-line
897 options. @value{GDBN} itself can remind you of the options available.
907 to display all available options and briefly describe their use
908 (@samp{@value{GDBP} -h} is a shorter equivalent).
910 All options and command line arguments you give are processed
911 in sequential order. The order makes a difference when the
912 @samp{-x} option is used.
916 * File Options:: Choosing files
917 * Mode Options:: Choosing modes
918 * Startup:: What @value{GDBN} does during startup
922 @subsection Choosing Files
924 When @value{GDBN} starts, it reads any arguments other than options as
925 specifying an executable file and core file (or process ID). This is
926 the same as if the arguments were specified by the @samp{-se} and
927 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
928 first argument that does not have an associated option flag as
929 equivalent to the @samp{-se} option followed by that argument; and the
930 second argument that does not have an associated option flag, if any, as
931 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
932 If the second argument begins with a decimal digit, @value{GDBN} will
933 first attempt to attach to it as a process, and if that fails, attempt
934 to open it as a corefile. If you have a corefile whose name begins with
935 a digit, you can prevent @value{GDBN} from treating it as a pid by
936 prefixing it with @file{./}, e.g.@: @file{./12345}.
938 If @value{GDBN} has not been configured to included core file support,
939 such as for most embedded targets, then it will complain about a second
940 argument and ignore it.
942 Many options have both long and short forms; both are shown in the
943 following list. @value{GDBN} also recognizes the long forms if you truncate
944 them, so long as enough of the option is present to be unambiguous.
945 (If you prefer, you can flag option arguments with @samp{--} rather
946 than @samp{-}, though we illustrate the more usual convention.)
948 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
949 @c way, both those who look for -foo and --foo in the index, will find
953 @item -symbols @var{file}
955 @cindex @code{--symbols}
957 Read symbol table from file @var{file}.
959 @item -exec @var{file}
961 @cindex @code{--exec}
963 Use file @var{file} as the executable file to execute when appropriate,
964 and for examining pure data in conjunction with a core dump.
968 Read symbol table from file @var{file} and use it as the executable
971 @item -core @var{file}
973 @cindex @code{--core}
975 Use file @var{file} as a core dump to examine.
977 @item -pid @var{number}
978 @itemx -p @var{number}
981 Connect to process ID @var{number}, as with the @code{attach} command.
983 @item -command @var{file}
985 @cindex @code{--command}
987 Execute commands from file @var{file}. The contents of this file is
988 evaluated exactly as the @code{source} command would.
989 @xref{Command Files,, Command files}.
991 @item -eval-command @var{command}
992 @itemx -ex @var{command}
993 @cindex @code{--eval-command}
995 Execute a single @value{GDBN} command.
997 This option may be used multiple times to call multiple commands. It may
998 also be interleaved with @samp{-command} as required.
1001 @value{GDBP} -ex 'target sim' -ex 'load' \
1002 -x setbreakpoints -ex 'run' a.out
1005 @item -init-command @var{file}
1006 @itemx -ix @var{file}
1007 @cindex @code{--init-command}
1009 Execute commands from file @var{file} before loading the inferior (but
1010 after loading gdbinit files).
1013 @item -init-eval-command @var{command}
1014 @itemx -iex @var{command}
1015 @cindex @code{--init-eval-command}
1017 Execute a single @value{GDBN} command before loading the inferior (but
1018 after loading gdbinit files).
1021 @item -directory @var{directory}
1022 @itemx -d @var{directory}
1023 @cindex @code{--directory}
1025 Add @var{directory} to the path to search for source and script files.
1029 @cindex @code{--readnow}
1031 Read each symbol file's entire symbol table immediately, rather than
1032 the default, which is to read it incrementally as it is needed.
1033 This makes startup slower, but makes future operations faster.
1038 @subsection Choosing Modes
1040 You can run @value{GDBN} in various alternative modes---for example, in
1041 batch mode or quiet mode.
1049 Do not execute commands found in any initialization file.
1050 There are three init files, loaded in the following order:
1053 @item @file{system.gdbinit}
1054 This is the system-wide init file.
1055 Its location is specified with the @code{--with-system-gdbinit}
1056 configure option (@pxref{System-wide configuration}).
1057 It is loaded first when @value{GDBN} starts, before command line options
1058 have been processed.
1059 @item @file{~/.gdbinit}
1060 This is the init file in your home directory.
1061 It is loaded next, after @file{system.gdbinit}, and before
1062 command options have been processed.
1063 @item @file{./.gdbinit}
1064 This is the init file in the current directory.
1065 It is loaded last, after command line options other than @code{-x} and
1066 @code{-ex} have been processed. Command line options @code{-x} and
1067 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1070 For further documentation on startup processing, @xref{Startup}.
1071 For documentation on how to write command files,
1072 @xref{Command Files,,Command Files}.
1077 Do not execute commands found in @file{~/.gdbinit}, the init file
1078 in your home directory.
1084 @cindex @code{--quiet}
1085 @cindex @code{--silent}
1087 ``Quiet''. Do not print the introductory and copyright messages. These
1088 messages are also suppressed in batch mode.
1091 @cindex @code{--batch}
1092 Run in batch mode. Exit with status @code{0} after processing all the
1093 command files specified with @samp{-x} (and all commands from
1094 initialization files, if not inhibited with @samp{-n}). Exit with
1095 nonzero status if an error occurs in executing the @value{GDBN} commands
1096 in the command files. Batch mode also disables pagination, sets unlimited
1097 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1098 off} were in effect (@pxref{Messages/Warnings}).
1100 Batch mode may be useful for running @value{GDBN} as a filter, for
1101 example to download and run a program on another computer; in order to
1102 make this more useful, the message
1105 Program exited normally.
1109 (which is ordinarily issued whenever a program running under
1110 @value{GDBN} control terminates) is not issued when running in batch
1114 @cindex @code{--batch-silent}
1115 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1116 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1117 unaffected). This is much quieter than @samp{-silent} and would be useless
1118 for an interactive session.
1120 This is particularly useful when using targets that give @samp{Loading section}
1121 messages, for example.
1123 Note that targets that give their output via @value{GDBN}, as opposed to
1124 writing directly to @code{stdout}, will also be made silent.
1126 @item -return-child-result
1127 @cindex @code{--return-child-result}
1128 The return code from @value{GDBN} will be the return code from the child
1129 process (the process being debugged), with the following exceptions:
1133 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1134 internal error. In this case the exit code is the same as it would have been
1135 without @samp{-return-child-result}.
1137 The user quits with an explicit value. E.g., @samp{quit 1}.
1139 The child process never runs, or is not allowed to terminate, in which case
1140 the exit code will be -1.
1143 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1144 when @value{GDBN} is being used as a remote program loader or simulator
1149 @cindex @code{--nowindows}
1151 ``No windows''. If @value{GDBN} comes with a graphical user interface
1152 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1153 interface. If no GUI is available, this option has no effect.
1157 @cindex @code{--windows}
1159 If @value{GDBN} includes a GUI, then this option requires it to be
1162 @item -cd @var{directory}
1164 Run @value{GDBN} using @var{directory} as its working directory,
1165 instead of the current directory.
1167 @item -data-directory @var{directory}
1168 @itemx -D @var{directory}
1169 @cindex @code{--data-directory}
1171 Run @value{GDBN} using @var{directory} as its data directory.
1172 The data directory is where @value{GDBN} searches for its
1173 auxiliary files. @xref{Data Files}.
1177 @cindex @code{--fullname}
1179 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1180 subprocess. It tells @value{GDBN} to output the full file name and line
1181 number in a standard, recognizable fashion each time a stack frame is
1182 displayed (which includes each time your program stops). This
1183 recognizable format looks like two @samp{\032} characters, followed by
1184 the file name, line number and character position separated by colons,
1185 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1186 @samp{\032} characters as a signal to display the source code for the
1189 @item -annotate @var{level}
1190 @cindex @code{--annotate}
1191 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1192 effect is identical to using @samp{set annotate @var{level}}
1193 (@pxref{Annotations}). The annotation @var{level} controls how much
1194 information @value{GDBN} prints together with its prompt, values of
1195 expressions, source lines, and other types of output. Level 0 is the
1196 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1197 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1198 that control @value{GDBN}, and level 2 has been deprecated.
1200 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1204 @cindex @code{--args}
1205 Change interpretation of command line so that arguments following the
1206 executable file are passed as command line arguments to the inferior.
1207 This option stops option processing.
1209 @item -baud @var{bps}
1211 @cindex @code{--baud}
1213 Set the line speed (baud rate or bits per second) of any serial
1214 interface used by @value{GDBN} for remote debugging.
1216 @item -l @var{timeout}
1218 Set the timeout (in seconds) of any communication used by @value{GDBN}
1219 for remote debugging.
1221 @item -tty @var{device}
1222 @itemx -t @var{device}
1223 @cindex @code{--tty}
1225 Run using @var{device} for your program's standard input and output.
1226 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1228 @c resolve the situation of these eventually
1230 @cindex @code{--tui}
1231 Activate the @dfn{Text User Interface} when starting. The Text User
1232 Interface manages several text windows on the terminal, showing
1233 source, assembly, registers and @value{GDBN} command outputs
1234 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1235 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1236 Using @value{GDBN} under @sc{gnu} Emacs}).
1238 @item -interpreter @var{interp}
1239 @cindex @code{--interpreter}
1240 Use the interpreter @var{interp} for interface with the controlling
1241 program or device. This option is meant to be set by programs which
1242 communicate with @value{GDBN} using it as a back end.
1243 @xref{Interpreters, , Command Interpreters}.
1245 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1246 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1247 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1248 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1249 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1250 @sc{gdb/mi} interfaces are no longer supported.
1253 @cindex @code{--write}
1254 Open the executable and core files for both reading and writing. This
1255 is equivalent to the @samp{set write on} command inside @value{GDBN}
1259 @cindex @code{--statistics}
1260 This option causes @value{GDBN} to print statistics about time and
1261 memory usage after it completes each command and returns to the prompt.
1264 @cindex @code{--version}
1265 This option causes @value{GDBN} to print its version number and
1266 no-warranty blurb, and exit.
1268 @item -configuration
1269 @cindex @code{--configuration}
1270 This option causes @value{GDBN} to print details about its build-time
1271 configuration parameters, and then exit. These details can be
1272 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1277 @subsection What @value{GDBN} Does During Startup
1278 @cindex @value{GDBN} startup
1280 Here's the description of what @value{GDBN} does during session startup:
1284 Sets up the command interpreter as specified by the command line
1285 (@pxref{Mode Options, interpreter}).
1289 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1290 used when building @value{GDBN}; @pxref{System-wide configuration,
1291 ,System-wide configuration and settings}) and executes all the commands in
1294 @anchor{Home Directory Init File}
1296 Reads the init file (if any) in your home directory@footnote{On
1297 DOS/Windows systems, the home directory is the one pointed to by the
1298 @code{HOME} environment variable.} and executes all the commands in
1301 @anchor{Option -init-eval-command}
1303 Executes commands and command files specified by the @samp{-iex} and
1304 @samp{-ix} options in their specified order. Usually you should use the
1305 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1306 settings before @value{GDBN} init files get executed and before inferior
1310 Processes command line options and operands.
1312 @anchor{Init File in the Current Directory during Startup}
1314 Reads and executes the commands from init file (if any) in the current
1315 working directory as long as @samp{set auto-load local-gdbinit} is set to
1316 @samp{on} (@pxref{Init File in the Current Directory}).
1317 This is only done if the current directory is
1318 different from your home directory. Thus, you can have more than one
1319 init file, one generic in your home directory, and another, specific
1320 to the program you are debugging, in the directory where you invoke
1324 If the command line specified a program to debug, or a process to
1325 attach to, or a core file, @value{GDBN} loads any auto-loaded
1326 scripts provided for the program or for its loaded shared libraries.
1327 @xref{Auto-loading}.
1329 If you wish to disable the auto-loading during startup,
1330 you must do something like the following:
1333 $ gdb -iex "set auto-load python-scripts off" myprogram
1336 Option @samp{-ex} does not work because the auto-loading is then turned
1340 Executes commands and command files specified by the @samp{-ex} and
1341 @samp{-x} options in their specified order. @xref{Command Files}, for
1342 more details about @value{GDBN} command files.
1345 Reads the command history recorded in the @dfn{history file}.
1346 @xref{Command History}, for more details about the command history and the
1347 files where @value{GDBN} records it.
1350 Init files use the same syntax as @dfn{command files} (@pxref{Command
1351 Files}) and are processed by @value{GDBN} in the same way. The init
1352 file in your home directory can set options (such as @samp{set
1353 complaints}) that affect subsequent processing of command line options
1354 and operands. Init files are not executed if you use the @samp{-nx}
1355 option (@pxref{Mode Options, ,Choosing Modes}).
1357 To display the list of init files loaded by gdb at startup, you
1358 can use @kbd{gdb --help}.
1360 @cindex init file name
1361 @cindex @file{.gdbinit}
1362 @cindex @file{gdb.ini}
1363 The @value{GDBN} init files are normally called @file{.gdbinit}.
1364 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1365 the limitations of file names imposed by DOS filesystems. The Windows
1366 port of @value{GDBN} uses the standard name, but if it finds a
1367 @file{gdb.ini} file in your home directory, it warns you about that
1368 and suggests to rename the file to the standard name.
1372 @section Quitting @value{GDBN}
1373 @cindex exiting @value{GDBN}
1374 @cindex leaving @value{GDBN}
1377 @kindex quit @r{[}@var{expression}@r{]}
1378 @kindex q @r{(@code{quit})}
1379 @item quit @r{[}@var{expression}@r{]}
1381 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1382 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1383 do not supply @var{expression}, @value{GDBN} will terminate normally;
1384 otherwise it will terminate using the result of @var{expression} as the
1389 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1390 terminates the action of any @value{GDBN} command that is in progress and
1391 returns to @value{GDBN} command level. It is safe to type the interrupt
1392 character at any time because @value{GDBN} does not allow it to take effect
1393 until a time when it is safe.
1395 If you have been using @value{GDBN} to control an attached process or
1396 device, you can release it with the @code{detach} command
1397 (@pxref{Attach, ,Debugging an Already-running Process}).
1399 @node Shell Commands
1400 @section Shell Commands
1402 If you need to execute occasional shell commands during your
1403 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1404 just use the @code{shell} command.
1409 @cindex shell escape
1410 @item shell @var{command-string}
1411 @itemx !@var{command-string}
1412 Invoke a standard shell to execute @var{command-string}.
1413 Note that no space is needed between @code{!} and @var{command-string}.
1414 If it exists, the environment variable @code{SHELL} determines which
1415 shell to run. Otherwise @value{GDBN} uses the default shell
1416 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1419 The utility @code{make} is often needed in development environments.
1420 You do not have to use the @code{shell} command for this purpose in
1425 @cindex calling make
1426 @item make @var{make-args}
1427 Execute the @code{make} program with the specified
1428 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1431 @node Logging Output
1432 @section Logging Output
1433 @cindex logging @value{GDBN} output
1434 @cindex save @value{GDBN} output to a file
1436 You may want to save the output of @value{GDBN} commands to a file.
1437 There are several commands to control @value{GDBN}'s logging.
1441 @item set logging on
1443 @item set logging off
1445 @cindex logging file name
1446 @item set logging file @var{file}
1447 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1448 @item set logging overwrite [on|off]
1449 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1450 you want @code{set logging on} to overwrite the logfile instead.
1451 @item set logging redirect [on|off]
1452 By default, @value{GDBN} output will go to both the terminal and the logfile.
1453 Set @code{redirect} if you want output to go only to the log file.
1454 @kindex show logging
1456 Show the current values of the logging settings.
1460 @chapter @value{GDBN} Commands
1462 You can abbreviate a @value{GDBN} command to the first few letters of the command
1463 name, if that abbreviation is unambiguous; and you can repeat certain
1464 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1465 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1466 show you the alternatives available, if there is more than one possibility).
1469 * Command Syntax:: How to give commands to @value{GDBN}
1470 * Completion:: Command completion
1471 * Help:: How to ask @value{GDBN} for help
1474 @node Command Syntax
1475 @section Command Syntax
1477 A @value{GDBN} command is a single line of input. There is no limit on
1478 how long it can be. It starts with a command name, which is followed by
1479 arguments whose meaning depends on the command name. For example, the
1480 command @code{step} accepts an argument which is the number of times to
1481 step, as in @samp{step 5}. You can also use the @code{step} command
1482 with no arguments. Some commands do not allow any arguments.
1484 @cindex abbreviation
1485 @value{GDBN} command names may always be truncated if that abbreviation is
1486 unambiguous. Other possible command abbreviations are listed in the
1487 documentation for individual commands. In some cases, even ambiguous
1488 abbreviations are allowed; for example, @code{s} is specially defined as
1489 equivalent to @code{step} even though there are other commands whose
1490 names start with @code{s}. You can test abbreviations by using them as
1491 arguments to the @code{help} command.
1493 @cindex repeating commands
1494 @kindex RET @r{(repeat last command)}
1495 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1496 repeat the previous command. Certain commands (for example, @code{run})
1497 will not repeat this way; these are commands whose unintentional
1498 repetition might cause trouble and which you are unlikely to want to
1499 repeat. User-defined commands can disable this feature; see
1500 @ref{Define, dont-repeat}.
1502 The @code{list} and @code{x} commands, when you repeat them with
1503 @key{RET}, construct new arguments rather than repeating
1504 exactly as typed. This permits easy scanning of source or memory.
1506 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1507 output, in a way similar to the common utility @code{more}
1508 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1509 @key{RET} too many in this situation, @value{GDBN} disables command
1510 repetition after any command that generates this sort of display.
1512 @kindex # @r{(a comment)}
1514 Any text from a @kbd{#} to the end of the line is a comment; it does
1515 nothing. This is useful mainly in command files (@pxref{Command
1516 Files,,Command Files}).
1518 @cindex repeating command sequences
1519 @kindex Ctrl-o @r{(operate-and-get-next)}
1520 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1521 commands. This command accepts the current line, like @key{RET}, and
1522 then fetches the next line relative to the current line from the history
1526 @section Command Completion
1529 @cindex word completion
1530 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1531 only one possibility; it can also show you what the valid possibilities
1532 are for the next word in a command, at any time. This works for @value{GDBN}
1533 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1535 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1536 of a word. If there is only one possibility, @value{GDBN} fills in the
1537 word, and waits for you to finish the command (or press @key{RET} to
1538 enter it). For example, if you type
1540 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1541 @c complete accuracy in these examples; space introduced for clarity.
1542 @c If texinfo enhancements make it unnecessary, it would be nice to
1543 @c replace " @key" by "@key" in the following...
1545 (@value{GDBP}) info bre @key{TAB}
1549 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1550 the only @code{info} subcommand beginning with @samp{bre}:
1553 (@value{GDBP}) info breakpoints
1557 You can either press @key{RET} at this point, to run the @code{info
1558 breakpoints} command, or backspace and enter something else, if
1559 @samp{breakpoints} does not look like the command you expected. (If you
1560 were sure you wanted @code{info breakpoints} in the first place, you
1561 might as well just type @key{RET} immediately after @samp{info bre},
1562 to exploit command abbreviations rather than command completion).
1564 If there is more than one possibility for the next word when you press
1565 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1566 characters and try again, or just press @key{TAB} a second time;
1567 @value{GDBN} displays all the possible completions for that word. For
1568 example, you might want to set a breakpoint on a subroutine whose name
1569 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1570 just sounds the bell. Typing @key{TAB} again displays all the
1571 function names in your program that begin with those characters, for
1575 (@value{GDBP}) b make_ @key{TAB}
1576 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1577 make_a_section_from_file make_environ
1578 make_abs_section make_function_type
1579 make_blockvector make_pointer_type
1580 make_cleanup make_reference_type
1581 make_command make_symbol_completion_list
1582 (@value{GDBP}) b make_
1586 After displaying the available possibilities, @value{GDBN} copies your
1587 partial input (@samp{b make_} in the example) so you can finish the
1590 If you just want to see the list of alternatives in the first place, you
1591 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1592 means @kbd{@key{META} ?}. You can type this either by holding down a
1593 key designated as the @key{META} shift on your keyboard (if there is
1594 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1596 If the number of possible completions is large, @value{GDBN} will
1597 print as much of the list as it has collected, as well as a message
1598 indicating that the list may be truncated.
1601 (@value{GDBP}) b m@key{TAB}@key{TAB}
1603 <... the rest of the possible completions ...>
1604 *** List may be truncated, max-completions reached. ***
1609 This behavior can be controlled with the following commands:
1612 @kindex set max-completions
1613 @item set max-completions @var{limit}
1614 @itemx set max-completions unlimited
1615 Set the maximum number of completion candidates. @value{GDBN} will
1616 stop looking for more completions once it collects this many candidates.
1617 This is useful when completing on things like function names as collecting
1618 all the possible candidates can be time consuming.
1619 The default value is 200. A value of zero disables tab-completion.
1620 Note that setting either no limit or a very large limit can make
1622 @kindex show max-completions
1623 @item show max-completions
1624 Show the maximum number of candidates that @value{GDBN} will collect and show
1628 @cindex quotes in commands
1629 @cindex completion of quoted strings
1630 Sometimes the string you need, while logically a ``word'', may contain
1631 parentheses or other characters that @value{GDBN} normally excludes from
1632 its notion of a word. To permit word completion to work in this
1633 situation, you may enclose words in @code{'} (single quote marks) in
1634 @value{GDBN} commands.
1636 The most likely situation where you might need this is in typing the
1637 name of a C@t{++} function. This is because C@t{++} allows function
1638 overloading (multiple definitions of the same function, distinguished
1639 by argument type). For example, when you want to set a breakpoint you
1640 may need to distinguish whether you mean the version of @code{name}
1641 that takes an @code{int} parameter, @code{name(int)}, or the version
1642 that takes a @code{float} parameter, @code{name(float)}. To use the
1643 word-completion facilities in this situation, type a single quote
1644 @code{'} at the beginning of the function name. This alerts
1645 @value{GDBN} that it may need to consider more information than usual
1646 when you press @key{TAB} or @kbd{M-?} to request word completion:
1649 (@value{GDBP}) b 'bubble( @kbd{M-?}
1650 bubble(double,double) bubble(int,int)
1651 (@value{GDBP}) b 'bubble(
1654 In some cases, @value{GDBN} can tell that completing a name requires using
1655 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1656 completing as much as it can) if you do not type the quote in the first
1660 (@value{GDBP}) b bub @key{TAB}
1661 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1662 (@value{GDBP}) b 'bubble(
1666 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1667 you have not yet started typing the argument list when you ask for
1668 completion on an overloaded symbol.
1670 For more information about overloaded functions, see @ref{C Plus Plus
1671 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1672 overload-resolution off} to disable overload resolution;
1673 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1675 @cindex completion of structure field names
1676 @cindex structure field name completion
1677 @cindex completion of union field names
1678 @cindex union field name completion
1679 When completing in an expression which looks up a field in a
1680 structure, @value{GDBN} also tries@footnote{The completer can be
1681 confused by certain kinds of invalid expressions. Also, it only
1682 examines the static type of the expression, not the dynamic type.} to
1683 limit completions to the field names available in the type of the
1687 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1688 magic to_fputs to_rewind
1689 to_data to_isatty to_write
1690 to_delete to_put to_write_async_safe
1695 This is because the @code{gdb_stdout} is a variable of the type
1696 @code{struct ui_file} that is defined in @value{GDBN} sources as
1703 ui_file_flush_ftype *to_flush;
1704 ui_file_write_ftype *to_write;
1705 ui_file_write_async_safe_ftype *to_write_async_safe;
1706 ui_file_fputs_ftype *to_fputs;
1707 ui_file_read_ftype *to_read;
1708 ui_file_delete_ftype *to_delete;
1709 ui_file_isatty_ftype *to_isatty;
1710 ui_file_rewind_ftype *to_rewind;
1711 ui_file_put_ftype *to_put;
1718 @section Getting Help
1719 @cindex online documentation
1722 You can always ask @value{GDBN} itself for information on its commands,
1723 using the command @code{help}.
1726 @kindex h @r{(@code{help})}
1729 You can use @code{help} (abbreviated @code{h}) with no arguments to
1730 display a short list of named classes of commands:
1734 List of classes of commands:
1736 aliases -- Aliases of other commands
1737 breakpoints -- Making program stop at certain points
1738 data -- Examining data
1739 files -- Specifying and examining files
1740 internals -- Maintenance commands
1741 obscure -- Obscure features
1742 running -- Running the program
1743 stack -- Examining the stack
1744 status -- Status inquiries
1745 support -- Support facilities
1746 tracepoints -- Tracing of program execution without
1747 stopping the program
1748 user-defined -- User-defined commands
1750 Type "help" followed by a class name for a list of
1751 commands in that class.
1752 Type "help" followed by command name for full
1754 Command name abbreviations are allowed if unambiguous.
1757 @c the above line break eliminates huge line overfull...
1759 @item help @var{class}
1760 Using one of the general help classes as an argument, you can get a
1761 list of the individual commands in that class. For example, here is the
1762 help display for the class @code{status}:
1765 (@value{GDBP}) help status
1770 @c Line break in "show" line falsifies real output, but needed
1771 @c to fit in smallbook page size.
1772 info -- Generic command for showing things
1773 about the program being debugged
1774 show -- Generic command for showing things
1777 Type "help" followed by command name for full
1779 Command name abbreviations are allowed if unambiguous.
1783 @item help @var{command}
1784 With a command name as @code{help} argument, @value{GDBN} displays a
1785 short paragraph on how to use that command.
1788 @item apropos @var{args}
1789 The @code{apropos} command searches through all of the @value{GDBN}
1790 commands, and their documentation, for the regular expression specified in
1791 @var{args}. It prints out all matches found. For example:
1802 alias -- Define a new command that is an alias of an existing command
1803 aliases -- Aliases of other commands
1804 d -- Delete some breakpoints or auto-display expressions
1805 del -- Delete some breakpoints or auto-display expressions
1806 delete -- Delete some breakpoints or auto-display expressions
1811 @item complete @var{args}
1812 The @code{complete @var{args}} command lists all the possible completions
1813 for the beginning of a command. Use @var{args} to specify the beginning of the
1814 command you want completed. For example:
1820 @noindent results in:
1831 @noindent This is intended for use by @sc{gnu} Emacs.
1834 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1835 and @code{show} to inquire about the state of your program, or the state
1836 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1837 manual introduces each of them in the appropriate context. The listings
1838 under @code{info} and under @code{show} in the Command, Variable, and
1839 Function Index point to all the sub-commands. @xref{Command and Variable
1845 @kindex i @r{(@code{info})}
1847 This command (abbreviated @code{i}) is for describing the state of your
1848 program. For example, you can show the arguments passed to a function
1849 with @code{info args}, list the registers currently in use with @code{info
1850 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1851 You can get a complete list of the @code{info} sub-commands with
1852 @w{@code{help info}}.
1856 You can assign the result of an expression to an environment variable with
1857 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1858 @code{set prompt $}.
1862 In contrast to @code{info}, @code{show} is for describing the state of
1863 @value{GDBN} itself.
1864 You can change most of the things you can @code{show}, by using the
1865 related command @code{set}; for example, you can control what number
1866 system is used for displays with @code{set radix}, or simply inquire
1867 which is currently in use with @code{show radix}.
1870 To display all the settable parameters and their current
1871 values, you can use @code{show} with no arguments; you may also use
1872 @code{info set}. Both commands produce the same display.
1873 @c FIXME: "info set" violates the rule that "info" is for state of
1874 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1875 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1879 Here are several miscellaneous @code{show} subcommands, all of which are
1880 exceptional in lacking corresponding @code{set} commands:
1883 @kindex show version
1884 @cindex @value{GDBN} version number
1886 Show what version of @value{GDBN} is running. You should include this
1887 information in @value{GDBN} bug-reports. If multiple versions of
1888 @value{GDBN} are in use at your site, you may need to determine which
1889 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1890 commands are introduced, and old ones may wither away. Also, many
1891 system vendors ship variant versions of @value{GDBN}, and there are
1892 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1893 The version number is the same as the one announced when you start
1896 @kindex show copying
1897 @kindex info copying
1898 @cindex display @value{GDBN} copyright
1901 Display information about permission for copying @value{GDBN}.
1903 @kindex show warranty
1904 @kindex info warranty
1906 @itemx info warranty
1907 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1908 if your version of @value{GDBN} comes with one.
1910 @kindex show configuration
1911 @item show configuration
1912 Display detailed information about the way @value{GDBN} was configured
1913 when it was built. This displays the optional arguments passed to the
1914 @file{configure} script and also configuration parameters detected
1915 automatically by @command{configure}. When reporting a @value{GDBN}
1916 bug (@pxref{GDB Bugs}), it is important to include this information in
1922 @chapter Running Programs Under @value{GDBN}
1924 When you run a program under @value{GDBN}, you must first generate
1925 debugging information when you compile it.
1927 You may start @value{GDBN} with its arguments, if any, in an environment
1928 of your choice. If you are doing native debugging, you may redirect
1929 your program's input and output, debug an already running process, or
1930 kill a child process.
1933 * Compilation:: Compiling for debugging
1934 * Starting:: Starting your program
1935 * Arguments:: Your program's arguments
1936 * Environment:: Your program's environment
1938 * Working Directory:: Your program's working directory
1939 * Input/Output:: Your program's input and output
1940 * Attach:: Debugging an already-running process
1941 * Kill Process:: Killing the child process
1943 * Inferiors and Programs:: Debugging multiple inferiors and programs
1944 * Threads:: Debugging programs with multiple threads
1945 * Forks:: Debugging forks
1946 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1950 @section Compiling for Debugging
1952 In order to debug a program effectively, you need to generate
1953 debugging information when you compile it. This debugging information
1954 is stored in the object file; it describes the data type of each
1955 variable or function and the correspondence between source line numbers
1956 and addresses in the executable code.
1958 To request debugging information, specify the @samp{-g} option when you run
1961 Programs that are to be shipped to your customers are compiled with
1962 optimizations, using the @samp{-O} compiler option. However, some
1963 compilers are unable to handle the @samp{-g} and @samp{-O} options
1964 together. Using those compilers, you cannot generate optimized
1965 executables containing debugging information.
1967 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1968 without @samp{-O}, making it possible to debug optimized code. We
1969 recommend that you @emph{always} use @samp{-g} whenever you compile a
1970 program. You may think your program is correct, but there is no sense
1971 in pushing your luck. For more information, see @ref{Optimized Code}.
1973 Older versions of the @sc{gnu} C compiler permitted a variant option
1974 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1975 format; if your @sc{gnu} C compiler has this option, do not use it.
1977 @value{GDBN} knows about preprocessor macros and can show you their
1978 expansion (@pxref{Macros}). Most compilers do not include information
1979 about preprocessor macros in the debugging information if you specify
1980 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
1981 the @sc{gnu} C compiler, provides macro information if you are using
1982 the DWARF debugging format, and specify the option @option{-g3}.
1984 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1985 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1986 information on @value{NGCC} options affecting debug information.
1988 You will have the best debugging experience if you use the latest
1989 version of the DWARF debugging format that your compiler supports.
1990 DWARF is currently the most expressive and best supported debugging
1991 format in @value{GDBN}.
1995 @section Starting your Program
2001 @kindex r @r{(@code{run})}
2004 Use the @code{run} command to start your program under @value{GDBN}.
2005 You must first specify the program name with an argument to
2006 @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
2007 @value{GDBN}}), or by using the @code{file} or @code{exec-file}
2008 command (@pxref{Files, ,Commands to Specify Files}).
2012 If you are running your program in an execution environment that
2013 supports processes, @code{run} creates an inferior process and makes
2014 that process run your program. In some environments without processes,
2015 @code{run} jumps to the start of your program. Other targets,
2016 like @samp{remote}, are always running. If you get an error
2017 message like this one:
2020 The "remote" target does not support "run".
2021 Try "help target" or "continue".
2025 then use @code{continue} to run your program. You may need @code{load}
2026 first (@pxref{load}).
2028 The execution of a program is affected by certain information it
2029 receives from its superior. @value{GDBN} provides ways to specify this
2030 information, which you must do @emph{before} starting your program. (You
2031 can change it after starting your program, but such changes only affect
2032 your program the next time you start it.) This information may be
2033 divided into four categories:
2036 @item The @emph{arguments.}
2037 Specify the arguments to give your program as the arguments of the
2038 @code{run} command. If a shell is available on your target, the shell
2039 is used to pass the arguments, so that you may use normal conventions
2040 (such as wildcard expansion or variable substitution) in describing
2042 In Unix systems, you can control which shell is used with the
2043 @code{SHELL} environment variable. If you do not define @code{SHELL},
2044 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2045 use of any shell with the @code{set startup-with-shell} command (see
2048 @item The @emph{environment.}
2049 Your program normally inherits its environment from @value{GDBN}, but you can
2050 use the @value{GDBN} commands @code{set environment} and @code{unset
2051 environment} to change parts of the environment that affect
2052 your program. @xref{Environment, ,Your Program's Environment}.
2054 @item The @emph{working directory.}
2055 Your program inherits its working directory from @value{GDBN}. You can set
2056 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
2057 @xref{Working Directory, ,Your Program's Working Directory}.
2059 @item The @emph{standard input and output.}
2060 Your program normally uses the same device for standard input and
2061 standard output as @value{GDBN} is using. You can redirect input and output
2062 in the @code{run} command line, or you can use the @code{tty} command to
2063 set a different device for your program.
2064 @xref{Input/Output, ,Your Program's Input and Output}.
2067 @emph{Warning:} While input and output redirection work, you cannot use
2068 pipes to pass the output of the program you are debugging to another
2069 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2073 When you issue the @code{run} command, your program begins to execute
2074 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2075 of how to arrange for your program to stop. Once your program has
2076 stopped, you may call functions in your program, using the @code{print}
2077 or @code{call} commands. @xref{Data, ,Examining Data}.
2079 If the modification time of your symbol file has changed since the last
2080 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2081 table, and reads it again. When it does this, @value{GDBN} tries to retain
2082 your current breakpoints.
2087 @cindex run to main procedure
2088 The name of the main procedure can vary from language to language.
2089 With C or C@t{++}, the main procedure name is always @code{main}, but
2090 other languages such as Ada do not require a specific name for their
2091 main procedure. The debugger provides a convenient way to start the
2092 execution of the program and to stop at the beginning of the main
2093 procedure, depending on the language used.
2095 The @samp{start} command does the equivalent of setting a temporary
2096 breakpoint at the beginning of the main procedure and then invoking
2097 the @samp{run} command.
2099 @cindex elaboration phase
2100 Some programs contain an @dfn{elaboration} phase where some startup code is
2101 executed before the main procedure is called. This depends on the
2102 languages used to write your program. In C@t{++}, for instance,
2103 constructors for static and global objects are executed before
2104 @code{main} is called. It is therefore possible that the debugger stops
2105 before reaching the main procedure. However, the temporary breakpoint
2106 will remain to halt execution.
2108 Specify the arguments to give to your program as arguments to the
2109 @samp{start} command. These arguments will be given verbatim to the
2110 underlying @samp{run} command. Note that the same arguments will be
2111 reused if no argument is provided during subsequent calls to
2112 @samp{start} or @samp{run}.
2114 It is sometimes necessary to debug the program during elaboration. In
2115 these cases, using the @code{start} command would stop the execution of
2116 your program too late, as the program would have already completed the
2117 elaboration phase. Under these circumstances, insert breakpoints in your
2118 elaboration code before running your program.
2120 @anchor{set exec-wrapper}
2121 @kindex set exec-wrapper
2122 @item set exec-wrapper @var{wrapper}
2123 @itemx show exec-wrapper
2124 @itemx unset exec-wrapper
2125 When @samp{exec-wrapper} is set, the specified wrapper is used to
2126 launch programs for debugging. @value{GDBN} starts your program
2127 with a shell command of the form @kbd{exec @var{wrapper}
2128 @var{program}}. Quoting is added to @var{program} and its
2129 arguments, but not to @var{wrapper}, so you should add quotes if
2130 appropriate for your shell. The wrapper runs until it executes
2131 your program, and then @value{GDBN} takes control.
2133 You can use any program that eventually calls @code{execve} with
2134 its arguments as a wrapper. Several standard Unix utilities do
2135 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2136 with @code{exec "$@@"} will also work.
2138 For example, you can use @code{env} to pass an environment variable to
2139 the debugged program, without setting the variable in your shell's
2143 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2147 This command is available when debugging locally on most targets, excluding
2148 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2150 @kindex set startup-with-shell
2151 @item set startup-with-shell
2152 @itemx set startup-with-shell on
2153 @itemx set startup-with-shell off
2154 @itemx show set startup-with-shell
2155 On Unix systems, by default, if a shell is available on your target,
2156 @value{GDBN}) uses it to start your program. Arguments of the
2157 @code{run} command are passed to the shell, which does variable
2158 substitution, expands wildcard characters and performs redirection of
2159 I/O. In some circumstances, it may be useful to disable such use of a
2160 shell, for example, when debugging the shell itself or diagnosing
2161 startup failures such as:
2165 Starting program: ./a.out
2166 During startup program terminated with signal SIGSEGV, Segmentation fault.
2170 which indicates the shell or the wrapper specified with
2171 @samp{exec-wrapper} crashed, not your program. Most often, this is
2172 caused by something odd in your shell's non-interactive mode
2173 initialization file---such as @file{.cshrc} for C-shell,
2174 $@file{.zshenv} for the Z shell, or the file specified in the
2175 @samp{BASH_ENV} environment variable for BASH.
2177 @anchor{set auto-connect-native-target}
2178 @kindex set auto-connect-native-target
2179 @item set auto-connect-native-target
2180 @itemx set auto-connect-native-target on
2181 @itemx set auto-connect-native-target off
2182 @itemx show auto-connect-native-target
2184 By default, if not connected to any target yet (e.g., with
2185 @code{target remote}), the @code{run} command starts your program as a
2186 native process under @value{GDBN}, on your local machine. If you're
2187 sure you don't want to debug programs on your local machine, you can
2188 tell @value{GDBN} to not connect to the native target automatically
2189 with the @code{set auto-connect-native-target off} command.
2191 If @code{on}, which is the default, and if @value{GDBN} is not
2192 connected to a target already, the @code{run} command automaticaly
2193 connects to the native target, if one is available.
2195 If @code{off}, and if @value{GDBN} is not connected to a target
2196 already, the @code{run} command fails with an error:
2200 Don't know how to run. Try "help target".
2203 If @value{GDBN} is already connected to a target, @value{GDBN} always
2204 uses it with the @code{run} command.
2206 In any case, you can explicitly connect to the native target with the
2207 @code{target native} command. For example,
2210 (@value{GDBP}) set auto-connect-native-target off
2212 Don't know how to run. Try "help target".
2213 (@value{GDBP}) target native
2215 Starting program: ./a.out
2216 [Inferior 1 (process 10421) exited normally]
2219 In case you connected explicitly to the @code{native} target,
2220 @value{GDBN} remains connected even if all inferiors exit, ready for
2221 the next @code{run} command. Use the @code{disconnect} command to
2224 Examples of other commands that likewise respect the
2225 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2226 proc}, @code{info os}.
2228 @kindex set disable-randomization
2229 @item set disable-randomization
2230 @itemx set disable-randomization on
2231 This option (enabled by default in @value{GDBN}) will turn off the native
2232 randomization of the virtual address space of the started program. This option
2233 is useful for multiple debugging sessions to make the execution better
2234 reproducible and memory addresses reusable across debugging sessions.
2236 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2237 On @sc{gnu}/Linux you can get the same behavior using
2240 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2243 @item set disable-randomization off
2244 Leave the behavior of the started executable unchanged. Some bugs rear their
2245 ugly heads only when the program is loaded at certain addresses. If your bug
2246 disappears when you run the program under @value{GDBN}, that might be because
2247 @value{GDBN} by default disables the address randomization on platforms, such
2248 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2249 disable-randomization off} to try to reproduce such elusive bugs.
2251 On targets where it is available, virtual address space randomization
2252 protects the programs against certain kinds of security attacks. In these
2253 cases the attacker needs to know the exact location of a concrete executable
2254 code. Randomizing its location makes it impossible to inject jumps misusing
2255 a code at its expected addresses.
2257 Prelinking shared libraries provides a startup performance advantage but it
2258 makes addresses in these libraries predictable for privileged processes by
2259 having just unprivileged access at the target system. Reading the shared
2260 library binary gives enough information for assembling the malicious code
2261 misusing it. Still even a prelinked shared library can get loaded at a new
2262 random address just requiring the regular relocation process during the
2263 startup. Shared libraries not already prelinked are always loaded at
2264 a randomly chosen address.
2266 Position independent executables (PIE) contain position independent code
2267 similar to the shared libraries and therefore such executables get loaded at
2268 a randomly chosen address upon startup. PIE executables always load even
2269 already prelinked shared libraries at a random address. You can build such
2270 executable using @command{gcc -fPIE -pie}.
2272 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2273 (as long as the randomization is enabled).
2275 @item show disable-randomization
2276 Show the current setting of the explicit disable of the native randomization of
2277 the virtual address space of the started program.
2282 @section Your Program's Arguments
2284 @cindex arguments (to your program)
2285 The arguments to your program can be specified by the arguments of the
2287 They are passed to a shell, which expands wildcard characters and
2288 performs redirection of I/O, and thence to your program. Your
2289 @code{SHELL} environment variable (if it exists) specifies what shell
2290 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2291 the default shell (@file{/bin/sh} on Unix).
2293 On non-Unix systems, the program is usually invoked directly by
2294 @value{GDBN}, which emulates I/O redirection via the appropriate system
2295 calls, and the wildcard characters are expanded by the startup code of
2296 the program, not by the shell.
2298 @code{run} with no arguments uses the same arguments used by the previous
2299 @code{run}, or those set by the @code{set args} command.
2304 Specify the arguments to be used the next time your program is run. If
2305 @code{set args} has no arguments, @code{run} executes your program
2306 with no arguments. Once you have run your program with arguments,
2307 using @code{set args} before the next @code{run} is the only way to run
2308 it again without arguments.
2312 Show the arguments to give your program when it is started.
2316 @section Your Program's Environment
2318 @cindex environment (of your program)
2319 The @dfn{environment} consists of a set of environment variables and
2320 their values. Environment variables conventionally record such things as
2321 your user name, your home directory, your terminal type, and your search
2322 path for programs to run. Usually you set up environment variables with
2323 the shell and they are inherited by all the other programs you run. When
2324 debugging, it can be useful to try running your program with a modified
2325 environment without having to start @value{GDBN} over again.
2329 @item path @var{directory}
2330 Add @var{directory} to the front of the @code{PATH} environment variable
2331 (the search path for executables) that will be passed to your program.
2332 The value of @code{PATH} used by @value{GDBN} does not change.
2333 You may specify several directory names, separated by whitespace or by a
2334 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2335 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2336 is moved to the front, so it is searched sooner.
2338 You can use the string @samp{$cwd} to refer to whatever is the current
2339 working directory at the time @value{GDBN} searches the path. If you
2340 use @samp{.} instead, it refers to the directory where you executed the
2341 @code{path} command. @value{GDBN} replaces @samp{.} in the
2342 @var{directory} argument (with the current path) before adding
2343 @var{directory} to the search path.
2344 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2345 @c document that, since repeating it would be a no-op.
2349 Display the list of search paths for executables (the @code{PATH}
2350 environment variable).
2352 @kindex show environment
2353 @item show environment @r{[}@var{varname}@r{]}
2354 Print the value of environment variable @var{varname} to be given to
2355 your program when it starts. If you do not supply @var{varname},
2356 print the names and values of all environment variables to be given to
2357 your program. You can abbreviate @code{environment} as @code{env}.
2359 @kindex set environment
2360 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2361 Set environment variable @var{varname} to @var{value}. The value
2362 changes for your program (and the shell @value{GDBN} uses to launch
2363 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2364 values of environment variables are just strings, and any
2365 interpretation is supplied by your program itself. The @var{value}
2366 parameter is optional; if it is eliminated, the variable is set to a
2368 @c "any string" here does not include leading, trailing
2369 @c blanks. Gnu asks: does anyone care?
2371 For example, this command:
2378 tells the debugged program, when subsequently run, that its user is named
2379 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2380 are not actually required.)
2382 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2383 which also inherits the environment set with @code{set environment}.
2384 If necessary, you can avoid that by using the @samp{env} program as a
2385 wrapper instead of using @code{set environment}. @xref{set
2386 exec-wrapper}, for an example doing just that.
2388 @kindex unset environment
2389 @item unset environment @var{varname}
2390 Remove variable @var{varname} from the environment to be passed to your
2391 program. This is different from @samp{set env @var{varname} =};
2392 @code{unset environment} removes the variable from the environment,
2393 rather than assigning it an empty value.
2396 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2397 the shell indicated by your @code{SHELL} environment variable if it
2398 exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
2399 names a shell that runs an initialization file when started
2400 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2401 for the Z shell, or the file specified in the @samp{BASH_ENV}
2402 environment variable for BASH---any variables you set in that file
2403 affect your program. You may wish to move setting of environment
2404 variables to files that are only run when you sign on, such as
2405 @file{.login} or @file{.profile}.
2407 @node Working Directory
2408 @section Your Program's Working Directory
2410 @cindex working directory (of your program)
2411 Each time you start your program with @code{run}, it inherits its
2412 working directory from the current working directory of @value{GDBN}.
2413 The @value{GDBN} working directory is initially whatever it inherited
2414 from its parent process (typically the shell), but you can specify a new
2415 working directory in @value{GDBN} with the @code{cd} command.
2417 The @value{GDBN} working directory also serves as a default for the commands
2418 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2423 @cindex change working directory
2424 @item cd @r{[}@var{directory}@r{]}
2425 Set the @value{GDBN} working directory to @var{directory}. If not
2426 given, @var{directory} uses @file{'~'}.
2430 Print the @value{GDBN} working directory.
2433 It is generally impossible to find the current working directory of
2434 the process being debugged (since a program can change its directory
2435 during its run). If you work on a system where @value{GDBN} is
2436 configured with the @file{/proc} support, you can use the @code{info
2437 proc} command (@pxref{SVR4 Process Information}) to find out the
2438 current working directory of the debuggee.
2441 @section Your Program's Input and Output
2446 By default, the program you run under @value{GDBN} does input and output to
2447 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2448 to its own terminal modes to interact with you, but it records the terminal
2449 modes your program was using and switches back to them when you continue
2450 running your program.
2453 @kindex info terminal
2455 Displays information recorded by @value{GDBN} about the terminal modes your
2459 You can redirect your program's input and/or output using shell
2460 redirection with the @code{run} command. For example,
2467 starts your program, diverting its output to the file @file{outfile}.
2470 @cindex controlling terminal
2471 Another way to specify where your program should do input and output is
2472 with the @code{tty} command. This command accepts a file name as
2473 argument, and causes this file to be the default for future @code{run}
2474 commands. It also resets the controlling terminal for the child
2475 process, for future @code{run} commands. For example,
2482 directs that processes started with subsequent @code{run} commands
2483 default to do input and output on the terminal @file{/dev/ttyb} and have
2484 that as their controlling terminal.
2486 An explicit redirection in @code{run} overrides the @code{tty} command's
2487 effect on the input/output device, but not its effect on the controlling
2490 When you use the @code{tty} command or redirect input in the @code{run}
2491 command, only the input @emph{for your program} is affected. The input
2492 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2493 for @code{set inferior-tty}.
2495 @cindex inferior tty
2496 @cindex set inferior controlling terminal
2497 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2498 display the name of the terminal that will be used for future runs of your
2502 @item set inferior-tty /dev/ttyb
2503 @kindex set inferior-tty
2504 Set the tty for the program being debugged to /dev/ttyb.
2506 @item show inferior-tty
2507 @kindex show inferior-tty
2508 Show the current tty for the program being debugged.
2512 @section Debugging an Already-running Process
2517 @item attach @var{process-id}
2518 This command attaches to a running process---one that was started
2519 outside @value{GDBN}. (@code{info files} shows your active
2520 targets.) The command takes as argument a process ID. The usual way to
2521 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2522 or with the @samp{jobs -l} shell command.
2524 @code{attach} does not repeat if you press @key{RET} a second time after
2525 executing the command.
2528 To use @code{attach}, your program must be running in an environment
2529 which supports processes; for example, @code{attach} does not work for
2530 programs on bare-board targets that lack an operating system. You must
2531 also have permission to send the process a signal.
2533 When you use @code{attach}, the debugger finds the program running in
2534 the process first by looking in the current working directory, then (if
2535 the program is not found) by using the source file search path
2536 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2537 the @code{file} command to load the program. @xref{Files, ,Commands to
2540 The first thing @value{GDBN} does after arranging to debug the specified
2541 process is to stop it. You can examine and modify an attached process
2542 with all the @value{GDBN} commands that are ordinarily available when
2543 you start processes with @code{run}. You can insert breakpoints; you
2544 can step and continue; you can modify storage. If you would rather the
2545 process continue running, you may use the @code{continue} command after
2546 attaching @value{GDBN} to the process.
2551 When you have finished debugging the attached process, you can use the
2552 @code{detach} command to release it from @value{GDBN} control. Detaching
2553 the process continues its execution. After the @code{detach} command,
2554 that process and @value{GDBN} become completely independent once more, and you
2555 are ready to @code{attach} another process or start one with @code{run}.
2556 @code{detach} does not repeat if you press @key{RET} again after
2557 executing the command.
2560 If you exit @value{GDBN} while you have an attached process, you detach
2561 that process. If you use the @code{run} command, you kill that process.
2562 By default, @value{GDBN} asks for confirmation if you try to do either of these
2563 things; you can control whether or not you need to confirm by using the
2564 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2568 @section Killing the Child Process
2573 Kill the child process in which your program is running under @value{GDBN}.
2576 This command is useful if you wish to debug a core dump instead of a
2577 running process. @value{GDBN} ignores any core dump file while your program
2580 On some operating systems, a program cannot be executed outside @value{GDBN}
2581 while you have breakpoints set on it inside @value{GDBN}. You can use the
2582 @code{kill} command in this situation to permit running your program
2583 outside the debugger.
2585 The @code{kill} command is also useful if you wish to recompile and
2586 relink your program, since on many systems it is impossible to modify an
2587 executable file while it is running in a process. In this case, when you
2588 next type @code{run}, @value{GDBN} notices that the file has changed, and
2589 reads the symbol table again (while trying to preserve your current
2590 breakpoint settings).
2592 @node Inferiors and Programs
2593 @section Debugging Multiple Inferiors and Programs
2595 @value{GDBN} lets you run and debug multiple programs in a single
2596 session. In addition, @value{GDBN} on some systems may let you run
2597 several programs simultaneously (otherwise you have to exit from one
2598 before starting another). In the most general case, you can have
2599 multiple threads of execution in each of multiple processes, launched
2600 from multiple executables.
2603 @value{GDBN} represents the state of each program execution with an
2604 object called an @dfn{inferior}. An inferior typically corresponds to
2605 a process, but is more general and applies also to targets that do not
2606 have processes. Inferiors may be created before a process runs, and
2607 may be retained after a process exits. Inferiors have unique
2608 identifiers that are different from process ids. Usually each
2609 inferior will also have its own distinct address space, although some
2610 embedded targets may have several inferiors running in different parts
2611 of a single address space. Each inferior may in turn have multiple
2612 threads running in it.
2614 To find out what inferiors exist at any moment, use @w{@code{info
2618 @kindex info inferiors
2619 @item info inferiors
2620 Print a list of all inferiors currently being managed by @value{GDBN}.
2622 @value{GDBN} displays for each inferior (in this order):
2626 the inferior number assigned by @value{GDBN}
2629 the target system's inferior identifier
2632 the name of the executable the inferior is running.
2637 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2638 indicates the current inferior.
2642 @c end table here to get a little more width for example
2645 (@value{GDBP}) info inferiors
2646 Num Description Executable
2647 2 process 2307 hello
2648 * 1 process 3401 goodbye
2651 To switch focus between inferiors, use the @code{inferior} command:
2654 @kindex inferior @var{infno}
2655 @item inferior @var{infno}
2656 Make inferior number @var{infno} the current inferior. The argument
2657 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2658 in the first field of the @samp{info inferiors} display.
2661 @vindex $_inferior@r{, convenience variable}
2662 The debugger convenience variable @samp{$_inferior} contains the
2663 number of the current inferior. You may find this useful in writing
2664 breakpoint conditional expressions, command scripts, and so forth.
2665 @xref{Convenience Vars,, Convenience Variables}, for general
2666 information on convenience variables.
2668 You can get multiple executables into a debugging session via the
2669 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2670 systems @value{GDBN} can add inferiors to the debug session
2671 automatically by following calls to @code{fork} and @code{exec}. To
2672 remove inferiors from the debugging session use the
2673 @w{@code{remove-inferiors}} command.
2676 @kindex add-inferior
2677 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2678 Adds @var{n} inferiors to be run using @var{executable} as the
2679 executable; @var{n} defaults to 1. If no executable is specified,
2680 the inferiors begins empty, with no program. You can still assign or
2681 change the program assigned to the inferior at any time by using the
2682 @code{file} command with the executable name as its argument.
2684 @kindex clone-inferior
2685 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2686 Adds @var{n} inferiors ready to execute the same program as inferior
2687 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
2688 number of the current inferior. This is a convenient command when you
2689 want to run another instance of the inferior you are debugging.
2692 (@value{GDBP}) info inferiors
2693 Num Description Executable
2694 * 1 process 29964 helloworld
2695 (@value{GDBP}) clone-inferior
2698 (@value{GDBP}) info inferiors
2699 Num Description Executable
2701 * 1 process 29964 helloworld
2704 You can now simply switch focus to inferior 2 and run it.
2706 @kindex remove-inferiors
2707 @item remove-inferiors @var{infno}@dots{}
2708 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2709 possible to remove an inferior that is running with this command. For
2710 those, use the @code{kill} or @code{detach} command first.
2714 To quit debugging one of the running inferiors that is not the current
2715 inferior, you can either detach from it by using the @w{@code{detach
2716 inferior}} command (allowing it to run independently), or kill it
2717 using the @w{@code{kill inferiors}} command:
2720 @kindex detach inferiors @var{infno}@dots{}
2721 @item detach inferior @var{infno}@dots{}
2722 Detach from the inferior or inferiors identified by @value{GDBN}
2723 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2724 still stays on the list of inferiors shown by @code{info inferiors},
2725 but its Description will show @samp{<null>}.
2727 @kindex kill inferiors @var{infno}@dots{}
2728 @item kill inferiors @var{infno}@dots{}
2729 Kill the inferior or inferiors identified by @value{GDBN} inferior
2730 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2731 stays on the list of inferiors shown by @code{info inferiors}, but its
2732 Description will show @samp{<null>}.
2735 After the successful completion of a command such as @code{detach},
2736 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2737 a normal process exit, the inferior is still valid and listed with
2738 @code{info inferiors}, ready to be restarted.
2741 To be notified when inferiors are started or exit under @value{GDBN}'s
2742 control use @w{@code{set print inferior-events}}:
2745 @kindex set print inferior-events
2746 @cindex print messages on inferior start and exit
2747 @item set print inferior-events
2748 @itemx set print inferior-events on
2749 @itemx set print inferior-events off
2750 The @code{set print inferior-events} command allows you to enable or
2751 disable printing of messages when @value{GDBN} notices that new
2752 inferiors have started or that inferiors have exited or have been
2753 detached. By default, these messages will not be printed.
2755 @kindex show print inferior-events
2756 @item show print inferior-events
2757 Show whether messages will be printed when @value{GDBN} detects that
2758 inferiors have started, exited or have been detached.
2761 Many commands will work the same with multiple programs as with a
2762 single program: e.g., @code{print myglobal} will simply display the
2763 value of @code{myglobal} in the current inferior.
2766 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2767 get more info about the relationship of inferiors, programs, address
2768 spaces in a debug session. You can do that with the @w{@code{maint
2769 info program-spaces}} command.
2772 @kindex maint info program-spaces
2773 @item maint info program-spaces
2774 Print a list of all program spaces currently being managed by
2777 @value{GDBN} displays for each program space (in this order):
2781 the program space number assigned by @value{GDBN}
2784 the name of the executable loaded into the program space, with e.g.,
2785 the @code{file} command.
2790 An asterisk @samp{*} preceding the @value{GDBN} program space number
2791 indicates the current program space.
2793 In addition, below each program space line, @value{GDBN} prints extra
2794 information that isn't suitable to display in tabular form. For
2795 example, the list of inferiors bound to the program space.
2798 (@value{GDBP}) maint info program-spaces
2802 Bound inferiors: ID 1 (process 21561)
2805 Here we can see that no inferior is running the program @code{hello},
2806 while @code{process 21561} is running the program @code{goodbye}. On
2807 some targets, it is possible that multiple inferiors are bound to the
2808 same program space. The most common example is that of debugging both
2809 the parent and child processes of a @code{vfork} call. For example,
2812 (@value{GDBP}) maint info program-spaces
2815 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2818 Here, both inferior 2 and inferior 1 are running in the same program
2819 space as a result of inferior 1 having executed a @code{vfork} call.
2823 @section Debugging Programs with Multiple Threads
2825 @cindex threads of execution
2826 @cindex multiple threads
2827 @cindex switching threads
2828 In some operating systems, such as GNU/Linux and Solaris, a single program
2829 may have more than one @dfn{thread} of execution. The precise semantics
2830 of threads differ from one operating system to another, but in general
2831 the threads of a single program are akin to multiple processes---except
2832 that they share one address space (that is, they can all examine and
2833 modify the same variables). On the other hand, each thread has its own
2834 registers and execution stack, and perhaps private memory.
2836 @value{GDBN} provides these facilities for debugging multi-thread
2840 @item automatic notification of new threads
2841 @item @samp{thread @var{thread-id}}, a command to switch among threads
2842 @item @samp{info threads}, a command to inquire about existing threads
2843 @item @samp{thread apply [@var{thread-id-list}] [@var{all}] @var{args}},
2844 a command to apply a command to a list of threads
2845 @item thread-specific breakpoints
2846 @item @samp{set print thread-events}, which controls printing of
2847 messages on thread start and exit.
2848 @item @samp{set libthread-db-search-path @var{path}}, which lets
2849 the user specify which @code{libthread_db} to use if the default choice
2850 isn't compatible with the program.
2853 @cindex focus of debugging
2854 @cindex current thread
2855 The @value{GDBN} thread debugging facility allows you to observe all
2856 threads while your program runs---but whenever @value{GDBN} takes
2857 control, one thread in particular is always the focus of debugging.
2858 This thread is called the @dfn{current thread}. Debugging commands show
2859 program information from the perspective of the current thread.
2861 @cindex @code{New} @var{systag} message
2862 @cindex thread identifier (system)
2863 @c FIXME-implementors!! It would be more helpful if the [New...] message
2864 @c included GDB's numeric thread handle, so you could just go to that
2865 @c thread without first checking `info threads'.
2866 Whenever @value{GDBN} detects a new thread in your program, it displays
2867 the target system's identification for the thread with a message in the
2868 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
2869 whose form varies depending on the particular system. For example, on
2870 @sc{gnu}/Linux, you might see
2873 [New Thread 0x41e02940 (LWP 25582)]
2877 when @value{GDBN} notices a new thread. In contrast, on other systems,
2878 the @var{systag} is simply something like @samp{process 368}, with no
2881 @c FIXME!! (1) Does the [New...] message appear even for the very first
2882 @c thread of a program, or does it only appear for the
2883 @c second---i.e.@: when it becomes obvious we have a multithread
2885 @c (2) *Is* there necessarily a first thread always? Or do some
2886 @c multithread systems permit starting a program with multiple
2887 @c threads ab initio?
2889 @anchor{thread numbers}
2890 @cindex thread number, per inferior
2891 @cindex thread identifier (GDB)
2892 For debugging purposes, @value{GDBN} associates its own thread number
2893 ---always a single integer---with each thread of an inferior. This
2894 number is unique between all threads of an inferior, but not unique
2895 between threads of different inferiors.
2897 @cindex qualified thread ID
2898 You can refer to a given thread in an inferior using the qualified
2899 @var{inferior-num}.@var{thread-num} syntax, also known as
2900 @dfn{qualified thread ID}, with @var{inferior-num} being the inferior
2901 number and @var{thread-num} being the thread number of the given
2902 inferior. For example, thread @code{2.3} refers to thread number 3 of
2903 inferior 2. If you omit @var{inferior-num} (e.g., @code{thread 3}),
2904 then @value{GDBN} infers you're referring to a thread of the current
2907 Until you create a second inferior, @value{GDBN} does not show the
2908 @var{inferior-num} part of thread IDs, even though you can always use
2909 the full @var{inferior-num}.@var{thread-num} form to refer to threads
2910 of inferior 1, the initial inferior.
2912 @anchor{thread ID lists}
2913 @cindex thread ID lists
2914 Some commands accept a space-separated @dfn{thread ID list} as
2915 argument. A list element can be:
2919 A thread ID as shown in the first field of the @samp{info threads}
2920 display, with or without an inferior qualifier. E.g., @samp{2.1} or
2924 A range of thread numbers, again with or without an inferior
2925 qualifier, as in @var{inf}.@var{thr1}-@var{thr2} or
2926 @var{thr1}-@var{thr2}. E.g., @samp{1.2-4} or @samp{2-4}.
2929 All threads of an inferior, specified with a star wildcard, with or
2930 without an inferior qualifier, as in @var{inf}.@code{*} (e.g.,
2931 @samp{1.*}) or @code{*}. The former refers to all threads of the
2932 given inferior, and the latter form without an inferior qualifier
2933 refers to all threads of the current inferior.
2937 For example, if the current inferior is 1, and inferior 7 has one
2938 thread with ID 7.1, the thread list @samp{1 2-3 4.5 6.7-9 7.*}
2939 includes threads 1 to 3 of inferior 1, thread 5 of inferior 4, threads
2940 7 to 9 of inferior 6 and all threads of inferior 7. That is, in
2941 expanded qualified form, the same as @samp{1.1 1.2 1.3 4.5 6.7 6.8 6.9
2945 @anchor{global thread numbers}
2946 @cindex global thread number
2947 @cindex global thread identifier (GDB)
2948 In addition to a @emph{per-inferior} number, each thread is also
2949 assigned a unique @emph{global} number, also known as @dfn{global
2950 thread ID}, a single integer. Unlike the thread number component of
2951 the thread ID, no two threads have the same global ID, even when
2952 you're debugging multiple inferiors.
2954 From @value{GDBN}'s perspective, a process always has at least one
2955 thread. In other words, @value{GDBN} assigns a thread number to the
2956 program's ``main thread'' even if the program is not multi-threaded.
2958 @vindex $_thread@r{, convenience variable}
2959 @vindex $_gthread@r{, convenience variable}
2960 The debugger convenience variables @samp{$_thread} and
2961 @samp{$_gthread} contain, respectively, the per-inferior thread number
2962 and the global thread number of the current thread. You may find this
2963 useful in writing breakpoint conditional expressions, command scripts,
2964 and so forth. @xref{Convenience Vars,, Convenience Variables}, for
2965 general information on convenience variables.
2967 If @value{GDBN} detects the program is multi-threaded, it augments the
2968 usual message about stopping at a breakpoint with the ID and name of
2969 the thread that hit the breakpoint.
2972 Thread 2 "client" hit Breakpoint 1, send_message () at client.c:68
2975 Likewise when the program receives a signal:
2978 Thread 1 "main" received signal SIGINT, Interrupt.
2982 @kindex info threads
2983 @item info threads @r{[}@var{thread-id-list}@r{]}
2985 Display information about one or more threads. With no arguments
2986 displays information about all threads. You can specify the list of
2987 threads that you want to display using the thread ID list syntax
2988 (@pxref{thread ID lists}).
2990 @value{GDBN} displays for each thread (in this order):
2994 the per-inferior thread number assigned by @value{GDBN}
2997 the global thread number assigned by @value{GDBN}, if the @samp{-gid}
2998 option was specified
3001 the target system's thread identifier (@var{systag})
3004 the thread's name, if one is known. A thread can either be named by
3005 the user (see @code{thread name}, below), or, in some cases, by the
3009 the current stack frame summary for that thread
3013 An asterisk @samp{*} to the left of the @value{GDBN} thread number
3014 indicates the current thread.
3018 @c end table here to get a little more width for example
3021 (@value{GDBP}) info threads
3023 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3024 2 process 35 thread 23 0x34e5 in sigpause ()
3025 3 process 35 thread 27 0x34e5 in sigpause ()
3029 If you're debugging multiple inferiors, @value{GDBN} displays thread
3030 IDs using the qualified @var{inferior-num}.@var{thread-num} format.
3031 Otherwise, only @var{thread-num} is shown.
3033 If you specify the @samp{-gid} option, @value{GDBN} displays a column
3034 indicating each thread's global thread ID:
3037 (@value{GDBP}) info threads
3038 Id GId Target Id Frame
3039 1.1 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3040 1.2 3 process 35 thread 23 0x34e5 in sigpause ()
3041 1.3 4 process 35 thread 27 0x34e5 in sigpause ()
3042 * 2.1 2 process 65 thread 1 main (argc=1, argv=0x7ffffff8)
3045 On Solaris, you can display more information about user threads with a
3046 Solaris-specific command:
3049 @item maint info sol-threads
3050 @kindex maint info sol-threads
3051 @cindex thread info (Solaris)
3052 Display info on Solaris user threads.
3056 @kindex thread @var{thread-id}
3057 @item thread @var{thread-id}
3058 Make thread ID @var{thread-id} the current thread. The command
3059 argument @var{thread-id} is the @value{GDBN} thread ID, as shown in
3060 the first field of the @samp{info threads} display, with or without an
3061 inferior qualifier (e.g., @samp{2.1} or @samp{1}).
3063 @value{GDBN} responds by displaying the system identifier of the
3064 thread you selected, and its current stack frame summary:
3067 (@value{GDBP}) thread 2
3068 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
3069 #0 some_function (ignore=0x0) at example.c:8
3070 8 printf ("hello\n");
3074 As with the @samp{[New @dots{}]} message, the form of the text after
3075 @samp{Switching to} depends on your system's conventions for identifying
3078 @kindex thread apply
3079 @cindex apply command to several threads
3080 @item thread apply [@var{thread-id-list} | all [-ascending]] @var{command}
3081 The @code{thread apply} command allows you to apply the named
3082 @var{command} to one or more threads. Specify the threads that you
3083 want affected using the thread ID list syntax (@pxref{thread ID
3084 lists}), or specify @code{all} to apply to all threads. To apply a
3085 command to all threads in descending order, type @kbd{thread apply all
3086 @var{command}}. To apply a command to all threads in ascending order,
3087 type @kbd{thread apply all -ascending @var{command}}.
3091 @cindex name a thread
3092 @item thread name [@var{name}]
3093 This command assigns a name to the current thread. If no argument is
3094 given, any existing user-specified name is removed. The thread name
3095 appears in the @samp{info threads} display.
3097 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3098 determine the name of the thread as given by the OS. On these
3099 systems, a name specified with @samp{thread name} will override the
3100 system-give name, and removing the user-specified name will cause
3101 @value{GDBN} to once again display the system-specified name.
3104 @cindex search for a thread
3105 @item thread find [@var{regexp}]
3106 Search for and display thread ids whose name or @var{systag}
3107 matches the supplied regular expression.
3109 As well as being the complement to the @samp{thread name} command,
3110 this command also allows you to identify a thread by its target
3111 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3115 (@value{GDBN}) thread find 26688
3116 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3117 (@value{GDBN}) info thread 4
3119 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3122 @kindex set print thread-events
3123 @cindex print messages on thread start and exit
3124 @item set print thread-events
3125 @itemx set print thread-events on
3126 @itemx set print thread-events off
3127 The @code{set print thread-events} command allows you to enable or
3128 disable printing of messages when @value{GDBN} notices that new threads have
3129 started or that threads have exited. By default, these messages will
3130 be printed if detection of these events is supported by the target.
3131 Note that these messages cannot be disabled on all targets.
3133 @kindex show print thread-events
3134 @item show print thread-events
3135 Show whether messages will be printed when @value{GDBN} detects that threads
3136 have started and exited.
3139 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3140 more information about how @value{GDBN} behaves when you stop and start
3141 programs with multiple threads.
3143 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3144 watchpoints in programs with multiple threads.
3146 @anchor{set libthread-db-search-path}
3148 @kindex set libthread-db-search-path
3149 @cindex search path for @code{libthread_db}
3150 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3151 If this variable is set, @var{path} is a colon-separated list of
3152 directories @value{GDBN} will use to search for @code{libthread_db}.
3153 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3154 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3155 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3158 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3159 @code{libthread_db} library to obtain information about threads in the
3160 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3161 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3162 specific thread debugging library loading is enabled
3163 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3165 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3166 refers to the default system directories that are
3167 normally searched for loading shared libraries. The @samp{$sdir} entry
3168 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3169 (@pxref{libthread_db.so.1 file}).
3171 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3172 refers to the directory from which @code{libpthread}
3173 was loaded in the inferior process.
3175 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3176 @value{GDBN} attempts to initialize it with the current inferior process.
3177 If this initialization fails (which could happen because of a version
3178 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3179 will unload @code{libthread_db}, and continue with the next directory.
3180 If none of @code{libthread_db} libraries initialize successfully,
3181 @value{GDBN} will issue a warning and thread debugging will be disabled.
3183 Setting @code{libthread-db-search-path} is currently implemented
3184 only on some platforms.
3186 @kindex show libthread-db-search-path
3187 @item show libthread-db-search-path
3188 Display current libthread_db search path.
3190 @kindex set debug libthread-db
3191 @kindex show debug libthread-db
3192 @cindex debugging @code{libthread_db}
3193 @item set debug libthread-db
3194 @itemx show debug libthread-db
3195 Turns on or off display of @code{libthread_db}-related events.
3196 Use @code{1} to enable, @code{0} to disable.
3200 @section Debugging Forks
3202 @cindex fork, debugging programs which call
3203 @cindex multiple processes
3204 @cindex processes, multiple
3205 On most systems, @value{GDBN} has no special support for debugging
3206 programs which create additional processes using the @code{fork}
3207 function. When a program forks, @value{GDBN} will continue to debug the
3208 parent process and the child process will run unimpeded. If you have
3209 set a breakpoint in any code which the child then executes, the child
3210 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3211 will cause it to terminate.
3213 However, if you want to debug the child process there is a workaround
3214 which isn't too painful. Put a call to @code{sleep} in the code which
3215 the child process executes after the fork. It may be useful to sleep
3216 only if a certain environment variable is set, or a certain file exists,
3217 so that the delay need not occur when you don't want to run @value{GDBN}
3218 on the child. While the child is sleeping, use the @code{ps} program to
3219 get its process ID. Then tell @value{GDBN} (a new invocation of
3220 @value{GDBN} if you are also debugging the parent process) to attach to
3221 the child process (@pxref{Attach}). From that point on you can debug
3222 the child process just like any other process which you attached to.
3224 On some systems, @value{GDBN} provides support for debugging programs
3225 that create additional processes using the @code{fork} or @code{vfork}
3226 functions. On @sc{gnu}/Linux platforms, this feature is supported
3227 with kernel version 2.5.46 and later.
3229 The fork debugging commands are supported in native mode and when
3230 connected to @code{gdbserver} in either @code{target remote} mode or
3231 @code{target extended-remote} mode.
3233 By default, when a program forks, @value{GDBN} will continue to debug
3234 the parent process and the child process will run unimpeded.
3236 If you want to follow the child process instead of the parent process,
3237 use the command @w{@code{set follow-fork-mode}}.
3240 @kindex set follow-fork-mode
3241 @item set follow-fork-mode @var{mode}
3242 Set the debugger response to a program call of @code{fork} or
3243 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3244 process. The @var{mode} argument can be:
3248 The original process is debugged after a fork. The child process runs
3249 unimpeded. This is the default.
3252 The new process is debugged after a fork. The parent process runs
3257 @kindex show follow-fork-mode
3258 @item show follow-fork-mode
3259 Display the current debugger response to a @code{fork} or @code{vfork} call.
3262 @cindex debugging multiple processes
3263 On Linux, if you want to debug both the parent and child processes, use the
3264 command @w{@code{set detach-on-fork}}.
3267 @kindex set detach-on-fork
3268 @item set detach-on-fork @var{mode}
3269 Tells gdb whether to detach one of the processes after a fork, or
3270 retain debugger control over them both.
3274 The child process (or parent process, depending on the value of
3275 @code{follow-fork-mode}) will be detached and allowed to run
3276 independently. This is the default.
3279 Both processes will be held under the control of @value{GDBN}.
3280 One process (child or parent, depending on the value of
3281 @code{follow-fork-mode}) is debugged as usual, while the other
3286 @kindex show detach-on-fork
3287 @item show detach-on-fork
3288 Show whether detach-on-fork mode is on/off.
3291 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3292 will retain control of all forked processes (including nested forks).
3293 You can list the forked processes under the control of @value{GDBN} by
3294 using the @w{@code{info inferiors}} command, and switch from one fork
3295 to another by using the @code{inferior} command (@pxref{Inferiors and
3296 Programs, ,Debugging Multiple Inferiors and Programs}).
3298 To quit debugging one of the forked processes, you can either detach
3299 from it by using the @w{@code{detach inferiors}} command (allowing it
3300 to run independently), or kill it using the @w{@code{kill inferiors}}
3301 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3304 If you ask to debug a child process and a @code{vfork} is followed by an
3305 @code{exec}, @value{GDBN} executes the new target up to the first
3306 breakpoint in the new target. If you have a breakpoint set on
3307 @code{main} in your original program, the breakpoint will also be set on
3308 the child process's @code{main}.
3310 On some systems, when a child process is spawned by @code{vfork}, you
3311 cannot debug the child or parent until an @code{exec} call completes.
3313 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3314 call executes, the new target restarts. To restart the parent
3315 process, use the @code{file} command with the parent executable name
3316 as its argument. By default, after an @code{exec} call executes,
3317 @value{GDBN} discards the symbols of the previous executable image.
3318 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3322 @kindex set follow-exec-mode
3323 @item set follow-exec-mode @var{mode}
3325 Set debugger response to a program call of @code{exec}. An
3326 @code{exec} call replaces the program image of a process.
3328 @code{follow-exec-mode} can be:
3332 @value{GDBN} creates a new inferior and rebinds the process to this
3333 new inferior. The program the process was running before the
3334 @code{exec} call can be restarted afterwards by restarting the
3340 (@value{GDBP}) info inferiors
3342 Id Description Executable
3345 process 12020 is executing new program: prog2
3346 Program exited normally.
3347 (@value{GDBP}) info inferiors
3348 Id Description Executable
3354 @value{GDBN} keeps the process bound to the same inferior. The new
3355 executable image replaces the previous executable loaded in the
3356 inferior. Restarting the inferior after the @code{exec} call, with
3357 e.g., the @code{run} command, restarts the executable the process was
3358 running after the @code{exec} call. This is the default mode.
3363 (@value{GDBP}) info inferiors
3364 Id Description Executable
3367 process 12020 is executing new program: prog2
3368 Program exited normally.
3369 (@value{GDBP}) info inferiors
3370 Id Description Executable
3377 @code{follow-exec-mode} is supported in native mode and
3378 @code{target extended-remote} mode.
3380 You can use the @code{catch} command to make @value{GDBN} stop whenever
3381 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3382 Catchpoints, ,Setting Catchpoints}.
3384 @node Checkpoint/Restart
3385 @section Setting a @emph{Bookmark} to Return to Later
3390 @cindex snapshot of a process
3391 @cindex rewind program state
3393 On certain operating systems@footnote{Currently, only
3394 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3395 program's state, called a @dfn{checkpoint}, and come back to it
3398 Returning to a checkpoint effectively undoes everything that has
3399 happened in the program since the @code{checkpoint} was saved. This
3400 includes changes in memory, registers, and even (within some limits)
3401 system state. Effectively, it is like going back in time to the
3402 moment when the checkpoint was saved.
3404 Thus, if you're stepping thru a program and you think you're
3405 getting close to the point where things go wrong, you can save
3406 a checkpoint. Then, if you accidentally go too far and miss
3407 the critical statement, instead of having to restart your program
3408 from the beginning, you can just go back to the checkpoint and
3409 start again from there.
3411 This can be especially useful if it takes a lot of time or
3412 steps to reach the point where you think the bug occurs.
3414 To use the @code{checkpoint}/@code{restart} method of debugging:
3419 Save a snapshot of the debugged program's current execution state.
3420 The @code{checkpoint} command takes no arguments, but each checkpoint
3421 is assigned a small integer id, similar to a breakpoint id.
3423 @kindex info checkpoints
3424 @item info checkpoints
3425 List the checkpoints that have been saved in the current debugging
3426 session. For each checkpoint, the following information will be
3433 @item Source line, or label
3436 @kindex restart @var{checkpoint-id}
3437 @item restart @var{checkpoint-id}
3438 Restore the program state that was saved as checkpoint number
3439 @var{checkpoint-id}. All program variables, registers, stack frames
3440 etc.@: will be returned to the values that they had when the checkpoint
3441 was saved. In essence, gdb will ``wind back the clock'' to the point
3442 in time when the checkpoint was saved.
3444 Note that breakpoints, @value{GDBN} variables, command history etc.
3445 are not affected by restoring a checkpoint. In general, a checkpoint
3446 only restores things that reside in the program being debugged, not in
3449 @kindex delete checkpoint @var{checkpoint-id}
3450 @item delete checkpoint @var{checkpoint-id}
3451 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3455 Returning to a previously saved checkpoint will restore the user state
3456 of the program being debugged, plus a significant subset of the system
3457 (OS) state, including file pointers. It won't ``un-write'' data from
3458 a file, but it will rewind the file pointer to the previous location,
3459 so that the previously written data can be overwritten. For files
3460 opened in read mode, the pointer will also be restored so that the
3461 previously read data can be read again.
3463 Of course, characters that have been sent to a printer (or other
3464 external device) cannot be ``snatched back'', and characters received
3465 from eg.@: a serial device can be removed from internal program buffers,
3466 but they cannot be ``pushed back'' into the serial pipeline, ready to
3467 be received again. Similarly, the actual contents of files that have
3468 been changed cannot be restored (at this time).
3470 However, within those constraints, you actually can ``rewind'' your
3471 program to a previously saved point in time, and begin debugging it
3472 again --- and you can change the course of events so as to debug a
3473 different execution path this time.
3475 @cindex checkpoints and process id
3476 Finally, there is one bit of internal program state that will be
3477 different when you return to a checkpoint --- the program's process
3478 id. Each checkpoint will have a unique process id (or @var{pid}),
3479 and each will be different from the program's original @var{pid}.
3480 If your program has saved a local copy of its process id, this could
3481 potentially pose a problem.
3483 @subsection A Non-obvious Benefit of Using Checkpoints
3485 On some systems such as @sc{gnu}/Linux, address space randomization
3486 is performed on new processes for security reasons. This makes it
3487 difficult or impossible to set a breakpoint, or watchpoint, on an
3488 absolute address if you have to restart the program, since the
3489 absolute location of a symbol will change from one execution to the
3492 A checkpoint, however, is an @emph{identical} copy of a process.
3493 Therefore if you create a checkpoint at (eg.@:) the start of main,
3494 and simply return to that checkpoint instead of restarting the
3495 process, you can avoid the effects of address randomization and
3496 your symbols will all stay in the same place.
3499 @chapter Stopping and Continuing
3501 The principal purposes of using a debugger are so that you can stop your
3502 program before it terminates; or so that, if your program runs into
3503 trouble, you can investigate and find out why.
3505 Inside @value{GDBN}, your program may stop for any of several reasons,
3506 such as a signal, a breakpoint, or reaching a new line after a
3507 @value{GDBN} command such as @code{step}. You may then examine and
3508 change variables, set new breakpoints or remove old ones, and then
3509 continue execution. Usually, the messages shown by @value{GDBN} provide
3510 ample explanation of the status of your program---but you can also
3511 explicitly request this information at any time.
3514 @kindex info program
3516 Display information about the status of your program: whether it is
3517 running or not, what process it is, and why it stopped.
3521 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3522 * Continuing and Stepping:: Resuming execution
3523 * Skipping Over Functions and Files::
3524 Skipping over functions and files
3526 * Thread Stops:: Stopping and starting multi-thread programs
3530 @section Breakpoints, Watchpoints, and Catchpoints
3533 A @dfn{breakpoint} makes your program stop whenever a certain point in
3534 the program is reached. For each breakpoint, you can add conditions to
3535 control in finer detail whether your program stops. You can set
3536 breakpoints with the @code{break} command and its variants (@pxref{Set
3537 Breaks, ,Setting Breakpoints}), to specify the place where your program
3538 should stop by line number, function name or exact address in the
3541 On some systems, you can set breakpoints in shared libraries before
3542 the executable is run.
3545 @cindex data breakpoints
3546 @cindex memory tracing
3547 @cindex breakpoint on memory address
3548 @cindex breakpoint on variable modification
3549 A @dfn{watchpoint} is a special breakpoint that stops your program
3550 when the value of an expression changes. The expression may be a value
3551 of a variable, or it could involve values of one or more variables
3552 combined by operators, such as @samp{a + b}. This is sometimes called
3553 @dfn{data breakpoints}. You must use a different command to set
3554 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3555 from that, you can manage a watchpoint like any other breakpoint: you
3556 enable, disable, and delete both breakpoints and watchpoints using the
3559 You can arrange to have values from your program displayed automatically
3560 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3564 @cindex breakpoint on events
3565 A @dfn{catchpoint} is another special breakpoint that stops your program
3566 when a certain kind of event occurs, such as the throwing of a C@t{++}
3567 exception or the loading of a library. As with watchpoints, you use a
3568 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3569 Catchpoints}), but aside from that, you can manage a catchpoint like any
3570 other breakpoint. (To stop when your program receives a signal, use the
3571 @code{handle} command; see @ref{Signals, ,Signals}.)
3573 @cindex breakpoint numbers
3574 @cindex numbers for breakpoints
3575 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3576 catchpoint when you create it; these numbers are successive integers
3577 starting with one. In many of the commands for controlling various
3578 features of breakpoints you use the breakpoint number to say which
3579 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3580 @dfn{disabled}; if disabled, it has no effect on your program until you
3583 @cindex breakpoint ranges
3584 @cindex ranges of breakpoints
3585 Some @value{GDBN} commands accept a range of breakpoints on which to
3586 operate. A breakpoint range is either a single breakpoint number, like
3587 @samp{5}, or two such numbers, in increasing order, separated by a
3588 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3589 all breakpoints in that range are operated on.
3592 * Set Breaks:: Setting breakpoints
3593 * Set Watchpoints:: Setting watchpoints
3594 * Set Catchpoints:: Setting catchpoints
3595 * Delete Breaks:: Deleting breakpoints
3596 * Disabling:: Disabling breakpoints
3597 * Conditions:: Break conditions
3598 * Break Commands:: Breakpoint command lists
3599 * Dynamic Printf:: Dynamic printf
3600 * Save Breakpoints:: How to save breakpoints in a file
3601 * Static Probe Points:: Listing static probe points
3602 * Error in Breakpoints:: ``Cannot insert breakpoints''
3603 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3607 @subsection Setting Breakpoints
3609 @c FIXME LMB what does GDB do if no code on line of breakpt?
3610 @c consider in particular declaration with/without initialization.
3612 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3615 @kindex b @r{(@code{break})}
3616 @vindex $bpnum@r{, convenience variable}
3617 @cindex latest breakpoint
3618 Breakpoints are set with the @code{break} command (abbreviated
3619 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3620 number of the breakpoint you've set most recently; see @ref{Convenience
3621 Vars,, Convenience Variables}, for a discussion of what you can do with
3622 convenience variables.
3625 @item break @var{location}
3626 Set a breakpoint at the given @var{location}, which can specify a
3627 function name, a line number, or an address of an instruction.
3628 (@xref{Specify Location}, for a list of all the possible ways to
3629 specify a @var{location}.) The breakpoint will stop your program just
3630 before it executes any of the code in the specified @var{location}.
3632 When using source languages that permit overloading of symbols, such as
3633 C@t{++}, a function name may refer to more than one possible place to break.
3634 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3637 It is also possible to insert a breakpoint that will stop the program
3638 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3639 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3642 When called without any arguments, @code{break} sets a breakpoint at
3643 the next instruction to be executed in the selected stack frame
3644 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3645 innermost, this makes your program stop as soon as control
3646 returns to that frame. This is similar to the effect of a
3647 @code{finish} command in the frame inside the selected frame---except
3648 that @code{finish} does not leave an active breakpoint. If you use
3649 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3650 the next time it reaches the current location; this may be useful
3653 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3654 least one instruction has been executed. If it did not do this, you
3655 would be unable to proceed past a breakpoint without first disabling the
3656 breakpoint. This rule applies whether or not the breakpoint already
3657 existed when your program stopped.
3659 @item break @dots{} if @var{cond}
3660 Set a breakpoint with condition @var{cond}; evaluate the expression
3661 @var{cond} each time the breakpoint is reached, and stop only if the
3662 value is nonzero---that is, if @var{cond} evaluates as true.
3663 @samp{@dots{}} stands for one of the possible arguments described
3664 above (or no argument) specifying where to break. @xref{Conditions,
3665 ,Break Conditions}, for more information on breakpoint conditions.
3668 @item tbreak @var{args}
3669 Set a breakpoint enabled only for one stop. The @var{args} are the
3670 same as for the @code{break} command, and the breakpoint is set in the same
3671 way, but the breakpoint is automatically deleted after the first time your
3672 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3675 @cindex hardware breakpoints
3676 @item hbreak @var{args}
3677 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
3678 @code{break} command and the breakpoint is set in the same way, but the
3679 breakpoint requires hardware support and some target hardware may not
3680 have this support. The main purpose of this is EPROM/ROM code
3681 debugging, so you can set a breakpoint at an instruction without
3682 changing the instruction. This can be used with the new trap-generation
3683 provided by SPARClite DSU and most x86-based targets. These targets
3684 will generate traps when a program accesses some data or instruction
3685 address that is assigned to the debug registers. However the hardware
3686 breakpoint registers can take a limited number of breakpoints. For
3687 example, on the DSU, only two data breakpoints can be set at a time, and
3688 @value{GDBN} will reject this command if more than two are used. Delete
3689 or disable unused hardware breakpoints before setting new ones
3690 (@pxref{Disabling, ,Disabling Breakpoints}).
3691 @xref{Conditions, ,Break Conditions}.
3692 For remote targets, you can restrict the number of hardware
3693 breakpoints @value{GDBN} will use, see @ref{set remote
3694 hardware-breakpoint-limit}.
3697 @item thbreak @var{args}
3698 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
3699 are the same as for the @code{hbreak} command and the breakpoint is set in
3700 the same way. However, like the @code{tbreak} command,
3701 the breakpoint is automatically deleted after the
3702 first time your program stops there. Also, like the @code{hbreak}
3703 command, the breakpoint requires hardware support and some target hardware
3704 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3705 See also @ref{Conditions, ,Break Conditions}.
3708 @cindex regular expression
3709 @cindex breakpoints at functions matching a regexp
3710 @cindex set breakpoints in many functions
3711 @item rbreak @var{regex}
3712 Set breakpoints on all functions matching the regular expression
3713 @var{regex}. This command sets an unconditional breakpoint on all
3714 matches, printing a list of all breakpoints it set. Once these
3715 breakpoints are set, they are treated just like the breakpoints set with
3716 the @code{break} command. You can delete them, disable them, or make
3717 them conditional the same way as any other breakpoint.
3719 The syntax of the regular expression is the standard one used with tools
3720 like @file{grep}. Note that this is different from the syntax used by
3721 shells, so for instance @code{foo*} matches all functions that include
3722 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3723 @code{.*} leading and trailing the regular expression you supply, so to
3724 match only functions that begin with @code{foo}, use @code{^foo}.
3726 @cindex non-member C@t{++} functions, set breakpoint in
3727 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3728 breakpoints on overloaded functions that are not members of any special
3731 @cindex set breakpoints on all functions
3732 The @code{rbreak} command can be used to set breakpoints in
3733 @strong{all} the functions in a program, like this:
3736 (@value{GDBP}) rbreak .
3739 @item rbreak @var{file}:@var{regex}
3740 If @code{rbreak} is called with a filename qualification, it limits
3741 the search for functions matching the given regular expression to the
3742 specified @var{file}. This can be used, for example, to set breakpoints on
3743 every function in a given file:
3746 (@value{GDBP}) rbreak file.c:.
3749 The colon separating the filename qualifier from the regex may
3750 optionally be surrounded by spaces.
3752 @kindex info breakpoints
3753 @cindex @code{$_} and @code{info breakpoints}
3754 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3755 @itemx info break @r{[}@var{n}@dots{}@r{]}
3756 Print a table of all breakpoints, watchpoints, and catchpoints set and
3757 not deleted. Optional argument @var{n} means print information only
3758 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3759 For each breakpoint, following columns are printed:
3762 @item Breakpoint Numbers
3764 Breakpoint, watchpoint, or catchpoint.
3766 Whether the breakpoint is marked to be disabled or deleted when hit.
3767 @item Enabled or Disabled
3768 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3769 that are not enabled.
3771 Where the breakpoint is in your program, as a memory address. For a
3772 pending breakpoint whose address is not yet known, this field will
3773 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3774 library that has the symbol or line referred by breakpoint is loaded.
3775 See below for details. A breakpoint with several locations will
3776 have @samp{<MULTIPLE>} in this field---see below for details.
3778 Where the breakpoint is in the source for your program, as a file and
3779 line number. For a pending breakpoint, the original string passed to
3780 the breakpoint command will be listed as it cannot be resolved until
3781 the appropriate shared library is loaded in the future.
3785 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3786 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3787 @value{GDBN} on the host's side. If it is ``target'', then the condition
3788 is evaluated by the target. The @code{info break} command shows
3789 the condition on the line following the affected breakpoint, together with
3790 its condition evaluation mode in between parentheses.
3792 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3793 allowed to have a condition specified for it. The condition is not parsed for
3794 validity until a shared library is loaded that allows the pending
3795 breakpoint to resolve to a valid location.
3798 @code{info break} with a breakpoint
3799 number @var{n} as argument lists only that breakpoint. The
3800 convenience variable @code{$_} and the default examining-address for
3801 the @code{x} command are set to the address of the last breakpoint
3802 listed (@pxref{Memory, ,Examining Memory}).
3805 @code{info break} displays a count of the number of times the breakpoint
3806 has been hit. This is especially useful in conjunction with the
3807 @code{ignore} command. You can ignore a large number of breakpoint
3808 hits, look at the breakpoint info to see how many times the breakpoint
3809 was hit, and then run again, ignoring one less than that number. This
3810 will get you quickly to the last hit of that breakpoint.
3813 For a breakpoints with an enable count (xref) greater than 1,
3814 @code{info break} also displays that count.
3818 @value{GDBN} allows you to set any number of breakpoints at the same place in
3819 your program. There is nothing silly or meaningless about this. When
3820 the breakpoints are conditional, this is even useful
3821 (@pxref{Conditions, ,Break Conditions}).
3823 @cindex multiple locations, breakpoints
3824 @cindex breakpoints, multiple locations
3825 It is possible that a breakpoint corresponds to several locations
3826 in your program. Examples of this situation are:
3830 Multiple functions in the program may have the same name.
3833 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3834 instances of the function body, used in different cases.
3837 For a C@t{++} template function, a given line in the function can
3838 correspond to any number of instantiations.
3841 For an inlined function, a given source line can correspond to
3842 several places where that function is inlined.
3845 In all those cases, @value{GDBN} will insert a breakpoint at all
3846 the relevant locations.
3848 A breakpoint with multiple locations is displayed in the breakpoint
3849 table using several rows---one header row, followed by one row for
3850 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3851 address column. The rows for individual locations contain the actual
3852 addresses for locations, and show the functions to which those
3853 locations belong. The number column for a location is of the form
3854 @var{breakpoint-number}.@var{location-number}.
3859 Num Type Disp Enb Address What
3860 1 breakpoint keep y <MULTIPLE>
3862 breakpoint already hit 1 time
3863 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3864 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3867 Each location can be individually enabled or disabled by passing
3868 @var{breakpoint-number}.@var{location-number} as argument to the
3869 @code{enable} and @code{disable} commands. Note that you cannot
3870 delete the individual locations from the list, you can only delete the
3871 entire list of locations that belong to their parent breakpoint (with
3872 the @kbd{delete @var{num}} command, where @var{num} is the number of
3873 the parent breakpoint, 1 in the above example). Disabling or enabling
3874 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3875 that belong to that breakpoint.
3877 @cindex pending breakpoints
3878 It's quite common to have a breakpoint inside a shared library.
3879 Shared libraries can be loaded and unloaded explicitly,
3880 and possibly repeatedly, as the program is executed. To support
3881 this use case, @value{GDBN} updates breakpoint locations whenever
3882 any shared library is loaded or unloaded. Typically, you would
3883 set a breakpoint in a shared library at the beginning of your
3884 debugging session, when the library is not loaded, and when the
3885 symbols from the library are not available. When you try to set
3886 breakpoint, @value{GDBN} will ask you if you want to set
3887 a so called @dfn{pending breakpoint}---breakpoint whose address
3888 is not yet resolved.
3890 After the program is run, whenever a new shared library is loaded,
3891 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3892 shared library contains the symbol or line referred to by some
3893 pending breakpoint, that breakpoint is resolved and becomes an
3894 ordinary breakpoint. When a library is unloaded, all breakpoints
3895 that refer to its symbols or source lines become pending again.
3897 This logic works for breakpoints with multiple locations, too. For
3898 example, if you have a breakpoint in a C@t{++} template function, and
3899 a newly loaded shared library has an instantiation of that template,
3900 a new location is added to the list of locations for the breakpoint.
3902 Except for having unresolved address, pending breakpoints do not
3903 differ from regular breakpoints. You can set conditions or commands,
3904 enable and disable them and perform other breakpoint operations.
3906 @value{GDBN} provides some additional commands for controlling what
3907 happens when the @samp{break} command cannot resolve breakpoint
3908 address specification to an address:
3910 @kindex set breakpoint pending
3911 @kindex show breakpoint pending
3913 @item set breakpoint pending auto
3914 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3915 location, it queries you whether a pending breakpoint should be created.
3917 @item set breakpoint pending on
3918 This indicates that an unrecognized breakpoint location should automatically
3919 result in a pending breakpoint being created.
3921 @item set breakpoint pending off
3922 This indicates that pending breakpoints are not to be created. Any
3923 unrecognized breakpoint location results in an error. This setting does
3924 not affect any pending breakpoints previously created.
3926 @item show breakpoint pending
3927 Show the current behavior setting for creating pending breakpoints.
3930 The settings above only affect the @code{break} command and its
3931 variants. Once breakpoint is set, it will be automatically updated
3932 as shared libraries are loaded and unloaded.
3934 @cindex automatic hardware breakpoints
3935 For some targets, @value{GDBN} can automatically decide if hardware or
3936 software breakpoints should be used, depending on whether the
3937 breakpoint address is read-only or read-write. This applies to
3938 breakpoints set with the @code{break} command as well as to internal
3939 breakpoints set by commands like @code{next} and @code{finish}. For
3940 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3943 You can control this automatic behaviour with the following commands::
3945 @kindex set breakpoint auto-hw
3946 @kindex show breakpoint auto-hw
3948 @item set breakpoint auto-hw on
3949 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3950 will try to use the target memory map to decide if software or hardware
3951 breakpoint must be used.
3953 @item set breakpoint auto-hw off
3954 This indicates @value{GDBN} should not automatically select breakpoint
3955 type. If the target provides a memory map, @value{GDBN} will warn when
3956 trying to set software breakpoint at a read-only address.
3959 @value{GDBN} normally implements breakpoints by replacing the program code
3960 at the breakpoint address with a special instruction, which, when
3961 executed, given control to the debugger. By default, the program
3962 code is so modified only when the program is resumed. As soon as
3963 the program stops, @value{GDBN} restores the original instructions. This
3964 behaviour guards against leaving breakpoints inserted in the
3965 target should gdb abrubptly disconnect. However, with slow remote
3966 targets, inserting and removing breakpoint can reduce the performance.
3967 This behavior can be controlled with the following commands::
3969 @kindex set breakpoint always-inserted
3970 @kindex show breakpoint always-inserted
3972 @item set breakpoint always-inserted off
3973 All breakpoints, including newly added by the user, are inserted in
3974 the target only when the target is resumed. All breakpoints are
3975 removed from the target when it stops. This is the default mode.
3977 @item set breakpoint always-inserted on
3978 Causes all breakpoints to be inserted in the target at all times. If
3979 the user adds a new breakpoint, or changes an existing breakpoint, the
3980 breakpoints in the target are updated immediately. A breakpoint is
3981 removed from the target only when breakpoint itself is deleted.
3984 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3985 when a breakpoint breaks. If the condition is true, then the process being
3986 debugged stops, otherwise the process is resumed.
3988 If the target supports evaluating conditions on its end, @value{GDBN} may
3989 download the breakpoint, together with its conditions, to it.
3991 This feature can be controlled via the following commands:
3993 @kindex set breakpoint condition-evaluation
3994 @kindex show breakpoint condition-evaluation
3996 @item set breakpoint condition-evaluation host
3997 This option commands @value{GDBN} to evaluate the breakpoint
3998 conditions on the host's side. Unconditional breakpoints are sent to
3999 the target which in turn receives the triggers and reports them back to GDB
4000 for condition evaluation. This is the standard evaluation mode.
4002 @item set breakpoint condition-evaluation target
4003 This option commands @value{GDBN} to download breakpoint conditions
4004 to the target at the moment of their insertion. The target
4005 is responsible for evaluating the conditional expression and reporting
4006 breakpoint stop events back to @value{GDBN} whenever the condition
4007 is true. Due to limitations of target-side evaluation, some conditions
4008 cannot be evaluated there, e.g., conditions that depend on local data
4009 that is only known to the host. Examples include
4010 conditional expressions involving convenience variables, complex types
4011 that cannot be handled by the agent expression parser and expressions
4012 that are too long to be sent over to the target, specially when the
4013 target is a remote system. In these cases, the conditions will be
4014 evaluated by @value{GDBN}.
4016 @item set breakpoint condition-evaluation auto
4017 This is the default mode. If the target supports evaluating breakpoint
4018 conditions on its end, @value{GDBN} will download breakpoint conditions to
4019 the target (limitations mentioned previously apply). If the target does
4020 not support breakpoint condition evaluation, then @value{GDBN} will fallback
4021 to evaluating all these conditions on the host's side.
4025 @cindex negative breakpoint numbers
4026 @cindex internal @value{GDBN} breakpoints
4027 @value{GDBN} itself sometimes sets breakpoints in your program for
4028 special purposes, such as proper handling of @code{longjmp} (in C
4029 programs). These internal breakpoints are assigned negative numbers,
4030 starting with @code{-1}; @samp{info breakpoints} does not display them.
4031 You can see these breakpoints with the @value{GDBN} maintenance command
4032 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
4035 @node Set Watchpoints
4036 @subsection Setting Watchpoints
4038 @cindex setting watchpoints
4039 You can use a watchpoint to stop execution whenever the value of an
4040 expression changes, without having to predict a particular place where
4041 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
4042 The expression may be as simple as the value of a single variable, or
4043 as complex as many variables combined by operators. Examples include:
4047 A reference to the value of a single variable.
4050 An address cast to an appropriate data type. For example,
4051 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
4052 address (assuming an @code{int} occupies 4 bytes).
4055 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
4056 expression can use any operators valid in the program's native
4057 language (@pxref{Languages}).
4060 You can set a watchpoint on an expression even if the expression can
4061 not be evaluated yet. For instance, you can set a watchpoint on
4062 @samp{*global_ptr} before @samp{global_ptr} is initialized.
4063 @value{GDBN} will stop when your program sets @samp{global_ptr} and
4064 the expression produces a valid value. If the expression becomes
4065 valid in some other way than changing a variable (e.g.@: if the memory
4066 pointed to by @samp{*global_ptr} becomes readable as the result of a
4067 @code{malloc} call), @value{GDBN} may not stop until the next time
4068 the expression changes.
4070 @cindex software watchpoints
4071 @cindex hardware watchpoints
4072 Depending on your system, watchpoints may be implemented in software or
4073 hardware. @value{GDBN} does software watchpointing by single-stepping your
4074 program and testing the variable's value each time, which is hundreds of
4075 times slower than normal execution. (But this may still be worth it, to
4076 catch errors where you have no clue what part of your program is the
4079 On some systems, such as most PowerPC or x86-based targets,
4080 @value{GDBN} includes support for hardware watchpoints, which do not
4081 slow down the running of your program.
4085 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4086 Set a watchpoint for an expression. @value{GDBN} will break when the
4087 expression @var{expr} is written into by the program and its value
4088 changes. The simplest (and the most popular) use of this command is
4089 to watch the value of a single variable:
4092 (@value{GDBP}) watch foo
4095 If the command includes a @code{@r{[}thread @var{thread-id}@r{]}}
4096 argument, @value{GDBN} breaks only when the thread identified by
4097 @var{thread-id} changes the value of @var{expr}. If any other threads
4098 change the value of @var{expr}, @value{GDBN} will not break. Note
4099 that watchpoints restricted to a single thread in this way only work
4100 with Hardware Watchpoints.
4102 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4103 (see below). The @code{-location} argument tells @value{GDBN} to
4104 instead watch the memory referred to by @var{expr}. In this case,
4105 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4106 and watch the memory at that address. The type of the result is used
4107 to determine the size of the watched memory. If the expression's
4108 result does not have an address, then @value{GDBN} will print an
4111 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4112 of masked watchpoints, if the current architecture supports this
4113 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4114 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4115 to an address to watch. The mask specifies that some bits of an address
4116 (the bits which are reset in the mask) should be ignored when matching
4117 the address accessed by the inferior against the watchpoint address.
4118 Thus, a masked watchpoint watches many addresses simultaneously---those
4119 addresses whose unmasked bits are identical to the unmasked bits in the
4120 watchpoint address. The @code{mask} argument implies @code{-location}.
4124 (@value{GDBP}) watch foo mask 0xffff00ff
4125 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4129 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4130 Set a watchpoint that will break when the value of @var{expr} is read
4134 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4135 Set a watchpoint that will break when @var{expr} is either read from
4136 or written into by the program.
4138 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
4139 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
4140 This command prints a list of watchpoints, using the same format as
4141 @code{info break} (@pxref{Set Breaks}).
4144 If you watch for a change in a numerically entered address you need to
4145 dereference it, as the address itself is just a constant number which will
4146 never change. @value{GDBN} refuses to create a watchpoint that watches
4147 a never-changing value:
4150 (@value{GDBP}) watch 0x600850
4151 Cannot watch constant value 0x600850.
4152 (@value{GDBP}) watch *(int *) 0x600850
4153 Watchpoint 1: *(int *) 6293584
4156 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4157 watchpoints execute very quickly, and the debugger reports a change in
4158 value at the exact instruction where the change occurs. If @value{GDBN}
4159 cannot set a hardware watchpoint, it sets a software watchpoint, which
4160 executes more slowly and reports the change in value at the next
4161 @emph{statement}, not the instruction, after the change occurs.
4163 @cindex use only software watchpoints
4164 You can force @value{GDBN} to use only software watchpoints with the
4165 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4166 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4167 the underlying system supports them. (Note that hardware-assisted
4168 watchpoints that were set @emph{before} setting
4169 @code{can-use-hw-watchpoints} to zero will still use the hardware
4170 mechanism of watching expression values.)
4173 @item set can-use-hw-watchpoints
4174 @kindex set can-use-hw-watchpoints
4175 Set whether or not to use hardware watchpoints.
4177 @item show can-use-hw-watchpoints
4178 @kindex show can-use-hw-watchpoints
4179 Show the current mode of using hardware watchpoints.
4182 For remote targets, you can restrict the number of hardware
4183 watchpoints @value{GDBN} will use, see @ref{set remote
4184 hardware-breakpoint-limit}.
4186 When you issue the @code{watch} command, @value{GDBN} reports
4189 Hardware watchpoint @var{num}: @var{expr}
4193 if it was able to set a hardware watchpoint.
4195 Currently, the @code{awatch} and @code{rwatch} commands can only set
4196 hardware watchpoints, because accesses to data that don't change the
4197 value of the watched expression cannot be detected without examining
4198 every instruction as it is being executed, and @value{GDBN} does not do
4199 that currently. If @value{GDBN} finds that it is unable to set a
4200 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4201 will print a message like this:
4204 Expression cannot be implemented with read/access watchpoint.
4207 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4208 data type of the watched expression is wider than what a hardware
4209 watchpoint on the target machine can handle. For example, some systems
4210 can only watch regions that are up to 4 bytes wide; on such systems you
4211 cannot set hardware watchpoints for an expression that yields a
4212 double-precision floating-point number (which is typically 8 bytes
4213 wide). As a work-around, it might be possible to break the large region
4214 into a series of smaller ones and watch them with separate watchpoints.
4216 If you set too many hardware watchpoints, @value{GDBN} might be unable
4217 to insert all of them when you resume the execution of your program.
4218 Since the precise number of active watchpoints is unknown until such
4219 time as the program is about to be resumed, @value{GDBN} might not be
4220 able to warn you about this when you set the watchpoints, and the
4221 warning will be printed only when the program is resumed:
4224 Hardware watchpoint @var{num}: Could not insert watchpoint
4228 If this happens, delete or disable some of the watchpoints.
4230 Watching complex expressions that reference many variables can also
4231 exhaust the resources available for hardware-assisted watchpoints.
4232 That's because @value{GDBN} needs to watch every variable in the
4233 expression with separately allocated resources.
4235 If you call a function interactively using @code{print} or @code{call},
4236 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4237 kind of breakpoint or the call completes.
4239 @value{GDBN} automatically deletes watchpoints that watch local
4240 (automatic) variables, or expressions that involve such variables, when
4241 they go out of scope, that is, when the execution leaves the block in
4242 which these variables were defined. In particular, when the program
4243 being debugged terminates, @emph{all} local variables go out of scope,
4244 and so only watchpoints that watch global variables remain set. If you
4245 rerun the program, you will need to set all such watchpoints again. One
4246 way of doing that would be to set a code breakpoint at the entry to the
4247 @code{main} function and when it breaks, set all the watchpoints.
4249 @cindex watchpoints and threads
4250 @cindex threads and watchpoints
4251 In multi-threaded programs, watchpoints will detect changes to the
4252 watched expression from every thread.
4255 @emph{Warning:} In multi-threaded programs, software watchpoints
4256 have only limited usefulness. If @value{GDBN} creates a software
4257 watchpoint, it can only watch the value of an expression @emph{in a
4258 single thread}. If you are confident that the expression can only
4259 change due to the current thread's activity (and if you are also
4260 confident that no other thread can become current), then you can use
4261 software watchpoints as usual. However, @value{GDBN} may not notice
4262 when a non-current thread's activity changes the expression. (Hardware
4263 watchpoints, in contrast, watch an expression in all threads.)
4266 @xref{set remote hardware-watchpoint-limit}.
4268 @node Set Catchpoints
4269 @subsection Setting Catchpoints
4270 @cindex catchpoints, setting
4271 @cindex exception handlers
4272 @cindex event handling
4274 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4275 kinds of program events, such as C@t{++} exceptions or the loading of a
4276 shared library. Use the @code{catch} command to set a catchpoint.
4280 @item catch @var{event}
4281 Stop when @var{event} occurs. The @var{event} can be any of the following:
4284 @item throw @r{[}@var{regexp}@r{]}
4285 @itemx rethrow @r{[}@var{regexp}@r{]}
4286 @itemx catch @r{[}@var{regexp}@r{]}
4288 @kindex catch rethrow
4290 @cindex stop on C@t{++} exceptions
4291 The throwing, re-throwing, or catching of a C@t{++} exception.
4293 If @var{regexp} is given, then only exceptions whose type matches the
4294 regular expression will be caught.
4296 @vindex $_exception@r{, convenience variable}
4297 The convenience variable @code{$_exception} is available at an
4298 exception-related catchpoint, on some systems. This holds the
4299 exception being thrown.
4301 There are currently some limitations to C@t{++} exception handling in
4306 The support for these commands is system-dependent. Currently, only
4307 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4311 The regular expression feature and the @code{$_exception} convenience
4312 variable rely on the presence of some SDT probes in @code{libstdc++}.
4313 If these probes are not present, then these features cannot be used.
4314 These probes were first available in the GCC 4.8 release, but whether
4315 or not they are available in your GCC also depends on how it was
4319 The @code{$_exception} convenience variable is only valid at the
4320 instruction at which an exception-related catchpoint is set.
4323 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4324 location in the system library which implements runtime exception
4325 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4326 (@pxref{Selection}) to get to your code.
4329 If you call a function interactively, @value{GDBN} normally returns
4330 control to you when the function has finished executing. If the call
4331 raises an exception, however, the call may bypass the mechanism that
4332 returns control to you and cause your program either to abort or to
4333 simply continue running until it hits a breakpoint, catches a signal
4334 that @value{GDBN} is listening for, or exits. This is the case even if
4335 you set a catchpoint for the exception; catchpoints on exceptions are
4336 disabled within interactive calls. @xref{Calling}, for information on
4337 controlling this with @code{set unwind-on-terminating-exception}.
4340 You cannot raise an exception interactively.
4343 You cannot install an exception handler interactively.
4347 @kindex catch exception
4348 @cindex Ada exception catching
4349 @cindex catch Ada exceptions
4350 An Ada exception being raised. If an exception name is specified
4351 at the end of the command (eg @code{catch exception Program_Error}),
4352 the debugger will stop only when this specific exception is raised.
4353 Otherwise, the debugger stops execution when any Ada exception is raised.
4355 When inserting an exception catchpoint on a user-defined exception whose
4356 name is identical to one of the exceptions defined by the language, the
4357 fully qualified name must be used as the exception name. Otherwise,
4358 @value{GDBN} will assume that it should stop on the pre-defined exception
4359 rather than the user-defined one. For instance, assuming an exception
4360 called @code{Constraint_Error} is defined in package @code{Pck}, then
4361 the command to use to catch such exceptions is @kbd{catch exception
4362 Pck.Constraint_Error}.
4364 @item exception unhandled
4365 @kindex catch exception unhandled
4366 An exception that was raised but is not handled by the program.
4369 @kindex catch assert
4370 A failed Ada assertion.
4374 @cindex break on fork/exec
4375 A call to @code{exec}.
4378 @itemx syscall @r{[}@var{name} @r{|} @var{number} @r{|} @r{group:}@var{groupname} @r{|} @r{g:}@var{groupname}@r{]} @dots{}
4379 @kindex catch syscall
4380 @cindex break on a system call.
4381 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4382 syscall is a mechanism for application programs to request a service
4383 from the operating system (OS) or one of the OS system services.
4384 @value{GDBN} can catch some or all of the syscalls issued by the
4385 debuggee, and show the related information for each syscall. If no
4386 argument is specified, calls to and returns from all system calls
4389 @var{name} can be any system call name that is valid for the
4390 underlying OS. Just what syscalls are valid depends on the OS. On
4391 GNU and Unix systems, you can find the full list of valid syscall
4392 names on @file{/usr/include/asm/unistd.h}.
4394 @c For MS-Windows, the syscall names and the corresponding numbers
4395 @c can be found, e.g., on this URL:
4396 @c http://www.metasploit.com/users/opcode/syscalls.html
4397 @c but we don't support Windows syscalls yet.
4399 Normally, @value{GDBN} knows in advance which syscalls are valid for
4400 each OS, so you can use the @value{GDBN} command-line completion
4401 facilities (@pxref{Completion,, command completion}) to list the
4404 You may also specify the system call numerically. A syscall's
4405 number is the value passed to the OS's syscall dispatcher to
4406 identify the requested service. When you specify the syscall by its
4407 name, @value{GDBN} uses its database of syscalls to convert the name
4408 into the corresponding numeric code, but using the number directly
4409 may be useful if @value{GDBN}'s database does not have the complete
4410 list of syscalls on your system (e.g., because @value{GDBN} lags
4411 behind the OS upgrades).
4413 You may specify a group of related syscalls to be caught at once using
4414 the @code{group:} syntax (@code{g:} is a shorter equivalent). For
4415 instance, on some platforms @value{GDBN} allows you to catch all
4416 network related syscalls, by passing the argument @code{group:network}
4417 to @code{catch syscall}. Note that not all syscall groups are
4418 available in every system. You can use the command completion
4419 facilities (@pxref{Completion,, command completion}) to list the
4420 syscall groups available on your environment.
4422 The example below illustrates how this command works if you don't provide
4426 (@value{GDBP}) catch syscall
4427 Catchpoint 1 (syscall)
4429 Starting program: /tmp/catch-syscall
4431 Catchpoint 1 (call to syscall 'close'), \
4432 0xffffe424 in __kernel_vsyscall ()
4436 Catchpoint 1 (returned from syscall 'close'), \
4437 0xffffe424 in __kernel_vsyscall ()
4441 Here is an example of catching a system call by name:
4444 (@value{GDBP}) catch syscall chroot
4445 Catchpoint 1 (syscall 'chroot' [61])
4447 Starting program: /tmp/catch-syscall
4449 Catchpoint 1 (call to syscall 'chroot'), \
4450 0xffffe424 in __kernel_vsyscall ()
4454 Catchpoint 1 (returned from syscall 'chroot'), \
4455 0xffffe424 in __kernel_vsyscall ()
4459 An example of specifying a system call numerically. In the case
4460 below, the syscall number has a corresponding entry in the XML
4461 file, so @value{GDBN} finds its name and prints it:
4464 (@value{GDBP}) catch syscall 252
4465 Catchpoint 1 (syscall(s) 'exit_group')
4467 Starting program: /tmp/catch-syscall
4469 Catchpoint 1 (call to syscall 'exit_group'), \
4470 0xffffe424 in __kernel_vsyscall ()
4474 Program exited normally.
4478 Here is an example of catching a syscall group:
4481 (@value{GDBP}) catch syscall group:process
4482 Catchpoint 1 (syscalls 'exit' [1] 'fork' [2] 'waitpid' [7]
4483 'execve' [11] 'wait4' [114] 'clone' [120] 'vfork' [190]
4484 'exit_group' [252] 'waitid' [284] 'unshare' [310])
4486 Starting program: /tmp/catch-syscall
4488 Catchpoint 1 (call to syscall fork), 0x00007ffff7df4e27 in open64 ()
4489 from /lib64/ld-linux-x86-64.so.2
4495 However, there can be situations when there is no corresponding name
4496 in XML file for that syscall number. In this case, @value{GDBN} prints
4497 a warning message saying that it was not able to find the syscall name,
4498 but the catchpoint will be set anyway. See the example below:
4501 (@value{GDBP}) catch syscall 764
4502 warning: The number '764' does not represent a known syscall.
4503 Catchpoint 2 (syscall 764)
4507 If you configure @value{GDBN} using the @samp{--without-expat} option,
4508 it will not be able to display syscall names. Also, if your
4509 architecture does not have an XML file describing its system calls,
4510 you will not be able to see the syscall names. It is important to
4511 notice that these two features are used for accessing the syscall
4512 name database. In either case, you will see a warning like this:
4515 (@value{GDBP}) catch syscall
4516 warning: Could not open "syscalls/i386-linux.xml"
4517 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4518 GDB will not be able to display syscall names.
4519 Catchpoint 1 (syscall)
4523 Of course, the file name will change depending on your architecture and system.
4525 Still using the example above, you can also try to catch a syscall by its
4526 number. In this case, you would see something like:
4529 (@value{GDBP}) catch syscall 252
4530 Catchpoint 1 (syscall(s) 252)
4533 Again, in this case @value{GDBN} would not be able to display syscall's names.
4537 A call to @code{fork}.
4541 A call to @code{vfork}.
4543 @item load @r{[}regexp@r{]}
4544 @itemx unload @r{[}regexp@r{]}
4546 @kindex catch unload
4547 The loading or unloading of a shared library. If @var{regexp} is
4548 given, then the catchpoint will stop only if the regular expression
4549 matches one of the affected libraries.
4551 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4552 @kindex catch signal
4553 The delivery of a signal.
4555 With no arguments, this catchpoint will catch any signal that is not
4556 used internally by @value{GDBN}, specifically, all signals except
4557 @samp{SIGTRAP} and @samp{SIGINT}.
4559 With the argument @samp{all}, all signals, including those used by
4560 @value{GDBN}, will be caught. This argument cannot be used with other
4563 Otherwise, the arguments are a list of signal names as given to
4564 @code{handle} (@pxref{Signals}). Only signals specified in this list
4567 One reason that @code{catch signal} can be more useful than
4568 @code{handle} is that you can attach commands and conditions to the
4571 When a signal is caught by a catchpoint, the signal's @code{stop} and
4572 @code{print} settings, as specified by @code{handle}, are ignored.
4573 However, whether the signal is still delivered to the inferior depends
4574 on the @code{pass} setting; this can be changed in the catchpoint's
4579 @item tcatch @var{event}
4581 Set a catchpoint that is enabled only for one stop. The catchpoint is
4582 automatically deleted after the first time the event is caught.
4586 Use the @code{info break} command to list the current catchpoints.
4590 @subsection Deleting Breakpoints
4592 @cindex clearing breakpoints, watchpoints, catchpoints
4593 @cindex deleting breakpoints, watchpoints, catchpoints
4594 It is often necessary to eliminate a breakpoint, watchpoint, or
4595 catchpoint once it has done its job and you no longer want your program
4596 to stop there. This is called @dfn{deleting} the breakpoint. A
4597 breakpoint that has been deleted no longer exists; it is forgotten.
4599 With the @code{clear} command you can delete breakpoints according to
4600 where they are in your program. With the @code{delete} command you can
4601 delete individual breakpoints, watchpoints, or catchpoints by specifying
4602 their breakpoint numbers.
4604 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4605 automatically ignores breakpoints on the first instruction to be executed
4606 when you continue execution without changing the execution address.
4611 Delete any breakpoints at the next instruction to be executed in the
4612 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4613 the innermost frame is selected, this is a good way to delete a
4614 breakpoint where your program just stopped.
4616 @item clear @var{location}
4617 Delete any breakpoints set at the specified @var{location}.
4618 @xref{Specify Location}, for the various forms of @var{location}; the
4619 most useful ones are listed below:
4622 @item clear @var{function}
4623 @itemx clear @var{filename}:@var{function}
4624 Delete any breakpoints set at entry to the named @var{function}.
4626 @item clear @var{linenum}
4627 @itemx clear @var{filename}:@var{linenum}
4628 Delete any breakpoints set at or within the code of the specified
4629 @var{linenum} of the specified @var{filename}.
4632 @cindex delete breakpoints
4634 @kindex d @r{(@code{delete})}
4635 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4636 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4637 ranges specified as arguments. If no argument is specified, delete all
4638 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4639 confirm off}). You can abbreviate this command as @code{d}.
4643 @subsection Disabling Breakpoints
4645 @cindex enable/disable a breakpoint
4646 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4647 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4648 it had been deleted, but remembers the information on the breakpoint so
4649 that you can @dfn{enable} it again later.
4651 You disable and enable breakpoints, watchpoints, and catchpoints with
4652 the @code{enable} and @code{disable} commands, optionally specifying
4653 one or more breakpoint numbers as arguments. Use @code{info break} to
4654 print a list of all breakpoints, watchpoints, and catchpoints if you
4655 do not know which numbers to use.
4657 Disabling and enabling a breakpoint that has multiple locations
4658 affects all of its locations.
4660 A breakpoint, watchpoint, or catchpoint can have any of several
4661 different states of enablement:
4665 Enabled. The breakpoint stops your program. A breakpoint set
4666 with the @code{break} command starts out in this state.
4668 Disabled. The breakpoint has no effect on your program.
4670 Enabled once. The breakpoint stops your program, but then becomes
4673 Enabled for a count. The breakpoint stops your program for the next
4674 N times, then becomes disabled.
4676 Enabled for deletion. The breakpoint stops your program, but
4677 immediately after it does so it is deleted permanently. A breakpoint
4678 set with the @code{tbreak} command starts out in this state.
4681 You can use the following commands to enable or disable breakpoints,
4682 watchpoints, and catchpoints:
4686 @kindex dis @r{(@code{disable})}
4687 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4688 Disable the specified breakpoints---or all breakpoints, if none are
4689 listed. A disabled breakpoint has no effect but is not forgotten. All
4690 options such as ignore-counts, conditions and commands are remembered in
4691 case the breakpoint is enabled again later. You may abbreviate
4692 @code{disable} as @code{dis}.
4695 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4696 Enable the specified breakpoints (or all defined breakpoints). They
4697 become effective once again in stopping your program.
4699 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4700 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4701 of these breakpoints immediately after stopping your program.
4703 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4704 Enable the specified breakpoints temporarily. @value{GDBN} records
4705 @var{count} with each of the specified breakpoints, and decrements a
4706 breakpoint's count when it is hit. When any count reaches 0,
4707 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4708 count (@pxref{Conditions, ,Break Conditions}), that will be
4709 decremented to 0 before @var{count} is affected.
4711 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4712 Enable the specified breakpoints to work once, then die. @value{GDBN}
4713 deletes any of these breakpoints as soon as your program stops there.
4714 Breakpoints set by the @code{tbreak} command start out in this state.
4717 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4718 @c confusing: tbreak is also initially enabled.
4719 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4720 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4721 subsequently, they become disabled or enabled only when you use one of
4722 the commands above. (The command @code{until} can set and delete a
4723 breakpoint of its own, but it does not change the state of your other
4724 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4728 @subsection Break Conditions
4729 @cindex conditional breakpoints
4730 @cindex breakpoint conditions
4732 @c FIXME what is scope of break condition expr? Context where wanted?
4733 @c in particular for a watchpoint?
4734 The simplest sort of breakpoint breaks every time your program reaches a
4735 specified place. You can also specify a @dfn{condition} for a
4736 breakpoint. A condition is just a Boolean expression in your
4737 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4738 a condition evaluates the expression each time your program reaches it,
4739 and your program stops only if the condition is @emph{true}.
4741 This is the converse of using assertions for program validation; in that
4742 situation, you want to stop when the assertion is violated---that is,
4743 when the condition is false. In C, if you want to test an assertion expressed
4744 by the condition @var{assert}, you should set the condition
4745 @samp{! @var{assert}} on the appropriate breakpoint.
4747 Conditions are also accepted for watchpoints; you may not need them,
4748 since a watchpoint is inspecting the value of an expression anyhow---but
4749 it might be simpler, say, to just set a watchpoint on a variable name,
4750 and specify a condition that tests whether the new value is an interesting
4753 Break conditions can have side effects, and may even call functions in
4754 your program. This can be useful, for example, to activate functions
4755 that log program progress, or to use your own print functions to
4756 format special data structures. The effects are completely predictable
4757 unless there is another enabled breakpoint at the same address. (In
4758 that case, @value{GDBN} might see the other breakpoint first and stop your
4759 program without checking the condition of this one.) Note that
4760 breakpoint commands are usually more convenient and flexible than break
4762 purpose of performing side effects when a breakpoint is reached
4763 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4765 Breakpoint conditions can also be evaluated on the target's side if
4766 the target supports it. Instead of evaluating the conditions locally,
4767 @value{GDBN} encodes the expression into an agent expression
4768 (@pxref{Agent Expressions}) suitable for execution on the target,
4769 independently of @value{GDBN}. Global variables become raw memory
4770 locations, locals become stack accesses, and so forth.
4772 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4773 when its condition evaluates to true. This mechanism may provide faster
4774 response times depending on the performance characteristics of the target
4775 since it does not need to keep @value{GDBN} informed about
4776 every breakpoint trigger, even those with false conditions.
4778 Break conditions can be specified when a breakpoint is set, by using
4779 @samp{if} in the arguments to the @code{break} command. @xref{Set
4780 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4781 with the @code{condition} command.
4783 You can also use the @code{if} keyword with the @code{watch} command.
4784 The @code{catch} command does not recognize the @code{if} keyword;
4785 @code{condition} is the only way to impose a further condition on a
4790 @item condition @var{bnum} @var{expression}
4791 Specify @var{expression} as the break condition for breakpoint,
4792 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4793 breakpoint @var{bnum} stops your program only if the value of
4794 @var{expression} is true (nonzero, in C). When you use
4795 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4796 syntactic correctness, and to determine whether symbols in it have
4797 referents in the context of your breakpoint. If @var{expression} uses
4798 symbols not referenced in the context of the breakpoint, @value{GDBN}
4799 prints an error message:
4802 No symbol "foo" in current context.
4807 not actually evaluate @var{expression} at the time the @code{condition}
4808 command (or a command that sets a breakpoint with a condition, like
4809 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4811 @item condition @var{bnum}
4812 Remove the condition from breakpoint number @var{bnum}. It becomes
4813 an ordinary unconditional breakpoint.
4816 @cindex ignore count (of breakpoint)
4817 A special case of a breakpoint condition is to stop only when the
4818 breakpoint has been reached a certain number of times. This is so
4819 useful that there is a special way to do it, using the @dfn{ignore
4820 count} of the breakpoint. Every breakpoint has an ignore count, which
4821 is an integer. Most of the time, the ignore count is zero, and
4822 therefore has no effect. But if your program reaches a breakpoint whose
4823 ignore count is positive, then instead of stopping, it just decrements
4824 the ignore count by one and continues. As a result, if the ignore count
4825 value is @var{n}, the breakpoint does not stop the next @var{n} times
4826 your program reaches it.
4830 @item ignore @var{bnum} @var{count}
4831 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4832 The next @var{count} times the breakpoint is reached, your program's
4833 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4836 To make the breakpoint stop the next time it is reached, specify
4839 When you use @code{continue} to resume execution of your program from a
4840 breakpoint, you can specify an ignore count directly as an argument to
4841 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4842 Stepping,,Continuing and Stepping}.
4844 If a breakpoint has a positive ignore count and a condition, the
4845 condition is not checked. Once the ignore count reaches zero,
4846 @value{GDBN} resumes checking the condition.
4848 You could achieve the effect of the ignore count with a condition such
4849 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4850 is decremented each time. @xref{Convenience Vars, ,Convenience
4854 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4857 @node Break Commands
4858 @subsection Breakpoint Command Lists
4860 @cindex breakpoint commands
4861 You can give any breakpoint (or watchpoint or catchpoint) a series of
4862 commands to execute when your program stops due to that breakpoint. For
4863 example, you might want to print the values of certain expressions, or
4864 enable other breakpoints.
4868 @kindex end@r{ (breakpoint commands)}
4869 @item commands @r{[}@var{range}@dots{}@r{]}
4870 @itemx @dots{} @var{command-list} @dots{}
4872 Specify a list of commands for the given breakpoints. The commands
4873 themselves appear on the following lines. Type a line containing just
4874 @code{end} to terminate the commands.
4876 To remove all commands from a breakpoint, type @code{commands} and
4877 follow it immediately with @code{end}; that is, give no commands.
4879 With no argument, @code{commands} refers to the last breakpoint,
4880 watchpoint, or catchpoint set (not to the breakpoint most recently
4881 encountered). If the most recent breakpoints were set with a single
4882 command, then the @code{commands} will apply to all the breakpoints
4883 set by that command. This applies to breakpoints set by
4884 @code{rbreak}, and also applies when a single @code{break} command
4885 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4889 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4890 disabled within a @var{command-list}.
4892 You can use breakpoint commands to start your program up again. Simply
4893 use the @code{continue} command, or @code{step}, or any other command
4894 that resumes execution.
4896 Any other commands in the command list, after a command that resumes
4897 execution, are ignored. This is because any time you resume execution
4898 (even with a simple @code{next} or @code{step}), you may encounter
4899 another breakpoint---which could have its own command list, leading to
4900 ambiguities about which list to execute.
4903 If the first command you specify in a command list is @code{silent}, the
4904 usual message about stopping at a breakpoint is not printed. This may
4905 be desirable for breakpoints that are to print a specific message and
4906 then continue. If none of the remaining commands print anything, you
4907 see no sign that the breakpoint was reached. @code{silent} is
4908 meaningful only at the beginning of a breakpoint command list.
4910 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4911 print precisely controlled output, and are often useful in silent
4912 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4914 For example, here is how you could use breakpoint commands to print the
4915 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4921 printf "x is %d\n",x
4926 One application for breakpoint commands is to compensate for one bug so
4927 you can test for another. Put a breakpoint just after the erroneous line
4928 of code, give it a condition to detect the case in which something
4929 erroneous has been done, and give it commands to assign correct values
4930 to any variables that need them. End with the @code{continue} command
4931 so that your program does not stop, and start with the @code{silent}
4932 command so that no output is produced. Here is an example:
4943 @node Dynamic Printf
4944 @subsection Dynamic Printf
4946 @cindex dynamic printf
4948 The dynamic printf command @code{dprintf} combines a breakpoint with
4949 formatted printing of your program's data to give you the effect of
4950 inserting @code{printf} calls into your program on-the-fly, without
4951 having to recompile it.
4953 In its most basic form, the output goes to the GDB console. However,
4954 you can set the variable @code{dprintf-style} for alternate handling.
4955 For instance, you can ask to format the output by calling your
4956 program's @code{printf} function. This has the advantage that the
4957 characters go to the program's output device, so they can recorded in
4958 redirects to files and so forth.
4960 If you are doing remote debugging with a stub or agent, you can also
4961 ask to have the printf handled by the remote agent. In addition to
4962 ensuring that the output goes to the remote program's device along
4963 with any other output the program might produce, you can also ask that
4964 the dprintf remain active even after disconnecting from the remote
4965 target. Using the stub/agent is also more efficient, as it can do
4966 everything without needing to communicate with @value{GDBN}.
4970 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4971 Whenever execution reaches @var{location}, print the values of one or
4972 more @var{expressions} under the control of the string @var{template}.
4973 To print several values, separate them with commas.
4975 @item set dprintf-style @var{style}
4976 Set the dprintf output to be handled in one of several different
4977 styles enumerated below. A change of style affects all existing
4978 dynamic printfs immediately. (If you need individual control over the
4979 print commands, simply define normal breakpoints with
4980 explicitly-supplied command lists.)
4983 @kindex dprintf-style gdb
4984 Handle the output using the @value{GDBN} @code{printf} command.
4987 @kindex dprintf-style call
4988 Handle the output by calling a function in your program (normally
4992 @kindex dprintf-style agent
4993 Have the remote debugging agent (such as @code{gdbserver}) handle
4994 the output itself. This style is only available for agents that
4995 support running commands on the target.
4997 @item set dprintf-function @var{function}
4998 Set the function to call if the dprintf style is @code{call}. By
4999 default its value is @code{printf}. You may set it to any expression.
5000 that @value{GDBN} can evaluate to a function, as per the @code{call}
5003 @item set dprintf-channel @var{channel}
5004 Set a ``channel'' for dprintf. If set to a non-empty value,
5005 @value{GDBN} will evaluate it as an expression and pass the result as
5006 a first argument to the @code{dprintf-function}, in the manner of
5007 @code{fprintf} and similar functions. Otherwise, the dprintf format
5008 string will be the first argument, in the manner of @code{printf}.
5010 As an example, if you wanted @code{dprintf} output to go to a logfile
5011 that is a standard I/O stream assigned to the variable @code{mylog},
5012 you could do the following:
5015 (gdb) set dprintf-style call
5016 (gdb) set dprintf-function fprintf
5017 (gdb) set dprintf-channel mylog
5018 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
5019 Dprintf 1 at 0x123456: file main.c, line 25.
5021 1 dprintf keep y 0x00123456 in main at main.c:25
5022 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
5027 Note that the @code{info break} displays the dynamic printf commands
5028 as normal breakpoint commands; you can thus easily see the effect of
5029 the variable settings.
5031 @item set disconnected-dprintf on
5032 @itemx set disconnected-dprintf off
5033 @kindex set disconnected-dprintf
5034 Choose whether @code{dprintf} commands should continue to run if
5035 @value{GDBN} has disconnected from the target. This only applies
5036 if the @code{dprintf-style} is @code{agent}.
5038 @item show disconnected-dprintf off
5039 @kindex show disconnected-dprintf
5040 Show the current choice for disconnected @code{dprintf}.
5044 @value{GDBN} does not check the validity of function and channel,
5045 relying on you to supply values that are meaningful for the contexts
5046 in which they are being used. For instance, the function and channel
5047 may be the values of local variables, but if that is the case, then
5048 all enabled dynamic prints must be at locations within the scope of
5049 those locals. If evaluation fails, @value{GDBN} will report an error.
5051 @node Save Breakpoints
5052 @subsection How to save breakpoints to a file
5054 To save breakpoint definitions to a file use the @w{@code{save
5055 breakpoints}} command.
5058 @kindex save breakpoints
5059 @cindex save breakpoints to a file for future sessions
5060 @item save breakpoints [@var{filename}]
5061 This command saves all current breakpoint definitions together with
5062 their commands and ignore counts, into a file @file{@var{filename}}
5063 suitable for use in a later debugging session. This includes all
5064 types of breakpoints (breakpoints, watchpoints, catchpoints,
5065 tracepoints). To read the saved breakpoint definitions, use the
5066 @code{source} command (@pxref{Command Files}). Note that watchpoints
5067 with expressions involving local variables may fail to be recreated
5068 because it may not be possible to access the context where the
5069 watchpoint is valid anymore. Because the saved breakpoint definitions
5070 are simply a sequence of @value{GDBN} commands that recreate the
5071 breakpoints, you can edit the file in your favorite editing program,
5072 and remove the breakpoint definitions you're not interested in, or
5073 that can no longer be recreated.
5076 @node Static Probe Points
5077 @subsection Static Probe Points
5079 @cindex static probe point, SystemTap
5080 @cindex static probe point, DTrace
5081 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
5082 for Statically Defined Tracing, and the probes are designed to have a tiny
5083 runtime code and data footprint, and no dynamic relocations.
5085 Currently, the following types of probes are supported on
5086 ELF-compatible systems:
5090 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
5091 @acronym{SDT} probes@footnote{See
5092 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
5093 for more information on how to add @code{SystemTap} @acronym{SDT}
5094 probes in your applications.}. @code{SystemTap} probes are usable
5095 from assembly, C and C@t{++} languages@footnote{See
5096 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
5097 for a good reference on how the @acronym{SDT} probes are implemented.}.
5099 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
5100 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
5104 @cindex semaphores on static probe points
5105 Some @code{SystemTap} probes have an associated semaphore variable;
5106 for instance, this happens automatically if you defined your probe
5107 using a DTrace-style @file{.d} file. If your probe has a semaphore,
5108 @value{GDBN} will automatically enable it when you specify a
5109 breakpoint using the @samp{-probe-stap} notation. But, if you put a
5110 breakpoint at a probe's location by some other method (e.g.,
5111 @code{break file:line}), then @value{GDBN} will not automatically set
5112 the semaphore. @code{DTrace} probes do not support semaphores.
5114 You can examine the available static static probes using @code{info
5115 probes}, with optional arguments:
5119 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5120 If given, @var{type} is either @code{stap} for listing
5121 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5122 probes. If omitted all probes are listed regardless of their types.
5124 If given, @var{provider} is a regular expression used to match against provider
5125 names when selecting which probes to list. If omitted, probes by all
5126 probes from all providers are listed.
5128 If given, @var{name} is a regular expression to match against probe names
5129 when selecting which probes to list. If omitted, probe names are not
5130 considered when deciding whether to display them.
5132 If given, @var{objfile} is a regular expression used to select which
5133 object files (executable or shared libraries) to examine. If not
5134 given, all object files are considered.
5136 @item info probes all
5137 List the available static probes, from all types.
5140 @cindex enabling and disabling probes
5141 Some probe points can be enabled and/or disabled. The effect of
5142 enabling or disabling a probe depends on the type of probe being
5143 handled. Some @code{DTrace} probes can be enabled or
5144 disabled, but @code{SystemTap} probes cannot be disabled.
5146 You can enable (or disable) one or more probes using the following
5147 commands, with optional arguments:
5150 @kindex enable probes
5151 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5152 If given, @var{provider} is a regular expression used to match against
5153 provider names when selecting which probes to enable. If omitted,
5154 all probes from all providers are enabled.
5156 If given, @var{name} is a regular expression to match against probe
5157 names when selecting which probes to enable. If omitted, probe names
5158 are not considered when deciding whether to enable them.
5160 If given, @var{objfile} is a regular expression used to select which
5161 object files (executable or shared libraries) to examine. If not
5162 given, all object files are considered.
5164 @kindex disable probes
5165 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5166 See the @code{enable probes} command above for a description of the
5167 optional arguments accepted by this command.
5170 @vindex $_probe_arg@r{, convenience variable}
5171 A probe may specify up to twelve arguments. These are available at the
5172 point at which the probe is defined---that is, when the current PC is
5173 at the probe's location. The arguments are available using the
5174 convenience variables (@pxref{Convenience Vars})
5175 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
5176 probes each probe argument is an integer of the appropriate size;
5177 types are not preserved. In @code{DTrace} probes types are preserved
5178 provided that they are recognized as such by @value{GDBN}; otherwise
5179 the value of the probe argument will be a long integer. The
5180 convenience variable @code{$_probe_argc} holds the number of arguments
5181 at the current probe point.
5183 These variables are always available, but attempts to access them at
5184 any location other than a probe point will cause @value{GDBN} to give
5188 @c @ifclear BARETARGET
5189 @node Error in Breakpoints
5190 @subsection ``Cannot insert breakpoints''
5192 If you request too many active hardware-assisted breakpoints and
5193 watchpoints, you will see this error message:
5195 @c FIXME: the precise wording of this message may change; the relevant
5196 @c source change is not committed yet (Sep 3, 1999).
5198 Stopped; cannot insert breakpoints.
5199 You may have requested too many hardware breakpoints and watchpoints.
5203 This message is printed when you attempt to resume the program, since
5204 only then @value{GDBN} knows exactly how many hardware breakpoints and
5205 watchpoints it needs to insert.
5207 When this message is printed, you need to disable or remove some of the
5208 hardware-assisted breakpoints and watchpoints, and then continue.
5210 @node Breakpoint-related Warnings
5211 @subsection ``Breakpoint address adjusted...''
5212 @cindex breakpoint address adjusted
5214 Some processor architectures place constraints on the addresses at
5215 which breakpoints may be placed. For architectures thus constrained,
5216 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5217 with the constraints dictated by the architecture.
5219 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5220 a VLIW architecture in which a number of RISC-like instructions may be
5221 bundled together for parallel execution. The FR-V architecture
5222 constrains the location of a breakpoint instruction within such a
5223 bundle to the instruction with the lowest address. @value{GDBN}
5224 honors this constraint by adjusting a breakpoint's address to the
5225 first in the bundle.
5227 It is not uncommon for optimized code to have bundles which contain
5228 instructions from different source statements, thus it may happen that
5229 a breakpoint's address will be adjusted from one source statement to
5230 another. Since this adjustment may significantly alter @value{GDBN}'s
5231 breakpoint related behavior from what the user expects, a warning is
5232 printed when the breakpoint is first set and also when the breakpoint
5235 A warning like the one below is printed when setting a breakpoint
5236 that's been subject to address adjustment:
5239 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5242 Such warnings are printed both for user settable and @value{GDBN}'s
5243 internal breakpoints. If you see one of these warnings, you should
5244 verify that a breakpoint set at the adjusted address will have the
5245 desired affect. If not, the breakpoint in question may be removed and
5246 other breakpoints may be set which will have the desired behavior.
5247 E.g., it may be sufficient to place the breakpoint at a later
5248 instruction. A conditional breakpoint may also be useful in some
5249 cases to prevent the breakpoint from triggering too often.
5251 @value{GDBN} will also issue a warning when stopping at one of these
5252 adjusted breakpoints:
5255 warning: Breakpoint 1 address previously adjusted from 0x00010414
5259 When this warning is encountered, it may be too late to take remedial
5260 action except in cases where the breakpoint is hit earlier or more
5261 frequently than expected.
5263 @node Continuing and Stepping
5264 @section Continuing and Stepping
5268 @cindex resuming execution
5269 @dfn{Continuing} means resuming program execution until your program
5270 completes normally. In contrast, @dfn{stepping} means executing just
5271 one more ``step'' of your program, where ``step'' may mean either one
5272 line of source code, or one machine instruction (depending on what
5273 particular command you use). Either when continuing or when stepping,
5274 your program may stop even sooner, due to a breakpoint or a signal. (If
5275 it stops due to a signal, you may want to use @code{handle}, or use
5276 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5277 or you may step into the signal's handler (@pxref{stepping and signal
5282 @kindex c @r{(@code{continue})}
5283 @kindex fg @r{(resume foreground execution)}
5284 @item continue @r{[}@var{ignore-count}@r{]}
5285 @itemx c @r{[}@var{ignore-count}@r{]}
5286 @itemx fg @r{[}@var{ignore-count}@r{]}
5287 Resume program execution, at the address where your program last stopped;
5288 any breakpoints set at that address are bypassed. The optional argument
5289 @var{ignore-count} allows you to specify a further number of times to
5290 ignore a breakpoint at this location; its effect is like that of
5291 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5293 The argument @var{ignore-count} is meaningful only when your program
5294 stopped due to a breakpoint. At other times, the argument to
5295 @code{continue} is ignored.
5297 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5298 debugged program is deemed to be the foreground program) are provided
5299 purely for convenience, and have exactly the same behavior as
5303 To resume execution at a different place, you can use @code{return}
5304 (@pxref{Returning, ,Returning from a Function}) to go back to the
5305 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5306 Different Address}) to go to an arbitrary location in your program.
5308 A typical technique for using stepping is to set a breakpoint
5309 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5310 beginning of the function or the section of your program where a problem
5311 is believed to lie, run your program until it stops at that breakpoint,
5312 and then step through the suspect area, examining the variables that are
5313 interesting, until you see the problem happen.
5317 @kindex s @r{(@code{step})}
5319 Continue running your program until control reaches a different source
5320 line, then stop it and return control to @value{GDBN}. This command is
5321 abbreviated @code{s}.
5324 @c "without debugging information" is imprecise; actually "without line
5325 @c numbers in the debugging information". (gcc -g1 has debugging info but
5326 @c not line numbers). But it seems complex to try to make that
5327 @c distinction here.
5328 @emph{Warning:} If you use the @code{step} command while control is
5329 within a function that was compiled without debugging information,
5330 execution proceeds until control reaches a function that does have
5331 debugging information. Likewise, it will not step into a function which
5332 is compiled without debugging information. To step through functions
5333 without debugging information, use the @code{stepi} command, described
5337 The @code{step} command only stops at the first instruction of a source
5338 line. This prevents the multiple stops that could otherwise occur in
5339 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5340 to stop if a function that has debugging information is called within
5341 the line. In other words, @code{step} @emph{steps inside} any functions
5342 called within the line.
5344 Also, the @code{step} command only enters a function if there is line
5345 number information for the function. Otherwise it acts like the
5346 @code{next} command. This avoids problems when using @code{cc -gl}
5347 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5348 was any debugging information about the routine.
5350 @item step @var{count}
5351 Continue running as in @code{step}, but do so @var{count} times. If a
5352 breakpoint is reached, or a signal not related to stepping occurs before
5353 @var{count} steps, stepping stops right away.
5356 @kindex n @r{(@code{next})}
5357 @item next @r{[}@var{count}@r{]}
5358 Continue to the next source line in the current (innermost) stack frame.
5359 This is similar to @code{step}, but function calls that appear within
5360 the line of code are executed without stopping. Execution stops when
5361 control reaches a different line of code at the original stack level
5362 that was executing when you gave the @code{next} command. This command
5363 is abbreviated @code{n}.
5365 An argument @var{count} is a repeat count, as for @code{step}.
5368 @c FIX ME!! Do we delete this, or is there a way it fits in with
5369 @c the following paragraph? --- Vctoria
5371 @c @code{next} within a function that lacks debugging information acts like
5372 @c @code{step}, but any function calls appearing within the code of the
5373 @c function are executed without stopping.
5375 The @code{next} command only stops at the first instruction of a
5376 source line. This prevents multiple stops that could otherwise occur in
5377 @code{switch} statements, @code{for} loops, etc.
5379 @kindex set step-mode
5381 @cindex functions without line info, and stepping
5382 @cindex stepping into functions with no line info
5383 @itemx set step-mode on
5384 The @code{set step-mode on} command causes the @code{step} command to
5385 stop at the first instruction of a function which contains no debug line
5386 information rather than stepping over it.
5388 This is useful in cases where you may be interested in inspecting the
5389 machine instructions of a function which has no symbolic info and do not
5390 want @value{GDBN} to automatically skip over this function.
5392 @item set step-mode off
5393 Causes the @code{step} command to step over any functions which contains no
5394 debug information. This is the default.
5396 @item show step-mode
5397 Show whether @value{GDBN} will stop in or step over functions without
5398 source line debug information.
5401 @kindex fin @r{(@code{finish})}
5403 Continue running until just after function in the selected stack frame
5404 returns. Print the returned value (if any). This command can be
5405 abbreviated as @code{fin}.
5407 Contrast this with the @code{return} command (@pxref{Returning,
5408 ,Returning from a Function}).
5411 @kindex u @r{(@code{until})}
5412 @cindex run until specified location
5415 Continue running until a source line past the current line, in the
5416 current stack frame, is reached. This command is used to avoid single
5417 stepping through a loop more than once. It is like the @code{next}
5418 command, except that when @code{until} encounters a jump, it
5419 automatically continues execution until the program counter is greater
5420 than the address of the jump.
5422 This means that when you reach the end of a loop after single stepping
5423 though it, @code{until} makes your program continue execution until it
5424 exits the loop. In contrast, a @code{next} command at the end of a loop
5425 simply steps back to the beginning of the loop, which forces you to step
5426 through the next iteration.
5428 @code{until} always stops your program if it attempts to exit the current
5431 @code{until} may produce somewhat counterintuitive results if the order
5432 of machine code does not match the order of the source lines. For
5433 example, in the following excerpt from a debugging session, the @code{f}
5434 (@code{frame}) command shows that execution is stopped at line
5435 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5439 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5441 (@value{GDBP}) until
5442 195 for ( ; argc > 0; NEXTARG) @{
5445 This happened because, for execution efficiency, the compiler had
5446 generated code for the loop closure test at the end, rather than the
5447 start, of the loop---even though the test in a C @code{for}-loop is
5448 written before the body of the loop. The @code{until} command appeared
5449 to step back to the beginning of the loop when it advanced to this
5450 expression; however, it has not really gone to an earlier
5451 statement---not in terms of the actual machine code.
5453 @code{until} with no argument works by means of single
5454 instruction stepping, and hence is slower than @code{until} with an
5457 @item until @var{location}
5458 @itemx u @var{location}
5459 Continue running your program until either the specified @var{location} is
5460 reached, or the current stack frame returns. The location is any of
5461 the forms described in @ref{Specify Location}.
5462 This form of the command uses temporary breakpoints, and
5463 hence is quicker than @code{until} without an argument. The specified
5464 location is actually reached only if it is in the current frame. This
5465 implies that @code{until} can be used to skip over recursive function
5466 invocations. For instance in the code below, if the current location is
5467 line @code{96}, issuing @code{until 99} will execute the program up to
5468 line @code{99} in the same invocation of factorial, i.e., after the inner
5469 invocations have returned.
5472 94 int factorial (int value)
5474 96 if (value > 1) @{
5475 97 value *= factorial (value - 1);
5482 @kindex advance @var{location}
5483 @item advance @var{location}
5484 Continue running the program up to the given @var{location}. An argument is
5485 required, which should be of one of the forms described in
5486 @ref{Specify Location}.
5487 Execution will also stop upon exit from the current stack
5488 frame. This command is similar to @code{until}, but @code{advance} will
5489 not skip over recursive function calls, and the target location doesn't
5490 have to be in the same frame as the current one.
5494 @kindex si @r{(@code{stepi})}
5496 @itemx stepi @var{arg}
5498 Execute one machine instruction, then stop and return to the debugger.
5500 It is often useful to do @samp{display/i $pc} when stepping by machine
5501 instructions. This makes @value{GDBN} automatically display the next
5502 instruction to be executed, each time your program stops. @xref{Auto
5503 Display,, Automatic Display}.
5505 An argument is a repeat count, as in @code{step}.
5509 @kindex ni @r{(@code{nexti})}
5511 @itemx nexti @var{arg}
5513 Execute one machine instruction, but if it is a function call,
5514 proceed until the function returns.
5516 An argument is a repeat count, as in @code{next}.
5520 @anchor{range stepping}
5521 @cindex range stepping
5522 @cindex target-assisted range stepping
5523 By default, and if available, @value{GDBN} makes use of
5524 target-assisted @dfn{range stepping}. In other words, whenever you
5525 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5526 tells the target to step the corresponding range of instruction
5527 addresses instead of issuing multiple single-steps. This speeds up
5528 line stepping, particularly for remote targets. Ideally, there should
5529 be no reason you would want to turn range stepping off. However, it's
5530 possible that a bug in the debug info, a bug in the remote stub (for
5531 remote targets), or even a bug in @value{GDBN} could make line
5532 stepping behave incorrectly when target-assisted range stepping is
5533 enabled. You can use the following command to turn off range stepping
5537 @kindex set range-stepping
5538 @kindex show range-stepping
5539 @item set range-stepping
5540 @itemx show range-stepping
5541 Control whether range stepping is enabled.
5543 If @code{on}, and the target supports it, @value{GDBN} tells the
5544 target to step a range of addresses itself, instead of issuing
5545 multiple single-steps. If @code{off}, @value{GDBN} always issues
5546 single-steps, even if range stepping is supported by the target. The
5547 default is @code{on}.
5551 @node Skipping Over Functions and Files
5552 @section Skipping Over Functions and Files
5553 @cindex skipping over functions and files
5555 The program you are debugging may contain some functions which are
5556 uninteresting to debug. The @code{skip} command lets you tell @value{GDBN} to
5557 skip a function, all functions in a file or a particular function in
5558 a particular file when stepping.
5560 For example, consider the following C function:
5571 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5572 are not interested in stepping through @code{boring}. If you run @code{step}
5573 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5574 step over both @code{foo} and @code{boring}!
5576 One solution is to @code{step} into @code{boring} and use the @code{finish}
5577 command to immediately exit it. But this can become tedious if @code{boring}
5578 is called from many places.
5580 A more flexible solution is to execute @kbd{skip boring}. This instructs
5581 @value{GDBN} never to step into @code{boring}. Now when you execute
5582 @code{step} at line 103, you'll step over @code{boring} and directly into
5585 Functions may be skipped by providing either a function name, linespec
5586 (@pxref{Specify Location}), regular expression that matches the function's
5587 name, file name or a @code{glob}-style pattern that matches the file name.
5589 On Posix systems the form of the regular expression is
5590 ``Extended Regular Expressions''. See for example @samp{man 7 regex}
5591 on @sc{gnu}/Linux systems. On non-Posix systems the form of the regular
5592 expression is whatever is provided by the @code{regcomp} function of
5593 the underlying system.
5594 See for example @samp{man 7 glob} on @sc{gnu}/Linux systems for a
5595 description of @code{glob}-style patterns.
5599 @item skip @r{[}@var{options}@r{]}
5600 The basic form of the @code{skip} command takes zero or more options
5601 that specify what to skip.
5602 The @var{options} argument is any useful combination of the following:
5605 @item -file @var{file}
5606 @itemx -fi @var{file}
5607 Functions in @var{file} will be skipped over when stepping.
5609 @item -gfile @var{file-glob-pattern}
5610 @itemx -gfi @var{file-glob-pattern}
5611 @cindex skipping over files via glob-style patterns
5612 Functions in files matching @var{file-glob-pattern} will be skipped
5616 (gdb) skip -gfi utils/*.c
5619 @item -function @var{linespec}
5620 @itemx -fu @var{linespec}
5621 Functions named by @var{linespec} or the function containing the line
5622 named by @var{linespec} will be skipped over when stepping.
5623 @xref{Specify Location}.
5625 @item -rfunction @var{regexp}
5626 @itemx -rfu @var{regexp}
5627 @cindex skipping over functions via regular expressions
5628 Functions whose name matches @var{regexp} will be skipped over when stepping.
5630 This form is useful for complex function names.
5631 For example, there is generally no need to step into C@t{++} @code{std::string}
5632 constructors or destructors. Plus with C@t{++} templates it can be hard to
5633 write out the full name of the function, and often it doesn't matter what
5634 the template arguments are. Specifying the function to be skipped as a
5635 regular expression makes this easier.
5638 (gdb) skip -rfu ^std::(allocator|basic_string)<.*>::~?\1 *\(
5641 If you want to skip every templated C@t{++} constructor and destructor
5642 in the @code{std} namespace you can do:
5645 (gdb) skip -rfu ^std::([a-zA-z0-9_]+)<.*>::~?\1 *\(
5649 If no options are specified, the function you're currently debugging
5652 @kindex skip function
5653 @item skip function @r{[}@var{linespec}@r{]}
5654 After running this command, the function named by @var{linespec} or the
5655 function containing the line named by @var{linespec} will be skipped over when
5656 stepping. @xref{Specify Location}.
5658 If you do not specify @var{linespec}, the function you're currently debugging
5661 (If you have a function called @code{file} that you want to skip, use
5662 @kbd{skip function file}.)
5665 @item skip file @r{[}@var{filename}@r{]}
5666 After running this command, any function whose source lives in @var{filename}
5667 will be skipped over when stepping.
5670 (gdb) skip file boring.c
5671 File boring.c will be skipped when stepping.
5674 If you do not specify @var{filename}, functions whose source lives in the file
5675 you're currently debugging will be skipped.
5678 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5679 These are the commands for managing your list of skips:
5683 @item info skip @r{[}@var{range}@r{]}
5684 Print details about the specified skip(s). If @var{range} is not specified,
5685 print a table with details about all functions and files marked for skipping.
5686 @code{info skip} prints the following information about each skip:
5690 A number identifying this skip.
5691 @item Enabled or Disabled
5692 Enabled skips are marked with @samp{y}.
5693 Disabled skips are marked with @samp{n}.
5695 If the file name is a @samp{glob} pattern this is @samp{y}.
5696 Otherwise it is @samp{n}.
5698 The name or @samp{glob} pattern of the file to be skipped.
5699 If no file is specified this is @samp{<none>}.
5701 If the function name is a @samp{regular expression} this is @samp{y}.
5702 Otherwise it is @samp{n}.
5704 The name or regular expression of the function to skip.
5705 If no function is specified this is @samp{<none>}.
5709 @item skip delete @r{[}@var{range}@r{]}
5710 Delete the specified skip(s). If @var{range} is not specified, delete all
5714 @item skip enable @r{[}@var{range}@r{]}
5715 Enable the specified skip(s). If @var{range} is not specified, enable all
5718 @kindex skip disable
5719 @item skip disable @r{[}@var{range}@r{]}
5720 Disable the specified skip(s). If @var{range} is not specified, disable all
5729 A signal is an asynchronous event that can happen in a program. The
5730 operating system defines the possible kinds of signals, and gives each
5731 kind a name and a number. For example, in Unix @code{SIGINT} is the
5732 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5733 @code{SIGSEGV} is the signal a program gets from referencing a place in
5734 memory far away from all the areas in use; @code{SIGALRM} occurs when
5735 the alarm clock timer goes off (which happens only if your program has
5736 requested an alarm).
5738 @cindex fatal signals
5739 Some signals, including @code{SIGALRM}, are a normal part of the
5740 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5741 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5742 program has not specified in advance some other way to handle the signal.
5743 @code{SIGINT} does not indicate an error in your program, but it is normally
5744 fatal so it can carry out the purpose of the interrupt: to kill the program.
5746 @value{GDBN} has the ability to detect any occurrence of a signal in your
5747 program. You can tell @value{GDBN} in advance what to do for each kind of
5750 @cindex handling signals
5751 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5752 @code{SIGALRM} be silently passed to your program
5753 (so as not to interfere with their role in the program's functioning)
5754 but to stop your program immediately whenever an error signal happens.
5755 You can change these settings with the @code{handle} command.
5758 @kindex info signals
5762 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5763 handle each one. You can use this to see the signal numbers of all
5764 the defined types of signals.
5766 @item info signals @var{sig}
5767 Similar, but print information only about the specified signal number.
5769 @code{info handle} is an alias for @code{info signals}.
5771 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5772 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5773 for details about this command.
5776 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5777 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
5778 can be the number of a signal or its name (with or without the
5779 @samp{SIG} at the beginning); a list of signal numbers of the form
5780 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5781 known signals. Optional arguments @var{keywords}, described below,
5782 say what change to make.
5786 The keywords allowed by the @code{handle} command can be abbreviated.
5787 Their full names are:
5791 @value{GDBN} should not stop your program when this signal happens. It may
5792 still print a message telling you that the signal has come in.
5795 @value{GDBN} should stop your program when this signal happens. This implies
5796 the @code{print} keyword as well.
5799 @value{GDBN} should print a message when this signal happens.
5802 @value{GDBN} should not mention the occurrence of the signal at all. This
5803 implies the @code{nostop} keyword as well.
5807 @value{GDBN} should allow your program to see this signal; your program
5808 can handle the signal, or else it may terminate if the signal is fatal
5809 and not handled. @code{pass} and @code{noignore} are synonyms.
5813 @value{GDBN} should not allow your program to see this signal.
5814 @code{nopass} and @code{ignore} are synonyms.
5818 When a signal stops your program, the signal is not visible to the
5820 continue. Your program sees the signal then, if @code{pass} is in
5821 effect for the signal in question @emph{at that time}. In other words,
5822 after @value{GDBN} reports a signal, you can use the @code{handle}
5823 command with @code{pass} or @code{nopass} to control whether your
5824 program sees that signal when you continue.
5826 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5827 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5828 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5831 You can also use the @code{signal} command to prevent your program from
5832 seeing a signal, or cause it to see a signal it normally would not see,
5833 or to give it any signal at any time. For example, if your program stopped
5834 due to some sort of memory reference error, you might store correct
5835 values into the erroneous variables and continue, hoping to see more
5836 execution; but your program would probably terminate immediately as
5837 a result of the fatal signal once it saw the signal. To prevent this,
5838 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5841 @cindex stepping and signal handlers
5842 @anchor{stepping and signal handlers}
5844 @value{GDBN} optimizes for stepping the mainline code. If a signal
5845 that has @code{handle nostop} and @code{handle pass} set arrives while
5846 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
5847 in progress, @value{GDBN} lets the signal handler run and then resumes
5848 stepping the mainline code once the signal handler returns. In other
5849 words, @value{GDBN} steps over the signal handler. This prevents
5850 signals that you've specified as not interesting (with @code{handle
5851 nostop}) from changing the focus of debugging unexpectedly. Note that
5852 the signal handler itself may still hit a breakpoint, stop for another
5853 signal that has @code{handle stop} in effect, or for any other event
5854 that normally results in stopping the stepping command sooner. Also
5855 note that @value{GDBN} still informs you that the program received a
5856 signal if @code{handle print} is set.
5858 @anchor{stepping into signal handlers}
5860 If you set @code{handle pass} for a signal, and your program sets up a
5861 handler for it, then issuing a stepping command, such as @code{step}
5862 or @code{stepi}, when your program is stopped due to the signal will
5863 step @emph{into} the signal handler (if the target supports that).
5865 Likewise, if you use the @code{queue-signal} command to queue a signal
5866 to be delivered to the current thread when execution of the thread
5867 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
5868 stepping command will step into the signal handler.
5870 Here's an example, using @code{stepi} to step to the first instruction
5871 of @code{SIGUSR1}'s handler:
5874 (@value{GDBP}) handle SIGUSR1
5875 Signal Stop Print Pass to program Description
5876 SIGUSR1 Yes Yes Yes User defined signal 1
5880 Program received signal SIGUSR1, User defined signal 1.
5881 main () sigusr1.c:28
5884 sigusr1_handler () at sigusr1.c:9
5888 The same, but using @code{queue-signal} instead of waiting for the
5889 program to receive the signal first:
5894 (@value{GDBP}) queue-signal SIGUSR1
5896 sigusr1_handler () at sigusr1.c:9
5901 @cindex extra signal information
5902 @anchor{extra signal information}
5904 On some targets, @value{GDBN} can inspect extra signal information
5905 associated with the intercepted signal, before it is actually
5906 delivered to the program being debugged. This information is exported
5907 by the convenience variable @code{$_siginfo}, and consists of data
5908 that is passed by the kernel to the signal handler at the time of the
5909 receipt of a signal. The data type of the information itself is
5910 target dependent. You can see the data type using the @code{ptype
5911 $_siginfo} command. On Unix systems, it typically corresponds to the
5912 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5915 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5916 referenced address that raised a segmentation fault.
5920 (@value{GDBP}) continue
5921 Program received signal SIGSEGV, Segmentation fault.
5922 0x0000000000400766 in main ()
5924 (@value{GDBP}) ptype $_siginfo
5931 struct @{...@} _kill;
5932 struct @{...@} _timer;
5934 struct @{...@} _sigchld;
5935 struct @{...@} _sigfault;
5936 struct @{...@} _sigpoll;
5939 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5943 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5944 $1 = (void *) 0x7ffff7ff7000
5948 Depending on target support, @code{$_siginfo} may also be writable.
5950 @cindex Intel MPX boundary violations
5951 @cindex boundary violations, Intel MPX
5952 On some targets, a @code{SIGSEGV} can be caused by a boundary
5953 violation, i.e., accessing an address outside of the allowed range.
5954 In those cases @value{GDBN} may displays additional information,
5955 depending on how @value{GDBN} has been told to handle the signal.
5956 With @code{handle stop SIGSEGV}, @value{GDBN} displays the violation
5957 kind: "Upper" or "Lower", the memory address accessed and the
5958 bounds, while with @code{handle nostop SIGSEGV} no additional
5959 information is displayed.
5961 The usual output of a segfault is:
5963 Program received signal SIGSEGV, Segmentation fault
5964 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
5965 68 value = *(p + len);
5968 While a bound violation is presented as:
5970 Program received signal SIGSEGV, Segmentation fault
5971 Upper bound violation while accessing address 0x7fffffffc3b3
5972 Bounds: [lower = 0x7fffffffc390, upper = 0x7fffffffc3a3]
5973 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
5974 68 value = *(p + len);
5978 @section Stopping and Starting Multi-thread Programs
5980 @cindex stopped threads
5981 @cindex threads, stopped
5983 @cindex continuing threads
5984 @cindex threads, continuing
5986 @value{GDBN} supports debugging programs with multiple threads
5987 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5988 are two modes of controlling execution of your program within the
5989 debugger. In the default mode, referred to as @dfn{all-stop mode},
5990 when any thread in your program stops (for example, at a breakpoint
5991 or while being stepped), all other threads in the program are also stopped by
5992 @value{GDBN}. On some targets, @value{GDBN} also supports
5993 @dfn{non-stop mode}, in which other threads can continue to run freely while
5994 you examine the stopped thread in the debugger.
5997 * All-Stop Mode:: All threads stop when GDB takes control
5998 * Non-Stop Mode:: Other threads continue to execute
5999 * Background Execution:: Running your program asynchronously
6000 * Thread-Specific Breakpoints:: Controlling breakpoints
6001 * Interrupted System Calls:: GDB may interfere with system calls
6002 * Observer Mode:: GDB does not alter program behavior
6006 @subsection All-Stop Mode
6008 @cindex all-stop mode
6010 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
6011 @emph{all} threads of execution stop, not just the current thread. This
6012 allows you to examine the overall state of the program, including
6013 switching between threads, without worrying that things may change
6016 Conversely, whenever you restart the program, @emph{all} threads start
6017 executing. @emph{This is true even when single-stepping} with commands
6018 like @code{step} or @code{next}.
6020 In particular, @value{GDBN} cannot single-step all threads in lockstep.
6021 Since thread scheduling is up to your debugging target's operating
6022 system (not controlled by @value{GDBN}), other threads may
6023 execute more than one statement while the current thread completes a
6024 single step. Moreover, in general other threads stop in the middle of a
6025 statement, rather than at a clean statement boundary, when the program
6028 You might even find your program stopped in another thread after
6029 continuing or even single-stepping. This happens whenever some other
6030 thread runs into a breakpoint, a signal, or an exception before the
6031 first thread completes whatever you requested.
6033 @cindex automatic thread selection
6034 @cindex switching threads automatically
6035 @cindex threads, automatic switching
6036 Whenever @value{GDBN} stops your program, due to a breakpoint or a
6037 signal, it automatically selects the thread where that breakpoint or
6038 signal happened. @value{GDBN} alerts you to the context switch with a
6039 message such as @samp{[Switching to Thread @var{n}]} to identify the
6042 On some OSes, you can modify @value{GDBN}'s default behavior by
6043 locking the OS scheduler to allow only a single thread to run.
6046 @item set scheduler-locking @var{mode}
6047 @cindex scheduler locking mode
6048 @cindex lock scheduler
6049 Set the scheduler locking mode. It applies to normal execution,
6050 record mode, and replay mode. If it is @code{off}, then there is no
6051 locking and any thread may run at any time. If @code{on}, then only
6052 the current thread may run when the inferior is resumed. The
6053 @code{step} mode optimizes for single-stepping; it prevents other
6054 threads from preempting the current thread while you are stepping, so
6055 that the focus of debugging does not change unexpectedly. Other
6056 threads never get a chance to run when you step, and they are
6057 completely free to run when you use commands like @samp{continue},
6058 @samp{until}, or @samp{finish}. However, unless another thread hits a
6059 breakpoint during its timeslice, @value{GDBN} does not change the
6060 current thread away from the thread that you are debugging. The
6061 @code{replay} mode behaves like @code{off} in record mode and like
6062 @code{on} in replay mode.
6064 @item show scheduler-locking
6065 Display the current scheduler locking mode.
6068 @cindex resume threads of multiple processes simultaneously
6069 By default, when you issue one of the execution commands such as
6070 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
6071 threads of the current inferior to run. For example, if @value{GDBN}
6072 is attached to two inferiors, each with two threads, the
6073 @code{continue} command resumes only the two threads of the current
6074 inferior. This is useful, for example, when you debug a program that
6075 forks and you want to hold the parent stopped (so that, for instance,
6076 it doesn't run to exit), while you debug the child. In other
6077 situations, you may not be interested in inspecting the current state
6078 of any of the processes @value{GDBN} is attached to, and you may want
6079 to resume them all until some breakpoint is hit. In the latter case,
6080 you can instruct @value{GDBN} to allow all threads of all the
6081 inferiors to run with the @w{@code{set schedule-multiple}} command.
6084 @kindex set schedule-multiple
6085 @item set schedule-multiple
6086 Set the mode for allowing threads of multiple processes to be resumed
6087 when an execution command is issued. When @code{on}, all threads of
6088 all processes are allowed to run. When @code{off}, only the threads
6089 of the current process are resumed. The default is @code{off}. The
6090 @code{scheduler-locking} mode takes precedence when set to @code{on},
6091 or while you are stepping and set to @code{step}.
6093 @item show schedule-multiple
6094 Display the current mode for resuming the execution of threads of
6099 @subsection Non-Stop Mode
6101 @cindex non-stop mode
6103 @c This section is really only a place-holder, and needs to be expanded
6104 @c with more details.
6106 For some multi-threaded targets, @value{GDBN} supports an optional
6107 mode of operation in which you can examine stopped program threads in
6108 the debugger while other threads continue to execute freely. This
6109 minimizes intrusion when debugging live systems, such as programs
6110 where some threads have real-time constraints or must continue to
6111 respond to external events. This is referred to as @dfn{non-stop} mode.
6113 In non-stop mode, when a thread stops to report a debugging event,
6114 @emph{only} that thread is stopped; @value{GDBN} does not stop other
6115 threads as well, in contrast to the all-stop mode behavior. Additionally,
6116 execution commands such as @code{continue} and @code{step} apply by default
6117 only to the current thread in non-stop mode, rather than all threads as
6118 in all-stop mode. This allows you to control threads explicitly in
6119 ways that are not possible in all-stop mode --- for example, stepping
6120 one thread while allowing others to run freely, stepping
6121 one thread while holding all others stopped, or stepping several threads
6122 independently and simultaneously.
6124 To enter non-stop mode, use this sequence of commands before you run
6125 or attach to your program:
6128 # If using the CLI, pagination breaks non-stop.
6131 # Finally, turn it on!
6135 You can use these commands to manipulate the non-stop mode setting:
6138 @kindex set non-stop
6139 @item set non-stop on
6140 Enable selection of non-stop mode.
6141 @item set non-stop off
6142 Disable selection of non-stop mode.
6143 @kindex show non-stop
6145 Show the current non-stop enablement setting.
6148 Note these commands only reflect whether non-stop mode is enabled,
6149 not whether the currently-executing program is being run in non-stop mode.
6150 In particular, the @code{set non-stop} preference is only consulted when
6151 @value{GDBN} starts or connects to the target program, and it is generally
6152 not possible to switch modes once debugging has started. Furthermore,
6153 since not all targets support non-stop mode, even when you have enabled
6154 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
6157 In non-stop mode, all execution commands apply only to the current thread
6158 by default. That is, @code{continue} only continues one thread.
6159 To continue all threads, issue @code{continue -a} or @code{c -a}.
6161 You can use @value{GDBN}'s background execution commands
6162 (@pxref{Background Execution}) to run some threads in the background
6163 while you continue to examine or step others from @value{GDBN}.
6164 The MI execution commands (@pxref{GDB/MI Program Execution}) are
6165 always executed asynchronously in non-stop mode.
6167 Suspending execution is done with the @code{interrupt} command when
6168 running in the background, or @kbd{Ctrl-c} during foreground execution.
6169 In all-stop mode, this stops the whole process;
6170 but in non-stop mode the interrupt applies only to the current thread.
6171 To stop the whole program, use @code{interrupt -a}.
6173 Other execution commands do not currently support the @code{-a} option.
6175 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
6176 that thread current, as it does in all-stop mode. This is because the
6177 thread stop notifications are asynchronous with respect to @value{GDBN}'s
6178 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
6179 changed to a different thread just as you entered a command to operate on the
6180 previously current thread.
6182 @node Background Execution
6183 @subsection Background Execution
6185 @cindex foreground execution
6186 @cindex background execution
6187 @cindex asynchronous execution
6188 @cindex execution, foreground, background and asynchronous
6190 @value{GDBN}'s execution commands have two variants: the normal
6191 foreground (synchronous) behavior, and a background
6192 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
6193 the program to report that some thread has stopped before prompting for
6194 another command. In background execution, @value{GDBN} immediately gives
6195 a command prompt so that you can issue other commands while your program runs.
6197 If the target doesn't support async mode, @value{GDBN} issues an error
6198 message if you attempt to use the background execution commands.
6200 To specify background execution, add a @code{&} to the command. For example,
6201 the background form of the @code{continue} command is @code{continue&}, or
6202 just @code{c&}. The execution commands that accept background execution
6208 @xref{Starting, , Starting your Program}.
6212 @xref{Attach, , Debugging an Already-running Process}.
6216 @xref{Continuing and Stepping, step}.
6220 @xref{Continuing and Stepping, stepi}.
6224 @xref{Continuing and Stepping, next}.
6228 @xref{Continuing and Stepping, nexti}.
6232 @xref{Continuing and Stepping, continue}.
6236 @xref{Continuing and Stepping, finish}.
6240 @xref{Continuing and Stepping, until}.
6244 Background execution is especially useful in conjunction with non-stop
6245 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
6246 However, you can also use these commands in the normal all-stop mode with
6247 the restriction that you cannot issue another execution command until the
6248 previous one finishes. Examples of commands that are valid in all-stop
6249 mode while the program is running include @code{help} and @code{info break}.
6251 You can interrupt your program while it is running in the background by
6252 using the @code{interrupt} command.
6259 Suspend execution of the running program. In all-stop mode,
6260 @code{interrupt} stops the whole process, but in non-stop mode, it stops
6261 only the current thread. To stop the whole program in non-stop mode,
6262 use @code{interrupt -a}.
6265 @node Thread-Specific Breakpoints
6266 @subsection Thread-Specific Breakpoints
6268 When your program has multiple threads (@pxref{Threads,, Debugging
6269 Programs with Multiple Threads}), you can choose whether to set
6270 breakpoints on all threads, or on a particular thread.
6273 @cindex breakpoints and threads
6274 @cindex thread breakpoints
6275 @kindex break @dots{} thread @var{thread-id}
6276 @item break @var{location} thread @var{thread-id}
6277 @itemx break @var{location} thread @var{thread-id} if @dots{}
6278 @var{location} specifies source lines; there are several ways of
6279 writing them (@pxref{Specify Location}), but the effect is always to
6280 specify some source line.
6282 Use the qualifier @samp{thread @var{thread-id}} with a breakpoint command
6283 to specify that you only want @value{GDBN} to stop the program when a
6284 particular thread reaches this breakpoint. The @var{thread-id} specifier
6285 is one of the thread identifiers assigned by @value{GDBN}, shown
6286 in the first column of the @samp{info threads} display.
6288 If you do not specify @samp{thread @var{thread-id}} when you set a
6289 breakpoint, the breakpoint applies to @emph{all} threads of your
6292 You can use the @code{thread} qualifier on conditional breakpoints as
6293 well; in this case, place @samp{thread @var{thread-id}} before or
6294 after the breakpoint condition, like this:
6297 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6302 Thread-specific breakpoints are automatically deleted when
6303 @value{GDBN} detects the corresponding thread is no longer in the
6304 thread list. For example:
6308 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6311 There are several ways for a thread to disappear, such as a regular
6312 thread exit, but also when you detach from the process with the
6313 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6314 Process}), or if @value{GDBN} loses the remote connection
6315 (@pxref{Remote Debugging}), etc. Note that with some targets,
6316 @value{GDBN} is only able to detect a thread has exited when the user
6317 explictly asks for the thread list with the @code{info threads}
6320 @node Interrupted System Calls
6321 @subsection Interrupted System Calls
6323 @cindex thread breakpoints and system calls
6324 @cindex system calls and thread breakpoints
6325 @cindex premature return from system calls
6326 There is an unfortunate side effect when using @value{GDBN} to debug
6327 multi-threaded programs. If one thread stops for a
6328 breakpoint, or for some other reason, and another thread is blocked in a
6329 system call, then the system call may return prematurely. This is a
6330 consequence of the interaction between multiple threads and the signals
6331 that @value{GDBN} uses to implement breakpoints and other events that
6334 To handle this problem, your program should check the return value of
6335 each system call and react appropriately. This is good programming
6338 For example, do not write code like this:
6344 The call to @code{sleep} will return early if a different thread stops
6345 at a breakpoint or for some other reason.
6347 Instead, write this:
6352 unslept = sleep (unslept);
6355 A system call is allowed to return early, so the system is still
6356 conforming to its specification. But @value{GDBN} does cause your
6357 multi-threaded program to behave differently than it would without
6360 Also, @value{GDBN} uses internal breakpoints in the thread library to
6361 monitor certain events such as thread creation and thread destruction.
6362 When such an event happens, a system call in another thread may return
6363 prematurely, even though your program does not appear to stop.
6366 @subsection Observer Mode
6368 If you want to build on non-stop mode and observe program behavior
6369 without any chance of disruption by @value{GDBN}, you can set
6370 variables to disable all of the debugger's attempts to modify state,
6371 whether by writing memory, inserting breakpoints, etc. These operate
6372 at a low level, intercepting operations from all commands.
6374 When all of these are set to @code{off}, then @value{GDBN} is said to
6375 be @dfn{observer mode}. As a convenience, the variable
6376 @code{observer} can be set to disable these, plus enable non-stop
6379 Note that @value{GDBN} will not prevent you from making nonsensical
6380 combinations of these settings. For instance, if you have enabled
6381 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6382 then breakpoints that work by writing trap instructions into the code
6383 stream will still not be able to be placed.
6388 @item set observer on
6389 @itemx set observer off
6390 When set to @code{on}, this disables all the permission variables
6391 below (except for @code{insert-fast-tracepoints}), plus enables
6392 non-stop debugging. Setting this to @code{off} switches back to
6393 normal debugging, though remaining in non-stop mode.
6396 Show whether observer mode is on or off.
6398 @kindex may-write-registers
6399 @item set may-write-registers on
6400 @itemx set may-write-registers off
6401 This controls whether @value{GDBN} will attempt to alter the values of
6402 registers, such as with assignment expressions in @code{print}, or the
6403 @code{jump} command. It defaults to @code{on}.
6405 @item show may-write-registers
6406 Show the current permission to write registers.
6408 @kindex may-write-memory
6409 @item set may-write-memory on
6410 @itemx set may-write-memory off
6411 This controls whether @value{GDBN} will attempt to alter the contents
6412 of memory, such as with assignment expressions in @code{print}. It
6413 defaults to @code{on}.
6415 @item show may-write-memory
6416 Show the current permission to write memory.
6418 @kindex may-insert-breakpoints
6419 @item set may-insert-breakpoints on
6420 @itemx set may-insert-breakpoints off
6421 This controls whether @value{GDBN} will attempt to insert breakpoints.
6422 This affects all breakpoints, including internal breakpoints defined
6423 by @value{GDBN}. It defaults to @code{on}.
6425 @item show may-insert-breakpoints
6426 Show the current permission to insert breakpoints.
6428 @kindex may-insert-tracepoints
6429 @item set may-insert-tracepoints on
6430 @itemx set may-insert-tracepoints off
6431 This controls whether @value{GDBN} will attempt to insert (regular)
6432 tracepoints at the beginning of a tracing experiment. It affects only
6433 non-fast tracepoints, fast tracepoints being under the control of
6434 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6436 @item show may-insert-tracepoints
6437 Show the current permission to insert tracepoints.
6439 @kindex may-insert-fast-tracepoints
6440 @item set may-insert-fast-tracepoints on
6441 @itemx set may-insert-fast-tracepoints off
6442 This controls whether @value{GDBN} will attempt to insert fast
6443 tracepoints at the beginning of a tracing experiment. It affects only
6444 fast tracepoints, regular (non-fast) tracepoints being under the
6445 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6447 @item show may-insert-fast-tracepoints
6448 Show the current permission to insert fast tracepoints.
6450 @kindex may-interrupt
6451 @item set may-interrupt on
6452 @itemx set may-interrupt off
6453 This controls whether @value{GDBN} will attempt to interrupt or stop
6454 program execution. When this variable is @code{off}, the
6455 @code{interrupt} command will have no effect, nor will
6456 @kbd{Ctrl-c}. It defaults to @code{on}.
6458 @item show may-interrupt
6459 Show the current permission to interrupt or stop the program.
6463 @node Reverse Execution
6464 @chapter Running programs backward
6465 @cindex reverse execution
6466 @cindex running programs backward
6468 When you are debugging a program, it is not unusual to realize that
6469 you have gone too far, and some event of interest has already happened.
6470 If the target environment supports it, @value{GDBN} can allow you to
6471 ``rewind'' the program by running it backward.
6473 A target environment that supports reverse execution should be able
6474 to ``undo'' the changes in machine state that have taken place as the
6475 program was executing normally. Variables, registers etc.@: should
6476 revert to their previous values. Obviously this requires a great
6477 deal of sophistication on the part of the target environment; not
6478 all target environments can support reverse execution.
6480 When a program is executed in reverse, the instructions that
6481 have most recently been executed are ``un-executed'', in reverse
6482 order. The program counter runs backward, following the previous
6483 thread of execution in reverse. As each instruction is ``un-executed'',
6484 the values of memory and/or registers that were changed by that
6485 instruction are reverted to their previous states. After executing
6486 a piece of source code in reverse, all side effects of that code
6487 should be ``undone'', and all variables should be returned to their
6488 prior values@footnote{
6489 Note that some side effects are easier to undo than others. For instance,
6490 memory and registers are relatively easy, but device I/O is hard. Some
6491 targets may be able undo things like device I/O, and some may not.
6493 The contract between @value{GDBN} and the reverse executing target
6494 requires only that the target do something reasonable when
6495 @value{GDBN} tells it to execute backwards, and then report the
6496 results back to @value{GDBN}. Whatever the target reports back to
6497 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6498 assumes that the memory and registers that the target reports are in a
6499 consistant state, but @value{GDBN} accepts whatever it is given.
6502 If you are debugging in a target environment that supports
6503 reverse execution, @value{GDBN} provides the following commands.
6506 @kindex reverse-continue
6507 @kindex rc @r{(@code{reverse-continue})}
6508 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6509 @itemx rc @r{[}@var{ignore-count}@r{]}
6510 Beginning at the point where your program last stopped, start executing
6511 in reverse. Reverse execution will stop for breakpoints and synchronous
6512 exceptions (signals), just like normal execution. Behavior of
6513 asynchronous signals depends on the target environment.
6515 @kindex reverse-step
6516 @kindex rs @r{(@code{step})}
6517 @item reverse-step @r{[}@var{count}@r{]}
6518 Run the program backward until control reaches the start of a
6519 different source line; then stop it, and return control to @value{GDBN}.
6521 Like the @code{step} command, @code{reverse-step} will only stop
6522 at the beginning of a source line. It ``un-executes'' the previously
6523 executed source line. If the previous source line included calls to
6524 debuggable functions, @code{reverse-step} will step (backward) into
6525 the called function, stopping at the beginning of the @emph{last}
6526 statement in the called function (typically a return statement).
6528 Also, as with the @code{step} command, if non-debuggable functions are
6529 called, @code{reverse-step} will run thru them backward without stopping.
6531 @kindex reverse-stepi
6532 @kindex rsi @r{(@code{reverse-stepi})}
6533 @item reverse-stepi @r{[}@var{count}@r{]}
6534 Reverse-execute one machine instruction. Note that the instruction
6535 to be reverse-executed is @emph{not} the one pointed to by the program
6536 counter, but the instruction executed prior to that one. For instance,
6537 if the last instruction was a jump, @code{reverse-stepi} will take you
6538 back from the destination of the jump to the jump instruction itself.
6540 @kindex reverse-next
6541 @kindex rn @r{(@code{reverse-next})}
6542 @item reverse-next @r{[}@var{count}@r{]}
6543 Run backward to the beginning of the previous line executed in
6544 the current (innermost) stack frame. If the line contains function
6545 calls, they will be ``un-executed'' without stopping. Starting from
6546 the first line of a function, @code{reverse-next} will take you back
6547 to the caller of that function, @emph{before} the function was called,
6548 just as the normal @code{next} command would take you from the last
6549 line of a function back to its return to its caller
6550 @footnote{Unless the code is too heavily optimized.}.
6552 @kindex reverse-nexti
6553 @kindex rni @r{(@code{reverse-nexti})}
6554 @item reverse-nexti @r{[}@var{count}@r{]}
6555 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6556 in reverse, except that called functions are ``un-executed'' atomically.
6557 That is, if the previously executed instruction was a return from
6558 another function, @code{reverse-nexti} will continue to execute
6559 in reverse until the call to that function (from the current stack
6562 @kindex reverse-finish
6563 @item reverse-finish
6564 Just as the @code{finish} command takes you to the point where the
6565 current function returns, @code{reverse-finish} takes you to the point
6566 where it was called. Instead of ending up at the end of the current
6567 function invocation, you end up at the beginning.
6569 @kindex set exec-direction
6570 @item set exec-direction
6571 Set the direction of target execution.
6572 @item set exec-direction reverse
6573 @cindex execute forward or backward in time
6574 @value{GDBN} will perform all execution commands in reverse, until the
6575 exec-direction mode is changed to ``forward''. Affected commands include
6576 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6577 command cannot be used in reverse mode.
6578 @item set exec-direction forward
6579 @value{GDBN} will perform all execution commands in the normal fashion.
6580 This is the default.
6584 @node Process Record and Replay
6585 @chapter Recording Inferior's Execution and Replaying It
6586 @cindex process record and replay
6587 @cindex recording inferior's execution and replaying it
6589 On some platforms, @value{GDBN} provides a special @dfn{process record
6590 and replay} target that can record a log of the process execution, and
6591 replay it later with both forward and reverse execution commands.
6594 When this target is in use, if the execution log includes the record
6595 for the next instruction, @value{GDBN} will debug in @dfn{replay
6596 mode}. In the replay mode, the inferior does not really execute code
6597 instructions. Instead, all the events that normally happen during
6598 code execution are taken from the execution log. While code is not
6599 really executed in replay mode, the values of registers (including the
6600 program counter register) and the memory of the inferior are still
6601 changed as they normally would. Their contents are taken from the
6605 If the record for the next instruction is not in the execution log,
6606 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6607 inferior executes normally, and @value{GDBN} records the execution log
6610 The process record and replay target supports reverse execution
6611 (@pxref{Reverse Execution}), even if the platform on which the
6612 inferior runs does not. However, the reverse execution is limited in
6613 this case by the range of the instructions recorded in the execution
6614 log. In other words, reverse execution on platforms that don't
6615 support it directly can only be done in the replay mode.
6617 When debugging in the reverse direction, @value{GDBN} will work in
6618 replay mode as long as the execution log includes the record for the
6619 previous instruction; otherwise, it will work in record mode, if the
6620 platform supports reverse execution, or stop if not.
6622 For architecture environments that support process record and replay,
6623 @value{GDBN} provides the following commands:
6626 @kindex target record
6627 @kindex target record-full
6628 @kindex target record-btrace
6631 @kindex record btrace
6632 @kindex record btrace bts
6633 @kindex record btrace pt
6639 @kindex rec btrace bts
6640 @kindex rec btrace pt
6643 @item record @var{method}
6644 This command starts the process record and replay target. The
6645 recording method can be specified as parameter. Without a parameter
6646 the command uses the @code{full} recording method. The following
6647 recording methods are available:
6651 Full record/replay recording using @value{GDBN}'s software record and
6652 replay implementation. This method allows replaying and reverse
6655 @item btrace @var{format}
6656 Hardware-supported instruction recording. This method does not record
6657 data. Further, the data is collected in a ring buffer so old data will
6658 be overwritten when the buffer is full. It allows limited reverse
6659 execution. Variables and registers are not available during reverse
6660 execution. In remote debugging, recording continues on disconnect.
6661 Recorded data can be inspected after reconnecting. The recording may
6662 be stopped using @code{record stop}.
6664 The recording format can be specified as parameter. Without a parameter
6665 the command chooses the recording format. The following recording
6666 formats are available:
6670 @cindex branch trace store
6671 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
6672 this format, the processor stores a from/to record for each executed
6673 branch in the btrace ring buffer.
6676 @cindex Intel Processor Trace
6677 Use the @dfn{Intel Processor Trace} recording format. In this
6678 format, the processor stores the execution trace in a compressed form
6679 that is afterwards decoded by @value{GDBN}.
6681 The trace can be recorded with very low overhead. The compressed
6682 trace format also allows small trace buffers to already contain a big
6683 number of instructions compared to @acronym{BTS}.
6685 Decoding the recorded execution trace, on the other hand, is more
6686 expensive than decoding @acronym{BTS} trace. This is mostly due to the
6687 increased number of instructions to process. You should increase the
6688 buffer-size with care.
6691 Not all recording formats may be available on all processors.
6694 The process record and replay target can only debug a process that is
6695 already running. Therefore, you need first to start the process with
6696 the @kbd{run} or @kbd{start} commands, and then start the recording
6697 with the @kbd{record @var{method}} command.
6699 @cindex displaced stepping, and process record and replay
6700 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6701 will be automatically disabled when process record and replay target
6702 is started. That's because the process record and replay target
6703 doesn't support displaced stepping.
6705 @cindex non-stop mode, and process record and replay
6706 @cindex asynchronous execution, and process record and replay
6707 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6708 the asynchronous execution mode (@pxref{Background Execution}), not
6709 all recording methods are available. The @code{full} recording method
6710 does not support these two modes.
6715 Stop the process record and replay target. When process record and
6716 replay target stops, the entire execution log will be deleted and the
6717 inferior will either be terminated, or will remain in its final state.
6719 When you stop the process record and replay target in record mode (at
6720 the end of the execution log), the inferior will be stopped at the
6721 next instruction that would have been recorded. In other words, if
6722 you record for a while and then stop recording, the inferior process
6723 will be left in the same state as if the recording never happened.
6725 On the other hand, if the process record and replay target is stopped
6726 while in replay mode (that is, not at the end of the execution log,
6727 but at some earlier point), the inferior process will become ``live''
6728 at that earlier state, and it will then be possible to continue the
6729 usual ``live'' debugging of the process from that state.
6731 When the inferior process exits, or @value{GDBN} detaches from it,
6732 process record and replay target will automatically stop itself.
6736 Go to a specific location in the execution log. There are several
6737 ways to specify the location to go to:
6740 @item record goto begin
6741 @itemx record goto start
6742 Go to the beginning of the execution log.
6744 @item record goto end
6745 Go to the end of the execution log.
6747 @item record goto @var{n}
6748 Go to instruction number @var{n} in the execution log.
6752 @item record save @var{filename}
6753 Save the execution log to a file @file{@var{filename}}.
6754 Default filename is @file{gdb_record.@var{process_id}}, where
6755 @var{process_id} is the process ID of the inferior.
6757 This command may not be available for all recording methods.
6759 @kindex record restore
6760 @item record restore @var{filename}
6761 Restore the execution log from a file @file{@var{filename}}.
6762 File must have been created with @code{record save}.
6764 @kindex set record full
6765 @item set record full insn-number-max @var{limit}
6766 @itemx set record full insn-number-max unlimited
6767 Set the limit of instructions to be recorded for the @code{full}
6768 recording method. Default value is 200000.
6770 If @var{limit} is a positive number, then @value{GDBN} will start
6771 deleting instructions from the log once the number of the record
6772 instructions becomes greater than @var{limit}. For every new recorded
6773 instruction, @value{GDBN} will delete the earliest recorded
6774 instruction to keep the number of recorded instructions at the limit.
6775 (Since deleting recorded instructions loses information, @value{GDBN}
6776 lets you control what happens when the limit is reached, by means of
6777 the @code{stop-at-limit} option, described below.)
6779 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6780 delete recorded instructions from the execution log. The number of
6781 recorded instructions is limited only by the available memory.
6783 @kindex show record full
6784 @item show record full insn-number-max
6785 Show the limit of instructions to be recorded with the @code{full}
6788 @item set record full stop-at-limit
6789 Control the behavior of the @code{full} recording method when the
6790 number of recorded instructions reaches the limit. If ON (the
6791 default), @value{GDBN} will stop when the limit is reached for the
6792 first time and ask you whether you want to stop the inferior or
6793 continue running it and recording the execution log. If you decide
6794 to continue recording, each new recorded instruction will cause the
6795 oldest one to be deleted.
6797 If this option is OFF, @value{GDBN} will automatically delete the
6798 oldest record to make room for each new one, without asking.
6800 @item show record full stop-at-limit
6801 Show the current setting of @code{stop-at-limit}.
6803 @item set record full memory-query
6804 Control the behavior when @value{GDBN} is unable to record memory
6805 changes caused by an instruction for the @code{full} recording method.
6806 If ON, @value{GDBN} will query whether to stop the inferior in that
6809 If this option is OFF (the default), @value{GDBN} will automatically
6810 ignore the effect of such instructions on memory. Later, when
6811 @value{GDBN} replays this execution log, it will mark the log of this
6812 instruction as not accessible, and it will not affect the replay
6815 @item show record full memory-query
6816 Show the current setting of @code{memory-query}.
6818 @kindex set record btrace
6819 The @code{btrace} record target does not trace data. As a
6820 convenience, when replaying, @value{GDBN} reads read-only memory off
6821 the live program directly, assuming that the addresses of the
6822 read-only areas don't change. This for example makes it possible to
6823 disassemble code while replaying, but not to print variables.
6824 In some cases, being able to inspect variables might be useful.
6825 You can use the following command for that:
6827 @item set record btrace replay-memory-access
6828 Control the behavior of the @code{btrace} recording method when
6829 accessing memory during replay. If @code{read-only} (the default),
6830 @value{GDBN} will only allow accesses to read-only memory.
6831 If @code{read-write}, @value{GDBN} will allow accesses to read-only
6832 and to read-write memory. Beware that the accessed memory corresponds
6833 to the live target and not necessarily to the current replay
6836 @kindex show record btrace
6837 @item show record btrace replay-memory-access
6838 Show the current setting of @code{replay-memory-access}.
6840 @kindex set record btrace bts
6841 @item set record btrace bts buffer-size @var{size}
6842 @itemx set record btrace bts buffer-size unlimited
6843 Set the requested ring buffer size for branch tracing in @acronym{BTS}
6844 format. Default is 64KB.
6846 If @var{size} is a positive number, then @value{GDBN} will try to
6847 allocate a buffer of at least @var{size} bytes for each new thread
6848 that uses the btrace recording method and the @acronym{BTS} format.
6849 The actually obtained buffer size may differ from the requested
6850 @var{size}. Use the @code{info record} command to see the actual
6851 buffer size for each thread that uses the btrace recording method and
6852 the @acronym{BTS} format.
6854 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6855 allocate a buffer of 4MB.
6857 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6858 also need longer to process the branch trace data before it can be used.
6860 @item show record btrace bts buffer-size @var{size}
6861 Show the current setting of the requested ring buffer size for branch
6862 tracing in @acronym{BTS} format.
6864 @kindex set record btrace pt
6865 @item set record btrace pt buffer-size @var{size}
6866 @itemx set record btrace pt buffer-size unlimited
6867 Set the requested ring buffer size for branch tracing in Intel
6868 Processor Trace format. Default is 16KB.
6870 If @var{size} is a positive number, then @value{GDBN} will try to
6871 allocate a buffer of at least @var{size} bytes for each new thread
6872 that uses the btrace recording method and the Intel Processor Trace
6873 format. The actually obtained buffer size may differ from the
6874 requested @var{size}. Use the @code{info record} command to see the
6875 actual buffer size for each thread.
6877 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6878 allocate a buffer of 4MB.
6880 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6881 also need longer to process the branch trace data before it can be used.
6883 @item show record btrace pt buffer-size @var{size}
6884 Show the current setting of the requested ring buffer size for branch
6885 tracing in Intel Processor Trace format.
6889 Show various statistics about the recording depending on the recording
6894 For the @code{full} recording method, it shows the state of process
6895 record and its in-memory execution log buffer, including:
6899 Whether in record mode or replay mode.
6901 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6903 Highest recorded instruction number.
6905 Current instruction about to be replayed (if in replay mode).
6907 Number of instructions contained in the execution log.
6909 Maximum number of instructions that may be contained in the execution log.
6913 For the @code{btrace} recording method, it shows:
6919 Number of instructions that have been recorded.
6921 Number of blocks of sequential control-flow formed by the recorded
6924 Whether in record mode or replay mode.
6927 For the @code{bts} recording format, it also shows:
6930 Size of the perf ring buffer.
6933 For the @code{pt} recording format, it also shows:
6936 Size of the perf ring buffer.
6940 @kindex record delete
6943 When record target runs in replay mode (``in the past''), delete the
6944 subsequent execution log and begin to record a new execution log starting
6945 from the current address. This means you will abandon the previously
6946 recorded ``future'' and begin recording a new ``future''.
6948 @kindex record instruction-history
6949 @kindex rec instruction-history
6950 @item record instruction-history
6951 Disassembles instructions from the recorded execution log. By
6952 default, ten instructions are disassembled. This can be changed using
6953 the @code{set record instruction-history-size} command. Instructions
6954 are printed in execution order.
6956 It can also print mixed source+disassembly if you specify the the
6957 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
6958 as well as in symbolic form by specifying the @code{/r} modifier.
6960 The current position marker is printed for the instruction at the
6961 current program counter value. This instruction can appear multiple
6962 times in the trace and the current position marker will be printed
6963 every time. To omit the current position marker, specify the
6966 To better align the printed instructions when the trace contains
6967 instructions from more than one function, the function name may be
6968 omitted by specifying the @code{/f} modifier.
6970 Speculatively executed instructions are prefixed with @samp{?}. This
6971 feature is not available for all recording formats.
6973 There are several ways to specify what part of the execution log to
6977 @item record instruction-history @var{insn}
6978 Disassembles ten instructions starting from instruction number
6981 @item record instruction-history @var{insn}, +/-@var{n}
6982 Disassembles @var{n} instructions around instruction number
6983 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
6984 @var{n} instructions after instruction number @var{insn}. If
6985 @var{n} is preceded with @code{-}, disassembles @var{n}
6986 instructions before instruction number @var{insn}.
6988 @item record instruction-history
6989 Disassembles ten more instructions after the last disassembly.
6991 @item record instruction-history -
6992 Disassembles ten more instructions before the last disassembly.
6994 @item record instruction-history @var{begin}, @var{end}
6995 Disassembles instructions beginning with instruction number
6996 @var{begin} until instruction number @var{end}. The instruction
6997 number @var{end} is included.
7000 This command may not be available for all recording methods.
7003 @item set record instruction-history-size @var{size}
7004 @itemx set record instruction-history-size unlimited
7005 Define how many instructions to disassemble in the @code{record
7006 instruction-history} command. The default value is 10.
7007 A @var{size} of @code{unlimited} means unlimited instructions.
7010 @item show record instruction-history-size
7011 Show how many instructions to disassemble in the @code{record
7012 instruction-history} command.
7014 @kindex record function-call-history
7015 @kindex rec function-call-history
7016 @item record function-call-history
7017 Prints the execution history at function granularity. It prints one
7018 line for each sequence of instructions that belong to the same
7019 function giving the name of that function, the source lines
7020 for this instruction sequence (if the @code{/l} modifier is
7021 specified), and the instructions numbers that form the sequence (if
7022 the @code{/i} modifier is specified). The function names are indented
7023 to reflect the call stack depth if the @code{/c} modifier is
7024 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
7028 (@value{GDBP}) @b{list 1, 10}
7039 (@value{GDBP}) @b{record function-call-history /ilc}
7040 1 bar inst 1,4 at foo.c:6,8
7041 2 foo inst 5,10 at foo.c:2,3
7042 3 bar inst 11,13 at foo.c:9,10
7045 By default, ten lines are printed. This can be changed using the
7046 @code{set record function-call-history-size} command. Functions are
7047 printed in execution order. There are several ways to specify what
7051 @item record function-call-history @var{func}
7052 Prints ten functions starting from function number @var{func}.
7054 @item record function-call-history @var{func}, +/-@var{n}
7055 Prints @var{n} functions around function number @var{func}. If
7056 @var{n} is preceded with @code{+}, prints @var{n} functions after
7057 function number @var{func}. If @var{n} is preceded with @code{-},
7058 prints @var{n} functions before function number @var{func}.
7060 @item record function-call-history
7061 Prints ten more functions after the last ten-line print.
7063 @item record function-call-history -
7064 Prints ten more functions before the last ten-line print.
7066 @item record function-call-history @var{begin}, @var{end}
7067 Prints functions beginning with function number @var{begin} until
7068 function number @var{end}. The function number @var{end} is included.
7071 This command may not be available for all recording methods.
7073 @item set record function-call-history-size @var{size}
7074 @itemx set record function-call-history-size unlimited
7075 Define how many lines to print in the
7076 @code{record function-call-history} command. The default value is 10.
7077 A size of @code{unlimited} means unlimited lines.
7079 @item show record function-call-history-size
7080 Show how many lines to print in the
7081 @code{record function-call-history} command.
7086 @chapter Examining the Stack
7088 When your program has stopped, the first thing you need to know is where it
7089 stopped and how it got there.
7092 Each time your program performs a function call, information about the call
7094 That information includes the location of the call in your program,
7095 the arguments of the call,
7096 and the local variables of the function being called.
7097 The information is saved in a block of data called a @dfn{stack frame}.
7098 The stack frames are allocated in a region of memory called the @dfn{call
7101 When your program stops, the @value{GDBN} commands for examining the
7102 stack allow you to see all of this information.
7104 @cindex selected frame
7105 One of the stack frames is @dfn{selected} by @value{GDBN} and many
7106 @value{GDBN} commands refer implicitly to the selected frame. In
7107 particular, whenever you ask @value{GDBN} for the value of a variable in
7108 your program, the value is found in the selected frame. There are
7109 special @value{GDBN} commands to select whichever frame you are
7110 interested in. @xref{Selection, ,Selecting a Frame}.
7112 When your program stops, @value{GDBN} automatically selects the
7113 currently executing frame and describes it briefly, similar to the
7114 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
7117 * Frames:: Stack frames
7118 * Backtrace:: Backtraces
7119 * Selection:: Selecting a frame
7120 * Frame Info:: Information on a frame
7121 * Frame Filter Management:: Managing frame filters
7126 @section Stack Frames
7128 @cindex frame, definition
7130 The call stack is divided up into contiguous pieces called @dfn{stack
7131 frames}, or @dfn{frames} for short; each frame is the data associated
7132 with one call to one function. The frame contains the arguments given
7133 to the function, the function's local variables, and the address at
7134 which the function is executing.
7136 @cindex initial frame
7137 @cindex outermost frame
7138 @cindex innermost frame
7139 When your program is started, the stack has only one frame, that of the
7140 function @code{main}. This is called the @dfn{initial} frame or the
7141 @dfn{outermost} frame. Each time a function is called, a new frame is
7142 made. Each time a function returns, the frame for that function invocation
7143 is eliminated. If a function is recursive, there can be many frames for
7144 the same function. The frame for the function in which execution is
7145 actually occurring is called the @dfn{innermost} frame. This is the most
7146 recently created of all the stack frames that still exist.
7148 @cindex frame pointer
7149 Inside your program, stack frames are identified by their addresses. A
7150 stack frame consists of many bytes, each of which has its own address; each
7151 kind of computer has a convention for choosing one byte whose
7152 address serves as the address of the frame. Usually this address is kept
7153 in a register called the @dfn{frame pointer register}
7154 (@pxref{Registers, $fp}) while execution is going on in that frame.
7156 @cindex frame number
7157 @value{GDBN} assigns numbers to all existing stack frames, starting with
7158 zero for the innermost frame, one for the frame that called it,
7159 and so on upward. These numbers do not really exist in your program;
7160 they are assigned by @value{GDBN} to give you a way of designating stack
7161 frames in @value{GDBN} commands.
7163 @c The -fomit-frame-pointer below perennially causes hbox overflow
7164 @c underflow problems.
7165 @cindex frameless execution
7166 Some compilers provide a way to compile functions so that they operate
7167 without stack frames. (For example, the @value{NGCC} option
7169 @samp{-fomit-frame-pointer}
7171 generates functions without a frame.)
7172 This is occasionally done with heavily used library functions to save
7173 the frame setup time. @value{GDBN} has limited facilities for dealing
7174 with these function invocations. If the innermost function invocation
7175 has no stack frame, @value{GDBN} nevertheless regards it as though
7176 it had a separate frame, which is numbered zero as usual, allowing
7177 correct tracing of the function call chain. However, @value{GDBN} has
7178 no provision for frameless functions elsewhere in the stack.
7184 @cindex call stack traces
7185 A backtrace is a summary of how your program got where it is. It shows one
7186 line per frame, for many frames, starting with the currently executing
7187 frame (frame zero), followed by its caller (frame one), and on up the
7190 @anchor{backtrace-command}
7193 @kindex bt @r{(@code{backtrace})}
7196 Print a backtrace of the entire stack: one line per frame for all
7197 frames in the stack.
7199 You can stop the backtrace at any time by typing the system interrupt
7200 character, normally @kbd{Ctrl-c}.
7202 @item backtrace @var{n}
7204 Similar, but print only the innermost @var{n} frames.
7206 @item backtrace -@var{n}
7208 Similar, but print only the outermost @var{n} frames.
7210 @item backtrace full
7212 @itemx bt full @var{n}
7213 @itemx bt full -@var{n}
7214 Print the values of the local variables also. As described above,
7215 @var{n} specifies the number of frames to print.
7217 @item backtrace no-filters
7218 @itemx bt no-filters
7219 @itemx bt no-filters @var{n}
7220 @itemx bt no-filters -@var{n}
7221 @itemx bt no-filters full
7222 @itemx bt no-filters full @var{n}
7223 @itemx bt no-filters full -@var{n}
7224 Do not run Python frame filters on this backtrace. @xref{Frame
7225 Filter API}, for more information. Additionally use @ref{disable
7226 frame-filter all} to turn off all frame filters. This is only
7227 relevant when @value{GDBN} has been configured with @code{Python}
7233 The names @code{where} and @code{info stack} (abbreviated @code{info s})
7234 are additional aliases for @code{backtrace}.
7236 @cindex multiple threads, backtrace
7237 In a multi-threaded program, @value{GDBN} by default shows the
7238 backtrace only for the current thread. To display the backtrace for
7239 several or all of the threads, use the command @code{thread apply}
7240 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
7241 apply all backtrace}, @value{GDBN} will display the backtrace for all
7242 the threads; this is handy when you debug a core dump of a
7243 multi-threaded program.
7245 Each line in the backtrace shows the frame number and the function name.
7246 The program counter value is also shown---unless you use @code{set
7247 print address off}. The backtrace also shows the source file name and
7248 line number, as well as the arguments to the function. The program
7249 counter value is omitted if it is at the beginning of the code for that
7252 Here is an example of a backtrace. It was made with the command
7253 @samp{bt 3}, so it shows the innermost three frames.
7257 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7259 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
7260 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
7262 (More stack frames follow...)
7267 The display for frame zero does not begin with a program counter
7268 value, indicating that your program has stopped at the beginning of the
7269 code for line @code{993} of @code{builtin.c}.
7272 The value of parameter @code{data} in frame 1 has been replaced by
7273 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
7274 only if it is a scalar (integer, pointer, enumeration, etc). See command
7275 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
7276 on how to configure the way function parameter values are printed.
7278 @cindex optimized out, in backtrace
7279 @cindex function call arguments, optimized out
7280 If your program was compiled with optimizations, some compilers will
7281 optimize away arguments passed to functions if those arguments are
7282 never used after the call. Such optimizations generate code that
7283 passes arguments through registers, but doesn't store those arguments
7284 in the stack frame. @value{GDBN} has no way of displaying such
7285 arguments in stack frames other than the innermost one. Here's what
7286 such a backtrace might look like:
7290 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7292 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
7293 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
7295 (More stack frames follow...)
7300 The values of arguments that were not saved in their stack frames are
7301 shown as @samp{<optimized out>}.
7303 If you need to display the values of such optimized-out arguments,
7304 either deduce that from other variables whose values depend on the one
7305 you are interested in, or recompile without optimizations.
7307 @cindex backtrace beyond @code{main} function
7308 @cindex program entry point
7309 @cindex startup code, and backtrace
7310 Most programs have a standard user entry point---a place where system
7311 libraries and startup code transition into user code. For C this is
7312 @code{main}@footnote{
7313 Note that embedded programs (the so-called ``free-standing''
7314 environment) are not required to have a @code{main} function as the
7315 entry point. They could even have multiple entry points.}.
7316 When @value{GDBN} finds the entry function in a backtrace
7317 it will terminate the backtrace, to avoid tracing into highly
7318 system-specific (and generally uninteresting) code.
7320 If you need to examine the startup code, or limit the number of levels
7321 in a backtrace, you can change this behavior:
7324 @item set backtrace past-main
7325 @itemx set backtrace past-main on
7326 @kindex set backtrace
7327 Backtraces will continue past the user entry point.
7329 @item set backtrace past-main off
7330 Backtraces will stop when they encounter the user entry point. This is the
7333 @item show backtrace past-main
7334 @kindex show backtrace
7335 Display the current user entry point backtrace policy.
7337 @item set backtrace past-entry
7338 @itemx set backtrace past-entry on
7339 Backtraces will continue past the internal entry point of an application.
7340 This entry point is encoded by the linker when the application is built,
7341 and is likely before the user entry point @code{main} (or equivalent) is called.
7343 @item set backtrace past-entry off
7344 Backtraces will stop when they encounter the internal entry point of an
7345 application. This is the default.
7347 @item show backtrace past-entry
7348 Display the current internal entry point backtrace policy.
7350 @item set backtrace limit @var{n}
7351 @itemx set backtrace limit 0
7352 @itemx set backtrace limit unlimited
7353 @cindex backtrace limit
7354 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
7355 or zero means unlimited levels.
7357 @item show backtrace limit
7358 Display the current limit on backtrace levels.
7361 You can control how file names are displayed.
7364 @item set filename-display
7365 @itemx set filename-display relative
7366 @cindex filename-display
7367 Display file names relative to the compilation directory. This is the default.
7369 @item set filename-display basename
7370 Display only basename of a filename.
7372 @item set filename-display absolute
7373 Display an absolute filename.
7375 @item show filename-display
7376 Show the current way to display filenames.
7380 @section Selecting a Frame
7382 Most commands for examining the stack and other data in your program work on
7383 whichever stack frame is selected at the moment. Here are the commands for
7384 selecting a stack frame; all of them finish by printing a brief description
7385 of the stack frame just selected.
7388 @kindex frame@r{, selecting}
7389 @kindex f @r{(@code{frame})}
7392 Select frame number @var{n}. Recall that frame zero is the innermost
7393 (currently executing) frame, frame one is the frame that called the
7394 innermost one, and so on. The highest-numbered frame is the one for
7397 @item frame @var{stack-addr} [ @var{pc-addr} ]
7398 @itemx f @var{stack-addr} [ @var{pc-addr} ]
7399 Select the frame at address @var{stack-addr}. This is useful mainly if the
7400 chaining of stack frames has been damaged by a bug, making it
7401 impossible for @value{GDBN} to assign numbers properly to all frames. In
7402 addition, this can be useful when your program has multiple stacks and
7403 switches between them. The optional @var{pc-addr} can also be given to
7404 specify the value of PC for the stack frame.
7408 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
7409 numbers @var{n}, this advances toward the outermost frame, to higher
7410 frame numbers, to frames that have existed longer.
7413 @kindex do @r{(@code{down})}
7415 Move @var{n} frames down the stack; @var{n} defaults to 1. For
7416 positive numbers @var{n}, this advances toward the innermost frame, to
7417 lower frame numbers, to frames that were created more recently.
7418 You may abbreviate @code{down} as @code{do}.
7421 All of these commands end by printing two lines of output describing the
7422 frame. The first line shows the frame number, the function name, the
7423 arguments, and the source file and line number of execution in that
7424 frame. The second line shows the text of that source line.
7432 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7434 10 read_input_file (argv[i]);
7438 After such a printout, the @code{list} command with no arguments
7439 prints ten lines centered on the point of execution in the frame.
7440 You can also edit the program at the point of execution with your favorite
7441 editing program by typing @code{edit}.
7442 @xref{List, ,Printing Source Lines},
7446 @kindex select-frame
7448 The @code{select-frame} command is a variant of @code{frame} that does
7449 not display the new frame after selecting it. This command is
7450 intended primarily for use in @value{GDBN} command scripts, where the
7451 output might be unnecessary and distracting.
7453 @kindex down-silently
7455 @item up-silently @var{n}
7456 @itemx down-silently @var{n}
7457 These two commands are variants of @code{up} and @code{down},
7458 respectively; they differ in that they do their work silently, without
7459 causing display of the new frame. They are intended primarily for use
7460 in @value{GDBN} command scripts, where the output might be unnecessary and
7465 @section Information About a Frame
7467 There are several other commands to print information about the selected
7473 When used without any argument, this command does not change which
7474 frame is selected, but prints a brief description of the currently
7475 selected stack frame. It can be abbreviated @code{f}. With an
7476 argument, this command is used to select a stack frame.
7477 @xref{Selection, ,Selecting a Frame}.
7480 @kindex info f @r{(@code{info frame})}
7483 This command prints a verbose description of the selected stack frame,
7488 the address of the frame
7490 the address of the next frame down (called by this frame)
7492 the address of the next frame up (caller of this frame)
7494 the language in which the source code corresponding to this frame is written
7496 the address of the frame's arguments
7498 the address of the frame's local variables
7500 the program counter saved in it (the address of execution in the caller frame)
7502 which registers were saved in the frame
7505 @noindent The verbose description is useful when
7506 something has gone wrong that has made the stack format fail to fit
7507 the usual conventions.
7509 @item info frame @var{addr}
7510 @itemx info f @var{addr}
7511 Print a verbose description of the frame at address @var{addr}, without
7512 selecting that frame. The selected frame remains unchanged by this
7513 command. This requires the same kind of address (more than one for some
7514 architectures) that you specify in the @code{frame} command.
7515 @xref{Selection, ,Selecting a Frame}.
7519 Print the arguments of the selected frame, each on a separate line.
7523 Print the local variables of the selected frame, each on a separate
7524 line. These are all variables (declared either static or automatic)
7525 accessible at the point of execution of the selected frame.
7529 @node Frame Filter Management
7530 @section Management of Frame Filters.
7531 @cindex managing frame filters
7533 Frame filters are Python based utilities to manage and decorate the
7534 output of frames. @xref{Frame Filter API}, for further information.
7536 Managing frame filters is performed by several commands available
7537 within @value{GDBN}, detailed here.
7540 @kindex info frame-filter
7541 @item info frame-filter
7542 Print a list of installed frame filters from all dictionaries, showing
7543 their name, priority and enabled status.
7545 @kindex disable frame-filter
7546 @anchor{disable frame-filter all}
7547 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
7548 Disable a frame filter in the dictionary matching
7549 @var{filter-dictionary} and @var{filter-name}. The
7550 @var{filter-dictionary} may be @code{all}, @code{global},
7551 @code{progspace}, or the name of the object file where the frame filter
7552 dictionary resides. When @code{all} is specified, all frame filters
7553 across all dictionaries are disabled. The @var{filter-name} is the name
7554 of the frame filter and is used when @code{all} is not the option for
7555 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
7556 may be enabled again later.
7558 @kindex enable frame-filter
7559 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
7560 Enable a frame filter in the dictionary matching
7561 @var{filter-dictionary} and @var{filter-name}. The
7562 @var{filter-dictionary} may be @code{all}, @code{global},
7563 @code{progspace} or the name of the object file where the frame filter
7564 dictionary resides. When @code{all} is specified, all frame filters across
7565 all dictionaries are enabled. The @var{filter-name} is the name of the frame
7566 filter and is used when @code{all} is not the option for
7567 @var{filter-dictionary}.
7572 (gdb) info frame-filter
7574 global frame-filters:
7575 Priority Enabled Name
7576 1000 No PrimaryFunctionFilter
7579 progspace /build/test frame-filters:
7580 Priority Enabled Name
7581 100 Yes ProgspaceFilter
7583 objfile /build/test frame-filters:
7584 Priority Enabled Name
7585 999 Yes BuildProgra Filter
7587 (gdb) disable frame-filter /build/test BuildProgramFilter
7588 (gdb) info frame-filter
7590 global frame-filters:
7591 Priority Enabled Name
7592 1000 No PrimaryFunctionFilter
7595 progspace /build/test frame-filters:
7596 Priority Enabled Name
7597 100 Yes ProgspaceFilter
7599 objfile /build/test frame-filters:
7600 Priority Enabled Name
7601 999 No BuildProgramFilter
7603 (gdb) enable frame-filter global PrimaryFunctionFilter
7604 (gdb) info frame-filter
7606 global frame-filters:
7607 Priority Enabled Name
7608 1000 Yes PrimaryFunctionFilter
7611 progspace /build/test frame-filters:
7612 Priority Enabled Name
7613 100 Yes ProgspaceFilter
7615 objfile /build/test frame-filters:
7616 Priority Enabled Name
7617 999 No BuildProgramFilter
7620 @kindex set frame-filter priority
7621 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
7622 Set the @var{priority} of a frame filter in the dictionary matching
7623 @var{filter-dictionary}, and the frame filter name matching
7624 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7625 @code{progspace} or the name of the object file where the frame filter
7626 dictionary resides. The @var{priority} is an integer.
7628 @kindex show frame-filter priority
7629 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
7630 Show the @var{priority} of a frame filter in the dictionary matching
7631 @var{filter-dictionary}, and the frame filter name matching
7632 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7633 @code{progspace} or the name of the object file where the frame filter
7639 (gdb) info frame-filter
7641 global frame-filters:
7642 Priority Enabled Name
7643 1000 Yes PrimaryFunctionFilter
7646 progspace /build/test frame-filters:
7647 Priority Enabled Name
7648 100 Yes ProgspaceFilter
7650 objfile /build/test frame-filters:
7651 Priority Enabled Name
7652 999 No BuildProgramFilter
7654 (gdb) set frame-filter priority global Reverse 50
7655 (gdb) info frame-filter
7657 global frame-filters:
7658 Priority Enabled Name
7659 1000 Yes PrimaryFunctionFilter
7662 progspace /build/test frame-filters:
7663 Priority Enabled Name
7664 100 Yes ProgspaceFilter
7666 objfile /build/test frame-filters:
7667 Priority Enabled Name
7668 999 No BuildProgramFilter
7673 @chapter Examining Source Files
7675 @value{GDBN} can print parts of your program's source, since the debugging
7676 information recorded in the program tells @value{GDBN} what source files were
7677 used to build it. When your program stops, @value{GDBN} spontaneously prints
7678 the line where it stopped. Likewise, when you select a stack frame
7679 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7680 execution in that frame has stopped. You can print other portions of
7681 source files by explicit command.
7683 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7684 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7685 @value{GDBN} under @sc{gnu} Emacs}.
7688 * List:: Printing source lines
7689 * Specify Location:: How to specify code locations
7690 * Edit:: Editing source files
7691 * Search:: Searching source files
7692 * Source Path:: Specifying source directories
7693 * Machine Code:: Source and machine code
7697 @section Printing Source Lines
7700 @kindex l @r{(@code{list})}
7701 To print lines from a source file, use the @code{list} command
7702 (abbreviated @code{l}). By default, ten lines are printed.
7703 There are several ways to specify what part of the file you want to
7704 print; see @ref{Specify Location}, for the full list.
7706 Here are the forms of the @code{list} command most commonly used:
7709 @item list @var{linenum}
7710 Print lines centered around line number @var{linenum} in the
7711 current source file.
7713 @item list @var{function}
7714 Print lines centered around the beginning of function
7718 Print more lines. If the last lines printed were printed with a
7719 @code{list} command, this prints lines following the last lines
7720 printed; however, if the last line printed was a solitary line printed
7721 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7722 Stack}), this prints lines centered around that line.
7725 Print lines just before the lines last printed.
7728 @cindex @code{list}, how many lines to display
7729 By default, @value{GDBN} prints ten source lines with any of these forms of
7730 the @code{list} command. You can change this using @code{set listsize}:
7733 @kindex set listsize
7734 @item set listsize @var{count}
7735 @itemx set listsize unlimited
7736 Make the @code{list} command display @var{count} source lines (unless
7737 the @code{list} argument explicitly specifies some other number).
7738 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7740 @kindex show listsize
7742 Display the number of lines that @code{list} prints.
7745 Repeating a @code{list} command with @key{RET} discards the argument,
7746 so it is equivalent to typing just @code{list}. This is more useful
7747 than listing the same lines again. An exception is made for an
7748 argument of @samp{-}; that argument is preserved in repetition so that
7749 each repetition moves up in the source file.
7751 In general, the @code{list} command expects you to supply zero, one or two
7752 @dfn{locations}. Locations specify source lines; there are several ways
7753 of writing them (@pxref{Specify Location}), but the effect is always
7754 to specify some source line.
7756 Here is a complete description of the possible arguments for @code{list}:
7759 @item list @var{location}
7760 Print lines centered around the line specified by @var{location}.
7762 @item list @var{first},@var{last}
7763 Print lines from @var{first} to @var{last}. Both arguments are
7764 locations. When a @code{list} command has two locations, and the
7765 source file of the second location is omitted, this refers to
7766 the same source file as the first location.
7768 @item list ,@var{last}
7769 Print lines ending with @var{last}.
7771 @item list @var{first},
7772 Print lines starting with @var{first}.
7775 Print lines just after the lines last printed.
7778 Print lines just before the lines last printed.
7781 As described in the preceding table.
7784 @node Specify Location
7785 @section Specifying a Location
7786 @cindex specifying location
7788 @cindex source location
7791 * Linespec Locations:: Linespec locations
7792 * Explicit Locations:: Explicit locations
7793 * Address Locations:: Address locations
7796 Several @value{GDBN} commands accept arguments that specify a location
7797 of your program's code. Since @value{GDBN} is a source-level
7798 debugger, a location usually specifies some line in the source code.
7799 Locations may be specified using three different formats:
7800 linespec locations, explicit locations, or address locations.
7802 @node Linespec Locations
7803 @subsection Linespec Locations
7804 @cindex linespec locations
7806 A @dfn{linespec} is a colon-separated list of source location parameters such
7807 as file name, function name, etc. Here are all the different ways of
7808 specifying a linespec:
7812 Specifies the line number @var{linenum} of the current source file.
7815 @itemx +@var{offset}
7816 Specifies the line @var{offset} lines before or after the @dfn{current
7817 line}. For the @code{list} command, the current line is the last one
7818 printed; for the breakpoint commands, this is the line at which
7819 execution stopped in the currently selected @dfn{stack frame}
7820 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7821 used as the second of the two linespecs in a @code{list} command,
7822 this specifies the line @var{offset} lines up or down from the first
7825 @item @var{filename}:@var{linenum}
7826 Specifies the line @var{linenum} in the source file @var{filename}.
7827 If @var{filename} is a relative file name, then it will match any
7828 source file name with the same trailing components. For example, if
7829 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7830 name of @file{/build/trunk/gcc/expr.c}, but not
7831 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7833 @item @var{function}
7834 Specifies the line that begins the body of the function @var{function}.
7835 For example, in C, this is the line with the open brace.
7837 @item @var{function}:@var{label}
7838 Specifies the line where @var{label} appears in @var{function}.
7840 @item @var{filename}:@var{function}
7841 Specifies the line that begins the body of the function @var{function}
7842 in the file @var{filename}. You only need the file name with a
7843 function name to avoid ambiguity when there are identically named
7844 functions in different source files.
7847 Specifies the line at which the label named @var{label} appears
7848 in the function corresponding to the currently selected stack frame.
7849 If there is no current selected stack frame (for instance, if the inferior
7850 is not running), then @value{GDBN} will not search for a label.
7852 @cindex breakpoint at static probe point
7853 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7854 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7855 applications to embed static probes. @xref{Static Probe Points}, for more
7856 information on finding and using static probes. This form of linespec
7857 specifies the location of such a static probe.
7859 If @var{objfile} is given, only probes coming from that shared library
7860 or executable matching @var{objfile} as a regular expression are considered.
7861 If @var{provider} is given, then only probes from that provider are considered.
7862 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7863 each one of those probes.
7866 @node Explicit Locations
7867 @subsection Explicit Locations
7868 @cindex explicit locations
7870 @dfn{Explicit locations} allow the user to directly specify the source
7871 location's parameters using option-value pairs.
7873 Explicit locations are useful when several functions, labels, or
7874 file names have the same name (base name for files) in the program's
7875 sources. In these cases, explicit locations point to the source
7876 line you meant more accurately and unambiguously. Also, using
7877 explicit locations might be faster in large programs.
7879 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
7880 defined in the file named @file{foo} or the label @code{bar} in a function
7881 named @code{foo}. @value{GDBN} must search either the file system or
7882 the symbol table to know.
7884 The list of valid explicit location options is summarized in the
7888 @item -source @var{filename}
7889 The value specifies the source file name. To differentiate between
7890 files with the same base name, prepend as many directories as is necessary
7891 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
7892 @value{GDBN} will use the first file it finds with the given base
7893 name. This option requires the use of either @code{-function} or @code{-line}.
7895 @item -function @var{function}
7896 The value specifies the name of a function. Operations
7897 on function locations unmodified by other options (such as @code{-label}
7898 or @code{-line}) refer to the line that begins the body of the function.
7899 In C, for example, this is the line with the open brace.
7901 @item -label @var{label}
7902 The value specifies the name of a label. When the function
7903 name is not specified, the label is searched in the function of the currently
7904 selected stack frame.
7906 @item -line @var{number}
7907 The value specifies a line offset for the location. The offset may either
7908 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
7909 the command. When specified without any other options, the line offset is
7910 relative to the current line.
7913 Explicit location options may be abbreviated by omitting any non-unique
7914 trailing characters from the option name, e.g., @code{break -s main.c -li 3}.
7916 @node Address Locations
7917 @subsection Address Locations
7918 @cindex address locations
7920 @dfn{Address locations} indicate a specific program address. They have
7921 the generalized form *@var{address}.
7923 For line-oriented commands, such as @code{list} and @code{edit}, this
7924 specifies a source line that contains @var{address}. For @code{break} and
7925 other breakpoint-oriented commands, this can be used to set breakpoints in
7926 parts of your program which do not have debugging information or
7929 Here @var{address} may be any expression valid in the current working
7930 language (@pxref{Languages, working language}) that specifies a code
7931 address. In addition, as a convenience, @value{GDBN} extends the
7932 semantics of expressions used in locations to cover several situations
7933 that frequently occur during debugging. Here are the various forms
7937 @item @var{expression}
7938 Any expression valid in the current working language.
7940 @item @var{funcaddr}
7941 An address of a function or procedure derived from its name. In C,
7942 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
7943 simply the function's name @var{function} (and actually a special case
7944 of a valid expression). In Pascal and Modula-2, this is
7945 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
7946 (although the Pascal form also works).
7948 This form specifies the address of the function's first instruction,
7949 before the stack frame and arguments have been set up.
7951 @item '@var{filename}':@var{funcaddr}
7952 Like @var{funcaddr} above, but also specifies the name of the source
7953 file explicitly. This is useful if the name of the function does not
7954 specify the function unambiguously, e.g., if there are several
7955 functions with identical names in different source files.
7959 @section Editing Source Files
7960 @cindex editing source files
7963 @kindex e @r{(@code{edit})}
7964 To edit the lines in a source file, use the @code{edit} command.
7965 The editing program of your choice
7966 is invoked with the current line set to
7967 the active line in the program.
7968 Alternatively, there are several ways to specify what part of the file you
7969 want to print if you want to see other parts of the program:
7972 @item edit @var{location}
7973 Edit the source file specified by @code{location}. Editing starts at
7974 that @var{location}, e.g., at the specified source line of the
7975 specified file. @xref{Specify Location}, for all the possible forms
7976 of the @var{location} argument; here are the forms of the @code{edit}
7977 command most commonly used:
7980 @item edit @var{number}
7981 Edit the current source file with @var{number} as the active line number.
7983 @item edit @var{function}
7984 Edit the file containing @var{function} at the beginning of its definition.
7989 @subsection Choosing your Editor
7990 You can customize @value{GDBN} to use any editor you want
7992 The only restriction is that your editor (say @code{ex}), recognizes the
7993 following command-line syntax:
7995 ex +@var{number} file
7997 The optional numeric value +@var{number} specifies the number of the line in
7998 the file where to start editing.}.
7999 By default, it is @file{@value{EDITOR}}, but you can change this
8000 by setting the environment variable @code{EDITOR} before using
8001 @value{GDBN}. For example, to configure @value{GDBN} to use the
8002 @code{vi} editor, you could use these commands with the @code{sh} shell:
8008 or in the @code{csh} shell,
8010 setenv EDITOR /usr/bin/vi
8015 @section Searching Source Files
8016 @cindex searching source files
8018 There are two commands for searching through the current source file for a
8023 @kindex forward-search
8024 @kindex fo @r{(@code{forward-search})}
8025 @item forward-search @var{regexp}
8026 @itemx search @var{regexp}
8027 The command @samp{forward-search @var{regexp}} checks each line,
8028 starting with the one following the last line listed, for a match for
8029 @var{regexp}. It lists the line that is found. You can use the
8030 synonym @samp{search @var{regexp}} or abbreviate the command name as
8033 @kindex reverse-search
8034 @item reverse-search @var{regexp}
8035 The command @samp{reverse-search @var{regexp}} checks each line, starting
8036 with the one before the last line listed and going backward, for a match
8037 for @var{regexp}. It lists the line that is found. You can abbreviate
8038 this command as @code{rev}.
8042 @section Specifying Source Directories
8045 @cindex directories for source files
8046 Executable programs sometimes do not record the directories of the source
8047 files from which they were compiled, just the names. Even when they do,
8048 the directories could be moved between the compilation and your debugging
8049 session. @value{GDBN} has a list of directories to search for source files;
8050 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
8051 it tries all the directories in the list, in the order they are present
8052 in the list, until it finds a file with the desired name.
8054 For example, suppose an executable references the file
8055 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
8056 @file{/mnt/cross}. The file is first looked up literally; if this
8057 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
8058 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
8059 message is printed. @value{GDBN} does not look up the parts of the
8060 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
8061 Likewise, the subdirectories of the source path are not searched: if
8062 the source path is @file{/mnt/cross}, and the binary refers to
8063 @file{foo.c}, @value{GDBN} would not find it under
8064 @file{/mnt/cross/usr/src/foo-1.0/lib}.
8066 Plain file names, relative file names with leading directories, file
8067 names containing dots, etc.@: are all treated as described above; for
8068 instance, if the source path is @file{/mnt/cross}, and the source file
8069 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
8070 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
8071 that---@file{/mnt/cross/foo.c}.
8073 Note that the executable search path is @emph{not} used to locate the
8076 Whenever you reset or rearrange the source path, @value{GDBN} clears out
8077 any information it has cached about where source files are found and where
8078 each line is in the file.
8082 When you start @value{GDBN}, its source path includes only @samp{cdir}
8083 and @samp{cwd}, in that order.
8084 To add other directories, use the @code{directory} command.
8086 The search path is used to find both program source files and @value{GDBN}
8087 script files (read using the @samp{-command} option and @samp{source} command).
8089 In addition to the source path, @value{GDBN} provides a set of commands
8090 that manage a list of source path substitution rules. A @dfn{substitution
8091 rule} specifies how to rewrite source directories stored in the program's
8092 debug information in case the sources were moved to a different
8093 directory between compilation and debugging. A rule is made of
8094 two strings, the first specifying what needs to be rewritten in
8095 the path, and the second specifying how it should be rewritten.
8096 In @ref{set substitute-path}, we name these two parts @var{from} and
8097 @var{to} respectively. @value{GDBN} does a simple string replacement
8098 of @var{from} with @var{to} at the start of the directory part of the
8099 source file name, and uses that result instead of the original file
8100 name to look up the sources.
8102 Using the previous example, suppose the @file{foo-1.0} tree has been
8103 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
8104 @value{GDBN} to replace @file{/usr/src} in all source path names with
8105 @file{/mnt/cross}. The first lookup will then be
8106 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
8107 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
8108 substitution rule, use the @code{set substitute-path} command
8109 (@pxref{set substitute-path}).
8111 To avoid unexpected substitution results, a rule is applied only if the
8112 @var{from} part of the directory name ends at a directory separator.
8113 For instance, a rule substituting @file{/usr/source} into
8114 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
8115 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
8116 is applied only at the beginning of the directory name, this rule will
8117 not be applied to @file{/root/usr/source/baz.c} either.
8119 In many cases, you can achieve the same result using the @code{directory}
8120 command. However, @code{set substitute-path} can be more efficient in
8121 the case where the sources are organized in a complex tree with multiple
8122 subdirectories. With the @code{directory} command, you need to add each
8123 subdirectory of your project. If you moved the entire tree while
8124 preserving its internal organization, then @code{set substitute-path}
8125 allows you to direct the debugger to all the sources with one single
8128 @code{set substitute-path} is also more than just a shortcut command.
8129 The source path is only used if the file at the original location no
8130 longer exists. On the other hand, @code{set substitute-path} modifies
8131 the debugger behavior to look at the rewritten location instead. So, if
8132 for any reason a source file that is not relevant to your executable is
8133 located at the original location, a substitution rule is the only
8134 method available to point @value{GDBN} at the new location.
8136 @cindex @samp{--with-relocated-sources}
8137 @cindex default source path substitution
8138 You can configure a default source path substitution rule by
8139 configuring @value{GDBN} with the
8140 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
8141 should be the name of a directory under @value{GDBN}'s configured
8142 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
8143 directory names in debug information under @var{dir} will be adjusted
8144 automatically if the installed @value{GDBN} is moved to a new
8145 location. This is useful if @value{GDBN}, libraries or executables
8146 with debug information and corresponding source code are being moved
8150 @item directory @var{dirname} @dots{}
8151 @item dir @var{dirname} @dots{}
8152 Add directory @var{dirname} to the front of the source path. Several
8153 directory names may be given to this command, separated by @samp{:}
8154 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
8155 part of absolute file names) or
8156 whitespace. You may specify a directory that is already in the source
8157 path; this moves it forward, so @value{GDBN} searches it sooner.
8161 @vindex $cdir@r{, convenience variable}
8162 @vindex $cwd@r{, convenience variable}
8163 @cindex compilation directory
8164 @cindex current directory
8165 @cindex working directory
8166 @cindex directory, current
8167 @cindex directory, compilation
8168 You can use the string @samp{$cdir} to refer to the compilation
8169 directory (if one is recorded), and @samp{$cwd} to refer to the current
8170 working directory. @samp{$cwd} is not the same as @samp{.}---the former
8171 tracks the current working directory as it changes during your @value{GDBN}
8172 session, while the latter is immediately expanded to the current
8173 directory at the time you add an entry to the source path.
8176 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
8178 @c RET-repeat for @code{directory} is explicitly disabled, but since
8179 @c repeating it would be a no-op we do not say that. (thanks to RMS)
8181 @item set directories @var{path-list}
8182 @kindex set directories
8183 Set the source path to @var{path-list}.
8184 @samp{$cdir:$cwd} are added if missing.
8186 @item show directories
8187 @kindex show directories
8188 Print the source path: show which directories it contains.
8190 @anchor{set substitute-path}
8191 @item set substitute-path @var{from} @var{to}
8192 @kindex set substitute-path
8193 Define a source path substitution rule, and add it at the end of the
8194 current list of existing substitution rules. If a rule with the same
8195 @var{from} was already defined, then the old rule is also deleted.
8197 For example, if the file @file{/foo/bar/baz.c} was moved to
8198 @file{/mnt/cross/baz.c}, then the command
8201 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
8205 will tell @value{GDBN} to replace @samp{/foo/bar} with
8206 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
8207 @file{baz.c} even though it was moved.
8209 In the case when more than one substitution rule have been defined,
8210 the rules are evaluated one by one in the order where they have been
8211 defined. The first one matching, if any, is selected to perform
8214 For instance, if we had entered the following commands:
8217 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
8218 (@value{GDBP}) set substitute-path /usr/src /mnt/src
8222 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
8223 @file{/mnt/include/defs.h} by using the first rule. However, it would
8224 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
8225 @file{/mnt/src/lib/foo.c}.
8228 @item unset substitute-path [path]
8229 @kindex unset substitute-path
8230 If a path is specified, search the current list of substitution rules
8231 for a rule that would rewrite that path. Delete that rule if found.
8232 A warning is emitted by the debugger if no rule could be found.
8234 If no path is specified, then all substitution rules are deleted.
8236 @item show substitute-path [path]
8237 @kindex show substitute-path
8238 If a path is specified, then print the source path substitution rule
8239 which would rewrite that path, if any.
8241 If no path is specified, then print all existing source path substitution
8246 If your source path is cluttered with directories that are no longer of
8247 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
8248 versions of source. You can correct the situation as follows:
8252 Use @code{directory} with no argument to reset the source path to its default value.
8255 Use @code{directory} with suitable arguments to reinstall the
8256 directories you want in the source path. You can add all the
8257 directories in one command.
8261 @section Source and Machine Code
8262 @cindex source line and its code address
8264 You can use the command @code{info line} to map source lines to program
8265 addresses (and vice versa), and the command @code{disassemble} to display
8266 a range of addresses as machine instructions. You can use the command
8267 @code{set disassemble-next-line} to set whether to disassemble next
8268 source line when execution stops. When run under @sc{gnu} Emacs
8269 mode, the @code{info line} command causes the arrow to point to the
8270 line specified. Also, @code{info line} prints addresses in symbolic form as
8275 @item info line @var{location}
8276 Print the starting and ending addresses of the compiled code for
8277 source line @var{location}. You can specify source lines in any of
8278 the ways documented in @ref{Specify Location}.
8281 For example, we can use @code{info line} to discover the location of
8282 the object code for the first line of function
8283 @code{m4_changequote}:
8285 @c FIXME: I think this example should also show the addresses in
8286 @c symbolic form, as they usually would be displayed.
8288 (@value{GDBP}) info line m4_changequote
8289 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
8293 @cindex code address and its source line
8294 We can also inquire (using @code{*@var{addr}} as the form for
8295 @var{location}) what source line covers a particular address:
8297 (@value{GDBP}) info line *0x63ff
8298 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
8301 @cindex @code{$_} and @code{info line}
8302 @cindex @code{x} command, default address
8303 @kindex x@r{(examine), and} info line
8304 After @code{info line}, the default address for the @code{x} command
8305 is changed to the starting address of the line, so that @samp{x/i} is
8306 sufficient to begin examining the machine code (@pxref{Memory,
8307 ,Examining Memory}). Also, this address is saved as the value of the
8308 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
8313 @cindex assembly instructions
8314 @cindex instructions, assembly
8315 @cindex machine instructions
8316 @cindex listing machine instructions
8318 @itemx disassemble /m
8319 @itemx disassemble /s
8320 @itemx disassemble /r
8321 This specialized command dumps a range of memory as machine
8322 instructions. It can also print mixed source+disassembly by specifying
8323 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
8324 as well as in symbolic form by specifying the @code{/r} modifier.
8325 The default memory range is the function surrounding the
8326 program counter of the selected frame. A single argument to this
8327 command is a program counter value; @value{GDBN} dumps the function
8328 surrounding this value. When two arguments are given, they should
8329 be separated by a comma, possibly surrounded by whitespace. The
8330 arguments specify a range of addresses to dump, in one of two forms:
8333 @item @var{start},@var{end}
8334 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
8335 @item @var{start},+@var{length}
8336 the addresses from @var{start} (inclusive) to
8337 @code{@var{start}+@var{length}} (exclusive).
8341 When 2 arguments are specified, the name of the function is also
8342 printed (since there could be several functions in the given range).
8344 The argument(s) can be any expression yielding a numeric value, such as
8345 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
8347 If the range of memory being disassembled contains current program counter,
8348 the instruction at that location is shown with a @code{=>} marker.
8351 The following example shows the disassembly of a range of addresses of
8352 HP PA-RISC 2.0 code:
8355 (@value{GDBP}) disas 0x32c4, 0x32e4
8356 Dump of assembler code from 0x32c4 to 0x32e4:
8357 0x32c4 <main+204>: addil 0,dp
8358 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
8359 0x32cc <main+212>: ldil 0x3000,r31
8360 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
8361 0x32d4 <main+220>: ldo 0(r31),rp
8362 0x32d8 <main+224>: addil -0x800,dp
8363 0x32dc <main+228>: ldo 0x588(r1),r26
8364 0x32e0 <main+232>: ldil 0x3000,r31
8365 End of assembler dump.
8368 Here is an example showing mixed source+assembly for Intel x86
8369 with @code{/m} or @code{/s}, when the program is stopped just after
8370 function prologue in a non-optimized function with no inline code.
8373 (@value{GDBP}) disas /m main
8374 Dump of assembler code for function main:
8376 0x08048330 <+0>: push %ebp
8377 0x08048331 <+1>: mov %esp,%ebp
8378 0x08048333 <+3>: sub $0x8,%esp
8379 0x08048336 <+6>: and $0xfffffff0,%esp
8380 0x08048339 <+9>: sub $0x10,%esp
8382 6 printf ("Hello.\n");
8383 => 0x0804833c <+12>: movl $0x8048440,(%esp)
8384 0x08048343 <+19>: call 0x8048284 <puts@@plt>
8388 0x08048348 <+24>: mov $0x0,%eax
8389 0x0804834d <+29>: leave
8390 0x0804834e <+30>: ret
8392 End of assembler dump.
8395 The @code{/m} option is deprecated as its output is not useful when
8396 there is either inlined code or re-ordered code.
8397 The @code{/s} option is the preferred choice.
8398 Here is an example for AMD x86-64 showing the difference between
8399 @code{/m} output and @code{/s} output.
8400 This example has one inline function defined in a header file,
8401 and the code is compiled with @samp{-O2} optimization.
8402 Note how the @code{/m} output is missing the disassembly of
8403 several instructions that are present in the @code{/s} output.
8433 (@value{GDBP}) disas /m main
8434 Dump of assembler code for function main:
8438 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8439 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8443 0x000000000040041d <+29>: xor %eax,%eax
8444 0x000000000040041f <+31>: retq
8445 0x0000000000400420 <+32>: add %eax,%eax
8446 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8448 End of assembler dump.
8449 (@value{GDBP}) disas /s main
8450 Dump of assembler code for function main:
8454 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8458 0x0000000000400406 <+6>: test %eax,%eax
8459 0x0000000000400408 <+8>: js 0x400420 <main+32>
8464 0x000000000040040a <+10>: lea 0xa(%rax),%edx
8465 0x000000000040040d <+13>: test %eax,%eax
8466 0x000000000040040f <+15>: mov $0x1,%eax
8467 0x0000000000400414 <+20>: cmovne %edx,%eax
8471 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8475 0x000000000040041d <+29>: xor %eax,%eax
8476 0x000000000040041f <+31>: retq
8480 0x0000000000400420 <+32>: add %eax,%eax
8481 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8482 End of assembler dump.
8485 Here is another example showing raw instructions in hex for AMD x86-64,
8488 (gdb) disas /r 0x400281,+10
8489 Dump of assembler code from 0x400281 to 0x40028b:
8490 0x0000000000400281: 38 36 cmp %dh,(%rsi)
8491 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
8492 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
8493 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
8494 End of assembler dump.
8497 Addresses cannot be specified as a location (@pxref{Specify Location}).
8498 So, for example, if you want to disassemble function @code{bar}
8499 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
8500 and not @samp{disassemble foo.c:bar}.
8502 Some architectures have more than one commonly-used set of instruction
8503 mnemonics or other syntax.
8505 For programs that were dynamically linked and use shared libraries,
8506 instructions that call functions or branch to locations in the shared
8507 libraries might show a seemingly bogus location---it's actually a
8508 location of the relocation table. On some architectures, @value{GDBN}
8509 might be able to resolve these to actual function names.
8512 @kindex set disassembly-flavor
8513 @cindex Intel disassembly flavor
8514 @cindex AT&T disassembly flavor
8515 @item set disassembly-flavor @var{instruction-set}
8516 Select the instruction set to use when disassembling the
8517 program via the @code{disassemble} or @code{x/i} commands.
8519 Currently this command is only defined for the Intel x86 family. You
8520 can set @var{instruction-set} to either @code{intel} or @code{att}.
8521 The default is @code{att}, the AT&T flavor used by default by Unix
8522 assemblers for x86-based targets.
8524 @kindex show disassembly-flavor
8525 @item show disassembly-flavor
8526 Show the current setting of the disassembly flavor.
8530 @kindex set disassemble-next-line
8531 @kindex show disassemble-next-line
8532 @item set disassemble-next-line
8533 @itemx show disassemble-next-line
8534 Control whether or not @value{GDBN} will disassemble the next source
8535 line or instruction when execution stops. If ON, @value{GDBN} will
8536 display disassembly of the next source line when execution of the
8537 program being debugged stops. This is @emph{in addition} to
8538 displaying the source line itself, which @value{GDBN} always does if
8539 possible. If the next source line cannot be displayed for some reason
8540 (e.g., if @value{GDBN} cannot find the source file, or there's no line
8541 info in the debug info), @value{GDBN} will display disassembly of the
8542 next @emph{instruction} instead of showing the next source line. If
8543 AUTO, @value{GDBN} will display disassembly of next instruction only
8544 if the source line cannot be displayed. This setting causes
8545 @value{GDBN} to display some feedback when you step through a function
8546 with no line info or whose source file is unavailable. The default is
8547 OFF, which means never display the disassembly of the next line or
8553 @chapter Examining Data
8555 @cindex printing data
8556 @cindex examining data
8559 The usual way to examine data in your program is with the @code{print}
8560 command (abbreviated @code{p}), or its synonym @code{inspect}. It
8561 evaluates and prints the value of an expression of the language your
8562 program is written in (@pxref{Languages, ,Using @value{GDBN} with
8563 Different Languages}). It may also print the expression using a
8564 Python-based pretty-printer (@pxref{Pretty Printing}).
8567 @item print @var{expr}
8568 @itemx print /@var{f} @var{expr}
8569 @var{expr} is an expression (in the source language). By default the
8570 value of @var{expr} is printed in a format appropriate to its data type;
8571 you can choose a different format by specifying @samp{/@var{f}}, where
8572 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
8576 @itemx print /@var{f}
8577 @cindex reprint the last value
8578 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
8579 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
8580 conveniently inspect the same value in an alternative format.
8583 A more low-level way of examining data is with the @code{x} command.
8584 It examines data in memory at a specified address and prints it in a
8585 specified format. @xref{Memory, ,Examining Memory}.
8587 If you are interested in information about types, or about how the
8588 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
8589 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
8592 @cindex exploring hierarchical data structures
8594 Another way of examining values of expressions and type information is
8595 through the Python extension command @code{explore} (available only if
8596 the @value{GDBN} build is configured with @code{--with-python}). It
8597 offers an interactive way to start at the highest level (or, the most
8598 abstract level) of the data type of an expression (or, the data type
8599 itself) and explore all the way down to leaf scalar values/fields
8600 embedded in the higher level data types.
8603 @item explore @var{arg}
8604 @var{arg} is either an expression (in the source language), or a type
8605 visible in the current context of the program being debugged.
8608 The working of the @code{explore} command can be illustrated with an
8609 example. If a data type @code{struct ComplexStruct} is defined in your
8619 struct ComplexStruct
8621 struct SimpleStruct *ss_p;
8627 followed by variable declarations as
8630 struct SimpleStruct ss = @{ 10, 1.11 @};
8631 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
8635 then, the value of the variable @code{cs} can be explored using the
8636 @code{explore} command as follows.
8640 The value of `cs' is a struct/class of type `struct ComplexStruct' with
8641 the following fields:
8643 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
8644 arr = <Enter 1 to explore this field of type `int [10]'>
8646 Enter the field number of choice:
8650 Since the fields of @code{cs} are not scalar values, you are being
8651 prompted to chose the field you want to explore. Let's say you choose
8652 the field @code{ss_p} by entering @code{0}. Then, since this field is a
8653 pointer, you will be asked if it is pointing to a single value. From
8654 the declaration of @code{cs} above, it is indeed pointing to a single
8655 value, hence you enter @code{y}. If you enter @code{n}, then you will
8656 be asked if it were pointing to an array of values, in which case this
8657 field will be explored as if it were an array.
8660 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
8661 Continue exploring it as a pointer to a single value [y/n]: y
8662 The value of `*(cs.ss_p)' is a struct/class of type `struct
8663 SimpleStruct' with the following fields:
8665 i = 10 .. (Value of type `int')
8666 d = 1.1100000000000001 .. (Value of type `double')
8668 Press enter to return to parent value:
8672 If the field @code{arr} of @code{cs} was chosen for exploration by
8673 entering @code{1} earlier, then since it is as array, you will be
8674 prompted to enter the index of the element in the array that you want
8678 `cs.arr' is an array of `int'.
8679 Enter the index of the element you want to explore in `cs.arr': 5
8681 `(cs.arr)[5]' is a scalar value of type `int'.
8685 Press enter to return to parent value:
8688 In general, at any stage of exploration, you can go deeper towards the
8689 leaf values by responding to the prompts appropriately, or hit the
8690 return key to return to the enclosing data structure (the @i{higher}
8691 level data structure).
8693 Similar to exploring values, you can use the @code{explore} command to
8694 explore types. Instead of specifying a value (which is typically a
8695 variable name or an expression valid in the current context of the
8696 program being debugged), you specify a type name. If you consider the
8697 same example as above, your can explore the type
8698 @code{struct ComplexStruct} by passing the argument
8699 @code{struct ComplexStruct} to the @code{explore} command.
8702 (gdb) explore struct ComplexStruct
8706 By responding to the prompts appropriately in the subsequent interactive
8707 session, you can explore the type @code{struct ComplexStruct} in a
8708 manner similar to how the value @code{cs} was explored in the above
8711 The @code{explore} command also has two sub-commands,
8712 @code{explore value} and @code{explore type}. The former sub-command is
8713 a way to explicitly specify that value exploration of the argument is
8714 being invoked, while the latter is a way to explicitly specify that type
8715 exploration of the argument is being invoked.
8718 @item explore value @var{expr}
8719 @cindex explore value
8720 This sub-command of @code{explore} explores the value of the
8721 expression @var{expr} (if @var{expr} is an expression valid in the
8722 current context of the program being debugged). The behavior of this
8723 command is identical to that of the behavior of the @code{explore}
8724 command being passed the argument @var{expr}.
8726 @item explore type @var{arg}
8727 @cindex explore type
8728 This sub-command of @code{explore} explores the type of @var{arg} (if
8729 @var{arg} is a type visible in the current context of program being
8730 debugged), or the type of the value/expression @var{arg} (if @var{arg}
8731 is an expression valid in the current context of the program being
8732 debugged). If @var{arg} is a type, then the behavior of this command is
8733 identical to that of the @code{explore} command being passed the
8734 argument @var{arg}. If @var{arg} is an expression, then the behavior of
8735 this command will be identical to that of the @code{explore} command
8736 being passed the type of @var{arg} as the argument.
8740 * Expressions:: Expressions
8741 * Ambiguous Expressions:: Ambiguous Expressions
8742 * Variables:: Program variables
8743 * Arrays:: Artificial arrays
8744 * Output Formats:: Output formats
8745 * Memory:: Examining memory
8746 * Auto Display:: Automatic display
8747 * Print Settings:: Print settings
8748 * Pretty Printing:: Python pretty printing
8749 * Value History:: Value history
8750 * Convenience Vars:: Convenience variables
8751 * Convenience Funs:: Convenience functions
8752 * Registers:: Registers
8753 * Floating Point Hardware:: Floating point hardware
8754 * Vector Unit:: Vector Unit
8755 * OS Information:: Auxiliary data provided by operating system
8756 * Memory Region Attributes:: Memory region attributes
8757 * Dump/Restore Files:: Copy between memory and a file
8758 * Core File Generation:: Cause a program dump its core
8759 * Character Sets:: Debugging programs that use a different
8760 character set than GDB does
8761 * Caching Target Data:: Data caching for targets
8762 * Searching Memory:: Searching memory for a sequence of bytes
8763 * Value Sizes:: Managing memory allocated for values
8767 @section Expressions
8770 @code{print} and many other @value{GDBN} commands accept an expression and
8771 compute its value. Any kind of constant, variable or operator defined
8772 by the programming language you are using is valid in an expression in
8773 @value{GDBN}. This includes conditional expressions, function calls,
8774 casts, and string constants. It also includes preprocessor macros, if
8775 you compiled your program to include this information; see
8778 @cindex arrays in expressions
8779 @value{GDBN} supports array constants in expressions input by
8780 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
8781 you can use the command @code{print @{1, 2, 3@}} to create an array
8782 of three integers. If you pass an array to a function or assign it
8783 to a program variable, @value{GDBN} copies the array to memory that
8784 is @code{malloc}ed in the target program.
8786 Because C is so widespread, most of the expressions shown in examples in
8787 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
8788 Languages}, for information on how to use expressions in other
8791 In this section, we discuss operators that you can use in @value{GDBN}
8792 expressions regardless of your programming language.
8794 @cindex casts, in expressions
8795 Casts are supported in all languages, not just in C, because it is so
8796 useful to cast a number into a pointer in order to examine a structure
8797 at that address in memory.
8798 @c FIXME: casts supported---Mod2 true?
8800 @value{GDBN} supports these operators, in addition to those common
8801 to programming languages:
8805 @samp{@@} is a binary operator for treating parts of memory as arrays.
8806 @xref{Arrays, ,Artificial Arrays}, for more information.
8809 @samp{::} allows you to specify a variable in terms of the file or
8810 function where it is defined. @xref{Variables, ,Program Variables}.
8812 @cindex @{@var{type}@}
8813 @cindex type casting memory
8814 @cindex memory, viewing as typed object
8815 @cindex casts, to view memory
8816 @item @{@var{type}@} @var{addr}
8817 Refers to an object of type @var{type} stored at address @var{addr} in
8818 memory. The address @var{addr} may be any expression whose value is
8819 an integer or pointer (but parentheses are required around binary
8820 operators, just as in a cast). This construct is allowed regardless
8821 of what kind of data is normally supposed to reside at @var{addr}.
8824 @node Ambiguous Expressions
8825 @section Ambiguous Expressions
8826 @cindex ambiguous expressions
8828 Expressions can sometimes contain some ambiguous elements. For instance,
8829 some programming languages (notably Ada, C@t{++} and Objective-C) permit
8830 a single function name to be defined several times, for application in
8831 different contexts. This is called @dfn{overloading}. Another example
8832 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
8833 templates and is typically instantiated several times, resulting in
8834 the same function name being defined in different contexts.
8836 In some cases and depending on the language, it is possible to adjust
8837 the expression to remove the ambiguity. For instance in C@t{++}, you
8838 can specify the signature of the function you want to break on, as in
8839 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
8840 qualified name of your function often makes the expression unambiguous
8843 When an ambiguity that needs to be resolved is detected, the debugger
8844 has the capability to display a menu of numbered choices for each
8845 possibility, and then waits for the selection with the prompt @samp{>}.
8846 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
8847 aborts the current command. If the command in which the expression was
8848 used allows more than one choice to be selected, the next option in the
8849 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
8852 For example, the following session excerpt shows an attempt to set a
8853 breakpoint at the overloaded symbol @code{String::after}.
8854 We choose three particular definitions of that function name:
8856 @c FIXME! This is likely to change to show arg type lists, at least
8859 (@value{GDBP}) b String::after
8862 [2] file:String.cc; line number:867
8863 [3] file:String.cc; line number:860
8864 [4] file:String.cc; line number:875
8865 [5] file:String.cc; line number:853
8866 [6] file:String.cc; line number:846
8867 [7] file:String.cc; line number:735
8869 Breakpoint 1 at 0xb26c: file String.cc, line 867.
8870 Breakpoint 2 at 0xb344: file String.cc, line 875.
8871 Breakpoint 3 at 0xafcc: file String.cc, line 846.
8872 Multiple breakpoints were set.
8873 Use the "delete" command to delete unwanted
8880 @kindex set multiple-symbols
8881 @item set multiple-symbols @var{mode}
8882 @cindex multiple-symbols menu
8884 This option allows you to adjust the debugger behavior when an expression
8887 By default, @var{mode} is set to @code{all}. If the command with which
8888 the expression is used allows more than one choice, then @value{GDBN}
8889 automatically selects all possible choices. For instance, inserting
8890 a breakpoint on a function using an ambiguous name results in a breakpoint
8891 inserted on each possible match. However, if a unique choice must be made,
8892 then @value{GDBN} uses the menu to help you disambiguate the expression.
8893 For instance, printing the address of an overloaded function will result
8894 in the use of the menu.
8896 When @var{mode} is set to @code{ask}, the debugger always uses the menu
8897 when an ambiguity is detected.
8899 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
8900 an error due to the ambiguity and the command is aborted.
8902 @kindex show multiple-symbols
8903 @item show multiple-symbols
8904 Show the current value of the @code{multiple-symbols} setting.
8908 @section Program Variables
8910 The most common kind of expression to use is the name of a variable
8913 Variables in expressions are understood in the selected stack frame
8914 (@pxref{Selection, ,Selecting a Frame}); they must be either:
8918 global (or file-static)
8925 visible according to the scope rules of the
8926 programming language from the point of execution in that frame
8929 @noindent This means that in the function
8944 you can examine and use the variable @code{a} whenever your program is
8945 executing within the function @code{foo}, but you can only use or
8946 examine the variable @code{b} while your program is executing inside
8947 the block where @code{b} is declared.
8949 @cindex variable name conflict
8950 There is an exception: you can refer to a variable or function whose
8951 scope is a single source file even if the current execution point is not
8952 in this file. But it is possible to have more than one such variable or
8953 function with the same name (in different source files). If that
8954 happens, referring to that name has unpredictable effects. If you wish,
8955 you can specify a static variable in a particular function or file by
8956 using the colon-colon (@code{::}) notation:
8958 @cindex colon-colon, context for variables/functions
8960 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
8961 @cindex @code{::}, context for variables/functions
8964 @var{file}::@var{variable}
8965 @var{function}::@var{variable}
8969 Here @var{file} or @var{function} is the name of the context for the
8970 static @var{variable}. In the case of file names, you can use quotes to
8971 make sure @value{GDBN} parses the file name as a single word---for example,
8972 to print a global value of @code{x} defined in @file{f2.c}:
8975 (@value{GDBP}) p 'f2.c'::x
8978 The @code{::} notation is normally used for referring to
8979 static variables, since you typically disambiguate uses of local variables
8980 in functions by selecting the appropriate frame and using the
8981 simple name of the variable. However, you may also use this notation
8982 to refer to local variables in frames enclosing the selected frame:
8991 process (a); /* Stop here */
9002 For example, if there is a breakpoint at the commented line,
9003 here is what you might see
9004 when the program stops after executing the call @code{bar(0)}:
9009 (@value{GDBP}) p bar::a
9012 #2 0x080483d0 in foo (a=5) at foobar.c:12
9015 (@value{GDBP}) p bar::a
9019 @cindex C@t{++} scope resolution
9020 These uses of @samp{::} are very rarely in conflict with the very
9021 similar use of the same notation in C@t{++}. When they are in
9022 conflict, the C@t{++} meaning takes precedence; however, this can be
9023 overridden by quoting the file or function name with single quotes.
9025 For example, suppose the program is stopped in a method of a class
9026 that has a field named @code{includefile}, and there is also an
9027 include file named @file{includefile} that defines a variable,
9031 (@value{GDBP}) p includefile
9033 (@value{GDBP}) p includefile::some_global
9034 A syntax error in expression, near `'.
9035 (@value{GDBP}) p 'includefile'::some_global
9039 @cindex wrong values
9040 @cindex variable values, wrong
9041 @cindex function entry/exit, wrong values of variables
9042 @cindex optimized code, wrong values of variables
9044 @emph{Warning:} Occasionally, a local variable may appear to have the
9045 wrong value at certain points in a function---just after entry to a new
9046 scope, and just before exit.
9048 You may see this problem when you are stepping by machine instructions.
9049 This is because, on most machines, it takes more than one instruction to
9050 set up a stack frame (including local variable definitions); if you are
9051 stepping by machine instructions, variables may appear to have the wrong
9052 values until the stack frame is completely built. On exit, it usually
9053 also takes more than one machine instruction to destroy a stack frame;
9054 after you begin stepping through that group of instructions, local
9055 variable definitions may be gone.
9057 This may also happen when the compiler does significant optimizations.
9058 To be sure of always seeing accurate values, turn off all optimization
9061 @cindex ``No symbol "foo" in current context''
9062 Another possible effect of compiler optimizations is to optimize
9063 unused variables out of existence, or assign variables to registers (as
9064 opposed to memory addresses). Depending on the support for such cases
9065 offered by the debug info format used by the compiler, @value{GDBN}
9066 might not be able to display values for such local variables. If that
9067 happens, @value{GDBN} will print a message like this:
9070 No symbol "foo" in current context.
9073 To solve such problems, either recompile without optimizations, or use a
9074 different debug info format, if the compiler supports several such
9075 formats. @xref{Compilation}, for more information on choosing compiler
9076 options. @xref{C, ,C and C@t{++}}, for more information about debug
9077 info formats that are best suited to C@t{++} programs.
9079 If you ask to print an object whose contents are unknown to
9080 @value{GDBN}, e.g., because its data type is not completely specified
9081 by the debug information, @value{GDBN} will say @samp{<incomplete
9082 type>}. @xref{Symbols, incomplete type}, for more about this.
9084 If you append @kbd{@@entry} string to a function parameter name you get its
9085 value at the time the function got called. If the value is not available an
9086 error message is printed. Entry values are available only with some compilers.
9087 Entry values are normally also printed at the function parameter list according
9088 to @ref{set print entry-values}.
9091 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
9097 (gdb) print i@@entry
9101 Strings are identified as arrays of @code{char} values without specified
9102 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
9103 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
9104 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
9105 defines literal string type @code{"char"} as @code{char} without a sign.
9110 signed char var1[] = "A";
9113 You get during debugging
9118 $2 = @{65 'A', 0 '\0'@}
9122 @section Artificial Arrays
9124 @cindex artificial array
9126 @kindex @@@r{, referencing memory as an array}
9127 It is often useful to print out several successive objects of the
9128 same type in memory; a section of an array, or an array of
9129 dynamically determined size for which only a pointer exists in the
9132 You can do this by referring to a contiguous span of memory as an
9133 @dfn{artificial array}, using the binary operator @samp{@@}. The left
9134 operand of @samp{@@} should be the first element of the desired array
9135 and be an individual object. The right operand should be the desired length
9136 of the array. The result is an array value whose elements are all of
9137 the type of the left argument. The first element is actually the left
9138 argument; the second element comes from bytes of memory immediately
9139 following those that hold the first element, and so on. Here is an
9140 example. If a program says
9143 int *array = (int *) malloc (len * sizeof (int));
9147 you can print the contents of @code{array} with
9153 The left operand of @samp{@@} must reside in memory. Array values made
9154 with @samp{@@} in this way behave just like other arrays in terms of
9155 subscripting, and are coerced to pointers when used in expressions.
9156 Artificial arrays most often appear in expressions via the value history
9157 (@pxref{Value History, ,Value History}), after printing one out.
9159 Another way to create an artificial array is to use a cast.
9160 This re-interprets a value as if it were an array.
9161 The value need not be in memory:
9163 (@value{GDBP}) p/x (short[2])0x12345678
9164 $1 = @{0x1234, 0x5678@}
9167 As a convenience, if you leave the array length out (as in
9168 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
9169 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
9171 (@value{GDBP}) p/x (short[])0x12345678
9172 $2 = @{0x1234, 0x5678@}
9175 Sometimes the artificial array mechanism is not quite enough; in
9176 moderately complex data structures, the elements of interest may not
9177 actually be adjacent---for example, if you are interested in the values
9178 of pointers in an array. One useful work-around in this situation is
9179 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
9180 Variables}) as a counter in an expression that prints the first
9181 interesting value, and then repeat that expression via @key{RET}. For
9182 instance, suppose you have an array @code{dtab} of pointers to
9183 structures, and you are interested in the values of a field @code{fv}
9184 in each structure. Here is an example of what you might type:
9194 @node Output Formats
9195 @section Output Formats
9197 @cindex formatted output
9198 @cindex output formats
9199 By default, @value{GDBN} prints a value according to its data type. Sometimes
9200 this is not what you want. For example, you might want to print a number
9201 in hex, or a pointer in decimal. Or you might want to view data in memory
9202 at a certain address as a character string or as an instruction. To do
9203 these things, specify an @dfn{output format} when you print a value.
9205 The simplest use of output formats is to say how to print a value
9206 already computed. This is done by starting the arguments of the
9207 @code{print} command with a slash and a format letter. The format
9208 letters supported are:
9212 Regard the bits of the value as an integer, and print the integer in
9216 Print as integer in signed decimal.
9219 Print as integer in unsigned decimal.
9222 Print as integer in octal.
9225 Print as integer in binary. The letter @samp{t} stands for ``two''.
9226 @footnote{@samp{b} cannot be used because these format letters are also
9227 used with the @code{x} command, where @samp{b} stands for ``byte'';
9228 see @ref{Memory,,Examining Memory}.}
9231 @cindex unknown address, locating
9232 @cindex locate address
9233 Print as an address, both absolute in hexadecimal and as an offset from
9234 the nearest preceding symbol. You can use this format used to discover
9235 where (in what function) an unknown address is located:
9238 (@value{GDBP}) p/a 0x54320
9239 $3 = 0x54320 <_initialize_vx+396>
9243 The command @code{info symbol 0x54320} yields similar results.
9244 @xref{Symbols, info symbol}.
9247 Regard as an integer and print it as a character constant. This
9248 prints both the numerical value and its character representation. The
9249 character representation is replaced with the octal escape @samp{\nnn}
9250 for characters outside the 7-bit @sc{ascii} range.
9252 Without this format, @value{GDBN} displays @code{char},
9253 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
9254 constants. Single-byte members of vectors are displayed as integer
9258 Regard the bits of the value as a floating point number and print
9259 using typical floating point syntax.
9262 @cindex printing strings
9263 @cindex printing byte arrays
9264 Regard as a string, if possible. With this format, pointers to single-byte
9265 data are displayed as null-terminated strings and arrays of single-byte data
9266 are displayed as fixed-length strings. Other values are displayed in their
9269 Without this format, @value{GDBN} displays pointers to and arrays of
9270 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
9271 strings. Single-byte members of a vector are displayed as an integer
9275 Like @samp{x} formatting, the value is treated as an integer and
9276 printed as hexadecimal, but leading zeros are printed to pad the value
9277 to the size of the integer type.
9280 @cindex raw printing
9281 Print using the @samp{raw} formatting. By default, @value{GDBN} will
9282 use a Python-based pretty-printer, if one is available (@pxref{Pretty
9283 Printing}). This typically results in a higher-level display of the
9284 value's contents. The @samp{r} format bypasses any Python
9285 pretty-printer which might exist.
9288 For example, to print the program counter in hex (@pxref{Registers}), type
9295 Note that no space is required before the slash; this is because command
9296 names in @value{GDBN} cannot contain a slash.
9298 To reprint the last value in the value history with a different format,
9299 you can use the @code{print} command with just a format and no
9300 expression. For example, @samp{p/x} reprints the last value in hex.
9303 @section Examining Memory
9305 You can use the command @code{x} (for ``examine'') to examine memory in
9306 any of several formats, independently of your program's data types.
9308 @cindex examining memory
9310 @kindex x @r{(examine memory)}
9311 @item x/@var{nfu} @var{addr}
9314 Use the @code{x} command to examine memory.
9317 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
9318 much memory to display and how to format it; @var{addr} is an
9319 expression giving the address where you want to start displaying memory.
9320 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
9321 Several commands set convenient defaults for @var{addr}.
9324 @item @var{n}, the repeat count
9325 The repeat count is a decimal integer; the default is 1. It specifies
9326 how much memory (counting by units @var{u}) to display. If a negative
9327 number is specified, memory is examined backward from @var{addr}.
9328 @c This really is **decimal**; unaffected by 'set radix' as of GDB
9331 @item @var{f}, the display format
9332 The display format is one of the formats used by @code{print}
9333 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
9334 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
9335 The default is @samp{x} (hexadecimal) initially. The default changes
9336 each time you use either @code{x} or @code{print}.
9338 @item @var{u}, the unit size
9339 The unit size is any of
9345 Halfwords (two bytes).
9347 Words (four bytes). This is the initial default.
9349 Giant words (eight bytes).
9352 Each time you specify a unit size with @code{x}, that size becomes the
9353 default unit the next time you use @code{x}. For the @samp{i} format,
9354 the unit size is ignored and is normally not written. For the @samp{s} format,
9355 the unit size defaults to @samp{b}, unless it is explicitly given.
9356 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
9357 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
9358 Note that the results depend on the programming language of the
9359 current compilation unit. If the language is C, the @samp{s}
9360 modifier will use the UTF-16 encoding while @samp{w} will use
9361 UTF-32. The encoding is set by the programming language and cannot
9364 @item @var{addr}, starting display address
9365 @var{addr} is the address where you want @value{GDBN} to begin displaying
9366 memory. The expression need not have a pointer value (though it may);
9367 it is always interpreted as an integer address of a byte of memory.
9368 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
9369 @var{addr} is usually just after the last address examined---but several
9370 other commands also set the default address: @code{info breakpoints} (to
9371 the address of the last breakpoint listed), @code{info line} (to the
9372 starting address of a line), and @code{print} (if you use it to display
9373 a value from memory).
9376 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
9377 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
9378 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
9379 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
9380 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
9382 You can also specify a negative repeat count to examine memory backward
9383 from the given address. For example, @samp{x/-3uh 0x54320} prints three
9384 halfwords (@code{h}) at @code{0x54314}, @code{0x54328}, and @code{0x5431c}.
9386 Since the letters indicating unit sizes are all distinct from the
9387 letters specifying output formats, you do not have to remember whether
9388 unit size or format comes first; either order works. The output
9389 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
9390 (However, the count @var{n} must come first; @samp{wx4} does not work.)
9392 Even though the unit size @var{u} is ignored for the formats @samp{s}
9393 and @samp{i}, you might still want to use a count @var{n}; for example,
9394 @samp{3i} specifies that you want to see three machine instructions,
9395 including any operands. For convenience, especially when used with
9396 the @code{display} command, the @samp{i} format also prints branch delay
9397 slot instructions, if any, beyond the count specified, which immediately
9398 follow the last instruction that is within the count. The command
9399 @code{disassemble} gives an alternative way of inspecting machine
9400 instructions; see @ref{Machine Code,,Source and Machine Code}.
9402 If a negative repeat count is specified for the formats @samp{s} or @samp{i},
9403 the command displays null-terminated strings or instructions before the given
9404 address as many as the absolute value of the given number. For the @samp{i}
9405 format, we use line number information in the debug info to accurately locate
9406 instruction boundaries while disassembling backward. If line info is not
9407 available, the command stops examining memory with an error message.
9409 All the defaults for the arguments to @code{x} are designed to make it
9410 easy to continue scanning memory with minimal specifications each time
9411 you use @code{x}. For example, after you have inspected three machine
9412 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
9413 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
9414 the repeat count @var{n} is used again; the other arguments default as
9415 for successive uses of @code{x}.
9417 When examining machine instructions, the instruction at current program
9418 counter is shown with a @code{=>} marker. For example:
9421 (@value{GDBP}) x/5i $pc-6
9422 0x804837f <main+11>: mov %esp,%ebp
9423 0x8048381 <main+13>: push %ecx
9424 0x8048382 <main+14>: sub $0x4,%esp
9425 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
9426 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
9429 @cindex @code{$_}, @code{$__}, and value history
9430 The addresses and contents printed by the @code{x} command are not saved
9431 in the value history because there is often too much of them and they
9432 would get in the way. Instead, @value{GDBN} makes these values available for
9433 subsequent use in expressions as values of the convenience variables
9434 @code{$_} and @code{$__}. After an @code{x} command, the last address
9435 examined is available for use in expressions in the convenience variable
9436 @code{$_}. The contents of that address, as examined, are available in
9437 the convenience variable @code{$__}.
9439 If the @code{x} command has a repeat count, the address and contents saved
9440 are from the last memory unit printed; this is not the same as the last
9441 address printed if several units were printed on the last line of output.
9443 @anchor{addressable memory unit}
9444 @cindex addressable memory unit
9445 Most targets have an addressable memory unit size of 8 bits. This means
9446 that to each memory address are associated 8 bits of data. Some
9447 targets, however, have other addressable memory unit sizes.
9448 Within @value{GDBN} and this document, the term
9449 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
9450 when explicitly referring to a chunk of data of that size. The word
9451 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
9452 the addressable memory unit size of the target. For most systems,
9453 addressable memory unit is a synonym of byte.
9455 @cindex remote memory comparison
9456 @cindex target memory comparison
9457 @cindex verify remote memory image
9458 @cindex verify target memory image
9459 When you are debugging a program running on a remote target machine
9460 (@pxref{Remote Debugging}), you may wish to verify the program's image
9461 in the remote machine's memory against the executable file you
9462 downloaded to the target. Or, on any target, you may want to check
9463 whether the program has corrupted its own read-only sections. The
9464 @code{compare-sections} command is provided for such situations.
9467 @kindex compare-sections
9468 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
9469 Compare the data of a loadable section @var{section-name} in the
9470 executable file of the program being debugged with the same section in
9471 the target machine's memory, and report any mismatches. With no
9472 arguments, compares all loadable sections. With an argument of
9473 @code{-r}, compares all loadable read-only sections.
9475 Note: for remote targets, this command can be accelerated if the
9476 target supports computing the CRC checksum of a block of memory
9477 (@pxref{qCRC packet}).
9481 @section Automatic Display
9482 @cindex automatic display
9483 @cindex display of expressions
9485 If you find that you want to print the value of an expression frequently
9486 (to see how it changes), you might want to add it to the @dfn{automatic
9487 display list} so that @value{GDBN} prints its value each time your program stops.
9488 Each expression added to the list is given a number to identify it;
9489 to remove an expression from the list, you specify that number.
9490 The automatic display looks like this:
9494 3: bar[5] = (struct hack *) 0x3804
9498 This display shows item numbers, expressions and their current values. As with
9499 displays you request manually using @code{x} or @code{print}, you can
9500 specify the output format you prefer; in fact, @code{display} decides
9501 whether to use @code{print} or @code{x} depending your format
9502 specification---it uses @code{x} if you specify either the @samp{i}
9503 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
9507 @item display @var{expr}
9508 Add the expression @var{expr} to the list of expressions to display
9509 each time your program stops. @xref{Expressions, ,Expressions}.
9511 @code{display} does not repeat if you press @key{RET} again after using it.
9513 @item display/@var{fmt} @var{expr}
9514 For @var{fmt} specifying only a display format and not a size or
9515 count, add the expression @var{expr} to the auto-display list but
9516 arrange to display it each time in the specified format @var{fmt}.
9517 @xref{Output Formats,,Output Formats}.
9519 @item display/@var{fmt} @var{addr}
9520 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
9521 number of units, add the expression @var{addr} as a memory address to
9522 be examined each time your program stops. Examining means in effect
9523 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
9526 For example, @samp{display/i $pc} can be helpful, to see the machine
9527 instruction about to be executed each time execution stops (@samp{$pc}
9528 is a common name for the program counter; @pxref{Registers, ,Registers}).
9531 @kindex delete display
9533 @item undisplay @var{dnums}@dots{}
9534 @itemx delete display @var{dnums}@dots{}
9535 Remove items from the list of expressions to display. Specify the
9536 numbers of the displays that you want affected with the command
9537 argument @var{dnums}. It can be a single display number, one of the
9538 numbers shown in the first field of the @samp{info display} display;
9539 or it could be a range of display numbers, as in @code{2-4}.
9541 @code{undisplay} does not repeat if you press @key{RET} after using it.
9542 (Otherwise you would just get the error @samp{No display number @dots{}}.)
9544 @kindex disable display
9545 @item disable display @var{dnums}@dots{}
9546 Disable the display of item numbers @var{dnums}. A disabled display
9547 item is not printed automatically, but is not forgotten. It may be
9548 enabled again later. Specify the numbers of the displays that you
9549 want affected with the command argument @var{dnums}. It can be a
9550 single display number, one of the numbers shown in the first field of
9551 the @samp{info display} display; or it could be a range of display
9552 numbers, as in @code{2-4}.
9554 @kindex enable display
9555 @item enable display @var{dnums}@dots{}
9556 Enable display of item numbers @var{dnums}. It becomes effective once
9557 again in auto display of its expression, until you specify otherwise.
9558 Specify the numbers of the displays that you want affected with the
9559 command argument @var{dnums}. It can be a single display number, one
9560 of the numbers shown in the first field of the @samp{info display}
9561 display; or it could be a range of display numbers, as in @code{2-4}.
9564 Display the current values of the expressions on the list, just as is
9565 done when your program stops.
9567 @kindex info display
9569 Print the list of expressions previously set up to display
9570 automatically, each one with its item number, but without showing the
9571 values. This includes disabled expressions, which are marked as such.
9572 It also includes expressions which would not be displayed right now
9573 because they refer to automatic variables not currently available.
9576 @cindex display disabled out of scope
9577 If a display expression refers to local variables, then it does not make
9578 sense outside the lexical context for which it was set up. Such an
9579 expression is disabled when execution enters a context where one of its
9580 variables is not defined. For example, if you give the command
9581 @code{display last_char} while inside a function with an argument
9582 @code{last_char}, @value{GDBN} displays this argument while your program
9583 continues to stop inside that function. When it stops elsewhere---where
9584 there is no variable @code{last_char}---the display is disabled
9585 automatically. The next time your program stops where @code{last_char}
9586 is meaningful, you can enable the display expression once again.
9588 @node Print Settings
9589 @section Print Settings
9591 @cindex format options
9592 @cindex print settings
9593 @value{GDBN} provides the following ways to control how arrays, structures,
9594 and symbols are printed.
9597 These settings are useful for debugging programs in any language:
9601 @item set print address
9602 @itemx set print address on
9603 @cindex print/don't print memory addresses
9604 @value{GDBN} prints memory addresses showing the location of stack
9605 traces, structure values, pointer values, breakpoints, and so forth,
9606 even when it also displays the contents of those addresses. The default
9607 is @code{on}. For example, this is what a stack frame display looks like with
9608 @code{set print address on}:
9613 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
9615 530 if (lquote != def_lquote)
9619 @item set print address off
9620 Do not print addresses when displaying their contents. For example,
9621 this is the same stack frame displayed with @code{set print address off}:
9625 (@value{GDBP}) set print addr off
9627 #0 set_quotes (lq="<<", rq=">>") at input.c:530
9628 530 if (lquote != def_lquote)
9632 You can use @samp{set print address off} to eliminate all machine
9633 dependent displays from the @value{GDBN} interface. For example, with
9634 @code{print address off}, you should get the same text for backtraces on
9635 all machines---whether or not they involve pointer arguments.
9638 @item show print address
9639 Show whether or not addresses are to be printed.
9642 When @value{GDBN} prints a symbolic address, it normally prints the
9643 closest earlier symbol plus an offset. If that symbol does not uniquely
9644 identify the address (for example, it is a name whose scope is a single
9645 source file), you may need to clarify. One way to do this is with
9646 @code{info line}, for example @samp{info line *0x4537}. Alternately,
9647 you can set @value{GDBN} to print the source file and line number when
9648 it prints a symbolic address:
9651 @item set print symbol-filename on
9652 @cindex source file and line of a symbol
9653 @cindex symbol, source file and line
9654 Tell @value{GDBN} to print the source file name and line number of a
9655 symbol in the symbolic form of an address.
9657 @item set print symbol-filename off
9658 Do not print source file name and line number of a symbol. This is the
9661 @item show print symbol-filename
9662 Show whether or not @value{GDBN} will print the source file name and
9663 line number of a symbol in the symbolic form of an address.
9666 Another situation where it is helpful to show symbol filenames and line
9667 numbers is when disassembling code; @value{GDBN} shows you the line
9668 number and source file that corresponds to each instruction.
9670 Also, you may wish to see the symbolic form only if the address being
9671 printed is reasonably close to the closest earlier symbol:
9674 @item set print max-symbolic-offset @var{max-offset}
9675 @itemx set print max-symbolic-offset unlimited
9676 @cindex maximum value for offset of closest symbol
9677 Tell @value{GDBN} to only display the symbolic form of an address if the
9678 offset between the closest earlier symbol and the address is less than
9679 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
9680 to always print the symbolic form of an address if any symbol precedes
9681 it. Zero is equivalent to @code{unlimited}.
9683 @item show print max-symbolic-offset
9684 Ask how large the maximum offset is that @value{GDBN} prints in a
9688 @cindex wild pointer, interpreting
9689 @cindex pointer, finding referent
9690 If you have a pointer and you are not sure where it points, try
9691 @samp{set print symbol-filename on}. Then you can determine the name
9692 and source file location of the variable where it points, using
9693 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
9694 For example, here @value{GDBN} shows that a variable @code{ptt} points
9695 at another variable @code{t}, defined in @file{hi2.c}:
9698 (@value{GDBP}) set print symbol-filename on
9699 (@value{GDBP}) p/a ptt
9700 $4 = 0xe008 <t in hi2.c>
9704 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
9705 does not show the symbol name and filename of the referent, even with
9706 the appropriate @code{set print} options turned on.
9709 You can also enable @samp{/a}-like formatting all the time using
9710 @samp{set print symbol on}:
9713 @item set print symbol on
9714 Tell @value{GDBN} to print the symbol corresponding to an address, if
9717 @item set print symbol off
9718 Tell @value{GDBN} not to print the symbol corresponding to an
9719 address. In this mode, @value{GDBN} will still print the symbol
9720 corresponding to pointers to functions. This is the default.
9722 @item show print symbol
9723 Show whether @value{GDBN} will display the symbol corresponding to an
9727 Other settings control how different kinds of objects are printed:
9730 @item set print array
9731 @itemx set print array on
9732 @cindex pretty print arrays
9733 Pretty print arrays. This format is more convenient to read,
9734 but uses more space. The default is off.
9736 @item set print array off
9737 Return to compressed format for arrays.
9739 @item show print array
9740 Show whether compressed or pretty format is selected for displaying
9743 @cindex print array indexes
9744 @item set print array-indexes
9745 @itemx set print array-indexes on
9746 Print the index of each element when displaying arrays. May be more
9747 convenient to locate a given element in the array or quickly find the
9748 index of a given element in that printed array. The default is off.
9750 @item set print array-indexes off
9751 Stop printing element indexes when displaying arrays.
9753 @item show print array-indexes
9754 Show whether the index of each element is printed when displaying
9757 @item set print elements @var{number-of-elements}
9758 @itemx set print elements unlimited
9759 @cindex number of array elements to print
9760 @cindex limit on number of printed array elements
9761 Set a limit on how many elements of an array @value{GDBN} will print.
9762 If @value{GDBN} is printing a large array, it stops printing after it has
9763 printed the number of elements set by the @code{set print elements} command.
9764 This limit also applies to the display of strings.
9765 When @value{GDBN} starts, this limit is set to 200.
9766 Setting @var{number-of-elements} to @code{unlimited} or zero means
9767 that the number of elements to print is unlimited.
9769 @item show print elements
9770 Display the number of elements of a large array that @value{GDBN} will print.
9771 If the number is 0, then the printing is unlimited.
9773 @item set print frame-arguments @var{value}
9774 @kindex set print frame-arguments
9775 @cindex printing frame argument values
9776 @cindex print all frame argument values
9777 @cindex print frame argument values for scalars only
9778 @cindex do not print frame argument values
9779 This command allows to control how the values of arguments are printed
9780 when the debugger prints a frame (@pxref{Frames}). The possible
9785 The values of all arguments are printed.
9788 Print the value of an argument only if it is a scalar. The value of more
9789 complex arguments such as arrays, structures, unions, etc, is replaced
9790 by @code{@dots{}}. This is the default. Here is an example where
9791 only scalar arguments are shown:
9794 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9799 None of the argument values are printed. Instead, the value of each argument
9800 is replaced by @code{@dots{}}. In this case, the example above now becomes:
9803 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
9808 By default, only scalar arguments are printed. This command can be used
9809 to configure the debugger to print the value of all arguments, regardless
9810 of their type. However, it is often advantageous to not print the value
9811 of more complex parameters. For instance, it reduces the amount of
9812 information printed in each frame, making the backtrace more readable.
9813 Also, it improves performance when displaying Ada frames, because
9814 the computation of large arguments can sometimes be CPU-intensive,
9815 especially in large applications. Setting @code{print frame-arguments}
9816 to @code{scalars} (the default) or @code{none} avoids this computation,
9817 thus speeding up the display of each Ada frame.
9819 @item show print frame-arguments
9820 Show how the value of arguments should be displayed when printing a frame.
9822 @item set print raw frame-arguments on
9823 Print frame arguments in raw, non pretty-printed, form.
9825 @item set print raw frame-arguments off
9826 Print frame arguments in pretty-printed form, if there is a pretty-printer
9827 for the value (@pxref{Pretty Printing}),
9828 otherwise print the value in raw form.
9829 This is the default.
9831 @item show print raw frame-arguments
9832 Show whether to print frame arguments in raw form.
9834 @anchor{set print entry-values}
9835 @item set print entry-values @var{value}
9836 @kindex set print entry-values
9837 Set printing of frame argument values at function entry. In some cases
9838 @value{GDBN} can determine the value of function argument which was passed by
9839 the function caller, even if the value was modified inside the called function
9840 and therefore is different. With optimized code, the current value could be
9841 unavailable, but the entry value may still be known.
9843 The default value is @code{default} (see below for its description). Older
9844 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
9845 this feature will behave in the @code{default} setting the same way as with the
9848 This functionality is currently supported only by DWARF 2 debugging format and
9849 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9850 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9853 The @var{value} parameter can be one of the following:
9857 Print only actual parameter values, never print values from function entry
9861 #0 different (val=6)
9862 #0 lost (val=<optimized out>)
9864 #0 invalid (val=<optimized out>)
9868 Print only parameter values from function entry point. The actual parameter
9869 values are never printed.
9871 #0 equal (val@@entry=5)
9872 #0 different (val@@entry=5)
9873 #0 lost (val@@entry=5)
9874 #0 born (val@@entry=<optimized out>)
9875 #0 invalid (val@@entry=<optimized out>)
9879 Print only parameter values from function entry point. If value from function
9880 entry point is not known while the actual value is known, print the actual
9881 value for such parameter.
9883 #0 equal (val@@entry=5)
9884 #0 different (val@@entry=5)
9885 #0 lost (val@@entry=5)
9887 #0 invalid (val@@entry=<optimized out>)
9891 Print actual parameter values. If actual parameter value is not known while
9892 value from function entry point is known, print the entry point value for such
9896 #0 different (val=6)
9897 #0 lost (val@@entry=5)
9899 #0 invalid (val=<optimized out>)
9903 Always print both the actual parameter value and its value from function entry
9904 point, even if values of one or both are not available due to compiler
9907 #0 equal (val=5, val@@entry=5)
9908 #0 different (val=6, val@@entry=5)
9909 #0 lost (val=<optimized out>, val@@entry=5)
9910 #0 born (val=10, val@@entry=<optimized out>)
9911 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
9915 Print the actual parameter value if it is known and also its value from
9916 function entry point if it is known. If neither is known, print for the actual
9917 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
9918 values are known and identical, print the shortened
9919 @code{param=param@@entry=VALUE} notation.
9921 #0 equal (val=val@@entry=5)
9922 #0 different (val=6, val@@entry=5)
9923 #0 lost (val@@entry=5)
9925 #0 invalid (val=<optimized out>)
9929 Always print the actual parameter value. Print also its value from function
9930 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
9931 if both values are known and identical, print the shortened
9932 @code{param=param@@entry=VALUE} notation.
9934 #0 equal (val=val@@entry=5)
9935 #0 different (val=6, val@@entry=5)
9936 #0 lost (val=<optimized out>, val@@entry=5)
9938 #0 invalid (val=<optimized out>)
9942 For analysis messages on possible failures of frame argument values at function
9943 entry resolution see @ref{set debug entry-values}.
9945 @item show print entry-values
9946 Show the method being used for printing of frame argument values at function
9949 @item set print repeats @var{number-of-repeats}
9950 @itemx set print repeats unlimited
9951 @cindex repeated array elements
9952 Set the threshold for suppressing display of repeated array
9953 elements. When the number of consecutive identical elements of an
9954 array exceeds the threshold, @value{GDBN} prints the string
9955 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
9956 identical repetitions, instead of displaying the identical elements
9957 themselves. Setting the threshold to @code{unlimited} or zero will
9958 cause all elements to be individually printed. The default threshold
9961 @item show print repeats
9962 Display the current threshold for printing repeated identical
9965 @item set print null-stop
9966 @cindex @sc{null} elements in arrays
9967 Cause @value{GDBN} to stop printing the characters of an array when the first
9968 @sc{null} is encountered. This is useful when large arrays actually
9969 contain only short strings.
9972 @item show print null-stop
9973 Show whether @value{GDBN} stops printing an array on the first
9974 @sc{null} character.
9976 @item set print pretty on
9977 @cindex print structures in indented form
9978 @cindex indentation in structure display
9979 Cause @value{GDBN} to print structures in an indented format with one member
9980 per line, like this:
9995 @item set print pretty off
9996 Cause @value{GDBN} to print structures in a compact format, like this:
10000 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
10001 meat = 0x54 "Pork"@}
10006 This is the default format.
10008 @item show print pretty
10009 Show which format @value{GDBN} is using to print structures.
10011 @item set print sevenbit-strings on
10012 @cindex eight-bit characters in strings
10013 @cindex octal escapes in strings
10014 Print using only seven-bit characters; if this option is set,
10015 @value{GDBN} displays any eight-bit characters (in strings or
10016 character values) using the notation @code{\}@var{nnn}. This setting is
10017 best if you are working in English (@sc{ascii}) and you use the
10018 high-order bit of characters as a marker or ``meta'' bit.
10020 @item set print sevenbit-strings off
10021 Print full eight-bit characters. This allows the use of more
10022 international character sets, and is the default.
10024 @item show print sevenbit-strings
10025 Show whether or not @value{GDBN} is printing only seven-bit characters.
10027 @item set print union on
10028 @cindex unions in structures, printing
10029 Tell @value{GDBN} to print unions which are contained in structures
10030 and other unions. This is the default setting.
10032 @item set print union off
10033 Tell @value{GDBN} not to print unions which are contained in
10034 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
10037 @item show print union
10038 Ask @value{GDBN} whether or not it will print unions which are contained in
10039 structures and other unions.
10041 For example, given the declarations
10044 typedef enum @{Tree, Bug@} Species;
10045 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
10046 typedef enum @{Caterpillar, Cocoon, Butterfly@}
10057 struct thing foo = @{Tree, @{Acorn@}@};
10061 with @code{set print union on} in effect @samp{p foo} would print
10064 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
10068 and with @code{set print union off} in effect it would print
10071 $1 = @{it = Tree, form = @{...@}@}
10075 @code{set print union} affects programs written in C-like languages
10081 These settings are of interest when debugging C@t{++} programs:
10084 @cindex demangling C@t{++} names
10085 @item set print demangle
10086 @itemx set print demangle on
10087 Print C@t{++} names in their source form rather than in the encoded
10088 (``mangled'') form passed to the assembler and linker for type-safe
10089 linkage. The default is on.
10091 @item show print demangle
10092 Show whether C@t{++} names are printed in mangled or demangled form.
10094 @item set print asm-demangle
10095 @itemx set print asm-demangle on
10096 Print C@t{++} names in their source form rather than their mangled form, even
10097 in assembler code printouts such as instruction disassemblies.
10098 The default is off.
10100 @item show print asm-demangle
10101 Show whether C@t{++} names in assembly listings are printed in mangled
10104 @cindex C@t{++} symbol decoding style
10105 @cindex symbol decoding style, C@t{++}
10106 @kindex set demangle-style
10107 @item set demangle-style @var{style}
10108 Choose among several encoding schemes used by different compilers to
10109 represent C@t{++} names. The choices for @var{style} are currently:
10113 Allow @value{GDBN} to choose a decoding style by inspecting your program.
10114 This is the default.
10117 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
10120 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
10123 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
10126 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
10127 @strong{Warning:} this setting alone is not sufficient to allow
10128 debugging @code{cfront}-generated executables. @value{GDBN} would
10129 require further enhancement to permit that.
10132 If you omit @var{style}, you will see a list of possible formats.
10134 @item show demangle-style
10135 Display the encoding style currently in use for decoding C@t{++} symbols.
10137 @item set print object
10138 @itemx set print object on
10139 @cindex derived type of an object, printing
10140 @cindex display derived types
10141 When displaying a pointer to an object, identify the @emph{actual}
10142 (derived) type of the object rather than the @emph{declared} type, using
10143 the virtual function table. Note that the virtual function table is
10144 required---this feature can only work for objects that have run-time
10145 type identification; a single virtual method in the object's declared
10146 type is sufficient. Note that this setting is also taken into account when
10147 working with variable objects via MI (@pxref{GDB/MI}).
10149 @item set print object off
10150 Display only the declared type of objects, without reference to the
10151 virtual function table. This is the default setting.
10153 @item show print object
10154 Show whether actual, or declared, object types are displayed.
10156 @item set print static-members
10157 @itemx set print static-members on
10158 @cindex static members of C@t{++} objects
10159 Print static members when displaying a C@t{++} object. The default is on.
10161 @item set print static-members off
10162 Do not print static members when displaying a C@t{++} object.
10164 @item show print static-members
10165 Show whether C@t{++} static members are printed or not.
10167 @item set print pascal_static-members
10168 @itemx set print pascal_static-members on
10169 @cindex static members of Pascal objects
10170 @cindex Pascal objects, static members display
10171 Print static members when displaying a Pascal object. The default is on.
10173 @item set print pascal_static-members off
10174 Do not print static members when displaying a Pascal object.
10176 @item show print pascal_static-members
10177 Show whether Pascal static members are printed or not.
10179 @c These don't work with HP ANSI C++ yet.
10180 @item set print vtbl
10181 @itemx set print vtbl on
10182 @cindex pretty print C@t{++} virtual function tables
10183 @cindex virtual functions (C@t{++}) display
10184 @cindex VTBL display
10185 Pretty print C@t{++} virtual function tables. The default is off.
10186 (The @code{vtbl} commands do not work on programs compiled with the HP
10187 ANSI C@t{++} compiler (@code{aCC}).)
10189 @item set print vtbl off
10190 Do not pretty print C@t{++} virtual function tables.
10192 @item show print vtbl
10193 Show whether C@t{++} virtual function tables are pretty printed, or not.
10196 @node Pretty Printing
10197 @section Pretty Printing
10199 @value{GDBN} provides a mechanism to allow pretty-printing of values using
10200 Python code. It greatly simplifies the display of complex objects. This
10201 mechanism works for both MI and the CLI.
10204 * Pretty-Printer Introduction:: Introduction to pretty-printers
10205 * Pretty-Printer Example:: An example pretty-printer
10206 * Pretty-Printer Commands:: Pretty-printer commands
10209 @node Pretty-Printer Introduction
10210 @subsection Pretty-Printer Introduction
10212 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
10213 registered for the value. If there is then @value{GDBN} invokes the
10214 pretty-printer to print the value. Otherwise the value is printed normally.
10216 Pretty-printers are normally named. This makes them easy to manage.
10217 The @samp{info pretty-printer} command will list all the installed
10218 pretty-printers with their names.
10219 If a pretty-printer can handle multiple data types, then its
10220 @dfn{subprinters} are the printers for the individual data types.
10221 Each such subprinter has its own name.
10222 The format of the name is @var{printer-name};@var{subprinter-name}.
10224 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
10225 Typically they are automatically loaded and registered when the corresponding
10226 debug information is loaded, thus making them available without having to
10227 do anything special.
10229 There are three places where a pretty-printer can be registered.
10233 Pretty-printers registered globally are available when debugging
10237 Pretty-printers registered with a program space are available only
10238 when debugging that program.
10239 @xref{Progspaces In Python}, for more details on program spaces in Python.
10242 Pretty-printers registered with an objfile are loaded and unloaded
10243 with the corresponding objfile (e.g., shared library).
10244 @xref{Objfiles In Python}, for more details on objfiles in Python.
10247 @xref{Selecting Pretty-Printers}, for further information on how
10248 pretty-printers are selected,
10250 @xref{Writing a Pretty-Printer}, for implementing pretty printers
10253 @node Pretty-Printer Example
10254 @subsection Pretty-Printer Example
10256 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
10259 (@value{GDBP}) print s
10261 static npos = 4294967295,
10263 <std::allocator<char>> = @{
10264 <__gnu_cxx::new_allocator<char>> = @{
10265 <No data fields>@}, <No data fields>
10267 members of std::basic_string<char, std::char_traits<char>,
10268 std::allocator<char> >::_Alloc_hider:
10269 _M_p = 0x804a014 "abcd"
10274 With a pretty-printer for @code{std::string} only the contents are printed:
10277 (@value{GDBP}) print s
10281 @node Pretty-Printer Commands
10282 @subsection Pretty-Printer Commands
10283 @cindex pretty-printer commands
10286 @kindex info pretty-printer
10287 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10288 Print the list of installed pretty-printers.
10289 This includes disabled pretty-printers, which are marked as such.
10291 @var{object-regexp} is a regular expression matching the objects
10292 whose pretty-printers to list.
10293 Objects can be @code{global}, the program space's file
10294 (@pxref{Progspaces In Python}),
10295 and the object files within that program space (@pxref{Objfiles In Python}).
10296 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
10297 looks up a printer from these three objects.
10299 @var{name-regexp} is a regular expression matching the name of the printers
10302 @kindex disable pretty-printer
10303 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10304 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10305 A disabled pretty-printer is not forgotten, it may be enabled again later.
10307 @kindex enable pretty-printer
10308 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10309 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10314 Suppose we have three pretty-printers installed: one from library1.so
10315 named @code{foo} that prints objects of type @code{foo}, and
10316 another from library2.so named @code{bar} that prints two types of objects,
10317 @code{bar1} and @code{bar2}.
10320 (gdb) info pretty-printer
10327 (gdb) info pretty-printer library2
10332 (gdb) disable pretty-printer library1
10334 2 of 3 printers enabled
10335 (gdb) info pretty-printer
10342 (gdb) disable pretty-printer library2 bar:bar1
10344 1 of 3 printers enabled
10345 (gdb) info pretty-printer library2
10352 (gdb) disable pretty-printer library2 bar
10354 0 of 3 printers enabled
10355 (gdb) info pretty-printer library2
10364 Note that for @code{bar} the entire printer can be disabled,
10365 as can each individual subprinter.
10367 @node Value History
10368 @section Value History
10370 @cindex value history
10371 @cindex history of values printed by @value{GDBN}
10372 Values printed by the @code{print} command are saved in the @value{GDBN}
10373 @dfn{value history}. This allows you to refer to them in other expressions.
10374 Values are kept until the symbol table is re-read or discarded
10375 (for example with the @code{file} or @code{symbol-file} commands).
10376 When the symbol table changes, the value history is discarded,
10377 since the values may contain pointers back to the types defined in the
10382 @cindex history number
10383 The values printed are given @dfn{history numbers} by which you can
10384 refer to them. These are successive integers starting with one.
10385 @code{print} shows you the history number assigned to a value by
10386 printing @samp{$@var{num} = } before the value; here @var{num} is the
10389 To refer to any previous value, use @samp{$} followed by the value's
10390 history number. The way @code{print} labels its output is designed to
10391 remind you of this. Just @code{$} refers to the most recent value in
10392 the history, and @code{$$} refers to the value before that.
10393 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
10394 is the value just prior to @code{$$}, @code{$$1} is equivalent to
10395 @code{$$}, and @code{$$0} is equivalent to @code{$}.
10397 For example, suppose you have just printed a pointer to a structure and
10398 want to see the contents of the structure. It suffices to type
10404 If you have a chain of structures where the component @code{next} points
10405 to the next one, you can print the contents of the next one with this:
10412 You can print successive links in the chain by repeating this
10413 command---which you can do by just typing @key{RET}.
10415 Note that the history records values, not expressions. If the value of
10416 @code{x} is 4 and you type these commands:
10424 then the value recorded in the value history by the @code{print} command
10425 remains 4 even though the value of @code{x} has changed.
10428 @kindex show values
10430 Print the last ten values in the value history, with their item numbers.
10431 This is like @samp{p@ $$9} repeated ten times, except that @code{show
10432 values} does not change the history.
10434 @item show values @var{n}
10435 Print ten history values centered on history item number @var{n}.
10437 @item show values +
10438 Print ten history values just after the values last printed. If no more
10439 values are available, @code{show values +} produces no display.
10442 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
10443 same effect as @samp{show values +}.
10445 @node Convenience Vars
10446 @section Convenience Variables
10448 @cindex convenience variables
10449 @cindex user-defined variables
10450 @value{GDBN} provides @dfn{convenience variables} that you can use within
10451 @value{GDBN} to hold on to a value and refer to it later. These variables
10452 exist entirely within @value{GDBN}; they are not part of your program, and
10453 setting a convenience variable has no direct effect on further execution
10454 of your program. That is why you can use them freely.
10456 Convenience variables are prefixed with @samp{$}. Any name preceded by
10457 @samp{$} can be used for a convenience variable, unless it is one of
10458 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
10459 (Value history references, in contrast, are @emph{numbers} preceded
10460 by @samp{$}. @xref{Value History, ,Value History}.)
10462 You can save a value in a convenience variable with an assignment
10463 expression, just as you would set a variable in your program.
10467 set $foo = *object_ptr
10471 would save in @code{$foo} the value contained in the object pointed to by
10474 Using a convenience variable for the first time creates it, but its
10475 value is @code{void} until you assign a new value. You can alter the
10476 value with another assignment at any time.
10478 Convenience variables have no fixed types. You can assign a convenience
10479 variable any type of value, including structures and arrays, even if
10480 that variable already has a value of a different type. The convenience
10481 variable, when used as an expression, has the type of its current value.
10484 @kindex show convenience
10485 @cindex show all user variables and functions
10486 @item show convenience
10487 Print a list of convenience variables used so far, and their values,
10488 as well as a list of the convenience functions.
10489 Abbreviated @code{show conv}.
10491 @kindex init-if-undefined
10492 @cindex convenience variables, initializing
10493 @item init-if-undefined $@var{variable} = @var{expression}
10494 Set a convenience variable if it has not already been set. This is useful
10495 for user-defined commands that keep some state. It is similar, in concept,
10496 to using local static variables with initializers in C (except that
10497 convenience variables are global). It can also be used to allow users to
10498 override default values used in a command script.
10500 If the variable is already defined then the expression is not evaluated so
10501 any side-effects do not occur.
10504 One of the ways to use a convenience variable is as a counter to be
10505 incremented or a pointer to be advanced. For example, to print
10506 a field from successive elements of an array of structures:
10510 print bar[$i++]->contents
10514 Repeat that command by typing @key{RET}.
10516 Some convenience variables are created automatically by @value{GDBN} and given
10517 values likely to be useful.
10520 @vindex $_@r{, convenience variable}
10522 The variable @code{$_} is automatically set by the @code{x} command to
10523 the last address examined (@pxref{Memory, ,Examining Memory}). Other
10524 commands which provide a default address for @code{x} to examine also
10525 set @code{$_} to that address; these commands include @code{info line}
10526 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
10527 except when set by the @code{x} command, in which case it is a pointer
10528 to the type of @code{$__}.
10530 @vindex $__@r{, convenience variable}
10532 The variable @code{$__} is automatically set by the @code{x} command
10533 to the value found in the last address examined. Its type is chosen
10534 to match the format in which the data was printed.
10537 @vindex $_exitcode@r{, convenience variable}
10538 When the program being debugged terminates normally, @value{GDBN}
10539 automatically sets this variable to the exit code of the program, and
10540 resets @code{$_exitsignal} to @code{void}.
10543 @vindex $_exitsignal@r{, convenience variable}
10544 When the program being debugged dies due to an uncaught signal,
10545 @value{GDBN} automatically sets this variable to that signal's number,
10546 and resets @code{$_exitcode} to @code{void}.
10548 To distinguish between whether the program being debugged has exited
10549 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
10550 @code{$_exitsignal} is not @code{void}), the convenience function
10551 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
10552 Functions}). For example, considering the following source code:
10555 #include <signal.h>
10558 main (int argc, char *argv[])
10565 A valid way of telling whether the program being debugged has exited
10566 or signalled would be:
10569 (@value{GDBP}) define has_exited_or_signalled
10570 Type commands for definition of ``has_exited_or_signalled''.
10571 End with a line saying just ``end''.
10572 >if $_isvoid ($_exitsignal)
10573 >echo The program has exited\n
10575 >echo The program has signalled\n
10581 Program terminated with signal SIGALRM, Alarm clock.
10582 The program no longer exists.
10583 (@value{GDBP}) has_exited_or_signalled
10584 The program has signalled
10587 As can be seen, @value{GDBN} correctly informs that the program being
10588 debugged has signalled, since it calls @code{raise} and raises a
10589 @code{SIGALRM} signal. If the program being debugged had not called
10590 @code{raise}, then @value{GDBN} would report a normal exit:
10593 (@value{GDBP}) has_exited_or_signalled
10594 The program has exited
10598 The variable @code{$_exception} is set to the exception object being
10599 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
10602 @itemx $_probe_arg0@dots{}$_probe_arg11
10603 Arguments to a static probe. @xref{Static Probe Points}.
10606 @vindex $_sdata@r{, inspect, convenience variable}
10607 The variable @code{$_sdata} contains extra collected static tracepoint
10608 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
10609 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
10610 if extra static tracepoint data has not been collected.
10613 @vindex $_siginfo@r{, convenience variable}
10614 The variable @code{$_siginfo} contains extra signal information
10615 (@pxref{extra signal information}). Note that @code{$_siginfo}
10616 could be empty, if the application has not yet received any signals.
10617 For example, it will be empty before you execute the @code{run} command.
10620 @vindex $_tlb@r{, convenience variable}
10621 The variable @code{$_tlb} is automatically set when debugging
10622 applications running on MS-Windows in native mode or connected to
10623 gdbserver that supports the @code{qGetTIBAddr} request.
10624 @xref{General Query Packets}.
10625 This variable contains the address of the thread information block.
10628 The number of the current inferior. @xref{Inferiors and
10629 Programs, ,Debugging Multiple Inferiors and Programs}.
10632 The thread number of the current thread. @xref{thread numbers}.
10635 The global number of the current thread. @xref{global thread numbers}.
10639 @node Convenience Funs
10640 @section Convenience Functions
10642 @cindex convenience functions
10643 @value{GDBN} also supplies some @dfn{convenience functions}. These
10644 have a syntax similar to convenience variables. A convenience
10645 function can be used in an expression just like an ordinary function;
10646 however, a convenience function is implemented internally to
10649 These functions do not require @value{GDBN} to be configured with
10650 @code{Python} support, which means that they are always available.
10654 @item $_isvoid (@var{expr})
10655 @findex $_isvoid@r{, convenience function}
10656 Return one if the expression @var{expr} is @code{void}. Otherwise it
10659 A @code{void} expression is an expression where the type of the result
10660 is @code{void}. For example, you can examine a convenience variable
10661 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
10665 (@value{GDBP}) print $_exitcode
10667 (@value{GDBP}) print $_isvoid ($_exitcode)
10670 Starting program: ./a.out
10671 [Inferior 1 (process 29572) exited normally]
10672 (@value{GDBP}) print $_exitcode
10674 (@value{GDBP}) print $_isvoid ($_exitcode)
10678 In the example above, we used @code{$_isvoid} to check whether
10679 @code{$_exitcode} is @code{void} before and after the execution of the
10680 program being debugged. Before the execution there is no exit code to
10681 be examined, therefore @code{$_exitcode} is @code{void}. After the
10682 execution the program being debugged returned zero, therefore
10683 @code{$_exitcode} is zero, which means that it is not @code{void}
10686 The @code{void} expression can also be a call of a function from the
10687 program being debugged. For example, given the following function:
10696 The result of calling it inside @value{GDBN} is @code{void}:
10699 (@value{GDBP}) print foo ()
10701 (@value{GDBP}) print $_isvoid (foo ())
10703 (@value{GDBP}) set $v = foo ()
10704 (@value{GDBP}) print $v
10706 (@value{GDBP}) print $_isvoid ($v)
10712 These functions require @value{GDBN} to be configured with
10713 @code{Python} support.
10717 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
10718 @findex $_memeq@r{, convenience function}
10719 Returns one if the @var{length} bytes at the addresses given by
10720 @var{buf1} and @var{buf2} are equal.
10721 Otherwise it returns zero.
10723 @item $_regex(@var{str}, @var{regex})
10724 @findex $_regex@r{, convenience function}
10725 Returns one if the string @var{str} matches the regular expression
10726 @var{regex}. Otherwise it returns zero.
10727 The syntax of the regular expression is that specified by @code{Python}'s
10728 regular expression support.
10730 @item $_streq(@var{str1}, @var{str2})
10731 @findex $_streq@r{, convenience function}
10732 Returns one if the strings @var{str1} and @var{str2} are equal.
10733 Otherwise it returns zero.
10735 @item $_strlen(@var{str})
10736 @findex $_strlen@r{, convenience function}
10737 Returns the length of string @var{str}.
10739 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10740 @findex $_caller_is@r{, convenience function}
10741 Returns one if the calling function's name is equal to @var{name}.
10742 Otherwise it returns zero.
10744 If the optional argument @var{number_of_frames} is provided,
10745 it is the number of frames up in the stack to look.
10753 at testsuite/gdb.python/py-caller-is.c:21
10754 #1 0x00000000004005a0 in middle_func ()
10755 at testsuite/gdb.python/py-caller-is.c:27
10756 #2 0x00000000004005ab in top_func ()
10757 at testsuite/gdb.python/py-caller-is.c:33
10758 #3 0x00000000004005b6 in main ()
10759 at testsuite/gdb.python/py-caller-is.c:39
10760 (gdb) print $_caller_is ("middle_func")
10762 (gdb) print $_caller_is ("top_func", 2)
10766 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10767 @findex $_caller_matches@r{, convenience function}
10768 Returns one if the calling function's name matches the regular expression
10769 @var{regexp}. Otherwise it returns zero.
10771 If the optional argument @var{number_of_frames} is provided,
10772 it is the number of frames up in the stack to look.
10775 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10776 @findex $_any_caller_is@r{, convenience function}
10777 Returns one if any calling function's name is equal to @var{name}.
10778 Otherwise it returns zero.
10780 If the optional argument @var{number_of_frames} is provided,
10781 it is the number of frames up in the stack to look.
10784 This function differs from @code{$_caller_is} in that this function
10785 checks all stack frames from the immediate caller to the frame specified
10786 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
10787 frame specified by @var{number_of_frames}.
10789 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10790 @findex $_any_caller_matches@r{, convenience function}
10791 Returns one if any calling function's name matches the regular expression
10792 @var{regexp}. Otherwise it returns zero.
10794 If the optional argument @var{number_of_frames} is provided,
10795 it is the number of frames up in the stack to look.
10798 This function differs from @code{$_caller_matches} in that this function
10799 checks all stack frames from the immediate caller to the frame specified
10800 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
10801 frame specified by @var{number_of_frames}.
10803 @item $_as_string(@var{value})
10804 @findex $_as_string@r{, convenience function}
10805 Return the string representation of @var{value}.
10807 This function is useful to obtain the textual label (enumerator) of an
10808 enumeration value. For example, assuming the variable @var{node} is of
10809 an enumerated type:
10812 (gdb) printf "Visiting node of type %s\n", $_as_string(node)
10813 Visiting node of type NODE_INTEGER
10818 @value{GDBN} provides the ability to list and get help on
10819 convenience functions.
10822 @item help function
10823 @kindex help function
10824 @cindex show all convenience functions
10825 Print a list of all convenience functions.
10832 You can refer to machine register contents, in expressions, as variables
10833 with names starting with @samp{$}. The names of registers are different
10834 for each machine; use @code{info registers} to see the names used on
10838 @kindex info registers
10839 @item info registers
10840 Print the names and values of all registers except floating-point
10841 and vector registers (in the selected stack frame).
10843 @kindex info all-registers
10844 @cindex floating point registers
10845 @item info all-registers
10846 Print the names and values of all registers, including floating-point
10847 and vector registers (in the selected stack frame).
10849 @item info registers @var{regname} @dots{}
10850 Print the @dfn{relativized} value of each specified register @var{regname}.
10851 As discussed in detail below, register values are normally relative to
10852 the selected stack frame. The @var{regname} may be any register name valid on
10853 the machine you are using, with or without the initial @samp{$}.
10856 @anchor{standard registers}
10857 @cindex stack pointer register
10858 @cindex program counter register
10859 @cindex process status register
10860 @cindex frame pointer register
10861 @cindex standard registers
10862 @value{GDBN} has four ``standard'' register names that are available (in
10863 expressions) on most machines---whenever they do not conflict with an
10864 architecture's canonical mnemonics for registers. The register names
10865 @code{$pc} and @code{$sp} are used for the program counter register and
10866 the stack pointer. @code{$fp} is used for a register that contains a
10867 pointer to the current stack frame, and @code{$ps} is used for a
10868 register that contains the processor status. For example,
10869 you could print the program counter in hex with
10876 or print the instruction to be executed next with
10883 or add four to the stack pointer@footnote{This is a way of removing
10884 one word from the stack, on machines where stacks grow downward in
10885 memory (most machines, nowadays). This assumes that the innermost
10886 stack frame is selected; setting @code{$sp} is not allowed when other
10887 stack frames are selected. To pop entire frames off the stack,
10888 regardless of machine architecture, use @code{return};
10889 see @ref{Returning, ,Returning from a Function}.} with
10895 Whenever possible, these four standard register names are available on
10896 your machine even though the machine has different canonical mnemonics,
10897 so long as there is no conflict. The @code{info registers} command
10898 shows the canonical names. For example, on the SPARC, @code{info
10899 registers} displays the processor status register as @code{$psr} but you
10900 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
10901 is an alias for the @sc{eflags} register.
10903 @value{GDBN} always considers the contents of an ordinary register as an
10904 integer when the register is examined in this way. Some machines have
10905 special registers which can hold nothing but floating point; these
10906 registers are considered to have floating point values. There is no way
10907 to refer to the contents of an ordinary register as floating point value
10908 (although you can @emph{print} it as a floating point value with
10909 @samp{print/f $@var{regname}}).
10911 Some registers have distinct ``raw'' and ``virtual'' data formats. This
10912 means that the data format in which the register contents are saved by
10913 the operating system is not the same one that your program normally
10914 sees. For example, the registers of the 68881 floating point
10915 coprocessor are always saved in ``extended'' (raw) format, but all C
10916 programs expect to work with ``double'' (virtual) format. In such
10917 cases, @value{GDBN} normally works with the virtual format only (the format
10918 that makes sense for your program), but the @code{info registers} command
10919 prints the data in both formats.
10921 @cindex SSE registers (x86)
10922 @cindex MMX registers (x86)
10923 Some machines have special registers whose contents can be interpreted
10924 in several different ways. For example, modern x86-based machines
10925 have SSE and MMX registers that can hold several values packed
10926 together in several different formats. @value{GDBN} refers to such
10927 registers in @code{struct} notation:
10930 (@value{GDBP}) print $xmm1
10932 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
10933 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
10934 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
10935 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
10936 v4_int32 = @{0, 20657912, 11, 13@},
10937 v2_int64 = @{88725056443645952, 55834574859@},
10938 uint128 = 0x0000000d0000000b013b36f800000000
10943 To set values of such registers, you need to tell @value{GDBN} which
10944 view of the register you wish to change, as if you were assigning
10945 value to a @code{struct} member:
10948 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
10951 Normally, register values are relative to the selected stack frame
10952 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
10953 value that the register would contain if all stack frames farther in
10954 were exited and their saved registers restored. In order to see the
10955 true contents of hardware registers, you must select the innermost
10956 frame (with @samp{frame 0}).
10958 @cindex caller-saved registers
10959 @cindex call-clobbered registers
10960 @cindex volatile registers
10961 @cindex <not saved> values
10962 Usually ABIs reserve some registers as not needed to be saved by the
10963 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
10964 registers). It may therefore not be possible for @value{GDBN} to know
10965 the value a register had before the call (in other words, in the outer
10966 frame), if the register value has since been changed by the callee.
10967 @value{GDBN} tries to deduce where the inner frame saved
10968 (``callee-saved'') registers, from the debug info, unwind info, or the
10969 machine code generated by your compiler. If some register is not
10970 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
10971 its own knowledge of the ABI, or because the debug/unwind info
10972 explicitly says the register's value is undefined), @value{GDBN}
10973 displays @w{@samp{<not saved>}} as the register's value. With targets
10974 that @value{GDBN} has no knowledge of the register saving convention,
10975 if a register was not saved by the callee, then its value and location
10976 in the outer frame are assumed to be the same of the inner frame.
10977 This is usually harmless, because if the register is call-clobbered,
10978 the caller either does not care what is in the register after the
10979 call, or has code to restore the value that it does care about. Note,
10980 however, that if you change such a register in the outer frame, you
10981 may also be affecting the inner frame. Also, the more ``outer'' the
10982 frame is you're looking at, the more likely a call-clobbered
10983 register's value is to be wrong, in the sense that it doesn't actually
10984 represent the value the register had just before the call.
10986 @node Floating Point Hardware
10987 @section Floating Point Hardware
10988 @cindex floating point
10990 Depending on the configuration, @value{GDBN} may be able to give
10991 you more information about the status of the floating point hardware.
10996 Display hardware-dependent information about the floating
10997 point unit. The exact contents and layout vary depending on the
10998 floating point chip. Currently, @samp{info float} is supported on
10999 the ARM and x86 machines.
11003 @section Vector Unit
11004 @cindex vector unit
11006 Depending on the configuration, @value{GDBN} may be able to give you
11007 more information about the status of the vector unit.
11010 @kindex info vector
11012 Display information about the vector unit. The exact contents and
11013 layout vary depending on the hardware.
11016 @node OS Information
11017 @section Operating System Auxiliary Information
11018 @cindex OS information
11020 @value{GDBN} provides interfaces to useful OS facilities that can help
11021 you debug your program.
11023 @cindex auxiliary vector
11024 @cindex vector, auxiliary
11025 Some operating systems supply an @dfn{auxiliary vector} to programs at
11026 startup. This is akin to the arguments and environment that you
11027 specify for a program, but contains a system-dependent variety of
11028 binary values that tell system libraries important details about the
11029 hardware, operating system, and process. Each value's purpose is
11030 identified by an integer tag; the meanings are well-known but system-specific.
11031 Depending on the configuration and operating system facilities,
11032 @value{GDBN} may be able to show you this information. For remote
11033 targets, this functionality may further depend on the remote stub's
11034 support of the @samp{qXfer:auxv:read} packet, see
11035 @ref{qXfer auxiliary vector read}.
11040 Display the auxiliary vector of the inferior, which can be either a
11041 live process or a core dump file. @value{GDBN} prints each tag value
11042 numerically, and also shows names and text descriptions for recognized
11043 tags. Some values in the vector are numbers, some bit masks, and some
11044 pointers to strings or other data. @value{GDBN} displays each value in the
11045 most appropriate form for a recognized tag, and in hexadecimal for
11046 an unrecognized tag.
11049 On some targets, @value{GDBN} can access operating system-specific
11050 information and show it to you. The types of information available
11051 will differ depending on the type of operating system running on the
11052 target. The mechanism used to fetch the data is described in
11053 @ref{Operating System Information}. For remote targets, this
11054 functionality depends on the remote stub's support of the
11055 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
11059 @item info os @var{infotype}
11061 Display OS information of the requested type.
11063 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
11065 @anchor{linux info os infotypes}
11067 @kindex info os cpus
11069 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
11070 the available fields from /proc/cpuinfo. For each supported architecture
11071 different fields are available. Two common entries are processor which gives
11072 CPU number and bogomips; a system constant that is calculated during
11073 kernel initialization.
11075 @kindex info os files
11077 Display the list of open file descriptors on the target. For each
11078 file descriptor, @value{GDBN} prints the identifier of the process
11079 owning the descriptor, the command of the owning process, the value
11080 of the descriptor, and the target of the descriptor.
11082 @kindex info os modules
11084 Display the list of all loaded kernel modules on the target. For each
11085 module, @value{GDBN} prints the module name, the size of the module in
11086 bytes, the number of times the module is used, the dependencies of the
11087 module, the status of the module, and the address of the loaded module
11090 @kindex info os msg
11092 Display the list of all System V message queues on the target. For each
11093 message queue, @value{GDBN} prints the message queue key, the message
11094 queue identifier, the access permissions, the current number of bytes
11095 on the queue, the current number of messages on the queue, the processes
11096 that last sent and received a message on the queue, the user and group
11097 of the owner and creator of the message queue, the times at which a
11098 message was last sent and received on the queue, and the time at which
11099 the message queue was last changed.
11101 @kindex info os processes
11103 Display the list of processes on the target. For each process,
11104 @value{GDBN} prints the process identifier, the name of the user, the
11105 command corresponding to the process, and the list of processor cores
11106 that the process is currently running on. (To understand what these
11107 properties mean, for this and the following info types, please consult
11108 the general @sc{gnu}/Linux documentation.)
11110 @kindex info os procgroups
11112 Display the list of process groups on the target. For each process,
11113 @value{GDBN} prints the identifier of the process group that it belongs
11114 to, the command corresponding to the process group leader, the process
11115 identifier, and the command line of the process. The list is sorted
11116 first by the process group identifier, then by the process identifier,
11117 so that processes belonging to the same process group are grouped together
11118 and the process group leader is listed first.
11120 @kindex info os semaphores
11122 Display the list of all System V semaphore sets on the target. For each
11123 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
11124 set identifier, the access permissions, the number of semaphores in the
11125 set, the user and group of the owner and creator of the semaphore set,
11126 and the times at which the semaphore set was operated upon and changed.
11128 @kindex info os shm
11130 Display the list of all System V shared-memory regions on the target.
11131 For each shared-memory region, @value{GDBN} prints the region key,
11132 the shared-memory identifier, the access permissions, the size of the
11133 region, the process that created the region, the process that last
11134 attached to or detached from the region, the current number of live
11135 attaches to the region, and the times at which the region was last
11136 attached to, detach from, and changed.
11138 @kindex info os sockets
11140 Display the list of Internet-domain sockets on the target. For each
11141 socket, @value{GDBN} prints the address and port of the local and
11142 remote endpoints, the current state of the connection, the creator of
11143 the socket, the IP address family of the socket, and the type of the
11146 @kindex info os threads
11148 Display the list of threads running on the target. For each thread,
11149 @value{GDBN} prints the identifier of the process that the thread
11150 belongs to, the command of the process, the thread identifier, and the
11151 processor core that it is currently running on. The main thread of a
11152 process is not listed.
11156 If @var{infotype} is omitted, then list the possible values for
11157 @var{infotype} and the kind of OS information available for each
11158 @var{infotype}. If the target does not return a list of possible
11159 types, this command will report an error.
11162 @node Memory Region Attributes
11163 @section Memory Region Attributes
11164 @cindex memory region attributes
11166 @dfn{Memory region attributes} allow you to describe special handling
11167 required by regions of your target's memory. @value{GDBN} uses
11168 attributes to determine whether to allow certain types of memory
11169 accesses; whether to use specific width accesses; and whether to cache
11170 target memory. By default the description of memory regions is
11171 fetched from the target (if the current target supports this), but the
11172 user can override the fetched regions.
11174 Defined memory regions can be individually enabled and disabled. When a
11175 memory region is disabled, @value{GDBN} uses the default attributes when
11176 accessing memory in that region. Similarly, if no memory regions have
11177 been defined, @value{GDBN} uses the default attributes when accessing
11180 When a memory region is defined, it is given a number to identify it;
11181 to enable, disable, or remove a memory region, you specify that number.
11185 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
11186 Define a memory region bounded by @var{lower} and @var{upper} with
11187 attributes @var{attributes}@dots{}, and add it to the list of regions
11188 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
11189 case: it is treated as the target's maximum memory address.
11190 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
11193 Discard any user changes to the memory regions and use target-supplied
11194 regions, if available, or no regions if the target does not support.
11197 @item delete mem @var{nums}@dots{}
11198 Remove memory regions @var{nums}@dots{} from the list of regions
11199 monitored by @value{GDBN}.
11201 @kindex disable mem
11202 @item disable mem @var{nums}@dots{}
11203 Disable monitoring of memory regions @var{nums}@dots{}.
11204 A disabled memory region is not forgotten.
11205 It may be enabled again later.
11208 @item enable mem @var{nums}@dots{}
11209 Enable monitoring of memory regions @var{nums}@dots{}.
11213 Print a table of all defined memory regions, with the following columns
11217 @item Memory Region Number
11218 @item Enabled or Disabled.
11219 Enabled memory regions are marked with @samp{y}.
11220 Disabled memory regions are marked with @samp{n}.
11223 The address defining the inclusive lower bound of the memory region.
11226 The address defining the exclusive upper bound of the memory region.
11229 The list of attributes set for this memory region.
11234 @subsection Attributes
11236 @subsubsection Memory Access Mode
11237 The access mode attributes set whether @value{GDBN} may make read or
11238 write accesses to a memory region.
11240 While these attributes prevent @value{GDBN} from performing invalid
11241 memory accesses, they do nothing to prevent the target system, I/O DMA,
11242 etc.@: from accessing memory.
11246 Memory is read only.
11248 Memory is write only.
11250 Memory is read/write. This is the default.
11253 @subsubsection Memory Access Size
11254 The access size attribute tells @value{GDBN} to use specific sized
11255 accesses in the memory region. Often memory mapped device registers
11256 require specific sized accesses. If no access size attribute is
11257 specified, @value{GDBN} may use accesses of any size.
11261 Use 8 bit memory accesses.
11263 Use 16 bit memory accesses.
11265 Use 32 bit memory accesses.
11267 Use 64 bit memory accesses.
11270 @c @subsubsection Hardware/Software Breakpoints
11271 @c The hardware/software breakpoint attributes set whether @value{GDBN}
11272 @c will use hardware or software breakpoints for the internal breakpoints
11273 @c used by the step, next, finish, until, etc. commands.
11277 @c Always use hardware breakpoints
11278 @c @item swbreak (default)
11281 @subsubsection Data Cache
11282 The data cache attributes set whether @value{GDBN} will cache target
11283 memory. While this generally improves performance by reducing debug
11284 protocol overhead, it can lead to incorrect results because @value{GDBN}
11285 does not know about volatile variables or memory mapped device
11290 Enable @value{GDBN} to cache target memory.
11292 Disable @value{GDBN} from caching target memory. This is the default.
11295 @subsection Memory Access Checking
11296 @value{GDBN} can be instructed to refuse accesses to memory that is
11297 not explicitly described. This can be useful if accessing such
11298 regions has undesired effects for a specific target, or to provide
11299 better error checking. The following commands control this behaviour.
11302 @kindex set mem inaccessible-by-default
11303 @item set mem inaccessible-by-default [on|off]
11304 If @code{on} is specified, make @value{GDBN} treat memory not
11305 explicitly described by the memory ranges as non-existent and refuse accesses
11306 to such memory. The checks are only performed if there's at least one
11307 memory range defined. If @code{off} is specified, make @value{GDBN}
11308 treat the memory not explicitly described by the memory ranges as RAM.
11309 The default value is @code{on}.
11310 @kindex show mem inaccessible-by-default
11311 @item show mem inaccessible-by-default
11312 Show the current handling of accesses to unknown memory.
11316 @c @subsubsection Memory Write Verification
11317 @c The memory write verification attributes set whether @value{GDBN}
11318 @c will re-reads data after each write to verify the write was successful.
11322 @c @item noverify (default)
11325 @node Dump/Restore Files
11326 @section Copy Between Memory and a File
11327 @cindex dump/restore files
11328 @cindex append data to a file
11329 @cindex dump data to a file
11330 @cindex restore data from a file
11332 You can use the commands @code{dump}, @code{append}, and
11333 @code{restore} to copy data between target memory and a file. The
11334 @code{dump} and @code{append} commands write data to a file, and the
11335 @code{restore} command reads data from a file back into the inferior's
11336 memory. Files may be in binary, Motorola S-record, Intel hex,
11337 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
11338 append to binary files, and cannot read from Verilog Hex files.
11343 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11344 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
11345 Dump the contents of memory from @var{start_addr} to @var{end_addr},
11346 or the value of @var{expr}, to @var{filename} in the given format.
11348 The @var{format} parameter may be any one of:
11355 Motorola S-record format.
11357 Tektronix Hex format.
11359 Verilog Hex format.
11362 @value{GDBN} uses the same definitions of these formats as the
11363 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
11364 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
11368 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11369 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
11370 Append the contents of memory from @var{start_addr} to @var{end_addr},
11371 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
11372 (@value{GDBN} can only append data to files in raw binary form.)
11375 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
11376 Restore the contents of file @var{filename} into memory. The
11377 @code{restore} command can automatically recognize any known @sc{bfd}
11378 file format, except for raw binary. To restore a raw binary file you
11379 must specify the optional keyword @code{binary} after the filename.
11381 If @var{bias} is non-zero, its value will be added to the addresses
11382 contained in the file. Binary files always start at address zero, so
11383 they will be restored at address @var{bias}. Other bfd files have
11384 a built-in location; they will be restored at offset @var{bias}
11385 from that location.
11387 If @var{start} and/or @var{end} are non-zero, then only data between
11388 file offset @var{start} and file offset @var{end} will be restored.
11389 These offsets are relative to the addresses in the file, before
11390 the @var{bias} argument is applied.
11394 @node Core File Generation
11395 @section How to Produce a Core File from Your Program
11396 @cindex dump core from inferior
11398 A @dfn{core file} or @dfn{core dump} is a file that records the memory
11399 image of a running process and its process status (register values
11400 etc.). Its primary use is post-mortem debugging of a program that
11401 crashed while it ran outside a debugger. A program that crashes
11402 automatically produces a core file, unless this feature is disabled by
11403 the user. @xref{Files}, for information on invoking @value{GDBN} in
11404 the post-mortem debugging mode.
11406 Occasionally, you may wish to produce a core file of the program you
11407 are debugging in order to preserve a snapshot of its state.
11408 @value{GDBN} has a special command for that.
11412 @kindex generate-core-file
11413 @item generate-core-file [@var{file}]
11414 @itemx gcore [@var{file}]
11415 Produce a core dump of the inferior process. The optional argument
11416 @var{file} specifies the file name where to put the core dump. If not
11417 specified, the file name defaults to @file{core.@var{pid}}, where
11418 @var{pid} is the inferior process ID.
11420 Note that this command is implemented only for some systems (as of
11421 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
11423 On @sc{gnu}/Linux, this command can take into account the value of the
11424 file @file{/proc/@var{pid}/coredump_filter} when generating the core
11425 dump (@pxref{set use-coredump-filter}).
11427 @kindex set use-coredump-filter
11428 @anchor{set use-coredump-filter}
11429 @item set use-coredump-filter on
11430 @itemx set use-coredump-filter off
11431 Enable or disable the use of the file
11432 @file{/proc/@var{pid}/coredump_filter} when generating core dump
11433 files. This file is used by the Linux kernel to decide what types of
11434 memory mappings will be dumped or ignored when generating a core dump
11435 file. @var{pid} is the process ID of a currently running process.
11437 To make use of this feature, you have to write in the
11438 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
11439 which is a bit mask representing the memory mapping types. If a bit
11440 is set in the bit mask, then the memory mappings of the corresponding
11441 types will be dumped; otherwise, they will be ignored. This
11442 configuration is inherited by child processes. For more information
11443 about the bits that can be set in the
11444 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
11445 manpage of @code{core(5)}.
11447 By default, this option is @code{on}. If this option is turned
11448 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
11449 and instead uses the same default value as the Linux kernel in order
11450 to decide which pages will be dumped in the core dump file. This
11451 value is currently @code{0x33}, which means that bits @code{0}
11452 (anonymous private mappings), @code{1} (anonymous shared mappings),
11453 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
11454 This will cause these memory mappings to be dumped automatically.
11457 @node Character Sets
11458 @section Character Sets
11459 @cindex character sets
11461 @cindex translating between character sets
11462 @cindex host character set
11463 @cindex target character set
11465 If the program you are debugging uses a different character set to
11466 represent characters and strings than the one @value{GDBN} uses itself,
11467 @value{GDBN} can automatically translate between the character sets for
11468 you. The character set @value{GDBN} uses we call the @dfn{host
11469 character set}; the one the inferior program uses we call the
11470 @dfn{target character set}.
11472 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
11473 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
11474 remote protocol (@pxref{Remote Debugging}) to debug a program
11475 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
11476 then the host character set is Latin-1, and the target character set is
11477 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
11478 target-charset EBCDIC-US}, then @value{GDBN} translates between
11479 @sc{ebcdic} and Latin 1 as you print character or string values, or use
11480 character and string literals in expressions.
11482 @value{GDBN} has no way to automatically recognize which character set
11483 the inferior program uses; you must tell it, using the @code{set
11484 target-charset} command, described below.
11486 Here are the commands for controlling @value{GDBN}'s character set
11490 @item set target-charset @var{charset}
11491 @kindex set target-charset
11492 Set the current target character set to @var{charset}. To display the
11493 list of supported target character sets, type
11494 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
11496 @item set host-charset @var{charset}
11497 @kindex set host-charset
11498 Set the current host character set to @var{charset}.
11500 By default, @value{GDBN} uses a host character set appropriate to the
11501 system it is running on; you can override that default using the
11502 @code{set host-charset} command. On some systems, @value{GDBN} cannot
11503 automatically determine the appropriate host character set. In this
11504 case, @value{GDBN} uses @samp{UTF-8}.
11506 @value{GDBN} can only use certain character sets as its host character
11507 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
11508 @value{GDBN} will list the host character sets it supports.
11510 @item set charset @var{charset}
11511 @kindex set charset
11512 Set the current host and target character sets to @var{charset}. As
11513 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
11514 @value{GDBN} will list the names of the character sets that can be used
11515 for both host and target.
11518 @kindex show charset
11519 Show the names of the current host and target character sets.
11521 @item show host-charset
11522 @kindex show host-charset
11523 Show the name of the current host character set.
11525 @item show target-charset
11526 @kindex show target-charset
11527 Show the name of the current target character set.
11529 @item set target-wide-charset @var{charset}
11530 @kindex set target-wide-charset
11531 Set the current target's wide character set to @var{charset}. This is
11532 the character set used by the target's @code{wchar_t} type. To
11533 display the list of supported wide character sets, type
11534 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
11536 @item show target-wide-charset
11537 @kindex show target-wide-charset
11538 Show the name of the current target's wide character set.
11541 Here is an example of @value{GDBN}'s character set support in action.
11542 Assume that the following source code has been placed in the file
11543 @file{charset-test.c}:
11549 = @{72, 101, 108, 108, 111, 44, 32, 119,
11550 111, 114, 108, 100, 33, 10, 0@};
11551 char ibm1047_hello[]
11552 = @{200, 133, 147, 147, 150, 107, 64, 166,
11553 150, 153, 147, 132, 90, 37, 0@};
11557 printf ("Hello, world!\n");
11561 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
11562 containing the string @samp{Hello, world!} followed by a newline,
11563 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
11565 We compile the program, and invoke the debugger on it:
11568 $ gcc -g charset-test.c -o charset-test
11569 $ gdb -nw charset-test
11570 GNU gdb 2001-12-19-cvs
11571 Copyright 2001 Free Software Foundation, Inc.
11576 We can use the @code{show charset} command to see what character sets
11577 @value{GDBN} is currently using to interpret and display characters and
11581 (@value{GDBP}) show charset
11582 The current host and target character set is `ISO-8859-1'.
11586 For the sake of printing this manual, let's use @sc{ascii} as our
11587 initial character set:
11589 (@value{GDBP}) set charset ASCII
11590 (@value{GDBP}) show charset
11591 The current host and target character set is `ASCII'.
11595 Let's assume that @sc{ascii} is indeed the correct character set for our
11596 host system --- in other words, let's assume that if @value{GDBN} prints
11597 characters using the @sc{ascii} character set, our terminal will display
11598 them properly. Since our current target character set is also
11599 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
11602 (@value{GDBP}) print ascii_hello
11603 $1 = 0x401698 "Hello, world!\n"
11604 (@value{GDBP}) print ascii_hello[0]
11609 @value{GDBN} uses the target character set for character and string
11610 literals you use in expressions:
11613 (@value{GDBP}) print '+'
11618 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
11621 @value{GDBN} relies on the user to tell it which character set the
11622 target program uses. If we print @code{ibm1047_hello} while our target
11623 character set is still @sc{ascii}, we get jibberish:
11626 (@value{GDBP}) print ibm1047_hello
11627 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
11628 (@value{GDBP}) print ibm1047_hello[0]
11633 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
11634 @value{GDBN} tells us the character sets it supports:
11637 (@value{GDBP}) set target-charset
11638 ASCII EBCDIC-US IBM1047 ISO-8859-1
11639 (@value{GDBP}) set target-charset
11642 We can select @sc{ibm1047} as our target character set, and examine the
11643 program's strings again. Now the @sc{ascii} string is wrong, but
11644 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
11645 target character set, @sc{ibm1047}, to the host character set,
11646 @sc{ascii}, and they display correctly:
11649 (@value{GDBP}) set target-charset IBM1047
11650 (@value{GDBP}) show charset
11651 The current host character set is `ASCII'.
11652 The current target character set is `IBM1047'.
11653 (@value{GDBP}) print ascii_hello
11654 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
11655 (@value{GDBP}) print ascii_hello[0]
11657 (@value{GDBP}) print ibm1047_hello
11658 $8 = 0x4016a8 "Hello, world!\n"
11659 (@value{GDBP}) print ibm1047_hello[0]
11664 As above, @value{GDBN} uses the target character set for character and
11665 string literals you use in expressions:
11668 (@value{GDBP}) print '+'
11673 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
11676 @node Caching Target Data
11677 @section Caching Data of Targets
11678 @cindex caching data of targets
11680 @value{GDBN} caches data exchanged between the debugger and a target.
11681 Each cache is associated with the address space of the inferior.
11682 @xref{Inferiors and Programs}, about inferior and address space.
11683 Such caching generally improves performance in remote debugging
11684 (@pxref{Remote Debugging}), because it reduces the overhead of the
11685 remote protocol by bundling memory reads and writes into large chunks.
11686 Unfortunately, simply caching everything would lead to incorrect results,
11687 since @value{GDBN} does not necessarily know anything about volatile
11688 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
11689 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
11691 Therefore, by default, @value{GDBN} only caches data
11692 known to be on the stack@footnote{In non-stop mode, it is moderately
11693 rare for a running thread to modify the stack of a stopped thread
11694 in a way that would interfere with a backtrace, and caching of
11695 stack reads provides a significant speed up of remote backtraces.} or
11696 in the code segment.
11697 Other regions of memory can be explicitly marked as
11698 cacheable; @pxref{Memory Region Attributes}.
11701 @kindex set remotecache
11702 @item set remotecache on
11703 @itemx set remotecache off
11704 This option no longer does anything; it exists for compatibility
11707 @kindex show remotecache
11708 @item show remotecache
11709 Show the current state of the obsolete remotecache flag.
11711 @kindex set stack-cache
11712 @item set stack-cache on
11713 @itemx set stack-cache off
11714 Enable or disable caching of stack accesses. When @code{on}, use
11715 caching. By default, this option is @code{on}.
11717 @kindex show stack-cache
11718 @item show stack-cache
11719 Show the current state of data caching for memory accesses.
11721 @kindex set code-cache
11722 @item set code-cache on
11723 @itemx set code-cache off
11724 Enable or disable caching of code segment accesses. When @code{on},
11725 use caching. By default, this option is @code{on}. This improves
11726 performance of disassembly in remote debugging.
11728 @kindex show code-cache
11729 @item show code-cache
11730 Show the current state of target memory cache for code segment
11733 @kindex info dcache
11734 @item info dcache @r{[}line@r{]}
11735 Print the information about the performance of data cache of the
11736 current inferior's address space. The information displayed
11737 includes the dcache width and depth, and for each cache line, its
11738 number, address, and how many times it was referenced. This
11739 command is useful for debugging the data cache operation.
11741 If a line number is specified, the contents of that line will be
11744 @item set dcache size @var{size}
11745 @cindex dcache size
11746 @kindex set dcache size
11747 Set maximum number of entries in dcache (dcache depth above).
11749 @item set dcache line-size @var{line-size}
11750 @cindex dcache line-size
11751 @kindex set dcache line-size
11752 Set number of bytes each dcache entry caches (dcache width above).
11753 Must be a power of 2.
11755 @item show dcache size
11756 @kindex show dcache size
11757 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
11759 @item show dcache line-size
11760 @kindex show dcache line-size
11761 Show default size of dcache lines.
11765 @node Searching Memory
11766 @section Search Memory
11767 @cindex searching memory
11769 Memory can be searched for a particular sequence of bytes with the
11770 @code{find} command.
11774 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11775 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11776 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
11777 etc. The search begins at address @var{start_addr} and continues for either
11778 @var{len} bytes or through to @var{end_addr} inclusive.
11781 @var{s} and @var{n} are optional parameters.
11782 They may be specified in either order, apart or together.
11785 @item @var{s}, search query size
11786 The size of each search query value.
11792 halfwords (two bytes)
11796 giant words (eight bytes)
11799 All values are interpreted in the current language.
11800 This means, for example, that if the current source language is C/C@t{++}
11801 then searching for the string ``hello'' includes the trailing '\0'.
11803 If the value size is not specified, it is taken from the
11804 value's type in the current language.
11805 This is useful when one wants to specify the search
11806 pattern as a mixture of types.
11807 Note that this means, for example, that in the case of C-like languages
11808 a search for an untyped 0x42 will search for @samp{(int) 0x42}
11809 which is typically four bytes.
11811 @item @var{n}, maximum number of finds
11812 The maximum number of matches to print. The default is to print all finds.
11815 You can use strings as search values. Quote them with double-quotes
11817 The string value is copied into the search pattern byte by byte,
11818 regardless of the endianness of the target and the size specification.
11820 The address of each match found is printed as well as a count of the
11821 number of matches found.
11823 The address of the last value found is stored in convenience variable
11825 A count of the number of matches is stored in @samp{$numfound}.
11827 For example, if stopped at the @code{printf} in this function:
11833 static char hello[] = "hello-hello";
11834 static struct @{ char c; short s; int i; @}
11835 __attribute__ ((packed)) mixed
11836 = @{ 'c', 0x1234, 0x87654321 @};
11837 printf ("%s\n", hello);
11842 you get during debugging:
11845 (gdb) find &hello[0], +sizeof(hello), "hello"
11846 0x804956d <hello.1620+6>
11848 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
11849 0x8049567 <hello.1620>
11850 0x804956d <hello.1620+6>
11852 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
11853 0x8049567 <hello.1620>
11855 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
11856 0x8049560 <mixed.1625>
11858 (gdb) print $numfound
11861 $2 = (void *) 0x8049560
11865 @section Value Sizes
11867 Whenever @value{GDBN} prints a value memory will be allocated within
11868 @value{GDBN} to hold the contents of the value. It is possible in
11869 some languages with dynamic typing systems, that an invalid program
11870 may indicate a value that is incorrectly large, this in turn may cause
11871 @value{GDBN} to try and allocate an overly large ammount of memory.
11874 @kindex set max-value-size
11875 @item set max-value-size @var{bytes}
11876 @itemx set max-value-size unlimited
11877 Set the maximum size of memory that @value{GDBN} will allocate for the
11878 contents of a value to @var{bytes}, trying to display a value that
11879 requires more memory than that will result in an error.
11881 Setting this variable does not effect values that have already been
11882 allocated within @value{GDBN}, only future allocations.
11884 There's a minimum size that @code{max-value-size} can be set to in
11885 order that @value{GDBN} can still operate correctly, this minimum is
11886 currently 16 bytes.
11888 The limit applies to the results of some subexpressions as well as to
11889 complete expressions. For example, an expression denoting a simple
11890 integer component, such as @code{x.y.z}, may fail if the size of
11891 @var{x.y} is dynamic and exceeds @var{bytes}. On the other hand,
11892 @value{GDBN} is sometimes clever; the expression @code{A[i]}, where
11893 @var{A} is an array variable with non-constant size, will generally
11894 succeed regardless of the bounds on @var{A}, as long as the component
11895 size is less than @var{bytes}.
11897 The default value of @code{max-value-size} is currently 64k.
11899 @kindex show max-value-size
11900 @item show max-value-size
11901 Show the maximum size of memory, in bytes, that @value{GDBN} will
11902 allocate for the contents of a value.
11905 @node Optimized Code
11906 @chapter Debugging Optimized Code
11907 @cindex optimized code, debugging
11908 @cindex debugging optimized code
11910 Almost all compilers support optimization. With optimization
11911 disabled, the compiler generates assembly code that corresponds
11912 directly to your source code, in a simplistic way. As the compiler
11913 applies more powerful optimizations, the generated assembly code
11914 diverges from your original source code. With help from debugging
11915 information generated by the compiler, @value{GDBN} can map from
11916 the running program back to constructs from your original source.
11918 @value{GDBN} is more accurate with optimization disabled. If you
11919 can recompile without optimization, it is easier to follow the
11920 progress of your program during debugging. But, there are many cases
11921 where you may need to debug an optimized version.
11923 When you debug a program compiled with @samp{-g -O}, remember that the
11924 optimizer has rearranged your code; the debugger shows you what is
11925 really there. Do not be too surprised when the execution path does not
11926 exactly match your source file! An extreme example: if you define a
11927 variable, but never use it, @value{GDBN} never sees that
11928 variable---because the compiler optimizes it out of existence.
11930 Some things do not work as well with @samp{-g -O} as with just
11931 @samp{-g}, particularly on machines with instruction scheduling. If in
11932 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
11933 please report it to us as a bug (including a test case!).
11934 @xref{Variables}, for more information about debugging optimized code.
11937 * Inline Functions:: How @value{GDBN} presents inlining
11938 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
11941 @node Inline Functions
11942 @section Inline Functions
11943 @cindex inline functions, debugging
11945 @dfn{Inlining} is an optimization that inserts a copy of the function
11946 body directly at each call site, instead of jumping to a shared
11947 routine. @value{GDBN} displays inlined functions just like
11948 non-inlined functions. They appear in backtraces. You can view their
11949 arguments and local variables, step into them with @code{step}, skip
11950 them with @code{next}, and escape from them with @code{finish}.
11951 You can check whether a function was inlined by using the
11952 @code{info frame} command.
11954 For @value{GDBN} to support inlined functions, the compiler must
11955 record information about inlining in the debug information ---
11956 @value{NGCC} using the @sc{dwarf 2} format does this, and several
11957 other compilers do also. @value{GDBN} only supports inlined functions
11958 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
11959 do not emit two required attributes (@samp{DW_AT_call_file} and
11960 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
11961 function calls with earlier versions of @value{NGCC}. It instead
11962 displays the arguments and local variables of inlined functions as
11963 local variables in the caller.
11965 The body of an inlined function is directly included at its call site;
11966 unlike a non-inlined function, there are no instructions devoted to
11967 the call. @value{GDBN} still pretends that the call site and the
11968 start of the inlined function are different instructions. Stepping to
11969 the call site shows the call site, and then stepping again shows
11970 the first line of the inlined function, even though no additional
11971 instructions are executed.
11973 This makes source-level debugging much clearer; you can see both the
11974 context of the call and then the effect of the call. Only stepping by
11975 a single instruction using @code{stepi} or @code{nexti} does not do
11976 this; single instruction steps always show the inlined body.
11978 There are some ways that @value{GDBN} does not pretend that inlined
11979 function calls are the same as normal calls:
11983 Setting breakpoints at the call site of an inlined function may not
11984 work, because the call site does not contain any code. @value{GDBN}
11985 may incorrectly move the breakpoint to the next line of the enclosing
11986 function, after the call. This limitation will be removed in a future
11987 version of @value{GDBN}; until then, set a breakpoint on an earlier line
11988 or inside the inlined function instead.
11991 @value{GDBN} cannot locate the return value of inlined calls after
11992 using the @code{finish} command. This is a limitation of compiler-generated
11993 debugging information; after @code{finish}, you can step to the next line
11994 and print a variable where your program stored the return value.
11998 @node Tail Call Frames
11999 @section Tail Call Frames
12000 @cindex tail call frames, debugging
12002 Function @code{B} can call function @code{C} in its very last statement. In
12003 unoptimized compilation the call of @code{C} is immediately followed by return
12004 instruction at the end of @code{B} code. Optimizing compiler may replace the
12005 call and return in function @code{B} into one jump to function @code{C}
12006 instead. Such use of a jump instruction is called @dfn{tail call}.
12008 During execution of function @code{C}, there will be no indication in the
12009 function call stack frames that it was tail-called from @code{B}. If function
12010 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
12011 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
12012 some cases @value{GDBN} can determine that @code{C} was tail-called from
12013 @code{B}, and it will then create fictitious call frame for that, with the
12014 return address set up as if @code{B} called @code{C} normally.
12016 This functionality is currently supported only by DWARF 2 debugging format and
12017 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
12018 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
12021 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
12022 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
12026 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
12028 Stack level 1, frame at 0x7fffffffda30:
12029 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
12030 tail call frame, caller of frame at 0x7fffffffda30
12031 source language c++.
12032 Arglist at unknown address.
12033 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
12036 The detection of all the possible code path executions can find them ambiguous.
12037 There is no execution history stored (possible @ref{Reverse Execution} is never
12038 used for this purpose) and the last known caller could have reached the known
12039 callee by multiple different jump sequences. In such case @value{GDBN} still
12040 tries to show at least all the unambiguous top tail callers and all the
12041 unambiguous bottom tail calees, if any.
12044 @anchor{set debug entry-values}
12045 @item set debug entry-values
12046 @kindex set debug entry-values
12047 When set to on, enables printing of analysis messages for both frame argument
12048 values at function entry and tail calls. It will show all the possible valid
12049 tail calls code paths it has considered. It will also print the intersection
12050 of them with the final unambiguous (possibly partial or even empty) code path
12053 @item show debug entry-values
12054 @kindex show debug entry-values
12055 Show the current state of analysis messages printing for both frame argument
12056 values at function entry and tail calls.
12059 The analysis messages for tail calls can for example show why the virtual tail
12060 call frame for function @code{c} has not been recognized (due to the indirect
12061 reference by variable @code{x}):
12064 static void __attribute__((noinline, noclone)) c (void);
12065 void (*x) (void) = c;
12066 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12067 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
12068 int main (void) @{ x (); return 0; @}
12070 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
12071 DW_TAG_GNU_call_site 0x40039a in main
12073 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12076 #1 0x000000000040039a in main () at t.c:5
12079 Another possibility is an ambiguous virtual tail call frames resolution:
12083 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
12084 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
12085 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
12086 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
12087 static void __attribute__((noinline, noclone)) b (void)
12088 @{ if (i) c (); else e (); @}
12089 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
12090 int main (void) @{ a (); return 0; @}
12092 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
12093 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
12094 tailcall: reduced: 0x4004d2(a) |
12097 #1 0x00000000004004d2 in a () at t.c:8
12098 #2 0x0000000000400395 in main () at t.c:9
12101 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
12102 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
12104 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
12105 @ifset HAVE_MAKEINFO_CLICK
12106 @set ARROW @click{}
12107 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
12108 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
12110 @ifclear HAVE_MAKEINFO_CLICK
12112 @set CALLSEQ1B @value{CALLSEQ1A}
12113 @set CALLSEQ2B @value{CALLSEQ2A}
12116 Frames #0 and #2 are real, #1 is a virtual tail call frame.
12117 The code can have possible execution paths @value{CALLSEQ1B} or
12118 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
12120 @code{initial:} state shows some random possible calling sequence @value{GDBN}
12121 has found. It then finds another possible calling sequcen - that one is
12122 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
12123 printed as the @code{reduced:} calling sequence. That one could have many
12124 futher @code{compare:} and @code{reduced:} statements as long as there remain
12125 any non-ambiguous sequence entries.
12127 For the frame of function @code{b} in both cases there are different possible
12128 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
12129 also ambigous. The only non-ambiguous frame is the one for function @code{a},
12130 therefore this one is displayed to the user while the ambiguous frames are
12133 There can be also reasons why printing of frame argument values at function
12138 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
12139 static void __attribute__((noinline, noclone)) a (int i);
12140 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
12141 static void __attribute__((noinline, noclone)) a (int i)
12142 @{ if (i) b (i - 1); else c (0); @}
12143 int main (void) @{ a (5); return 0; @}
12146 #0 c (i=i@@entry=0) at t.c:2
12147 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
12148 function "a" at 0x400420 can call itself via tail calls
12149 i=<optimized out>) at t.c:6
12150 #2 0x000000000040036e in main () at t.c:7
12153 @value{GDBN} cannot find out from the inferior state if and how many times did
12154 function @code{a} call itself (via function @code{b}) as these calls would be
12155 tail calls. Such tail calls would modify thue @code{i} variable, therefore
12156 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
12157 prints @code{<optimized out>} instead.
12160 @chapter C Preprocessor Macros
12162 Some languages, such as C and C@t{++}, provide a way to define and invoke
12163 ``preprocessor macros'' which expand into strings of tokens.
12164 @value{GDBN} can evaluate expressions containing macro invocations, show
12165 the result of macro expansion, and show a macro's definition, including
12166 where it was defined.
12168 You may need to compile your program specially to provide @value{GDBN}
12169 with information about preprocessor macros. Most compilers do not
12170 include macros in their debugging information, even when you compile
12171 with the @option{-g} flag. @xref{Compilation}.
12173 A program may define a macro at one point, remove that definition later,
12174 and then provide a different definition after that. Thus, at different
12175 points in the program, a macro may have different definitions, or have
12176 no definition at all. If there is a current stack frame, @value{GDBN}
12177 uses the macros in scope at that frame's source code line. Otherwise,
12178 @value{GDBN} uses the macros in scope at the current listing location;
12181 Whenever @value{GDBN} evaluates an expression, it always expands any
12182 macro invocations present in the expression. @value{GDBN} also provides
12183 the following commands for working with macros explicitly.
12187 @kindex macro expand
12188 @cindex macro expansion, showing the results of preprocessor
12189 @cindex preprocessor macro expansion, showing the results of
12190 @cindex expanding preprocessor macros
12191 @item macro expand @var{expression}
12192 @itemx macro exp @var{expression}
12193 Show the results of expanding all preprocessor macro invocations in
12194 @var{expression}. Since @value{GDBN} simply expands macros, but does
12195 not parse the result, @var{expression} need not be a valid expression;
12196 it can be any string of tokens.
12199 @item macro expand-once @var{expression}
12200 @itemx macro exp1 @var{expression}
12201 @cindex expand macro once
12202 @i{(This command is not yet implemented.)} Show the results of
12203 expanding those preprocessor macro invocations that appear explicitly in
12204 @var{expression}. Macro invocations appearing in that expansion are
12205 left unchanged. This command allows you to see the effect of a
12206 particular macro more clearly, without being confused by further
12207 expansions. Since @value{GDBN} simply expands macros, but does not
12208 parse the result, @var{expression} need not be a valid expression; it
12209 can be any string of tokens.
12212 @cindex macro definition, showing
12213 @cindex definition of a macro, showing
12214 @cindex macros, from debug info
12215 @item info macro [-a|-all] [--] @var{macro}
12216 Show the current definition or all definitions of the named @var{macro},
12217 and describe the source location or compiler command-line where that
12218 definition was established. The optional double dash is to signify the end of
12219 argument processing and the beginning of @var{macro} for non C-like macros where
12220 the macro may begin with a hyphen.
12222 @kindex info macros
12223 @item info macros @var{location}
12224 Show all macro definitions that are in effect at the location specified
12225 by @var{location}, and describe the source location or compiler
12226 command-line where those definitions were established.
12228 @kindex macro define
12229 @cindex user-defined macros
12230 @cindex defining macros interactively
12231 @cindex macros, user-defined
12232 @item macro define @var{macro} @var{replacement-list}
12233 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
12234 Introduce a definition for a preprocessor macro named @var{macro},
12235 invocations of which are replaced by the tokens given in
12236 @var{replacement-list}. The first form of this command defines an
12237 ``object-like'' macro, which takes no arguments; the second form
12238 defines a ``function-like'' macro, which takes the arguments given in
12241 A definition introduced by this command is in scope in every
12242 expression evaluated in @value{GDBN}, until it is removed with the
12243 @code{macro undef} command, described below. The definition overrides
12244 all definitions for @var{macro} present in the program being debugged,
12245 as well as any previous user-supplied definition.
12247 @kindex macro undef
12248 @item macro undef @var{macro}
12249 Remove any user-supplied definition for the macro named @var{macro}.
12250 This command only affects definitions provided with the @code{macro
12251 define} command, described above; it cannot remove definitions present
12252 in the program being debugged.
12256 List all the macros defined using the @code{macro define} command.
12259 @cindex macros, example of debugging with
12260 Here is a transcript showing the above commands in action. First, we
12261 show our source files:
12266 #include "sample.h"
12269 #define ADD(x) (M + x)
12274 printf ("Hello, world!\n");
12276 printf ("We're so creative.\n");
12278 printf ("Goodbye, world!\n");
12285 Now, we compile the program using the @sc{gnu} C compiler,
12286 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
12287 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
12288 and @option{-gdwarf-4}; we recommend always choosing the most recent
12289 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
12290 includes information about preprocessor macros in the debugging
12294 $ gcc -gdwarf-2 -g3 sample.c -o sample
12298 Now, we start @value{GDBN} on our sample program:
12302 GNU gdb 2002-05-06-cvs
12303 Copyright 2002 Free Software Foundation, Inc.
12304 GDB is free software, @dots{}
12308 We can expand macros and examine their definitions, even when the
12309 program is not running. @value{GDBN} uses the current listing position
12310 to decide which macro definitions are in scope:
12313 (@value{GDBP}) list main
12316 5 #define ADD(x) (M + x)
12321 10 printf ("Hello, world!\n");
12323 12 printf ("We're so creative.\n");
12324 (@value{GDBP}) info macro ADD
12325 Defined at /home/jimb/gdb/macros/play/sample.c:5
12326 #define ADD(x) (M + x)
12327 (@value{GDBP}) info macro Q
12328 Defined at /home/jimb/gdb/macros/play/sample.h:1
12329 included at /home/jimb/gdb/macros/play/sample.c:2
12331 (@value{GDBP}) macro expand ADD(1)
12332 expands to: (42 + 1)
12333 (@value{GDBP}) macro expand-once ADD(1)
12334 expands to: once (M + 1)
12338 In the example above, note that @code{macro expand-once} expands only
12339 the macro invocation explicit in the original text --- the invocation of
12340 @code{ADD} --- but does not expand the invocation of the macro @code{M},
12341 which was introduced by @code{ADD}.
12343 Once the program is running, @value{GDBN} uses the macro definitions in
12344 force at the source line of the current stack frame:
12347 (@value{GDBP}) break main
12348 Breakpoint 1 at 0x8048370: file sample.c, line 10.
12350 Starting program: /home/jimb/gdb/macros/play/sample
12352 Breakpoint 1, main () at sample.c:10
12353 10 printf ("Hello, world!\n");
12357 At line 10, the definition of the macro @code{N} at line 9 is in force:
12360 (@value{GDBP}) info macro N
12361 Defined at /home/jimb/gdb/macros/play/sample.c:9
12363 (@value{GDBP}) macro expand N Q M
12364 expands to: 28 < 42
12365 (@value{GDBP}) print N Q M
12370 As we step over directives that remove @code{N}'s definition, and then
12371 give it a new definition, @value{GDBN} finds the definition (or lack
12372 thereof) in force at each point:
12375 (@value{GDBP}) next
12377 12 printf ("We're so creative.\n");
12378 (@value{GDBP}) info macro N
12379 The symbol `N' has no definition as a C/C++ preprocessor macro
12380 at /home/jimb/gdb/macros/play/sample.c:12
12381 (@value{GDBP}) next
12383 14 printf ("Goodbye, world!\n");
12384 (@value{GDBP}) info macro N
12385 Defined at /home/jimb/gdb/macros/play/sample.c:13
12387 (@value{GDBP}) macro expand N Q M
12388 expands to: 1729 < 42
12389 (@value{GDBP}) print N Q M
12394 In addition to source files, macros can be defined on the compilation command
12395 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
12396 such a way, @value{GDBN} displays the location of their definition as line zero
12397 of the source file submitted to the compiler.
12400 (@value{GDBP}) info macro __STDC__
12401 Defined at /home/jimb/gdb/macros/play/sample.c:0
12408 @chapter Tracepoints
12409 @c This chapter is based on the documentation written by Michael
12410 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
12412 @cindex tracepoints
12413 In some applications, it is not feasible for the debugger to interrupt
12414 the program's execution long enough for the developer to learn
12415 anything helpful about its behavior. If the program's correctness
12416 depends on its real-time behavior, delays introduced by a debugger
12417 might cause the program to change its behavior drastically, or perhaps
12418 fail, even when the code itself is correct. It is useful to be able
12419 to observe the program's behavior without interrupting it.
12421 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
12422 specify locations in the program, called @dfn{tracepoints}, and
12423 arbitrary expressions to evaluate when those tracepoints are reached.
12424 Later, using the @code{tfind} command, you can examine the values
12425 those expressions had when the program hit the tracepoints. The
12426 expressions may also denote objects in memory---structures or arrays,
12427 for example---whose values @value{GDBN} should record; while visiting
12428 a particular tracepoint, you may inspect those objects as if they were
12429 in memory at that moment. However, because @value{GDBN} records these
12430 values without interacting with you, it can do so quickly and
12431 unobtrusively, hopefully not disturbing the program's behavior.
12433 The tracepoint facility is currently available only for remote
12434 targets. @xref{Targets}. In addition, your remote target must know
12435 how to collect trace data. This functionality is implemented in the
12436 remote stub; however, none of the stubs distributed with @value{GDBN}
12437 support tracepoints as of this writing. The format of the remote
12438 packets used to implement tracepoints are described in @ref{Tracepoint
12441 It is also possible to get trace data from a file, in a manner reminiscent
12442 of corefiles; you specify the filename, and use @code{tfind} to search
12443 through the file. @xref{Trace Files}, for more details.
12445 This chapter describes the tracepoint commands and features.
12448 * Set Tracepoints::
12449 * Analyze Collected Data::
12450 * Tracepoint Variables::
12454 @node Set Tracepoints
12455 @section Commands to Set Tracepoints
12457 Before running such a @dfn{trace experiment}, an arbitrary number of
12458 tracepoints can be set. A tracepoint is actually a special type of
12459 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
12460 standard breakpoint commands. For instance, as with breakpoints,
12461 tracepoint numbers are successive integers starting from one, and many
12462 of the commands associated with tracepoints take the tracepoint number
12463 as their argument, to identify which tracepoint to work on.
12465 For each tracepoint, you can specify, in advance, some arbitrary set
12466 of data that you want the target to collect in the trace buffer when
12467 it hits that tracepoint. The collected data can include registers,
12468 local variables, or global data. Later, you can use @value{GDBN}
12469 commands to examine the values these data had at the time the
12470 tracepoint was hit.
12472 Tracepoints do not support every breakpoint feature. Ignore counts on
12473 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
12474 commands when they are hit. Tracepoints may not be thread-specific
12477 @cindex fast tracepoints
12478 Some targets may support @dfn{fast tracepoints}, which are inserted in
12479 a different way (such as with a jump instead of a trap), that is
12480 faster but possibly restricted in where they may be installed.
12482 @cindex static tracepoints
12483 @cindex markers, static tracepoints
12484 @cindex probing markers, static tracepoints
12485 Regular and fast tracepoints are dynamic tracing facilities, meaning
12486 that they can be used to insert tracepoints at (almost) any location
12487 in the target. Some targets may also support controlling @dfn{static
12488 tracepoints} from @value{GDBN}. With static tracing, a set of
12489 instrumentation points, also known as @dfn{markers}, are embedded in
12490 the target program, and can be activated or deactivated by name or
12491 address. These are usually placed at locations which facilitate
12492 investigating what the target is actually doing. @value{GDBN}'s
12493 support for static tracing includes being able to list instrumentation
12494 points, and attach them with @value{GDBN} defined high level
12495 tracepoints that expose the whole range of convenience of
12496 @value{GDBN}'s tracepoints support. Namely, support for collecting
12497 registers values and values of global or local (to the instrumentation
12498 point) variables; tracepoint conditions and trace state variables.
12499 The act of installing a @value{GDBN} static tracepoint on an
12500 instrumentation point, or marker, is referred to as @dfn{probing} a
12501 static tracepoint marker.
12503 @code{gdbserver} supports tracepoints on some target systems.
12504 @xref{Server,,Tracepoints support in @code{gdbserver}}.
12506 This section describes commands to set tracepoints and associated
12507 conditions and actions.
12510 * Create and Delete Tracepoints::
12511 * Enable and Disable Tracepoints::
12512 * Tracepoint Passcounts::
12513 * Tracepoint Conditions::
12514 * Trace State Variables::
12515 * Tracepoint Actions::
12516 * Listing Tracepoints::
12517 * Listing Static Tracepoint Markers::
12518 * Starting and Stopping Trace Experiments::
12519 * Tracepoint Restrictions::
12522 @node Create and Delete Tracepoints
12523 @subsection Create and Delete Tracepoints
12526 @cindex set tracepoint
12528 @item trace @var{location}
12529 The @code{trace} command is very similar to the @code{break} command.
12530 Its argument @var{location} can be any valid location.
12531 @xref{Specify Location}. The @code{trace} command defines a tracepoint,
12532 which is a point in the target program where the debugger will briefly stop,
12533 collect some data, and then allow the program to continue. Setting a tracepoint
12534 or changing its actions takes effect immediately if the remote stub
12535 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
12537 If remote stub doesn't support the @samp{InstallInTrace} feature, all
12538 these changes don't take effect until the next @code{tstart}
12539 command, and once a trace experiment is running, further changes will
12540 not have any effect until the next trace experiment starts. In addition,
12541 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
12542 address is not yet resolved. (This is similar to pending breakpoints.)
12543 Pending tracepoints are not downloaded to the target and not installed
12544 until they are resolved. The resolution of pending tracepoints requires
12545 @value{GDBN} support---when debugging with the remote target, and
12546 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
12547 tracing}), pending tracepoints can not be resolved (and downloaded to
12548 the remote stub) while @value{GDBN} is disconnected.
12550 Here are some examples of using the @code{trace} command:
12553 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
12555 (@value{GDBP}) @b{trace +2} // 2 lines forward
12557 (@value{GDBP}) @b{trace my_function} // first source line of function
12559 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
12561 (@value{GDBP}) @b{trace *0x2117c4} // an address
12565 You can abbreviate @code{trace} as @code{tr}.
12567 @item trace @var{location} if @var{cond}
12568 Set a tracepoint with condition @var{cond}; evaluate the expression
12569 @var{cond} each time the tracepoint is reached, and collect data only
12570 if the value is nonzero---that is, if @var{cond} evaluates as true.
12571 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
12572 information on tracepoint conditions.
12574 @item ftrace @var{location} [ if @var{cond} ]
12575 @cindex set fast tracepoint
12576 @cindex fast tracepoints, setting
12578 The @code{ftrace} command sets a fast tracepoint. For targets that
12579 support them, fast tracepoints will use a more efficient but possibly
12580 less general technique to trigger data collection, such as a jump
12581 instruction instead of a trap, or some sort of hardware support. It
12582 may not be possible to create a fast tracepoint at the desired
12583 location, in which case the command will exit with an explanatory
12586 @value{GDBN} handles arguments to @code{ftrace} exactly as for
12589 On 32-bit x86-architecture systems, fast tracepoints normally need to
12590 be placed at an instruction that is 5 bytes or longer, but can be
12591 placed at 4-byte instructions if the low 64K of memory of the target
12592 program is available to install trampolines. Some Unix-type systems,
12593 such as @sc{gnu}/Linux, exclude low addresses from the program's
12594 address space; but for instance with the Linux kernel it is possible
12595 to let @value{GDBN} use this area by doing a @command{sysctl} command
12596 to set the @code{mmap_min_addr} kernel parameter, as in
12599 sudo sysctl -w vm.mmap_min_addr=32768
12603 which sets the low address to 32K, which leaves plenty of room for
12604 trampolines. The minimum address should be set to a page boundary.
12606 @item strace @var{location} [ if @var{cond} ]
12607 @cindex set static tracepoint
12608 @cindex static tracepoints, setting
12609 @cindex probe static tracepoint marker
12611 The @code{strace} command sets a static tracepoint. For targets that
12612 support it, setting a static tracepoint probes a static
12613 instrumentation point, or marker, found at @var{location}. It may not
12614 be possible to set a static tracepoint at the desired location, in
12615 which case the command will exit with an explanatory message.
12617 @value{GDBN} handles arguments to @code{strace} exactly as for
12618 @code{trace}, with the addition that the user can also specify
12619 @code{-m @var{marker}} as @var{location}. This probes the marker
12620 identified by the @var{marker} string identifier. This identifier
12621 depends on the static tracepoint backend library your program is
12622 using. You can find all the marker identifiers in the @samp{ID} field
12623 of the @code{info static-tracepoint-markers} command output.
12624 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
12625 Markers}. For example, in the following small program using the UST
12631 trace_mark(ust, bar33, "str %s", "FOOBAZ");
12636 the marker id is composed of joining the first two arguments to the
12637 @code{trace_mark} call with a slash, which translates to:
12640 (@value{GDBP}) info static-tracepoint-markers
12641 Cnt Enb ID Address What
12642 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
12648 so you may probe the marker above with:
12651 (@value{GDBP}) strace -m ust/bar33
12654 Static tracepoints accept an extra collect action --- @code{collect
12655 $_sdata}. This collects arbitrary user data passed in the probe point
12656 call to the tracing library. In the UST example above, you'll see
12657 that the third argument to @code{trace_mark} is a printf-like format
12658 string. The user data is then the result of running that formating
12659 string against the following arguments. Note that @code{info
12660 static-tracepoint-markers} command output lists that format string in
12661 the @samp{Data:} field.
12663 You can inspect this data when analyzing the trace buffer, by printing
12664 the $_sdata variable like any other variable available to
12665 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
12668 @cindex last tracepoint number
12669 @cindex recent tracepoint number
12670 @cindex tracepoint number
12671 The convenience variable @code{$tpnum} records the tracepoint number
12672 of the most recently set tracepoint.
12674 @kindex delete tracepoint
12675 @cindex tracepoint deletion
12676 @item delete tracepoint @r{[}@var{num}@r{]}
12677 Permanently delete one or more tracepoints. With no argument, the
12678 default is to delete all tracepoints. Note that the regular
12679 @code{delete} command can remove tracepoints also.
12684 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
12686 (@value{GDBP}) @b{delete trace} // remove all tracepoints
12690 You can abbreviate this command as @code{del tr}.
12693 @node Enable and Disable Tracepoints
12694 @subsection Enable and Disable Tracepoints
12696 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
12699 @kindex disable tracepoint
12700 @item disable tracepoint @r{[}@var{num}@r{]}
12701 Disable tracepoint @var{num}, or all tracepoints if no argument
12702 @var{num} is given. A disabled tracepoint will have no effect during
12703 a trace experiment, but it is not forgotten. You can re-enable
12704 a disabled tracepoint using the @code{enable tracepoint} command.
12705 If the command is issued during a trace experiment and the debug target
12706 has support for disabling tracepoints during a trace experiment, then the
12707 change will be effective immediately. Otherwise, it will be applied to the
12708 next trace experiment.
12710 @kindex enable tracepoint
12711 @item enable tracepoint @r{[}@var{num}@r{]}
12712 Enable tracepoint @var{num}, or all tracepoints. If this command is
12713 issued during a trace experiment and the debug target supports enabling
12714 tracepoints during a trace experiment, then the enabled tracepoints will
12715 become effective immediately. Otherwise, they will become effective the
12716 next time a trace experiment is run.
12719 @node Tracepoint Passcounts
12720 @subsection Tracepoint Passcounts
12724 @cindex tracepoint pass count
12725 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
12726 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
12727 automatically stop a trace experiment. If a tracepoint's passcount is
12728 @var{n}, then the trace experiment will be automatically stopped on
12729 the @var{n}'th time that tracepoint is hit. If the tracepoint number
12730 @var{num} is not specified, the @code{passcount} command sets the
12731 passcount of the most recently defined tracepoint. If no passcount is
12732 given, the trace experiment will run until stopped explicitly by the
12738 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
12739 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
12741 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
12742 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
12743 (@value{GDBP}) @b{trace foo}
12744 (@value{GDBP}) @b{pass 3}
12745 (@value{GDBP}) @b{trace bar}
12746 (@value{GDBP}) @b{pass 2}
12747 (@value{GDBP}) @b{trace baz}
12748 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
12749 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
12750 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
12751 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
12755 @node Tracepoint Conditions
12756 @subsection Tracepoint Conditions
12757 @cindex conditional tracepoints
12758 @cindex tracepoint conditions
12760 The simplest sort of tracepoint collects data every time your program
12761 reaches a specified place. You can also specify a @dfn{condition} for
12762 a tracepoint. A condition is just a Boolean expression in your
12763 programming language (@pxref{Expressions, ,Expressions}). A
12764 tracepoint with a condition evaluates the expression each time your
12765 program reaches it, and data collection happens only if the condition
12768 Tracepoint conditions can be specified when a tracepoint is set, by
12769 using @samp{if} in the arguments to the @code{trace} command.
12770 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
12771 also be set or changed at any time with the @code{condition} command,
12772 just as with breakpoints.
12774 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
12775 the conditional expression itself. Instead, @value{GDBN} encodes the
12776 expression into an agent expression (@pxref{Agent Expressions})
12777 suitable for execution on the target, independently of @value{GDBN}.
12778 Global variables become raw memory locations, locals become stack
12779 accesses, and so forth.
12781 For instance, suppose you have a function that is usually called
12782 frequently, but should not be called after an error has occurred. You
12783 could use the following tracepoint command to collect data about calls
12784 of that function that happen while the error code is propagating
12785 through the program; an unconditional tracepoint could end up
12786 collecting thousands of useless trace frames that you would have to
12790 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
12793 @node Trace State Variables
12794 @subsection Trace State Variables
12795 @cindex trace state variables
12797 A @dfn{trace state variable} is a special type of variable that is
12798 created and managed by target-side code. The syntax is the same as
12799 that for GDB's convenience variables (a string prefixed with ``$''),
12800 but they are stored on the target. They must be created explicitly,
12801 using a @code{tvariable} command. They are always 64-bit signed
12804 Trace state variables are remembered by @value{GDBN}, and downloaded
12805 to the target along with tracepoint information when the trace
12806 experiment starts. There are no intrinsic limits on the number of
12807 trace state variables, beyond memory limitations of the target.
12809 @cindex convenience variables, and trace state variables
12810 Although trace state variables are managed by the target, you can use
12811 them in print commands and expressions as if they were convenience
12812 variables; @value{GDBN} will get the current value from the target
12813 while the trace experiment is running. Trace state variables share
12814 the same namespace as other ``$'' variables, which means that you
12815 cannot have trace state variables with names like @code{$23} or
12816 @code{$pc}, nor can you have a trace state variable and a convenience
12817 variable with the same name.
12821 @item tvariable $@var{name} [ = @var{expression} ]
12823 The @code{tvariable} command creates a new trace state variable named
12824 @code{$@var{name}}, and optionally gives it an initial value of
12825 @var{expression}. The @var{expression} is evaluated when this command is
12826 entered; the result will be converted to an integer if possible,
12827 otherwise @value{GDBN} will report an error. A subsequent
12828 @code{tvariable} command specifying the same name does not create a
12829 variable, but instead assigns the supplied initial value to the
12830 existing variable of that name, overwriting any previous initial
12831 value. The default initial value is 0.
12833 @item info tvariables
12834 @kindex info tvariables
12835 List all the trace state variables along with their initial values.
12836 Their current values may also be displayed, if the trace experiment is
12839 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
12840 @kindex delete tvariable
12841 Delete the given trace state variables, or all of them if no arguments
12846 @node Tracepoint Actions
12847 @subsection Tracepoint Action Lists
12851 @cindex tracepoint actions
12852 @item actions @r{[}@var{num}@r{]}
12853 This command will prompt for a list of actions to be taken when the
12854 tracepoint is hit. If the tracepoint number @var{num} is not
12855 specified, this command sets the actions for the one that was most
12856 recently defined (so that you can define a tracepoint and then say
12857 @code{actions} without bothering about its number). You specify the
12858 actions themselves on the following lines, one action at a time, and
12859 terminate the actions list with a line containing just @code{end}. So
12860 far, the only defined actions are @code{collect}, @code{teval}, and
12861 @code{while-stepping}.
12863 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
12864 Commands, ,Breakpoint Command Lists}), except that only the defined
12865 actions are allowed; any other @value{GDBN} command is rejected.
12867 @cindex remove actions from a tracepoint
12868 To remove all actions from a tracepoint, type @samp{actions @var{num}}
12869 and follow it immediately with @samp{end}.
12872 (@value{GDBP}) @b{collect @var{data}} // collect some data
12874 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
12876 (@value{GDBP}) @b{end} // signals the end of actions.
12879 In the following example, the action list begins with @code{collect}
12880 commands indicating the things to be collected when the tracepoint is
12881 hit. Then, in order to single-step and collect additional data
12882 following the tracepoint, a @code{while-stepping} command is used,
12883 followed by the list of things to be collected after each step in a
12884 sequence of single steps. The @code{while-stepping} command is
12885 terminated by its own separate @code{end} command. Lastly, the action
12886 list is terminated by an @code{end} command.
12889 (@value{GDBP}) @b{trace foo}
12890 (@value{GDBP}) @b{actions}
12891 Enter actions for tracepoint 1, one per line:
12894 > while-stepping 12
12895 > collect $pc, arr[i]
12900 @kindex collect @r{(tracepoints)}
12901 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
12902 Collect values of the given expressions when the tracepoint is hit.
12903 This command accepts a comma-separated list of any valid expressions.
12904 In addition to global, static, or local variables, the following
12905 special arguments are supported:
12909 Collect all registers.
12912 Collect all function arguments.
12915 Collect all local variables.
12918 Collect the return address. This is helpful if you want to see more
12921 @emph{Note:} The return address location can not always be reliably
12922 determined up front, and the wrong address / registers may end up
12923 collected instead. On some architectures the reliability is higher
12924 for tracepoints at function entry, while on others it's the opposite.
12925 When this happens, backtracing will stop because the return address is
12926 found unavailable (unless another collect rule happened to match it).
12929 Collects the number of arguments from the static probe at which the
12930 tracepoint is located.
12931 @xref{Static Probe Points}.
12933 @item $_probe_arg@var{n}
12934 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
12935 from the static probe at which the tracepoint is located.
12936 @xref{Static Probe Points}.
12939 @vindex $_sdata@r{, collect}
12940 Collect static tracepoint marker specific data. Only available for
12941 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
12942 Lists}. On the UST static tracepoints library backend, an
12943 instrumentation point resembles a @code{printf} function call. The
12944 tracing library is able to collect user specified data formatted to a
12945 character string using the format provided by the programmer that
12946 instrumented the program. Other backends have similar mechanisms.
12947 Here's an example of a UST marker call:
12950 const char master_name[] = "$your_name";
12951 trace_mark(channel1, marker1, "hello %s", master_name)
12954 In this case, collecting @code{$_sdata} collects the string
12955 @samp{hello $yourname}. When analyzing the trace buffer, you can
12956 inspect @samp{$_sdata} like any other variable available to
12960 You can give several consecutive @code{collect} commands, each one
12961 with a single argument, or one @code{collect} command with several
12962 arguments separated by commas; the effect is the same.
12964 The optional @var{mods} changes the usual handling of the arguments.
12965 @code{s} requests that pointers to chars be handled as strings, in
12966 particular collecting the contents of the memory being pointed at, up
12967 to the first zero. The upper bound is by default the value of the
12968 @code{print elements} variable; if @code{s} is followed by a decimal
12969 number, that is the upper bound instead. So for instance
12970 @samp{collect/s25 mystr} collects as many as 25 characters at
12973 The command @code{info scope} (@pxref{Symbols, info scope}) is
12974 particularly useful for figuring out what data to collect.
12976 @kindex teval @r{(tracepoints)}
12977 @item teval @var{expr1}, @var{expr2}, @dots{}
12978 Evaluate the given expressions when the tracepoint is hit. This
12979 command accepts a comma-separated list of expressions. The results
12980 are discarded, so this is mainly useful for assigning values to trace
12981 state variables (@pxref{Trace State Variables}) without adding those
12982 values to the trace buffer, as would be the case if the @code{collect}
12985 @kindex while-stepping @r{(tracepoints)}
12986 @item while-stepping @var{n}
12987 Perform @var{n} single-step instruction traces after the tracepoint,
12988 collecting new data after each step. The @code{while-stepping}
12989 command is followed by the list of what to collect while stepping
12990 (followed by its own @code{end} command):
12993 > while-stepping 12
12994 > collect $regs, myglobal
13000 Note that @code{$pc} is not automatically collected by
13001 @code{while-stepping}; you need to explicitly collect that register if
13002 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
13005 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
13006 @kindex set default-collect
13007 @cindex default collection action
13008 This variable is a list of expressions to collect at each tracepoint
13009 hit. It is effectively an additional @code{collect} action prepended
13010 to every tracepoint action list. The expressions are parsed
13011 individually for each tracepoint, so for instance a variable named
13012 @code{xyz} may be interpreted as a global for one tracepoint, and a
13013 local for another, as appropriate to the tracepoint's location.
13015 @item show default-collect
13016 @kindex show default-collect
13017 Show the list of expressions that are collected by default at each
13022 @node Listing Tracepoints
13023 @subsection Listing Tracepoints
13026 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
13027 @kindex info tp @r{[}@var{n}@dots{}@r{]}
13028 @cindex information about tracepoints
13029 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
13030 Display information about the tracepoint @var{num}. If you don't
13031 specify a tracepoint number, displays information about all the
13032 tracepoints defined so far. The format is similar to that used for
13033 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
13034 command, simply restricting itself to tracepoints.
13036 A tracepoint's listing may include additional information specific to
13041 its passcount as given by the @code{passcount @var{n}} command
13044 the state about installed on target of each location
13048 (@value{GDBP}) @b{info trace}
13049 Num Type Disp Enb Address What
13050 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
13052 collect globfoo, $regs
13057 2 tracepoint keep y <MULTIPLE>
13059 2.1 y 0x0804859c in func4 at change-loc.h:35
13060 installed on target
13061 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
13062 installed on target
13063 2.3 y <PENDING> set_tracepoint
13064 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
13065 not installed on target
13070 This command can be abbreviated @code{info tp}.
13073 @node Listing Static Tracepoint Markers
13074 @subsection Listing Static Tracepoint Markers
13077 @kindex info static-tracepoint-markers
13078 @cindex information about static tracepoint markers
13079 @item info static-tracepoint-markers
13080 Display information about all static tracepoint markers defined in the
13083 For each marker, the following columns are printed:
13087 An incrementing counter, output to help readability. This is not a
13090 The marker ID, as reported by the target.
13091 @item Enabled or Disabled
13092 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
13093 that are not enabled.
13095 Where the marker is in your program, as a memory address.
13097 Where the marker is in the source for your program, as a file and line
13098 number. If the debug information included in the program does not
13099 allow @value{GDBN} to locate the source of the marker, this column
13100 will be left blank.
13104 In addition, the following information may be printed for each marker:
13108 User data passed to the tracing library by the marker call. In the
13109 UST backend, this is the format string passed as argument to the
13111 @item Static tracepoints probing the marker
13112 The list of static tracepoints attached to the marker.
13116 (@value{GDBP}) info static-tracepoint-markers
13117 Cnt ID Enb Address What
13118 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
13119 Data: number1 %d number2 %d
13120 Probed by static tracepoints: #2
13121 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
13127 @node Starting and Stopping Trace Experiments
13128 @subsection Starting and Stopping Trace Experiments
13131 @kindex tstart [ @var{notes} ]
13132 @cindex start a new trace experiment
13133 @cindex collected data discarded
13135 This command starts the trace experiment, and begins collecting data.
13136 It has the side effect of discarding all the data collected in the
13137 trace buffer during the previous trace experiment. If any arguments
13138 are supplied, they are taken as a note and stored with the trace
13139 experiment's state. The notes may be arbitrary text, and are
13140 especially useful with disconnected tracing in a multi-user context;
13141 the notes can explain what the trace is doing, supply user contact
13142 information, and so forth.
13144 @kindex tstop [ @var{notes} ]
13145 @cindex stop a running trace experiment
13147 This command stops the trace experiment. If any arguments are
13148 supplied, they are recorded with the experiment as a note. This is
13149 useful if you are stopping a trace started by someone else, for
13150 instance if the trace is interfering with the system's behavior and
13151 needs to be stopped quickly.
13153 @strong{Note}: a trace experiment and data collection may stop
13154 automatically if any tracepoint's passcount is reached
13155 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
13158 @cindex status of trace data collection
13159 @cindex trace experiment, status of
13161 This command displays the status of the current trace data
13165 Here is an example of the commands we described so far:
13168 (@value{GDBP}) @b{trace gdb_c_test}
13169 (@value{GDBP}) @b{actions}
13170 Enter actions for tracepoint #1, one per line.
13171 > collect $regs,$locals,$args
13172 > while-stepping 11
13176 (@value{GDBP}) @b{tstart}
13177 [time passes @dots{}]
13178 (@value{GDBP}) @b{tstop}
13181 @anchor{disconnected tracing}
13182 @cindex disconnected tracing
13183 You can choose to continue running the trace experiment even if
13184 @value{GDBN} disconnects from the target, voluntarily or
13185 involuntarily. For commands such as @code{detach}, the debugger will
13186 ask what you want to do with the trace. But for unexpected
13187 terminations (@value{GDBN} crash, network outage), it would be
13188 unfortunate to lose hard-won trace data, so the variable
13189 @code{disconnected-tracing} lets you decide whether the trace should
13190 continue running without @value{GDBN}.
13193 @item set disconnected-tracing on
13194 @itemx set disconnected-tracing off
13195 @kindex set disconnected-tracing
13196 Choose whether a tracing run should continue to run if @value{GDBN}
13197 has disconnected from the target. Note that @code{detach} or
13198 @code{quit} will ask you directly what to do about a running trace no
13199 matter what this variable's setting, so the variable is mainly useful
13200 for handling unexpected situations, such as loss of the network.
13202 @item show disconnected-tracing
13203 @kindex show disconnected-tracing
13204 Show the current choice for disconnected tracing.
13208 When you reconnect to the target, the trace experiment may or may not
13209 still be running; it might have filled the trace buffer in the
13210 meantime, or stopped for one of the other reasons. If it is running,
13211 it will continue after reconnection.
13213 Upon reconnection, the target will upload information about the
13214 tracepoints in effect. @value{GDBN} will then compare that
13215 information to the set of tracepoints currently defined, and attempt
13216 to match them up, allowing for the possibility that the numbers may
13217 have changed due to creation and deletion in the meantime. If one of
13218 the target's tracepoints does not match any in @value{GDBN}, the
13219 debugger will create a new tracepoint, so that you have a number with
13220 which to specify that tracepoint. This matching-up process is
13221 necessarily heuristic, and it may result in useless tracepoints being
13222 created; you may simply delete them if they are of no use.
13224 @cindex circular trace buffer
13225 If your target agent supports a @dfn{circular trace buffer}, then you
13226 can run a trace experiment indefinitely without filling the trace
13227 buffer; when space runs out, the agent deletes already-collected trace
13228 frames, oldest first, until there is enough room to continue
13229 collecting. This is especially useful if your tracepoints are being
13230 hit too often, and your trace gets terminated prematurely because the
13231 buffer is full. To ask for a circular trace buffer, simply set
13232 @samp{circular-trace-buffer} to on. You can set this at any time,
13233 including during tracing; if the agent can do it, it will change
13234 buffer handling on the fly, otherwise it will not take effect until
13238 @item set circular-trace-buffer on
13239 @itemx set circular-trace-buffer off
13240 @kindex set circular-trace-buffer
13241 Choose whether a tracing run should use a linear or circular buffer
13242 for trace data. A linear buffer will not lose any trace data, but may
13243 fill up prematurely, while a circular buffer will discard old trace
13244 data, but it will have always room for the latest tracepoint hits.
13246 @item show circular-trace-buffer
13247 @kindex show circular-trace-buffer
13248 Show the current choice for the trace buffer. Note that this may not
13249 match the agent's current buffer handling, nor is it guaranteed to
13250 match the setting that might have been in effect during a past run,
13251 for instance if you are looking at frames from a trace file.
13256 @item set trace-buffer-size @var{n}
13257 @itemx set trace-buffer-size unlimited
13258 @kindex set trace-buffer-size
13259 Request that the target use a trace buffer of @var{n} bytes. Not all
13260 targets will honor the request; they may have a compiled-in size for
13261 the trace buffer, or some other limitation. Set to a value of
13262 @code{unlimited} or @code{-1} to let the target use whatever size it
13263 likes. This is also the default.
13265 @item show trace-buffer-size
13266 @kindex show trace-buffer-size
13267 Show the current requested size for the trace buffer. Note that this
13268 will only match the actual size if the target supports size-setting,
13269 and was able to handle the requested size. For instance, if the
13270 target can only change buffer size between runs, this variable will
13271 not reflect the change until the next run starts. Use @code{tstatus}
13272 to get a report of the actual buffer size.
13276 @item set trace-user @var{text}
13277 @kindex set trace-user
13279 @item show trace-user
13280 @kindex show trace-user
13282 @item set trace-notes @var{text}
13283 @kindex set trace-notes
13284 Set the trace run's notes.
13286 @item show trace-notes
13287 @kindex show trace-notes
13288 Show the trace run's notes.
13290 @item set trace-stop-notes @var{text}
13291 @kindex set trace-stop-notes
13292 Set the trace run's stop notes. The handling of the note is as for
13293 @code{tstop} arguments; the set command is convenient way to fix a
13294 stop note that is mistaken or incomplete.
13296 @item show trace-stop-notes
13297 @kindex show trace-stop-notes
13298 Show the trace run's stop notes.
13302 @node Tracepoint Restrictions
13303 @subsection Tracepoint Restrictions
13305 @cindex tracepoint restrictions
13306 There are a number of restrictions on the use of tracepoints. As
13307 described above, tracepoint data gathering occurs on the target
13308 without interaction from @value{GDBN}. Thus the full capabilities of
13309 the debugger are not available during data gathering, and then at data
13310 examination time, you will be limited by only having what was
13311 collected. The following items describe some common problems, but it
13312 is not exhaustive, and you may run into additional difficulties not
13318 Tracepoint expressions are intended to gather objects (lvalues). Thus
13319 the full flexibility of GDB's expression evaluator is not available.
13320 You cannot call functions, cast objects to aggregate types, access
13321 convenience variables or modify values (except by assignment to trace
13322 state variables). Some language features may implicitly call
13323 functions (for instance Objective-C fields with accessors), and therefore
13324 cannot be collected either.
13327 Collection of local variables, either individually or in bulk with
13328 @code{$locals} or @code{$args}, during @code{while-stepping} may
13329 behave erratically. The stepping action may enter a new scope (for
13330 instance by stepping into a function), or the location of the variable
13331 may change (for instance it is loaded into a register). The
13332 tracepoint data recorded uses the location information for the
13333 variables that is correct for the tracepoint location. When the
13334 tracepoint is created, it is not possible, in general, to determine
13335 where the steps of a @code{while-stepping} sequence will advance the
13336 program---particularly if a conditional branch is stepped.
13339 Collection of an incompletely-initialized or partially-destroyed object
13340 may result in something that @value{GDBN} cannot display, or displays
13341 in a misleading way.
13344 When @value{GDBN} displays a pointer to character it automatically
13345 dereferences the pointer to also display characters of the string
13346 being pointed to. However, collecting the pointer during tracing does
13347 not automatically collect the string. You need to explicitly
13348 dereference the pointer and provide size information if you want to
13349 collect not only the pointer, but the memory pointed to. For example,
13350 @code{*ptr@@50} can be used to collect the 50 element array pointed to
13354 It is not possible to collect a complete stack backtrace at a
13355 tracepoint. Instead, you may collect the registers and a few hundred
13356 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
13357 (adjust to use the name of the actual stack pointer register on your
13358 target architecture, and the amount of stack you wish to capture).
13359 Then the @code{backtrace} command will show a partial backtrace when
13360 using a trace frame. The number of stack frames that can be examined
13361 depends on the sizes of the frames in the collected stack. Note that
13362 if you ask for a block so large that it goes past the bottom of the
13363 stack, the target agent may report an error trying to read from an
13367 If you do not collect registers at a tracepoint, @value{GDBN} can
13368 infer that the value of @code{$pc} must be the same as the address of
13369 the tracepoint and use that when you are looking at a trace frame
13370 for that tracepoint. However, this cannot work if the tracepoint has
13371 multiple locations (for instance if it was set in a function that was
13372 inlined), or if it has a @code{while-stepping} loop. In those cases
13373 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
13378 @node Analyze Collected Data
13379 @section Using the Collected Data
13381 After the tracepoint experiment ends, you use @value{GDBN} commands
13382 for examining the trace data. The basic idea is that each tracepoint
13383 collects a trace @dfn{snapshot} every time it is hit and another
13384 snapshot every time it single-steps. All these snapshots are
13385 consecutively numbered from zero and go into a buffer, and you can
13386 examine them later. The way you examine them is to @dfn{focus} on a
13387 specific trace snapshot. When the remote stub is focused on a trace
13388 snapshot, it will respond to all @value{GDBN} requests for memory and
13389 registers by reading from the buffer which belongs to that snapshot,
13390 rather than from @emph{real} memory or registers of the program being
13391 debugged. This means that @strong{all} @value{GDBN} commands
13392 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
13393 behave as if we were currently debugging the program state as it was
13394 when the tracepoint occurred. Any requests for data that are not in
13395 the buffer will fail.
13398 * tfind:: How to select a trace snapshot
13399 * tdump:: How to display all data for a snapshot
13400 * save tracepoints:: How to save tracepoints for a future run
13404 @subsection @code{tfind @var{n}}
13407 @cindex select trace snapshot
13408 @cindex find trace snapshot
13409 The basic command for selecting a trace snapshot from the buffer is
13410 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
13411 counting from zero. If no argument @var{n} is given, the next
13412 snapshot is selected.
13414 Here are the various forms of using the @code{tfind} command.
13418 Find the first snapshot in the buffer. This is a synonym for
13419 @code{tfind 0} (since 0 is the number of the first snapshot).
13422 Stop debugging trace snapshots, resume @emph{live} debugging.
13425 Same as @samp{tfind none}.
13428 No argument means find the next trace snapshot or find the first
13429 one if no trace snapshot is selected.
13432 Find the previous trace snapshot before the current one. This permits
13433 retracing earlier steps.
13435 @item tfind tracepoint @var{num}
13436 Find the next snapshot associated with tracepoint @var{num}. Search
13437 proceeds forward from the last examined trace snapshot. If no
13438 argument @var{num} is given, it means find the next snapshot collected
13439 for the same tracepoint as the current snapshot.
13441 @item tfind pc @var{addr}
13442 Find the next snapshot associated with the value @var{addr} of the
13443 program counter. Search proceeds forward from the last examined trace
13444 snapshot. If no argument @var{addr} is given, it means find the next
13445 snapshot with the same value of PC as the current snapshot.
13447 @item tfind outside @var{addr1}, @var{addr2}
13448 Find the next snapshot whose PC is outside the given range of
13449 addresses (exclusive).
13451 @item tfind range @var{addr1}, @var{addr2}
13452 Find the next snapshot whose PC is between @var{addr1} and
13453 @var{addr2} (inclusive).
13455 @item tfind line @r{[}@var{file}:@r{]}@var{n}
13456 Find the next snapshot associated with the source line @var{n}. If
13457 the optional argument @var{file} is given, refer to line @var{n} in
13458 that source file. Search proceeds forward from the last examined
13459 trace snapshot. If no argument @var{n} is given, it means find the
13460 next line other than the one currently being examined; thus saying
13461 @code{tfind line} repeatedly can appear to have the same effect as
13462 stepping from line to line in a @emph{live} debugging session.
13465 The default arguments for the @code{tfind} commands are specifically
13466 designed to make it easy to scan through the trace buffer. For
13467 instance, @code{tfind} with no argument selects the next trace
13468 snapshot, and @code{tfind -} with no argument selects the previous
13469 trace snapshot. So, by giving one @code{tfind} command, and then
13470 simply hitting @key{RET} repeatedly you can examine all the trace
13471 snapshots in order. Or, by saying @code{tfind -} and then hitting
13472 @key{RET} repeatedly you can examine the snapshots in reverse order.
13473 The @code{tfind line} command with no argument selects the snapshot
13474 for the next source line executed. The @code{tfind pc} command with
13475 no argument selects the next snapshot with the same program counter
13476 (PC) as the current frame. The @code{tfind tracepoint} command with
13477 no argument selects the next trace snapshot collected by the same
13478 tracepoint as the current one.
13480 In addition to letting you scan through the trace buffer manually,
13481 these commands make it easy to construct @value{GDBN} scripts that
13482 scan through the trace buffer and print out whatever collected data
13483 you are interested in. Thus, if we want to examine the PC, FP, and SP
13484 registers from each trace frame in the buffer, we can say this:
13487 (@value{GDBP}) @b{tfind start}
13488 (@value{GDBP}) @b{while ($trace_frame != -1)}
13489 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
13490 $trace_frame, $pc, $sp, $fp
13494 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
13495 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
13496 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
13497 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
13498 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
13499 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
13500 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
13501 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
13502 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
13503 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
13504 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
13507 Or, if we want to examine the variable @code{X} at each source line in
13511 (@value{GDBP}) @b{tfind start}
13512 (@value{GDBP}) @b{while ($trace_frame != -1)}
13513 > printf "Frame %d, X == %d\n", $trace_frame, X
13523 @subsection @code{tdump}
13525 @cindex dump all data collected at tracepoint
13526 @cindex tracepoint data, display
13528 This command takes no arguments. It prints all the data collected at
13529 the current trace snapshot.
13532 (@value{GDBP}) @b{trace 444}
13533 (@value{GDBP}) @b{actions}
13534 Enter actions for tracepoint #2, one per line:
13535 > collect $regs, $locals, $args, gdb_long_test
13538 (@value{GDBP}) @b{tstart}
13540 (@value{GDBP}) @b{tfind line 444}
13541 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
13543 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
13545 (@value{GDBP}) @b{tdump}
13546 Data collected at tracepoint 2, trace frame 1:
13547 d0 0xc4aa0085 -995491707
13551 d4 0x71aea3d 119204413
13554 d7 0x380035 3670069
13555 a0 0x19e24a 1696330
13556 a1 0x3000668 50333288
13558 a3 0x322000 3284992
13559 a4 0x3000698 50333336
13560 a5 0x1ad3cc 1758156
13561 fp 0x30bf3c 0x30bf3c
13562 sp 0x30bf34 0x30bf34
13564 pc 0x20b2c8 0x20b2c8
13568 p = 0x20e5b4 "gdb-test"
13575 gdb_long_test = 17 '\021'
13580 @code{tdump} works by scanning the tracepoint's current collection
13581 actions and printing the value of each expression listed. So
13582 @code{tdump} can fail, if after a run, you change the tracepoint's
13583 actions to mention variables that were not collected during the run.
13585 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
13586 uses the collected value of @code{$pc} to distinguish between trace
13587 frames that were collected at the tracepoint hit, and frames that were
13588 collected while stepping. This allows it to correctly choose whether
13589 to display the basic list of collections, or the collections from the
13590 body of the while-stepping loop. However, if @code{$pc} was not collected,
13591 then @code{tdump} will always attempt to dump using the basic collection
13592 list, and may fail if a while-stepping frame does not include all the
13593 same data that is collected at the tracepoint hit.
13594 @c This is getting pretty arcane, example would be good.
13596 @node save tracepoints
13597 @subsection @code{save tracepoints @var{filename}}
13598 @kindex save tracepoints
13599 @kindex save-tracepoints
13600 @cindex save tracepoints for future sessions
13602 This command saves all current tracepoint definitions together with
13603 their actions and passcounts, into a file @file{@var{filename}}
13604 suitable for use in a later debugging session. To read the saved
13605 tracepoint definitions, use the @code{source} command (@pxref{Command
13606 Files}). The @w{@code{save-tracepoints}} command is a deprecated
13607 alias for @w{@code{save tracepoints}}
13609 @node Tracepoint Variables
13610 @section Convenience Variables for Tracepoints
13611 @cindex tracepoint variables
13612 @cindex convenience variables for tracepoints
13615 @vindex $trace_frame
13616 @item (int) $trace_frame
13617 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
13618 snapshot is selected.
13620 @vindex $tracepoint
13621 @item (int) $tracepoint
13622 The tracepoint for the current trace snapshot.
13624 @vindex $trace_line
13625 @item (int) $trace_line
13626 The line number for the current trace snapshot.
13628 @vindex $trace_file
13629 @item (char []) $trace_file
13630 The source file for the current trace snapshot.
13632 @vindex $trace_func
13633 @item (char []) $trace_func
13634 The name of the function containing @code{$tracepoint}.
13637 Note: @code{$trace_file} is not suitable for use in @code{printf},
13638 use @code{output} instead.
13640 Here's a simple example of using these convenience variables for
13641 stepping through all the trace snapshots and printing some of their
13642 data. Note that these are not the same as trace state variables,
13643 which are managed by the target.
13646 (@value{GDBP}) @b{tfind start}
13648 (@value{GDBP}) @b{while $trace_frame != -1}
13649 > output $trace_file
13650 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
13656 @section Using Trace Files
13657 @cindex trace files
13659 In some situations, the target running a trace experiment may no
13660 longer be available; perhaps it crashed, or the hardware was needed
13661 for a different activity. To handle these cases, you can arrange to
13662 dump the trace data into a file, and later use that file as a source
13663 of trace data, via the @code{target tfile} command.
13668 @item tsave [ -r ] @var{filename}
13669 @itemx tsave [-ctf] @var{dirname}
13670 Save the trace data to @var{filename}. By default, this command
13671 assumes that @var{filename} refers to the host filesystem, so if
13672 necessary @value{GDBN} will copy raw trace data up from the target and
13673 then save it. If the target supports it, you can also supply the
13674 optional argument @code{-r} (``remote'') to direct the target to save
13675 the data directly into @var{filename} in its own filesystem, which may be
13676 more efficient if the trace buffer is very large. (Note, however, that
13677 @code{target tfile} can only read from files accessible to the host.)
13678 By default, this command will save trace frame in tfile format.
13679 You can supply the optional argument @code{-ctf} to save date in CTF
13680 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
13681 that can be shared by multiple debugging and tracing tools. Please go to
13682 @indicateurl{http://www.efficios.com/ctf} to get more information.
13684 @kindex target tfile
13688 @item target tfile @var{filename}
13689 @itemx target ctf @var{dirname}
13690 Use the file named @var{filename} or directory named @var{dirname} as
13691 a source of trace data. Commands that examine data work as they do with
13692 a live target, but it is not possible to run any new trace experiments.
13693 @code{tstatus} will report the state of the trace run at the moment
13694 the data was saved, as well as the current trace frame you are examining.
13695 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
13699 (@value{GDBP}) target ctf ctf.ctf
13700 (@value{GDBP}) tfind
13701 Found trace frame 0, tracepoint 2
13702 39 ++a; /* set tracepoint 1 here */
13703 (@value{GDBP}) tdump
13704 Data collected at tracepoint 2, trace frame 0:
13708 c = @{"123", "456", "789", "123", "456", "789"@}
13709 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
13717 @chapter Debugging Programs That Use Overlays
13720 If your program is too large to fit completely in your target system's
13721 memory, you can sometimes use @dfn{overlays} to work around this
13722 problem. @value{GDBN} provides some support for debugging programs that
13726 * How Overlays Work:: A general explanation of overlays.
13727 * Overlay Commands:: Managing overlays in @value{GDBN}.
13728 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
13729 mapped by asking the inferior.
13730 * Overlay Sample Program:: A sample program using overlays.
13733 @node How Overlays Work
13734 @section How Overlays Work
13735 @cindex mapped overlays
13736 @cindex unmapped overlays
13737 @cindex load address, overlay's
13738 @cindex mapped address
13739 @cindex overlay area
13741 Suppose you have a computer whose instruction address space is only 64
13742 kilobytes long, but which has much more memory which can be accessed by
13743 other means: special instructions, segment registers, or memory
13744 management hardware, for example. Suppose further that you want to
13745 adapt a program which is larger than 64 kilobytes to run on this system.
13747 One solution is to identify modules of your program which are relatively
13748 independent, and need not call each other directly; call these modules
13749 @dfn{overlays}. Separate the overlays from the main program, and place
13750 their machine code in the larger memory. Place your main program in
13751 instruction memory, but leave at least enough space there to hold the
13752 largest overlay as well.
13754 Now, to call a function located in an overlay, you must first copy that
13755 overlay's machine code from the large memory into the space set aside
13756 for it in the instruction memory, and then jump to its entry point
13759 @c NB: In the below the mapped area's size is greater or equal to the
13760 @c size of all overlays. This is intentional to remind the developer
13761 @c that overlays don't necessarily need to be the same size.
13765 Data Instruction Larger
13766 Address Space Address Space Address Space
13767 +-----------+ +-----------+ +-----------+
13769 +-----------+ +-----------+ +-----------+<-- overlay 1
13770 | program | | main | .----| overlay 1 | load address
13771 | variables | | program | | +-----------+
13772 | and heap | | | | | |
13773 +-----------+ | | | +-----------+<-- overlay 2
13774 | | +-----------+ | | | load address
13775 +-----------+ | | | .-| overlay 2 |
13777 mapped --->+-----------+ | | +-----------+
13778 address | | | | | |
13779 | overlay | <-' | | |
13780 | area | <---' +-----------+<-- overlay 3
13781 | | <---. | | load address
13782 +-----------+ `--| overlay 3 |
13789 @anchor{A code overlay}A code overlay
13793 The diagram (@pxref{A code overlay}) shows a system with separate data
13794 and instruction address spaces. To map an overlay, the program copies
13795 its code from the larger address space to the instruction address space.
13796 Since the overlays shown here all use the same mapped address, only one
13797 may be mapped at a time. For a system with a single address space for
13798 data and instructions, the diagram would be similar, except that the
13799 program variables and heap would share an address space with the main
13800 program and the overlay area.
13802 An overlay loaded into instruction memory and ready for use is called a
13803 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
13804 instruction memory. An overlay not present (or only partially present)
13805 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
13806 is its address in the larger memory. The mapped address is also called
13807 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
13808 called the @dfn{load memory address}, or @dfn{LMA}.
13810 Unfortunately, overlays are not a completely transparent way to adapt a
13811 program to limited instruction memory. They introduce a new set of
13812 global constraints you must keep in mind as you design your program:
13817 Before calling or returning to a function in an overlay, your program
13818 must make sure that overlay is actually mapped. Otherwise, the call or
13819 return will transfer control to the right address, but in the wrong
13820 overlay, and your program will probably crash.
13823 If the process of mapping an overlay is expensive on your system, you
13824 will need to choose your overlays carefully to minimize their effect on
13825 your program's performance.
13828 The executable file you load onto your system must contain each
13829 overlay's instructions, appearing at the overlay's load address, not its
13830 mapped address. However, each overlay's instructions must be relocated
13831 and its symbols defined as if the overlay were at its mapped address.
13832 You can use GNU linker scripts to specify different load and relocation
13833 addresses for pieces of your program; see @ref{Overlay Description,,,
13834 ld.info, Using ld: the GNU linker}.
13837 The procedure for loading executable files onto your system must be able
13838 to load their contents into the larger address space as well as the
13839 instruction and data spaces.
13843 The overlay system described above is rather simple, and could be
13844 improved in many ways:
13849 If your system has suitable bank switch registers or memory management
13850 hardware, you could use those facilities to make an overlay's load area
13851 contents simply appear at their mapped address in instruction space.
13852 This would probably be faster than copying the overlay to its mapped
13853 area in the usual way.
13856 If your overlays are small enough, you could set aside more than one
13857 overlay area, and have more than one overlay mapped at a time.
13860 You can use overlays to manage data, as well as instructions. In
13861 general, data overlays are even less transparent to your design than
13862 code overlays: whereas code overlays only require care when you call or
13863 return to functions, data overlays require care every time you access
13864 the data. Also, if you change the contents of a data overlay, you
13865 must copy its contents back out to its load address before you can copy a
13866 different data overlay into the same mapped area.
13871 @node Overlay Commands
13872 @section Overlay Commands
13874 To use @value{GDBN}'s overlay support, each overlay in your program must
13875 correspond to a separate section of the executable file. The section's
13876 virtual memory address and load memory address must be the overlay's
13877 mapped and load addresses. Identifying overlays with sections allows
13878 @value{GDBN} to determine the appropriate address of a function or
13879 variable, depending on whether the overlay is mapped or not.
13881 @value{GDBN}'s overlay commands all start with the word @code{overlay};
13882 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
13887 Disable @value{GDBN}'s overlay support. When overlay support is
13888 disabled, @value{GDBN} assumes that all functions and variables are
13889 always present at their mapped addresses. By default, @value{GDBN}'s
13890 overlay support is disabled.
13892 @item overlay manual
13893 @cindex manual overlay debugging
13894 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
13895 relies on you to tell it which overlays are mapped, and which are not,
13896 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
13897 commands described below.
13899 @item overlay map-overlay @var{overlay}
13900 @itemx overlay map @var{overlay}
13901 @cindex map an overlay
13902 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
13903 be the name of the object file section containing the overlay. When an
13904 overlay is mapped, @value{GDBN} assumes it can find the overlay's
13905 functions and variables at their mapped addresses. @value{GDBN} assumes
13906 that any other overlays whose mapped ranges overlap that of
13907 @var{overlay} are now unmapped.
13909 @item overlay unmap-overlay @var{overlay}
13910 @itemx overlay unmap @var{overlay}
13911 @cindex unmap an overlay
13912 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
13913 must be the name of the object file section containing the overlay.
13914 When an overlay is unmapped, @value{GDBN} assumes it can find the
13915 overlay's functions and variables at their load addresses.
13918 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
13919 consults a data structure the overlay manager maintains in the inferior
13920 to see which overlays are mapped. For details, see @ref{Automatic
13921 Overlay Debugging}.
13923 @item overlay load-target
13924 @itemx overlay load
13925 @cindex reloading the overlay table
13926 Re-read the overlay table from the inferior. Normally, @value{GDBN}
13927 re-reads the table @value{GDBN} automatically each time the inferior
13928 stops, so this command should only be necessary if you have changed the
13929 overlay mapping yourself using @value{GDBN}. This command is only
13930 useful when using automatic overlay debugging.
13932 @item overlay list-overlays
13933 @itemx overlay list
13934 @cindex listing mapped overlays
13935 Display a list of the overlays currently mapped, along with their mapped
13936 addresses, load addresses, and sizes.
13940 Normally, when @value{GDBN} prints a code address, it includes the name
13941 of the function the address falls in:
13944 (@value{GDBP}) print main
13945 $3 = @{int ()@} 0x11a0 <main>
13948 When overlay debugging is enabled, @value{GDBN} recognizes code in
13949 unmapped overlays, and prints the names of unmapped functions with
13950 asterisks around them. For example, if @code{foo} is a function in an
13951 unmapped overlay, @value{GDBN} prints it this way:
13954 (@value{GDBP}) overlay list
13955 No sections are mapped.
13956 (@value{GDBP}) print foo
13957 $5 = @{int (int)@} 0x100000 <*foo*>
13960 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
13964 (@value{GDBP}) overlay list
13965 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
13966 mapped at 0x1016 - 0x104a
13967 (@value{GDBP}) print foo
13968 $6 = @{int (int)@} 0x1016 <foo>
13971 When overlay debugging is enabled, @value{GDBN} can find the correct
13972 address for functions and variables in an overlay, whether or not the
13973 overlay is mapped. This allows most @value{GDBN} commands, like
13974 @code{break} and @code{disassemble}, to work normally, even on unmapped
13975 code. However, @value{GDBN}'s breakpoint support has some limitations:
13979 @cindex breakpoints in overlays
13980 @cindex overlays, setting breakpoints in
13981 You can set breakpoints in functions in unmapped overlays, as long as
13982 @value{GDBN} can write to the overlay at its load address.
13984 @value{GDBN} can not set hardware or simulator-based breakpoints in
13985 unmapped overlays. However, if you set a breakpoint at the end of your
13986 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
13987 you are using manual overlay management), @value{GDBN} will re-set its
13988 breakpoints properly.
13992 @node Automatic Overlay Debugging
13993 @section Automatic Overlay Debugging
13994 @cindex automatic overlay debugging
13996 @value{GDBN} can automatically track which overlays are mapped and which
13997 are not, given some simple co-operation from the overlay manager in the
13998 inferior. If you enable automatic overlay debugging with the
13999 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
14000 looks in the inferior's memory for certain variables describing the
14001 current state of the overlays.
14003 Here are the variables your overlay manager must define to support
14004 @value{GDBN}'s automatic overlay debugging:
14008 @item @code{_ovly_table}:
14009 This variable must be an array of the following structures:
14014 /* The overlay's mapped address. */
14017 /* The size of the overlay, in bytes. */
14018 unsigned long size;
14020 /* The overlay's load address. */
14023 /* Non-zero if the overlay is currently mapped;
14025 unsigned long mapped;
14029 @item @code{_novlys}:
14030 This variable must be a four-byte signed integer, holding the total
14031 number of elements in @code{_ovly_table}.
14035 To decide whether a particular overlay is mapped or not, @value{GDBN}
14036 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
14037 @code{lma} members equal the VMA and LMA of the overlay's section in the
14038 executable file. When @value{GDBN} finds a matching entry, it consults
14039 the entry's @code{mapped} member to determine whether the overlay is
14042 In addition, your overlay manager may define a function called
14043 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
14044 will silently set a breakpoint there. If the overlay manager then
14045 calls this function whenever it has changed the overlay table, this
14046 will enable @value{GDBN} to accurately keep track of which overlays
14047 are in program memory, and update any breakpoints that may be set
14048 in overlays. This will allow breakpoints to work even if the
14049 overlays are kept in ROM or other non-writable memory while they
14050 are not being executed.
14052 @node Overlay Sample Program
14053 @section Overlay Sample Program
14054 @cindex overlay example program
14056 When linking a program which uses overlays, you must place the overlays
14057 at their load addresses, while relocating them to run at their mapped
14058 addresses. To do this, you must write a linker script (@pxref{Overlay
14059 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
14060 since linker scripts are specific to a particular host system, target
14061 architecture, and target memory layout, this manual cannot provide
14062 portable sample code demonstrating @value{GDBN}'s overlay support.
14064 However, the @value{GDBN} source distribution does contain an overlaid
14065 program, with linker scripts for a few systems, as part of its test
14066 suite. The program consists of the following files from
14067 @file{gdb/testsuite/gdb.base}:
14071 The main program file.
14073 A simple overlay manager, used by @file{overlays.c}.
14078 Overlay modules, loaded and used by @file{overlays.c}.
14081 Linker scripts for linking the test program on the @code{d10v-elf}
14082 and @code{m32r-elf} targets.
14085 You can build the test program using the @code{d10v-elf} GCC
14086 cross-compiler like this:
14089 $ d10v-elf-gcc -g -c overlays.c
14090 $ d10v-elf-gcc -g -c ovlymgr.c
14091 $ d10v-elf-gcc -g -c foo.c
14092 $ d10v-elf-gcc -g -c bar.c
14093 $ d10v-elf-gcc -g -c baz.c
14094 $ d10v-elf-gcc -g -c grbx.c
14095 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
14096 baz.o grbx.o -Wl,-Td10v.ld -o overlays
14099 The build process is identical for any other architecture, except that
14100 you must substitute the appropriate compiler and linker script for the
14101 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
14105 @chapter Using @value{GDBN} with Different Languages
14108 Although programming languages generally have common aspects, they are
14109 rarely expressed in the same manner. For instance, in ANSI C,
14110 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
14111 Modula-2, it is accomplished by @code{p^}. Values can also be
14112 represented (and displayed) differently. Hex numbers in C appear as
14113 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
14115 @cindex working language
14116 Language-specific information is built into @value{GDBN} for some languages,
14117 allowing you to express operations like the above in your program's
14118 native language, and allowing @value{GDBN} to output values in a manner
14119 consistent with the syntax of your program's native language. The
14120 language you use to build expressions is called the @dfn{working
14124 * Setting:: Switching between source languages
14125 * Show:: Displaying the language
14126 * Checks:: Type and range checks
14127 * Supported Languages:: Supported languages
14128 * Unsupported Languages:: Unsupported languages
14132 @section Switching Between Source Languages
14134 There are two ways to control the working language---either have @value{GDBN}
14135 set it automatically, or select it manually yourself. You can use the
14136 @code{set language} command for either purpose. On startup, @value{GDBN}
14137 defaults to setting the language automatically. The working language is
14138 used to determine how expressions you type are interpreted, how values
14141 In addition to the working language, every source file that
14142 @value{GDBN} knows about has its own working language. For some object
14143 file formats, the compiler might indicate which language a particular
14144 source file is in. However, most of the time @value{GDBN} infers the
14145 language from the name of the file. The language of a source file
14146 controls whether C@t{++} names are demangled---this way @code{backtrace} can
14147 show each frame appropriately for its own language. There is no way to
14148 set the language of a source file from within @value{GDBN}, but you can
14149 set the language associated with a filename extension. @xref{Show, ,
14150 Displaying the Language}.
14152 This is most commonly a problem when you use a program, such
14153 as @code{cfront} or @code{f2c}, that generates C but is written in
14154 another language. In that case, make the
14155 program use @code{#line} directives in its C output; that way
14156 @value{GDBN} will know the correct language of the source code of the original
14157 program, and will display that source code, not the generated C code.
14160 * Filenames:: Filename extensions and languages.
14161 * Manually:: Setting the working language manually
14162 * Automatically:: Having @value{GDBN} infer the source language
14166 @subsection List of Filename Extensions and Languages
14168 If a source file name ends in one of the following extensions, then
14169 @value{GDBN} infers that its language is the one indicated.
14187 C@t{++} source file
14193 Objective-C source file
14197 Fortran source file
14200 Modula-2 source file
14204 Assembler source file. This actually behaves almost like C, but
14205 @value{GDBN} does not skip over function prologues when stepping.
14208 In addition, you may set the language associated with a filename
14209 extension. @xref{Show, , Displaying the Language}.
14212 @subsection Setting the Working Language
14214 If you allow @value{GDBN} to set the language automatically,
14215 expressions are interpreted the same way in your debugging session and
14218 @kindex set language
14219 If you wish, you may set the language manually. To do this, issue the
14220 command @samp{set language @var{lang}}, where @var{lang} is the name of
14221 a language, such as
14222 @code{c} or @code{modula-2}.
14223 For a list of the supported languages, type @samp{set language}.
14225 Setting the language manually prevents @value{GDBN} from updating the working
14226 language automatically. This can lead to confusion if you try
14227 to debug a program when the working language is not the same as the
14228 source language, when an expression is acceptable to both
14229 languages---but means different things. For instance, if the current
14230 source file were written in C, and @value{GDBN} was parsing Modula-2, a
14238 might not have the effect you intended. In C, this means to add
14239 @code{b} and @code{c} and place the result in @code{a}. The result
14240 printed would be the value of @code{a}. In Modula-2, this means to compare
14241 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
14243 @node Automatically
14244 @subsection Having @value{GDBN} Infer the Source Language
14246 To have @value{GDBN} set the working language automatically, use
14247 @samp{set language local} or @samp{set language auto}. @value{GDBN}
14248 then infers the working language. That is, when your program stops in a
14249 frame (usually by encountering a breakpoint), @value{GDBN} sets the
14250 working language to the language recorded for the function in that
14251 frame. If the language for a frame is unknown (that is, if the function
14252 or block corresponding to the frame was defined in a source file that
14253 does not have a recognized extension), the current working language is
14254 not changed, and @value{GDBN} issues a warning.
14256 This may not seem necessary for most programs, which are written
14257 entirely in one source language. However, program modules and libraries
14258 written in one source language can be used by a main program written in
14259 a different source language. Using @samp{set language auto} in this
14260 case frees you from having to set the working language manually.
14263 @section Displaying the Language
14265 The following commands help you find out which language is the
14266 working language, and also what language source files were written in.
14269 @item show language
14270 @anchor{show language}
14271 @kindex show language
14272 Display the current working language. This is the
14273 language you can use with commands such as @code{print} to
14274 build and compute expressions that may involve variables in your program.
14277 @kindex info frame@r{, show the source language}
14278 Display the source language for this frame. This language becomes the
14279 working language if you use an identifier from this frame.
14280 @xref{Frame Info, ,Information about a Frame}, to identify the other
14281 information listed here.
14284 @kindex info source@r{, show the source language}
14285 Display the source language of this source file.
14286 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
14287 information listed here.
14290 In unusual circumstances, you may have source files with extensions
14291 not in the standard list. You can then set the extension associated
14292 with a language explicitly:
14295 @item set extension-language @var{ext} @var{language}
14296 @kindex set extension-language
14297 Tell @value{GDBN} that source files with extension @var{ext} are to be
14298 assumed as written in the source language @var{language}.
14300 @item info extensions
14301 @kindex info extensions
14302 List all the filename extensions and the associated languages.
14306 @section Type and Range Checking
14308 Some languages are designed to guard you against making seemingly common
14309 errors through a series of compile- and run-time checks. These include
14310 checking the type of arguments to functions and operators and making
14311 sure mathematical overflows are caught at run time. Checks such as
14312 these help to ensure a program's correctness once it has been compiled
14313 by eliminating type mismatches and providing active checks for range
14314 errors when your program is running.
14316 By default @value{GDBN} checks for these errors according to the
14317 rules of the current source language. Although @value{GDBN} does not check
14318 the statements in your program, it can check expressions entered directly
14319 into @value{GDBN} for evaluation via the @code{print} command, for example.
14322 * Type Checking:: An overview of type checking
14323 * Range Checking:: An overview of range checking
14326 @cindex type checking
14327 @cindex checks, type
14328 @node Type Checking
14329 @subsection An Overview of Type Checking
14331 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
14332 arguments to operators and functions have to be of the correct type,
14333 otherwise an error occurs. These checks prevent type mismatch
14334 errors from ever causing any run-time problems. For example,
14337 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
14339 (@value{GDBP}) print obj.my_method (0)
14342 (@value{GDBP}) print obj.my_method (0x1234)
14343 Cannot resolve method klass::my_method to any overloaded instance
14346 The second example fails because in C@t{++} the integer constant
14347 @samp{0x1234} is not type-compatible with the pointer parameter type.
14349 For the expressions you use in @value{GDBN} commands, you can tell
14350 @value{GDBN} to not enforce strict type checking or
14351 to treat any mismatches as errors and abandon the expression;
14352 When type checking is disabled, @value{GDBN} successfully evaluates
14353 expressions like the second example above.
14355 Even if type checking is off, there may be other reasons
14356 related to type that prevent @value{GDBN} from evaluating an expression.
14357 For instance, @value{GDBN} does not know how to add an @code{int} and
14358 a @code{struct foo}. These particular type errors have nothing to do
14359 with the language in use and usually arise from expressions which make
14360 little sense to evaluate anyway.
14362 @value{GDBN} provides some additional commands for controlling type checking:
14364 @kindex set check type
14365 @kindex show check type
14367 @item set check type on
14368 @itemx set check type off
14369 Set strict type checking on or off. If any type mismatches occur in
14370 evaluating an expression while type checking is on, @value{GDBN} prints a
14371 message and aborts evaluation of the expression.
14373 @item show check type
14374 Show the current setting of type checking and whether @value{GDBN}
14375 is enforcing strict type checking rules.
14378 @cindex range checking
14379 @cindex checks, range
14380 @node Range Checking
14381 @subsection An Overview of Range Checking
14383 In some languages (such as Modula-2), it is an error to exceed the
14384 bounds of a type; this is enforced with run-time checks. Such range
14385 checking is meant to ensure program correctness by making sure
14386 computations do not overflow, or indices on an array element access do
14387 not exceed the bounds of the array.
14389 For expressions you use in @value{GDBN} commands, you can tell
14390 @value{GDBN} to treat range errors in one of three ways: ignore them,
14391 always treat them as errors and abandon the expression, or issue
14392 warnings but evaluate the expression anyway.
14394 A range error can result from numerical overflow, from exceeding an
14395 array index bound, or when you type a constant that is not a member
14396 of any type. Some languages, however, do not treat overflows as an
14397 error. In many implementations of C, mathematical overflow causes the
14398 result to ``wrap around'' to lower values---for example, if @var{m} is
14399 the largest integer value, and @var{s} is the smallest, then
14402 @var{m} + 1 @result{} @var{s}
14405 This, too, is specific to individual languages, and in some cases
14406 specific to individual compilers or machines. @xref{Supported Languages, ,
14407 Supported Languages}, for further details on specific languages.
14409 @value{GDBN} provides some additional commands for controlling the range checker:
14411 @kindex set check range
14412 @kindex show check range
14414 @item set check range auto
14415 Set range checking on or off based on the current working language.
14416 @xref{Supported Languages, ,Supported Languages}, for the default settings for
14419 @item set check range on
14420 @itemx set check range off
14421 Set range checking on or off, overriding the default setting for the
14422 current working language. A warning is issued if the setting does not
14423 match the language default. If a range error occurs and range checking is on,
14424 then a message is printed and evaluation of the expression is aborted.
14426 @item set check range warn
14427 Output messages when the @value{GDBN} range checker detects a range error,
14428 but attempt to evaluate the expression anyway. Evaluating the
14429 expression may still be impossible for other reasons, such as accessing
14430 memory that the process does not own (a typical example from many Unix
14434 Show the current setting of the range checker, and whether or not it is
14435 being set automatically by @value{GDBN}.
14438 @node Supported Languages
14439 @section Supported Languages
14441 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
14442 OpenCL C, Pascal, Rust, assembly, Modula-2, and Ada.
14443 @c This is false ...
14444 Some @value{GDBN} features may be used in expressions regardless of the
14445 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
14446 and the @samp{@{type@}addr} construct (@pxref{Expressions,
14447 ,Expressions}) can be used with the constructs of any supported
14450 The following sections detail to what degree each source language is
14451 supported by @value{GDBN}. These sections are not meant to be language
14452 tutorials or references, but serve only as a reference guide to what the
14453 @value{GDBN} expression parser accepts, and what input and output
14454 formats should look like for different languages. There are many good
14455 books written on each of these languages; please look to these for a
14456 language reference or tutorial.
14459 * C:: C and C@t{++}
14462 * Objective-C:: Objective-C
14463 * OpenCL C:: OpenCL C
14464 * Fortran:: Fortran
14467 * Modula-2:: Modula-2
14472 @subsection C and C@t{++}
14474 @cindex C and C@t{++}
14475 @cindex expressions in C or C@t{++}
14477 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
14478 to both languages. Whenever this is the case, we discuss those languages
14482 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
14483 @cindex @sc{gnu} C@t{++}
14484 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
14485 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
14486 effectively, you must compile your C@t{++} programs with a supported
14487 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
14488 compiler (@code{aCC}).
14491 * C Operators:: C and C@t{++} operators
14492 * C Constants:: C and C@t{++} constants
14493 * C Plus Plus Expressions:: C@t{++} expressions
14494 * C Defaults:: Default settings for C and C@t{++}
14495 * C Checks:: C and C@t{++} type and range checks
14496 * Debugging C:: @value{GDBN} and C
14497 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
14498 * Decimal Floating Point:: Numbers in Decimal Floating Point format
14502 @subsubsection C and C@t{++} Operators
14504 @cindex C and C@t{++} operators
14506 Operators must be defined on values of specific types. For instance,
14507 @code{+} is defined on numbers, but not on structures. Operators are
14508 often defined on groups of types.
14510 For the purposes of C and C@t{++}, the following definitions hold:
14515 @emph{Integral types} include @code{int} with any of its storage-class
14516 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
14519 @emph{Floating-point types} include @code{float}, @code{double}, and
14520 @code{long double} (if supported by the target platform).
14523 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
14526 @emph{Scalar types} include all of the above.
14531 The following operators are supported. They are listed here
14532 in order of increasing precedence:
14536 The comma or sequencing operator. Expressions in a comma-separated list
14537 are evaluated from left to right, with the result of the entire
14538 expression being the last expression evaluated.
14541 Assignment. The value of an assignment expression is the value
14542 assigned. Defined on scalar types.
14545 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
14546 and translated to @w{@code{@var{a} = @var{a op b}}}.
14547 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
14548 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
14549 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
14552 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
14553 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
14554 should be of an integral type.
14557 Logical @sc{or}. Defined on integral types.
14560 Logical @sc{and}. Defined on integral types.
14563 Bitwise @sc{or}. Defined on integral types.
14566 Bitwise exclusive-@sc{or}. Defined on integral types.
14569 Bitwise @sc{and}. Defined on integral types.
14572 Equality and inequality. Defined on scalar types. The value of these
14573 expressions is 0 for false and non-zero for true.
14575 @item <@r{, }>@r{, }<=@r{, }>=
14576 Less than, greater than, less than or equal, greater than or equal.
14577 Defined on scalar types. The value of these expressions is 0 for false
14578 and non-zero for true.
14581 left shift, and right shift. Defined on integral types.
14584 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14587 Addition and subtraction. Defined on integral types, floating-point types and
14590 @item *@r{, }/@r{, }%
14591 Multiplication, division, and modulus. Multiplication and division are
14592 defined on integral and floating-point types. Modulus is defined on
14596 Increment and decrement. When appearing before a variable, the
14597 operation is performed before the variable is used in an expression;
14598 when appearing after it, the variable's value is used before the
14599 operation takes place.
14602 Pointer dereferencing. Defined on pointer types. Same precedence as
14606 Address operator. Defined on variables. Same precedence as @code{++}.
14608 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
14609 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
14610 to examine the address
14611 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
14615 Negative. Defined on integral and floating-point types. Same
14616 precedence as @code{++}.
14619 Logical negation. Defined on integral types. Same precedence as
14623 Bitwise complement operator. Defined on integral types. Same precedence as
14628 Structure member, and pointer-to-structure member. For convenience,
14629 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
14630 pointer based on the stored type information.
14631 Defined on @code{struct} and @code{union} data.
14634 Dereferences of pointers to members.
14637 Array indexing. @code{@var{a}[@var{i}]} is defined as
14638 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
14641 Function parameter list. Same precedence as @code{->}.
14644 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
14645 and @code{class} types.
14648 Doubled colons also represent the @value{GDBN} scope operator
14649 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
14653 If an operator is redefined in the user code, @value{GDBN} usually
14654 attempts to invoke the redefined version instead of using the operator's
14655 predefined meaning.
14658 @subsubsection C and C@t{++} Constants
14660 @cindex C and C@t{++} constants
14662 @value{GDBN} allows you to express the constants of C and C@t{++} in the
14667 Integer constants are a sequence of digits. Octal constants are
14668 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
14669 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
14670 @samp{l}, specifying that the constant should be treated as a
14674 Floating point constants are a sequence of digits, followed by a decimal
14675 point, followed by a sequence of digits, and optionally followed by an
14676 exponent. An exponent is of the form:
14677 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
14678 sequence of digits. The @samp{+} is optional for positive exponents.
14679 A floating-point constant may also end with a letter @samp{f} or
14680 @samp{F}, specifying that the constant should be treated as being of
14681 the @code{float} (as opposed to the default @code{double}) type; or with
14682 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
14686 Enumerated constants consist of enumerated identifiers, or their
14687 integral equivalents.
14690 Character constants are a single character surrounded by single quotes
14691 (@code{'}), or a number---the ordinal value of the corresponding character
14692 (usually its @sc{ascii} value). Within quotes, the single character may
14693 be represented by a letter or by @dfn{escape sequences}, which are of
14694 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
14695 of the character's ordinal value; or of the form @samp{\@var{x}}, where
14696 @samp{@var{x}} is a predefined special character---for example,
14697 @samp{\n} for newline.
14699 Wide character constants can be written by prefixing a character
14700 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
14701 form of @samp{x}. The target wide character set is used when
14702 computing the value of this constant (@pxref{Character Sets}).
14705 String constants are a sequence of character constants surrounded by
14706 double quotes (@code{"}). Any valid character constant (as described
14707 above) may appear. Double quotes within the string must be preceded by
14708 a backslash, so for instance @samp{"a\"b'c"} is a string of five
14711 Wide string constants can be written by prefixing a string constant
14712 with @samp{L}, as in C. The target wide character set is used when
14713 computing the value of this constant (@pxref{Character Sets}).
14716 Pointer constants are an integral value. You can also write pointers
14717 to constants using the C operator @samp{&}.
14720 Array constants are comma-separated lists surrounded by braces @samp{@{}
14721 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
14722 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
14723 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
14726 @node C Plus Plus Expressions
14727 @subsubsection C@t{++} Expressions
14729 @cindex expressions in C@t{++}
14730 @value{GDBN} expression handling can interpret most C@t{++} expressions.
14732 @cindex debugging C@t{++} programs
14733 @cindex C@t{++} compilers
14734 @cindex debug formats and C@t{++}
14735 @cindex @value{NGCC} and C@t{++}
14737 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
14738 the proper compiler and the proper debug format. Currently,
14739 @value{GDBN} works best when debugging C@t{++} code that is compiled
14740 with the most recent version of @value{NGCC} possible. The DWARF
14741 debugging format is preferred; @value{NGCC} defaults to this on most
14742 popular platforms. Other compilers and/or debug formats are likely to
14743 work badly or not at all when using @value{GDBN} to debug C@t{++}
14744 code. @xref{Compilation}.
14749 @cindex member functions
14751 Member function calls are allowed; you can use expressions like
14754 count = aml->GetOriginal(x, y)
14757 @vindex this@r{, inside C@t{++} member functions}
14758 @cindex namespace in C@t{++}
14760 While a member function is active (in the selected stack frame), your
14761 expressions have the same namespace available as the member function;
14762 that is, @value{GDBN} allows implicit references to the class instance
14763 pointer @code{this} following the same rules as C@t{++}. @code{using}
14764 declarations in the current scope are also respected by @value{GDBN}.
14766 @cindex call overloaded functions
14767 @cindex overloaded functions, calling
14768 @cindex type conversions in C@t{++}
14770 You can call overloaded functions; @value{GDBN} resolves the function
14771 call to the right definition, with some restrictions. @value{GDBN} does not
14772 perform overload resolution involving user-defined type conversions,
14773 calls to constructors, or instantiations of templates that do not exist
14774 in the program. It also cannot handle ellipsis argument lists or
14777 It does perform integral conversions and promotions, floating-point
14778 promotions, arithmetic conversions, pointer conversions, conversions of
14779 class objects to base classes, and standard conversions such as those of
14780 functions or arrays to pointers; it requires an exact match on the
14781 number of function arguments.
14783 Overload resolution is always performed, unless you have specified
14784 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
14785 ,@value{GDBN} Features for C@t{++}}.
14787 You must specify @code{set overload-resolution off} in order to use an
14788 explicit function signature to call an overloaded function, as in
14790 p 'foo(char,int)'('x', 13)
14793 The @value{GDBN} command-completion facility can simplify this;
14794 see @ref{Completion, ,Command Completion}.
14796 @cindex reference declarations
14798 @value{GDBN} understands variables declared as C@t{++} references; you can use
14799 them in expressions just as you do in C@t{++} source---they are automatically
14802 In the parameter list shown when @value{GDBN} displays a frame, the values of
14803 reference variables are not displayed (unlike other variables); this
14804 avoids clutter, since references are often used for large structures.
14805 The @emph{address} of a reference variable is always shown, unless
14806 you have specified @samp{set print address off}.
14809 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
14810 expressions can use it just as expressions in your program do. Since
14811 one scope may be defined in another, you can use @code{::} repeatedly if
14812 necessary, for example in an expression like
14813 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
14814 resolving name scope by reference to source files, in both C and C@t{++}
14815 debugging (@pxref{Variables, ,Program Variables}).
14818 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
14823 @subsubsection C and C@t{++} Defaults
14825 @cindex C and C@t{++} defaults
14827 If you allow @value{GDBN} to set range checking automatically, it
14828 defaults to @code{off} whenever the working language changes to
14829 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
14830 selects the working language.
14832 If you allow @value{GDBN} to set the language automatically, it
14833 recognizes source files whose names end with @file{.c}, @file{.C}, or
14834 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
14835 these files, it sets the working language to C or C@t{++}.
14836 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
14837 for further details.
14840 @subsubsection C and C@t{++} Type and Range Checks
14842 @cindex C and C@t{++} checks
14844 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
14845 checking is used. However, if you turn type checking off, @value{GDBN}
14846 will allow certain non-standard conversions, such as promoting integer
14847 constants to pointers.
14849 Range checking, if turned on, is done on mathematical operations. Array
14850 indices are not checked, since they are often used to index a pointer
14851 that is not itself an array.
14854 @subsubsection @value{GDBN} and C
14856 The @code{set print union} and @code{show print union} commands apply to
14857 the @code{union} type. When set to @samp{on}, any @code{union} that is
14858 inside a @code{struct} or @code{class} is also printed. Otherwise, it
14859 appears as @samp{@{...@}}.
14861 The @code{@@} operator aids in the debugging of dynamic arrays, formed
14862 with pointers and a memory allocation function. @xref{Expressions,
14865 @node Debugging C Plus Plus
14866 @subsubsection @value{GDBN} Features for C@t{++}
14868 @cindex commands for C@t{++}
14870 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
14871 designed specifically for use with C@t{++}. Here is a summary:
14874 @cindex break in overloaded functions
14875 @item @r{breakpoint menus}
14876 When you want a breakpoint in a function whose name is overloaded,
14877 @value{GDBN} has the capability to display a menu of possible breakpoint
14878 locations to help you specify which function definition you want.
14879 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
14881 @cindex overloading in C@t{++}
14882 @item rbreak @var{regex}
14883 Setting breakpoints using regular expressions is helpful for setting
14884 breakpoints on overloaded functions that are not members of any special
14886 @xref{Set Breaks, ,Setting Breakpoints}.
14888 @cindex C@t{++} exception handling
14890 @itemx catch rethrow
14892 Debug C@t{++} exception handling using these commands. @xref{Set
14893 Catchpoints, , Setting Catchpoints}.
14895 @cindex inheritance
14896 @item ptype @var{typename}
14897 Print inheritance relationships as well as other information for type
14899 @xref{Symbols, ,Examining the Symbol Table}.
14901 @item info vtbl @var{expression}.
14902 The @code{info vtbl} command can be used to display the virtual
14903 method tables of the object computed by @var{expression}. This shows
14904 one entry per virtual table; there may be multiple virtual tables when
14905 multiple inheritance is in use.
14907 @cindex C@t{++} demangling
14908 @item demangle @var{name}
14909 Demangle @var{name}.
14910 @xref{Symbols}, for a more complete description of the @code{demangle} command.
14912 @cindex C@t{++} symbol display
14913 @item set print demangle
14914 @itemx show print demangle
14915 @itemx set print asm-demangle
14916 @itemx show print asm-demangle
14917 Control whether C@t{++} symbols display in their source form, both when
14918 displaying code as C@t{++} source and when displaying disassemblies.
14919 @xref{Print Settings, ,Print Settings}.
14921 @item set print object
14922 @itemx show print object
14923 Choose whether to print derived (actual) or declared types of objects.
14924 @xref{Print Settings, ,Print Settings}.
14926 @item set print vtbl
14927 @itemx show print vtbl
14928 Control the format for printing virtual function tables.
14929 @xref{Print Settings, ,Print Settings}.
14930 (The @code{vtbl} commands do not work on programs compiled with the HP
14931 ANSI C@t{++} compiler (@code{aCC}).)
14933 @kindex set overload-resolution
14934 @cindex overloaded functions, overload resolution
14935 @item set overload-resolution on
14936 Enable overload resolution for C@t{++} expression evaluation. The default
14937 is on. For overloaded functions, @value{GDBN} evaluates the arguments
14938 and searches for a function whose signature matches the argument types,
14939 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
14940 Expressions, ,C@t{++} Expressions}, for details).
14941 If it cannot find a match, it emits a message.
14943 @item set overload-resolution off
14944 Disable overload resolution for C@t{++} expression evaluation. For
14945 overloaded functions that are not class member functions, @value{GDBN}
14946 chooses the first function of the specified name that it finds in the
14947 symbol table, whether or not its arguments are of the correct type. For
14948 overloaded functions that are class member functions, @value{GDBN}
14949 searches for a function whose signature @emph{exactly} matches the
14952 @kindex show overload-resolution
14953 @item show overload-resolution
14954 Show the current setting of overload resolution.
14956 @item @r{Overloaded symbol names}
14957 You can specify a particular definition of an overloaded symbol, using
14958 the same notation that is used to declare such symbols in C@t{++}: type
14959 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
14960 also use the @value{GDBN} command-line word completion facilities to list the
14961 available choices, or to finish the type list for you.
14962 @xref{Completion,, Command Completion}, for details on how to do this.
14965 @node Decimal Floating Point
14966 @subsubsection Decimal Floating Point format
14967 @cindex decimal floating point format
14969 @value{GDBN} can examine, set and perform computations with numbers in
14970 decimal floating point format, which in the C language correspond to the
14971 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
14972 specified by the extension to support decimal floating-point arithmetic.
14974 There are two encodings in use, depending on the architecture: BID (Binary
14975 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
14976 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
14979 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
14980 to manipulate decimal floating point numbers, it is not possible to convert
14981 (using a cast, for example) integers wider than 32-bit to decimal float.
14983 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
14984 point computations, error checking in decimal float operations ignores
14985 underflow, overflow and divide by zero exceptions.
14987 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
14988 to inspect @code{_Decimal128} values stored in floating point registers.
14989 See @ref{PowerPC,,PowerPC} for more details.
14995 @value{GDBN} can be used to debug programs written in D and compiled with
14996 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
14997 specific feature --- dynamic arrays.
15002 @cindex Go (programming language)
15003 @value{GDBN} can be used to debug programs written in Go and compiled with
15004 @file{gccgo} or @file{6g} compilers.
15006 Here is a summary of the Go-specific features and restrictions:
15009 @cindex current Go package
15010 @item The current Go package
15011 The name of the current package does not need to be specified when
15012 specifying global variables and functions.
15014 For example, given the program:
15018 var myglob = "Shall we?"
15024 When stopped inside @code{main} either of these work:
15028 (gdb) p main.myglob
15031 @cindex builtin Go types
15032 @item Builtin Go types
15033 The @code{string} type is recognized by @value{GDBN} and is printed
15036 @cindex builtin Go functions
15037 @item Builtin Go functions
15038 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
15039 function and handles it internally.
15041 @cindex restrictions on Go expressions
15042 @item Restrictions on Go expressions
15043 All Go operators are supported except @code{&^}.
15044 The Go @code{_} ``blank identifier'' is not supported.
15045 Automatic dereferencing of pointers is not supported.
15049 @subsection Objective-C
15051 @cindex Objective-C
15052 This section provides information about some commands and command
15053 options that are useful for debugging Objective-C code. See also
15054 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
15055 few more commands specific to Objective-C support.
15058 * Method Names in Commands::
15059 * The Print Command with Objective-C::
15062 @node Method Names in Commands
15063 @subsubsection Method Names in Commands
15065 The following commands have been extended to accept Objective-C method
15066 names as line specifications:
15068 @kindex clear@r{, and Objective-C}
15069 @kindex break@r{, and Objective-C}
15070 @kindex info line@r{, and Objective-C}
15071 @kindex jump@r{, and Objective-C}
15072 @kindex list@r{, and Objective-C}
15076 @item @code{info line}
15081 A fully qualified Objective-C method name is specified as
15084 -[@var{Class} @var{methodName}]
15087 where the minus sign is used to indicate an instance method and a
15088 plus sign (not shown) is used to indicate a class method. The class
15089 name @var{Class} and method name @var{methodName} are enclosed in
15090 brackets, similar to the way messages are specified in Objective-C
15091 source code. For example, to set a breakpoint at the @code{create}
15092 instance method of class @code{Fruit} in the program currently being
15096 break -[Fruit create]
15099 To list ten program lines around the @code{initialize} class method,
15103 list +[NSText initialize]
15106 In the current version of @value{GDBN}, the plus or minus sign is
15107 required. In future versions of @value{GDBN}, the plus or minus
15108 sign will be optional, but you can use it to narrow the search. It
15109 is also possible to specify just a method name:
15115 You must specify the complete method name, including any colons. If
15116 your program's source files contain more than one @code{create} method,
15117 you'll be presented with a numbered list of classes that implement that
15118 method. Indicate your choice by number, or type @samp{0} to exit if
15121 As another example, to clear a breakpoint established at the
15122 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
15125 clear -[NSWindow makeKeyAndOrderFront:]
15128 @node The Print Command with Objective-C
15129 @subsubsection The Print Command With Objective-C
15130 @cindex Objective-C, print objects
15131 @kindex print-object
15132 @kindex po @r{(@code{print-object})}
15134 The print command has also been extended to accept methods. For example:
15137 print -[@var{object} hash]
15140 @cindex print an Objective-C object description
15141 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
15143 will tell @value{GDBN} to send the @code{hash} message to @var{object}
15144 and print the result. Also, an additional command has been added,
15145 @code{print-object} or @code{po} for short, which is meant to print
15146 the description of an object. However, this command may only work
15147 with certain Objective-C libraries that have a particular hook
15148 function, @code{_NSPrintForDebugger}, defined.
15151 @subsection OpenCL C
15154 This section provides information about @value{GDBN}s OpenCL C support.
15157 * OpenCL C Datatypes::
15158 * OpenCL C Expressions::
15159 * OpenCL C Operators::
15162 @node OpenCL C Datatypes
15163 @subsubsection OpenCL C Datatypes
15165 @cindex OpenCL C Datatypes
15166 @value{GDBN} supports the builtin scalar and vector datatypes specified
15167 by OpenCL 1.1. In addition the half- and double-precision floating point
15168 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
15169 extensions are also known to @value{GDBN}.
15171 @node OpenCL C Expressions
15172 @subsubsection OpenCL C Expressions
15174 @cindex OpenCL C Expressions
15175 @value{GDBN} supports accesses to vector components including the access as
15176 lvalue where possible. Since OpenCL C is based on C99 most C expressions
15177 supported by @value{GDBN} can be used as well.
15179 @node OpenCL C Operators
15180 @subsubsection OpenCL C Operators
15182 @cindex OpenCL C Operators
15183 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
15187 @subsection Fortran
15188 @cindex Fortran-specific support in @value{GDBN}
15190 @value{GDBN} can be used to debug programs written in Fortran, but it
15191 currently supports only the features of Fortran 77 language.
15193 @cindex trailing underscore, in Fortran symbols
15194 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
15195 among them) append an underscore to the names of variables and
15196 functions. When you debug programs compiled by those compilers, you
15197 will need to refer to variables and functions with a trailing
15201 * Fortran Operators:: Fortran operators and expressions
15202 * Fortran Defaults:: Default settings for Fortran
15203 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
15206 @node Fortran Operators
15207 @subsubsection Fortran Operators and Expressions
15209 @cindex Fortran operators and expressions
15211 Operators must be defined on values of specific types. For instance,
15212 @code{+} is defined on numbers, but not on characters or other non-
15213 arithmetic types. Operators are often defined on groups of types.
15217 The exponentiation operator. It raises the first operand to the power
15221 The range operator. Normally used in the form of array(low:high) to
15222 represent a section of array.
15225 The access component operator. Normally used to access elements in derived
15226 types. Also suitable for unions. As unions aren't part of regular Fortran,
15227 this can only happen when accessing a register that uses a gdbarch-defined
15231 @node Fortran Defaults
15232 @subsubsection Fortran Defaults
15234 @cindex Fortran Defaults
15236 Fortran symbols are usually case-insensitive, so @value{GDBN} by
15237 default uses case-insensitive matches for Fortran symbols. You can
15238 change that with the @samp{set case-insensitive} command, see
15239 @ref{Symbols}, for the details.
15241 @node Special Fortran Commands
15242 @subsubsection Special Fortran Commands
15244 @cindex Special Fortran commands
15246 @value{GDBN} has some commands to support Fortran-specific features,
15247 such as displaying common blocks.
15250 @cindex @code{COMMON} blocks, Fortran
15251 @kindex info common
15252 @item info common @r{[}@var{common-name}@r{]}
15253 This command prints the values contained in the Fortran @code{COMMON}
15254 block whose name is @var{common-name}. With no argument, the names of
15255 all @code{COMMON} blocks visible at the current program location are
15262 @cindex Pascal support in @value{GDBN}, limitations
15263 Debugging Pascal programs which use sets, subranges, file variables, or
15264 nested functions does not currently work. @value{GDBN} does not support
15265 entering expressions, printing values, or similar features using Pascal
15268 The Pascal-specific command @code{set print pascal_static-members}
15269 controls whether static members of Pascal objects are displayed.
15270 @xref{Print Settings, pascal_static-members}.
15275 @value{GDBN} supports the @url{https://www.rust-lang.org/, Rust
15276 Programming Language}. Type- and value-printing, and expression
15277 parsing, are reasonably complete. However, there are a few
15278 peculiarities and holes to be aware of.
15282 Linespecs (@pxref{Specify Location}) are never relative to the current
15283 crate. Instead, they act as if there were a global namespace of
15284 crates, somewhat similar to the way @code{extern crate} behaves.
15286 That is, if @value{GDBN} is stopped at a breakpoint in a function in
15287 crate @samp{A}, module @samp{B}, then @code{break B::f} will attempt
15288 to set a breakpoint in a function named @samp{f} in a crate named
15291 As a consequence of this approach, linespecs also cannot refer to
15292 items using @samp{self::} or @samp{super::}.
15295 Because @value{GDBN} implements Rust name-lookup semantics in
15296 expressions, it will sometimes prepend the current crate to a name.
15297 For example, if @value{GDBN} is stopped at a breakpoint in the crate
15298 @samp{K}, then @code{print ::x::y} will try to find the symbol
15301 However, since it is useful to be able to refer to other crates when
15302 debugging, @value{GDBN} provides the @code{extern} extension to
15303 circumvent this. To use the extension, just put @code{extern} before
15304 a path expression to refer to the otherwise unavailable ``global''
15307 In the above example, if you wanted to refer to the symbol @samp{y} in
15308 the crate @samp{x}, you would use @code{print extern x::y}.
15311 The Rust expression evaluator does not support ``statement-like''
15312 expressions such as @code{if} or @code{match}, or lambda expressions.
15315 Tuple expressions are not implemented.
15318 The Rust expression evaluator does not currently implement the
15319 @code{Drop} trait. Objects that may be created by the evaluator will
15320 never be destroyed.
15323 @value{GDBN} does not implement type inference for generics. In order
15324 to call generic functions or otherwise refer to generic items, you
15325 will have to specify the type parameters manually.
15328 @value{GDBN} currently uses the C@t{++} demangler for Rust. In most
15329 cases this does not cause any problems. However, in an expression
15330 context, completing a generic function name will give syntactically
15331 invalid results. This happens because Rust requires the @samp{::}
15332 operator between the function name and its generic arguments. For
15333 example, @value{GDBN} might provide a completion like
15334 @code{crate::f<u32>}, where the parser would require
15335 @code{crate::f::<u32>}.
15338 As of this writing, the Rust compiler (version 1.8) has a few holes in
15339 the debugging information it generates. These holes prevent certain
15340 features from being implemented by @value{GDBN}:
15344 Method calls cannot be made via traits.
15347 Trait objects cannot be created or inspected.
15350 Operator overloading is not implemented.
15353 When debugging in a monomorphized function, you cannot use the generic
15357 The type @code{Self} is not available.
15360 @code{use} statements are not available, so some names may not be
15361 available in the crate.
15366 @subsection Modula-2
15368 @cindex Modula-2, @value{GDBN} support
15370 The extensions made to @value{GDBN} to support Modula-2 only support
15371 output from the @sc{gnu} Modula-2 compiler (which is currently being
15372 developed). Other Modula-2 compilers are not currently supported, and
15373 attempting to debug executables produced by them is most likely
15374 to give an error as @value{GDBN} reads in the executable's symbol
15377 @cindex expressions in Modula-2
15379 * M2 Operators:: Built-in operators
15380 * Built-In Func/Proc:: Built-in functions and procedures
15381 * M2 Constants:: Modula-2 constants
15382 * M2 Types:: Modula-2 types
15383 * M2 Defaults:: Default settings for Modula-2
15384 * Deviations:: Deviations from standard Modula-2
15385 * M2 Checks:: Modula-2 type and range checks
15386 * M2 Scope:: The scope operators @code{::} and @code{.}
15387 * GDB/M2:: @value{GDBN} and Modula-2
15391 @subsubsection Operators
15392 @cindex Modula-2 operators
15394 Operators must be defined on values of specific types. For instance,
15395 @code{+} is defined on numbers, but not on structures. Operators are
15396 often defined on groups of types. For the purposes of Modula-2, the
15397 following definitions hold:
15402 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
15406 @emph{Character types} consist of @code{CHAR} and its subranges.
15409 @emph{Floating-point types} consist of @code{REAL}.
15412 @emph{Pointer types} consist of anything declared as @code{POINTER TO
15416 @emph{Scalar types} consist of all of the above.
15419 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
15422 @emph{Boolean types} consist of @code{BOOLEAN}.
15426 The following operators are supported, and appear in order of
15427 increasing precedence:
15431 Function argument or array index separator.
15434 Assignment. The value of @var{var} @code{:=} @var{value} is
15438 Less than, greater than on integral, floating-point, or enumerated
15442 Less than or equal to, greater than or equal to
15443 on integral, floating-point and enumerated types, or set inclusion on
15444 set types. Same precedence as @code{<}.
15446 @item =@r{, }<>@r{, }#
15447 Equality and two ways of expressing inequality, valid on scalar types.
15448 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
15449 available for inequality, since @code{#} conflicts with the script
15453 Set membership. Defined on set types and the types of their members.
15454 Same precedence as @code{<}.
15457 Boolean disjunction. Defined on boolean types.
15460 Boolean conjunction. Defined on boolean types.
15463 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
15466 Addition and subtraction on integral and floating-point types, or union
15467 and difference on set types.
15470 Multiplication on integral and floating-point types, or set intersection
15474 Division on floating-point types, or symmetric set difference on set
15475 types. Same precedence as @code{*}.
15478 Integer division and remainder. Defined on integral types. Same
15479 precedence as @code{*}.
15482 Negative. Defined on @code{INTEGER} and @code{REAL} data.
15485 Pointer dereferencing. Defined on pointer types.
15488 Boolean negation. Defined on boolean types. Same precedence as
15492 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
15493 precedence as @code{^}.
15496 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
15499 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
15503 @value{GDBN} and Modula-2 scope operators.
15507 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
15508 treats the use of the operator @code{IN}, or the use of operators
15509 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
15510 @code{<=}, and @code{>=} on sets as an error.
15514 @node Built-In Func/Proc
15515 @subsubsection Built-in Functions and Procedures
15516 @cindex Modula-2 built-ins
15518 Modula-2 also makes available several built-in procedures and functions.
15519 In describing these, the following metavariables are used:
15524 represents an @code{ARRAY} variable.
15527 represents a @code{CHAR} constant or variable.
15530 represents a variable or constant of integral type.
15533 represents an identifier that belongs to a set. Generally used in the
15534 same function with the metavariable @var{s}. The type of @var{s} should
15535 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
15538 represents a variable or constant of integral or floating-point type.
15541 represents a variable or constant of floating-point type.
15547 represents a variable.
15550 represents a variable or constant of one of many types. See the
15551 explanation of the function for details.
15554 All Modula-2 built-in procedures also return a result, described below.
15558 Returns the absolute value of @var{n}.
15561 If @var{c} is a lower case letter, it returns its upper case
15562 equivalent, otherwise it returns its argument.
15565 Returns the character whose ordinal value is @var{i}.
15568 Decrements the value in the variable @var{v} by one. Returns the new value.
15570 @item DEC(@var{v},@var{i})
15571 Decrements the value in the variable @var{v} by @var{i}. Returns the
15574 @item EXCL(@var{m},@var{s})
15575 Removes the element @var{m} from the set @var{s}. Returns the new
15578 @item FLOAT(@var{i})
15579 Returns the floating point equivalent of the integer @var{i}.
15581 @item HIGH(@var{a})
15582 Returns the index of the last member of @var{a}.
15585 Increments the value in the variable @var{v} by one. Returns the new value.
15587 @item INC(@var{v},@var{i})
15588 Increments the value in the variable @var{v} by @var{i}. Returns the
15591 @item INCL(@var{m},@var{s})
15592 Adds the element @var{m} to the set @var{s} if it is not already
15593 there. Returns the new set.
15596 Returns the maximum value of the type @var{t}.
15599 Returns the minimum value of the type @var{t}.
15602 Returns boolean TRUE if @var{i} is an odd number.
15605 Returns the ordinal value of its argument. For example, the ordinal
15606 value of a character is its @sc{ascii} value (on machines supporting
15607 the @sc{ascii} character set). The argument @var{x} must be of an
15608 ordered type, which include integral, character and enumerated types.
15610 @item SIZE(@var{x})
15611 Returns the size of its argument. The argument @var{x} can be a
15612 variable or a type.
15614 @item TRUNC(@var{r})
15615 Returns the integral part of @var{r}.
15617 @item TSIZE(@var{x})
15618 Returns the size of its argument. The argument @var{x} can be a
15619 variable or a type.
15621 @item VAL(@var{t},@var{i})
15622 Returns the member of the type @var{t} whose ordinal value is @var{i}.
15626 @emph{Warning:} Sets and their operations are not yet supported, so
15627 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
15631 @cindex Modula-2 constants
15633 @subsubsection Constants
15635 @value{GDBN} allows you to express the constants of Modula-2 in the following
15641 Integer constants are simply a sequence of digits. When used in an
15642 expression, a constant is interpreted to be type-compatible with the
15643 rest of the expression. Hexadecimal integers are specified by a
15644 trailing @samp{H}, and octal integers by a trailing @samp{B}.
15647 Floating point constants appear as a sequence of digits, followed by a
15648 decimal point and another sequence of digits. An optional exponent can
15649 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
15650 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
15651 digits of the floating point constant must be valid decimal (base 10)
15655 Character constants consist of a single character enclosed by a pair of
15656 like quotes, either single (@code{'}) or double (@code{"}). They may
15657 also be expressed by their ordinal value (their @sc{ascii} value, usually)
15658 followed by a @samp{C}.
15661 String constants consist of a sequence of characters enclosed by a
15662 pair of like quotes, either single (@code{'}) or double (@code{"}).
15663 Escape sequences in the style of C are also allowed. @xref{C
15664 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
15668 Enumerated constants consist of an enumerated identifier.
15671 Boolean constants consist of the identifiers @code{TRUE} and
15675 Pointer constants consist of integral values only.
15678 Set constants are not yet supported.
15682 @subsubsection Modula-2 Types
15683 @cindex Modula-2 types
15685 Currently @value{GDBN} can print the following data types in Modula-2
15686 syntax: array types, record types, set types, pointer types, procedure
15687 types, enumerated types, subrange types and base types. You can also
15688 print the contents of variables declared using these type.
15689 This section gives a number of simple source code examples together with
15690 sample @value{GDBN} sessions.
15692 The first example contains the following section of code:
15701 and you can request @value{GDBN} to interrogate the type and value of
15702 @code{r} and @code{s}.
15705 (@value{GDBP}) print s
15707 (@value{GDBP}) ptype s
15709 (@value{GDBP}) print r
15711 (@value{GDBP}) ptype r
15716 Likewise if your source code declares @code{s} as:
15720 s: SET ['A'..'Z'] ;
15724 then you may query the type of @code{s} by:
15727 (@value{GDBP}) ptype s
15728 type = SET ['A'..'Z']
15732 Note that at present you cannot interactively manipulate set
15733 expressions using the debugger.
15735 The following example shows how you might declare an array in Modula-2
15736 and how you can interact with @value{GDBN} to print its type and contents:
15740 s: ARRAY [-10..10] OF CHAR ;
15744 (@value{GDBP}) ptype s
15745 ARRAY [-10..10] OF CHAR
15748 Note that the array handling is not yet complete and although the type
15749 is printed correctly, expression handling still assumes that all
15750 arrays have a lower bound of zero and not @code{-10} as in the example
15753 Here are some more type related Modula-2 examples:
15757 colour = (blue, red, yellow, green) ;
15758 t = [blue..yellow] ;
15766 The @value{GDBN} interaction shows how you can query the data type
15767 and value of a variable.
15770 (@value{GDBP}) print s
15772 (@value{GDBP}) ptype t
15773 type = [blue..yellow]
15777 In this example a Modula-2 array is declared and its contents
15778 displayed. Observe that the contents are written in the same way as
15779 their @code{C} counterparts.
15783 s: ARRAY [1..5] OF CARDINAL ;
15789 (@value{GDBP}) print s
15790 $1 = @{1, 0, 0, 0, 0@}
15791 (@value{GDBP}) ptype s
15792 type = ARRAY [1..5] OF CARDINAL
15795 The Modula-2 language interface to @value{GDBN} also understands
15796 pointer types as shown in this example:
15800 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
15807 and you can request that @value{GDBN} describes the type of @code{s}.
15810 (@value{GDBP}) ptype s
15811 type = POINTER TO ARRAY [1..5] OF CARDINAL
15814 @value{GDBN} handles compound types as we can see in this example.
15815 Here we combine array types, record types, pointer types and subrange
15826 myarray = ARRAY myrange OF CARDINAL ;
15827 myrange = [-2..2] ;
15829 s: POINTER TO ARRAY myrange OF foo ;
15833 and you can ask @value{GDBN} to describe the type of @code{s} as shown
15837 (@value{GDBP}) ptype s
15838 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
15841 f3 : ARRAY [-2..2] OF CARDINAL;
15846 @subsubsection Modula-2 Defaults
15847 @cindex Modula-2 defaults
15849 If type and range checking are set automatically by @value{GDBN}, they
15850 both default to @code{on} whenever the working language changes to
15851 Modula-2. This happens regardless of whether you or @value{GDBN}
15852 selected the working language.
15854 If you allow @value{GDBN} to set the language automatically, then entering
15855 code compiled from a file whose name ends with @file{.mod} sets the
15856 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
15857 Infer the Source Language}, for further details.
15860 @subsubsection Deviations from Standard Modula-2
15861 @cindex Modula-2, deviations from
15863 A few changes have been made to make Modula-2 programs easier to debug.
15864 This is done primarily via loosening its type strictness:
15868 Unlike in standard Modula-2, pointer constants can be formed by
15869 integers. This allows you to modify pointer variables during
15870 debugging. (In standard Modula-2, the actual address contained in a
15871 pointer variable is hidden from you; it can only be modified
15872 through direct assignment to another pointer variable or expression that
15873 returned a pointer.)
15876 C escape sequences can be used in strings and characters to represent
15877 non-printable characters. @value{GDBN} prints out strings with these
15878 escape sequences embedded. Single non-printable characters are
15879 printed using the @samp{CHR(@var{nnn})} format.
15882 The assignment operator (@code{:=}) returns the value of its right-hand
15886 All built-in procedures both modify @emph{and} return their argument.
15890 @subsubsection Modula-2 Type and Range Checks
15891 @cindex Modula-2 checks
15894 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
15897 @c FIXME remove warning when type/range checks added
15899 @value{GDBN} considers two Modula-2 variables type equivalent if:
15903 They are of types that have been declared equivalent via a @code{TYPE
15904 @var{t1} = @var{t2}} statement
15907 They have been declared on the same line. (Note: This is true of the
15908 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
15911 As long as type checking is enabled, any attempt to combine variables
15912 whose types are not equivalent is an error.
15914 Range checking is done on all mathematical operations, assignment, array
15915 index bounds, and all built-in functions and procedures.
15918 @subsubsection The Scope Operators @code{::} and @code{.}
15920 @cindex @code{.}, Modula-2 scope operator
15921 @cindex colon, doubled as scope operator
15923 @vindex colon-colon@r{, in Modula-2}
15924 @c Info cannot handle :: but TeX can.
15927 @vindex ::@r{, in Modula-2}
15930 There are a few subtle differences between the Modula-2 scope operator
15931 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
15936 @var{module} . @var{id}
15937 @var{scope} :: @var{id}
15941 where @var{scope} is the name of a module or a procedure,
15942 @var{module} the name of a module, and @var{id} is any declared
15943 identifier within your program, except another module.
15945 Using the @code{::} operator makes @value{GDBN} search the scope
15946 specified by @var{scope} for the identifier @var{id}. If it is not
15947 found in the specified scope, then @value{GDBN} searches all scopes
15948 enclosing the one specified by @var{scope}.
15950 Using the @code{.} operator makes @value{GDBN} search the current scope for
15951 the identifier specified by @var{id} that was imported from the
15952 definition module specified by @var{module}. With this operator, it is
15953 an error if the identifier @var{id} was not imported from definition
15954 module @var{module}, or if @var{id} is not an identifier in
15958 @subsubsection @value{GDBN} and Modula-2
15960 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
15961 Five subcommands of @code{set print} and @code{show print} apply
15962 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
15963 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
15964 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
15965 analogue in Modula-2.
15967 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
15968 with any language, is not useful with Modula-2. Its
15969 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
15970 created in Modula-2 as they can in C or C@t{++}. However, because an
15971 address can be specified by an integral constant, the construct
15972 @samp{@{@var{type}@}@var{adrexp}} is still useful.
15974 @cindex @code{#} in Modula-2
15975 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
15976 interpreted as the beginning of a comment. Use @code{<>} instead.
15982 The extensions made to @value{GDBN} for Ada only support
15983 output from the @sc{gnu} Ada (GNAT) compiler.
15984 Other Ada compilers are not currently supported, and
15985 attempting to debug executables produced by them is most likely
15989 @cindex expressions in Ada
15991 * Ada Mode Intro:: General remarks on the Ada syntax
15992 and semantics supported by Ada mode
15994 * Omissions from Ada:: Restrictions on the Ada expression syntax.
15995 * Additions to Ada:: Extensions of the Ada expression syntax.
15996 * Overloading support for Ada:: Support for expressions involving overloaded
15998 * Stopping Before Main Program:: Debugging the program during elaboration.
15999 * Ada Exceptions:: Ada Exceptions
16000 * Ada Tasks:: Listing and setting breakpoints in tasks.
16001 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
16002 * Ravenscar Profile:: Tasking Support when using the Ravenscar
16004 * Ada Glitches:: Known peculiarities of Ada mode.
16007 @node Ada Mode Intro
16008 @subsubsection Introduction
16009 @cindex Ada mode, general
16011 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
16012 syntax, with some extensions.
16013 The philosophy behind the design of this subset is
16017 That @value{GDBN} should provide basic literals and access to operations for
16018 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
16019 leaving more sophisticated computations to subprograms written into the
16020 program (which therefore may be called from @value{GDBN}).
16023 That type safety and strict adherence to Ada language restrictions
16024 are not particularly important to the @value{GDBN} user.
16027 That brevity is important to the @value{GDBN} user.
16030 Thus, for brevity, the debugger acts as if all names declared in
16031 user-written packages are directly visible, even if they are not visible
16032 according to Ada rules, thus making it unnecessary to fully qualify most
16033 names with their packages, regardless of context. Where this causes
16034 ambiguity, @value{GDBN} asks the user's intent.
16036 The debugger will start in Ada mode if it detects an Ada main program.
16037 As for other languages, it will enter Ada mode when stopped in a program that
16038 was translated from an Ada source file.
16040 While in Ada mode, you may use `@t{--}' for comments. This is useful
16041 mostly for documenting command files. The standard @value{GDBN} comment
16042 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
16043 middle (to allow based literals).
16045 @node Omissions from Ada
16046 @subsubsection Omissions from Ada
16047 @cindex Ada, omissions from
16049 Here are the notable omissions from the subset:
16053 Only a subset of the attributes are supported:
16057 @t{'First}, @t{'Last}, and @t{'Length}
16058 on array objects (not on types and subtypes).
16061 @t{'Min} and @t{'Max}.
16064 @t{'Pos} and @t{'Val}.
16070 @t{'Range} on array objects (not subtypes), but only as the right
16071 operand of the membership (@code{in}) operator.
16074 @t{'Access}, @t{'Unchecked_Access}, and
16075 @t{'Unrestricted_Access} (a GNAT extension).
16083 @code{Characters.Latin_1} are not available and
16084 concatenation is not implemented. Thus, escape characters in strings are
16085 not currently available.
16088 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
16089 equality of representations. They will generally work correctly
16090 for strings and arrays whose elements have integer or enumeration types.
16091 They may not work correctly for arrays whose element
16092 types have user-defined equality, for arrays of real values
16093 (in particular, IEEE-conformant floating point, because of negative
16094 zeroes and NaNs), and for arrays whose elements contain unused bits with
16095 indeterminate values.
16098 The other component-by-component array operations (@code{and}, @code{or},
16099 @code{xor}, @code{not}, and relational tests other than equality)
16100 are not implemented.
16103 @cindex array aggregates (Ada)
16104 @cindex record aggregates (Ada)
16105 @cindex aggregates (Ada)
16106 There is limited support for array and record aggregates. They are
16107 permitted only on the right sides of assignments, as in these examples:
16110 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
16111 (@value{GDBP}) set An_Array := (1, others => 0)
16112 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
16113 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
16114 (@value{GDBP}) set A_Record := (1, "Peter", True);
16115 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
16119 discriminant's value by assigning an aggregate has an
16120 undefined effect if that discriminant is used within the record.
16121 However, you can first modify discriminants by directly assigning to
16122 them (which normally would not be allowed in Ada), and then performing an
16123 aggregate assignment. For example, given a variable @code{A_Rec}
16124 declared to have a type such as:
16127 type Rec (Len : Small_Integer := 0) is record
16129 Vals : IntArray (1 .. Len);
16133 you can assign a value with a different size of @code{Vals} with two
16137 (@value{GDBP}) set A_Rec.Len := 4
16138 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
16141 As this example also illustrates, @value{GDBN} is very loose about the usual
16142 rules concerning aggregates. You may leave out some of the
16143 components of an array or record aggregate (such as the @code{Len}
16144 component in the assignment to @code{A_Rec} above); they will retain their
16145 original values upon assignment. You may freely use dynamic values as
16146 indices in component associations. You may even use overlapping or
16147 redundant component associations, although which component values are
16148 assigned in such cases is not defined.
16151 Calls to dispatching subprograms are not implemented.
16154 The overloading algorithm is much more limited (i.e., less selective)
16155 than that of real Ada. It makes only limited use of the context in
16156 which a subexpression appears to resolve its meaning, and it is much
16157 looser in its rules for allowing type matches. As a result, some
16158 function calls will be ambiguous, and the user will be asked to choose
16159 the proper resolution.
16162 The @code{new} operator is not implemented.
16165 Entry calls are not implemented.
16168 Aside from printing, arithmetic operations on the native VAX floating-point
16169 formats are not supported.
16172 It is not possible to slice a packed array.
16175 The names @code{True} and @code{False}, when not part of a qualified name,
16176 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
16178 Should your program
16179 redefine these names in a package or procedure (at best a dubious practice),
16180 you will have to use fully qualified names to access their new definitions.
16183 @node Additions to Ada
16184 @subsubsection Additions to Ada
16185 @cindex Ada, deviations from
16187 As it does for other languages, @value{GDBN} makes certain generic
16188 extensions to Ada (@pxref{Expressions}):
16192 If the expression @var{E} is a variable residing in memory (typically
16193 a local variable or array element) and @var{N} is a positive integer,
16194 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
16195 @var{N}-1 adjacent variables following it in memory as an array. In
16196 Ada, this operator is generally not necessary, since its prime use is
16197 in displaying parts of an array, and slicing will usually do this in
16198 Ada. However, there are occasional uses when debugging programs in
16199 which certain debugging information has been optimized away.
16202 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
16203 appears in function or file @var{B}.'' When @var{B} is a file name,
16204 you must typically surround it in single quotes.
16207 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
16208 @var{type} that appears at address @var{addr}.''
16211 A name starting with @samp{$} is a convenience variable
16212 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
16215 In addition, @value{GDBN} provides a few other shortcuts and outright
16216 additions specific to Ada:
16220 The assignment statement is allowed as an expression, returning
16221 its right-hand operand as its value. Thus, you may enter
16224 (@value{GDBP}) set x := y + 3
16225 (@value{GDBP}) print A(tmp := y + 1)
16229 The semicolon is allowed as an ``operator,'' returning as its value
16230 the value of its right-hand operand.
16231 This allows, for example,
16232 complex conditional breaks:
16235 (@value{GDBP}) break f
16236 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
16240 Rather than use catenation and symbolic character names to introduce special
16241 characters into strings, one may instead use a special bracket notation,
16242 which is also used to print strings. A sequence of characters of the form
16243 @samp{["@var{XX}"]} within a string or character literal denotes the
16244 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
16245 sequence of characters @samp{["""]} also denotes a single quotation mark
16246 in strings. For example,
16248 "One line.["0a"]Next line.["0a"]"
16251 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
16255 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
16256 @t{'Max} is optional (and is ignored in any case). For example, it is valid
16260 (@value{GDBP}) print 'max(x, y)
16264 When printing arrays, @value{GDBN} uses positional notation when the
16265 array has a lower bound of 1, and uses a modified named notation otherwise.
16266 For example, a one-dimensional array of three integers with a lower bound
16267 of 3 might print as
16274 That is, in contrast to valid Ada, only the first component has a @code{=>}
16278 You may abbreviate attributes in expressions with any unique,
16279 multi-character subsequence of
16280 their names (an exact match gets preference).
16281 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
16282 in place of @t{a'length}.
16285 @cindex quoting Ada internal identifiers
16286 Since Ada is case-insensitive, the debugger normally maps identifiers you type
16287 to lower case. The GNAT compiler uses upper-case characters for
16288 some of its internal identifiers, which are normally of no interest to users.
16289 For the rare occasions when you actually have to look at them,
16290 enclose them in angle brackets to avoid the lower-case mapping.
16293 (@value{GDBP}) print <JMPBUF_SAVE>[0]
16297 Printing an object of class-wide type or dereferencing an
16298 access-to-class-wide value will display all the components of the object's
16299 specific type (as indicated by its run-time tag). Likewise, component
16300 selection on such a value will operate on the specific type of the
16305 @node Overloading support for Ada
16306 @subsubsection Overloading support for Ada
16307 @cindex overloading, Ada
16309 The debugger supports limited overloading. Given a subprogram call in which
16310 the function symbol has multiple definitions, it will use the number of
16311 actual parameters and some information about their types to attempt to narrow
16312 the set of definitions. It also makes very limited use of context, preferring
16313 procedures to functions in the context of the @code{call} command, and
16314 functions to procedures elsewhere.
16316 If, after narrowing, the set of matching definitions still contains more than
16317 one definition, @value{GDBN} will display a menu to query which one it should
16321 (@value{GDBP}) print f(1)
16322 Multiple matches for f
16324 [1] foo.f (integer) return boolean at foo.adb:23
16325 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
16329 In this case, just select one menu entry either to cancel expression evaluation
16330 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
16331 instance (type the corresponding number and press @key{RET}).
16333 Here are a couple of commands to customize @value{GDBN}'s behavior in this
16338 @kindex set ada print-signatures
16339 @item set ada print-signatures
16340 Control whether parameter types and return types are displayed in overloads
16341 selection menus. It is @code{on} by default.
16342 @xref{Overloading support for Ada}.
16344 @kindex show ada print-signatures
16345 @item show ada print-signatures
16346 Show the current setting for displaying parameter types and return types in
16347 overloads selection menu.
16348 @xref{Overloading support for Ada}.
16352 @node Stopping Before Main Program
16353 @subsubsection Stopping at the Very Beginning
16355 @cindex breakpointing Ada elaboration code
16356 It is sometimes necessary to debug the program during elaboration, and
16357 before reaching the main procedure.
16358 As defined in the Ada Reference
16359 Manual, the elaboration code is invoked from a procedure called
16360 @code{adainit}. To run your program up to the beginning of
16361 elaboration, simply use the following two commands:
16362 @code{tbreak adainit} and @code{run}.
16364 @node Ada Exceptions
16365 @subsubsection Ada Exceptions
16367 A command is provided to list all Ada exceptions:
16370 @kindex info exceptions
16371 @item info exceptions
16372 @itemx info exceptions @var{regexp}
16373 The @code{info exceptions} command allows you to list all Ada exceptions
16374 defined within the program being debugged, as well as their addresses.
16375 With a regular expression, @var{regexp}, as argument, only those exceptions
16376 whose names match @var{regexp} are listed.
16379 Below is a small example, showing how the command can be used, first
16380 without argument, and next with a regular expression passed as an
16384 (@value{GDBP}) info exceptions
16385 All defined Ada exceptions:
16386 constraint_error: 0x613da0
16387 program_error: 0x613d20
16388 storage_error: 0x613ce0
16389 tasking_error: 0x613ca0
16390 const.aint_global_e: 0x613b00
16391 (@value{GDBP}) info exceptions const.aint
16392 All Ada exceptions matching regular expression "const.aint":
16393 constraint_error: 0x613da0
16394 const.aint_global_e: 0x613b00
16397 It is also possible to ask @value{GDBN} to stop your program's execution
16398 when an exception is raised. For more details, see @ref{Set Catchpoints}.
16401 @subsubsection Extensions for Ada Tasks
16402 @cindex Ada, tasking
16404 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
16405 @value{GDBN} provides the following task-related commands:
16410 This command shows a list of current Ada tasks, as in the following example:
16417 (@value{GDBP}) info tasks
16418 ID TID P-ID Pri State Name
16419 1 8088000 0 15 Child Activation Wait main_task
16420 2 80a4000 1 15 Accept Statement b
16421 3 809a800 1 15 Child Activation Wait a
16422 * 4 80ae800 3 15 Runnable c
16427 In this listing, the asterisk before the last task indicates it to be the
16428 task currently being inspected.
16432 Represents @value{GDBN}'s internal task number.
16438 The parent's task ID (@value{GDBN}'s internal task number).
16441 The base priority of the task.
16444 Current state of the task.
16448 The task has been created but has not been activated. It cannot be
16452 The task is not blocked for any reason known to Ada. (It may be waiting
16453 for a mutex, though.) It is conceptually "executing" in normal mode.
16456 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
16457 that were waiting on terminate alternatives have been awakened and have
16458 terminated themselves.
16460 @item Child Activation Wait
16461 The task is waiting for created tasks to complete activation.
16463 @item Accept Statement
16464 The task is waiting on an accept or selective wait statement.
16466 @item Waiting on entry call
16467 The task is waiting on an entry call.
16469 @item Async Select Wait
16470 The task is waiting to start the abortable part of an asynchronous
16474 The task is waiting on a select statement with only a delay
16477 @item Child Termination Wait
16478 The task is sleeping having completed a master within itself, and is
16479 waiting for the tasks dependent on that master to become terminated or
16480 waiting on a terminate Phase.
16482 @item Wait Child in Term Alt
16483 The task is sleeping waiting for tasks on terminate alternatives to
16484 finish terminating.
16486 @item Accepting RV with @var{taskno}
16487 The task is accepting a rendez-vous with the task @var{taskno}.
16491 Name of the task in the program.
16495 @kindex info task @var{taskno}
16496 @item info task @var{taskno}
16497 This command shows detailled informations on the specified task, as in
16498 the following example:
16503 (@value{GDBP}) info tasks
16504 ID TID P-ID Pri State Name
16505 1 8077880 0 15 Child Activation Wait main_task
16506 * 2 807c468 1 15 Runnable task_1
16507 (@value{GDBP}) info task 2
16508 Ada Task: 0x807c468
16511 Parent: 1 (main_task)
16517 @kindex task@r{ (Ada)}
16518 @cindex current Ada task ID
16519 This command prints the ID of the current task.
16525 (@value{GDBP}) info tasks
16526 ID TID P-ID Pri State Name
16527 1 8077870 0 15 Child Activation Wait main_task
16528 * 2 807c458 1 15 Runnable t
16529 (@value{GDBP}) task
16530 [Current task is 2]
16533 @item task @var{taskno}
16534 @cindex Ada task switching
16535 This command is like the @code{thread @var{thread-id}}
16536 command (@pxref{Threads}). It switches the context of debugging
16537 from the current task to the given task.
16543 (@value{GDBP}) info tasks
16544 ID TID P-ID Pri State Name
16545 1 8077870 0 15 Child Activation Wait main_task
16546 * 2 807c458 1 15 Runnable t
16547 (@value{GDBP}) task 1
16548 [Switching to task 1]
16549 #0 0x8067726 in pthread_cond_wait ()
16551 #0 0x8067726 in pthread_cond_wait ()
16552 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
16553 #2 0x805cb63 in system.task_primitives.operations.sleep ()
16554 #3 0x806153e in system.tasking.stages.activate_tasks ()
16555 #4 0x804aacc in un () at un.adb:5
16558 @item break @var{location} task @var{taskno}
16559 @itemx break @var{location} task @var{taskno} if @dots{}
16560 @cindex breakpoints and tasks, in Ada
16561 @cindex task breakpoints, in Ada
16562 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
16563 These commands are like the @code{break @dots{} thread @dots{}}
16564 command (@pxref{Thread Stops}). The
16565 @var{location} argument specifies source lines, as described
16566 in @ref{Specify Location}.
16568 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
16569 to specify that you only want @value{GDBN} to stop the program when a
16570 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
16571 numeric task identifiers assigned by @value{GDBN}, shown in the first
16572 column of the @samp{info tasks} display.
16574 If you do not specify @samp{task @var{taskno}} when you set a
16575 breakpoint, the breakpoint applies to @emph{all} tasks of your
16578 You can use the @code{task} qualifier on conditional breakpoints as
16579 well; in this case, place @samp{task @var{taskno}} before the
16580 breakpoint condition (before the @code{if}).
16588 (@value{GDBP}) info tasks
16589 ID TID P-ID Pri State Name
16590 1 140022020 0 15 Child Activation Wait main_task
16591 2 140045060 1 15 Accept/Select Wait t2
16592 3 140044840 1 15 Runnable t1
16593 * 4 140056040 1 15 Runnable t3
16594 (@value{GDBP}) b 15 task 2
16595 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
16596 (@value{GDBP}) cont
16601 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
16603 (@value{GDBP}) info tasks
16604 ID TID P-ID Pri State Name
16605 1 140022020 0 15 Child Activation Wait main_task
16606 * 2 140045060 1 15 Runnable t2
16607 3 140044840 1 15 Runnable t1
16608 4 140056040 1 15 Delay Sleep t3
16612 @node Ada Tasks and Core Files
16613 @subsubsection Tasking Support when Debugging Core Files
16614 @cindex Ada tasking and core file debugging
16616 When inspecting a core file, as opposed to debugging a live program,
16617 tasking support may be limited or even unavailable, depending on
16618 the platform being used.
16619 For instance, on x86-linux, the list of tasks is available, but task
16620 switching is not supported.
16622 On certain platforms, the debugger needs to perform some
16623 memory writes in order to provide Ada tasking support. When inspecting
16624 a core file, this means that the core file must be opened with read-write
16625 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
16626 Under these circumstances, you should make a backup copy of the core
16627 file before inspecting it with @value{GDBN}.
16629 @node Ravenscar Profile
16630 @subsubsection Tasking Support when using the Ravenscar Profile
16631 @cindex Ravenscar Profile
16633 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
16634 specifically designed for systems with safety-critical real-time
16638 @kindex set ravenscar task-switching on
16639 @cindex task switching with program using Ravenscar Profile
16640 @item set ravenscar task-switching on
16641 Allows task switching when debugging a program that uses the Ravenscar
16642 Profile. This is the default.
16644 @kindex set ravenscar task-switching off
16645 @item set ravenscar task-switching off
16646 Turn off task switching when debugging a program that uses the Ravenscar
16647 Profile. This is mostly intended to disable the code that adds support
16648 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
16649 the Ravenscar runtime is preventing @value{GDBN} from working properly.
16650 To be effective, this command should be run before the program is started.
16652 @kindex show ravenscar task-switching
16653 @item show ravenscar task-switching
16654 Show whether it is possible to switch from task to task in a program
16655 using the Ravenscar Profile.
16660 @subsubsection Known Peculiarities of Ada Mode
16661 @cindex Ada, problems
16663 Besides the omissions listed previously (@pxref{Omissions from Ada}),
16664 we know of several problems with and limitations of Ada mode in
16666 some of which will be fixed with planned future releases of the debugger
16667 and the GNU Ada compiler.
16671 Static constants that the compiler chooses not to materialize as objects in
16672 storage are invisible to the debugger.
16675 Named parameter associations in function argument lists are ignored (the
16676 argument lists are treated as positional).
16679 Many useful library packages are currently invisible to the debugger.
16682 Fixed-point arithmetic, conversions, input, and output is carried out using
16683 floating-point arithmetic, and may give results that only approximate those on
16687 The GNAT compiler never generates the prefix @code{Standard} for any of
16688 the standard symbols defined by the Ada language. @value{GDBN} knows about
16689 this: it will strip the prefix from names when you use it, and will never
16690 look for a name you have so qualified among local symbols, nor match against
16691 symbols in other packages or subprograms. If you have
16692 defined entities anywhere in your program other than parameters and
16693 local variables whose simple names match names in @code{Standard},
16694 GNAT's lack of qualification here can cause confusion. When this happens,
16695 you can usually resolve the confusion
16696 by qualifying the problematic names with package
16697 @code{Standard} explicitly.
16700 Older versions of the compiler sometimes generate erroneous debugging
16701 information, resulting in the debugger incorrectly printing the value
16702 of affected entities. In some cases, the debugger is able to work
16703 around an issue automatically. In other cases, the debugger is able
16704 to work around the issue, but the work-around has to be specifically
16707 @kindex set ada trust-PAD-over-XVS
16708 @kindex show ada trust-PAD-over-XVS
16711 @item set ada trust-PAD-over-XVS on
16712 Configure GDB to strictly follow the GNAT encoding when computing the
16713 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
16714 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
16715 a complete description of the encoding used by the GNAT compiler).
16716 This is the default.
16718 @item set ada trust-PAD-over-XVS off
16719 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
16720 sometimes prints the wrong value for certain entities, changing @code{ada
16721 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
16722 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
16723 @code{off}, but this incurs a slight performance penalty, so it is
16724 recommended to leave this setting to @code{on} unless necessary.
16728 @cindex GNAT descriptive types
16729 @cindex GNAT encoding
16730 Internally, the debugger also relies on the compiler following a number
16731 of conventions known as the @samp{GNAT Encoding}, all documented in
16732 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
16733 how the debugging information should be generated for certain types.
16734 In particular, this convention makes use of @dfn{descriptive types},
16735 which are artificial types generated purely to help the debugger.
16737 These encodings were defined at a time when the debugging information
16738 format used was not powerful enough to describe some of the more complex
16739 types available in Ada. Since DWARF allows us to express nearly all
16740 Ada features, the long-term goal is to slowly replace these descriptive
16741 types by their pure DWARF equivalent. To facilitate that transition,
16742 a new maintenance option is available to force the debugger to ignore
16743 those descriptive types. It allows the user to quickly evaluate how
16744 well @value{GDBN} works without them.
16748 @kindex maint ada set ignore-descriptive-types
16749 @item maintenance ada set ignore-descriptive-types [on|off]
16750 Control whether the debugger should ignore descriptive types.
16751 The default is not to ignore descriptives types (@code{off}).
16753 @kindex maint ada show ignore-descriptive-types
16754 @item maintenance ada show ignore-descriptive-types
16755 Show if descriptive types are ignored by @value{GDBN}.
16759 @node Unsupported Languages
16760 @section Unsupported Languages
16762 @cindex unsupported languages
16763 @cindex minimal language
16764 In addition to the other fully-supported programming languages,
16765 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
16766 It does not represent a real programming language, but provides a set
16767 of capabilities close to what the C or assembly languages provide.
16768 This should allow most simple operations to be performed while debugging
16769 an application that uses a language currently not supported by @value{GDBN}.
16771 If the language is set to @code{auto}, @value{GDBN} will automatically
16772 select this language if the current frame corresponds to an unsupported
16776 @chapter Examining the Symbol Table
16778 The commands described in this chapter allow you to inquire about the
16779 symbols (names of variables, functions and types) defined in your
16780 program. This information is inherent in the text of your program and
16781 does not change as your program executes. @value{GDBN} finds it in your
16782 program's symbol table, in the file indicated when you started @value{GDBN}
16783 (@pxref{File Options, ,Choosing Files}), or by one of the
16784 file-management commands (@pxref{Files, ,Commands to Specify Files}).
16786 @cindex symbol names
16787 @cindex names of symbols
16788 @cindex quoting names
16789 Occasionally, you may need to refer to symbols that contain unusual
16790 characters, which @value{GDBN} ordinarily treats as word delimiters. The
16791 most frequent case is in referring to static variables in other
16792 source files (@pxref{Variables,,Program Variables}). File names
16793 are recorded in object files as debugging symbols, but @value{GDBN} would
16794 ordinarily parse a typical file name, like @file{foo.c}, as the three words
16795 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
16796 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
16803 looks up the value of @code{x} in the scope of the file @file{foo.c}.
16806 @cindex case-insensitive symbol names
16807 @cindex case sensitivity in symbol names
16808 @kindex set case-sensitive
16809 @item set case-sensitive on
16810 @itemx set case-sensitive off
16811 @itemx set case-sensitive auto
16812 Normally, when @value{GDBN} looks up symbols, it matches their names
16813 with case sensitivity determined by the current source language.
16814 Occasionally, you may wish to control that. The command @code{set
16815 case-sensitive} lets you do that by specifying @code{on} for
16816 case-sensitive matches or @code{off} for case-insensitive ones. If
16817 you specify @code{auto}, case sensitivity is reset to the default
16818 suitable for the source language. The default is case-sensitive
16819 matches for all languages except for Fortran, for which the default is
16820 case-insensitive matches.
16822 @kindex show case-sensitive
16823 @item show case-sensitive
16824 This command shows the current setting of case sensitivity for symbols
16827 @kindex set print type methods
16828 @item set print type methods
16829 @itemx set print type methods on
16830 @itemx set print type methods off
16831 Normally, when @value{GDBN} prints a class, it displays any methods
16832 declared in that class. You can control this behavior either by
16833 passing the appropriate flag to @code{ptype}, or using @command{set
16834 print type methods}. Specifying @code{on} will cause @value{GDBN} to
16835 display the methods; this is the default. Specifying @code{off} will
16836 cause @value{GDBN} to omit the methods.
16838 @kindex show print type methods
16839 @item show print type methods
16840 This command shows the current setting of method display when printing
16843 @kindex set print type typedefs
16844 @item set print type typedefs
16845 @itemx set print type typedefs on
16846 @itemx set print type typedefs off
16848 Normally, when @value{GDBN} prints a class, it displays any typedefs
16849 defined in that class. You can control this behavior either by
16850 passing the appropriate flag to @code{ptype}, or using @command{set
16851 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
16852 display the typedef definitions; this is the default. Specifying
16853 @code{off} will cause @value{GDBN} to omit the typedef definitions.
16854 Note that this controls whether the typedef definition itself is
16855 printed, not whether typedef names are substituted when printing other
16858 @kindex show print type typedefs
16859 @item show print type typedefs
16860 This command shows the current setting of typedef display when
16863 @kindex info address
16864 @cindex address of a symbol
16865 @item info address @var{symbol}
16866 Describe where the data for @var{symbol} is stored. For a register
16867 variable, this says which register it is kept in. For a non-register
16868 local variable, this prints the stack-frame offset at which the variable
16871 Note the contrast with @samp{print &@var{symbol}}, which does not work
16872 at all for a register variable, and for a stack local variable prints
16873 the exact address of the current instantiation of the variable.
16875 @kindex info symbol
16876 @cindex symbol from address
16877 @cindex closest symbol and offset for an address
16878 @item info symbol @var{addr}
16879 Print the name of a symbol which is stored at the address @var{addr}.
16880 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
16881 nearest symbol and an offset from it:
16884 (@value{GDBP}) info symbol 0x54320
16885 _initialize_vx + 396 in section .text
16889 This is the opposite of the @code{info address} command. You can use
16890 it to find out the name of a variable or a function given its address.
16892 For dynamically linked executables, the name of executable or shared
16893 library containing the symbol is also printed:
16896 (@value{GDBP}) info symbol 0x400225
16897 _start + 5 in section .text of /tmp/a.out
16898 (@value{GDBP}) info symbol 0x2aaaac2811cf
16899 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
16904 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
16905 Demangle @var{name}.
16906 If @var{language} is provided it is the name of the language to demangle
16907 @var{name} in. Otherwise @var{name} is demangled in the current language.
16909 The @samp{--} option specifies the end of options,
16910 and is useful when @var{name} begins with a dash.
16912 The parameter @code{demangle-style} specifies how to interpret the kind
16913 of mangling used. @xref{Print Settings}.
16916 @item whatis[/@var{flags}] [@var{arg}]
16917 Print the data type of @var{arg}, which can be either an expression
16918 or a name of a data type. With no argument, print the data type of
16919 @code{$}, the last value in the value history.
16921 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
16922 is not actually evaluated, and any side-effecting operations (such as
16923 assignments or function calls) inside it do not take place.
16925 If @var{arg} is a variable or an expression, @code{whatis} prints its
16926 literal type as it is used in the source code. If the type was
16927 defined using a @code{typedef}, @code{whatis} will @emph{not} print
16928 the data type underlying the @code{typedef}. If the type of the
16929 variable or the expression is a compound data type, such as
16930 @code{struct} or @code{class}, @code{whatis} never prints their
16931 fields or methods. It just prints the @code{struct}/@code{class}
16932 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
16933 such a compound data type, use @code{ptype}.
16935 If @var{arg} is a type name that was defined using @code{typedef},
16936 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
16937 Unrolling means that @code{whatis} will show the underlying type used
16938 in the @code{typedef} declaration of @var{arg}. However, if that
16939 underlying type is also a @code{typedef}, @code{whatis} will not
16942 For C code, the type names may also have the form @samp{class
16943 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
16944 @var{union-tag}} or @samp{enum @var{enum-tag}}.
16946 @var{flags} can be used to modify how the type is displayed.
16947 Available flags are:
16951 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
16952 parameters and typedefs defined in a class when printing the class'
16953 members. The @code{/r} flag disables this.
16956 Do not print methods defined in the class.
16959 Print methods defined in the class. This is the default, but the flag
16960 exists in case you change the default with @command{set print type methods}.
16963 Do not print typedefs defined in the class. Note that this controls
16964 whether the typedef definition itself is printed, not whether typedef
16965 names are substituted when printing other types.
16968 Print typedefs defined in the class. This is the default, but the flag
16969 exists in case you change the default with @command{set print type typedefs}.
16973 @item ptype[/@var{flags}] [@var{arg}]
16974 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
16975 detailed description of the type, instead of just the name of the type.
16976 @xref{Expressions, ,Expressions}.
16978 Contrary to @code{whatis}, @code{ptype} always unrolls any
16979 @code{typedef}s in its argument declaration, whether the argument is
16980 a variable, expression, or a data type. This means that @code{ptype}
16981 of a variable or an expression will not print literally its type as
16982 present in the source code---use @code{whatis} for that. @code{typedef}s at
16983 the pointer or reference targets are also unrolled. Only @code{typedef}s of
16984 fields, methods and inner @code{class typedef}s of @code{struct}s,
16985 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
16987 For example, for this variable declaration:
16990 typedef double real_t;
16991 struct complex @{ real_t real; double imag; @};
16992 typedef struct complex complex_t;
16994 real_t *real_pointer_var;
16998 the two commands give this output:
17002 (@value{GDBP}) whatis var
17004 (@value{GDBP}) ptype var
17005 type = struct complex @{
17009 (@value{GDBP}) whatis complex_t
17010 type = struct complex
17011 (@value{GDBP}) whatis struct complex
17012 type = struct complex
17013 (@value{GDBP}) ptype struct complex
17014 type = struct complex @{
17018 (@value{GDBP}) whatis real_pointer_var
17020 (@value{GDBP}) ptype real_pointer_var
17026 As with @code{whatis}, using @code{ptype} without an argument refers to
17027 the type of @code{$}, the last value in the value history.
17029 @cindex incomplete type
17030 Sometimes, programs use opaque data types or incomplete specifications
17031 of complex data structure. If the debug information included in the
17032 program does not allow @value{GDBN} to display a full declaration of
17033 the data type, it will say @samp{<incomplete type>}. For example,
17034 given these declarations:
17038 struct foo *fooptr;
17042 but no definition for @code{struct foo} itself, @value{GDBN} will say:
17045 (@value{GDBP}) ptype foo
17046 $1 = <incomplete type>
17050 ``Incomplete type'' is C terminology for data types that are not
17051 completely specified.
17054 @item info types @var{regexp}
17056 Print a brief description of all types whose names match the regular
17057 expression @var{regexp} (or all types in your program, if you supply
17058 no argument). Each complete typename is matched as though it were a
17059 complete line; thus, @samp{i type value} gives information on all
17060 types in your program whose names include the string @code{value}, but
17061 @samp{i type ^value$} gives information only on types whose complete
17062 name is @code{value}.
17064 This command differs from @code{ptype} in two ways: first, like
17065 @code{whatis}, it does not print a detailed description; second, it
17066 lists all source files where a type is defined.
17068 @kindex info type-printers
17069 @item info type-printers
17070 Versions of @value{GDBN} that ship with Python scripting enabled may
17071 have ``type printers'' available. When using @command{ptype} or
17072 @command{whatis}, these printers are consulted when the name of a type
17073 is needed. @xref{Type Printing API}, for more information on writing
17076 @code{info type-printers} displays all the available type printers.
17078 @kindex enable type-printer
17079 @kindex disable type-printer
17080 @item enable type-printer @var{name}@dots{}
17081 @item disable type-printer @var{name}@dots{}
17082 These commands can be used to enable or disable type printers.
17085 @cindex local variables
17086 @item info scope @var{location}
17087 List all the variables local to a particular scope. This command
17088 accepts a @var{location} argument---a function name, a source line, or
17089 an address preceded by a @samp{*}, and prints all the variables local
17090 to the scope defined by that location. (@xref{Specify Location}, for
17091 details about supported forms of @var{location}.) For example:
17094 (@value{GDBP}) @b{info scope command_line_handler}
17095 Scope for command_line_handler:
17096 Symbol rl is an argument at stack/frame offset 8, length 4.
17097 Symbol linebuffer is in static storage at address 0x150a18, length 4.
17098 Symbol linelength is in static storage at address 0x150a1c, length 4.
17099 Symbol p is a local variable in register $esi, length 4.
17100 Symbol p1 is a local variable in register $ebx, length 4.
17101 Symbol nline is a local variable in register $edx, length 4.
17102 Symbol repeat is a local variable at frame offset -8, length 4.
17106 This command is especially useful for determining what data to collect
17107 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
17110 @kindex info source
17112 Show information about the current source file---that is, the source file for
17113 the function containing the current point of execution:
17116 the name of the source file, and the directory containing it,
17118 the directory it was compiled in,
17120 its length, in lines,
17122 which programming language it is written in,
17124 if the debug information provides it, the program that compiled the file
17125 (which may include, e.g., the compiler version and command line arguments),
17127 whether the executable includes debugging information for that file, and
17128 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
17130 whether the debugging information includes information about
17131 preprocessor macros.
17135 @kindex info sources
17137 Print the names of all source files in your program for which there is
17138 debugging information, organized into two lists: files whose symbols
17139 have already been read, and files whose symbols will be read when needed.
17141 @kindex info functions
17142 @item info functions
17143 Print the names and data types of all defined functions.
17145 @item info functions @var{regexp}
17146 Print the names and data types of all defined functions
17147 whose names contain a match for regular expression @var{regexp}.
17148 Thus, @samp{info fun step} finds all functions whose names
17149 include @code{step}; @samp{info fun ^step} finds those whose names
17150 start with @code{step}. If a function name contains characters
17151 that conflict with the regular expression language (e.g.@:
17152 @samp{operator*()}), they may be quoted with a backslash.
17154 @kindex info variables
17155 @item info variables
17156 Print the names and data types of all variables that are defined
17157 outside of functions (i.e.@: excluding local variables).
17159 @item info variables @var{regexp}
17160 Print the names and data types of all variables (except for local
17161 variables) whose names contain a match for regular expression
17164 @kindex info classes
17165 @cindex Objective-C, classes and selectors
17167 @itemx info classes @var{regexp}
17168 Display all Objective-C classes in your program, or
17169 (with the @var{regexp} argument) all those matching a particular regular
17172 @kindex info selectors
17173 @item info selectors
17174 @itemx info selectors @var{regexp}
17175 Display all Objective-C selectors in your program, or
17176 (with the @var{regexp} argument) all those matching a particular regular
17180 This was never implemented.
17181 @kindex info methods
17183 @itemx info methods @var{regexp}
17184 The @code{info methods} command permits the user to examine all defined
17185 methods within C@t{++} program, or (with the @var{regexp} argument) a
17186 specific set of methods found in the various C@t{++} classes. Many
17187 C@t{++} classes provide a large number of methods. Thus, the output
17188 from the @code{ptype} command can be overwhelming and hard to use. The
17189 @code{info-methods} command filters the methods, printing only those
17190 which match the regular-expression @var{regexp}.
17193 @cindex opaque data types
17194 @kindex set opaque-type-resolution
17195 @item set opaque-type-resolution on
17196 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
17197 declared as a pointer to a @code{struct}, @code{class}, or
17198 @code{union}---for example, @code{struct MyType *}---that is used in one
17199 source file although the full declaration of @code{struct MyType} is in
17200 another source file. The default is on.
17202 A change in the setting of this subcommand will not take effect until
17203 the next time symbols for a file are loaded.
17205 @item set opaque-type-resolution off
17206 Tell @value{GDBN} not to resolve opaque types. In this case, the type
17207 is printed as follows:
17209 @{<no data fields>@}
17212 @kindex show opaque-type-resolution
17213 @item show opaque-type-resolution
17214 Show whether opaque types are resolved or not.
17216 @kindex set print symbol-loading
17217 @cindex print messages when symbols are loaded
17218 @item set print symbol-loading
17219 @itemx set print symbol-loading full
17220 @itemx set print symbol-loading brief
17221 @itemx set print symbol-loading off
17222 The @code{set print symbol-loading} command allows you to control the
17223 printing of messages when @value{GDBN} loads symbol information.
17224 By default a message is printed for the executable and one for each
17225 shared library, and normally this is what you want. However, when
17226 debugging apps with large numbers of shared libraries these messages
17228 When set to @code{brief} a message is printed for each executable,
17229 and when @value{GDBN} loads a collection of shared libraries at once
17230 it will only print one message regardless of the number of shared
17231 libraries. When set to @code{off} no messages are printed.
17233 @kindex show print symbol-loading
17234 @item show print symbol-loading
17235 Show whether messages will be printed when a @value{GDBN} command
17236 entered from the keyboard causes symbol information to be loaded.
17238 @kindex maint print symbols
17239 @cindex symbol dump
17240 @kindex maint print psymbols
17241 @cindex partial symbol dump
17242 @kindex maint print msymbols
17243 @cindex minimal symbol dump
17244 @item maint print symbols @var{filename}
17245 @itemx maint print psymbols @var{filename}
17246 @itemx maint print msymbols @var{filename}
17247 Write a dump of debugging symbol data into the file @var{filename}.
17248 These commands are used to debug the @value{GDBN} symbol-reading code. Only
17249 symbols with debugging data are included. If you use @samp{maint print
17250 symbols}, @value{GDBN} includes all the symbols for which it has already
17251 collected full details: that is, @var{filename} reflects symbols for
17252 only those files whose symbols @value{GDBN} has read. You can use the
17253 command @code{info sources} to find out which files these are. If you
17254 use @samp{maint print psymbols} instead, the dump shows information about
17255 symbols that @value{GDBN} only knows partially---that is, symbols defined in
17256 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
17257 @samp{maint print msymbols} dumps just the minimal symbol information
17258 required for each object file from which @value{GDBN} has read some symbols.
17259 @xref{Files, ,Commands to Specify Files}, for a discussion of how
17260 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
17262 @kindex maint info symtabs
17263 @kindex maint info psymtabs
17264 @cindex listing @value{GDBN}'s internal symbol tables
17265 @cindex symbol tables, listing @value{GDBN}'s internal
17266 @cindex full symbol tables, listing @value{GDBN}'s internal
17267 @cindex partial symbol tables, listing @value{GDBN}'s internal
17268 @item maint info symtabs @r{[} @var{regexp} @r{]}
17269 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
17271 List the @code{struct symtab} or @code{struct partial_symtab}
17272 structures whose names match @var{regexp}. If @var{regexp} is not
17273 given, list them all. The output includes expressions which you can
17274 copy into a @value{GDBN} debugging this one to examine a particular
17275 structure in more detail. For example:
17278 (@value{GDBP}) maint info psymtabs dwarf2read
17279 @{ objfile /home/gnu/build/gdb/gdb
17280 ((struct objfile *) 0x82e69d0)
17281 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
17282 ((struct partial_symtab *) 0x8474b10)
17285 text addresses 0x814d3c8 -- 0x8158074
17286 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
17287 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
17288 dependencies (none)
17291 (@value{GDBP}) maint info symtabs
17295 We see that there is one partial symbol table whose filename contains
17296 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
17297 and we see that @value{GDBN} has not read in any symtabs yet at all.
17298 If we set a breakpoint on a function, that will cause @value{GDBN} to
17299 read the symtab for the compilation unit containing that function:
17302 (@value{GDBP}) break dwarf2_psymtab_to_symtab
17303 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
17305 (@value{GDBP}) maint info symtabs
17306 @{ objfile /home/gnu/build/gdb/gdb
17307 ((struct objfile *) 0x82e69d0)
17308 @{ symtab /home/gnu/src/gdb/dwarf2read.c
17309 ((struct symtab *) 0x86c1f38)
17312 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
17313 linetable ((struct linetable *) 0x8370fa0)
17314 debugformat DWARF 2
17320 @kindex maint info line-table
17321 @cindex listing @value{GDBN}'s internal line tables
17322 @cindex line tables, listing @value{GDBN}'s internal
17323 @item maint info line-table @r{[} @var{regexp} @r{]}
17325 List the @code{struct linetable} from all @code{struct symtab}
17326 instances whose name matches @var{regexp}. If @var{regexp} is not
17327 given, list the @code{struct linetable} from all @code{struct symtab}.
17329 @kindex maint set symbol-cache-size
17330 @cindex symbol cache size
17331 @item maint set symbol-cache-size @var{size}
17332 Set the size of the symbol cache to @var{size}.
17333 The default size is intended to be good enough for debugging
17334 most applications. This option exists to allow for experimenting
17335 with different sizes.
17337 @kindex maint show symbol-cache-size
17338 @item maint show symbol-cache-size
17339 Show the size of the symbol cache.
17341 @kindex maint print symbol-cache
17342 @cindex symbol cache, printing its contents
17343 @item maint print symbol-cache
17344 Print the contents of the symbol cache.
17345 This is useful when debugging symbol cache issues.
17347 @kindex maint print symbol-cache-statistics
17348 @cindex symbol cache, printing usage statistics
17349 @item maint print symbol-cache-statistics
17350 Print symbol cache usage statistics.
17351 This helps determine how well the cache is being utilized.
17353 @kindex maint flush-symbol-cache
17354 @cindex symbol cache, flushing
17355 @item maint flush-symbol-cache
17356 Flush the contents of the symbol cache, all entries are removed.
17357 This command is useful when debugging the symbol cache.
17358 It is also useful when collecting performance data.
17363 @chapter Altering Execution
17365 Once you think you have found an error in your program, you might want to
17366 find out for certain whether correcting the apparent error would lead to
17367 correct results in the rest of the run. You can find the answer by
17368 experiment, using the @value{GDBN} features for altering execution of the
17371 For example, you can store new values into variables or memory
17372 locations, give your program a signal, restart it at a different
17373 address, or even return prematurely from a function.
17376 * Assignment:: Assignment to variables
17377 * Jumping:: Continuing at a different address
17378 * Signaling:: Giving your program a signal
17379 * Returning:: Returning from a function
17380 * Calling:: Calling your program's functions
17381 * Patching:: Patching your program
17382 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
17386 @section Assignment to Variables
17389 @cindex setting variables
17390 To alter the value of a variable, evaluate an assignment expression.
17391 @xref{Expressions, ,Expressions}. For example,
17398 stores the value 4 into the variable @code{x}, and then prints the
17399 value of the assignment expression (which is 4).
17400 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
17401 information on operators in supported languages.
17403 @kindex set variable
17404 @cindex variables, setting
17405 If you are not interested in seeing the value of the assignment, use the
17406 @code{set} command instead of the @code{print} command. @code{set} is
17407 really the same as @code{print} except that the expression's value is
17408 not printed and is not put in the value history (@pxref{Value History,
17409 ,Value History}). The expression is evaluated only for its effects.
17411 If the beginning of the argument string of the @code{set} command
17412 appears identical to a @code{set} subcommand, use the @code{set
17413 variable} command instead of just @code{set}. This command is identical
17414 to @code{set} except for its lack of subcommands. For example, if your
17415 program has a variable @code{width}, you get an error if you try to set
17416 a new value with just @samp{set width=13}, because @value{GDBN} has the
17417 command @code{set width}:
17420 (@value{GDBP}) whatis width
17422 (@value{GDBP}) p width
17424 (@value{GDBP}) set width=47
17425 Invalid syntax in expression.
17429 The invalid expression, of course, is @samp{=47}. In
17430 order to actually set the program's variable @code{width}, use
17433 (@value{GDBP}) set var width=47
17436 Because the @code{set} command has many subcommands that can conflict
17437 with the names of program variables, it is a good idea to use the
17438 @code{set variable} command instead of just @code{set}. For example, if
17439 your program has a variable @code{g}, you run into problems if you try
17440 to set a new value with just @samp{set g=4}, because @value{GDBN} has
17441 the command @code{set gnutarget}, abbreviated @code{set g}:
17445 (@value{GDBP}) whatis g
17449 (@value{GDBP}) set g=4
17453 The program being debugged has been started already.
17454 Start it from the beginning? (y or n) y
17455 Starting program: /home/smith/cc_progs/a.out
17456 "/home/smith/cc_progs/a.out": can't open to read symbols:
17457 Invalid bfd target.
17458 (@value{GDBP}) show g
17459 The current BFD target is "=4".
17464 The program variable @code{g} did not change, and you silently set the
17465 @code{gnutarget} to an invalid value. In order to set the variable
17469 (@value{GDBP}) set var g=4
17472 @value{GDBN} allows more implicit conversions in assignments than C; you can
17473 freely store an integer value into a pointer variable or vice versa,
17474 and you can convert any structure to any other structure that is the
17475 same length or shorter.
17476 @comment FIXME: how do structs align/pad in these conversions?
17477 @comment /doc@cygnus.com 18dec1990
17479 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
17480 construct to generate a value of specified type at a specified address
17481 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
17482 to memory location @code{0x83040} as an integer (which implies a certain size
17483 and representation in memory), and
17486 set @{int@}0x83040 = 4
17490 stores the value 4 into that memory location.
17493 @section Continuing at a Different Address
17495 Ordinarily, when you continue your program, you do so at the place where
17496 it stopped, with the @code{continue} command. You can instead continue at
17497 an address of your own choosing, with the following commands:
17501 @kindex j @r{(@code{jump})}
17502 @item jump @var{location}
17503 @itemx j @var{location}
17504 Resume execution at @var{location}. Execution stops again immediately
17505 if there is a breakpoint there. @xref{Specify Location}, for a description
17506 of the different forms of @var{location}. It is common
17507 practice to use the @code{tbreak} command in conjunction with
17508 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
17510 The @code{jump} command does not change the current stack frame, or
17511 the stack pointer, or the contents of any memory location or any
17512 register other than the program counter. If @var{location} is in
17513 a different function from the one currently executing, the results may
17514 be bizarre if the two functions expect different patterns of arguments or
17515 of local variables. For this reason, the @code{jump} command requests
17516 confirmation if the specified line is not in the function currently
17517 executing. However, even bizarre results are predictable if you are
17518 well acquainted with the machine-language code of your program.
17521 On many systems, you can get much the same effect as the @code{jump}
17522 command by storing a new value into the register @code{$pc}. The
17523 difference is that this does not start your program running; it only
17524 changes the address of where it @emph{will} run when you continue. For
17532 makes the next @code{continue} command or stepping command execute at
17533 address @code{0x485}, rather than at the address where your program stopped.
17534 @xref{Continuing and Stepping, ,Continuing and Stepping}.
17536 The most common occasion to use the @code{jump} command is to back
17537 up---perhaps with more breakpoints set---over a portion of a program
17538 that has already executed, in order to examine its execution in more
17543 @section Giving your Program a Signal
17544 @cindex deliver a signal to a program
17548 @item signal @var{signal}
17549 Resume execution where your program is stopped, but immediately give it the
17550 signal @var{signal}. The @var{signal} can be the name or the number of a
17551 signal. For example, on many systems @code{signal 2} and @code{signal
17552 SIGINT} are both ways of sending an interrupt signal.
17554 Alternatively, if @var{signal} is zero, continue execution without
17555 giving a signal. This is useful when your program stopped on account of
17556 a signal and would ordinarily see the signal when resumed with the
17557 @code{continue} command; @samp{signal 0} causes it to resume without a
17560 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
17561 delivered to the currently selected thread, not the thread that last
17562 reported a stop. This includes the situation where a thread was
17563 stopped due to a signal. So if you want to continue execution
17564 suppressing the signal that stopped a thread, you should select that
17565 same thread before issuing the @samp{signal 0} command. If you issue
17566 the @samp{signal 0} command with another thread as the selected one,
17567 @value{GDBN} detects that and asks for confirmation.
17569 Invoking the @code{signal} command is not the same as invoking the
17570 @code{kill} utility from the shell. Sending a signal with @code{kill}
17571 causes @value{GDBN} to decide what to do with the signal depending on
17572 the signal handling tables (@pxref{Signals}). The @code{signal} command
17573 passes the signal directly to your program.
17575 @code{signal} does not repeat when you press @key{RET} a second time
17576 after executing the command.
17578 @kindex queue-signal
17579 @item queue-signal @var{signal}
17580 Queue @var{signal} to be delivered immediately to the current thread
17581 when execution of the thread resumes. The @var{signal} can be the name or
17582 the number of a signal. For example, on many systems @code{signal 2} and
17583 @code{signal SIGINT} are both ways of sending an interrupt signal.
17584 The handling of the signal must be set to pass the signal to the program,
17585 otherwise @value{GDBN} will report an error.
17586 You can control the handling of signals from @value{GDBN} with the
17587 @code{handle} command (@pxref{Signals}).
17589 Alternatively, if @var{signal} is zero, any currently queued signal
17590 for the current thread is discarded and when execution resumes no signal
17591 will be delivered. This is useful when your program stopped on account
17592 of a signal and would ordinarily see the signal when resumed with the
17593 @code{continue} command.
17595 This command differs from the @code{signal} command in that the signal
17596 is just queued, execution is not resumed. And @code{queue-signal} cannot
17597 be used to pass a signal whose handling state has been set to @code{nopass}
17602 @xref{stepping into signal handlers}, for information on how stepping
17603 commands behave when the thread has a signal queued.
17606 @section Returning from a Function
17609 @cindex returning from a function
17612 @itemx return @var{expression}
17613 You can cancel execution of a function call with the @code{return}
17614 command. If you give an
17615 @var{expression} argument, its value is used as the function's return
17619 When you use @code{return}, @value{GDBN} discards the selected stack frame
17620 (and all frames within it). You can think of this as making the
17621 discarded frame return prematurely. If you wish to specify a value to
17622 be returned, give that value as the argument to @code{return}.
17624 This pops the selected stack frame (@pxref{Selection, ,Selecting a
17625 Frame}), and any other frames inside of it, leaving its caller as the
17626 innermost remaining frame. That frame becomes selected. The
17627 specified value is stored in the registers used for returning values
17630 The @code{return} command does not resume execution; it leaves the
17631 program stopped in the state that would exist if the function had just
17632 returned. In contrast, the @code{finish} command (@pxref{Continuing
17633 and Stepping, ,Continuing and Stepping}) resumes execution until the
17634 selected stack frame returns naturally.
17636 @value{GDBN} needs to know how the @var{expression} argument should be set for
17637 the inferior. The concrete registers assignment depends on the OS ABI and the
17638 type being returned by the selected stack frame. For example it is common for
17639 OS ABI to return floating point values in FPU registers while integer values in
17640 CPU registers. Still some ABIs return even floating point values in CPU
17641 registers. Larger integer widths (such as @code{long long int}) also have
17642 specific placement rules. @value{GDBN} already knows the OS ABI from its
17643 current target so it needs to find out also the type being returned to make the
17644 assignment into the right register(s).
17646 Normally, the selected stack frame has debug info. @value{GDBN} will always
17647 use the debug info instead of the implicit type of @var{expression} when the
17648 debug info is available. For example, if you type @kbd{return -1}, and the
17649 function in the current stack frame is declared to return a @code{long long
17650 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
17651 into a @code{long long int}:
17654 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
17656 (@value{GDBP}) return -1
17657 Make func return now? (y or n) y
17658 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
17659 43 printf ("result=%lld\n", func ());
17663 However, if the selected stack frame does not have a debug info, e.g., if the
17664 function was compiled without debug info, @value{GDBN} has to find out the type
17665 to return from user. Specifying a different type by mistake may set the value
17666 in different inferior registers than the caller code expects. For example,
17667 typing @kbd{return -1} with its implicit type @code{int} would set only a part
17668 of a @code{long long int} result for a debug info less function (on 32-bit
17669 architectures). Therefore the user is required to specify the return type by
17670 an appropriate cast explicitly:
17673 Breakpoint 2, 0x0040050b in func ()
17674 (@value{GDBP}) return -1
17675 Return value type not available for selected stack frame.
17676 Please use an explicit cast of the value to return.
17677 (@value{GDBP}) return (long long int) -1
17678 Make selected stack frame return now? (y or n) y
17679 #0 0x00400526 in main ()
17684 @section Calling Program Functions
17687 @cindex calling functions
17688 @cindex inferior functions, calling
17689 @item print @var{expr}
17690 Evaluate the expression @var{expr} and display the resulting value.
17691 The expression may include calls to functions in the program being
17695 @item call @var{expr}
17696 Evaluate the expression @var{expr} without displaying @code{void}
17699 You can use this variant of the @code{print} command if you want to
17700 execute a function from your program that does not return anything
17701 (a.k.a.@: @dfn{a void function}), but without cluttering the output
17702 with @code{void} returned values that @value{GDBN} will otherwise
17703 print. If the result is not void, it is printed and saved in the
17707 It is possible for the function you call via the @code{print} or
17708 @code{call} command to generate a signal (e.g., if there's a bug in
17709 the function, or if you passed it incorrect arguments). What happens
17710 in that case is controlled by the @code{set unwindonsignal} command.
17712 Similarly, with a C@t{++} program it is possible for the function you
17713 call via the @code{print} or @code{call} command to generate an
17714 exception that is not handled due to the constraints of the dummy
17715 frame. In this case, any exception that is raised in the frame, but has
17716 an out-of-frame exception handler will not be found. GDB builds a
17717 dummy-frame for the inferior function call, and the unwinder cannot
17718 seek for exception handlers outside of this dummy-frame. What happens
17719 in that case is controlled by the
17720 @code{set unwind-on-terminating-exception} command.
17723 @item set unwindonsignal
17724 @kindex set unwindonsignal
17725 @cindex unwind stack in called functions
17726 @cindex call dummy stack unwinding
17727 Set unwinding of the stack if a signal is received while in a function
17728 that @value{GDBN} called in the program being debugged. If set to on,
17729 @value{GDBN} unwinds the stack it created for the call and restores
17730 the context to what it was before the call. If set to off (the
17731 default), @value{GDBN} stops in the frame where the signal was
17734 @item show unwindonsignal
17735 @kindex show unwindonsignal
17736 Show the current setting of stack unwinding in the functions called by
17739 @item set unwind-on-terminating-exception
17740 @kindex set unwind-on-terminating-exception
17741 @cindex unwind stack in called functions with unhandled exceptions
17742 @cindex call dummy stack unwinding on unhandled exception.
17743 Set unwinding of the stack if a C@t{++} exception is raised, but left
17744 unhandled while in a function that @value{GDBN} called in the program being
17745 debugged. If set to on (the default), @value{GDBN} unwinds the stack
17746 it created for the call and restores the context to what it was before
17747 the call. If set to off, @value{GDBN} the exception is delivered to
17748 the default C@t{++} exception handler and the inferior terminated.
17750 @item show unwind-on-terminating-exception
17751 @kindex show unwind-on-terminating-exception
17752 Show the current setting of stack unwinding in the functions called by
17757 @cindex weak alias functions
17758 Sometimes, a function you wish to call is actually a @dfn{weak alias}
17759 for another function. In such case, @value{GDBN} might not pick up
17760 the type information, including the types of the function arguments,
17761 which causes @value{GDBN} to call the inferior function incorrectly.
17762 As a result, the called function will function erroneously and may
17763 even crash. A solution to that is to use the name of the aliased
17767 @section Patching Programs
17769 @cindex patching binaries
17770 @cindex writing into executables
17771 @cindex writing into corefiles
17773 By default, @value{GDBN} opens the file containing your program's
17774 executable code (or the corefile) read-only. This prevents accidental
17775 alterations to machine code; but it also prevents you from intentionally
17776 patching your program's binary.
17778 If you'd like to be able to patch the binary, you can specify that
17779 explicitly with the @code{set write} command. For example, you might
17780 want to turn on internal debugging flags, or even to make emergency
17786 @itemx set write off
17787 If you specify @samp{set write on}, @value{GDBN} opens executable and
17788 core files for both reading and writing; if you specify @kbd{set write
17789 off} (the default), @value{GDBN} opens them read-only.
17791 If you have already loaded a file, you must load it again (using the
17792 @code{exec-file} or @code{core-file} command) after changing @code{set
17793 write}, for your new setting to take effect.
17797 Display whether executable files and core files are opened for writing
17798 as well as reading.
17801 @node Compiling and Injecting Code
17802 @section Compiling and injecting code in @value{GDBN}
17803 @cindex injecting code
17804 @cindex writing into executables
17805 @cindex compiling code
17807 @value{GDBN} supports on-demand compilation and code injection into
17808 programs running under @value{GDBN}. GCC 5.0 or higher built with
17809 @file{libcc1.so} must be installed for this functionality to be enabled.
17810 This functionality is implemented with the following commands.
17813 @kindex compile code
17814 @item compile code @var{source-code}
17815 @itemx compile code -raw @var{--} @var{source-code}
17816 Compile @var{source-code} with the compiler language found as the current
17817 language in @value{GDBN} (@pxref{Languages}). If compilation and
17818 injection is not supported with the current language specified in
17819 @value{GDBN}, or the compiler does not support this feature, an error
17820 message will be printed. If @var{source-code} compiles and links
17821 successfully, @value{GDBN} will load the object-code emitted,
17822 and execute it within the context of the currently selected inferior.
17823 It is important to note that the compiled code is executed immediately.
17824 After execution, the compiled code is removed from @value{GDBN} and any
17825 new types or variables you have defined will be deleted.
17827 The command allows you to specify @var{source-code} in two ways.
17828 The simplest method is to provide a single line of code to the command.
17832 compile code printf ("hello world\n");
17835 If you specify options on the command line as well as source code, they
17836 may conflict. The @samp{--} delimiter can be used to separate options
17837 from actual source code. E.g.:
17840 compile code -r -- printf ("hello world\n");
17843 Alternatively you can enter source code as multiple lines of text. To
17844 enter this mode, invoke the @samp{compile code} command without any text
17845 following the command. This will start the multiple-line editor and
17846 allow you to type as many lines of source code as required. When you
17847 have completed typing, enter @samp{end} on its own line to exit the
17852 >printf ("hello\n");
17853 >printf ("world\n");
17857 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
17858 provided @var{source-code} in a callable scope. In this case, you must
17859 specify the entry point of the code by defining a function named
17860 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
17861 inferior. Using @samp{-raw} option may be needed for example when
17862 @var{source-code} requires @samp{#include} lines which may conflict with
17863 inferior symbols otherwise.
17865 @kindex compile file
17866 @item compile file @var{filename}
17867 @itemx compile file -raw @var{filename}
17868 Like @code{compile code}, but take the source code from @var{filename}.
17871 compile file /home/user/example.c
17876 @item compile print @var{expr}
17877 @itemx compile print /@var{f} @var{expr}
17878 Compile and execute @var{expr} with the compiler language found as the
17879 current language in @value{GDBN} (@pxref{Languages}). By default the
17880 value of @var{expr} is printed in a format appropriate to its data type;
17881 you can choose a different format by specifying @samp{/@var{f}}, where
17882 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
17885 @item compile print
17886 @itemx compile print /@var{f}
17887 @cindex reprint the last value
17888 Alternatively you can enter the expression (source code producing it) as
17889 multiple lines of text. To enter this mode, invoke the @samp{compile print}
17890 command without any text following the command. This will start the
17891 multiple-line editor.
17895 The process of compiling and injecting the code can be inspected using:
17898 @anchor{set debug compile}
17899 @item set debug compile
17900 @cindex compile command debugging info
17901 Turns on or off display of @value{GDBN} process of compiling and
17902 injecting the code. The default is off.
17904 @item show debug compile
17905 Displays the current state of displaying @value{GDBN} process of
17906 compiling and injecting the code.
17909 @subsection Compilation options for the @code{compile} command
17911 @value{GDBN} needs to specify the right compilation options for the code
17912 to be injected, in part to make its ABI compatible with the inferior
17913 and in part to make the injected code compatible with @value{GDBN}'s
17917 The options used, in increasing precedence:
17920 @item target architecture and OS options (@code{gdbarch})
17921 These options depend on target processor type and target operating
17922 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
17923 (@code{-m64}) compilation option.
17925 @item compilation options recorded in the target
17926 @value{NGCC} (since version 4.7) stores the options used for compilation
17927 into @code{DW_AT_producer} part of DWARF debugging information according
17928 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
17929 explicitly specify @code{-g} during inferior compilation otherwise
17930 @value{NGCC} produces no DWARF. This feature is only relevant for
17931 platforms where @code{-g} produces DWARF by default, otherwise one may
17932 try to enforce DWARF by using @code{-gdwarf-4}.
17934 @item compilation options set by @code{set compile-args}
17938 You can override compilation options using the following command:
17941 @item set compile-args
17942 @cindex compile command options override
17943 Set compilation options used for compiling and injecting code with the
17944 @code{compile} commands. These options override any conflicting ones
17945 from the target architecture and/or options stored during inferior
17948 @item show compile-args
17949 Displays the current state of compilation options override.
17950 This does not show all the options actually used during compilation,
17951 use @ref{set debug compile} for that.
17954 @subsection Caveats when using the @code{compile} command
17956 There are a few caveats to keep in mind when using the @code{compile}
17957 command. As the caveats are different per language, the table below
17958 highlights specific issues on a per language basis.
17961 @item C code examples and caveats
17962 When the language in @value{GDBN} is set to @samp{C}, the compiler will
17963 attempt to compile the source code with a @samp{C} compiler. The source
17964 code provided to the @code{compile} command will have much the same
17965 access to variables and types as it normally would if it were part of
17966 the program currently being debugged in @value{GDBN}.
17968 Below is a sample program that forms the basis of the examples that
17969 follow. This program has been compiled and loaded into @value{GDBN},
17970 much like any other normal debugging session.
17973 void function1 (void)
17976 printf ("function 1\n");
17979 void function2 (void)
17994 For the purposes of the examples in this section, the program above has
17995 been compiled, loaded into @value{GDBN}, stopped at the function
17996 @code{main}, and @value{GDBN} is awaiting input from the user.
17998 To access variables and types for any program in @value{GDBN}, the
17999 program must be compiled and packaged with debug information. The
18000 @code{compile} command is not an exception to this rule. Without debug
18001 information, you can still use the @code{compile} command, but you will
18002 be very limited in what variables and types you can access.
18004 So with that in mind, the example above has been compiled with debug
18005 information enabled. The @code{compile} command will have access to
18006 all variables and types (except those that may have been optimized
18007 out). Currently, as @value{GDBN} has stopped the program in the
18008 @code{main} function, the @code{compile} command would have access to
18009 the variable @code{k}. You could invoke the @code{compile} command
18010 and type some source code to set the value of @code{k}. You can also
18011 read it, or do anything with that variable you would normally do in
18012 @code{C}. Be aware that changes to inferior variables in the
18013 @code{compile} command are persistent. In the following example:
18016 compile code k = 3;
18020 the variable @code{k} is now 3. It will retain that value until
18021 something else in the example program changes it, or another
18022 @code{compile} command changes it.
18024 Normal scope and access rules apply to source code compiled and
18025 injected by the @code{compile} command. In the example, the variables
18026 @code{j} and @code{k} are not accessible yet, because the program is
18027 currently stopped in the @code{main} function, where these variables
18028 are not in scope. Therefore, the following command
18031 compile code j = 3;
18035 will result in a compilation error message.
18037 Once the program is continued, execution will bring these variables in
18038 scope, and they will become accessible; then the code you specify via
18039 the @code{compile} command will be able to access them.
18041 You can create variables and types with the @code{compile} command as
18042 part of your source code. Variables and types that are created as part
18043 of the @code{compile} command are not visible to the rest of the program for
18044 the duration of its run. This example is valid:
18047 compile code int ff = 5; printf ("ff is %d\n", ff);
18050 However, if you were to type the following into @value{GDBN} after that
18051 command has completed:
18054 compile code printf ("ff is %d\n'', ff);
18058 a compiler error would be raised as the variable @code{ff} no longer
18059 exists. Object code generated and injected by the @code{compile}
18060 command is removed when its execution ends. Caution is advised
18061 when assigning to program variables values of variables created by the
18062 code submitted to the @code{compile} command. This example is valid:
18065 compile code int ff = 5; k = ff;
18068 The value of the variable @code{ff} is assigned to @code{k}. The variable
18069 @code{k} does not require the existence of @code{ff} to maintain the value
18070 it has been assigned. However, pointers require particular care in
18071 assignment. If the source code compiled with the @code{compile} command
18072 changed the address of a pointer in the example program, perhaps to a
18073 variable created in the @code{compile} command, that pointer would point
18074 to an invalid location when the command exits. The following example
18075 would likely cause issues with your debugged program:
18078 compile code int ff = 5; p = &ff;
18081 In this example, @code{p} would point to @code{ff} when the
18082 @code{compile} command is executing the source code provided to it.
18083 However, as variables in the (example) program persist with their
18084 assigned values, the variable @code{p} would point to an invalid
18085 location when the command exists. A general rule should be followed
18086 in that you should either assign @code{NULL} to any assigned pointers,
18087 or restore a valid location to the pointer before the command exits.
18089 Similar caution must be exercised with any structs, unions, and typedefs
18090 defined in @code{compile} command. Types defined in the @code{compile}
18091 command will no longer be available in the next @code{compile} command.
18092 Therefore, if you cast a variable to a type defined in the
18093 @code{compile} command, care must be taken to ensure that any future
18094 need to resolve the type can be achieved.
18097 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
18098 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
18099 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
18100 Compilation failed.
18101 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
18105 Variables that have been optimized away by the compiler are not
18106 accessible to the code submitted to the @code{compile} command.
18107 Access to those variables will generate a compiler error which @value{GDBN}
18108 will print to the console.
18111 @subsection Compiler search for the @code{compile} command
18113 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged which
18114 may not be obvious for remote targets of different architecture than where
18115 @value{GDBN} is running. Environment variable @code{PATH} (@code{PATH} from
18116 shell that executed @value{GDBN}, not the one set by @value{GDBN}
18117 command @code{set environment}). @xref{Environment}. @code{PATH} on
18118 @value{GDBN} host is searched for @value{NGCC} binary matching the
18119 target architecture and operating system.
18121 Specifically @code{PATH} is searched for binaries matching regular expression
18122 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
18123 debugged. @var{arch} is processor name --- multiarch is supported, so for
18124 example both @code{i386} and @code{x86_64} targets look for pattern
18125 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
18126 for pattern @code{s390x?}. @var{os} is currently supported only for
18127 pattern @code{linux(-gnu)?}.
18130 @chapter @value{GDBN} Files
18132 @value{GDBN} needs to know the file name of the program to be debugged,
18133 both in order to read its symbol table and in order to start your
18134 program. To debug a core dump of a previous run, you must also tell
18135 @value{GDBN} the name of the core dump file.
18138 * Files:: Commands to specify files
18139 * File Caching:: Information about @value{GDBN}'s file caching
18140 * Separate Debug Files:: Debugging information in separate files
18141 * MiniDebugInfo:: Debugging information in a special section
18142 * Index Files:: Index files speed up GDB
18143 * Symbol Errors:: Errors reading symbol files
18144 * Data Files:: GDB data files
18148 @section Commands to Specify Files
18150 @cindex symbol table
18151 @cindex core dump file
18153 You may want to specify executable and core dump file names. The usual
18154 way to do this is at start-up time, using the arguments to
18155 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
18156 Out of @value{GDBN}}).
18158 Occasionally it is necessary to change to a different file during a
18159 @value{GDBN} session. Or you may run @value{GDBN} and forget to
18160 specify a file you want to use. Or you are debugging a remote target
18161 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
18162 Program}). In these situations the @value{GDBN} commands to specify
18163 new files are useful.
18166 @cindex executable file
18168 @item file @var{filename}
18169 Use @var{filename} as the program to be debugged. It is read for its
18170 symbols and for the contents of pure memory. It is also the program
18171 executed when you use the @code{run} command. If you do not specify a
18172 directory and the file is not found in the @value{GDBN} working directory,
18173 @value{GDBN} uses the environment variable @code{PATH} as a list of
18174 directories to search, just as the shell does when looking for a program
18175 to run. You can change the value of this variable, for both @value{GDBN}
18176 and your program, using the @code{path} command.
18178 @cindex unlinked object files
18179 @cindex patching object files
18180 You can load unlinked object @file{.o} files into @value{GDBN} using
18181 the @code{file} command. You will not be able to ``run'' an object
18182 file, but you can disassemble functions and inspect variables. Also,
18183 if the underlying BFD functionality supports it, you could use
18184 @kbd{gdb -write} to patch object files using this technique. Note
18185 that @value{GDBN} can neither interpret nor modify relocations in this
18186 case, so branches and some initialized variables will appear to go to
18187 the wrong place. But this feature is still handy from time to time.
18190 @code{file} with no argument makes @value{GDBN} discard any information it
18191 has on both executable file and the symbol table.
18194 @item exec-file @r{[} @var{filename} @r{]}
18195 Specify that the program to be run (but not the symbol table) is found
18196 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
18197 if necessary to locate your program. Omitting @var{filename} means to
18198 discard information on the executable file.
18200 @kindex symbol-file
18201 @item symbol-file @r{[} @var{filename} @r{]}
18202 Read symbol table information from file @var{filename}. @code{PATH} is
18203 searched when necessary. Use the @code{file} command to get both symbol
18204 table and program to run from the same file.
18206 @code{symbol-file} with no argument clears out @value{GDBN} information on your
18207 program's symbol table.
18209 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
18210 some breakpoints and auto-display expressions. This is because they may
18211 contain pointers to the internal data recording symbols and data types,
18212 which are part of the old symbol table data being discarded inside
18215 @code{symbol-file} does not repeat if you press @key{RET} again after
18218 When @value{GDBN} is configured for a particular environment, it
18219 understands debugging information in whatever format is the standard
18220 generated for that environment; you may use either a @sc{gnu} compiler, or
18221 other compilers that adhere to the local conventions.
18222 Best results are usually obtained from @sc{gnu} compilers; for example,
18223 using @code{@value{NGCC}} you can generate debugging information for
18226 For most kinds of object files, with the exception of old SVR3 systems
18227 using COFF, the @code{symbol-file} command does not normally read the
18228 symbol table in full right away. Instead, it scans the symbol table
18229 quickly to find which source files and which symbols are present. The
18230 details are read later, one source file at a time, as they are needed.
18232 The purpose of this two-stage reading strategy is to make @value{GDBN}
18233 start up faster. For the most part, it is invisible except for
18234 occasional pauses while the symbol table details for a particular source
18235 file are being read. (The @code{set verbose} command can turn these
18236 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
18237 Warnings and Messages}.)
18239 We have not implemented the two-stage strategy for COFF yet. When the
18240 symbol table is stored in COFF format, @code{symbol-file} reads the
18241 symbol table data in full right away. Note that ``stabs-in-COFF''
18242 still does the two-stage strategy, since the debug info is actually
18246 @cindex reading symbols immediately
18247 @cindex symbols, reading immediately
18248 @item symbol-file @r{[} -readnow @r{]} @var{filename}
18249 @itemx file @r{[} -readnow @r{]} @var{filename}
18250 You can override the @value{GDBN} two-stage strategy for reading symbol
18251 tables by using the @samp{-readnow} option with any of the commands that
18252 load symbol table information, if you want to be sure @value{GDBN} has the
18253 entire symbol table available.
18255 @c FIXME: for now no mention of directories, since this seems to be in
18256 @c flux. 13mar1992 status is that in theory GDB would look either in
18257 @c current dir or in same dir as myprog; but issues like competing
18258 @c GDB's, or clutter in system dirs, mean that in practice right now
18259 @c only current dir is used. FFish says maybe a special GDB hierarchy
18260 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
18264 @item core-file @r{[}@var{filename}@r{]}
18266 Specify the whereabouts of a core dump file to be used as the ``contents
18267 of memory''. Traditionally, core files contain only some parts of the
18268 address space of the process that generated them; @value{GDBN} can access the
18269 executable file itself for other parts.
18271 @code{core-file} with no argument specifies that no core file is
18274 Note that the core file is ignored when your program is actually running
18275 under @value{GDBN}. So, if you have been running your program and you
18276 wish to debug a core file instead, you must kill the subprocess in which
18277 the program is running. To do this, use the @code{kill} command
18278 (@pxref{Kill Process, ,Killing the Child Process}).
18280 @kindex add-symbol-file
18281 @cindex dynamic linking
18282 @item add-symbol-file @var{filename} @var{address}
18283 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
18284 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
18285 The @code{add-symbol-file} command reads additional symbol table
18286 information from the file @var{filename}. You would use this command
18287 when @var{filename} has been dynamically loaded (by some other means)
18288 into the program that is running. The @var{address} should give the memory
18289 address at which the file has been loaded; @value{GDBN} cannot figure
18290 this out for itself. You can additionally specify an arbitrary number
18291 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
18292 section name and base address for that section. You can specify any
18293 @var{address} as an expression.
18295 The symbol table of the file @var{filename} is added to the symbol table
18296 originally read with the @code{symbol-file} command. You can use the
18297 @code{add-symbol-file} command any number of times; the new symbol data
18298 thus read is kept in addition to the old.
18300 Changes can be reverted using the command @code{remove-symbol-file}.
18302 @cindex relocatable object files, reading symbols from
18303 @cindex object files, relocatable, reading symbols from
18304 @cindex reading symbols from relocatable object files
18305 @cindex symbols, reading from relocatable object files
18306 @cindex @file{.o} files, reading symbols from
18307 Although @var{filename} is typically a shared library file, an
18308 executable file, or some other object file which has been fully
18309 relocated for loading into a process, you can also load symbolic
18310 information from relocatable @file{.o} files, as long as:
18314 the file's symbolic information refers only to linker symbols defined in
18315 that file, not to symbols defined by other object files,
18317 every section the file's symbolic information refers to has actually
18318 been loaded into the inferior, as it appears in the file, and
18320 you can determine the address at which every section was loaded, and
18321 provide these to the @code{add-symbol-file} command.
18325 Some embedded operating systems, like Sun Chorus and VxWorks, can load
18326 relocatable files into an already running program; such systems
18327 typically make the requirements above easy to meet. However, it's
18328 important to recognize that many native systems use complex link
18329 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
18330 assembly, for example) that make the requirements difficult to meet. In
18331 general, one cannot assume that using @code{add-symbol-file} to read a
18332 relocatable object file's symbolic information will have the same effect
18333 as linking the relocatable object file into the program in the normal
18336 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
18338 @kindex remove-symbol-file
18339 @item remove-symbol-file @var{filename}
18340 @item remove-symbol-file -a @var{address}
18341 Remove a symbol file added via the @code{add-symbol-file} command. The
18342 file to remove can be identified by its @var{filename} or by an @var{address}
18343 that lies within the boundaries of this symbol file in memory. Example:
18346 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
18347 add symbol table from file "/home/user/gdb/mylib.so" at
18348 .text_addr = 0x7ffff7ff9480
18350 Reading symbols from /home/user/gdb/mylib.so...done.
18351 (gdb) remove-symbol-file -a 0x7ffff7ff9480
18352 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
18357 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
18359 @kindex add-symbol-file-from-memory
18360 @cindex @code{syscall DSO}
18361 @cindex load symbols from memory
18362 @item add-symbol-file-from-memory @var{address}
18363 Load symbols from the given @var{address} in a dynamically loaded
18364 object file whose image is mapped directly into the inferior's memory.
18365 For example, the Linux kernel maps a @code{syscall DSO} into each
18366 process's address space; this DSO provides kernel-specific code for
18367 some system calls. The argument can be any expression whose
18368 evaluation yields the address of the file's shared object file header.
18369 For this command to work, you must have used @code{symbol-file} or
18370 @code{exec-file} commands in advance.
18373 @item section @var{section} @var{addr}
18374 The @code{section} command changes the base address of the named
18375 @var{section} of the exec file to @var{addr}. This can be used if the
18376 exec file does not contain section addresses, (such as in the
18377 @code{a.out} format), or when the addresses specified in the file
18378 itself are wrong. Each section must be changed separately. The
18379 @code{info files} command, described below, lists all the sections and
18383 @kindex info target
18386 @code{info files} and @code{info target} are synonymous; both print the
18387 current target (@pxref{Targets, ,Specifying a Debugging Target}),
18388 including the names of the executable and core dump files currently in
18389 use by @value{GDBN}, and the files from which symbols were loaded. The
18390 command @code{help target} lists all possible targets rather than
18393 @kindex maint info sections
18394 @item maint info sections
18395 Another command that can give you extra information about program sections
18396 is @code{maint info sections}. In addition to the section information
18397 displayed by @code{info files}, this command displays the flags and file
18398 offset of each section in the executable and core dump files. In addition,
18399 @code{maint info sections} provides the following command options (which
18400 may be arbitrarily combined):
18404 Display sections for all loaded object files, including shared libraries.
18405 @item @var{sections}
18406 Display info only for named @var{sections}.
18407 @item @var{section-flags}
18408 Display info only for sections for which @var{section-flags} are true.
18409 The section flags that @value{GDBN} currently knows about are:
18412 Section will have space allocated in the process when loaded.
18413 Set for all sections except those containing debug information.
18415 Section will be loaded from the file into the child process memory.
18416 Set for pre-initialized code and data, clear for @code{.bss} sections.
18418 Section needs to be relocated before loading.
18420 Section cannot be modified by the child process.
18422 Section contains executable code only.
18424 Section contains data only (no executable code).
18426 Section will reside in ROM.
18428 Section contains data for constructor/destructor lists.
18430 Section is not empty.
18432 An instruction to the linker to not output the section.
18433 @item COFF_SHARED_LIBRARY
18434 A notification to the linker that the section contains
18435 COFF shared library information.
18437 Section contains common symbols.
18440 @kindex set trust-readonly-sections
18441 @cindex read-only sections
18442 @item set trust-readonly-sections on
18443 Tell @value{GDBN} that readonly sections in your object file
18444 really are read-only (i.e.@: that their contents will not change).
18445 In that case, @value{GDBN} can fetch values from these sections
18446 out of the object file, rather than from the target program.
18447 For some targets (notably embedded ones), this can be a significant
18448 enhancement to debugging performance.
18450 The default is off.
18452 @item set trust-readonly-sections off
18453 Tell @value{GDBN} not to trust readonly sections. This means that
18454 the contents of the section might change while the program is running,
18455 and must therefore be fetched from the target when needed.
18457 @item show trust-readonly-sections
18458 Show the current setting of trusting readonly sections.
18461 All file-specifying commands allow both absolute and relative file names
18462 as arguments. @value{GDBN} always converts the file name to an absolute file
18463 name and remembers it that way.
18465 @cindex shared libraries
18466 @anchor{Shared Libraries}
18467 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
18468 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
18469 DSBT (TIC6X) shared libraries.
18471 On MS-Windows @value{GDBN} must be linked with the Expat library to support
18472 shared libraries. @xref{Expat}.
18474 @value{GDBN} automatically loads symbol definitions from shared libraries
18475 when you use the @code{run} command, or when you examine a core file.
18476 (Before you issue the @code{run} command, @value{GDBN} does not understand
18477 references to a function in a shared library, however---unless you are
18478 debugging a core file).
18480 @c FIXME: some @value{GDBN} release may permit some refs to undef
18481 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
18482 @c FIXME...lib; check this from time to time when updating manual
18484 There are times, however, when you may wish to not automatically load
18485 symbol definitions from shared libraries, such as when they are
18486 particularly large or there are many of them.
18488 To control the automatic loading of shared library symbols, use the
18492 @kindex set auto-solib-add
18493 @item set auto-solib-add @var{mode}
18494 If @var{mode} is @code{on}, symbols from all shared object libraries
18495 will be loaded automatically when the inferior begins execution, you
18496 attach to an independently started inferior, or when the dynamic linker
18497 informs @value{GDBN} that a new library has been loaded. If @var{mode}
18498 is @code{off}, symbols must be loaded manually, using the
18499 @code{sharedlibrary} command. The default value is @code{on}.
18501 @cindex memory used for symbol tables
18502 If your program uses lots of shared libraries with debug info that
18503 takes large amounts of memory, you can decrease the @value{GDBN}
18504 memory footprint by preventing it from automatically loading the
18505 symbols from shared libraries. To that end, type @kbd{set
18506 auto-solib-add off} before running the inferior, then load each
18507 library whose debug symbols you do need with @kbd{sharedlibrary
18508 @var{regexp}}, where @var{regexp} is a regular expression that matches
18509 the libraries whose symbols you want to be loaded.
18511 @kindex show auto-solib-add
18512 @item show auto-solib-add
18513 Display the current autoloading mode.
18516 @cindex load shared library
18517 To explicitly load shared library symbols, use the @code{sharedlibrary}
18521 @kindex info sharedlibrary
18523 @item info share @var{regex}
18524 @itemx info sharedlibrary @var{regex}
18525 Print the names of the shared libraries which are currently loaded
18526 that match @var{regex}. If @var{regex} is omitted then print
18527 all shared libraries that are loaded.
18530 @item info dll @var{regex}
18531 This is an alias of @code{info sharedlibrary}.
18533 @kindex sharedlibrary
18535 @item sharedlibrary @var{regex}
18536 @itemx share @var{regex}
18537 Load shared object library symbols for files matching a
18538 Unix regular expression.
18539 As with files loaded automatically, it only loads shared libraries
18540 required by your program for a core file or after typing @code{run}. If
18541 @var{regex} is omitted all shared libraries required by your program are
18544 @item nosharedlibrary
18545 @kindex nosharedlibrary
18546 @cindex unload symbols from shared libraries
18547 Unload all shared object library symbols. This discards all symbols
18548 that have been loaded from all shared libraries. Symbols from shared
18549 libraries that were loaded by explicit user requests are not
18553 Sometimes you may wish that @value{GDBN} stops and gives you control
18554 when any of shared library events happen. The best way to do this is
18555 to use @code{catch load} and @code{catch unload} (@pxref{Set
18558 @value{GDBN} also supports the the @code{set stop-on-solib-events}
18559 command for this. This command exists for historical reasons. It is
18560 less useful than setting a catchpoint, because it does not allow for
18561 conditions or commands as a catchpoint does.
18564 @item set stop-on-solib-events
18565 @kindex set stop-on-solib-events
18566 This command controls whether @value{GDBN} should give you control
18567 when the dynamic linker notifies it about some shared library event.
18568 The most common event of interest is loading or unloading of a new
18571 @item show stop-on-solib-events
18572 @kindex show stop-on-solib-events
18573 Show whether @value{GDBN} stops and gives you control when shared
18574 library events happen.
18577 Shared libraries are also supported in many cross or remote debugging
18578 configurations. @value{GDBN} needs to have access to the target's libraries;
18579 this can be accomplished either by providing copies of the libraries
18580 on the host system, or by asking @value{GDBN} to automatically retrieve the
18581 libraries from the target. If copies of the target libraries are
18582 provided, they need to be the same as the target libraries, although the
18583 copies on the target can be stripped as long as the copies on the host are
18586 @cindex where to look for shared libraries
18587 For remote debugging, you need to tell @value{GDBN} where the target
18588 libraries are, so that it can load the correct copies---otherwise, it
18589 may try to load the host's libraries. @value{GDBN} has two variables
18590 to specify the search directories for target libraries.
18593 @cindex prefix for executable and shared library file names
18594 @cindex system root, alternate
18595 @kindex set solib-absolute-prefix
18596 @kindex set sysroot
18597 @item set sysroot @var{path}
18598 Use @var{path} as the system root for the program being debugged. Any
18599 absolute shared library paths will be prefixed with @var{path}; many
18600 runtime loaders store the absolute paths to the shared library in the
18601 target program's memory. When starting processes remotely, and when
18602 attaching to already-running processes (local or remote), their
18603 executable filenames will be prefixed with @var{path} if reported to
18604 @value{GDBN} as absolute by the operating system. If you use
18605 @code{set sysroot} to find executables and shared libraries, they need
18606 to be laid out in the same way that they are on the target, with
18607 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
18610 If @var{path} starts with the sequence @file{target:} and the target
18611 system is remote then @value{GDBN} will retrieve the target binaries
18612 from the remote system. This is only supported when using a remote
18613 target that supports the @code{remote get} command (@pxref{File
18614 Transfer,,Sending files to a remote system}). The part of @var{path}
18615 following the initial @file{target:} (if present) is used as system
18616 root prefix on the remote file system. If @var{path} starts with the
18617 sequence @file{remote:} this is converted to the sequence
18618 @file{target:} by @code{set sysroot}@footnote{Historically the
18619 functionality to retrieve binaries from the remote system was
18620 provided by prefixing @var{path} with @file{remote:}}. If you want
18621 to specify a local system root using a directory that happens to be
18622 named @file{target:} or @file{remote:}, you need to use some
18623 equivalent variant of the name like @file{./target:}.
18625 For targets with an MS-DOS based filesystem, such as MS-Windows and
18626 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
18627 absolute file name with @var{path}. But first, on Unix hosts,
18628 @value{GDBN} converts all backslash directory separators into forward
18629 slashes, because the backslash is not a directory separator on Unix:
18632 c:\foo\bar.dll @result{} c:/foo/bar.dll
18635 Then, @value{GDBN} attempts prefixing the target file name with
18636 @var{path}, and looks for the resulting file name in the host file
18640 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
18643 If that does not find the binary, @value{GDBN} tries removing
18644 the @samp{:} character from the drive spec, both for convenience, and,
18645 for the case of the host file system not supporting file names with
18649 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
18652 This makes it possible to have a system root that mirrors a target
18653 with more than one drive. E.g., you may want to setup your local
18654 copies of the target system shared libraries like so (note @samp{c} vs
18658 @file{/path/to/sysroot/c/sys/bin/foo.dll}
18659 @file{/path/to/sysroot/c/sys/bin/bar.dll}
18660 @file{/path/to/sysroot/z/sys/bin/bar.dll}
18664 and point the system root at @file{/path/to/sysroot}, so that
18665 @value{GDBN} can find the correct copies of both
18666 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
18668 If that still does not find the binary, @value{GDBN} tries
18669 removing the whole drive spec from the target file name:
18672 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
18675 This last lookup makes it possible to not care about the drive name,
18676 if you don't want or need to.
18678 The @code{set solib-absolute-prefix} command is an alias for @code{set
18681 @cindex default system root
18682 @cindex @samp{--with-sysroot}
18683 You can set the default system root by using the configure-time
18684 @samp{--with-sysroot} option. If the system root is inside
18685 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
18686 @samp{--exec-prefix}), then the default system root will be updated
18687 automatically if the installed @value{GDBN} is moved to a new
18690 @kindex show sysroot
18692 Display the current executable and shared library prefix.
18694 @kindex set solib-search-path
18695 @item set solib-search-path @var{path}
18696 If this variable is set, @var{path} is a colon-separated list of
18697 directories to search for shared libraries. @samp{solib-search-path}
18698 is used after @samp{sysroot} fails to locate the library, or if the
18699 path to the library is relative instead of absolute. If you want to
18700 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
18701 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
18702 finding your host's libraries. @samp{sysroot} is preferred; setting
18703 it to a nonexistent directory may interfere with automatic loading
18704 of shared library symbols.
18706 @kindex show solib-search-path
18707 @item show solib-search-path
18708 Display the current shared library search path.
18710 @cindex DOS file-name semantics of file names.
18711 @kindex set target-file-system-kind (unix|dos-based|auto)
18712 @kindex show target-file-system-kind
18713 @item set target-file-system-kind @var{kind}
18714 Set assumed file system kind for target reported file names.
18716 Shared library file names as reported by the target system may not
18717 make sense as is on the system @value{GDBN} is running on. For
18718 example, when remote debugging a target that has MS-DOS based file
18719 system semantics, from a Unix host, the target may be reporting to
18720 @value{GDBN} a list of loaded shared libraries with file names such as
18721 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
18722 drive letters, so the @samp{c:\} prefix is not normally understood as
18723 indicating an absolute file name, and neither is the backslash
18724 normally considered a directory separator character. In that case,
18725 the native file system would interpret this whole absolute file name
18726 as a relative file name with no directory components. This would make
18727 it impossible to point @value{GDBN} at a copy of the remote target's
18728 shared libraries on the host using @code{set sysroot}, and impractical
18729 with @code{set solib-search-path}. Setting
18730 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
18731 to interpret such file names similarly to how the target would, and to
18732 map them to file names valid on @value{GDBN}'s native file system
18733 semantics. The value of @var{kind} can be @code{"auto"}, in addition
18734 to one of the supported file system kinds. In that case, @value{GDBN}
18735 tries to determine the appropriate file system variant based on the
18736 current target's operating system (@pxref{ABI, ,Configuring the
18737 Current ABI}). The supported file system settings are:
18741 Instruct @value{GDBN} to assume the target file system is of Unix
18742 kind. Only file names starting the forward slash (@samp{/}) character
18743 are considered absolute, and the directory separator character is also
18747 Instruct @value{GDBN} to assume the target file system is DOS based.
18748 File names starting with either a forward slash, or a drive letter
18749 followed by a colon (e.g., @samp{c:}), are considered absolute, and
18750 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
18751 considered directory separators.
18754 Instruct @value{GDBN} to use the file system kind associated with the
18755 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
18756 This is the default.
18760 @cindex file name canonicalization
18761 @cindex base name differences
18762 When processing file names provided by the user, @value{GDBN}
18763 frequently needs to compare them to the file names recorded in the
18764 program's debug info. Normally, @value{GDBN} compares just the
18765 @dfn{base names} of the files as strings, which is reasonably fast
18766 even for very large programs. (The base name of a file is the last
18767 portion of its name, after stripping all the leading directories.)
18768 This shortcut in comparison is based upon the assumption that files
18769 cannot have more than one base name. This is usually true, but
18770 references to files that use symlinks or similar filesystem
18771 facilities violate that assumption. If your program records files
18772 using such facilities, or if you provide file names to @value{GDBN}
18773 using symlinks etc., you can set @code{basenames-may-differ} to
18774 @code{true} to instruct @value{GDBN} to completely canonicalize each
18775 pair of file names it needs to compare. This will make file-name
18776 comparisons accurate, but at a price of a significant slowdown.
18779 @item set basenames-may-differ
18780 @kindex set basenames-may-differ
18781 Set whether a source file may have multiple base names.
18783 @item show basenames-may-differ
18784 @kindex show basenames-may-differ
18785 Show whether a source file may have multiple base names.
18789 @section File Caching
18790 @cindex caching of opened files
18791 @cindex caching of bfd objects
18793 To speed up file loading, and reduce memory usage, @value{GDBN} will
18794 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
18795 BFD, bfd, The Binary File Descriptor Library}. The following commands
18796 allow visibility and control of the caching behavior.
18799 @kindex maint info bfds
18800 @item maint info bfds
18801 This prints information about each @code{bfd} object that is known to
18804 @kindex maint set bfd-sharing
18805 @kindex maint show bfd-sharing
18806 @kindex bfd caching
18807 @item maint set bfd-sharing
18808 @item maint show bfd-sharing
18809 Control whether @code{bfd} objects can be shared. When sharing is
18810 enabled @value{GDBN} reuses already open @code{bfd} objects rather
18811 than reopening the same file. Turning sharing off does not cause
18812 already shared @code{bfd} objects to be unshared, but all future files
18813 that are opened will create a new @code{bfd} object. Similarly,
18814 re-enabling sharing does not cause multiple existing @code{bfd}
18815 objects to be collapsed into a single shared @code{bfd} object.
18817 @kindex set debug bfd-cache @var{level}
18818 @kindex bfd caching
18819 @item set debug bfd-cache @var{level}
18820 Turns on debugging of the bfd cache, setting the level to @var{level}.
18822 @kindex show debug bfd-cache
18823 @kindex bfd caching
18824 @item show debug bfd-cache
18825 Show the current debugging level of the bfd cache.
18828 @node Separate Debug Files
18829 @section Debugging Information in Separate Files
18830 @cindex separate debugging information files
18831 @cindex debugging information in separate files
18832 @cindex @file{.debug} subdirectories
18833 @cindex debugging information directory, global
18834 @cindex global debugging information directories
18835 @cindex build ID, and separate debugging files
18836 @cindex @file{.build-id} directory
18838 @value{GDBN} allows you to put a program's debugging information in a
18839 file separate from the executable itself, in a way that allows
18840 @value{GDBN} to find and load the debugging information automatically.
18841 Since debugging information can be very large---sometimes larger
18842 than the executable code itself---some systems distribute debugging
18843 information for their executables in separate files, which users can
18844 install only when they need to debug a problem.
18846 @value{GDBN} supports two ways of specifying the separate debug info
18851 The executable contains a @dfn{debug link} that specifies the name of
18852 the separate debug info file. The separate debug file's name is
18853 usually @file{@var{executable}.debug}, where @var{executable} is the
18854 name of the corresponding executable file without leading directories
18855 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
18856 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
18857 checksum for the debug file, which @value{GDBN} uses to validate that
18858 the executable and the debug file came from the same build.
18861 The executable contains a @dfn{build ID}, a unique bit string that is
18862 also present in the corresponding debug info file. (This is supported
18863 only on some operating systems, when using the ELF or PE file formats
18864 for binary files and the @sc{gnu} Binutils.) For more details about
18865 this feature, see the description of the @option{--build-id}
18866 command-line option in @ref{Options, , Command Line Options, ld.info,
18867 The GNU Linker}. The debug info file's name is not specified
18868 explicitly by the build ID, but can be computed from the build ID, see
18872 Depending on the way the debug info file is specified, @value{GDBN}
18873 uses two different methods of looking for the debug file:
18877 For the ``debug link'' method, @value{GDBN} looks up the named file in
18878 the directory of the executable file, then in a subdirectory of that
18879 directory named @file{.debug}, and finally under each one of the global debug
18880 directories, in a subdirectory whose name is identical to the leading
18881 directories of the executable's absolute file name.
18884 For the ``build ID'' method, @value{GDBN} looks in the
18885 @file{.build-id} subdirectory of each one of the global debug directories for
18886 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
18887 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
18888 are the rest of the bit string. (Real build ID strings are 32 or more
18889 hex characters, not 10.)
18892 So, for example, suppose you ask @value{GDBN} to debug
18893 @file{/usr/bin/ls}, which has a debug link that specifies the
18894 file @file{ls.debug}, and a build ID whose value in hex is
18895 @code{abcdef1234}. If the list of the global debug directories includes
18896 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
18897 debug information files, in the indicated order:
18901 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
18903 @file{/usr/bin/ls.debug}
18905 @file{/usr/bin/.debug/ls.debug}
18907 @file{/usr/lib/debug/usr/bin/ls.debug}.
18910 @anchor{debug-file-directory}
18911 Global debugging info directories default to what is set by @value{GDBN}
18912 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
18913 you can also set the global debugging info directories, and view the list
18914 @value{GDBN} is currently using.
18918 @kindex set debug-file-directory
18919 @item set debug-file-directory @var{directories}
18920 Set the directories which @value{GDBN} searches for separate debugging
18921 information files to @var{directory}. Multiple path components can be set
18922 concatenating them by a path separator.
18924 @kindex show debug-file-directory
18925 @item show debug-file-directory
18926 Show the directories @value{GDBN} searches for separate debugging
18931 @cindex @code{.gnu_debuglink} sections
18932 @cindex debug link sections
18933 A debug link is a special section of the executable file named
18934 @code{.gnu_debuglink}. The section must contain:
18938 A filename, with any leading directory components removed, followed by
18941 zero to three bytes of padding, as needed to reach the next four-byte
18942 boundary within the section, and
18944 a four-byte CRC checksum, stored in the same endianness used for the
18945 executable file itself. The checksum is computed on the debugging
18946 information file's full contents by the function given below, passing
18947 zero as the @var{crc} argument.
18950 Any executable file format can carry a debug link, as long as it can
18951 contain a section named @code{.gnu_debuglink} with the contents
18954 @cindex @code{.note.gnu.build-id} sections
18955 @cindex build ID sections
18956 The build ID is a special section in the executable file (and in other
18957 ELF binary files that @value{GDBN} may consider). This section is
18958 often named @code{.note.gnu.build-id}, but that name is not mandatory.
18959 It contains unique identification for the built files---the ID remains
18960 the same across multiple builds of the same build tree. The default
18961 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
18962 content for the build ID string. The same section with an identical
18963 value is present in the original built binary with symbols, in its
18964 stripped variant, and in the separate debugging information file.
18966 The debugging information file itself should be an ordinary
18967 executable, containing a full set of linker symbols, sections, and
18968 debugging information. The sections of the debugging information file
18969 should have the same names, addresses, and sizes as the original file,
18970 but they need not contain any data---much like a @code{.bss} section
18971 in an ordinary executable.
18973 The @sc{gnu} binary utilities (Binutils) package includes the
18974 @samp{objcopy} utility that can produce
18975 the separated executable / debugging information file pairs using the
18976 following commands:
18979 @kbd{objcopy --only-keep-debug foo foo.debug}
18984 These commands remove the debugging
18985 information from the executable file @file{foo} and place it in the file
18986 @file{foo.debug}. You can use the first, second or both methods to link the
18991 The debug link method needs the following additional command to also leave
18992 behind a debug link in @file{foo}:
18995 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
18998 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
18999 a version of the @code{strip} command such that the command @kbd{strip foo -f
19000 foo.debug} has the same functionality as the two @code{objcopy} commands and
19001 the @code{ln -s} command above, together.
19004 Build ID gets embedded into the main executable using @code{ld --build-id} or
19005 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
19006 compatibility fixes for debug files separation are present in @sc{gnu} binary
19007 utilities (Binutils) package since version 2.18.
19012 @cindex CRC algorithm definition
19013 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
19014 IEEE 802.3 using the polynomial:
19016 @c TexInfo requires naked braces for multi-digit exponents for Tex
19017 @c output, but this causes HTML output to barf. HTML has to be set using
19018 @c raw commands. So we end up having to specify this equation in 2
19023 <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>
19024 + <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
19030 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
19031 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
19035 The function is computed byte at a time, taking the least
19036 significant bit of each byte first. The initial pattern
19037 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
19038 the final result is inverted to ensure trailing zeros also affect the
19041 @emph{Note:} This is the same CRC polynomial as used in handling the
19042 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
19043 However in the case of the Remote Serial Protocol, the CRC is computed
19044 @emph{most} significant bit first, and the result is not inverted, so
19045 trailing zeros have no effect on the CRC value.
19047 To complete the description, we show below the code of the function
19048 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
19049 initially supplied @code{crc} argument means that an initial call to
19050 this function passing in zero will start computing the CRC using
19053 @kindex gnu_debuglink_crc32
19056 gnu_debuglink_crc32 (unsigned long crc,
19057 unsigned char *buf, size_t len)
19059 static const unsigned long crc32_table[256] =
19061 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
19062 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
19063 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
19064 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
19065 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
19066 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
19067 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
19068 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
19069 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
19070 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
19071 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
19072 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
19073 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
19074 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
19075 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
19076 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
19077 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
19078 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
19079 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
19080 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
19081 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
19082 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
19083 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
19084 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
19085 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
19086 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
19087 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
19088 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
19089 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
19090 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
19091 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
19092 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
19093 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
19094 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
19095 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
19096 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
19097 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
19098 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
19099 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
19100 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
19101 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
19102 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
19103 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
19104 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
19105 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
19106 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
19107 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
19108 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
19109 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
19110 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
19111 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
19114 unsigned char *end;
19116 crc = ~crc & 0xffffffff;
19117 for (end = buf + len; buf < end; ++buf)
19118 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
19119 return ~crc & 0xffffffff;
19124 This computation does not apply to the ``build ID'' method.
19126 @node MiniDebugInfo
19127 @section Debugging information in a special section
19128 @cindex separate debug sections
19129 @cindex @samp{.gnu_debugdata} section
19131 Some systems ship pre-built executables and libraries that have a
19132 special @samp{.gnu_debugdata} section. This feature is called
19133 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
19134 is used to supply extra symbols for backtraces.
19136 The intent of this section is to provide extra minimal debugging
19137 information for use in simple backtraces. It is not intended to be a
19138 replacement for full separate debugging information (@pxref{Separate
19139 Debug Files}). The example below shows the intended use; however,
19140 @value{GDBN} does not currently put restrictions on what sort of
19141 debugging information might be included in the section.
19143 @value{GDBN} has support for this extension. If the section exists,
19144 then it is used provided that no other source of debugging information
19145 can be found, and that @value{GDBN} was configured with LZMA support.
19147 This section can be easily created using @command{objcopy} and other
19148 standard utilities:
19151 # Extract the dynamic symbols from the main binary, there is no need
19152 # to also have these in the normal symbol table.
19153 nm -D @var{binary} --format=posix --defined-only \
19154 | awk '@{ print $1 @}' | sort > dynsyms
19156 # Extract all the text (i.e. function) symbols from the debuginfo.
19157 # (Note that we actually also accept "D" symbols, for the benefit
19158 # of platforms like PowerPC64 that use function descriptors.)
19159 nm @var{binary} --format=posix --defined-only \
19160 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
19163 # Keep all the function symbols not already in the dynamic symbol
19165 comm -13 dynsyms funcsyms > keep_symbols
19167 # Separate full debug info into debug binary.
19168 objcopy --only-keep-debug @var{binary} debug
19170 # Copy the full debuginfo, keeping only a minimal set of symbols and
19171 # removing some unnecessary sections.
19172 objcopy -S --remove-section .gdb_index --remove-section .comment \
19173 --keep-symbols=keep_symbols debug mini_debuginfo
19175 # Drop the full debug info from the original binary.
19176 strip --strip-all -R .comment @var{binary}
19178 # Inject the compressed data into the .gnu_debugdata section of the
19181 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
19185 @section Index Files Speed Up @value{GDBN}
19186 @cindex index files
19187 @cindex @samp{.gdb_index} section
19189 When @value{GDBN} finds a symbol file, it scans the symbols in the
19190 file in order to construct an internal symbol table. This lets most
19191 @value{GDBN} operations work quickly---at the cost of a delay early
19192 on. For large programs, this delay can be quite lengthy, so
19193 @value{GDBN} provides a way to build an index, which speeds up
19196 The index is stored as a section in the symbol file. @value{GDBN} can
19197 write the index to a file, then you can put it into the symbol file
19198 using @command{objcopy}.
19200 To create an index file, use the @code{save gdb-index} command:
19203 @item save gdb-index @var{directory}
19204 @kindex save gdb-index
19205 Create an index file for each symbol file currently known by
19206 @value{GDBN}. Each file is named after its corresponding symbol file,
19207 with @samp{.gdb-index} appended, and is written into the given
19211 Once you have created an index file you can merge it into your symbol
19212 file, here named @file{symfile}, using @command{objcopy}:
19215 $ objcopy --add-section .gdb_index=symfile.gdb-index \
19216 --set-section-flags .gdb_index=readonly symfile symfile
19219 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
19220 sections that have been deprecated. Usually they are deprecated because
19221 they are missing a new feature or have performance issues.
19222 To tell @value{GDBN} to use a deprecated index section anyway
19223 specify @code{set use-deprecated-index-sections on}.
19224 The default is @code{off}.
19225 This can speed up startup, but may result in some functionality being lost.
19226 @xref{Index Section Format}.
19228 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
19229 must be done before gdb reads the file. The following will not work:
19232 $ gdb -ex "set use-deprecated-index-sections on" <program>
19235 Instead you must do, for example,
19238 $ gdb -iex "set use-deprecated-index-sections on" <program>
19241 There are currently some limitation on indices. They only work when
19242 for DWARF debugging information, not stabs. And, they do not
19243 currently work for programs using Ada.
19245 @node Symbol Errors
19246 @section Errors Reading Symbol Files
19248 While reading a symbol file, @value{GDBN} occasionally encounters problems,
19249 such as symbol types it does not recognize, or known bugs in compiler
19250 output. By default, @value{GDBN} does not notify you of such problems, since
19251 they are relatively common and primarily of interest to people
19252 debugging compilers. If you are interested in seeing information
19253 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
19254 only one message about each such type of problem, no matter how many
19255 times the problem occurs; or you can ask @value{GDBN} to print more messages,
19256 to see how many times the problems occur, with the @code{set
19257 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
19260 The messages currently printed, and their meanings, include:
19263 @item inner block not inside outer block in @var{symbol}
19265 The symbol information shows where symbol scopes begin and end
19266 (such as at the start of a function or a block of statements). This
19267 error indicates that an inner scope block is not fully contained
19268 in its outer scope blocks.
19270 @value{GDBN} circumvents the problem by treating the inner block as if it had
19271 the same scope as the outer block. In the error message, @var{symbol}
19272 may be shown as ``@code{(don't know)}'' if the outer block is not a
19275 @item block at @var{address} out of order
19277 The symbol information for symbol scope blocks should occur in
19278 order of increasing addresses. This error indicates that it does not
19281 @value{GDBN} does not circumvent this problem, and has trouble
19282 locating symbols in the source file whose symbols it is reading. (You
19283 can often determine what source file is affected by specifying
19284 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
19287 @item bad block start address patched
19289 The symbol information for a symbol scope block has a start address
19290 smaller than the address of the preceding source line. This is known
19291 to occur in the SunOS 4.1.1 (and earlier) C compiler.
19293 @value{GDBN} circumvents the problem by treating the symbol scope block as
19294 starting on the previous source line.
19296 @item bad string table offset in symbol @var{n}
19299 Symbol number @var{n} contains a pointer into the string table which is
19300 larger than the size of the string table.
19302 @value{GDBN} circumvents the problem by considering the symbol to have the
19303 name @code{foo}, which may cause other problems if many symbols end up
19306 @item unknown symbol type @code{0x@var{nn}}
19308 The symbol information contains new data types that @value{GDBN} does
19309 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
19310 uncomprehended information, in hexadecimal.
19312 @value{GDBN} circumvents the error by ignoring this symbol information.
19313 This usually allows you to debug your program, though certain symbols
19314 are not accessible. If you encounter such a problem and feel like
19315 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
19316 on @code{complain}, then go up to the function @code{read_dbx_symtab}
19317 and examine @code{*bufp} to see the symbol.
19319 @item stub type has NULL name
19321 @value{GDBN} could not find the full definition for a struct or class.
19323 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
19324 The symbol information for a C@t{++} member function is missing some
19325 information that recent versions of the compiler should have output for
19328 @item info mismatch between compiler and debugger
19330 @value{GDBN} could not parse a type specification output by the compiler.
19335 @section GDB Data Files
19337 @cindex prefix for data files
19338 @value{GDBN} will sometimes read an auxiliary data file. These files
19339 are kept in a directory known as the @dfn{data directory}.
19341 You can set the data directory's name, and view the name @value{GDBN}
19342 is currently using.
19345 @kindex set data-directory
19346 @item set data-directory @var{directory}
19347 Set the directory which @value{GDBN} searches for auxiliary data files
19348 to @var{directory}.
19350 @kindex show data-directory
19351 @item show data-directory
19352 Show the directory @value{GDBN} searches for auxiliary data files.
19355 @cindex default data directory
19356 @cindex @samp{--with-gdb-datadir}
19357 You can set the default data directory by using the configure-time
19358 @samp{--with-gdb-datadir} option. If the data directory is inside
19359 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
19360 @samp{--exec-prefix}), then the default data directory will be updated
19361 automatically if the installed @value{GDBN} is moved to a new
19364 The data directory may also be specified with the
19365 @code{--data-directory} command line option.
19366 @xref{Mode Options}.
19369 @chapter Specifying a Debugging Target
19371 @cindex debugging target
19372 A @dfn{target} is the execution environment occupied by your program.
19374 Often, @value{GDBN} runs in the same host environment as your program;
19375 in that case, the debugging target is specified as a side effect when
19376 you use the @code{file} or @code{core} commands. When you need more
19377 flexibility---for example, running @value{GDBN} on a physically separate
19378 host, or controlling a standalone system over a serial port or a
19379 realtime system over a TCP/IP connection---you can use the @code{target}
19380 command to specify one of the target types configured for @value{GDBN}
19381 (@pxref{Target Commands, ,Commands for Managing Targets}).
19383 @cindex target architecture
19384 It is possible to build @value{GDBN} for several different @dfn{target
19385 architectures}. When @value{GDBN} is built like that, you can choose
19386 one of the available architectures with the @kbd{set architecture}
19390 @kindex set architecture
19391 @kindex show architecture
19392 @item set architecture @var{arch}
19393 This command sets the current target architecture to @var{arch}. The
19394 value of @var{arch} can be @code{"auto"}, in addition to one of the
19395 supported architectures.
19397 @item show architecture
19398 Show the current target architecture.
19400 @item set processor
19402 @kindex set processor
19403 @kindex show processor
19404 These are alias commands for, respectively, @code{set architecture}
19405 and @code{show architecture}.
19409 * Active Targets:: Active targets
19410 * Target Commands:: Commands for managing targets
19411 * Byte Order:: Choosing target byte order
19414 @node Active Targets
19415 @section Active Targets
19417 @cindex stacking targets
19418 @cindex active targets
19419 @cindex multiple targets
19421 There are multiple classes of targets such as: processes, executable files or
19422 recording sessions. Core files belong to the process class, making core file
19423 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
19424 on multiple active targets, one in each class. This allows you to (for
19425 example) start a process and inspect its activity, while still having access to
19426 the executable file after the process finishes. Or if you start process
19427 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
19428 presented a virtual layer of the recording target, while the process target
19429 remains stopped at the chronologically last point of the process execution.
19431 Use the @code{core-file} and @code{exec-file} commands to select a new core
19432 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
19433 specify as a target a process that is already running, use the @code{attach}
19434 command (@pxref{Attach, ,Debugging an Already-running Process}).
19436 @node Target Commands
19437 @section Commands for Managing Targets
19440 @item target @var{type} @var{parameters}
19441 Connects the @value{GDBN} host environment to a target machine or
19442 process. A target is typically a protocol for talking to debugging
19443 facilities. You use the argument @var{type} to specify the type or
19444 protocol of the target machine.
19446 Further @var{parameters} are interpreted by the target protocol, but
19447 typically include things like device names or host names to connect
19448 with, process numbers, and baud rates.
19450 The @code{target} command does not repeat if you press @key{RET} again
19451 after executing the command.
19453 @kindex help target
19455 Displays the names of all targets available. To display targets
19456 currently selected, use either @code{info target} or @code{info files}
19457 (@pxref{Files, ,Commands to Specify Files}).
19459 @item help target @var{name}
19460 Describe a particular target, including any parameters necessary to
19463 @kindex set gnutarget
19464 @item set gnutarget @var{args}
19465 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
19466 knows whether it is reading an @dfn{executable},
19467 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
19468 with the @code{set gnutarget} command. Unlike most @code{target} commands,
19469 with @code{gnutarget} the @code{target} refers to a program, not a machine.
19472 @emph{Warning:} To specify a file format with @code{set gnutarget},
19473 you must know the actual BFD name.
19477 @xref{Files, , Commands to Specify Files}.
19479 @kindex show gnutarget
19480 @item show gnutarget
19481 Use the @code{show gnutarget} command to display what file format
19482 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
19483 @value{GDBN} will determine the file format for each file automatically,
19484 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
19487 @cindex common targets
19488 Here are some common targets (available, or not, depending on the GDB
19493 @item target exec @var{program}
19494 @cindex executable file target
19495 An executable file. @samp{target exec @var{program}} is the same as
19496 @samp{exec-file @var{program}}.
19498 @item target core @var{filename}
19499 @cindex core dump file target
19500 A core dump file. @samp{target core @var{filename}} is the same as
19501 @samp{core-file @var{filename}}.
19503 @item target remote @var{medium}
19504 @cindex remote target
19505 A remote system connected to @value{GDBN} via a serial line or network
19506 connection. This command tells @value{GDBN} to use its own remote
19507 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
19509 For example, if you have a board connected to @file{/dev/ttya} on the
19510 machine running @value{GDBN}, you could say:
19513 target remote /dev/ttya
19516 @code{target remote} supports the @code{load} command. This is only
19517 useful if you have some other way of getting the stub to the target
19518 system, and you can put it somewhere in memory where it won't get
19519 clobbered by the download.
19521 @item target sim @r{[}@var{simargs}@r{]} @dots{}
19522 @cindex built-in simulator target
19523 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
19531 works; however, you cannot assume that a specific memory map, device
19532 drivers, or even basic I/O is available, although some simulators do
19533 provide these. For info about any processor-specific simulator details,
19534 see the appropriate section in @ref{Embedded Processors, ,Embedded
19537 @item target native
19538 @cindex native target
19539 Setup for local/native process debugging. Useful to make the
19540 @code{run} command spawn native processes (likewise @code{attach},
19541 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
19542 (@pxref{set auto-connect-native-target}).
19546 Different targets are available on different configurations of @value{GDBN};
19547 your configuration may have more or fewer targets.
19549 Many remote targets require you to download the executable's code once
19550 you've successfully established a connection. You may wish to control
19551 various aspects of this process.
19556 @kindex set hash@r{, for remote monitors}
19557 @cindex hash mark while downloading
19558 This command controls whether a hash mark @samp{#} is displayed while
19559 downloading a file to the remote monitor. If on, a hash mark is
19560 displayed after each S-record is successfully downloaded to the
19564 @kindex show hash@r{, for remote monitors}
19565 Show the current status of displaying the hash mark.
19567 @item set debug monitor
19568 @kindex set debug monitor
19569 @cindex display remote monitor communications
19570 Enable or disable display of communications messages between
19571 @value{GDBN} and the remote monitor.
19573 @item show debug monitor
19574 @kindex show debug monitor
19575 Show the current status of displaying communications between
19576 @value{GDBN} and the remote monitor.
19581 @kindex load @var{filename}
19582 @item load @var{filename}
19584 Depending on what remote debugging facilities are configured into
19585 @value{GDBN}, the @code{load} command may be available. Where it exists, it
19586 is meant to make @var{filename} (an executable) available for debugging
19587 on the remote system---by downloading, or dynamic linking, for example.
19588 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
19589 the @code{add-symbol-file} command.
19591 If your @value{GDBN} does not have a @code{load} command, attempting to
19592 execute it gets the error message ``@code{You can't do that when your
19593 target is @dots{}}''
19595 The file is loaded at whatever address is specified in the executable.
19596 For some object file formats, you can specify the load address when you
19597 link the program; for other formats, like a.out, the object file format
19598 specifies a fixed address.
19599 @c FIXME! This would be a good place for an xref to the GNU linker doc.
19601 Depending on the remote side capabilities, @value{GDBN} may be able to
19602 load programs into flash memory.
19604 @code{load} does not repeat if you press @key{RET} again after using it.
19608 @section Choosing Target Byte Order
19610 @cindex choosing target byte order
19611 @cindex target byte order
19613 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
19614 offer the ability to run either big-endian or little-endian byte
19615 orders. Usually the executable or symbol will include a bit to
19616 designate the endian-ness, and you will not need to worry about
19617 which to use. However, you may still find it useful to adjust
19618 @value{GDBN}'s idea of processor endian-ness manually.
19622 @item set endian big
19623 Instruct @value{GDBN} to assume the target is big-endian.
19625 @item set endian little
19626 Instruct @value{GDBN} to assume the target is little-endian.
19628 @item set endian auto
19629 Instruct @value{GDBN} to use the byte order associated with the
19633 Display @value{GDBN}'s current idea of the target byte order.
19637 Note that these commands merely adjust interpretation of symbolic
19638 data on the host, and that they have absolutely no effect on the
19642 @node Remote Debugging
19643 @chapter Debugging Remote Programs
19644 @cindex remote debugging
19646 If you are trying to debug a program running on a machine that cannot run
19647 @value{GDBN} in the usual way, it is often useful to use remote debugging.
19648 For example, you might use remote debugging on an operating system kernel,
19649 or on a small system which does not have a general purpose operating system
19650 powerful enough to run a full-featured debugger.
19652 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
19653 to make this work with particular debugging targets. In addition,
19654 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
19655 but not specific to any particular target system) which you can use if you
19656 write the remote stubs---the code that runs on the remote system to
19657 communicate with @value{GDBN}.
19659 Other remote targets may be available in your
19660 configuration of @value{GDBN}; use @code{help target} to list them.
19663 * Connecting:: Connecting to a remote target
19664 * File Transfer:: Sending files to a remote system
19665 * Server:: Using the gdbserver program
19666 * Remote Configuration:: Remote configuration
19667 * Remote Stub:: Implementing a remote stub
19671 @section Connecting to a Remote Target
19672 @cindex remote debugging, connecting
19673 @cindex @code{gdbserver}, connecting
19674 @cindex remote debugging, types of connections
19675 @cindex @code{gdbserver}, types of connections
19676 @cindex @code{gdbserver}, @code{target remote} mode
19677 @cindex @code{gdbserver}, @code{target extended-remote} mode
19679 This section describes how to connect to a remote target, including the
19680 types of connections and their differences, how to set up executable and
19681 symbol files on the host and target, and the commands used for
19682 connecting to and disconnecting from the remote target.
19684 @subsection Types of Remote Connections
19686 @value{GDBN} supports two types of remote connections, @code{target remote}
19687 mode and @code{target extended-remote} mode. Note that many remote targets
19688 support only @code{target remote} mode. There are several major
19689 differences between the two types of connections, enumerated here:
19693 @cindex remote debugging, detach and program exit
19694 @item Result of detach or program exit
19695 @strong{With target remote mode:} When the debugged program exits or you
19696 detach from it, @value{GDBN} disconnects from the target. When using
19697 @code{gdbserver}, @code{gdbserver} will exit.
19699 @strong{With target extended-remote mode:} When the debugged program exits or
19700 you detach from it, @value{GDBN} remains connected to the target, even
19701 though no program is running. You can rerun the program, attach to a
19702 running program, or use @code{monitor} commands specific to the target.
19704 When using @code{gdbserver} in this case, it does not exit unless it was
19705 invoked using the @option{--once} option. If the @option{--once} option
19706 was not used, you can ask @code{gdbserver} to exit using the
19707 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
19709 @item Specifying the program to debug
19710 For both connection types you use the @code{file} command to specify the
19711 program on the host system. If you are using @code{gdbserver} there are
19712 some differences in how to specify the location of the program on the
19715 @strong{With target remote mode:} You must either specify the program to debug
19716 on the @code{gdbserver} command line or use the @option{--attach} option
19717 (@pxref{Attaching to a program,,Attaching to a Running Program}).
19719 @cindex @option{--multi}, @code{gdbserver} option
19720 @strong{With target extended-remote mode:} You may specify the program to debug
19721 on the @code{gdbserver} command line, or you can load the program or attach
19722 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
19724 @anchor{--multi Option in Types of Remote Connnections}
19725 You can start @code{gdbserver} without supplying an initial command to run
19726 or process ID to attach. To do this, use the @option{--multi} command line
19727 option. Then you can connect using @code{target extended-remote} and start
19728 the program you want to debug (see below for details on using the
19729 @code{run} command in this scenario). Note that the conditions under which
19730 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
19731 (@code{target remote} or @code{target extended-remote}). The
19732 @option{--multi} option to @code{gdbserver} has no influence on that.
19734 @item The @code{run} command
19735 @strong{With target remote mode:} The @code{run} command is not
19736 supported. Once a connection has been established, you can use all
19737 the usual @value{GDBN} commands to examine and change data. The
19738 remote program is already running, so you can use commands like
19739 @kbd{step} and @kbd{continue}.
19741 @strong{With target extended-remote mode:} The @code{run} command is
19742 supported. The @code{run} command uses the value set by
19743 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
19744 the program to run. Command line arguments are supported, except for
19745 wildcard expansion and I/O redirection (@pxref{Arguments}).
19747 If you specify the program to debug on the command line, then the
19748 @code{run} command is not required to start execution, and you can
19749 resume using commands like @kbd{step} and @kbd{continue} as with
19750 @code{target remote} mode.
19752 @anchor{Attaching in Types of Remote Connections}
19754 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
19755 not supported. To attach to a running program using @code{gdbserver}, you
19756 must use the @option{--attach} option (@pxref{Running gdbserver}).
19758 @strong{With target extended-remote mode:} To attach to a running program,
19759 you may use the @code{attach} command after the connection has been
19760 established. If you are using @code{gdbserver}, you may also invoke
19761 @code{gdbserver} using the @option{--attach} option
19762 (@pxref{Running gdbserver}).
19766 @anchor{Host and target files}
19767 @subsection Host and Target Files
19768 @cindex remote debugging, symbol files
19769 @cindex symbol files, remote debugging
19771 @value{GDBN}, running on the host, needs access to symbol and debugging
19772 information for your program running on the target. This requires
19773 access to an unstripped copy of your program, and possibly any associated
19774 symbol files. Note that this section applies equally to both @code{target
19775 remote} mode and @code{target extended-remote} mode.
19777 Some remote targets (@pxref{qXfer executable filename read}, and
19778 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
19779 the same connection used to communicate with @value{GDBN}. With such a
19780 target, if the remote program is unstripped, the only command you need is
19781 @code{target remote} (or @code{target extended-remote}).
19783 If the remote program is stripped, or the target does not support remote
19784 program file access, start up @value{GDBN} using the name of the local
19785 unstripped copy of your program as the first argument, or use the
19786 @code{file} command. Use @code{set sysroot} to specify the location (on
19787 the host) of target libraries (unless your @value{GDBN} was compiled with
19788 the correct sysroot using @code{--with-sysroot}). Alternatively, you
19789 may use @code{set solib-search-path} to specify how @value{GDBN} locates
19792 The symbol file and target libraries must exactly match the executable
19793 and libraries on the target, with one exception: the files on the host
19794 system should not be stripped, even if the files on the target system
19795 are. Mismatched or missing files will lead to confusing results
19796 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
19797 files may also prevent @code{gdbserver} from debugging multi-threaded
19800 @subsection Remote Connection Commands
19801 @cindex remote connection commands
19802 @value{GDBN} can communicate with the target over a serial line, or
19803 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
19804 each case, @value{GDBN} uses the same protocol for debugging your
19805 program; only the medium carrying the debugging packets varies. The
19806 @code{target remote} and @code{target extended-remote} commands
19807 establish a connection to the target. Both commands accept the same
19808 arguments, which indicate the medium to use:
19812 @item target remote @var{serial-device}
19813 @itemx target extended-remote @var{serial-device}
19814 @cindex serial line, @code{target remote}
19815 Use @var{serial-device} to communicate with the target. For example,
19816 to use a serial line connected to the device named @file{/dev/ttyb}:
19819 target remote /dev/ttyb
19822 If you're using a serial line, you may want to give @value{GDBN} the
19823 @samp{--baud} option, or use the @code{set serial baud} command
19824 (@pxref{Remote Configuration, set serial baud}) before the
19825 @code{target} command.
19827 @item target remote @code{@var{host}:@var{port}}
19828 @itemx target remote @code{tcp:@var{host}:@var{port}}
19829 @itemx target extended-remote @code{@var{host}:@var{port}}
19830 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
19831 @cindex @acronym{TCP} port, @code{target remote}
19832 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
19833 The @var{host} may be either a host name or a numeric @acronym{IP}
19834 address; @var{port} must be a decimal number. The @var{host} could be
19835 the target machine itself, if it is directly connected to the net, or
19836 it might be a terminal server which in turn has a serial line to the
19839 For example, to connect to port 2828 on a terminal server named
19843 target remote manyfarms:2828
19846 If your remote target is actually running on the same machine as your
19847 debugger session (e.g.@: a simulator for your target running on the
19848 same host), you can omit the hostname. For example, to connect to
19849 port 1234 on your local machine:
19852 target remote :1234
19856 Note that the colon is still required here.
19858 @item target remote @code{udp:@var{host}:@var{port}}
19859 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
19860 @cindex @acronym{UDP} port, @code{target remote}
19861 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
19862 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
19865 target remote udp:manyfarms:2828
19868 When using a @acronym{UDP} connection for remote debugging, you should
19869 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
19870 can silently drop packets on busy or unreliable networks, which will
19871 cause havoc with your debugging session.
19873 @item target remote | @var{command}
19874 @itemx target extended-remote | @var{command}
19875 @cindex pipe, @code{target remote} to
19876 Run @var{command} in the background and communicate with it using a
19877 pipe. The @var{command} is a shell command, to be parsed and expanded
19878 by the system's command shell, @code{/bin/sh}; it should expect remote
19879 protocol packets on its standard input, and send replies on its
19880 standard output. You could use this to run a stand-alone simulator
19881 that speaks the remote debugging protocol, to make net connections
19882 using programs like @code{ssh}, or for other similar tricks.
19884 If @var{command} closes its standard output (perhaps by exiting),
19885 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
19886 program has already exited, this will have no effect.)
19890 @cindex interrupting remote programs
19891 @cindex remote programs, interrupting
19892 Whenever @value{GDBN} is waiting for the remote program, if you type the
19893 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
19894 program. This may or may not succeed, depending in part on the hardware
19895 and the serial drivers the remote system uses. If you type the
19896 interrupt character once again, @value{GDBN} displays this prompt:
19899 Interrupted while waiting for the program.
19900 Give up (and stop debugging it)? (y or n)
19903 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
19904 the remote debugging session. (If you decide you want to try again later,
19905 you can use @kbd{target remote} again to connect once more.) If you type
19906 @kbd{n}, @value{GDBN} goes back to waiting.
19908 In @code{target extended-remote} mode, typing @kbd{n} will leave
19909 @value{GDBN} connected to the target.
19912 @kindex detach (remote)
19914 When you have finished debugging the remote program, you can use the
19915 @code{detach} command to release it from @value{GDBN} control.
19916 Detaching from the target normally resumes its execution, but the results
19917 will depend on your particular remote stub. After the @code{detach}
19918 command in @code{target remote} mode, @value{GDBN} is free to connect to
19919 another target. In @code{target extended-remote} mode, @value{GDBN} is
19920 still connected to the target.
19924 The @code{disconnect} command closes the connection to the target, and
19925 the target is generally not resumed. It will wait for @value{GDBN}
19926 (this instance or another one) to connect and continue debugging. After
19927 the @code{disconnect} command, @value{GDBN} is again free to connect to
19930 @cindex send command to remote monitor
19931 @cindex extend @value{GDBN} for remote targets
19932 @cindex add new commands for external monitor
19934 @item monitor @var{cmd}
19935 This command allows you to send arbitrary commands directly to the
19936 remote monitor. Since @value{GDBN} doesn't care about the commands it
19937 sends like this, this command is the way to extend @value{GDBN}---you
19938 can add new commands that only the external monitor will understand
19942 @node File Transfer
19943 @section Sending files to a remote system
19944 @cindex remote target, file transfer
19945 @cindex file transfer
19946 @cindex sending files to remote systems
19948 Some remote targets offer the ability to transfer files over the same
19949 connection used to communicate with @value{GDBN}. This is convenient
19950 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
19951 running @code{gdbserver} over a network interface. For other targets,
19952 e.g.@: embedded devices with only a single serial port, this may be
19953 the only way to upload or download files.
19955 Not all remote targets support these commands.
19959 @item remote put @var{hostfile} @var{targetfile}
19960 Copy file @var{hostfile} from the host system (the machine running
19961 @value{GDBN}) to @var{targetfile} on the target system.
19964 @item remote get @var{targetfile} @var{hostfile}
19965 Copy file @var{targetfile} from the target system to @var{hostfile}
19966 on the host system.
19968 @kindex remote delete
19969 @item remote delete @var{targetfile}
19970 Delete @var{targetfile} from the target system.
19975 @section Using the @code{gdbserver} Program
19978 @cindex remote connection without stubs
19979 @code{gdbserver} is a control program for Unix-like systems, which
19980 allows you to connect your program with a remote @value{GDBN} via
19981 @code{target remote} or @code{target extended-remote}---but without
19982 linking in the usual debugging stub.
19984 @code{gdbserver} is not a complete replacement for the debugging stubs,
19985 because it requires essentially the same operating-system facilities
19986 that @value{GDBN} itself does. In fact, a system that can run
19987 @code{gdbserver} to connect to a remote @value{GDBN} could also run
19988 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
19989 because it is a much smaller program than @value{GDBN} itself. It is
19990 also easier to port than all of @value{GDBN}, so you may be able to get
19991 started more quickly on a new system by using @code{gdbserver}.
19992 Finally, if you develop code for real-time systems, you may find that
19993 the tradeoffs involved in real-time operation make it more convenient to
19994 do as much development work as possible on another system, for example
19995 by cross-compiling. You can use @code{gdbserver} to make a similar
19996 choice for debugging.
19998 @value{GDBN} and @code{gdbserver} communicate via either a serial line
19999 or a TCP connection, using the standard @value{GDBN} remote serial
20003 @emph{Warning:} @code{gdbserver} does not have any built-in security.
20004 Do not run @code{gdbserver} connected to any public network; a
20005 @value{GDBN} connection to @code{gdbserver} provides access to the
20006 target system with the same privileges as the user running
20010 @anchor{Running gdbserver}
20011 @subsection Running @code{gdbserver}
20012 @cindex arguments, to @code{gdbserver}
20013 @cindex @code{gdbserver}, command-line arguments
20015 Run @code{gdbserver} on the target system. You need a copy of the
20016 program you want to debug, including any libraries it requires.
20017 @code{gdbserver} does not need your program's symbol table, so you can
20018 strip the program if necessary to save space. @value{GDBN} on the host
20019 system does all the symbol handling.
20021 To use the server, you must tell it how to communicate with @value{GDBN};
20022 the name of your program; and the arguments for your program. The usual
20026 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
20029 @var{comm} is either a device name (to use a serial line), or a TCP
20030 hostname and portnumber, or @code{-} or @code{stdio} to use
20031 stdin/stdout of @code{gdbserver}.
20032 For example, to debug Emacs with the argument
20033 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
20037 target> gdbserver /dev/com1 emacs foo.txt
20040 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
20043 To use a TCP connection instead of a serial line:
20046 target> gdbserver host:2345 emacs foo.txt
20049 The only difference from the previous example is the first argument,
20050 specifying that you are communicating with the host @value{GDBN} via
20051 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
20052 expect a TCP connection from machine @samp{host} to local TCP port 2345.
20053 (Currently, the @samp{host} part is ignored.) You can choose any number
20054 you want for the port number as long as it does not conflict with any
20055 TCP ports already in use on the target system (for example, @code{23} is
20056 reserved for @code{telnet}).@footnote{If you choose a port number that
20057 conflicts with another service, @code{gdbserver} prints an error message
20058 and exits.} You must use the same port number with the host @value{GDBN}
20059 @code{target remote} command.
20061 The @code{stdio} connection is useful when starting @code{gdbserver}
20065 (gdb) target remote | ssh -T hostname gdbserver - hello
20068 The @samp{-T} option to ssh is provided because we don't need a remote pty,
20069 and we don't want escape-character handling. Ssh does this by default when
20070 a command is provided, the flag is provided to make it explicit.
20071 You could elide it if you want to.
20073 Programs started with stdio-connected gdbserver have @file{/dev/null} for
20074 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
20075 display through a pipe connected to gdbserver.
20076 Both @code{stdout} and @code{stderr} use the same pipe.
20078 @anchor{Attaching to a program}
20079 @subsubsection Attaching to a Running Program
20080 @cindex attach to a program, @code{gdbserver}
20081 @cindex @option{--attach}, @code{gdbserver} option
20083 On some targets, @code{gdbserver} can also attach to running programs.
20084 This is accomplished via the @code{--attach} argument. The syntax is:
20087 target> gdbserver --attach @var{comm} @var{pid}
20090 @var{pid} is the process ID of a currently running process. It isn't
20091 necessary to point @code{gdbserver} at a binary for the running process.
20093 In @code{target extended-remote} mode, you can also attach using the
20094 @value{GDBN} attach command
20095 (@pxref{Attaching in Types of Remote Connections}).
20098 You can debug processes by name instead of process ID if your target has the
20099 @code{pidof} utility:
20102 target> gdbserver --attach @var{comm} `pidof @var{program}`
20105 In case more than one copy of @var{program} is running, or @var{program}
20106 has multiple threads, most versions of @code{pidof} support the
20107 @code{-s} option to only return the first process ID.
20109 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
20111 This section applies only when @code{gdbserver} is run to listen on a TCP
20114 @code{gdbserver} normally terminates after all of its debugged processes have
20115 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
20116 extended-remote}, @code{gdbserver} stays running even with no processes left.
20117 @value{GDBN} normally terminates the spawned debugged process on its exit,
20118 which normally also terminates @code{gdbserver} in the @kbd{target remote}
20119 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
20120 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
20121 stays running even in the @kbd{target remote} mode.
20123 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
20124 Such reconnecting is useful for features like @ref{disconnected tracing}. For
20125 completeness, at most one @value{GDBN} can be connected at a time.
20127 @cindex @option{--once}, @code{gdbserver} option
20128 By default, @code{gdbserver} keeps the listening TCP port open, so that
20129 subsequent connections are possible. However, if you start @code{gdbserver}
20130 with the @option{--once} option, it will stop listening for any further
20131 connection attempts after connecting to the first @value{GDBN} session. This
20132 means no further connections to @code{gdbserver} will be possible after the
20133 first one. It also means @code{gdbserver} will terminate after the first
20134 connection with remote @value{GDBN} has closed, even for unexpectedly closed
20135 connections and even in the @kbd{target extended-remote} mode. The
20136 @option{--once} option allows reusing the same port number for connecting to
20137 multiple instances of @code{gdbserver} running on the same host, since each
20138 instance closes its port after the first connection.
20140 @anchor{Other Command-Line Arguments for gdbserver}
20141 @subsubsection Other Command-Line Arguments for @code{gdbserver}
20143 You can use the @option{--multi} option to start @code{gdbserver} without
20144 specifying a program to debug or a process to attach to. Then you can
20145 attach in @code{target extended-remote} mode and run or attach to a
20146 program. For more information,
20147 @pxref{--multi Option in Types of Remote Connnections}.
20149 @cindex @option{--debug}, @code{gdbserver} option
20150 The @option{--debug} option tells @code{gdbserver} to display extra
20151 status information about the debugging process.
20152 @cindex @option{--remote-debug}, @code{gdbserver} option
20153 The @option{--remote-debug} option tells @code{gdbserver} to display
20154 remote protocol debug output. These options are intended for
20155 @code{gdbserver} development and for bug reports to the developers.
20157 @cindex @option{--debug-format}, @code{gdbserver} option
20158 The @option{--debug-format=option1[,option2,...]} option tells
20159 @code{gdbserver} to include additional information in each output.
20160 Possible options are:
20164 Turn off all extra information in debugging output.
20166 Turn on all extra information in debugging output.
20168 Include a timestamp in each line of debugging output.
20171 Options are processed in order. Thus, for example, if @option{none}
20172 appears last then no additional information is added to debugging output.
20174 @cindex @option{--wrapper}, @code{gdbserver} option
20175 The @option{--wrapper} option specifies a wrapper to launch programs
20176 for debugging. The option should be followed by the name of the
20177 wrapper, then any command-line arguments to pass to the wrapper, then
20178 @kbd{--} indicating the end of the wrapper arguments.
20180 @code{gdbserver} runs the specified wrapper program with a combined
20181 command line including the wrapper arguments, then the name of the
20182 program to debug, then any arguments to the program. The wrapper
20183 runs until it executes your program, and then @value{GDBN} gains control.
20185 You can use any program that eventually calls @code{execve} with
20186 its arguments as a wrapper. Several standard Unix utilities do
20187 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
20188 with @code{exec "$@@"} will also work.
20190 For example, you can use @code{env} to pass an environment variable to
20191 the debugged program, without setting the variable in @code{gdbserver}'s
20195 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
20198 @subsection Connecting to @code{gdbserver}
20200 The basic procedure for connecting to the remote target is:
20204 Run @value{GDBN} on the host system.
20207 Make sure you have the necessary symbol files
20208 (@pxref{Host and target files}).
20209 Load symbols for your application using the @code{file} command before you
20210 connect. Use @code{set sysroot} to locate target libraries (unless your
20211 @value{GDBN} was compiled with the correct sysroot using
20212 @code{--with-sysroot}).
20215 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
20216 For TCP connections, you must start up @code{gdbserver} prior to using
20217 the @code{target} command. Otherwise you may get an error whose
20218 text depends on the host system, but which usually looks something like
20219 @samp{Connection refused}. Don't use the @code{load}
20220 command in @value{GDBN} when using @code{target remote} mode, since the
20221 program is already on the target.
20225 @anchor{Monitor Commands for gdbserver}
20226 @subsection Monitor Commands for @code{gdbserver}
20227 @cindex monitor commands, for @code{gdbserver}
20229 During a @value{GDBN} session using @code{gdbserver}, you can use the
20230 @code{monitor} command to send special requests to @code{gdbserver}.
20231 Here are the available commands.
20235 List the available monitor commands.
20237 @item monitor set debug 0
20238 @itemx monitor set debug 1
20239 Disable or enable general debugging messages.
20241 @item monitor set remote-debug 0
20242 @itemx monitor set remote-debug 1
20243 Disable or enable specific debugging messages associated with the remote
20244 protocol (@pxref{Remote Protocol}).
20246 @item monitor set debug-format option1@r{[},option2,...@r{]}
20247 Specify additional text to add to debugging messages.
20248 Possible options are:
20252 Turn off all extra information in debugging output.
20254 Turn on all extra information in debugging output.
20256 Include a timestamp in each line of debugging output.
20259 Options are processed in order. Thus, for example, if @option{none}
20260 appears last then no additional information is added to debugging output.
20262 @item monitor set libthread-db-search-path [PATH]
20263 @cindex gdbserver, search path for @code{libthread_db}
20264 When this command is issued, @var{path} is a colon-separated list of
20265 directories to search for @code{libthread_db} (@pxref{Threads,,set
20266 libthread-db-search-path}). If you omit @var{path},
20267 @samp{libthread-db-search-path} will be reset to its default value.
20269 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
20270 not supported in @code{gdbserver}.
20273 Tell gdbserver to exit immediately. This command should be followed by
20274 @code{disconnect} to close the debugging session. @code{gdbserver} will
20275 detach from any attached processes and kill any processes it created.
20276 Use @code{monitor exit} to terminate @code{gdbserver} at the end
20277 of a multi-process mode debug session.
20281 @subsection Tracepoints support in @code{gdbserver}
20282 @cindex tracepoints support in @code{gdbserver}
20284 On some targets, @code{gdbserver} supports tracepoints, fast
20285 tracepoints and static tracepoints.
20287 For fast or static tracepoints to work, a special library called the
20288 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
20289 This library is built and distributed as an integral part of
20290 @code{gdbserver}. In addition, support for static tracepoints
20291 requires building the in-process agent library with static tracepoints
20292 support. At present, the UST (LTTng Userspace Tracer,
20293 @url{http://lttng.org/ust}) tracing engine is supported. This support
20294 is automatically available if UST development headers are found in the
20295 standard include path when @code{gdbserver} is built, or if
20296 @code{gdbserver} was explicitly configured using @option{--with-ust}
20297 to point at such headers. You can explicitly disable the support
20298 using @option{--with-ust=no}.
20300 There are several ways to load the in-process agent in your program:
20303 @item Specifying it as dependency at link time
20305 You can link your program dynamically with the in-process agent
20306 library. On most systems, this is accomplished by adding
20307 @code{-linproctrace} to the link command.
20309 @item Using the system's preloading mechanisms
20311 You can force loading the in-process agent at startup time by using
20312 your system's support for preloading shared libraries. Many Unixes
20313 support the concept of preloading user defined libraries. In most
20314 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
20315 in the environment. See also the description of @code{gdbserver}'s
20316 @option{--wrapper} command line option.
20318 @item Using @value{GDBN} to force loading the agent at run time
20320 On some systems, you can force the inferior to load a shared library,
20321 by calling a dynamic loader function in the inferior that takes care
20322 of dynamically looking up and loading a shared library. On most Unix
20323 systems, the function is @code{dlopen}. You'll use the @code{call}
20324 command for that. For example:
20327 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
20330 Note that on most Unix systems, for the @code{dlopen} function to be
20331 available, the program needs to be linked with @code{-ldl}.
20334 On systems that have a userspace dynamic loader, like most Unix
20335 systems, when you connect to @code{gdbserver} using @code{target
20336 remote}, you'll find that the program is stopped at the dynamic
20337 loader's entry point, and no shared library has been loaded in the
20338 program's address space yet, including the in-process agent. In that
20339 case, before being able to use any of the fast or static tracepoints
20340 features, you need to let the loader run and load the shared
20341 libraries. The simplest way to do that is to run the program to the
20342 main procedure. E.g., if debugging a C or C@t{++} program, start
20343 @code{gdbserver} like so:
20346 $ gdbserver :9999 myprogram
20349 Start GDB and connect to @code{gdbserver} like so, and run to main:
20353 (@value{GDBP}) target remote myhost:9999
20354 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
20355 (@value{GDBP}) b main
20356 (@value{GDBP}) continue
20359 The in-process tracing agent library should now be loaded into the
20360 process; you can confirm it with the @code{info sharedlibrary}
20361 command, which will list @file{libinproctrace.so} as loaded in the
20362 process. You are now ready to install fast tracepoints, list static
20363 tracepoint markers, probe static tracepoints markers, and start
20366 @node Remote Configuration
20367 @section Remote Configuration
20370 @kindex show remote
20371 This section documents the configuration options available when
20372 debugging remote programs. For the options related to the File I/O
20373 extensions of the remote protocol, see @ref{system,
20374 system-call-allowed}.
20377 @item set remoteaddresssize @var{bits}
20378 @cindex address size for remote targets
20379 @cindex bits in remote address
20380 Set the maximum size of address in a memory packet to the specified
20381 number of bits. @value{GDBN} will mask off the address bits above
20382 that number, when it passes addresses to the remote target. The
20383 default value is the number of bits in the target's address.
20385 @item show remoteaddresssize
20386 Show the current value of remote address size in bits.
20388 @item set serial baud @var{n}
20389 @cindex baud rate for remote targets
20390 Set the baud rate for the remote serial I/O to @var{n} baud. The
20391 value is used to set the speed of the serial port used for debugging
20394 @item show serial baud
20395 Show the current speed of the remote connection.
20397 @item set serial parity @var{parity}
20398 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
20399 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
20401 @item show serial parity
20402 Show the current parity of the serial port.
20404 @item set remotebreak
20405 @cindex interrupt remote programs
20406 @cindex BREAK signal instead of Ctrl-C
20407 @anchor{set remotebreak}
20408 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
20409 when you type @kbd{Ctrl-c} to interrupt the program running
20410 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
20411 character instead. The default is off, since most remote systems
20412 expect to see @samp{Ctrl-C} as the interrupt signal.
20414 @item show remotebreak
20415 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
20416 interrupt the remote program.
20418 @item set remoteflow on
20419 @itemx set remoteflow off
20420 @kindex set remoteflow
20421 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
20422 on the serial port used to communicate to the remote target.
20424 @item show remoteflow
20425 @kindex show remoteflow
20426 Show the current setting of hardware flow control.
20428 @item set remotelogbase @var{base}
20429 Set the base (a.k.a.@: radix) of logging serial protocol
20430 communications to @var{base}. Supported values of @var{base} are:
20431 @code{ascii}, @code{octal}, and @code{hex}. The default is
20434 @item show remotelogbase
20435 Show the current setting of the radix for logging remote serial
20438 @item set remotelogfile @var{file}
20439 @cindex record serial communications on file
20440 Record remote serial communications on the named @var{file}. The
20441 default is not to record at all.
20443 @item show remotelogfile.
20444 Show the current setting of the file name on which to record the
20445 serial communications.
20447 @item set remotetimeout @var{num}
20448 @cindex timeout for serial communications
20449 @cindex remote timeout
20450 Set the timeout limit to wait for the remote target to respond to
20451 @var{num} seconds. The default is 2 seconds.
20453 @item show remotetimeout
20454 Show the current number of seconds to wait for the remote target
20457 @cindex limit hardware breakpoints and watchpoints
20458 @cindex remote target, limit break- and watchpoints
20459 @anchor{set remote hardware-watchpoint-limit}
20460 @anchor{set remote hardware-breakpoint-limit}
20461 @item set remote hardware-watchpoint-limit @var{limit}
20462 @itemx set remote hardware-breakpoint-limit @var{limit}
20463 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
20464 watchpoints. A limit of -1, the default, is treated as unlimited.
20466 @cindex limit hardware watchpoints length
20467 @cindex remote target, limit watchpoints length
20468 @anchor{set remote hardware-watchpoint-length-limit}
20469 @item set remote hardware-watchpoint-length-limit @var{limit}
20470 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
20471 a remote hardware watchpoint. A limit of -1, the default, is treated
20474 @item show remote hardware-watchpoint-length-limit
20475 Show the current limit (in bytes) of the maximum length of
20476 a remote hardware watchpoint.
20478 @item set remote exec-file @var{filename}
20479 @itemx show remote exec-file
20480 @anchor{set remote exec-file}
20481 @cindex executable file, for remote target
20482 Select the file used for @code{run} with @code{target
20483 extended-remote}. This should be set to a filename valid on the
20484 target system. If it is not set, the target will use a default
20485 filename (e.g.@: the last program run).
20487 @item set remote interrupt-sequence
20488 @cindex interrupt remote programs
20489 @cindex select Ctrl-C, BREAK or BREAK-g
20490 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
20491 @samp{BREAK-g} as the
20492 sequence to the remote target in order to interrupt the execution.
20493 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
20494 is high level of serial line for some certain time.
20495 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
20496 It is @code{BREAK} signal followed by character @code{g}.
20498 @item show interrupt-sequence
20499 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
20500 is sent by @value{GDBN} to interrupt the remote program.
20501 @code{BREAK-g} is BREAK signal followed by @code{g} and
20502 also known as Magic SysRq g.
20504 @item set remote interrupt-on-connect
20505 @cindex send interrupt-sequence on start
20506 Specify whether interrupt-sequence is sent to remote target when
20507 @value{GDBN} connects to it. This is mostly needed when you debug
20508 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
20509 which is known as Magic SysRq g in order to connect @value{GDBN}.
20511 @item show interrupt-on-connect
20512 Show whether interrupt-sequence is sent
20513 to remote target when @value{GDBN} connects to it.
20517 @item set tcp auto-retry on
20518 @cindex auto-retry, for remote TCP target
20519 Enable auto-retry for remote TCP connections. This is useful if the remote
20520 debugging agent is launched in parallel with @value{GDBN}; there is a race
20521 condition because the agent may not become ready to accept the connection
20522 before @value{GDBN} attempts to connect. When auto-retry is
20523 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
20524 to establish the connection using the timeout specified by
20525 @code{set tcp connect-timeout}.
20527 @item set tcp auto-retry off
20528 Do not auto-retry failed TCP connections.
20530 @item show tcp auto-retry
20531 Show the current auto-retry setting.
20533 @item set tcp connect-timeout @var{seconds}
20534 @itemx set tcp connect-timeout unlimited
20535 @cindex connection timeout, for remote TCP target
20536 @cindex timeout, for remote target connection
20537 Set the timeout for establishing a TCP connection to the remote target to
20538 @var{seconds}. The timeout affects both polling to retry failed connections
20539 (enabled by @code{set tcp auto-retry on}) and waiting for connections
20540 that are merely slow to complete, and represents an approximate cumulative
20541 value. If @var{seconds} is @code{unlimited}, there is no timeout and
20542 @value{GDBN} will keep attempting to establish a connection forever,
20543 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
20545 @item show tcp connect-timeout
20546 Show the current connection timeout setting.
20549 @cindex remote packets, enabling and disabling
20550 The @value{GDBN} remote protocol autodetects the packets supported by
20551 your debugging stub. If you need to override the autodetection, you
20552 can use these commands to enable or disable individual packets. Each
20553 packet can be set to @samp{on} (the remote target supports this
20554 packet), @samp{off} (the remote target does not support this packet),
20555 or @samp{auto} (detect remote target support for this packet). They
20556 all default to @samp{auto}. For more information about each packet,
20557 see @ref{Remote Protocol}.
20559 During normal use, you should not have to use any of these commands.
20560 If you do, that may be a bug in your remote debugging stub, or a bug
20561 in @value{GDBN}. You may want to report the problem to the
20562 @value{GDBN} developers.
20564 For each packet @var{name}, the command to enable or disable the
20565 packet is @code{set remote @var{name}-packet}. The available settings
20568 @multitable @columnfractions 0.28 0.32 0.25
20571 @tab Related Features
20573 @item @code{fetch-register}
20575 @tab @code{info registers}
20577 @item @code{set-register}
20581 @item @code{binary-download}
20583 @tab @code{load}, @code{set}
20585 @item @code{read-aux-vector}
20586 @tab @code{qXfer:auxv:read}
20587 @tab @code{info auxv}
20589 @item @code{symbol-lookup}
20590 @tab @code{qSymbol}
20591 @tab Detecting multiple threads
20593 @item @code{attach}
20594 @tab @code{vAttach}
20597 @item @code{verbose-resume}
20599 @tab Stepping or resuming multiple threads
20605 @item @code{software-breakpoint}
20609 @item @code{hardware-breakpoint}
20613 @item @code{write-watchpoint}
20617 @item @code{read-watchpoint}
20621 @item @code{access-watchpoint}
20625 @item @code{pid-to-exec-file}
20626 @tab @code{qXfer:exec-file:read}
20627 @tab @code{attach}, @code{run}
20629 @item @code{target-features}
20630 @tab @code{qXfer:features:read}
20631 @tab @code{set architecture}
20633 @item @code{library-info}
20634 @tab @code{qXfer:libraries:read}
20635 @tab @code{info sharedlibrary}
20637 @item @code{memory-map}
20638 @tab @code{qXfer:memory-map:read}
20639 @tab @code{info mem}
20641 @item @code{read-sdata-object}
20642 @tab @code{qXfer:sdata:read}
20643 @tab @code{print $_sdata}
20645 @item @code{read-spu-object}
20646 @tab @code{qXfer:spu:read}
20647 @tab @code{info spu}
20649 @item @code{write-spu-object}
20650 @tab @code{qXfer:spu:write}
20651 @tab @code{info spu}
20653 @item @code{read-siginfo-object}
20654 @tab @code{qXfer:siginfo:read}
20655 @tab @code{print $_siginfo}
20657 @item @code{write-siginfo-object}
20658 @tab @code{qXfer:siginfo:write}
20659 @tab @code{set $_siginfo}
20661 @item @code{threads}
20662 @tab @code{qXfer:threads:read}
20663 @tab @code{info threads}
20665 @item @code{get-thread-local-@*storage-address}
20666 @tab @code{qGetTLSAddr}
20667 @tab Displaying @code{__thread} variables
20669 @item @code{get-thread-information-block-address}
20670 @tab @code{qGetTIBAddr}
20671 @tab Display MS-Windows Thread Information Block.
20673 @item @code{search-memory}
20674 @tab @code{qSearch:memory}
20677 @item @code{supported-packets}
20678 @tab @code{qSupported}
20679 @tab Remote communications parameters
20681 @item @code{catch-syscalls}
20682 @tab @code{QCatchSyscalls}
20683 @tab @code{catch syscall}
20685 @item @code{pass-signals}
20686 @tab @code{QPassSignals}
20687 @tab @code{handle @var{signal}}
20689 @item @code{program-signals}
20690 @tab @code{QProgramSignals}
20691 @tab @code{handle @var{signal}}
20693 @item @code{hostio-close-packet}
20694 @tab @code{vFile:close}
20695 @tab @code{remote get}, @code{remote put}
20697 @item @code{hostio-open-packet}
20698 @tab @code{vFile:open}
20699 @tab @code{remote get}, @code{remote put}
20701 @item @code{hostio-pread-packet}
20702 @tab @code{vFile:pread}
20703 @tab @code{remote get}, @code{remote put}
20705 @item @code{hostio-pwrite-packet}
20706 @tab @code{vFile:pwrite}
20707 @tab @code{remote get}, @code{remote put}
20709 @item @code{hostio-unlink-packet}
20710 @tab @code{vFile:unlink}
20711 @tab @code{remote delete}
20713 @item @code{hostio-readlink-packet}
20714 @tab @code{vFile:readlink}
20717 @item @code{hostio-fstat-packet}
20718 @tab @code{vFile:fstat}
20721 @item @code{hostio-setfs-packet}
20722 @tab @code{vFile:setfs}
20725 @item @code{noack-packet}
20726 @tab @code{QStartNoAckMode}
20727 @tab Packet acknowledgment
20729 @item @code{osdata}
20730 @tab @code{qXfer:osdata:read}
20731 @tab @code{info os}
20733 @item @code{query-attached}
20734 @tab @code{qAttached}
20735 @tab Querying remote process attach state.
20737 @item @code{trace-buffer-size}
20738 @tab @code{QTBuffer:size}
20739 @tab @code{set trace-buffer-size}
20741 @item @code{trace-status}
20742 @tab @code{qTStatus}
20743 @tab @code{tstatus}
20745 @item @code{traceframe-info}
20746 @tab @code{qXfer:traceframe-info:read}
20747 @tab Traceframe info
20749 @item @code{install-in-trace}
20750 @tab @code{InstallInTrace}
20751 @tab Install tracepoint in tracing
20753 @item @code{disable-randomization}
20754 @tab @code{QDisableRandomization}
20755 @tab @code{set disable-randomization}
20757 @item @code{conditional-breakpoints-packet}
20758 @tab @code{Z0 and Z1}
20759 @tab @code{Support for target-side breakpoint condition evaluation}
20761 @item @code{multiprocess-extensions}
20762 @tab @code{multiprocess extensions}
20763 @tab Debug multiple processes and remote process PID awareness
20765 @item @code{swbreak-feature}
20766 @tab @code{swbreak stop reason}
20769 @item @code{hwbreak-feature}
20770 @tab @code{hwbreak stop reason}
20773 @item @code{fork-event-feature}
20774 @tab @code{fork stop reason}
20777 @item @code{vfork-event-feature}
20778 @tab @code{vfork stop reason}
20781 @item @code{exec-event-feature}
20782 @tab @code{exec stop reason}
20785 @item @code{thread-events}
20786 @tab @code{QThreadEvents}
20787 @tab Tracking thread lifetime.
20789 @item @code{no-resumed-stop-reply}
20790 @tab @code{no resumed thread left stop reply}
20791 @tab Tracking thread lifetime.
20796 @section Implementing a Remote Stub
20798 @cindex debugging stub, example
20799 @cindex remote stub, example
20800 @cindex stub example, remote debugging
20801 The stub files provided with @value{GDBN} implement the target side of the
20802 communication protocol, and the @value{GDBN} side is implemented in the
20803 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
20804 these subroutines to communicate, and ignore the details. (If you're
20805 implementing your own stub file, you can still ignore the details: start
20806 with one of the existing stub files. @file{sparc-stub.c} is the best
20807 organized, and therefore the easiest to read.)
20809 @cindex remote serial debugging, overview
20810 To debug a program running on another machine (the debugging
20811 @dfn{target} machine), you must first arrange for all the usual
20812 prerequisites for the program to run by itself. For example, for a C
20817 A startup routine to set up the C runtime environment; these usually
20818 have a name like @file{crt0}. The startup routine may be supplied by
20819 your hardware supplier, or you may have to write your own.
20822 A C subroutine library to support your program's
20823 subroutine calls, notably managing input and output.
20826 A way of getting your program to the other machine---for example, a
20827 download program. These are often supplied by the hardware
20828 manufacturer, but you may have to write your own from hardware
20832 The next step is to arrange for your program to use a serial port to
20833 communicate with the machine where @value{GDBN} is running (the @dfn{host}
20834 machine). In general terms, the scheme looks like this:
20838 @value{GDBN} already understands how to use this protocol; when everything
20839 else is set up, you can simply use the @samp{target remote} command
20840 (@pxref{Targets,,Specifying a Debugging Target}).
20842 @item On the target,
20843 you must link with your program a few special-purpose subroutines that
20844 implement the @value{GDBN} remote serial protocol. The file containing these
20845 subroutines is called a @dfn{debugging stub}.
20847 On certain remote targets, you can use an auxiliary program
20848 @code{gdbserver} instead of linking a stub into your program.
20849 @xref{Server,,Using the @code{gdbserver} Program}, for details.
20852 The debugging stub is specific to the architecture of the remote
20853 machine; for example, use @file{sparc-stub.c} to debug programs on
20856 @cindex remote serial stub list
20857 These working remote stubs are distributed with @value{GDBN}:
20862 @cindex @file{i386-stub.c}
20865 For Intel 386 and compatible architectures.
20868 @cindex @file{m68k-stub.c}
20869 @cindex Motorola 680x0
20871 For Motorola 680x0 architectures.
20874 @cindex @file{sh-stub.c}
20877 For Renesas SH architectures.
20880 @cindex @file{sparc-stub.c}
20882 For @sc{sparc} architectures.
20884 @item sparcl-stub.c
20885 @cindex @file{sparcl-stub.c}
20888 For Fujitsu @sc{sparclite} architectures.
20892 The @file{README} file in the @value{GDBN} distribution may list other
20893 recently added stubs.
20896 * Stub Contents:: What the stub can do for you
20897 * Bootstrapping:: What you must do for the stub
20898 * Debug Session:: Putting it all together
20901 @node Stub Contents
20902 @subsection What the Stub Can Do for You
20904 @cindex remote serial stub
20905 The debugging stub for your architecture supplies these three
20909 @item set_debug_traps
20910 @findex set_debug_traps
20911 @cindex remote serial stub, initialization
20912 This routine arranges for @code{handle_exception} to run when your
20913 program stops. You must call this subroutine explicitly in your
20914 program's startup code.
20916 @item handle_exception
20917 @findex handle_exception
20918 @cindex remote serial stub, main routine
20919 This is the central workhorse, but your program never calls it
20920 explicitly---the setup code arranges for @code{handle_exception} to
20921 run when a trap is triggered.
20923 @code{handle_exception} takes control when your program stops during
20924 execution (for example, on a breakpoint), and mediates communications
20925 with @value{GDBN} on the host machine. This is where the communications
20926 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
20927 representative on the target machine. It begins by sending summary
20928 information on the state of your program, then continues to execute,
20929 retrieving and transmitting any information @value{GDBN} needs, until you
20930 execute a @value{GDBN} command that makes your program resume; at that point,
20931 @code{handle_exception} returns control to your own code on the target
20935 @cindex @code{breakpoint} subroutine, remote
20936 Use this auxiliary subroutine to make your program contain a
20937 breakpoint. Depending on the particular situation, this may be the only
20938 way for @value{GDBN} to get control. For instance, if your target
20939 machine has some sort of interrupt button, you won't need to call this;
20940 pressing the interrupt button transfers control to
20941 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
20942 simply receiving characters on the serial port may also trigger a trap;
20943 again, in that situation, you don't need to call @code{breakpoint} from
20944 your own program---simply running @samp{target remote} from the host
20945 @value{GDBN} session gets control.
20947 Call @code{breakpoint} if none of these is true, or if you simply want
20948 to make certain your program stops at a predetermined point for the
20949 start of your debugging session.
20952 @node Bootstrapping
20953 @subsection What You Must Do for the Stub
20955 @cindex remote stub, support routines
20956 The debugging stubs that come with @value{GDBN} are set up for a particular
20957 chip architecture, but they have no information about the rest of your
20958 debugging target machine.
20960 First of all you need to tell the stub how to communicate with the
20964 @item int getDebugChar()
20965 @findex getDebugChar
20966 Write this subroutine to read a single character from the serial port.
20967 It may be identical to @code{getchar} for your target system; a
20968 different name is used to allow you to distinguish the two if you wish.
20970 @item void putDebugChar(int)
20971 @findex putDebugChar
20972 Write this subroutine to write a single character to the serial port.
20973 It may be identical to @code{putchar} for your target system; a
20974 different name is used to allow you to distinguish the two if you wish.
20977 @cindex control C, and remote debugging
20978 @cindex interrupting remote targets
20979 If you want @value{GDBN} to be able to stop your program while it is
20980 running, you need to use an interrupt-driven serial driver, and arrange
20981 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
20982 character). That is the character which @value{GDBN} uses to tell the
20983 remote system to stop.
20985 Getting the debugging target to return the proper status to @value{GDBN}
20986 probably requires changes to the standard stub; one quick and dirty way
20987 is to just execute a breakpoint instruction (the ``dirty'' part is that
20988 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
20990 Other routines you need to supply are:
20993 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
20994 @findex exceptionHandler
20995 Write this function to install @var{exception_address} in the exception
20996 handling tables. You need to do this because the stub does not have any
20997 way of knowing what the exception handling tables on your target system
20998 are like (for example, the processor's table might be in @sc{rom},
20999 containing entries which point to a table in @sc{ram}).
21000 The @var{exception_number} specifies the exception which should be changed;
21001 its meaning is architecture-dependent (for example, different numbers
21002 might represent divide by zero, misaligned access, etc). When this
21003 exception occurs, control should be transferred directly to
21004 @var{exception_address}, and the processor state (stack, registers,
21005 and so on) should be just as it is when a processor exception occurs. So if
21006 you want to use a jump instruction to reach @var{exception_address}, it
21007 should be a simple jump, not a jump to subroutine.
21009 For the 386, @var{exception_address} should be installed as an interrupt
21010 gate so that interrupts are masked while the handler runs. The gate
21011 should be at privilege level 0 (the most privileged level). The
21012 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
21013 help from @code{exceptionHandler}.
21015 @item void flush_i_cache()
21016 @findex flush_i_cache
21017 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
21018 instruction cache, if any, on your target machine. If there is no
21019 instruction cache, this subroutine may be a no-op.
21021 On target machines that have instruction caches, @value{GDBN} requires this
21022 function to make certain that the state of your program is stable.
21026 You must also make sure this library routine is available:
21029 @item void *memset(void *, int, int)
21031 This is the standard library function @code{memset} that sets an area of
21032 memory to a known value. If you have one of the free versions of
21033 @code{libc.a}, @code{memset} can be found there; otherwise, you must
21034 either obtain it from your hardware manufacturer, or write your own.
21037 If you do not use the GNU C compiler, you may need other standard
21038 library subroutines as well; this varies from one stub to another,
21039 but in general the stubs are likely to use any of the common library
21040 subroutines which @code{@value{NGCC}} generates as inline code.
21043 @node Debug Session
21044 @subsection Putting it All Together
21046 @cindex remote serial debugging summary
21047 In summary, when your program is ready to debug, you must follow these
21052 Make sure you have defined the supporting low-level routines
21053 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
21055 @code{getDebugChar}, @code{putDebugChar},
21056 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
21060 Insert these lines in your program's startup code, before the main
21061 procedure is called:
21068 On some machines, when a breakpoint trap is raised, the hardware
21069 automatically makes the PC point to the instruction after the
21070 breakpoint. If your machine doesn't do that, you may need to adjust
21071 @code{handle_exception} to arrange for it to return to the instruction
21072 after the breakpoint on this first invocation, so that your program
21073 doesn't keep hitting the initial breakpoint instead of making
21077 For the 680x0 stub only, you need to provide a variable called
21078 @code{exceptionHook}. Normally you just use:
21081 void (*exceptionHook)() = 0;
21085 but if before calling @code{set_debug_traps}, you set it to point to a
21086 function in your program, that function is called when
21087 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
21088 error). The function indicated by @code{exceptionHook} is called with
21089 one parameter: an @code{int} which is the exception number.
21092 Compile and link together: your program, the @value{GDBN} debugging stub for
21093 your target architecture, and the supporting subroutines.
21096 Make sure you have a serial connection between your target machine and
21097 the @value{GDBN} host, and identify the serial port on the host.
21100 @c The "remote" target now provides a `load' command, so we should
21101 @c document that. FIXME.
21102 Download your program to your target machine (or get it there by
21103 whatever means the manufacturer provides), and start it.
21106 Start @value{GDBN} on the host, and connect to the target
21107 (@pxref{Connecting,,Connecting to a Remote Target}).
21111 @node Configurations
21112 @chapter Configuration-Specific Information
21114 While nearly all @value{GDBN} commands are available for all native and
21115 cross versions of the debugger, there are some exceptions. This chapter
21116 describes things that are only available in certain configurations.
21118 There are three major categories of configurations: native
21119 configurations, where the host and target are the same, embedded
21120 operating system configurations, which are usually the same for several
21121 different processor architectures, and bare embedded processors, which
21122 are quite different from each other.
21127 * Embedded Processors::
21134 This section describes details specific to particular native
21138 * BSD libkvm Interface:: Debugging BSD kernel memory images
21139 * SVR4 Process Information:: SVR4 process information
21140 * DJGPP Native:: Features specific to the DJGPP port
21141 * Cygwin Native:: Features specific to the Cygwin port
21142 * Hurd Native:: Features specific to @sc{gnu} Hurd
21143 * Darwin:: Features specific to Darwin
21146 @node BSD libkvm Interface
21147 @subsection BSD libkvm Interface
21150 @cindex kernel memory image
21151 @cindex kernel crash dump
21153 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
21154 interface that provides a uniform interface for accessing kernel virtual
21155 memory images, including live systems and crash dumps. @value{GDBN}
21156 uses this interface to allow you to debug live kernels and kernel crash
21157 dumps on many native BSD configurations. This is implemented as a
21158 special @code{kvm} debugging target. For debugging a live system, load
21159 the currently running kernel into @value{GDBN} and connect to the
21163 (@value{GDBP}) @b{target kvm}
21166 For debugging crash dumps, provide the file name of the crash dump as an
21170 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
21173 Once connected to the @code{kvm} target, the following commands are
21179 Set current context from the @dfn{Process Control Block} (PCB) address.
21182 Set current context from proc address. This command isn't available on
21183 modern FreeBSD systems.
21186 @node SVR4 Process Information
21187 @subsection SVR4 Process Information
21189 @cindex examine process image
21190 @cindex process info via @file{/proc}
21192 Many versions of SVR4 and compatible systems provide a facility called
21193 @samp{/proc} that can be used to examine the image of a running
21194 process using file-system subroutines.
21196 If @value{GDBN} is configured for an operating system with this
21197 facility, the command @code{info proc} is available to report
21198 information about the process running your program, or about any
21199 process running on your system. This includes, as of this writing,
21200 @sc{gnu}/Linux and Solaris, for example.
21202 This command may also work on core files that were created on a system
21203 that has the @samp{/proc} facility.
21209 @itemx info proc @var{process-id}
21210 Summarize available information about any running process. If a
21211 process ID is specified by @var{process-id}, display information about
21212 that process; otherwise display information about the program being
21213 debugged. The summary includes the debugged process ID, the command
21214 line used to invoke it, its current working directory, and its
21215 executable file's absolute file name.
21217 On some systems, @var{process-id} can be of the form
21218 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
21219 within a process. If the optional @var{pid} part is missing, it means
21220 a thread from the process being debugged (the leading @samp{/} still
21221 needs to be present, or else @value{GDBN} will interpret the number as
21222 a process ID rather than a thread ID).
21224 @item info proc cmdline
21225 @cindex info proc cmdline
21226 Show the original command line of the process. This command is
21227 specific to @sc{gnu}/Linux.
21229 @item info proc cwd
21230 @cindex info proc cwd
21231 Show the current working directory of the process. This command is
21232 specific to @sc{gnu}/Linux.
21234 @item info proc exe
21235 @cindex info proc exe
21236 Show the name of executable of the process. This command is specific
21239 @item info proc mappings
21240 @cindex memory address space mappings
21241 Report the memory address space ranges accessible in the program, with
21242 information on whether the process has read, write, or execute access
21243 rights to each range. On @sc{gnu}/Linux systems, each memory range
21244 includes the object file which is mapped to that range, instead of the
21245 memory access rights to that range.
21247 @item info proc stat
21248 @itemx info proc status
21249 @cindex process detailed status information
21250 These subcommands are specific to @sc{gnu}/Linux systems. They show
21251 the process-related information, including the user ID and group ID;
21252 how many threads are there in the process; its virtual memory usage;
21253 the signals that are pending, blocked, and ignored; its TTY; its
21254 consumption of system and user time; its stack size; its @samp{nice}
21255 value; etc. For more information, see the @samp{proc} man page
21256 (type @kbd{man 5 proc} from your shell prompt).
21258 @item info proc all
21259 Show all the information about the process described under all of the
21260 above @code{info proc} subcommands.
21263 @comment These sub-options of 'info proc' were not included when
21264 @comment procfs.c was re-written. Keep their descriptions around
21265 @comment against the day when someone finds the time to put them back in.
21266 @kindex info proc times
21267 @item info proc times
21268 Starting time, user CPU time, and system CPU time for your program and
21271 @kindex info proc id
21273 Report on the process IDs related to your program: its own process ID,
21274 the ID of its parent, the process group ID, and the session ID.
21277 @item set procfs-trace
21278 @kindex set procfs-trace
21279 @cindex @code{procfs} API calls
21280 This command enables and disables tracing of @code{procfs} API calls.
21282 @item show procfs-trace
21283 @kindex show procfs-trace
21284 Show the current state of @code{procfs} API call tracing.
21286 @item set procfs-file @var{file}
21287 @kindex set procfs-file
21288 Tell @value{GDBN} to write @code{procfs} API trace to the named
21289 @var{file}. @value{GDBN} appends the trace info to the previous
21290 contents of the file. The default is to display the trace on the
21293 @item show procfs-file
21294 @kindex show procfs-file
21295 Show the file to which @code{procfs} API trace is written.
21297 @item proc-trace-entry
21298 @itemx proc-trace-exit
21299 @itemx proc-untrace-entry
21300 @itemx proc-untrace-exit
21301 @kindex proc-trace-entry
21302 @kindex proc-trace-exit
21303 @kindex proc-untrace-entry
21304 @kindex proc-untrace-exit
21305 These commands enable and disable tracing of entries into and exits
21306 from the @code{syscall} interface.
21309 @kindex info pidlist
21310 @cindex process list, QNX Neutrino
21311 For QNX Neutrino only, this command displays the list of all the
21312 processes and all the threads within each process.
21315 @kindex info meminfo
21316 @cindex mapinfo list, QNX Neutrino
21317 For QNX Neutrino only, this command displays the list of all mapinfos.
21321 @subsection Features for Debugging @sc{djgpp} Programs
21322 @cindex @sc{djgpp} debugging
21323 @cindex native @sc{djgpp} debugging
21324 @cindex MS-DOS-specific commands
21327 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
21328 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
21329 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
21330 top of real-mode DOS systems and their emulations.
21332 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
21333 defines a few commands specific to the @sc{djgpp} port. This
21334 subsection describes those commands.
21339 This is a prefix of @sc{djgpp}-specific commands which print
21340 information about the target system and important OS structures.
21343 @cindex MS-DOS system info
21344 @cindex free memory information (MS-DOS)
21345 @item info dos sysinfo
21346 This command displays assorted information about the underlying
21347 platform: the CPU type and features, the OS version and flavor, the
21348 DPMI version, and the available conventional and DPMI memory.
21353 @cindex segment descriptor tables
21354 @cindex descriptor tables display
21356 @itemx info dos ldt
21357 @itemx info dos idt
21358 These 3 commands display entries from, respectively, Global, Local,
21359 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
21360 tables are data structures which store a descriptor for each segment
21361 that is currently in use. The segment's selector is an index into a
21362 descriptor table; the table entry for that index holds the
21363 descriptor's base address and limit, and its attributes and access
21366 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
21367 segment (used for both data and the stack), and a DOS segment (which
21368 allows access to DOS/BIOS data structures and absolute addresses in
21369 conventional memory). However, the DPMI host will usually define
21370 additional segments in order to support the DPMI environment.
21372 @cindex garbled pointers
21373 These commands allow to display entries from the descriptor tables.
21374 Without an argument, all entries from the specified table are
21375 displayed. An argument, which should be an integer expression, means
21376 display a single entry whose index is given by the argument. For
21377 example, here's a convenient way to display information about the
21378 debugged program's data segment:
21381 @exdent @code{(@value{GDBP}) info dos ldt $ds}
21382 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
21386 This comes in handy when you want to see whether a pointer is outside
21387 the data segment's limit (i.e.@: @dfn{garbled}).
21389 @cindex page tables display (MS-DOS)
21391 @itemx info dos pte
21392 These two commands display entries from, respectively, the Page
21393 Directory and the Page Tables. Page Directories and Page Tables are
21394 data structures which control how virtual memory addresses are mapped
21395 into physical addresses. A Page Table includes an entry for every
21396 page of memory that is mapped into the program's address space; there
21397 may be several Page Tables, each one holding up to 4096 entries. A
21398 Page Directory has up to 4096 entries, one each for every Page Table
21399 that is currently in use.
21401 Without an argument, @kbd{info dos pde} displays the entire Page
21402 Directory, and @kbd{info dos pte} displays all the entries in all of
21403 the Page Tables. An argument, an integer expression, given to the
21404 @kbd{info dos pde} command means display only that entry from the Page
21405 Directory table. An argument given to the @kbd{info dos pte} command
21406 means display entries from a single Page Table, the one pointed to by
21407 the specified entry in the Page Directory.
21409 @cindex direct memory access (DMA) on MS-DOS
21410 These commands are useful when your program uses @dfn{DMA} (Direct
21411 Memory Access), which needs physical addresses to program the DMA
21414 These commands are supported only with some DPMI servers.
21416 @cindex physical address from linear address
21417 @item info dos address-pte @var{addr}
21418 This command displays the Page Table entry for a specified linear
21419 address. The argument @var{addr} is a linear address which should
21420 already have the appropriate segment's base address added to it,
21421 because this command accepts addresses which may belong to @emph{any}
21422 segment. For example, here's how to display the Page Table entry for
21423 the page where a variable @code{i} is stored:
21426 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
21427 @exdent @code{Page Table entry for address 0x11a00d30:}
21428 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
21432 This says that @code{i} is stored at offset @code{0xd30} from the page
21433 whose physical base address is @code{0x02698000}, and shows all the
21434 attributes of that page.
21436 Note that you must cast the addresses of variables to a @code{char *},
21437 since otherwise the value of @code{__djgpp_base_address}, the base
21438 address of all variables and functions in a @sc{djgpp} program, will
21439 be added using the rules of C pointer arithmetics: if @code{i} is
21440 declared an @code{int}, @value{GDBN} will add 4 times the value of
21441 @code{__djgpp_base_address} to the address of @code{i}.
21443 Here's another example, it displays the Page Table entry for the
21447 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
21448 @exdent @code{Page Table entry for address 0x29110:}
21449 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
21453 (The @code{+ 3} offset is because the transfer buffer's address is the
21454 3rd member of the @code{_go32_info_block} structure.) The output
21455 clearly shows that this DPMI server maps the addresses in conventional
21456 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
21457 linear (@code{0x29110}) addresses are identical.
21459 This command is supported only with some DPMI servers.
21462 @cindex DOS serial data link, remote debugging
21463 In addition to native debugging, the DJGPP port supports remote
21464 debugging via a serial data link. The following commands are specific
21465 to remote serial debugging in the DJGPP port of @value{GDBN}.
21468 @kindex set com1base
21469 @kindex set com1irq
21470 @kindex set com2base
21471 @kindex set com2irq
21472 @kindex set com3base
21473 @kindex set com3irq
21474 @kindex set com4base
21475 @kindex set com4irq
21476 @item set com1base @var{addr}
21477 This command sets the base I/O port address of the @file{COM1} serial
21480 @item set com1irq @var{irq}
21481 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
21482 for the @file{COM1} serial port.
21484 There are similar commands @samp{set com2base}, @samp{set com3irq},
21485 etc.@: for setting the port address and the @code{IRQ} lines for the
21488 @kindex show com1base
21489 @kindex show com1irq
21490 @kindex show com2base
21491 @kindex show com2irq
21492 @kindex show com3base
21493 @kindex show com3irq
21494 @kindex show com4base
21495 @kindex show com4irq
21496 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
21497 display the current settings of the base address and the @code{IRQ}
21498 lines used by the COM ports.
21501 @kindex info serial
21502 @cindex DOS serial port status
21503 This command prints the status of the 4 DOS serial ports. For each
21504 port, it prints whether it's active or not, its I/O base address and
21505 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
21506 counts of various errors encountered so far.
21510 @node Cygwin Native
21511 @subsection Features for Debugging MS Windows PE Executables
21512 @cindex MS Windows debugging
21513 @cindex native Cygwin debugging
21514 @cindex Cygwin-specific commands
21516 @value{GDBN} supports native debugging of MS Windows programs, including
21517 DLLs with and without symbolic debugging information.
21519 @cindex Ctrl-BREAK, MS-Windows
21520 @cindex interrupt debuggee on MS-Windows
21521 MS-Windows programs that call @code{SetConsoleMode} to switch off the
21522 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
21523 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
21524 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
21525 sequence, which can be used to interrupt the debuggee even if it
21528 There are various additional Cygwin-specific commands, described in
21529 this section. Working with DLLs that have no debugging symbols is
21530 described in @ref{Non-debug DLL Symbols}.
21535 This is a prefix of MS Windows-specific commands which print
21536 information about the target system and important OS structures.
21538 @item info w32 selector
21539 This command displays information returned by
21540 the Win32 API @code{GetThreadSelectorEntry} function.
21541 It takes an optional argument that is evaluated to
21542 a long value to give the information about this given selector.
21543 Without argument, this command displays information
21544 about the six segment registers.
21546 @item info w32 thread-information-block
21547 This command displays thread specific information stored in the
21548 Thread Information Block (readable on the X86 CPU family using @code{$fs}
21549 selector for 32-bit programs and @code{$gs} for 64-bit programs).
21551 @kindex signal-event
21552 @item signal-event @var{id}
21553 This command signals an event with user-provided @var{id}. Used to resume
21554 crashing process when attached to it using MS-Windows JIT debugging (AeDebug).
21556 To use it, create or edit the following keys in
21557 @code{HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug} and/or
21558 @code{HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\AeDebug}
21559 (for x86_64 versions):
21563 @code{Debugger} (REG_SZ) --- a command to launch the debugger.
21564 Suggested command is: @code{@var{fully-qualified-path-to-gdb.exe} -ex
21565 "attach %ld" -ex "signal-event %ld" -ex "continue"}.
21567 The first @code{%ld} will be replaced by the process ID of the
21568 crashing process, the second @code{%ld} will be replaced by the ID of
21569 the event that blocks the crashing process, waiting for @value{GDBN}
21573 @code{Auto} (REG_SZ) --- either @code{1} or @code{0}. @code{1} will
21574 make the system run debugger specified by the Debugger key
21575 automatically, @code{0} will cause a dialog box with ``OK'' and
21576 ``Cancel'' buttons to appear, which allows the user to either
21577 terminate the crashing process (OK) or debug it (Cancel).
21580 @kindex set cygwin-exceptions
21581 @cindex debugging the Cygwin DLL
21582 @cindex Cygwin DLL, debugging
21583 @item set cygwin-exceptions @var{mode}
21584 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
21585 happen inside the Cygwin DLL. If @var{mode} is @code{off},
21586 @value{GDBN} will delay recognition of exceptions, and may ignore some
21587 exceptions which seem to be caused by internal Cygwin DLL
21588 ``bookkeeping''. This option is meant primarily for debugging the
21589 Cygwin DLL itself; the default value is @code{off} to avoid annoying
21590 @value{GDBN} users with false @code{SIGSEGV} signals.
21592 @kindex show cygwin-exceptions
21593 @item show cygwin-exceptions
21594 Displays whether @value{GDBN} will break on exceptions that happen
21595 inside the Cygwin DLL itself.
21597 @kindex set new-console
21598 @item set new-console @var{mode}
21599 If @var{mode} is @code{on} the debuggee will
21600 be started in a new console on next start.
21601 If @var{mode} is @code{off}, the debuggee will
21602 be started in the same console as the debugger.
21604 @kindex show new-console
21605 @item show new-console
21606 Displays whether a new console is used
21607 when the debuggee is started.
21609 @kindex set new-group
21610 @item set new-group @var{mode}
21611 This boolean value controls whether the debuggee should
21612 start a new group or stay in the same group as the debugger.
21613 This affects the way the Windows OS handles
21616 @kindex show new-group
21617 @item show new-group
21618 Displays current value of new-group boolean.
21620 @kindex set debugevents
21621 @item set debugevents
21622 This boolean value adds debug output concerning kernel events related
21623 to the debuggee seen by the debugger. This includes events that
21624 signal thread and process creation and exit, DLL loading and
21625 unloading, console interrupts, and debugging messages produced by the
21626 Windows @code{OutputDebugString} API call.
21628 @kindex set debugexec
21629 @item set debugexec
21630 This boolean value adds debug output concerning execute events
21631 (such as resume thread) seen by the debugger.
21633 @kindex set debugexceptions
21634 @item set debugexceptions
21635 This boolean value adds debug output concerning exceptions in the
21636 debuggee seen by the debugger.
21638 @kindex set debugmemory
21639 @item set debugmemory
21640 This boolean value adds debug output concerning debuggee memory reads
21641 and writes by the debugger.
21645 This boolean values specifies whether the debuggee is called
21646 via a shell or directly (default value is on).
21650 Displays if the debuggee will be started with a shell.
21655 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
21658 @node Non-debug DLL Symbols
21659 @subsubsection Support for DLLs without Debugging Symbols
21660 @cindex DLLs with no debugging symbols
21661 @cindex Minimal symbols and DLLs
21663 Very often on windows, some of the DLLs that your program relies on do
21664 not include symbolic debugging information (for example,
21665 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
21666 symbols in a DLL, it relies on the minimal amount of symbolic
21667 information contained in the DLL's export table. This section
21668 describes working with such symbols, known internally to @value{GDBN} as
21669 ``minimal symbols''.
21671 Note that before the debugged program has started execution, no DLLs
21672 will have been loaded. The easiest way around this problem is simply to
21673 start the program --- either by setting a breakpoint or letting the
21674 program run once to completion.
21676 @subsubsection DLL Name Prefixes
21678 In keeping with the naming conventions used by the Microsoft debugging
21679 tools, DLL export symbols are made available with a prefix based on the
21680 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
21681 also entered into the symbol table, so @code{CreateFileA} is often
21682 sufficient. In some cases there will be name clashes within a program
21683 (particularly if the executable itself includes full debugging symbols)
21684 necessitating the use of the fully qualified name when referring to the
21685 contents of the DLL. Use single-quotes around the name to avoid the
21686 exclamation mark (``!'') being interpreted as a language operator.
21688 Note that the internal name of the DLL may be all upper-case, even
21689 though the file name of the DLL is lower-case, or vice-versa. Since
21690 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
21691 some confusion. If in doubt, try the @code{info functions} and
21692 @code{info variables} commands or even @code{maint print msymbols}
21693 (@pxref{Symbols}). Here's an example:
21696 (@value{GDBP}) info function CreateFileA
21697 All functions matching regular expression "CreateFileA":
21699 Non-debugging symbols:
21700 0x77e885f4 CreateFileA
21701 0x77e885f4 KERNEL32!CreateFileA
21705 (@value{GDBP}) info function !
21706 All functions matching regular expression "!":
21708 Non-debugging symbols:
21709 0x6100114c cygwin1!__assert
21710 0x61004034 cygwin1!_dll_crt0@@0
21711 0x61004240 cygwin1!dll_crt0(per_process *)
21715 @subsubsection Working with Minimal Symbols
21717 Symbols extracted from a DLL's export table do not contain very much
21718 type information. All that @value{GDBN} can do is guess whether a symbol
21719 refers to a function or variable depending on the linker section that
21720 contains the symbol. Also note that the actual contents of the memory
21721 contained in a DLL are not available unless the program is running. This
21722 means that you cannot examine the contents of a variable or disassemble
21723 a function within a DLL without a running program.
21725 Variables are generally treated as pointers and dereferenced
21726 automatically. For this reason, it is often necessary to prefix a
21727 variable name with the address-of operator (``&'') and provide explicit
21728 type information in the command. Here's an example of the type of
21732 (@value{GDBP}) print 'cygwin1!__argv'
21737 (@value{GDBP}) x 'cygwin1!__argv'
21738 0x10021610: "\230y\""
21741 And two possible solutions:
21744 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
21745 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
21749 (@value{GDBP}) x/2x &'cygwin1!__argv'
21750 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
21751 (@value{GDBP}) x/x 0x10021608
21752 0x10021608: 0x0022fd98
21753 (@value{GDBP}) x/s 0x0022fd98
21754 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
21757 Setting a break point within a DLL is possible even before the program
21758 starts execution. However, under these circumstances, @value{GDBN} can't
21759 examine the initial instructions of the function in order to skip the
21760 function's frame set-up code. You can work around this by using ``*&''
21761 to set the breakpoint at a raw memory address:
21764 (@value{GDBP}) break *&'python22!PyOS_Readline'
21765 Breakpoint 1 at 0x1e04eff0
21768 The author of these extensions is not entirely convinced that setting a
21769 break point within a shared DLL like @file{kernel32.dll} is completely
21773 @subsection Commands Specific to @sc{gnu} Hurd Systems
21774 @cindex @sc{gnu} Hurd debugging
21776 This subsection describes @value{GDBN} commands specific to the
21777 @sc{gnu} Hurd native debugging.
21782 @kindex set signals@r{, Hurd command}
21783 @kindex set sigs@r{, Hurd command}
21784 This command toggles the state of inferior signal interception by
21785 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
21786 affected by this command. @code{sigs} is a shorthand alias for
21791 @kindex show signals@r{, Hurd command}
21792 @kindex show sigs@r{, Hurd command}
21793 Show the current state of intercepting inferior's signals.
21795 @item set signal-thread
21796 @itemx set sigthread
21797 @kindex set signal-thread
21798 @kindex set sigthread
21799 This command tells @value{GDBN} which thread is the @code{libc} signal
21800 thread. That thread is run when a signal is delivered to a running
21801 process. @code{set sigthread} is the shorthand alias of @code{set
21804 @item show signal-thread
21805 @itemx show sigthread
21806 @kindex show signal-thread
21807 @kindex show sigthread
21808 These two commands show which thread will run when the inferior is
21809 delivered a signal.
21812 @kindex set stopped@r{, Hurd command}
21813 This commands tells @value{GDBN} that the inferior process is stopped,
21814 as with the @code{SIGSTOP} signal. The stopped process can be
21815 continued by delivering a signal to it.
21818 @kindex show stopped@r{, Hurd command}
21819 This command shows whether @value{GDBN} thinks the debuggee is
21822 @item set exceptions
21823 @kindex set exceptions@r{, Hurd command}
21824 Use this command to turn off trapping of exceptions in the inferior.
21825 When exception trapping is off, neither breakpoints nor
21826 single-stepping will work. To restore the default, set exception
21829 @item show exceptions
21830 @kindex show exceptions@r{, Hurd command}
21831 Show the current state of trapping exceptions in the inferior.
21833 @item set task pause
21834 @kindex set task@r{, Hurd commands}
21835 @cindex task attributes (@sc{gnu} Hurd)
21836 @cindex pause current task (@sc{gnu} Hurd)
21837 This command toggles task suspension when @value{GDBN} has control.
21838 Setting it to on takes effect immediately, and the task is suspended
21839 whenever @value{GDBN} gets control. Setting it to off will take
21840 effect the next time the inferior is continued. If this option is set
21841 to off, you can use @code{set thread default pause on} or @code{set
21842 thread pause on} (see below) to pause individual threads.
21844 @item show task pause
21845 @kindex show task@r{, Hurd commands}
21846 Show the current state of task suspension.
21848 @item set task detach-suspend-count
21849 @cindex task suspend count
21850 @cindex detach from task, @sc{gnu} Hurd
21851 This command sets the suspend count the task will be left with when
21852 @value{GDBN} detaches from it.
21854 @item show task detach-suspend-count
21855 Show the suspend count the task will be left with when detaching.
21857 @item set task exception-port
21858 @itemx set task excp
21859 @cindex task exception port, @sc{gnu} Hurd
21860 This command sets the task exception port to which @value{GDBN} will
21861 forward exceptions. The argument should be the value of the @dfn{send
21862 rights} of the task. @code{set task excp} is a shorthand alias.
21864 @item set noninvasive
21865 @cindex noninvasive task options
21866 This command switches @value{GDBN} to a mode that is the least
21867 invasive as far as interfering with the inferior is concerned. This
21868 is the same as using @code{set task pause}, @code{set exceptions}, and
21869 @code{set signals} to values opposite to the defaults.
21871 @item info send-rights
21872 @itemx info receive-rights
21873 @itemx info port-rights
21874 @itemx info port-sets
21875 @itemx info dead-names
21878 @cindex send rights, @sc{gnu} Hurd
21879 @cindex receive rights, @sc{gnu} Hurd
21880 @cindex port rights, @sc{gnu} Hurd
21881 @cindex port sets, @sc{gnu} Hurd
21882 @cindex dead names, @sc{gnu} Hurd
21883 These commands display information about, respectively, send rights,
21884 receive rights, port rights, port sets, and dead names of a task.
21885 There are also shorthand aliases: @code{info ports} for @code{info
21886 port-rights} and @code{info psets} for @code{info port-sets}.
21888 @item set thread pause
21889 @kindex set thread@r{, Hurd command}
21890 @cindex thread properties, @sc{gnu} Hurd
21891 @cindex pause current thread (@sc{gnu} Hurd)
21892 This command toggles current thread suspension when @value{GDBN} has
21893 control. Setting it to on takes effect immediately, and the current
21894 thread is suspended whenever @value{GDBN} gets control. Setting it to
21895 off will take effect the next time the inferior is continued.
21896 Normally, this command has no effect, since when @value{GDBN} has
21897 control, the whole task is suspended. However, if you used @code{set
21898 task pause off} (see above), this command comes in handy to suspend
21899 only the current thread.
21901 @item show thread pause
21902 @kindex show thread@r{, Hurd command}
21903 This command shows the state of current thread suspension.
21905 @item set thread run
21906 This command sets whether the current thread is allowed to run.
21908 @item show thread run
21909 Show whether the current thread is allowed to run.
21911 @item set thread detach-suspend-count
21912 @cindex thread suspend count, @sc{gnu} Hurd
21913 @cindex detach from thread, @sc{gnu} Hurd
21914 This command sets the suspend count @value{GDBN} will leave on a
21915 thread when detaching. This number is relative to the suspend count
21916 found by @value{GDBN} when it notices the thread; use @code{set thread
21917 takeover-suspend-count} to force it to an absolute value.
21919 @item show thread detach-suspend-count
21920 Show the suspend count @value{GDBN} will leave on the thread when
21923 @item set thread exception-port
21924 @itemx set thread excp
21925 Set the thread exception port to which to forward exceptions. This
21926 overrides the port set by @code{set task exception-port} (see above).
21927 @code{set thread excp} is the shorthand alias.
21929 @item set thread takeover-suspend-count
21930 Normally, @value{GDBN}'s thread suspend counts are relative to the
21931 value @value{GDBN} finds when it notices each thread. This command
21932 changes the suspend counts to be absolute instead.
21934 @item set thread default
21935 @itemx show thread default
21936 @cindex thread default settings, @sc{gnu} Hurd
21937 Each of the above @code{set thread} commands has a @code{set thread
21938 default} counterpart (e.g., @code{set thread default pause}, @code{set
21939 thread default exception-port}, etc.). The @code{thread default}
21940 variety of commands sets the default thread properties for all
21941 threads; you can then change the properties of individual threads with
21942 the non-default commands.
21949 @value{GDBN} provides the following commands specific to the Darwin target:
21952 @item set debug darwin @var{num}
21953 @kindex set debug darwin
21954 When set to a non zero value, enables debugging messages specific to
21955 the Darwin support. Higher values produce more verbose output.
21957 @item show debug darwin
21958 @kindex show debug darwin
21959 Show the current state of Darwin messages.
21961 @item set debug mach-o @var{num}
21962 @kindex set debug mach-o
21963 When set to a non zero value, enables debugging messages while
21964 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
21965 file format used on Darwin for object and executable files.) Higher
21966 values produce more verbose output. This is a command to diagnose
21967 problems internal to @value{GDBN} and should not be needed in normal
21970 @item show debug mach-o
21971 @kindex show debug mach-o
21972 Show the current state of Mach-O file messages.
21974 @item set mach-exceptions on
21975 @itemx set mach-exceptions off
21976 @kindex set mach-exceptions
21977 On Darwin, faults are first reported as a Mach exception and are then
21978 mapped to a Posix signal. Use this command to turn on trapping of
21979 Mach exceptions in the inferior. This might be sometimes useful to
21980 better understand the cause of a fault. The default is off.
21982 @item show mach-exceptions
21983 @kindex show mach-exceptions
21984 Show the current state of exceptions trapping.
21989 @section Embedded Operating Systems
21991 This section describes configurations involving the debugging of
21992 embedded operating systems that are available for several different
21995 @value{GDBN} includes the ability to debug programs running on
21996 various real-time operating systems.
21998 @node Embedded Processors
21999 @section Embedded Processors
22001 This section goes into details specific to particular embedded
22004 @cindex send command to simulator
22005 Whenever a specific embedded processor has a simulator, @value{GDBN}
22006 allows to send an arbitrary command to the simulator.
22009 @item sim @var{command}
22010 @kindex sim@r{, a command}
22011 Send an arbitrary @var{command} string to the simulator. Consult the
22012 documentation for the specific simulator in use for information about
22013 acceptable commands.
22019 * M68K:: Motorola M68K
22020 * MicroBlaze:: Xilinx MicroBlaze
22021 * MIPS Embedded:: MIPS Embedded
22022 * PowerPC Embedded:: PowerPC Embedded
22025 * Super-H:: Renesas Super-H
22031 @value{GDBN} provides the following ARM-specific commands:
22034 @item set arm disassembler
22036 This commands selects from a list of disassembly styles. The
22037 @code{"std"} style is the standard style.
22039 @item show arm disassembler
22041 Show the current disassembly style.
22043 @item set arm apcs32
22044 @cindex ARM 32-bit mode
22045 This command toggles ARM operation mode between 32-bit and 26-bit.
22047 @item show arm apcs32
22048 Display the current usage of the ARM 32-bit mode.
22050 @item set arm fpu @var{fputype}
22051 This command sets the ARM floating-point unit (FPU) type. The
22052 argument @var{fputype} can be one of these:
22056 Determine the FPU type by querying the OS ABI.
22058 Software FPU, with mixed-endian doubles on little-endian ARM
22061 GCC-compiled FPA co-processor.
22063 Software FPU with pure-endian doubles.
22069 Show the current type of the FPU.
22072 This command forces @value{GDBN} to use the specified ABI.
22075 Show the currently used ABI.
22077 @item set arm fallback-mode (arm|thumb|auto)
22078 @value{GDBN} uses the symbol table, when available, to determine
22079 whether instructions are ARM or Thumb. This command controls
22080 @value{GDBN}'s default behavior when the symbol table is not
22081 available. The default is @samp{auto}, which causes @value{GDBN} to
22082 use the current execution mode (from the @code{T} bit in the @code{CPSR}
22085 @item show arm fallback-mode
22086 Show the current fallback instruction mode.
22088 @item set arm force-mode (arm|thumb|auto)
22089 This command overrides use of the symbol table to determine whether
22090 instructions are ARM or Thumb. The default is @samp{auto}, which
22091 causes @value{GDBN} to use the symbol table and then the setting
22092 of @samp{set arm fallback-mode}.
22094 @item show arm force-mode
22095 Show the current forced instruction mode.
22097 @item set debug arm
22098 Toggle whether to display ARM-specific debugging messages from the ARM
22099 target support subsystem.
22101 @item show debug arm
22102 Show whether ARM-specific debugging messages are enabled.
22106 @item target sim @r{[}@var{simargs}@r{]} @dots{}
22107 The @value{GDBN} ARM simulator accepts the following optional arguments.
22110 @item --swi-support=@var{type}
22111 Tell the simulator which SWI interfaces to support. The argument
22112 @var{type} may be a comma separated list of the following values.
22113 The default value is @code{all}.
22128 The Motorola m68k configuration includes ColdFire support.
22131 @subsection MicroBlaze
22132 @cindex Xilinx MicroBlaze
22133 @cindex XMD, Xilinx Microprocessor Debugger
22135 The MicroBlaze is a soft-core processor supported on various Xilinx
22136 FPGAs, such as Spartan or Virtex series. Boards with these processors
22137 usually have JTAG ports which connect to a host system running the Xilinx
22138 Embedded Development Kit (EDK) or Software Development Kit (SDK).
22139 This host system is used to download the configuration bitstream to
22140 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
22141 communicates with the target board using the JTAG interface and
22142 presents a @code{gdbserver} interface to the board. By default
22143 @code{xmd} uses port @code{1234}. (While it is possible to change
22144 this default port, it requires the use of undocumented @code{xmd}
22145 commands. Contact Xilinx support if you need to do this.)
22147 Use these GDB commands to connect to the MicroBlaze target processor.
22150 @item target remote :1234
22151 Use this command to connect to the target if you are running @value{GDBN}
22152 on the same system as @code{xmd}.
22154 @item target remote @var{xmd-host}:1234
22155 Use this command to connect to the target if it is connected to @code{xmd}
22156 running on a different system named @var{xmd-host}.
22159 Use this command to download a program to the MicroBlaze target.
22161 @item set debug microblaze @var{n}
22162 Enable MicroBlaze-specific debugging messages if non-zero.
22164 @item show debug microblaze @var{n}
22165 Show MicroBlaze-specific debugging level.
22168 @node MIPS Embedded
22169 @subsection @acronym{MIPS} Embedded
22172 @value{GDBN} supports these special commands for @acronym{MIPS} targets:
22175 @item set mipsfpu double
22176 @itemx set mipsfpu single
22177 @itemx set mipsfpu none
22178 @itemx set mipsfpu auto
22179 @itemx show mipsfpu
22180 @kindex set mipsfpu
22181 @kindex show mipsfpu
22182 @cindex @acronym{MIPS} remote floating point
22183 @cindex floating point, @acronym{MIPS} remote
22184 If your target board does not support the @acronym{MIPS} floating point
22185 coprocessor, you should use the command @samp{set mipsfpu none} (if you
22186 need this, you may wish to put the command in your @value{GDBN} init
22187 file). This tells @value{GDBN} how to find the return value of
22188 functions which return floating point values. It also allows
22189 @value{GDBN} to avoid saving the floating point registers when calling
22190 functions on the board. If you are using a floating point coprocessor
22191 with only single precision floating point support, as on the @sc{r4650}
22192 processor, use the command @samp{set mipsfpu single}. The default
22193 double precision floating point coprocessor may be selected using
22194 @samp{set mipsfpu double}.
22196 In previous versions the only choices were double precision or no
22197 floating point, so @samp{set mipsfpu on} will select double precision
22198 and @samp{set mipsfpu off} will select no floating point.
22200 As usual, you can inquire about the @code{mipsfpu} variable with
22201 @samp{show mipsfpu}.
22204 @node PowerPC Embedded
22205 @subsection PowerPC Embedded
22207 @cindex DVC register
22208 @value{GDBN} supports using the DVC (Data Value Compare) register to
22209 implement in hardware simple hardware watchpoint conditions of the form:
22212 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
22213 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
22216 The DVC register will be automatically used when @value{GDBN} detects
22217 such pattern in a condition expression, and the created watchpoint uses one
22218 debug register (either the @code{exact-watchpoints} option is on and the
22219 variable is scalar, or the variable has a length of one byte). This feature
22220 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
22223 When running on PowerPC embedded processors, @value{GDBN} automatically uses
22224 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
22225 in which case watchpoints using only one debug register are created when
22226 watching variables of scalar types.
22228 You can create an artificial array to watch an arbitrary memory
22229 region using one of the following commands (@pxref{Expressions}):
22232 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
22233 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
22236 PowerPC embedded processors support masked watchpoints. See the discussion
22237 about the @code{mask} argument in @ref{Set Watchpoints}.
22239 @cindex ranged breakpoint
22240 PowerPC embedded processors support hardware accelerated
22241 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
22242 the inferior whenever it executes an instruction at any address within
22243 the range it specifies. To set a ranged breakpoint in @value{GDBN},
22244 use the @code{break-range} command.
22246 @value{GDBN} provides the following PowerPC-specific commands:
22249 @kindex break-range
22250 @item break-range @var{start-location}, @var{end-location}
22251 Set a breakpoint for an address range given by
22252 @var{start-location} and @var{end-location}, which can specify a function name,
22253 a line number, an offset of lines from the current line or from the start
22254 location, or an address of an instruction (see @ref{Specify Location},
22255 for a list of all the possible ways to specify a @var{location}.)
22256 The breakpoint will stop execution of the inferior whenever it
22257 executes an instruction at any address within the specified range,
22258 (including @var{start-location} and @var{end-location}.)
22260 @kindex set powerpc
22261 @item set powerpc soft-float
22262 @itemx show powerpc soft-float
22263 Force @value{GDBN} to use (or not use) a software floating point calling
22264 convention. By default, @value{GDBN} selects the calling convention based
22265 on the selected architecture and the provided executable file.
22267 @item set powerpc vector-abi
22268 @itemx show powerpc vector-abi
22269 Force @value{GDBN} to use the specified calling convention for vector
22270 arguments and return values. The valid options are @samp{auto};
22271 @samp{generic}, to avoid vector registers even if they are present;
22272 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
22273 registers. By default, @value{GDBN} selects the calling convention
22274 based on the selected architecture and the provided executable file.
22276 @item set powerpc exact-watchpoints
22277 @itemx show powerpc exact-watchpoints
22278 Allow @value{GDBN} to use only one debug register when watching a variable
22279 of scalar type, thus assuming that the variable is accessed through the
22280 address of its first byte.
22285 @subsection Atmel AVR
22288 When configured for debugging the Atmel AVR, @value{GDBN} supports the
22289 following AVR-specific commands:
22292 @item info io_registers
22293 @kindex info io_registers@r{, AVR}
22294 @cindex I/O registers (Atmel AVR)
22295 This command displays information about the AVR I/O registers. For
22296 each register, @value{GDBN} prints its number and value.
22303 When configured for debugging CRIS, @value{GDBN} provides the
22304 following CRIS-specific commands:
22307 @item set cris-version @var{ver}
22308 @cindex CRIS version
22309 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
22310 The CRIS version affects register names and sizes. This command is useful in
22311 case autodetection of the CRIS version fails.
22313 @item show cris-version
22314 Show the current CRIS version.
22316 @item set cris-dwarf2-cfi
22317 @cindex DWARF-2 CFI and CRIS
22318 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
22319 Change to @samp{off} when using @code{gcc-cris} whose version is below
22322 @item show cris-dwarf2-cfi
22323 Show the current state of using DWARF-2 CFI.
22325 @item set cris-mode @var{mode}
22327 Set the current CRIS mode to @var{mode}. It should only be changed when
22328 debugging in guru mode, in which case it should be set to
22329 @samp{guru} (the default is @samp{normal}).
22331 @item show cris-mode
22332 Show the current CRIS mode.
22336 @subsection Renesas Super-H
22339 For the Renesas Super-H processor, @value{GDBN} provides these
22343 @item set sh calling-convention @var{convention}
22344 @kindex set sh calling-convention
22345 Set the calling-convention used when calling functions from @value{GDBN}.
22346 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
22347 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
22348 convention. If the DWARF-2 information of the called function specifies
22349 that the function follows the Renesas calling convention, the function
22350 is called using the Renesas calling convention. If the calling convention
22351 is set to @samp{renesas}, the Renesas calling convention is always used,
22352 regardless of the DWARF-2 information. This can be used to override the
22353 default of @samp{gcc} if debug information is missing, or the compiler
22354 does not emit the DWARF-2 calling convention entry for a function.
22356 @item show sh calling-convention
22357 @kindex show sh calling-convention
22358 Show the current calling convention setting.
22363 @node Architectures
22364 @section Architectures
22366 This section describes characteristics of architectures that affect
22367 all uses of @value{GDBN} with the architecture, both native and cross.
22374 * HPPA:: HP PA architecture
22375 * SPU:: Cell Broadband Engine SPU architecture
22381 @subsection AArch64
22382 @cindex AArch64 support
22384 When @value{GDBN} is debugging the AArch64 architecture, it provides the
22385 following special commands:
22388 @item set debug aarch64
22389 @kindex set debug aarch64
22390 This command determines whether AArch64 architecture-specific debugging
22391 messages are to be displayed.
22393 @item show debug aarch64
22394 Show whether AArch64 debugging messages are displayed.
22399 @subsection x86 Architecture-specific Issues
22402 @item set struct-convention @var{mode}
22403 @kindex set struct-convention
22404 @cindex struct return convention
22405 @cindex struct/union returned in registers
22406 Set the convention used by the inferior to return @code{struct}s and
22407 @code{union}s from functions to @var{mode}. Possible values of
22408 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
22409 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
22410 are returned on the stack, while @code{"reg"} means that a
22411 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
22412 be returned in a register.
22414 @item show struct-convention
22415 @kindex show struct-convention
22416 Show the current setting of the convention to return @code{struct}s
22421 @subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
22422 @cindex Intel Memory Protection Extensions (MPX).
22424 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
22425 @footnote{The register named with capital letters represent the architecture
22426 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
22427 which are the lower bound and upper bound. Bounds are effective addresses or
22428 memory locations. The upper bounds are architecturally represented in 1's
22429 complement form. A bound having lower bound = 0, and upper bound = 0
22430 (1's complement of all bits set) will allow access to the entire address space.
22432 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
22433 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
22434 display the upper bound performing the complement of one operation on the
22435 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
22436 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
22437 can also be noted that the upper bounds are inclusive.
22439 As an example, assume that the register BND0 holds bounds for a pointer having
22440 access allowed for the range between 0x32 and 0x71. The values present on
22441 bnd0raw and bnd registers are presented as follows:
22444 bnd0raw = @{0x32, 0xffffffff8e@}
22445 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
22448 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
22449 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
22450 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
22451 Python, the display includes the memory size, in bits, accessible to
22454 Bounds can also be stored in bounds tables, which are stored in
22455 application memory. These tables store bounds for pointers by specifying
22456 the bounds pointer's value along with its bounds. Evaluating and changing
22457 bounds located in bound tables is therefore interesting while investigating
22458 bugs on MPX context. @value{GDBN} provides commands for this purpose:
22461 @item show mpx bound @var{pointer}
22462 @kindex show mpx bound
22463 Display bounds of the given @var{pointer}.
22465 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
22466 @kindex set mpx bound
22467 Set the bounds of a pointer in the bound table.
22468 This command takes three parameters: @var{pointer} is the pointers
22469 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
22470 for lower and upper bounds respectively.
22476 See the following section.
22479 @subsection @acronym{MIPS}
22481 @cindex stack on Alpha
22482 @cindex stack on @acronym{MIPS}
22483 @cindex Alpha stack
22484 @cindex @acronym{MIPS} stack
22485 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
22486 sometimes requires @value{GDBN} to search backward in the object code to
22487 find the beginning of a function.
22489 @cindex response time, @acronym{MIPS} debugging
22490 To improve response time (especially for embedded applications, where
22491 @value{GDBN} may be restricted to a slow serial line for this search)
22492 you may want to limit the size of this search, using one of these
22496 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
22497 @item set heuristic-fence-post @var{limit}
22498 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
22499 search for the beginning of a function. A value of @var{0} (the
22500 default) means there is no limit. However, except for @var{0}, the
22501 larger the limit the more bytes @code{heuristic-fence-post} must search
22502 and therefore the longer it takes to run. You should only need to use
22503 this command when debugging a stripped executable.
22505 @item show heuristic-fence-post
22506 Display the current limit.
22510 These commands are available @emph{only} when @value{GDBN} is configured
22511 for debugging programs on Alpha or @acronym{MIPS} processors.
22513 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
22517 @item set mips abi @var{arg}
22518 @kindex set mips abi
22519 @cindex set ABI for @acronym{MIPS}
22520 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
22521 values of @var{arg} are:
22525 The default ABI associated with the current binary (this is the
22535 @item show mips abi
22536 @kindex show mips abi
22537 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
22539 @item set mips compression @var{arg}
22540 @kindex set mips compression
22541 @cindex code compression, @acronym{MIPS}
22542 Tell @value{GDBN} which @acronym{MIPS} compressed
22543 @acronym{ISA, Instruction Set Architecture} encoding is used by the
22544 inferior. @value{GDBN} uses this for code disassembly and other
22545 internal interpretation purposes. This setting is only referred to
22546 when no executable has been associated with the debugging session or
22547 the executable does not provide information about the encoding it uses.
22548 Otherwise this setting is automatically updated from information
22549 provided by the executable.
22551 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
22552 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
22553 executables containing @acronym{MIPS16} code frequently are not
22554 identified as such.
22556 This setting is ``sticky''; that is, it retains its value across
22557 debugging sessions until reset either explicitly with this command or
22558 implicitly from an executable.
22560 The compiler and/or assembler typically add symbol table annotations to
22561 identify functions compiled for the @acronym{MIPS16} or
22562 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
22563 are present, @value{GDBN} uses them in preference to the global
22564 compressed @acronym{ISA} encoding setting.
22566 @item show mips compression
22567 @kindex show mips compression
22568 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
22569 @value{GDBN} to debug the inferior.
22572 @itemx show mipsfpu
22573 @xref{MIPS Embedded, set mipsfpu}.
22575 @item set mips mask-address @var{arg}
22576 @kindex set mips mask-address
22577 @cindex @acronym{MIPS} addresses, masking
22578 This command determines whether the most-significant 32 bits of 64-bit
22579 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
22580 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
22581 setting, which lets @value{GDBN} determine the correct value.
22583 @item show mips mask-address
22584 @kindex show mips mask-address
22585 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
22588 @item set remote-mips64-transfers-32bit-regs
22589 @kindex set remote-mips64-transfers-32bit-regs
22590 This command controls compatibility with 64-bit @acronym{MIPS} targets that
22591 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
22592 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
22593 and 64 bits for other registers, set this option to @samp{on}.
22595 @item show remote-mips64-transfers-32bit-regs
22596 @kindex show remote-mips64-transfers-32bit-regs
22597 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
22599 @item set debug mips
22600 @kindex set debug mips
22601 This command turns on and off debugging messages for the @acronym{MIPS}-specific
22602 target code in @value{GDBN}.
22604 @item show debug mips
22605 @kindex show debug mips
22606 Show the current setting of @acronym{MIPS} debugging messages.
22612 @cindex HPPA support
22614 When @value{GDBN} is debugging the HP PA architecture, it provides the
22615 following special commands:
22618 @item set debug hppa
22619 @kindex set debug hppa
22620 This command determines whether HPPA architecture-specific debugging
22621 messages are to be displayed.
22623 @item show debug hppa
22624 Show whether HPPA debugging messages are displayed.
22626 @item maint print unwind @var{address}
22627 @kindex maint print unwind@r{, HPPA}
22628 This command displays the contents of the unwind table entry at the
22629 given @var{address}.
22635 @subsection Cell Broadband Engine SPU architecture
22636 @cindex Cell Broadband Engine
22639 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
22640 it provides the following special commands:
22643 @item info spu event
22645 Display SPU event facility status. Shows current event mask
22646 and pending event status.
22648 @item info spu signal
22649 Display SPU signal notification facility status. Shows pending
22650 signal-control word and signal notification mode of both signal
22651 notification channels.
22653 @item info spu mailbox
22654 Display SPU mailbox facility status. Shows all pending entries,
22655 in order of processing, in each of the SPU Write Outbound,
22656 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
22659 Display MFC DMA status. Shows all pending commands in the MFC
22660 DMA queue. For each entry, opcode, tag, class IDs, effective
22661 and local store addresses and transfer size are shown.
22663 @item info spu proxydma
22664 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
22665 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
22666 and local store addresses and transfer size are shown.
22670 When @value{GDBN} is debugging a combined PowerPC/SPU application
22671 on the Cell Broadband Engine, it provides in addition the following
22675 @item set spu stop-on-load @var{arg}
22677 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
22678 will give control to the user when a new SPE thread enters its @code{main}
22679 function. The default is @code{off}.
22681 @item show spu stop-on-load
22683 Show whether to stop for new SPE threads.
22685 @item set spu auto-flush-cache @var{arg}
22686 Set whether to automatically flush the software-managed cache. When set to
22687 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
22688 cache to be flushed whenever SPE execution stops. This provides a consistent
22689 view of PowerPC memory that is accessed via the cache. If an application
22690 does not use the software-managed cache, this option has no effect.
22692 @item show spu auto-flush-cache
22693 Show whether to automatically flush the software-managed cache.
22698 @subsection PowerPC
22699 @cindex PowerPC architecture
22701 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
22702 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
22703 numbers stored in the floating point registers. These values must be stored
22704 in two consecutive registers, always starting at an even register like
22705 @code{f0} or @code{f2}.
22707 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
22708 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
22709 @code{f2} and @code{f3} for @code{$dl1} and so on.
22711 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
22712 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
22715 @subsection Nios II
22716 @cindex Nios II architecture
22718 When @value{GDBN} is debugging the Nios II architecture,
22719 it provides the following special commands:
22723 @item set debug nios2
22724 @kindex set debug nios2
22725 This command turns on and off debugging messages for the Nios II
22726 target code in @value{GDBN}.
22728 @item show debug nios2
22729 @kindex show debug nios2
22730 Show the current setting of Nios II debugging messages.
22733 @node Controlling GDB
22734 @chapter Controlling @value{GDBN}
22736 You can alter the way @value{GDBN} interacts with you by using the
22737 @code{set} command. For commands controlling how @value{GDBN} displays
22738 data, see @ref{Print Settings, ,Print Settings}. Other settings are
22743 * Editing:: Command editing
22744 * Command History:: Command history
22745 * Screen Size:: Screen size
22746 * Numbers:: Numbers
22747 * ABI:: Configuring the current ABI
22748 * Auto-loading:: Automatically loading associated files
22749 * Messages/Warnings:: Optional warnings and messages
22750 * Debugging Output:: Optional messages about internal happenings
22751 * Other Misc Settings:: Other Miscellaneous Settings
22759 @value{GDBN} indicates its readiness to read a command by printing a string
22760 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
22761 can change the prompt string with the @code{set prompt} command. For
22762 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
22763 the prompt in one of the @value{GDBN} sessions so that you can always tell
22764 which one you are talking to.
22766 @emph{Note:} @code{set prompt} does not add a space for you after the
22767 prompt you set. This allows you to set a prompt which ends in a space
22768 or a prompt that does not.
22772 @item set prompt @var{newprompt}
22773 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
22775 @kindex show prompt
22777 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
22780 Versions of @value{GDBN} that ship with Python scripting enabled have
22781 prompt extensions. The commands for interacting with these extensions
22785 @kindex set extended-prompt
22786 @item set extended-prompt @var{prompt}
22787 Set an extended prompt that allows for substitutions.
22788 @xref{gdb.prompt}, for a list of escape sequences that can be used for
22789 substitution. Any escape sequences specified as part of the prompt
22790 string are replaced with the corresponding strings each time the prompt
22796 set extended-prompt Current working directory: \w (gdb)
22799 Note that when an extended-prompt is set, it takes control of the
22800 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
22802 @kindex show extended-prompt
22803 @item show extended-prompt
22804 Prints the extended prompt. Any escape sequences specified as part of
22805 the prompt string with @code{set extended-prompt}, are replaced with the
22806 corresponding strings each time the prompt is displayed.
22810 @section Command Editing
22812 @cindex command line editing
22814 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
22815 @sc{gnu} library provides consistent behavior for programs which provide a
22816 command line interface to the user. Advantages are @sc{gnu} Emacs-style
22817 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
22818 substitution, and a storage and recall of command history across
22819 debugging sessions.
22821 You may control the behavior of command line editing in @value{GDBN} with the
22822 command @code{set}.
22825 @kindex set editing
22828 @itemx set editing on
22829 Enable command line editing (enabled by default).
22831 @item set editing off
22832 Disable command line editing.
22834 @kindex show editing
22836 Show whether command line editing is enabled.
22839 @ifset SYSTEM_READLINE
22840 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
22842 @ifclear SYSTEM_READLINE
22843 @xref{Command Line Editing},
22845 for more details about the Readline
22846 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
22847 encouraged to read that chapter.
22849 @node Command History
22850 @section Command History
22851 @cindex command history
22853 @value{GDBN} can keep track of the commands you type during your
22854 debugging sessions, so that you can be certain of precisely what
22855 happened. Use these commands to manage the @value{GDBN} command
22858 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
22859 package, to provide the history facility.
22860 @ifset SYSTEM_READLINE
22861 @xref{Using History Interactively, , , history, GNU History Library},
22863 @ifclear SYSTEM_READLINE
22864 @xref{Using History Interactively},
22866 for the detailed description of the History library.
22868 To issue a command to @value{GDBN} without affecting certain aspects of
22869 the state which is seen by users, prefix it with @samp{server }
22870 (@pxref{Server Prefix}). This
22871 means that this command will not affect the command history, nor will it
22872 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
22873 pressed on a line by itself.
22875 @cindex @code{server}, command prefix
22876 The server prefix does not affect the recording of values into the value
22877 history; to print a value without recording it into the value history,
22878 use the @code{output} command instead of the @code{print} command.
22880 Here is the description of @value{GDBN} commands related to command
22884 @cindex history substitution
22885 @cindex history file
22886 @kindex set history filename
22887 @cindex @env{GDBHISTFILE}, environment variable
22888 @item set history filename @var{fname}
22889 Set the name of the @value{GDBN} command history file to @var{fname}.
22890 This is the file where @value{GDBN} reads an initial command history
22891 list, and where it writes the command history from this session when it
22892 exits. You can access this list through history expansion or through
22893 the history command editing characters listed below. This file defaults
22894 to the value of the environment variable @code{GDBHISTFILE}, or to
22895 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
22898 @cindex save command history
22899 @kindex set history save
22900 @item set history save
22901 @itemx set history save on
22902 Record command history in a file, whose name may be specified with the
22903 @code{set history filename} command. By default, this option is disabled.
22905 @item set history save off
22906 Stop recording command history in a file.
22908 @cindex history size
22909 @kindex set history size
22910 @cindex @env{GDBHISTSIZE}, environment variable
22911 @item set history size @var{size}
22912 @itemx set history size unlimited
22913 Set the number of commands which @value{GDBN} keeps in its history list.
22914 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
22915 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
22916 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
22917 either a negative number or the empty string, then the number of commands
22918 @value{GDBN} keeps in the history list is unlimited.
22920 @cindex remove duplicate history
22921 @kindex set history remove-duplicates
22922 @item set history remove-duplicates @var{count}
22923 @itemx set history remove-duplicates unlimited
22924 Control the removal of duplicate history entries in the command history list.
22925 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
22926 history entries and remove the first entry that is a duplicate of the current
22927 entry being added to the command history list. If @var{count} is
22928 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
22929 removal of duplicate history entries is disabled.
22931 Only history entries added during the current session are considered for
22932 removal. This option is set to 0 by default.
22936 History expansion assigns special meaning to the character @kbd{!}.
22937 @ifset SYSTEM_READLINE
22938 @xref{Event Designators, , , history, GNU History Library},
22940 @ifclear SYSTEM_READLINE
22941 @xref{Event Designators},
22945 @cindex history expansion, turn on/off
22946 Since @kbd{!} is also the logical not operator in C, history expansion
22947 is off by default. If you decide to enable history expansion with the
22948 @code{set history expansion on} command, you may sometimes need to
22949 follow @kbd{!} (when it is used as logical not, in an expression) with
22950 a space or a tab to prevent it from being expanded. The readline
22951 history facilities do not attempt substitution on the strings
22952 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
22954 The commands to control history expansion are:
22957 @item set history expansion on
22958 @itemx set history expansion
22959 @kindex set history expansion
22960 Enable history expansion. History expansion is off by default.
22962 @item set history expansion off
22963 Disable history expansion.
22966 @kindex show history
22968 @itemx show history filename
22969 @itemx show history save
22970 @itemx show history size
22971 @itemx show history expansion
22972 These commands display the state of the @value{GDBN} history parameters.
22973 @code{show history} by itself displays all four states.
22978 @kindex show commands
22979 @cindex show last commands
22980 @cindex display command history
22981 @item show commands
22982 Display the last ten commands in the command history.
22984 @item show commands @var{n}
22985 Print ten commands centered on command number @var{n}.
22987 @item show commands +
22988 Print ten commands just after the commands last printed.
22992 @section Screen Size
22993 @cindex size of screen
22994 @cindex screen size
22997 @cindex pauses in output
22999 Certain commands to @value{GDBN} may produce large amounts of
23000 information output to the screen. To help you read all of it,
23001 @value{GDBN} pauses and asks you for input at the end of each page of
23002 output. Type @key{RET} when you want to continue the output, or @kbd{q}
23003 to discard the remaining output. Also, the screen width setting
23004 determines when to wrap lines of output. Depending on what is being
23005 printed, @value{GDBN} tries to break the line at a readable place,
23006 rather than simply letting it overflow onto the following line.
23008 Normally @value{GDBN} knows the size of the screen from the terminal
23009 driver software. For example, on Unix @value{GDBN} uses the termcap data base
23010 together with the value of the @code{TERM} environment variable and the
23011 @code{stty rows} and @code{stty cols} settings. If this is not correct,
23012 you can override it with the @code{set height} and @code{set
23019 @kindex show height
23020 @item set height @var{lpp}
23021 @itemx set height unlimited
23023 @itemx set width @var{cpl}
23024 @itemx set width unlimited
23026 These @code{set} commands specify a screen height of @var{lpp} lines and
23027 a screen width of @var{cpl} characters. The associated @code{show}
23028 commands display the current settings.
23030 If you specify a height of either @code{unlimited} or zero lines,
23031 @value{GDBN} does not pause during output no matter how long the
23032 output is. This is useful if output is to a file or to an editor
23035 Likewise, you can specify @samp{set width unlimited} or @samp{set
23036 width 0} to prevent @value{GDBN} from wrapping its output.
23038 @item set pagination on
23039 @itemx set pagination off
23040 @kindex set pagination
23041 Turn the output pagination on or off; the default is on. Turning
23042 pagination off is the alternative to @code{set height unlimited}. Note that
23043 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
23044 Options, -batch}) also automatically disables pagination.
23046 @item show pagination
23047 @kindex show pagination
23048 Show the current pagination mode.
23053 @cindex number representation
23054 @cindex entering numbers
23056 You can always enter numbers in octal, decimal, or hexadecimal in
23057 @value{GDBN} by the usual conventions: octal numbers begin with
23058 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
23059 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
23060 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
23061 10; likewise, the default display for numbers---when no particular
23062 format is specified---is base 10. You can change the default base for
23063 both input and output with the commands described below.
23066 @kindex set input-radix
23067 @item set input-radix @var{base}
23068 Set the default base for numeric input. Supported choices
23069 for @var{base} are decimal 8, 10, or 16. The base must itself be
23070 specified either unambiguously or using the current input radix; for
23074 set input-radix 012
23075 set input-radix 10.
23076 set input-radix 0xa
23080 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
23081 leaves the input radix unchanged, no matter what it was, since
23082 @samp{10}, being without any leading or trailing signs of its base, is
23083 interpreted in the current radix. Thus, if the current radix is 16,
23084 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
23087 @kindex set output-radix
23088 @item set output-radix @var{base}
23089 Set the default base for numeric display. Supported choices
23090 for @var{base} are decimal 8, 10, or 16. The base must itself be
23091 specified either unambiguously or using the current input radix.
23093 @kindex show input-radix
23094 @item show input-radix
23095 Display the current default base for numeric input.
23097 @kindex show output-radix
23098 @item show output-radix
23099 Display the current default base for numeric display.
23101 @item set radix @r{[}@var{base}@r{]}
23105 These commands set and show the default base for both input and output
23106 of numbers. @code{set radix} sets the radix of input and output to
23107 the same base; without an argument, it resets the radix back to its
23108 default value of 10.
23113 @section Configuring the Current ABI
23115 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
23116 application automatically. However, sometimes you need to override its
23117 conclusions. Use these commands to manage @value{GDBN}'s view of the
23123 @cindex Newlib OS ABI and its influence on the longjmp handling
23125 One @value{GDBN} configuration can debug binaries for multiple operating
23126 system targets, either via remote debugging or native emulation.
23127 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
23128 but you can override its conclusion using the @code{set osabi} command.
23129 One example where this is useful is in debugging of binaries which use
23130 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
23131 not have the same identifying marks that the standard C library for your
23134 When @value{GDBN} is debugging the AArch64 architecture, it provides a
23135 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
23136 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
23137 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
23141 Show the OS ABI currently in use.
23144 With no argument, show the list of registered available OS ABI's.
23146 @item set osabi @var{abi}
23147 Set the current OS ABI to @var{abi}.
23150 @cindex float promotion
23152 Generally, the way that an argument of type @code{float} is passed to a
23153 function depends on whether the function is prototyped. For a prototyped
23154 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
23155 according to the architecture's convention for @code{float}. For unprototyped
23156 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
23157 @code{double} and then passed.
23159 Unfortunately, some forms of debug information do not reliably indicate whether
23160 a function is prototyped. If @value{GDBN} calls a function that is not marked
23161 as prototyped, it consults @kbd{set coerce-float-to-double}.
23164 @kindex set coerce-float-to-double
23165 @item set coerce-float-to-double
23166 @itemx set coerce-float-to-double on
23167 Arguments of type @code{float} will be promoted to @code{double} when passed
23168 to an unprototyped function. This is the default setting.
23170 @item set coerce-float-to-double off
23171 Arguments of type @code{float} will be passed directly to unprototyped
23174 @kindex show coerce-float-to-double
23175 @item show coerce-float-to-double
23176 Show the current setting of promoting @code{float} to @code{double}.
23180 @kindex show cp-abi
23181 @value{GDBN} needs to know the ABI used for your program's C@t{++}
23182 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
23183 used to build your application. @value{GDBN} only fully supports
23184 programs with a single C@t{++} ABI; if your program contains code using
23185 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
23186 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
23187 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
23188 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
23189 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
23190 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
23195 Show the C@t{++} ABI currently in use.
23198 With no argument, show the list of supported C@t{++} ABI's.
23200 @item set cp-abi @var{abi}
23201 @itemx set cp-abi auto
23202 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
23206 @section Automatically loading associated files
23207 @cindex auto-loading
23209 @value{GDBN} sometimes reads files with commands and settings automatically,
23210 without being explicitly told so by the user. We call this feature
23211 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
23212 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
23213 results or introduce security risks (e.g., if the file comes from untrusted
23217 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
23218 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
23220 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
23221 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
23224 There are various kinds of files @value{GDBN} can automatically load.
23225 In addition to these files, @value{GDBN} supports auto-loading code written
23226 in various extension languages. @xref{Auto-loading extensions}.
23228 Note that loading of these associated files (including the local @file{.gdbinit}
23229 file) requires accordingly configured @code{auto-load safe-path}
23230 (@pxref{Auto-loading safe path}).
23232 For these reasons, @value{GDBN} includes commands and options to let you
23233 control when to auto-load files and which files should be auto-loaded.
23236 @anchor{set auto-load off}
23237 @kindex set auto-load off
23238 @item set auto-load off
23239 Globally disable loading of all auto-loaded files.
23240 You may want to use this command with the @samp{-iex} option
23241 (@pxref{Option -init-eval-command}) such as:
23243 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
23246 Be aware that system init file (@pxref{System-wide configuration})
23247 and init files from your home directory (@pxref{Home Directory Init File})
23248 still get read (as they come from generally trusted directories).
23249 To prevent @value{GDBN} from auto-loading even those init files, use the
23250 @option{-nx} option (@pxref{Mode Options}), in addition to
23251 @code{set auto-load no}.
23253 @anchor{show auto-load}
23254 @kindex show auto-load
23255 @item show auto-load
23256 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
23260 (gdb) show auto-load
23261 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
23262 libthread-db: Auto-loading of inferior specific libthread_db is on.
23263 local-gdbinit: Auto-loading of .gdbinit script from current directory
23265 python-scripts: Auto-loading of Python scripts is on.
23266 safe-path: List of directories from which it is safe to auto-load files
23267 is $debugdir:$datadir/auto-load.
23268 scripts-directory: List of directories from which to load auto-loaded scripts
23269 is $debugdir:$datadir/auto-load.
23272 @anchor{info auto-load}
23273 @kindex info auto-load
23274 @item info auto-load
23275 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
23279 (gdb) info auto-load
23282 Yes /home/user/gdb/gdb-gdb.gdb
23283 libthread-db: No auto-loaded libthread-db.
23284 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
23288 Yes /home/user/gdb/gdb-gdb.py
23292 These are @value{GDBN} control commands for the auto-loading:
23294 @multitable @columnfractions .5 .5
23295 @item @xref{set auto-load off}.
23296 @tab Disable auto-loading globally.
23297 @item @xref{show auto-load}.
23298 @tab Show setting of all kinds of files.
23299 @item @xref{info auto-load}.
23300 @tab Show state of all kinds of files.
23301 @item @xref{set auto-load gdb-scripts}.
23302 @tab Control for @value{GDBN} command scripts.
23303 @item @xref{show auto-load gdb-scripts}.
23304 @tab Show setting of @value{GDBN} command scripts.
23305 @item @xref{info auto-load gdb-scripts}.
23306 @tab Show state of @value{GDBN} command scripts.
23307 @item @xref{set auto-load python-scripts}.
23308 @tab Control for @value{GDBN} Python scripts.
23309 @item @xref{show auto-load python-scripts}.
23310 @tab Show setting of @value{GDBN} Python scripts.
23311 @item @xref{info auto-load python-scripts}.
23312 @tab Show state of @value{GDBN} Python scripts.
23313 @item @xref{set auto-load guile-scripts}.
23314 @tab Control for @value{GDBN} Guile scripts.
23315 @item @xref{show auto-load guile-scripts}.
23316 @tab Show setting of @value{GDBN} Guile scripts.
23317 @item @xref{info auto-load guile-scripts}.
23318 @tab Show state of @value{GDBN} Guile scripts.
23319 @item @xref{set auto-load scripts-directory}.
23320 @tab Control for @value{GDBN} auto-loaded scripts location.
23321 @item @xref{show auto-load scripts-directory}.
23322 @tab Show @value{GDBN} auto-loaded scripts location.
23323 @item @xref{add-auto-load-scripts-directory}.
23324 @tab Add directory for auto-loaded scripts location list.
23325 @item @xref{set auto-load local-gdbinit}.
23326 @tab Control for init file in the current directory.
23327 @item @xref{show auto-load local-gdbinit}.
23328 @tab Show setting of init file in the current directory.
23329 @item @xref{info auto-load local-gdbinit}.
23330 @tab Show state of init file in the current directory.
23331 @item @xref{set auto-load libthread-db}.
23332 @tab Control for thread debugging library.
23333 @item @xref{show auto-load libthread-db}.
23334 @tab Show setting of thread debugging library.
23335 @item @xref{info auto-load libthread-db}.
23336 @tab Show state of thread debugging library.
23337 @item @xref{set auto-load safe-path}.
23338 @tab Control directories trusted for automatic loading.
23339 @item @xref{show auto-load safe-path}.
23340 @tab Show directories trusted for automatic loading.
23341 @item @xref{add-auto-load-safe-path}.
23342 @tab Add directory trusted for automatic loading.
23345 @node Init File in the Current Directory
23346 @subsection Automatically loading init file in the current directory
23347 @cindex auto-loading init file in the current directory
23349 By default, @value{GDBN} reads and executes the canned sequences of commands
23350 from init file (if any) in the current working directory,
23351 see @ref{Init File in the Current Directory during Startup}.
23353 Note that loading of this local @file{.gdbinit} file also requires accordingly
23354 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23357 @anchor{set auto-load local-gdbinit}
23358 @kindex set auto-load local-gdbinit
23359 @item set auto-load local-gdbinit [on|off]
23360 Enable or disable the auto-loading of canned sequences of commands
23361 (@pxref{Sequences}) found in init file in the current directory.
23363 @anchor{show auto-load local-gdbinit}
23364 @kindex show auto-load local-gdbinit
23365 @item show auto-load local-gdbinit
23366 Show whether auto-loading of canned sequences of commands from init file in the
23367 current directory is enabled or disabled.
23369 @anchor{info auto-load local-gdbinit}
23370 @kindex info auto-load local-gdbinit
23371 @item info auto-load local-gdbinit
23372 Print whether canned sequences of commands from init file in the
23373 current directory have been auto-loaded.
23376 @node libthread_db.so.1 file
23377 @subsection Automatically loading thread debugging library
23378 @cindex auto-loading libthread_db.so.1
23380 This feature is currently present only on @sc{gnu}/Linux native hosts.
23382 @value{GDBN} reads in some cases thread debugging library from places specific
23383 to the inferior (@pxref{set libthread-db-search-path}).
23385 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
23386 without checking this @samp{set auto-load libthread-db} switch as system
23387 libraries have to be trusted in general. In all other cases of
23388 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
23389 auto-load libthread-db} is enabled before trying to open such thread debugging
23392 Note that loading of this debugging library also requires accordingly configured
23393 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23396 @anchor{set auto-load libthread-db}
23397 @kindex set auto-load libthread-db
23398 @item set auto-load libthread-db [on|off]
23399 Enable or disable the auto-loading of inferior specific thread debugging library.
23401 @anchor{show auto-load libthread-db}
23402 @kindex show auto-load libthread-db
23403 @item show auto-load libthread-db
23404 Show whether auto-loading of inferior specific thread debugging library is
23405 enabled or disabled.
23407 @anchor{info auto-load libthread-db}
23408 @kindex info auto-load libthread-db
23409 @item info auto-load libthread-db
23410 Print the list of all loaded inferior specific thread debugging libraries and
23411 for each such library print list of inferior @var{pid}s using it.
23414 @node Auto-loading safe path
23415 @subsection Security restriction for auto-loading
23416 @cindex auto-loading safe-path
23418 As the files of inferior can come from untrusted source (such as submitted by
23419 an application user) @value{GDBN} does not always load any files automatically.
23420 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
23421 directories trusted for loading files not explicitly requested by user.
23422 Each directory can also be a shell wildcard pattern.
23424 If the path is not set properly you will see a warning and the file will not
23429 Reading symbols from /home/user/gdb/gdb...done.
23430 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
23431 declined by your `auto-load safe-path' set
23432 to "$debugdir:$datadir/auto-load".
23433 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
23434 declined by your `auto-load safe-path' set
23435 to "$debugdir:$datadir/auto-load".
23439 To instruct @value{GDBN} to go ahead and use the init files anyway,
23440 invoke @value{GDBN} like this:
23443 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
23446 The list of trusted directories is controlled by the following commands:
23449 @anchor{set auto-load safe-path}
23450 @kindex set auto-load safe-path
23451 @item set auto-load safe-path @r{[}@var{directories}@r{]}
23452 Set the list of directories (and their subdirectories) trusted for automatic
23453 loading and execution of scripts. You can also enter a specific trusted file.
23454 Each directory can also be a shell wildcard pattern; wildcards do not match
23455 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
23456 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
23457 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
23458 its default value as specified during @value{GDBN} compilation.
23460 The list of directories uses path separator (@samp{:} on GNU and Unix
23461 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
23462 to the @env{PATH} environment variable.
23464 @anchor{show auto-load safe-path}
23465 @kindex show auto-load safe-path
23466 @item show auto-load safe-path
23467 Show the list of directories trusted for automatic loading and execution of
23470 @anchor{add-auto-load-safe-path}
23471 @kindex add-auto-load-safe-path
23472 @item add-auto-load-safe-path
23473 Add an entry (or list of entries) to the list of directories trusted for
23474 automatic loading and execution of scripts. Multiple entries may be delimited
23475 by the host platform path separator in use.
23478 This variable defaults to what @code{--with-auto-load-dir} has been configured
23479 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
23480 substitution applies the same as for @ref{set auto-load scripts-directory}.
23481 The default @code{set auto-load safe-path} value can be also overriden by
23482 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
23484 Setting this variable to @file{/} disables this security protection,
23485 corresponding @value{GDBN} configuration option is
23486 @option{--without-auto-load-safe-path}.
23487 This variable is supposed to be set to the system directories writable by the
23488 system superuser only. Users can add their source directories in init files in
23489 their home directories (@pxref{Home Directory Init File}). See also deprecated
23490 init file in the current directory
23491 (@pxref{Init File in the Current Directory during Startup}).
23493 To force @value{GDBN} to load the files it declined to load in the previous
23494 example, you could use one of the following ways:
23497 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
23498 Specify this trusted directory (or a file) as additional component of the list.
23499 You have to specify also any existing directories displayed by
23500 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
23502 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
23503 Specify this directory as in the previous case but just for a single
23504 @value{GDBN} session.
23506 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
23507 Disable auto-loading safety for a single @value{GDBN} session.
23508 This assumes all the files you debug during this @value{GDBN} session will come
23509 from trusted sources.
23511 @item @kbd{./configure --without-auto-load-safe-path}
23512 During compilation of @value{GDBN} you may disable any auto-loading safety.
23513 This assumes all the files you will ever debug with this @value{GDBN} come from
23517 On the other hand you can also explicitly forbid automatic files loading which
23518 also suppresses any such warning messages:
23521 @item @kbd{gdb -iex "set auto-load no" @dots{}}
23522 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
23524 @item @file{~/.gdbinit}: @samp{set auto-load no}
23525 Disable auto-loading globally for the user
23526 (@pxref{Home Directory Init File}). While it is improbable, you could also
23527 use system init file instead (@pxref{System-wide configuration}).
23530 This setting applies to the file names as entered by user. If no entry matches
23531 @value{GDBN} tries as a last resort to also resolve all the file names into
23532 their canonical form (typically resolving symbolic links) and compare the
23533 entries again. @value{GDBN} already canonicalizes most of the filenames on its
23534 own before starting the comparison so a canonical form of directories is
23535 recommended to be entered.
23537 @node Auto-loading verbose mode
23538 @subsection Displaying files tried for auto-load
23539 @cindex auto-loading verbose mode
23541 For better visibility of all the file locations where you can place scripts to
23542 be auto-loaded with inferior --- or to protect yourself against accidental
23543 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
23544 all the files attempted to be loaded. Both existing and non-existing files may
23547 For example the list of directories from which it is safe to auto-load files
23548 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
23549 may not be too obvious while setting it up.
23552 (gdb) set debug auto-load on
23553 (gdb) file ~/src/t/true
23554 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
23555 for objfile "/tmp/true".
23556 auto-load: Updating directories of "/usr:/opt".
23557 auto-load: Using directory "/usr".
23558 auto-load: Using directory "/opt".
23559 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
23560 by your `auto-load safe-path' set to "/usr:/opt".
23564 @anchor{set debug auto-load}
23565 @kindex set debug auto-load
23566 @item set debug auto-load [on|off]
23567 Set whether to print the filenames attempted to be auto-loaded.
23569 @anchor{show debug auto-load}
23570 @kindex show debug auto-load
23571 @item show debug auto-load
23572 Show whether printing of the filenames attempted to be auto-loaded is turned
23576 @node Messages/Warnings
23577 @section Optional Warnings and Messages
23579 @cindex verbose operation
23580 @cindex optional warnings
23581 By default, @value{GDBN} is silent about its inner workings. If you are
23582 running on a slow machine, you may want to use the @code{set verbose}
23583 command. This makes @value{GDBN} tell you when it does a lengthy
23584 internal operation, so you will not think it has crashed.
23586 Currently, the messages controlled by @code{set verbose} are those
23587 which announce that the symbol table for a source file is being read;
23588 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
23591 @kindex set verbose
23592 @item set verbose on
23593 Enables @value{GDBN} output of certain informational messages.
23595 @item set verbose off
23596 Disables @value{GDBN} output of certain informational messages.
23598 @kindex show verbose
23600 Displays whether @code{set verbose} is on or off.
23603 By default, if @value{GDBN} encounters bugs in the symbol table of an
23604 object file, it is silent; but if you are debugging a compiler, you may
23605 find this information useful (@pxref{Symbol Errors, ,Errors Reading
23610 @kindex set complaints
23611 @item set complaints @var{limit}
23612 Permits @value{GDBN} to output @var{limit} complaints about each type of
23613 unusual symbols before becoming silent about the problem. Set
23614 @var{limit} to zero to suppress all complaints; set it to a large number
23615 to prevent complaints from being suppressed.
23617 @kindex show complaints
23618 @item show complaints
23619 Displays how many symbol complaints @value{GDBN} is permitted to produce.
23623 @anchor{confirmation requests}
23624 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
23625 lot of stupid questions to confirm certain commands. For example, if
23626 you try to run a program which is already running:
23630 The program being debugged has been started already.
23631 Start it from the beginning? (y or n)
23634 If you are willing to unflinchingly face the consequences of your own
23635 commands, you can disable this ``feature'':
23639 @kindex set confirm
23641 @cindex confirmation
23642 @cindex stupid questions
23643 @item set confirm off
23644 Disables confirmation requests. Note that running @value{GDBN} with
23645 the @option{--batch} option (@pxref{Mode Options, -batch}) also
23646 automatically disables confirmation requests.
23648 @item set confirm on
23649 Enables confirmation requests (the default).
23651 @kindex show confirm
23653 Displays state of confirmation requests.
23657 @cindex command tracing
23658 If you need to debug user-defined commands or sourced files you may find it
23659 useful to enable @dfn{command tracing}. In this mode each command will be
23660 printed as it is executed, prefixed with one or more @samp{+} symbols, the
23661 quantity denoting the call depth of each command.
23664 @kindex set trace-commands
23665 @cindex command scripts, debugging
23666 @item set trace-commands on
23667 Enable command tracing.
23668 @item set trace-commands off
23669 Disable command tracing.
23670 @item show trace-commands
23671 Display the current state of command tracing.
23674 @node Debugging Output
23675 @section Optional Messages about Internal Happenings
23676 @cindex optional debugging messages
23678 @value{GDBN} has commands that enable optional debugging messages from
23679 various @value{GDBN} subsystems; normally these commands are of
23680 interest to @value{GDBN} maintainers, or when reporting a bug. This
23681 section documents those commands.
23684 @kindex set exec-done-display
23685 @item set exec-done-display
23686 Turns on or off the notification of asynchronous commands'
23687 completion. When on, @value{GDBN} will print a message when an
23688 asynchronous command finishes its execution. The default is off.
23689 @kindex show exec-done-display
23690 @item show exec-done-display
23691 Displays the current setting of asynchronous command completion
23694 @cindex ARM AArch64
23695 @item set debug aarch64
23696 Turns on or off display of debugging messages related to ARM AArch64.
23697 The default is off.
23699 @item show debug aarch64
23700 Displays the current state of displaying debugging messages related to
23702 @cindex gdbarch debugging info
23703 @cindex architecture debugging info
23704 @item set debug arch
23705 Turns on or off display of gdbarch debugging info. The default is off
23706 @item show debug arch
23707 Displays the current state of displaying gdbarch debugging info.
23708 @item set debug aix-solib
23709 @cindex AIX shared library debugging
23710 Control display of debugging messages from the AIX shared library
23711 support module. The default is off.
23712 @item show debug aix-thread
23713 Show the current state of displaying AIX shared library debugging messages.
23714 @item set debug aix-thread
23715 @cindex AIX threads
23716 Display debugging messages about inner workings of the AIX thread
23718 @item show debug aix-thread
23719 Show the current state of AIX thread debugging info display.
23720 @item set debug check-physname
23722 Check the results of the ``physname'' computation. When reading DWARF
23723 debugging information for C@t{++}, @value{GDBN} attempts to compute
23724 each entity's name. @value{GDBN} can do this computation in two
23725 different ways, depending on exactly what information is present.
23726 When enabled, this setting causes @value{GDBN} to compute the names
23727 both ways and display any discrepancies.
23728 @item show debug check-physname
23729 Show the current state of ``physname'' checking.
23730 @item set debug coff-pe-read
23731 @cindex COFF/PE exported symbols
23732 Control display of debugging messages related to reading of COFF/PE
23733 exported symbols. The default is off.
23734 @item show debug coff-pe-read
23735 Displays the current state of displaying debugging messages related to
23736 reading of COFF/PE exported symbols.
23737 @item set debug dwarf-die
23739 Dump DWARF DIEs after they are read in.
23740 The value is the number of nesting levels to print.
23741 A value of zero turns off the display.
23742 @item show debug dwarf-die
23743 Show the current state of DWARF DIE debugging.
23744 @item set debug dwarf-line
23745 @cindex DWARF Line Tables
23746 Turns on or off display of debugging messages related to reading
23747 DWARF line tables. The default is 0 (off).
23748 A value of 1 provides basic information.
23749 A value greater than 1 provides more verbose information.
23750 @item show debug dwarf-line
23751 Show the current state of DWARF line table debugging.
23752 @item set debug dwarf-read
23753 @cindex DWARF Reading
23754 Turns on or off display of debugging messages related to reading
23755 DWARF debug info. The default is 0 (off).
23756 A value of 1 provides basic information.
23757 A value greater than 1 provides more verbose information.
23758 @item show debug dwarf-read
23759 Show the current state of DWARF reader debugging.
23760 @item set debug displaced
23761 @cindex displaced stepping debugging info
23762 Turns on or off display of @value{GDBN} debugging info for the
23763 displaced stepping support. The default is off.
23764 @item show debug displaced
23765 Displays the current state of displaying @value{GDBN} debugging info
23766 related to displaced stepping.
23767 @item set debug event
23768 @cindex event debugging info
23769 Turns on or off display of @value{GDBN} event debugging info. The
23771 @item show debug event
23772 Displays the current state of displaying @value{GDBN} event debugging
23774 @item set debug expression
23775 @cindex expression debugging info
23776 Turns on or off display of debugging info about @value{GDBN}
23777 expression parsing. The default is off.
23778 @item show debug expression
23779 Displays the current state of displaying debugging info about
23780 @value{GDBN} expression parsing.
23781 @item set debug fbsd-lwp
23782 @cindex FreeBSD LWP debug messages
23783 Turns on or off debugging messages from the FreeBSD LWP debug support.
23784 @item show debug fbsd-lwp
23785 Show the current state of FreeBSD LWP debugging messages.
23786 @item set debug frame
23787 @cindex frame debugging info
23788 Turns on or off display of @value{GDBN} frame debugging info. The
23790 @item show debug frame
23791 Displays the current state of displaying @value{GDBN} frame debugging
23793 @item set debug gnu-nat
23794 @cindex @sc{gnu}/Hurd debug messages
23795 Turn on or off debugging messages from the @sc{gnu}/Hurd debug support.
23796 @item show debug gnu-nat
23797 Show the current state of @sc{gnu}/Hurd debugging messages.
23798 @item set debug infrun
23799 @cindex inferior debugging info
23800 Turns on or off display of @value{GDBN} debugging info for running the inferior.
23801 The default is off. @file{infrun.c} contains GDB's runtime state machine used
23802 for implementing operations such as single-stepping the inferior.
23803 @item show debug infrun
23804 Displays the current state of @value{GDBN} inferior debugging.
23805 @item set debug jit
23806 @cindex just-in-time compilation, debugging messages
23807 Turn on or off debugging messages from JIT debug support.
23808 @item show debug jit
23809 Displays the current state of @value{GDBN} JIT debugging.
23810 @item set debug lin-lwp
23811 @cindex @sc{gnu}/Linux LWP debug messages
23812 @cindex Linux lightweight processes
23813 Turn on or off debugging messages from the Linux LWP debug support.
23814 @item show debug lin-lwp
23815 Show the current state of Linux LWP debugging messages.
23816 @item set debug linux-namespaces
23817 @cindex @sc{gnu}/Linux namespaces debug messages
23818 Turn on or off debugging messages from the Linux namespaces debug support.
23819 @item show debug linux-namespaces
23820 Show the current state of Linux namespaces debugging messages.
23821 @item set debug mach-o
23822 @cindex Mach-O symbols processing
23823 Control display of debugging messages related to Mach-O symbols
23824 processing. The default is off.
23825 @item show debug mach-o
23826 Displays the current state of displaying debugging messages related to
23827 reading of COFF/PE exported symbols.
23828 @item set debug notification
23829 @cindex remote async notification debugging info
23830 Turn on or off debugging messages about remote async notification.
23831 The default is off.
23832 @item show debug notification
23833 Displays the current state of remote async notification debugging messages.
23834 @item set debug observer
23835 @cindex observer debugging info
23836 Turns on or off display of @value{GDBN} observer debugging. This
23837 includes info such as the notification of observable events.
23838 @item show debug observer
23839 Displays the current state of observer debugging.
23840 @item set debug overload
23841 @cindex C@t{++} overload debugging info
23842 Turns on or off display of @value{GDBN} C@t{++} overload debugging
23843 info. This includes info such as ranking of functions, etc. The default
23845 @item show debug overload
23846 Displays the current state of displaying @value{GDBN} C@t{++} overload
23848 @cindex expression parser, debugging info
23849 @cindex debug expression parser
23850 @item set debug parser
23851 Turns on or off the display of expression parser debugging output.
23852 Internally, this sets the @code{yydebug} variable in the expression
23853 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
23854 details. The default is off.
23855 @item show debug parser
23856 Show the current state of expression parser debugging.
23857 @cindex packets, reporting on stdout
23858 @cindex serial connections, debugging
23859 @cindex debug remote protocol
23860 @cindex remote protocol debugging
23861 @cindex display remote packets
23862 @item set debug remote
23863 Turns on or off display of reports on all packets sent back and forth across
23864 the serial line to the remote machine. The info is printed on the
23865 @value{GDBN} standard output stream. The default is off.
23866 @item show debug remote
23867 Displays the state of display of remote packets.
23868 @item set debug serial
23869 Turns on or off display of @value{GDBN} serial debugging info. The
23871 @item show debug serial
23872 Displays the current state of displaying @value{GDBN} serial debugging
23874 @item set debug solib-frv
23875 @cindex FR-V shared-library debugging
23876 Turn on or off debugging messages for FR-V shared-library code.
23877 @item show debug solib-frv
23878 Display the current state of FR-V shared-library code debugging
23880 @item set debug symbol-lookup
23881 @cindex symbol lookup
23882 Turns on or off display of debugging messages related to symbol lookup.
23883 The default is 0 (off).
23884 A value of 1 provides basic information.
23885 A value greater than 1 provides more verbose information.
23886 @item show debug symbol-lookup
23887 Show the current state of symbol lookup debugging messages.
23888 @item set debug symfile
23889 @cindex symbol file functions
23890 Turns on or off display of debugging messages related to symbol file functions.
23891 The default is off. @xref{Files}.
23892 @item show debug symfile
23893 Show the current state of symbol file debugging messages.
23894 @item set debug symtab-create
23895 @cindex symbol table creation
23896 Turns on or off display of debugging messages related to symbol table creation.
23897 The default is 0 (off).
23898 A value of 1 provides basic information.
23899 A value greater than 1 provides more verbose information.
23900 @item show debug symtab-create
23901 Show the current state of symbol table creation debugging.
23902 @item set debug target
23903 @cindex target debugging info
23904 Turns on or off display of @value{GDBN} target debugging info. This info
23905 includes what is going on at the target level of GDB, as it happens. The
23906 default is 0. Set it to 1 to track events, and to 2 to also track the
23907 value of large memory transfers.
23908 @item show debug target
23909 Displays the current state of displaying @value{GDBN} target debugging
23911 @item set debug timestamp
23912 @cindex timestampping debugging info
23913 Turns on or off display of timestamps with @value{GDBN} debugging info.
23914 When enabled, seconds and microseconds are displayed before each debugging
23916 @item show debug timestamp
23917 Displays the current state of displaying timestamps with @value{GDBN}
23919 @item set debug varobj
23920 @cindex variable object debugging info
23921 Turns on or off display of @value{GDBN} variable object debugging
23922 info. The default is off.
23923 @item show debug varobj
23924 Displays the current state of displaying @value{GDBN} variable object
23926 @item set debug xml
23927 @cindex XML parser debugging
23928 Turn on or off debugging messages for built-in XML parsers.
23929 @item show debug xml
23930 Displays the current state of XML debugging messages.
23933 @node Other Misc Settings
23934 @section Other Miscellaneous Settings
23935 @cindex miscellaneous settings
23938 @kindex set interactive-mode
23939 @item set interactive-mode
23940 If @code{on}, forces @value{GDBN} to assume that GDB was started
23941 in a terminal. In practice, this means that @value{GDBN} should wait
23942 for the user to answer queries generated by commands entered at
23943 the command prompt. If @code{off}, forces @value{GDBN} to operate
23944 in the opposite mode, and it uses the default answers to all queries.
23945 If @code{auto} (the default), @value{GDBN} tries to determine whether
23946 its standard input is a terminal, and works in interactive-mode if it
23947 is, non-interactively otherwise.
23949 In the vast majority of cases, the debugger should be able to guess
23950 correctly which mode should be used. But this setting can be useful
23951 in certain specific cases, such as running a MinGW @value{GDBN}
23952 inside a cygwin window.
23954 @kindex show interactive-mode
23955 @item show interactive-mode
23956 Displays whether the debugger is operating in interactive mode or not.
23959 @node Extending GDB
23960 @chapter Extending @value{GDBN}
23961 @cindex extending GDB
23963 @value{GDBN} provides several mechanisms for extension.
23964 @value{GDBN} also provides the ability to automatically load
23965 extensions when it reads a file for debugging. This allows the
23966 user to automatically customize @value{GDBN} for the program
23970 * Sequences:: Canned Sequences of @value{GDBN} Commands
23971 * Python:: Extending @value{GDBN} using Python
23972 * Guile:: Extending @value{GDBN} using Guile
23973 * Auto-loading extensions:: Automatically loading extensions
23974 * Multiple Extension Languages:: Working with multiple extension languages
23975 * Aliases:: Creating new spellings of existing commands
23978 To facilitate the use of extension languages, @value{GDBN} is capable
23979 of evaluating the contents of a file. When doing so, @value{GDBN}
23980 can recognize which extension language is being used by looking at
23981 the filename extension. Files with an unrecognized filename extension
23982 are always treated as a @value{GDBN} Command Files.
23983 @xref{Command Files,, Command files}.
23985 You can control how @value{GDBN} evaluates these files with the following
23989 @kindex set script-extension
23990 @kindex show script-extension
23991 @item set script-extension off
23992 All scripts are always evaluated as @value{GDBN} Command Files.
23994 @item set script-extension soft
23995 The debugger determines the scripting language based on filename
23996 extension. If this scripting language is supported, @value{GDBN}
23997 evaluates the script using that language. Otherwise, it evaluates
23998 the file as a @value{GDBN} Command File.
24000 @item set script-extension strict
24001 The debugger determines the scripting language based on filename
24002 extension, and evaluates the script using that language. If the
24003 language is not supported, then the evaluation fails.
24005 @item show script-extension
24006 Display the current value of the @code{script-extension} option.
24011 @section Canned Sequences of Commands
24013 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
24014 Command Lists}), @value{GDBN} provides two ways to store sequences of
24015 commands for execution as a unit: user-defined commands and command
24019 * Define:: How to define your own commands
24020 * Hooks:: Hooks for user-defined commands
24021 * Command Files:: How to write scripts of commands to be stored in a file
24022 * Output:: Commands for controlled output
24023 * Auto-loading sequences:: Controlling auto-loaded command files
24027 @subsection User-defined Commands
24029 @cindex user-defined command
24030 @cindex arguments, to user-defined commands
24031 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
24032 which you assign a new name as a command. This is done with the
24033 @code{define} command. User commands may accept up to 10 arguments
24034 separated by whitespace. Arguments are accessed within the user command
24035 via @code{$arg0@dots{}$arg9}. A trivial example:
24039 print $arg0 + $arg1 + $arg2
24044 To execute the command use:
24051 This defines the command @code{adder}, which prints the sum of
24052 its three arguments. Note the arguments are text substitutions, so they may
24053 reference variables, use complex expressions, or even perform inferior
24056 @cindex argument count in user-defined commands
24057 @cindex how many arguments (user-defined commands)
24058 In addition, @code{$argc} may be used to find out how many arguments have
24059 been passed. This expands to a number in the range 0@dots{}10.
24064 print $arg0 + $arg1
24067 print $arg0 + $arg1 + $arg2
24075 @item define @var{commandname}
24076 Define a command named @var{commandname}. If there is already a command
24077 by that name, you are asked to confirm that you want to redefine it.
24078 The argument @var{commandname} may be a bare command name consisting of letters,
24079 numbers, dashes, and underscores. It may also start with any predefined
24080 prefix command. For example, @samp{define target my-target} creates
24081 a user-defined @samp{target my-target} command.
24083 The definition of the command is made up of other @value{GDBN} command lines,
24084 which are given following the @code{define} command. The end of these
24085 commands is marked by a line containing @code{end}.
24088 @kindex end@r{ (user-defined commands)}
24089 @item document @var{commandname}
24090 Document the user-defined command @var{commandname}, so that it can be
24091 accessed by @code{help}. The command @var{commandname} must already be
24092 defined. This command reads lines of documentation just as @code{define}
24093 reads the lines of the command definition, ending with @code{end}.
24094 After the @code{document} command is finished, @code{help} on command
24095 @var{commandname} displays the documentation you have written.
24097 You may use the @code{document} command again to change the
24098 documentation of a command. Redefining the command with @code{define}
24099 does not change the documentation.
24101 @kindex dont-repeat
24102 @cindex don't repeat command
24104 Used inside a user-defined command, this tells @value{GDBN} that this
24105 command should not be repeated when the user hits @key{RET}
24106 (@pxref{Command Syntax, repeat last command}).
24108 @kindex help user-defined
24109 @item help user-defined
24110 List all user-defined commands and all python commands defined in class
24111 COMAND_USER. The first line of the documentation or docstring is
24116 @itemx show user @var{commandname}
24117 Display the @value{GDBN} commands used to define @var{commandname} (but
24118 not its documentation). If no @var{commandname} is given, display the
24119 definitions for all user-defined commands.
24120 This does not work for user-defined python commands.
24122 @cindex infinite recursion in user-defined commands
24123 @kindex show max-user-call-depth
24124 @kindex set max-user-call-depth
24125 @item show max-user-call-depth
24126 @itemx set max-user-call-depth
24127 The value of @code{max-user-call-depth} controls how many recursion
24128 levels are allowed in user-defined commands before @value{GDBN} suspects an
24129 infinite recursion and aborts the command.
24130 This does not apply to user-defined python commands.
24133 In addition to the above commands, user-defined commands frequently
24134 use control flow commands, described in @ref{Command Files}.
24136 When user-defined commands are executed, the
24137 commands of the definition are not printed. An error in any command
24138 stops execution of the user-defined command.
24140 If used interactively, commands that would ask for confirmation proceed
24141 without asking when used inside a user-defined command. Many @value{GDBN}
24142 commands that normally print messages to say what they are doing omit the
24143 messages when used in a user-defined command.
24146 @subsection User-defined Command Hooks
24147 @cindex command hooks
24148 @cindex hooks, for commands
24149 @cindex hooks, pre-command
24152 You may define @dfn{hooks}, which are a special kind of user-defined
24153 command. Whenever you run the command @samp{foo}, if the user-defined
24154 command @samp{hook-foo} exists, it is executed (with no arguments)
24155 before that command.
24157 @cindex hooks, post-command
24159 A hook may also be defined which is run after the command you executed.
24160 Whenever you run the command @samp{foo}, if the user-defined command
24161 @samp{hookpost-foo} exists, it is executed (with no arguments) after
24162 that command. Post-execution hooks may exist simultaneously with
24163 pre-execution hooks, for the same command.
24165 It is valid for a hook to call the command which it hooks. If this
24166 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
24168 @c It would be nice if hookpost could be passed a parameter indicating
24169 @c if the command it hooks executed properly or not. FIXME!
24171 @kindex stop@r{, a pseudo-command}
24172 In addition, a pseudo-command, @samp{stop} exists. Defining
24173 (@samp{hook-stop}) makes the associated commands execute every time
24174 execution stops in your program: before breakpoint commands are run,
24175 displays are printed, or the stack frame is printed.
24177 For example, to ignore @code{SIGALRM} signals while
24178 single-stepping, but treat them normally during normal execution,
24183 handle SIGALRM nopass
24187 handle SIGALRM pass
24190 define hook-continue
24191 handle SIGALRM pass
24195 As a further example, to hook at the beginning and end of the @code{echo}
24196 command, and to add extra text to the beginning and end of the message,
24204 define hookpost-echo
24208 (@value{GDBP}) echo Hello World
24209 <<<---Hello World--->>>
24214 You can define a hook for any single-word command in @value{GDBN}, but
24215 not for command aliases; you should define a hook for the basic command
24216 name, e.g.@: @code{backtrace} rather than @code{bt}.
24217 @c FIXME! So how does Joe User discover whether a command is an alias
24219 You can hook a multi-word command by adding @code{hook-} or
24220 @code{hookpost-} to the last word of the command, e.g.@:
24221 @samp{define target hook-remote} to add a hook to @samp{target remote}.
24223 If an error occurs during the execution of your hook, execution of
24224 @value{GDBN} commands stops and @value{GDBN} issues a prompt
24225 (before the command that you actually typed had a chance to run).
24227 If you try to define a hook which does not match any known command, you
24228 get a warning from the @code{define} command.
24230 @node Command Files
24231 @subsection Command Files
24233 @cindex command files
24234 @cindex scripting commands
24235 A command file for @value{GDBN} is a text file made of lines that are
24236 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
24237 also be included. An empty line in a command file does nothing; it
24238 does not mean to repeat the last command, as it would from the
24241 You can request the execution of a command file with the @code{source}
24242 command. Note that the @code{source} command is also used to evaluate
24243 scripts that are not Command Files. The exact behavior can be configured
24244 using the @code{script-extension} setting.
24245 @xref{Extending GDB,, Extending GDB}.
24249 @cindex execute commands from a file
24250 @item source [-s] [-v] @var{filename}
24251 Execute the command file @var{filename}.
24254 The lines in a command file are generally executed sequentially,
24255 unless the order of execution is changed by one of the
24256 @emph{flow-control commands} described below. The commands are not
24257 printed as they are executed. An error in any command terminates
24258 execution of the command file and control is returned to the console.
24260 @value{GDBN} first searches for @var{filename} in the current directory.
24261 If the file is not found there, and @var{filename} does not specify a
24262 directory, then @value{GDBN} also looks for the file on the source search path
24263 (specified with the @samp{directory} command);
24264 except that @file{$cdir} is not searched because the compilation directory
24265 is not relevant to scripts.
24267 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
24268 on the search path even if @var{filename} specifies a directory.
24269 The search is done by appending @var{filename} to each element of the
24270 search path. So, for example, if @var{filename} is @file{mylib/myscript}
24271 and the search path contains @file{/home/user} then @value{GDBN} will
24272 look for the script @file{/home/user/mylib/myscript}.
24273 The search is also done if @var{filename} is an absolute path.
24274 For example, if @var{filename} is @file{/tmp/myscript} and
24275 the search path contains @file{/home/user} then @value{GDBN} will
24276 look for the script @file{/home/user/tmp/myscript}.
24277 For DOS-like systems, if @var{filename} contains a drive specification,
24278 it is stripped before concatenation. For example, if @var{filename} is
24279 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
24280 will look for the script @file{c:/tmp/myscript}.
24282 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
24283 each command as it is executed. The option must be given before
24284 @var{filename}, and is interpreted as part of the filename anywhere else.
24286 Commands that would ask for confirmation if used interactively proceed
24287 without asking when used in a command file. Many @value{GDBN} commands that
24288 normally print messages to say what they are doing omit the messages
24289 when called from command files.
24291 @value{GDBN} also accepts command input from standard input. In this
24292 mode, normal output goes to standard output and error output goes to
24293 standard error. Errors in a command file supplied on standard input do
24294 not terminate execution of the command file---execution continues with
24298 gdb < cmds > log 2>&1
24301 (The syntax above will vary depending on the shell used.) This example
24302 will execute commands from the file @file{cmds}. All output and errors
24303 would be directed to @file{log}.
24305 Since commands stored on command files tend to be more general than
24306 commands typed interactively, they frequently need to deal with
24307 complicated situations, such as different or unexpected values of
24308 variables and symbols, changes in how the program being debugged is
24309 built, etc. @value{GDBN} provides a set of flow-control commands to
24310 deal with these complexities. Using these commands, you can write
24311 complex scripts that loop over data structures, execute commands
24312 conditionally, etc.
24319 This command allows to include in your script conditionally executed
24320 commands. The @code{if} command takes a single argument, which is an
24321 expression to evaluate. It is followed by a series of commands that
24322 are executed only if the expression is true (its value is nonzero).
24323 There can then optionally be an @code{else} line, followed by a series
24324 of commands that are only executed if the expression was false. The
24325 end of the list is marked by a line containing @code{end}.
24329 This command allows to write loops. Its syntax is similar to
24330 @code{if}: the command takes a single argument, which is an expression
24331 to evaluate, and must be followed by the commands to execute, one per
24332 line, terminated by an @code{end}. These commands are called the
24333 @dfn{body} of the loop. The commands in the body of @code{while} are
24334 executed repeatedly as long as the expression evaluates to true.
24338 This command exits the @code{while} loop in whose body it is included.
24339 Execution of the script continues after that @code{while}s @code{end}
24342 @kindex loop_continue
24343 @item loop_continue
24344 This command skips the execution of the rest of the body of commands
24345 in the @code{while} loop in whose body it is included. Execution
24346 branches to the beginning of the @code{while} loop, where it evaluates
24347 the controlling expression.
24349 @kindex end@r{ (if/else/while commands)}
24351 Terminate the block of commands that are the body of @code{if},
24352 @code{else}, or @code{while} flow-control commands.
24357 @subsection Commands for Controlled Output
24359 During the execution of a command file or a user-defined command, normal
24360 @value{GDBN} output is suppressed; the only output that appears is what is
24361 explicitly printed by the commands in the definition. This section
24362 describes three commands useful for generating exactly the output you
24367 @item echo @var{text}
24368 @c I do not consider backslash-space a standard C escape sequence
24369 @c because it is not in ANSI.
24370 Print @var{text}. Nonprinting characters can be included in
24371 @var{text} using C escape sequences, such as @samp{\n} to print a
24372 newline. @strong{No newline is printed unless you specify one.}
24373 In addition to the standard C escape sequences, a backslash followed
24374 by a space stands for a space. This is useful for displaying a
24375 string with spaces at the beginning or the end, since leading and
24376 trailing spaces are otherwise trimmed from all arguments.
24377 To print @samp{@w{ }and foo =@w{ }}, use the command
24378 @samp{echo \@w{ }and foo = \@w{ }}.
24380 A backslash at the end of @var{text} can be used, as in C, to continue
24381 the command onto subsequent lines. For example,
24384 echo This is some text\n\
24385 which is continued\n\
24386 onto several lines.\n
24389 produces the same output as
24392 echo This is some text\n
24393 echo which is continued\n
24394 echo onto several lines.\n
24398 @item output @var{expression}
24399 Print the value of @var{expression} and nothing but that value: no
24400 newlines, no @samp{$@var{nn} = }. The value is not entered in the
24401 value history either. @xref{Expressions, ,Expressions}, for more information
24404 @item output/@var{fmt} @var{expression}
24405 Print the value of @var{expression} in format @var{fmt}. You can use
24406 the same formats as for @code{print}. @xref{Output Formats,,Output
24407 Formats}, for more information.
24410 @item printf @var{template}, @var{expressions}@dots{}
24411 Print the values of one or more @var{expressions} under the control of
24412 the string @var{template}. To print several values, make
24413 @var{expressions} be a comma-separated list of individual expressions,
24414 which may be either numbers or pointers. Their values are printed as
24415 specified by @var{template}, exactly as a C program would do by
24416 executing the code below:
24419 printf (@var{template}, @var{expressions}@dots{});
24422 As in @code{C} @code{printf}, ordinary characters in @var{template}
24423 are printed verbatim, while @dfn{conversion specification} introduced
24424 by the @samp{%} character cause subsequent @var{expressions} to be
24425 evaluated, their values converted and formatted according to type and
24426 style information encoded in the conversion specifications, and then
24429 For example, you can print two values in hex like this:
24432 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
24435 @code{printf} supports all the standard @code{C} conversion
24436 specifications, including the flags and modifiers between the @samp{%}
24437 character and the conversion letter, with the following exceptions:
24441 The argument-ordering modifiers, such as @samp{2$}, are not supported.
24444 The modifier @samp{*} is not supported for specifying precision or
24448 The @samp{'} flag (for separation of digits into groups according to
24449 @code{LC_NUMERIC'}) is not supported.
24452 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
24456 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
24459 The conversion letters @samp{a} and @samp{A} are not supported.
24463 Note that the @samp{ll} type modifier is supported only if the
24464 underlying @code{C} implementation used to build @value{GDBN} supports
24465 the @code{long long int} type, and the @samp{L} type modifier is
24466 supported only if @code{long double} type is available.
24468 As in @code{C}, @code{printf} supports simple backslash-escape
24469 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
24470 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
24471 single character. Octal and hexadecimal escape sequences are not
24474 Additionally, @code{printf} supports conversion specifications for DFP
24475 (@dfn{Decimal Floating Point}) types using the following length modifiers
24476 together with a floating point specifier.
24481 @samp{H} for printing @code{Decimal32} types.
24484 @samp{D} for printing @code{Decimal64} types.
24487 @samp{DD} for printing @code{Decimal128} types.
24490 If the underlying @code{C} implementation used to build @value{GDBN} has
24491 support for the three length modifiers for DFP types, other modifiers
24492 such as width and precision will also be available for @value{GDBN} to use.
24494 In case there is no such @code{C} support, no additional modifiers will be
24495 available and the value will be printed in the standard way.
24497 Here's an example of printing DFP types using the above conversion letters:
24499 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
24503 @item eval @var{template}, @var{expressions}@dots{}
24504 Convert the values of one or more @var{expressions} under the control of
24505 the string @var{template} to a command line, and call it.
24509 @node Auto-loading sequences
24510 @subsection Controlling auto-loading native @value{GDBN} scripts
24511 @cindex native script auto-loading
24513 When a new object file is read (for example, due to the @code{file}
24514 command, or because the inferior has loaded a shared library),
24515 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
24516 @xref{Auto-loading extensions}.
24518 Auto-loading can be enabled or disabled,
24519 and the list of auto-loaded scripts can be printed.
24522 @anchor{set auto-load gdb-scripts}
24523 @kindex set auto-load gdb-scripts
24524 @item set auto-load gdb-scripts [on|off]
24525 Enable or disable the auto-loading of canned sequences of commands scripts.
24527 @anchor{show auto-load gdb-scripts}
24528 @kindex show auto-load gdb-scripts
24529 @item show auto-load gdb-scripts
24530 Show whether auto-loading of canned sequences of commands scripts is enabled or
24533 @anchor{info auto-load gdb-scripts}
24534 @kindex info auto-load gdb-scripts
24535 @cindex print list of auto-loaded canned sequences of commands scripts
24536 @item info auto-load gdb-scripts [@var{regexp}]
24537 Print the list of all canned sequences of commands scripts that @value{GDBN}
24541 If @var{regexp} is supplied only canned sequences of commands scripts with
24542 matching names are printed.
24544 @c Python docs live in a separate file.
24545 @include python.texi
24547 @c Guile docs live in a separate file.
24548 @include guile.texi
24550 @node Auto-loading extensions
24551 @section Auto-loading extensions
24552 @cindex auto-loading extensions
24554 @value{GDBN} provides two mechanisms for automatically loading extensions
24555 when a new object file is read (for example, due to the @code{file}
24556 command, or because the inferior has loaded a shared library):
24557 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
24558 section of modern file formats like ELF.
24561 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
24562 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
24563 * Which flavor to choose?::
24566 The auto-loading feature is useful for supplying application-specific
24567 debugging commands and features.
24569 Auto-loading can be enabled or disabled,
24570 and the list of auto-loaded scripts can be printed.
24571 See the @samp{auto-loading} section of each extension language
24572 for more information.
24573 For @value{GDBN} command files see @ref{Auto-loading sequences}.
24574 For Python files see @ref{Python Auto-loading}.
24576 Note that loading of this script file also requires accordingly configured
24577 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24579 @node objfile-gdbdotext file
24580 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
24581 @cindex @file{@var{objfile}-gdb.gdb}
24582 @cindex @file{@var{objfile}-gdb.py}
24583 @cindex @file{@var{objfile}-gdb.scm}
24585 When a new object file is read, @value{GDBN} looks for a file named
24586 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
24587 where @var{objfile} is the object file's name and
24588 where @var{ext} is the file extension for the extension language:
24591 @item @file{@var{objfile}-gdb.gdb}
24592 GDB's own command language
24593 @item @file{@var{objfile}-gdb.py}
24595 @item @file{@var{objfile}-gdb.scm}
24599 @var{script-name} is formed by ensuring that the file name of @var{objfile}
24600 is absolute, following all symlinks, and resolving @code{.} and @code{..}
24601 components, and appending the @file{-gdb.@var{ext}} suffix.
24602 If this file exists and is readable, @value{GDBN} will evaluate it as a
24603 script in the specified extension language.
24605 If this file does not exist, then @value{GDBN} will look for
24606 @var{script-name} file in all of the directories as specified below.
24608 Note that loading of these files requires an accordingly configured
24609 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24611 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
24612 scripts normally according to its @file{.exe} filename. But if no scripts are
24613 found @value{GDBN} also tries script filenames matching the object file without
24614 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
24615 is attempted on any platform. This makes the script filenames compatible
24616 between Unix and MS-Windows hosts.
24619 @anchor{set auto-load scripts-directory}
24620 @kindex set auto-load scripts-directory
24621 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
24622 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
24623 may be delimited by the host platform path separator in use
24624 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
24626 Each entry here needs to be covered also by the security setting
24627 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
24629 @anchor{with-auto-load-dir}
24630 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
24631 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
24632 configuration option @option{--with-auto-load-dir}.
24634 Any reference to @file{$debugdir} will get replaced by
24635 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
24636 reference to @file{$datadir} will get replaced by @var{data-directory} which is
24637 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
24638 @file{$datadir} must be placed as a directory component --- either alone or
24639 delimited by @file{/} or @file{\} directory separators, depending on the host
24642 The list of directories uses path separator (@samp{:} on GNU and Unix
24643 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
24644 to the @env{PATH} environment variable.
24646 @anchor{show auto-load scripts-directory}
24647 @kindex show auto-load scripts-directory
24648 @item show auto-load scripts-directory
24649 Show @value{GDBN} auto-loaded scripts location.
24651 @anchor{add-auto-load-scripts-directory}
24652 @kindex add-auto-load-scripts-directory
24653 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
24654 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
24655 Multiple entries may be delimited by the host platform path separator in use.
24658 @value{GDBN} does not track which files it has already auto-loaded this way.
24659 @value{GDBN} will load the associated script every time the corresponding
24660 @var{objfile} is opened.
24661 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
24662 is evaluated more than once.
24664 @node dotdebug_gdb_scripts section
24665 @subsection The @code{.debug_gdb_scripts} section
24666 @cindex @code{.debug_gdb_scripts} section
24668 For systems using file formats like ELF and COFF,
24669 when @value{GDBN} loads a new object file
24670 it will look for a special section named @code{.debug_gdb_scripts}.
24671 If this section exists, its contents is a list of null-terminated entries
24672 specifying scripts to load. Each entry begins with a non-null prefix byte that
24673 specifies the kind of entry, typically the extension language and whether the
24674 script is in a file or inlined in @code{.debug_gdb_scripts}.
24676 The following entries are supported:
24679 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
24680 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
24681 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
24682 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
24685 @subsubsection Script File Entries
24687 If the entry specifies a file, @value{GDBN} will look for the file first
24688 in the current directory and then along the source search path
24689 (@pxref{Source Path, ,Specifying Source Directories}),
24690 except that @file{$cdir} is not searched, since the compilation
24691 directory is not relevant to scripts.
24693 File entries can be placed in section @code{.debug_gdb_scripts} with,
24694 for example, this GCC macro for Python scripts.
24697 /* Note: The "MS" section flags are to remove duplicates. */
24698 #define DEFINE_GDB_PY_SCRIPT(script_name) \
24700 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
24701 .byte 1 /* Python */\n\
24702 .asciz \"" script_name "\"\n\
24708 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
24709 Then one can reference the macro in a header or source file like this:
24712 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
24715 The script name may include directories if desired.
24717 Note that loading of this script file also requires accordingly configured
24718 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24720 If the macro invocation is put in a header, any application or library
24721 using this header will get a reference to the specified script,
24722 and with the use of @code{"MS"} attributes on the section, the linker
24723 will remove duplicates.
24725 @subsubsection Script Text Entries
24727 Script text entries allow to put the executable script in the entry
24728 itself instead of loading it from a file.
24729 The first line of the entry, everything after the prefix byte and up to
24730 the first newline (@code{0xa}) character, is the script name, and must not
24731 contain any kind of space character, e.g., spaces or tabs.
24732 The rest of the entry, up to the trailing null byte, is the script to
24733 execute in the specified language. The name needs to be unique among
24734 all script names, as @value{GDBN} executes each script only once based
24737 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
24741 #include "symcat.h"
24742 #include "gdb/section-scripts.h"
24744 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
24745 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
24746 ".ascii \"gdb.inlined-script\\n\"\n"
24747 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
24748 ".ascii \" def __init__ (self):\\n\"\n"
24749 ".ascii \" super (test_cmd, self).__init__ ("
24750 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
24751 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
24752 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
24753 ".ascii \"test_cmd ()\\n\"\n"
24759 Loading of inlined scripts requires a properly configured
24760 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24761 The path to specify in @code{auto-load safe-path} is the path of the file
24762 containing the @code{.debug_gdb_scripts} section.
24764 @node Which flavor to choose?
24765 @subsection Which flavor to choose?
24767 Given the multiple ways of auto-loading extensions, it might not always
24768 be clear which one to choose. This section provides some guidance.
24771 Benefits of the @file{-gdb.@var{ext}} way:
24775 Can be used with file formats that don't support multiple sections.
24778 Ease of finding scripts for public libraries.
24780 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
24781 in the source search path.
24782 For publicly installed libraries, e.g., @file{libstdc++}, there typically
24783 isn't a source directory in which to find the script.
24786 Doesn't require source code additions.
24790 Benefits of the @code{.debug_gdb_scripts} way:
24794 Works with static linking.
24796 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
24797 trigger their loading. When an application is statically linked the only
24798 objfile available is the executable, and it is cumbersome to attach all the
24799 scripts from all the input libraries to the executable's
24800 @file{-gdb.@var{ext}} script.
24803 Works with classes that are entirely inlined.
24805 Some classes can be entirely inlined, and thus there may not be an associated
24806 shared library to attach a @file{-gdb.@var{ext}} script to.
24809 Scripts needn't be copied out of the source tree.
24811 In some circumstances, apps can be built out of large collections of internal
24812 libraries, and the build infrastructure necessary to install the
24813 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
24814 cumbersome. It may be easier to specify the scripts in the
24815 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
24816 top of the source tree to the source search path.
24819 @node Multiple Extension Languages
24820 @section Multiple Extension Languages
24822 The Guile and Python extension languages do not share any state,
24823 and generally do not interfere with each other.
24824 There are some things to be aware of, however.
24826 @subsection Python comes first
24828 Python was @value{GDBN}'s first extension language, and to avoid breaking
24829 existing behaviour Python comes first. This is generally solved by the
24830 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
24831 extension languages, and when it makes a call to an extension language,
24832 (say to pretty-print a value), it tries each in turn until an extension
24833 language indicates it has performed the request (e.g., has returned the
24834 pretty-printed form of a value).
24835 This extends to errors while performing such requests: If an error happens
24836 while, for example, trying to pretty-print an object then the error is
24837 reported and any following extension languages are not tried.
24840 @section Creating new spellings of existing commands
24841 @cindex aliases for commands
24843 It is often useful to define alternate spellings of existing commands.
24844 For example, if a new @value{GDBN} command defined in Python has
24845 a long name to type, it is handy to have an abbreviated version of it
24846 that involves less typing.
24848 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
24849 of the @samp{step} command even though it is otherwise an ambiguous
24850 abbreviation of other commands like @samp{set} and @samp{show}.
24852 Aliases are also used to provide shortened or more common versions
24853 of multi-word commands. For example, @value{GDBN} provides the
24854 @samp{tty} alias of the @samp{set inferior-tty} command.
24856 You can define a new alias with the @samp{alias} command.
24861 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
24865 @var{ALIAS} specifies the name of the new alias.
24866 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
24869 @var{COMMAND} specifies the name of an existing command
24870 that is being aliased.
24872 The @samp{-a} option specifies that the new alias is an abbreviation
24873 of the command. Abbreviations are not shown in command
24874 lists displayed by the @samp{help} command.
24876 The @samp{--} option specifies the end of options,
24877 and is useful when @var{ALIAS} begins with a dash.
24879 Here is a simple example showing how to make an abbreviation
24880 of a command so that there is less to type.
24881 Suppose you were tired of typing @samp{disas}, the current
24882 shortest unambiguous abbreviation of the @samp{disassemble} command
24883 and you wanted an even shorter version named @samp{di}.
24884 The following will accomplish this.
24887 (gdb) alias -a di = disas
24890 Note that aliases are different from user-defined commands.
24891 With a user-defined command, you also need to write documentation
24892 for it with the @samp{document} command.
24893 An alias automatically picks up the documentation of the existing command.
24895 Here is an example where we make @samp{elms} an abbreviation of
24896 @samp{elements} in the @samp{set print elements} command.
24897 This is to show that you can make an abbreviation of any part
24901 (gdb) alias -a set print elms = set print elements
24902 (gdb) alias -a show print elms = show print elements
24903 (gdb) set p elms 20
24905 Limit on string chars or array elements to print is 200.
24908 Note that if you are defining an alias of a @samp{set} command,
24909 and you want to have an alias for the corresponding @samp{show}
24910 command, then you need to define the latter separately.
24912 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
24913 @var{ALIAS}, just as they are normally.
24916 (gdb) alias -a set pr elms = set p ele
24919 Finally, here is an example showing the creation of a one word
24920 alias for a more complex command.
24921 This creates alias @samp{spe} of the command @samp{set print elements}.
24924 (gdb) alias spe = set print elements
24929 @chapter Command Interpreters
24930 @cindex command interpreters
24932 @value{GDBN} supports multiple command interpreters, and some command
24933 infrastructure to allow users or user interface writers to switch
24934 between interpreters or run commands in other interpreters.
24936 @value{GDBN} currently supports two command interpreters, the console
24937 interpreter (sometimes called the command-line interpreter or @sc{cli})
24938 and the machine interface interpreter (or @sc{gdb/mi}). This manual
24939 describes both of these interfaces in great detail.
24941 By default, @value{GDBN} will start with the console interpreter.
24942 However, the user may choose to start @value{GDBN} with another
24943 interpreter by specifying the @option{-i} or @option{--interpreter}
24944 startup options. Defined interpreters include:
24948 @cindex console interpreter
24949 The traditional console or command-line interpreter. This is the most often
24950 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
24951 @value{GDBN} will use this interpreter.
24954 @cindex mi interpreter
24955 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
24956 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
24957 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
24961 @cindex mi2 interpreter
24962 The current @sc{gdb/mi} interface.
24965 @cindex mi1 interpreter
24966 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
24970 @cindex invoke another interpreter
24972 @kindex interpreter-exec
24973 You may execute commands in any interpreter from the current
24974 interpreter using the appropriate command. If you are running the
24975 console interpreter, simply use the @code{interpreter-exec} command:
24978 interpreter-exec mi "-data-list-register-names"
24981 @sc{gdb/mi} has a similar command, although it is only available in versions of
24982 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
24984 Note that @code{interpreter-exec} only changes the interpreter for the
24985 duration of the specified command. It does not change the interpreter
24988 @cindex start a new independent interpreter
24990 Although you may only choose a single interpreter at startup, it is
24991 possible to run an independent interpreter on a specified input/output
24992 device (usually a tty).
24994 For example, consider a debugger GUI or IDE that wants to provide a
24995 @value{GDBN} console view. It may do so by embedding a terminal
24996 emulator widget in its GUI, starting @value{GDBN} in the traditional
24997 command-line mode with stdin/stdout/stderr redirected to that
24998 terminal, and then creating an MI interpreter running on a specified
24999 input/output device. The console interpreter created by @value{GDBN}
25000 at startup handles commands the user types in the terminal widget,
25001 while the GUI controls and synchronizes state with @value{GDBN} using
25002 the separate MI interpreter.
25004 To start a new secondary @dfn{user interface} running MI, use the
25005 @code{new-ui} command:
25008 @cindex new user interface
25010 new-ui @var{interpreter} @var{tty}
25013 The @var{interpreter} parameter specifies the interpreter to run.
25014 This accepts the same values as the @code{interpreter-exec} command.
25015 For example, @samp{console}, @samp{mi}, @samp{mi2}, etc. The
25016 @var{tty} parameter specifies the name of the bidirectional file the
25017 interpreter uses for input/output, usually the name of a
25018 pseudoterminal slave on Unix systems. For example:
25021 (@value{GDBP}) new-ui mi /dev/pts/9
25025 runs an MI interpreter on @file{/dev/pts/9}.
25028 @chapter @value{GDBN} Text User Interface
25030 @cindex Text User Interface
25033 * TUI Overview:: TUI overview
25034 * TUI Keys:: TUI key bindings
25035 * TUI Single Key Mode:: TUI single key mode
25036 * TUI Commands:: TUI-specific commands
25037 * TUI Configuration:: TUI configuration variables
25040 The @value{GDBN} Text User Interface (TUI) is a terminal
25041 interface which uses the @code{curses} library to show the source
25042 file, the assembly output, the program registers and @value{GDBN}
25043 commands in separate text windows. The TUI mode is supported only
25044 on platforms where a suitable version of the @code{curses} library
25047 The TUI mode is enabled by default when you invoke @value{GDBN} as
25048 @samp{@value{GDBP} -tui}.
25049 You can also switch in and out of TUI mode while @value{GDBN} runs by
25050 using various TUI commands and key bindings, such as @command{tui
25051 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
25052 @ref{TUI Keys, ,TUI Key Bindings}.
25055 @section TUI Overview
25057 In TUI mode, @value{GDBN} can display several text windows:
25061 This window is the @value{GDBN} command window with the @value{GDBN}
25062 prompt and the @value{GDBN} output. The @value{GDBN} input is still
25063 managed using readline.
25066 The source window shows the source file of the program. The current
25067 line and active breakpoints are displayed in this window.
25070 The assembly window shows the disassembly output of the program.
25073 This window shows the processor registers. Registers are highlighted
25074 when their values change.
25077 The source and assembly windows show the current program position
25078 by highlighting the current line and marking it with a @samp{>} marker.
25079 Breakpoints are indicated with two markers. The first marker
25080 indicates the breakpoint type:
25084 Breakpoint which was hit at least once.
25087 Breakpoint which was never hit.
25090 Hardware breakpoint which was hit at least once.
25093 Hardware breakpoint which was never hit.
25096 The second marker indicates whether the breakpoint is enabled or not:
25100 Breakpoint is enabled.
25103 Breakpoint is disabled.
25106 The source, assembly and register windows are updated when the current
25107 thread changes, when the frame changes, or when the program counter
25110 These windows are not all visible at the same time. The command
25111 window is always visible. The others can be arranged in several
25122 source and assembly,
25125 source and registers, or
25128 assembly and registers.
25131 A status line above the command window shows the following information:
25135 Indicates the current @value{GDBN} target.
25136 (@pxref{Targets, ,Specifying a Debugging Target}).
25139 Gives the current process or thread number.
25140 When no process is being debugged, this field is set to @code{No process}.
25143 Gives the current function name for the selected frame.
25144 The name is demangled if demangling is turned on (@pxref{Print Settings}).
25145 When there is no symbol corresponding to the current program counter,
25146 the string @code{??} is displayed.
25149 Indicates the current line number for the selected frame.
25150 When the current line number is not known, the string @code{??} is displayed.
25153 Indicates the current program counter address.
25157 @section TUI Key Bindings
25158 @cindex TUI key bindings
25160 The TUI installs several key bindings in the readline keymaps
25161 @ifset SYSTEM_READLINE
25162 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
25164 @ifclear SYSTEM_READLINE
25165 (@pxref{Command Line Editing}).
25167 The following key bindings are installed for both TUI mode and the
25168 @value{GDBN} standard mode.
25177 Enter or leave the TUI mode. When leaving the TUI mode,
25178 the curses window management stops and @value{GDBN} operates using
25179 its standard mode, writing on the terminal directly. When reentering
25180 the TUI mode, control is given back to the curses windows.
25181 The screen is then refreshed.
25185 Use a TUI layout with only one window. The layout will
25186 either be @samp{source} or @samp{assembly}. When the TUI mode
25187 is not active, it will switch to the TUI mode.
25189 Think of this key binding as the Emacs @kbd{C-x 1} binding.
25193 Use a TUI layout with at least two windows. When the current
25194 layout already has two windows, the next layout with two windows is used.
25195 When a new layout is chosen, one window will always be common to the
25196 previous layout and the new one.
25198 Think of it as the Emacs @kbd{C-x 2} binding.
25202 Change the active window. The TUI associates several key bindings
25203 (like scrolling and arrow keys) with the active window. This command
25204 gives the focus to the next TUI window.
25206 Think of it as the Emacs @kbd{C-x o} binding.
25210 Switch in and out of the TUI SingleKey mode that binds single
25211 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
25214 The following key bindings only work in the TUI mode:
25219 Scroll the active window one page up.
25223 Scroll the active window one page down.
25227 Scroll the active window one line up.
25231 Scroll the active window one line down.
25235 Scroll the active window one column left.
25239 Scroll the active window one column right.
25243 Refresh the screen.
25246 Because the arrow keys scroll the active window in the TUI mode, they
25247 are not available for their normal use by readline unless the command
25248 window has the focus. When another window is active, you must use
25249 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
25250 and @kbd{C-f} to control the command window.
25252 @node TUI Single Key Mode
25253 @section TUI Single Key Mode
25254 @cindex TUI single key mode
25256 The TUI also provides a @dfn{SingleKey} mode, which binds several
25257 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
25258 switch into this mode, where the following key bindings are used:
25261 @kindex c @r{(SingleKey TUI key)}
25265 @kindex d @r{(SingleKey TUI key)}
25269 @kindex f @r{(SingleKey TUI key)}
25273 @kindex n @r{(SingleKey TUI key)}
25277 @kindex q @r{(SingleKey TUI key)}
25279 exit the SingleKey mode.
25281 @kindex r @r{(SingleKey TUI key)}
25285 @kindex s @r{(SingleKey TUI key)}
25289 @kindex u @r{(SingleKey TUI key)}
25293 @kindex v @r{(SingleKey TUI key)}
25297 @kindex w @r{(SingleKey TUI key)}
25302 Other keys temporarily switch to the @value{GDBN} command prompt.
25303 The key that was pressed is inserted in the editing buffer so that
25304 it is possible to type most @value{GDBN} commands without interaction
25305 with the TUI SingleKey mode. Once the command is entered the TUI
25306 SingleKey mode is restored. The only way to permanently leave
25307 this mode is by typing @kbd{q} or @kbd{C-x s}.
25311 @section TUI-specific Commands
25312 @cindex TUI commands
25314 The TUI has specific commands to control the text windows.
25315 These commands are always available, even when @value{GDBN} is not in
25316 the TUI mode. When @value{GDBN} is in the standard mode, most
25317 of these commands will automatically switch to the TUI mode.
25319 Note that if @value{GDBN}'s @code{stdout} is not connected to a
25320 terminal, or @value{GDBN} has been started with the machine interface
25321 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
25322 these commands will fail with an error, because it would not be
25323 possible or desirable to enable curses window management.
25328 Activate TUI mode. The last active TUI window layout will be used if
25329 TUI mode has prevsiouly been used in the current debugging session,
25330 otherwise a default layout is used.
25333 @kindex tui disable
25334 Disable TUI mode, returning to the console interpreter.
25338 List and give the size of all displayed windows.
25340 @item layout @var{name}
25342 Changes which TUI windows are displayed. In each layout the command
25343 window is always displayed, the @var{name} parameter controls which
25344 additional windows are displayed, and can be any of the following:
25348 Display the next layout.
25351 Display the previous layout.
25354 Display the source and command windows.
25357 Display the assembly and command windows.
25360 Display the source, assembly, and command windows.
25363 When in @code{src} layout display the register, source, and command
25364 windows. When in @code{asm} or @code{split} layout display the
25365 register, assembler, and command windows.
25368 @item focus @var{name}
25370 Changes which TUI window is currently active for scrolling. The
25371 @var{name} parameter can be any of the following:
25375 Make the next window active for scrolling.
25378 Make the previous window active for scrolling.
25381 Make the source window active for scrolling.
25384 Make the assembly window active for scrolling.
25387 Make the register window active for scrolling.
25390 Make the command window active for scrolling.
25395 Refresh the screen. This is similar to typing @kbd{C-L}.
25397 @item tui reg @var{group}
25399 Changes the register group displayed in the tui register window to
25400 @var{group}. If the register window is not currently displayed this
25401 command will cause the register window to be displayed. The list of
25402 register groups, as well as their order is target specific. The
25403 following groups are available on most targets:
25406 Repeatedly selecting this group will cause the display to cycle
25407 through all of the available register groups.
25410 Repeatedly selecting this group will cause the display to cycle
25411 through all of the available register groups in the reverse order to
25415 Display the general registers.
25417 Display the floating point registers.
25419 Display the system registers.
25421 Display the vector registers.
25423 Display all registers.
25428 Update the source window and the current execution point.
25430 @item winheight @var{name} +@var{count}
25431 @itemx winheight @var{name} -@var{count}
25433 Change the height of the window @var{name} by @var{count}
25434 lines. Positive counts increase the height, while negative counts
25435 decrease it. The @var{name} parameter can be one of @code{src} (the
25436 source window), @code{cmd} (the command window), @code{asm} (the
25437 disassembly window), or @code{regs} (the register display window).
25439 @item tabset @var{nchars}
25441 Set the width of tab stops to be @var{nchars} characters. This
25442 setting affects the display of TAB characters in the source and
25446 @node TUI Configuration
25447 @section TUI Configuration Variables
25448 @cindex TUI configuration variables
25450 Several configuration variables control the appearance of TUI windows.
25453 @item set tui border-kind @var{kind}
25454 @kindex set tui border-kind
25455 Select the border appearance for the source, assembly and register windows.
25456 The possible values are the following:
25459 Use a space character to draw the border.
25462 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
25465 Use the Alternate Character Set to draw the border. The border is
25466 drawn using character line graphics if the terminal supports them.
25469 @item set tui border-mode @var{mode}
25470 @kindex set tui border-mode
25471 @itemx set tui active-border-mode @var{mode}
25472 @kindex set tui active-border-mode
25473 Select the display attributes for the borders of the inactive windows
25474 or the active window. The @var{mode} can be one of the following:
25477 Use normal attributes to display the border.
25483 Use reverse video mode.
25486 Use half bright mode.
25488 @item half-standout
25489 Use half bright and standout mode.
25492 Use extra bright or bold mode.
25494 @item bold-standout
25495 Use extra bright or bold and standout mode.
25500 @chapter Using @value{GDBN} under @sc{gnu} Emacs
25503 @cindex @sc{gnu} Emacs
25504 A special interface allows you to use @sc{gnu} Emacs to view (and
25505 edit) the source files for the program you are debugging with
25508 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
25509 executable file you want to debug as an argument. This command starts
25510 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
25511 created Emacs buffer.
25512 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
25514 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
25519 All ``terminal'' input and output goes through an Emacs buffer, called
25522 This applies both to @value{GDBN} commands and their output, and to the input
25523 and output done by the program you are debugging.
25525 This is useful because it means that you can copy the text of previous
25526 commands and input them again; you can even use parts of the output
25529 All the facilities of Emacs' Shell mode are available for interacting
25530 with your program. In particular, you can send signals the usual
25531 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
25535 @value{GDBN} displays source code through Emacs.
25537 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
25538 source file for that frame and puts an arrow (@samp{=>}) at the
25539 left margin of the current line. Emacs uses a separate buffer for
25540 source display, and splits the screen to show both your @value{GDBN} session
25543 Explicit @value{GDBN} @code{list} or search commands still produce output as
25544 usual, but you probably have no reason to use them from Emacs.
25547 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
25548 a graphical mode, enabled by default, which provides further buffers
25549 that can control the execution and describe the state of your program.
25550 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
25552 If you specify an absolute file name when prompted for the @kbd{M-x
25553 gdb} argument, then Emacs sets your current working directory to where
25554 your program resides. If you only specify the file name, then Emacs
25555 sets your current working directory to the directory associated
25556 with the previous buffer. In this case, @value{GDBN} may find your
25557 program by searching your environment's @code{PATH} variable, but on
25558 some operating systems it might not find the source. So, although the
25559 @value{GDBN} input and output session proceeds normally, the auxiliary
25560 buffer does not display the current source and line of execution.
25562 The initial working directory of @value{GDBN} is printed on the top
25563 line of the GUD buffer and this serves as a default for the commands
25564 that specify files for @value{GDBN} to operate on. @xref{Files,
25565 ,Commands to Specify Files}.
25567 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
25568 need to call @value{GDBN} by a different name (for example, if you
25569 keep several configurations around, with different names) you can
25570 customize the Emacs variable @code{gud-gdb-command-name} to run the
25573 In the GUD buffer, you can use these special Emacs commands in
25574 addition to the standard Shell mode commands:
25578 Describe the features of Emacs' GUD Mode.
25581 Execute to another source line, like the @value{GDBN} @code{step} command; also
25582 update the display window to show the current file and location.
25585 Execute to next source line in this function, skipping all function
25586 calls, like the @value{GDBN} @code{next} command. Then update the display window
25587 to show the current file and location.
25590 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
25591 display window accordingly.
25594 Execute until exit from the selected stack frame, like the @value{GDBN}
25595 @code{finish} command.
25598 Continue execution of your program, like the @value{GDBN} @code{continue}
25602 Go up the number of frames indicated by the numeric argument
25603 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
25604 like the @value{GDBN} @code{up} command.
25607 Go down the number of frames indicated by the numeric argument, like the
25608 @value{GDBN} @code{down} command.
25611 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
25612 tells @value{GDBN} to set a breakpoint on the source line point is on.
25614 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
25615 separate frame which shows a backtrace when the GUD buffer is current.
25616 Move point to any frame in the stack and type @key{RET} to make it
25617 become the current frame and display the associated source in the
25618 source buffer. Alternatively, click @kbd{Mouse-2} to make the
25619 selected frame become the current one. In graphical mode, the
25620 speedbar displays watch expressions.
25622 If you accidentally delete the source-display buffer, an easy way to get
25623 it back is to type the command @code{f} in the @value{GDBN} buffer, to
25624 request a frame display; when you run under Emacs, this recreates
25625 the source buffer if necessary to show you the context of the current
25628 The source files displayed in Emacs are in ordinary Emacs buffers
25629 which are visiting the source files in the usual way. You can edit
25630 the files with these buffers if you wish; but keep in mind that @value{GDBN}
25631 communicates with Emacs in terms of line numbers. If you add or
25632 delete lines from the text, the line numbers that @value{GDBN} knows cease
25633 to correspond properly with the code.
25635 A more detailed description of Emacs' interaction with @value{GDBN} is
25636 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
25640 @chapter The @sc{gdb/mi} Interface
25642 @unnumberedsec Function and Purpose
25644 @cindex @sc{gdb/mi}, its purpose
25645 @sc{gdb/mi} is a line based machine oriented text interface to
25646 @value{GDBN} and is activated by specifying using the
25647 @option{--interpreter} command line option (@pxref{Mode Options}). It
25648 is specifically intended to support the development of systems which
25649 use the debugger as just one small component of a larger system.
25651 This chapter is a specification of the @sc{gdb/mi} interface. It is written
25652 in the form of a reference manual.
25654 Note that @sc{gdb/mi} is still under construction, so some of the
25655 features described below are incomplete and subject to change
25656 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
25658 @unnumberedsec Notation and Terminology
25660 @cindex notational conventions, for @sc{gdb/mi}
25661 This chapter uses the following notation:
25665 @code{|} separates two alternatives.
25668 @code{[ @var{something} ]} indicates that @var{something} is optional:
25669 it may or may not be given.
25672 @code{( @var{group} )*} means that @var{group} inside the parentheses
25673 may repeat zero or more times.
25676 @code{( @var{group} )+} means that @var{group} inside the parentheses
25677 may repeat one or more times.
25680 @code{"@var{string}"} means a literal @var{string}.
25684 @heading Dependencies
25688 * GDB/MI General Design::
25689 * GDB/MI Command Syntax::
25690 * GDB/MI Compatibility with CLI::
25691 * GDB/MI Development and Front Ends::
25692 * GDB/MI Output Records::
25693 * GDB/MI Simple Examples::
25694 * GDB/MI Command Description Format::
25695 * GDB/MI Breakpoint Commands::
25696 * GDB/MI Catchpoint Commands::
25697 * GDB/MI Program Context::
25698 * GDB/MI Thread Commands::
25699 * GDB/MI Ada Tasking Commands::
25700 * GDB/MI Program Execution::
25701 * GDB/MI Stack Manipulation::
25702 * GDB/MI Variable Objects::
25703 * GDB/MI Data Manipulation::
25704 * GDB/MI Tracepoint Commands::
25705 * GDB/MI Symbol Query::
25706 * GDB/MI File Commands::
25708 * GDB/MI Kod Commands::
25709 * GDB/MI Memory Overlay Commands::
25710 * GDB/MI Signal Handling Commands::
25712 * GDB/MI Target Manipulation::
25713 * GDB/MI File Transfer Commands::
25714 * GDB/MI Ada Exceptions Commands::
25715 * GDB/MI Support Commands::
25716 * GDB/MI Miscellaneous Commands::
25719 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25720 @node GDB/MI General Design
25721 @section @sc{gdb/mi} General Design
25722 @cindex GDB/MI General Design
25724 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
25725 parts---commands sent to @value{GDBN}, responses to those commands
25726 and notifications. Each command results in exactly one response,
25727 indicating either successful completion of the command, or an error.
25728 For the commands that do not resume the target, the response contains the
25729 requested information. For the commands that resume the target, the
25730 response only indicates whether the target was successfully resumed.
25731 Notifications is the mechanism for reporting changes in the state of the
25732 target, or in @value{GDBN} state, that cannot conveniently be associated with
25733 a command and reported as part of that command response.
25735 The important examples of notifications are:
25739 Exec notifications. These are used to report changes in
25740 target state---when a target is resumed, or stopped. It would not
25741 be feasible to include this information in response of resuming
25742 commands, because one resume commands can result in multiple events in
25743 different threads. Also, quite some time may pass before any event
25744 happens in the target, while a frontend needs to know whether the resuming
25745 command itself was successfully executed.
25748 Console output, and status notifications. Console output
25749 notifications are used to report output of CLI commands, as well as
25750 diagnostics for other commands. Status notifications are used to
25751 report the progress of a long-running operation. Naturally, including
25752 this information in command response would mean no output is produced
25753 until the command is finished, which is undesirable.
25756 General notifications. Commands may have various side effects on
25757 the @value{GDBN} or target state beyond their official purpose. For example,
25758 a command may change the selected thread. Although such changes can
25759 be included in command response, using notification allows for more
25760 orthogonal frontend design.
25764 There's no guarantee that whenever an MI command reports an error,
25765 @value{GDBN} or the target are in any specific state, and especially,
25766 the state is not reverted to the state before the MI command was
25767 processed. Therefore, whenever an MI command results in an error,
25768 we recommend that the frontend refreshes all the information shown in
25769 the user interface.
25773 * Context management::
25774 * Asynchronous and non-stop modes::
25778 @node Context management
25779 @subsection Context management
25781 @subsubsection Threads and Frames
25783 In most cases when @value{GDBN} accesses the target, this access is
25784 done in context of a specific thread and frame (@pxref{Frames}).
25785 Often, even when accessing global data, the target requires that a thread
25786 be specified. The CLI interface maintains the selected thread and frame,
25787 and supplies them to target on each command. This is convenient,
25788 because a command line user would not want to specify that information
25789 explicitly on each command, and because user interacts with
25790 @value{GDBN} via a single terminal, so no confusion is possible as
25791 to what thread and frame are the current ones.
25793 In the case of MI, the concept of selected thread and frame is less
25794 useful. First, a frontend can easily remember this information
25795 itself. Second, a graphical frontend can have more than one window,
25796 each one used for debugging a different thread, and the frontend might
25797 want to access additional threads for internal purposes. This
25798 increases the risk that by relying on implicitly selected thread, the
25799 frontend may be operating on a wrong one. Therefore, each MI command
25800 should explicitly specify which thread and frame to operate on. To
25801 make it possible, each MI command accepts the @samp{--thread} and
25802 @samp{--frame} options, the value to each is @value{GDBN} global
25803 identifier for thread and frame to operate on.
25805 Usually, each top-level window in a frontend allows the user to select
25806 a thread and a frame, and remembers the user selection for further
25807 operations. However, in some cases @value{GDBN} may suggest that the
25808 current thread be changed. For example, when stopping on a breakpoint
25809 it is reasonable to switch to the thread where breakpoint is hit. For
25810 another example, if the user issues the CLI @samp{thread} command via
25811 the frontend, it is desirable to change the frontend's selected thread to the
25812 one specified by user. @value{GDBN} communicates the suggestion to
25813 change current thread using the @samp{=thread-selected} notification.
25814 No such notification is available for the selected frame at the moment.
25816 Note that historically, MI shares the selected thread with CLI, so
25817 frontends used the @code{-thread-select} to execute commands in the
25818 right context. However, getting this to work right is cumbersome. The
25819 simplest way is for frontend to emit @code{-thread-select} command
25820 before every command. This doubles the number of commands that need
25821 to be sent. The alternative approach is to suppress @code{-thread-select}
25822 if the selected thread in @value{GDBN} is supposed to be identical to the
25823 thread the frontend wants to operate on. However, getting this
25824 optimization right can be tricky. In particular, if the frontend
25825 sends several commands to @value{GDBN}, and one of the commands changes the
25826 selected thread, then the behaviour of subsequent commands will
25827 change. So, a frontend should either wait for response from such
25828 problematic commands, or explicitly add @code{-thread-select} for
25829 all subsequent commands. No frontend is known to do this exactly
25830 right, so it is suggested to just always pass the @samp{--thread} and
25831 @samp{--frame} options.
25833 @subsubsection Language
25835 The execution of several commands depends on which language is selected.
25836 By default, the current language (@pxref{show language}) is used.
25837 But for commands known to be language-sensitive, it is recommended
25838 to use the @samp{--language} option. This option takes one argument,
25839 which is the name of the language to use while executing the command.
25843 -data-evaluate-expression --language c "sizeof (void*)"
25848 The valid language names are the same names accepted by the
25849 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
25850 @samp{local} or @samp{unknown}.
25852 @node Asynchronous and non-stop modes
25853 @subsection Asynchronous command execution and non-stop mode
25855 On some targets, @value{GDBN} is capable of processing MI commands
25856 even while the target is running. This is called @dfn{asynchronous
25857 command execution} (@pxref{Background Execution}). The frontend may
25858 specify a preferrence for asynchronous execution using the
25859 @code{-gdb-set mi-async 1} command, which should be emitted before
25860 either running the executable or attaching to the target. After the
25861 frontend has started the executable or attached to the target, it can
25862 find if asynchronous execution is enabled using the
25863 @code{-list-target-features} command.
25866 @item -gdb-set mi-async on
25867 @item -gdb-set mi-async off
25868 Set whether MI is in asynchronous mode.
25870 When @code{off}, which is the default, MI execution commands (e.g.,
25871 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
25872 for the program to stop before processing further commands.
25874 When @code{on}, MI execution commands are background execution
25875 commands (e.g., @code{-exec-continue} becomes the equivalent of the
25876 @code{c&} CLI command), and so @value{GDBN} is capable of processing
25877 MI commands even while the target is running.
25879 @item -gdb-show mi-async
25880 Show whether MI asynchronous mode is enabled.
25883 Note: In @value{GDBN} version 7.7 and earlier, this option was called
25884 @code{target-async} instead of @code{mi-async}, and it had the effect
25885 of both putting MI in asynchronous mode and making CLI background
25886 commands possible. CLI background commands are now always possible
25887 ``out of the box'' if the target supports them. The old spelling is
25888 kept as a deprecated alias for backwards compatibility.
25890 Even if @value{GDBN} can accept a command while target is running,
25891 many commands that access the target do not work when the target is
25892 running. Therefore, asynchronous command execution is most useful
25893 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
25894 it is possible to examine the state of one thread, while other threads
25897 When a given thread is running, MI commands that try to access the
25898 target in the context of that thread may not work, or may work only on
25899 some targets. In particular, commands that try to operate on thread's
25900 stack will not work, on any target. Commands that read memory, or
25901 modify breakpoints, may work or not work, depending on the target. Note
25902 that even commands that operate on global state, such as @code{print},
25903 @code{set}, and breakpoint commands, still access the target in the
25904 context of a specific thread, so frontend should try to find a
25905 stopped thread and perform the operation on that thread (using the
25906 @samp{--thread} option).
25908 Which commands will work in the context of a running thread is
25909 highly target dependent. However, the two commands
25910 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
25911 to find the state of a thread, will always work.
25913 @node Thread groups
25914 @subsection Thread groups
25915 @value{GDBN} may be used to debug several processes at the same time.
25916 On some platfroms, @value{GDBN} may support debugging of several
25917 hardware systems, each one having several cores with several different
25918 processes running on each core. This section describes the MI
25919 mechanism to support such debugging scenarios.
25921 The key observation is that regardless of the structure of the
25922 target, MI can have a global list of threads, because most commands that
25923 accept the @samp{--thread} option do not need to know what process that
25924 thread belongs to. Therefore, it is not necessary to introduce
25925 neither additional @samp{--process} option, nor an notion of the
25926 current process in the MI interface. The only strictly new feature
25927 that is required is the ability to find how the threads are grouped
25930 To allow the user to discover such grouping, and to support arbitrary
25931 hierarchy of machines/cores/processes, MI introduces the concept of a
25932 @dfn{thread group}. Thread group is a collection of threads and other
25933 thread groups. A thread group always has a string identifier, a type,
25934 and may have additional attributes specific to the type. A new
25935 command, @code{-list-thread-groups}, returns the list of top-level
25936 thread groups, which correspond to processes that @value{GDBN} is
25937 debugging at the moment. By passing an identifier of a thread group
25938 to the @code{-list-thread-groups} command, it is possible to obtain
25939 the members of specific thread group.
25941 To allow the user to easily discover processes, and other objects, he
25942 wishes to debug, a concept of @dfn{available thread group} is
25943 introduced. Available thread group is an thread group that
25944 @value{GDBN} is not debugging, but that can be attached to, using the
25945 @code{-target-attach} command. The list of available top-level thread
25946 groups can be obtained using @samp{-list-thread-groups --available}.
25947 In general, the content of a thread group may be only retrieved only
25948 after attaching to that thread group.
25950 Thread groups are related to inferiors (@pxref{Inferiors and
25951 Programs}). Each inferior corresponds to a thread group of a special
25952 type @samp{process}, and some additional operations are permitted on
25953 such thread groups.
25955 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25956 @node GDB/MI Command Syntax
25957 @section @sc{gdb/mi} Command Syntax
25960 * GDB/MI Input Syntax::
25961 * GDB/MI Output Syntax::
25964 @node GDB/MI Input Syntax
25965 @subsection @sc{gdb/mi} Input Syntax
25967 @cindex input syntax for @sc{gdb/mi}
25968 @cindex @sc{gdb/mi}, input syntax
25970 @item @var{command} @expansion{}
25971 @code{@var{cli-command} | @var{mi-command}}
25973 @item @var{cli-command} @expansion{}
25974 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
25975 @var{cli-command} is any existing @value{GDBN} CLI command.
25977 @item @var{mi-command} @expansion{}
25978 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
25979 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
25981 @item @var{token} @expansion{}
25982 "any sequence of digits"
25984 @item @var{option} @expansion{}
25985 @code{"-" @var{parameter} [ " " @var{parameter} ]}
25987 @item @var{parameter} @expansion{}
25988 @code{@var{non-blank-sequence} | @var{c-string}}
25990 @item @var{operation} @expansion{}
25991 @emph{any of the operations described in this chapter}
25993 @item @var{non-blank-sequence} @expansion{}
25994 @emph{anything, provided it doesn't contain special characters such as
25995 "-", @var{nl}, """ and of course " "}
25997 @item @var{c-string} @expansion{}
25998 @code{""" @var{seven-bit-iso-c-string-content} """}
26000 @item @var{nl} @expansion{}
26009 The CLI commands are still handled by the @sc{mi} interpreter; their
26010 output is described below.
26013 The @code{@var{token}}, when present, is passed back when the command
26017 Some @sc{mi} commands accept optional arguments as part of the parameter
26018 list. Each option is identified by a leading @samp{-} (dash) and may be
26019 followed by an optional argument parameter. Options occur first in the
26020 parameter list and can be delimited from normal parameters using
26021 @samp{--} (this is useful when some parameters begin with a dash).
26028 We want easy access to the existing CLI syntax (for debugging).
26031 We want it to be easy to spot a @sc{mi} operation.
26034 @node GDB/MI Output Syntax
26035 @subsection @sc{gdb/mi} Output Syntax
26037 @cindex output syntax of @sc{gdb/mi}
26038 @cindex @sc{gdb/mi}, output syntax
26039 The output from @sc{gdb/mi} consists of zero or more out-of-band records
26040 followed, optionally, by a single result record. This result record
26041 is for the most recent command. The sequence of output records is
26042 terminated by @samp{(gdb)}.
26044 If an input command was prefixed with a @code{@var{token}} then the
26045 corresponding output for that command will also be prefixed by that same
26049 @item @var{output} @expansion{}
26050 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
26052 @item @var{result-record} @expansion{}
26053 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
26055 @item @var{out-of-band-record} @expansion{}
26056 @code{@var{async-record} | @var{stream-record}}
26058 @item @var{async-record} @expansion{}
26059 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
26061 @item @var{exec-async-output} @expansion{}
26062 @code{[ @var{token} ] "*" @var{async-output nl}}
26064 @item @var{status-async-output} @expansion{}
26065 @code{[ @var{token} ] "+" @var{async-output nl}}
26067 @item @var{notify-async-output} @expansion{}
26068 @code{[ @var{token} ] "=" @var{async-output nl}}
26070 @item @var{async-output} @expansion{}
26071 @code{@var{async-class} ( "," @var{result} )*}
26073 @item @var{result-class} @expansion{}
26074 @code{"done" | "running" | "connected" | "error" | "exit"}
26076 @item @var{async-class} @expansion{}
26077 @code{"stopped" | @var{others}} (where @var{others} will be added
26078 depending on the needs---this is still in development).
26080 @item @var{result} @expansion{}
26081 @code{ @var{variable} "=" @var{value}}
26083 @item @var{variable} @expansion{}
26084 @code{ @var{string} }
26086 @item @var{value} @expansion{}
26087 @code{ @var{const} | @var{tuple} | @var{list} }
26089 @item @var{const} @expansion{}
26090 @code{@var{c-string}}
26092 @item @var{tuple} @expansion{}
26093 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
26095 @item @var{list} @expansion{}
26096 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
26097 @var{result} ( "," @var{result} )* "]" }
26099 @item @var{stream-record} @expansion{}
26100 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
26102 @item @var{console-stream-output} @expansion{}
26103 @code{"~" @var{c-string nl}}
26105 @item @var{target-stream-output} @expansion{}
26106 @code{"@@" @var{c-string nl}}
26108 @item @var{log-stream-output} @expansion{}
26109 @code{"&" @var{c-string nl}}
26111 @item @var{nl} @expansion{}
26114 @item @var{token} @expansion{}
26115 @emph{any sequence of digits}.
26123 All output sequences end in a single line containing a period.
26126 The @code{@var{token}} is from the corresponding request. Note that
26127 for all async output, while the token is allowed by the grammar and
26128 may be output by future versions of @value{GDBN} for select async
26129 output messages, it is generally omitted. Frontends should treat
26130 all async output as reporting general changes in the state of the
26131 target and there should be no need to associate async output to any
26135 @cindex status output in @sc{gdb/mi}
26136 @var{status-async-output} contains on-going status information about the
26137 progress of a slow operation. It can be discarded. All status output is
26138 prefixed by @samp{+}.
26141 @cindex async output in @sc{gdb/mi}
26142 @var{exec-async-output} contains asynchronous state change on the target
26143 (stopped, started, disappeared). All async output is prefixed by
26147 @cindex notify output in @sc{gdb/mi}
26148 @var{notify-async-output} contains supplementary information that the
26149 client should handle (e.g., a new breakpoint information). All notify
26150 output is prefixed by @samp{=}.
26153 @cindex console output in @sc{gdb/mi}
26154 @var{console-stream-output} is output that should be displayed as is in the
26155 console. It is the textual response to a CLI command. All the console
26156 output is prefixed by @samp{~}.
26159 @cindex target output in @sc{gdb/mi}
26160 @var{target-stream-output} is the output produced by the target program.
26161 All the target output is prefixed by @samp{@@}.
26164 @cindex log output in @sc{gdb/mi}
26165 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
26166 instance messages that should be displayed as part of an error log. All
26167 the log output is prefixed by @samp{&}.
26170 @cindex list output in @sc{gdb/mi}
26171 New @sc{gdb/mi} commands should only output @var{lists} containing
26177 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
26178 details about the various output records.
26180 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26181 @node GDB/MI Compatibility with CLI
26182 @section @sc{gdb/mi} Compatibility with CLI
26184 @cindex compatibility, @sc{gdb/mi} and CLI
26185 @cindex @sc{gdb/mi}, compatibility with CLI
26187 For the developers convenience CLI commands can be entered directly,
26188 but there may be some unexpected behaviour. For example, commands
26189 that query the user will behave as if the user replied yes, breakpoint
26190 command lists are not executed and some CLI commands, such as
26191 @code{if}, @code{when} and @code{define}, prompt for further input with
26192 @samp{>}, which is not valid MI output.
26194 This feature may be removed at some stage in the future and it is
26195 recommended that front ends use the @code{-interpreter-exec} command
26196 (@pxref{-interpreter-exec}).
26198 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26199 @node GDB/MI Development and Front Ends
26200 @section @sc{gdb/mi} Development and Front Ends
26201 @cindex @sc{gdb/mi} development
26203 The application which takes the MI output and presents the state of the
26204 program being debugged to the user is called a @dfn{front end}.
26206 Although @sc{gdb/mi} is still incomplete, it is currently being used
26207 by a variety of front ends to @value{GDBN}. This makes it difficult
26208 to introduce new functionality without breaking existing usage. This
26209 section tries to minimize the problems by describing how the protocol
26212 Some changes in MI need not break a carefully designed front end, and
26213 for these the MI version will remain unchanged. The following is a
26214 list of changes that may occur within one level, so front ends should
26215 parse MI output in a way that can handle them:
26219 New MI commands may be added.
26222 New fields may be added to the output of any MI command.
26225 The range of values for fields with specified values, e.g.,
26226 @code{in_scope} (@pxref{-var-update}) may be extended.
26228 @c The format of field's content e.g type prefix, may change so parse it
26229 @c at your own risk. Yes, in general?
26231 @c The order of fields may change? Shouldn't really matter but it might
26232 @c resolve inconsistencies.
26235 If the changes are likely to break front ends, the MI version level
26236 will be increased by one. This will allow the front end to parse the
26237 output according to the MI version. Apart from mi0, new versions of
26238 @value{GDBN} will not support old versions of MI and it will be the
26239 responsibility of the front end to work with the new one.
26241 @c Starting with mi3, add a new command -mi-version that prints the MI
26244 The best way to avoid unexpected changes in MI that might break your front
26245 end is to make your project known to @value{GDBN} developers and
26246 follow development on @email{gdb@@sourceware.org} and
26247 @email{gdb-patches@@sourceware.org}.
26248 @cindex mailing lists
26250 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26251 @node GDB/MI Output Records
26252 @section @sc{gdb/mi} Output Records
26255 * GDB/MI Result Records::
26256 * GDB/MI Stream Records::
26257 * GDB/MI Async Records::
26258 * GDB/MI Breakpoint Information::
26259 * GDB/MI Frame Information::
26260 * GDB/MI Thread Information::
26261 * GDB/MI Ada Exception Information::
26264 @node GDB/MI Result Records
26265 @subsection @sc{gdb/mi} Result Records
26267 @cindex result records in @sc{gdb/mi}
26268 @cindex @sc{gdb/mi}, result records
26269 In addition to a number of out-of-band notifications, the response to a
26270 @sc{gdb/mi} command includes one of the following result indications:
26274 @item "^done" [ "," @var{results} ]
26275 The synchronous operation was successful, @code{@var{results}} are the return
26280 This result record is equivalent to @samp{^done}. Historically, it
26281 was output instead of @samp{^done} if the command has resumed the
26282 target. This behaviour is maintained for backward compatibility, but
26283 all frontends should treat @samp{^done} and @samp{^running}
26284 identically and rely on the @samp{*running} output record to determine
26285 which threads are resumed.
26289 @value{GDBN} has connected to a remote target.
26291 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
26293 The operation failed. The @code{msg=@var{c-string}} variable contains
26294 the corresponding error message.
26296 If present, the @code{code=@var{c-string}} variable provides an error
26297 code on which consumers can rely on to detect the corresponding
26298 error condition. At present, only one error code is defined:
26301 @item "undefined-command"
26302 Indicates that the command causing the error does not exist.
26307 @value{GDBN} has terminated.
26311 @node GDB/MI Stream Records
26312 @subsection @sc{gdb/mi} Stream Records
26314 @cindex @sc{gdb/mi}, stream records
26315 @cindex stream records in @sc{gdb/mi}
26316 @value{GDBN} internally maintains a number of output streams: the console, the
26317 target, and the log. The output intended for each of these streams is
26318 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
26320 Each stream record begins with a unique @dfn{prefix character} which
26321 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
26322 Syntax}). In addition to the prefix, each stream record contains a
26323 @code{@var{string-output}}. This is either raw text (with an implicit new
26324 line) or a quoted C string (which does not contain an implicit newline).
26327 @item "~" @var{string-output}
26328 The console output stream contains text that should be displayed in the
26329 CLI console window. It contains the textual responses to CLI commands.
26331 @item "@@" @var{string-output}
26332 The target output stream contains any textual output from the running
26333 target. This is only present when GDB's event loop is truly
26334 asynchronous, which is currently only the case for remote targets.
26336 @item "&" @var{string-output}
26337 The log stream contains debugging messages being produced by @value{GDBN}'s
26341 @node GDB/MI Async Records
26342 @subsection @sc{gdb/mi} Async Records
26344 @cindex async records in @sc{gdb/mi}
26345 @cindex @sc{gdb/mi}, async records
26346 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
26347 additional changes that have occurred. Those changes can either be a
26348 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
26349 target activity (e.g., target stopped).
26351 The following is the list of possible async records:
26355 @item *running,thread-id="@var{thread}"
26356 The target is now running. The @var{thread} field can be the global
26357 thread ID of the the thread that is now running, and it can be
26358 @samp{all} if all threads are running. The frontend should assume
26359 that no interaction with a running thread is possible after this
26360 notification is produced. The frontend should not assume that this
26361 notification is output only once for any command. @value{GDBN} may
26362 emit this notification several times, either for different threads,
26363 because it cannot resume all threads together, or even for a single
26364 thread, if the thread must be stepped though some code before letting
26367 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
26368 The target has stopped. The @var{reason} field can have one of the
26372 @item breakpoint-hit
26373 A breakpoint was reached.
26374 @item watchpoint-trigger
26375 A watchpoint was triggered.
26376 @item read-watchpoint-trigger
26377 A read watchpoint was triggered.
26378 @item access-watchpoint-trigger
26379 An access watchpoint was triggered.
26380 @item function-finished
26381 An -exec-finish or similar CLI command was accomplished.
26382 @item location-reached
26383 An -exec-until or similar CLI command was accomplished.
26384 @item watchpoint-scope
26385 A watchpoint has gone out of scope.
26386 @item end-stepping-range
26387 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
26388 similar CLI command was accomplished.
26389 @item exited-signalled
26390 The inferior exited because of a signal.
26392 The inferior exited.
26393 @item exited-normally
26394 The inferior exited normally.
26395 @item signal-received
26396 A signal was received by the inferior.
26398 The inferior has stopped due to a library being loaded or unloaded.
26399 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
26400 set or when a @code{catch load} or @code{catch unload} catchpoint is
26401 in use (@pxref{Set Catchpoints}).
26403 The inferior has forked. This is reported when @code{catch fork}
26404 (@pxref{Set Catchpoints}) has been used.
26406 The inferior has vforked. This is reported in when @code{catch vfork}
26407 (@pxref{Set Catchpoints}) has been used.
26408 @item syscall-entry
26409 The inferior entered a system call. This is reported when @code{catch
26410 syscall} (@pxref{Set Catchpoints}) has been used.
26411 @item syscall-return
26412 The inferior returned from a system call. This is reported when
26413 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
26415 The inferior called @code{exec}. This is reported when @code{catch exec}
26416 (@pxref{Set Catchpoints}) has been used.
26419 The @var{id} field identifies the global thread ID of the thread
26420 that directly caused the stop -- for example by hitting a breakpoint.
26421 Depending on whether all-stop
26422 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
26423 stop all threads, or only the thread that directly triggered the stop.
26424 If all threads are stopped, the @var{stopped} field will have the
26425 value of @code{"all"}. Otherwise, the value of the @var{stopped}
26426 field will be a list of thread identifiers. Presently, this list will
26427 always include a single thread, but frontend should be prepared to see
26428 several threads in the list. The @var{core} field reports the
26429 processor core on which the stop event has happened. This field may be absent
26430 if such information is not available.
26432 @item =thread-group-added,id="@var{id}"
26433 @itemx =thread-group-removed,id="@var{id}"
26434 A thread group was either added or removed. The @var{id} field
26435 contains the @value{GDBN} identifier of the thread group. When a thread
26436 group is added, it generally might not be associated with a running
26437 process. When a thread group is removed, its id becomes invalid and
26438 cannot be used in any way.
26440 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
26441 A thread group became associated with a running program,
26442 either because the program was just started or the thread group
26443 was attached to a program. The @var{id} field contains the
26444 @value{GDBN} identifier of the thread group. The @var{pid} field
26445 contains process identifier, specific to the operating system.
26447 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
26448 A thread group is no longer associated with a running program,
26449 either because the program has exited, or because it was detached
26450 from. The @var{id} field contains the @value{GDBN} identifier of the
26451 thread group. The @var{code} field is the exit code of the inferior; it exists
26452 only when the inferior exited with some code.
26454 @item =thread-created,id="@var{id}",group-id="@var{gid}"
26455 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
26456 A thread either was created, or has exited. The @var{id} field
26457 contains the global @value{GDBN} identifier of the thread. The @var{gid}
26458 field identifies the thread group this thread belongs to.
26460 @item =thread-selected,id="@var{id}"
26461 Informs that the selected thread was changed as result of the last
26462 command. This notification is not emitted as result of @code{-thread-select}
26463 command but is emitted whenever an MI command that is not documented
26464 to change the selected thread actually changes it. In particular,
26465 invoking, directly or indirectly (via user-defined command), the CLI
26466 @code{thread} command, will generate this notification.
26468 We suggest that in response to this notification, front ends
26469 highlight the selected thread and cause subsequent commands to apply to
26472 @item =library-loaded,...
26473 Reports that a new library file was loaded by the program. This
26474 notification has 4 fields---@var{id}, @var{target-name},
26475 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
26476 opaque identifier of the library. For remote debugging case,
26477 @var{target-name} and @var{host-name} fields give the name of the
26478 library file on the target, and on the host respectively. For native
26479 debugging, both those fields have the same value. The
26480 @var{symbols-loaded} field is emitted only for backward compatibility
26481 and should not be relied on to convey any useful information. The
26482 @var{thread-group} field, if present, specifies the id of the thread
26483 group in whose context the library was loaded. If the field is
26484 absent, it means the library was loaded in the context of all present
26487 @item =library-unloaded,...
26488 Reports that a library was unloaded by the program. This notification
26489 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
26490 the same meaning as for the @code{=library-loaded} notification.
26491 The @var{thread-group} field, if present, specifies the id of the
26492 thread group in whose context the library was unloaded. If the field is
26493 absent, it means the library was unloaded in the context of all present
26496 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
26497 @itemx =traceframe-changed,end
26498 Reports that the trace frame was changed and its new number is
26499 @var{tfnum}. The number of the tracepoint associated with this trace
26500 frame is @var{tpnum}.
26502 @item =tsv-created,name=@var{name},initial=@var{initial}
26503 Reports that the new trace state variable @var{name} is created with
26504 initial value @var{initial}.
26506 @item =tsv-deleted,name=@var{name}
26507 @itemx =tsv-deleted
26508 Reports that the trace state variable @var{name} is deleted or all
26509 trace state variables are deleted.
26511 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
26512 Reports that the trace state variable @var{name} is modified with
26513 the initial value @var{initial}. The current value @var{current} of
26514 trace state variable is optional and is reported if the current
26515 value of trace state variable is known.
26517 @item =breakpoint-created,bkpt=@{...@}
26518 @itemx =breakpoint-modified,bkpt=@{...@}
26519 @itemx =breakpoint-deleted,id=@var{number}
26520 Reports that a breakpoint was created, modified, or deleted,
26521 respectively. Only user-visible breakpoints are reported to the MI
26524 The @var{bkpt} argument is of the same form as returned by the various
26525 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
26526 @var{number} is the ordinal number of the breakpoint.
26528 Note that if a breakpoint is emitted in the result record of a
26529 command, then it will not also be emitted in an async record.
26531 @item =record-started,thread-group="@var{id}",method="@var{method}"[,format="@var{format}"]
26532 @itemx =record-stopped,thread-group="@var{id}"
26533 Execution log recording was either started or stopped on an
26534 inferior. The @var{id} is the @value{GDBN} identifier of the thread
26535 group corresponding to the affected inferior.
26537 The @var{method} field indicates the method used to record execution. If the
26538 method in use supports multiple recording formats, @var{format} will be present
26539 and contain the currently used format. @xref{Process Record and Replay}
26540 for existing method and format values.
26542 @item =cmd-param-changed,param=@var{param},value=@var{value}
26543 Reports that a parameter of the command @code{set @var{param}} is
26544 changed to @var{value}. In the multi-word @code{set} command,
26545 the @var{param} is the whole parameter list to @code{set} command.
26546 For example, In command @code{set check type on}, @var{param}
26547 is @code{check type} and @var{value} is @code{on}.
26549 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
26550 Reports that bytes from @var{addr} to @var{data} + @var{len} were
26551 written in an inferior. The @var{id} is the identifier of the
26552 thread group corresponding to the affected inferior. The optional
26553 @code{type="code"} part is reported if the memory written to holds
26557 @node GDB/MI Breakpoint Information
26558 @subsection @sc{gdb/mi} Breakpoint Information
26560 When @value{GDBN} reports information about a breakpoint, a
26561 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
26566 The breakpoint number. For a breakpoint that represents one location
26567 of a multi-location breakpoint, this will be a dotted pair, like
26571 The type of the breakpoint. For ordinary breakpoints this will be
26572 @samp{breakpoint}, but many values are possible.
26575 If the type of the breakpoint is @samp{catchpoint}, then this
26576 indicates the exact type of catchpoint.
26579 This is the breakpoint disposition---either @samp{del}, meaning that
26580 the breakpoint will be deleted at the next stop, or @samp{keep},
26581 meaning that the breakpoint will not be deleted.
26584 This indicates whether the breakpoint is enabled, in which case the
26585 value is @samp{y}, or disabled, in which case the value is @samp{n}.
26586 Note that this is not the same as the field @code{enable}.
26589 The address of the breakpoint. This may be a hexidecimal number,
26590 giving the address; or the string @samp{<PENDING>}, for a pending
26591 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
26592 multiple locations. This field will not be present if no address can
26593 be determined. For example, a watchpoint does not have an address.
26596 If known, the function in which the breakpoint appears.
26597 If not known, this field is not present.
26600 The name of the source file which contains this function, if known.
26601 If not known, this field is not present.
26604 The full file name of the source file which contains this function, if
26605 known. If not known, this field is not present.
26608 The line number at which this breakpoint appears, if known.
26609 If not known, this field is not present.
26612 If the source file is not known, this field may be provided. If
26613 provided, this holds the address of the breakpoint, possibly followed
26617 If this breakpoint is pending, this field is present and holds the
26618 text used to set the breakpoint, as entered by the user.
26621 Where this breakpoint's condition is evaluated, either @samp{host} or
26625 If this is a thread-specific breakpoint, then this identifies the
26626 thread in which the breakpoint can trigger.
26629 If this breakpoint is restricted to a particular Ada task, then this
26630 field will hold the task identifier.
26633 If the breakpoint is conditional, this is the condition expression.
26636 The ignore count of the breakpoint.
26639 The enable count of the breakpoint.
26641 @item traceframe-usage
26644 @item static-tracepoint-marker-string-id
26645 For a static tracepoint, the name of the static tracepoint marker.
26648 For a masked watchpoint, this is the mask.
26651 A tracepoint's pass count.
26653 @item original-location
26654 The location of the breakpoint as originally specified by the user.
26655 This field is optional.
26658 The number of times the breakpoint has been hit.
26661 This field is only given for tracepoints. This is either @samp{y},
26662 meaning that the tracepoint is installed, or @samp{n}, meaning that it
26666 Some extra data, the exact contents of which are type-dependent.
26670 For example, here is what the output of @code{-break-insert}
26671 (@pxref{GDB/MI Breakpoint Commands}) might be:
26674 -> -break-insert main
26675 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26676 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26677 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
26682 @node GDB/MI Frame Information
26683 @subsection @sc{gdb/mi} Frame Information
26685 Response from many MI commands includes an information about stack
26686 frame. This information is a tuple that may have the following
26691 The level of the stack frame. The innermost frame has the level of
26692 zero. This field is always present.
26695 The name of the function corresponding to the frame. This field may
26696 be absent if @value{GDBN} is unable to determine the function name.
26699 The code address for the frame. This field is always present.
26702 The name of the source files that correspond to the frame's code
26703 address. This field may be absent.
26706 The source line corresponding to the frames' code address. This field
26710 The name of the binary file (either executable or shared library) the
26711 corresponds to the frame's code address. This field may be absent.
26715 @node GDB/MI Thread Information
26716 @subsection @sc{gdb/mi} Thread Information
26718 Whenever @value{GDBN} has to report an information about a thread, it
26719 uses a tuple with the following fields:
26723 The global numeric id assigned to the thread by @value{GDBN}. This field is
26727 Target-specific string identifying the thread. This field is always present.
26730 Additional information about the thread provided by the target.
26731 It is supposed to be human-readable and not interpreted by the
26732 frontend. This field is optional.
26735 Either @samp{stopped} or @samp{running}, depending on whether the
26736 thread is presently running. This field is always present.
26739 The value of this field is an integer number of the processor core the
26740 thread was last seen on. This field is optional.
26743 @node GDB/MI Ada Exception Information
26744 @subsection @sc{gdb/mi} Ada Exception Information
26746 Whenever a @code{*stopped} record is emitted because the program
26747 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
26748 @value{GDBN} provides the name of the exception that was raised via
26749 the @code{exception-name} field.
26751 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26752 @node GDB/MI Simple Examples
26753 @section Simple Examples of @sc{gdb/mi} Interaction
26754 @cindex @sc{gdb/mi}, simple examples
26756 This subsection presents several simple examples of interaction using
26757 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
26758 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
26759 the output received from @sc{gdb/mi}.
26761 Note the line breaks shown in the examples are here only for
26762 readability, they don't appear in the real output.
26764 @subheading Setting a Breakpoint
26766 Setting a breakpoint generates synchronous output which contains detailed
26767 information of the breakpoint.
26770 -> -break-insert main
26771 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26772 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26773 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
26778 @subheading Program Execution
26780 Program execution generates asynchronous records and MI gives the
26781 reason that execution stopped.
26787 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
26788 frame=@{addr="0x08048564",func="main",
26789 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
26790 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
26795 <- *stopped,reason="exited-normally"
26799 @subheading Quitting @value{GDBN}
26801 Quitting @value{GDBN} just prints the result class @samp{^exit}.
26809 Please note that @samp{^exit} is printed immediately, but it might
26810 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
26811 performs necessary cleanups, including killing programs being debugged
26812 or disconnecting from debug hardware, so the frontend should wait till
26813 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
26814 fails to exit in reasonable time.
26816 @subheading A Bad Command
26818 Here's what happens if you pass a non-existent command:
26822 <- ^error,msg="Undefined MI command: rubbish"
26827 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26828 @node GDB/MI Command Description Format
26829 @section @sc{gdb/mi} Command Description Format
26831 The remaining sections describe blocks of commands. Each block of
26832 commands is laid out in a fashion similar to this section.
26834 @subheading Motivation
26836 The motivation for this collection of commands.
26838 @subheading Introduction
26840 A brief introduction to this collection of commands as a whole.
26842 @subheading Commands
26844 For each command in the block, the following is described:
26846 @subsubheading Synopsis
26849 -command @var{args}@dots{}
26852 @subsubheading Result
26854 @subsubheading @value{GDBN} Command
26856 The corresponding @value{GDBN} CLI command(s), if any.
26858 @subsubheading Example
26860 Example(s) formatted for readability. Some of the described commands have
26861 not been implemented yet and these are labeled N.A.@: (not available).
26864 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26865 @node GDB/MI Breakpoint Commands
26866 @section @sc{gdb/mi} Breakpoint Commands
26868 @cindex breakpoint commands for @sc{gdb/mi}
26869 @cindex @sc{gdb/mi}, breakpoint commands
26870 This section documents @sc{gdb/mi} commands for manipulating
26873 @subheading The @code{-break-after} Command
26874 @findex -break-after
26876 @subsubheading Synopsis
26879 -break-after @var{number} @var{count}
26882 The breakpoint number @var{number} is not in effect until it has been
26883 hit @var{count} times. To see how this is reflected in the output of
26884 the @samp{-break-list} command, see the description of the
26885 @samp{-break-list} command below.
26887 @subsubheading @value{GDBN} Command
26889 The corresponding @value{GDBN} command is @samp{ignore}.
26891 @subsubheading Example
26896 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26897 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26898 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
26906 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26907 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26908 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26909 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26910 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26911 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26912 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26913 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26914 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26915 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
26920 @subheading The @code{-break-catch} Command
26921 @findex -break-catch
26924 @subheading The @code{-break-commands} Command
26925 @findex -break-commands
26927 @subsubheading Synopsis
26930 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
26933 Specifies the CLI commands that should be executed when breakpoint
26934 @var{number} is hit. The parameters @var{command1} to @var{commandN}
26935 are the commands. If no command is specified, any previously-set
26936 commands are cleared. @xref{Break Commands}. Typical use of this
26937 functionality is tracing a program, that is, printing of values of
26938 some variables whenever breakpoint is hit and then continuing.
26940 @subsubheading @value{GDBN} Command
26942 The corresponding @value{GDBN} command is @samp{commands}.
26944 @subsubheading Example
26949 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26950 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26951 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
26954 -break-commands 1 "print v" "continue"
26959 @subheading The @code{-break-condition} Command
26960 @findex -break-condition
26962 @subsubheading Synopsis
26965 -break-condition @var{number} @var{expr}
26968 Breakpoint @var{number} will stop the program only if the condition in
26969 @var{expr} is true. The condition becomes part of the
26970 @samp{-break-list} output (see the description of the @samp{-break-list}
26973 @subsubheading @value{GDBN} Command
26975 The corresponding @value{GDBN} command is @samp{condition}.
26977 @subsubheading Example
26981 -break-condition 1 1
26985 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26986 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26987 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26988 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26989 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26990 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26991 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26992 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26993 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26994 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
26998 @subheading The @code{-break-delete} Command
26999 @findex -break-delete
27001 @subsubheading Synopsis
27004 -break-delete ( @var{breakpoint} )+
27007 Delete the breakpoint(s) whose number(s) are specified in the argument
27008 list. This is obviously reflected in the breakpoint list.
27010 @subsubheading @value{GDBN} Command
27012 The corresponding @value{GDBN} command is @samp{delete}.
27014 @subsubheading Example
27022 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27023 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27024 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27025 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27026 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27027 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27028 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27033 @subheading The @code{-break-disable} Command
27034 @findex -break-disable
27036 @subsubheading Synopsis
27039 -break-disable ( @var{breakpoint} )+
27042 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
27043 break list is now set to @samp{n} for the named @var{breakpoint}(s).
27045 @subsubheading @value{GDBN} Command
27047 The corresponding @value{GDBN} command is @samp{disable}.
27049 @subsubheading Example
27057 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27058 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27059 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27060 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27061 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27062 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27063 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27064 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
27065 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27066 line="5",thread-groups=["i1"],times="0"@}]@}
27070 @subheading The @code{-break-enable} Command
27071 @findex -break-enable
27073 @subsubheading Synopsis
27076 -break-enable ( @var{breakpoint} )+
27079 Enable (previously disabled) @var{breakpoint}(s).
27081 @subsubheading @value{GDBN} Command
27083 The corresponding @value{GDBN} command is @samp{enable}.
27085 @subsubheading Example
27093 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27094 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27095 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27096 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27097 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27098 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27099 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27100 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27101 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27102 line="5",thread-groups=["i1"],times="0"@}]@}
27106 @subheading The @code{-break-info} Command
27107 @findex -break-info
27109 @subsubheading Synopsis
27112 -break-info @var{breakpoint}
27116 Get information about a single breakpoint.
27118 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
27119 Information}, for details on the format of each breakpoint in the
27122 @subsubheading @value{GDBN} Command
27124 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
27126 @subsubheading Example
27129 @subheading The @code{-break-insert} Command
27130 @findex -break-insert
27131 @anchor{-break-insert}
27133 @subsubheading Synopsis
27136 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
27137 [ -c @var{condition} ] [ -i @var{ignore-count} ]
27138 [ -p @var{thread-id} ] [ @var{location} ]
27142 If specified, @var{location}, can be one of:
27145 @item linespec location
27146 A linespec location. @xref{Linespec Locations}.
27148 @item explicit location
27149 An explicit location. @sc{gdb/mi} explicit locations are
27150 analogous to the CLI's explicit locations using the option names
27151 listed below. @xref{Explicit Locations}.
27154 @item --source @var{filename}
27155 The source file name of the location. This option requires the use
27156 of either @samp{--function} or @samp{--line}.
27158 @item --function @var{function}
27159 The name of a function or method.
27161 @item --label @var{label}
27162 The name of a label.
27164 @item --line @var{lineoffset}
27165 An absolute or relative line offset from the start of the location.
27168 @item address location
27169 An address location, *@var{address}. @xref{Address Locations}.
27173 The possible optional parameters of this command are:
27177 Insert a temporary breakpoint.
27179 Insert a hardware breakpoint.
27181 If @var{location} cannot be parsed (for example if it
27182 refers to unknown files or functions), create a pending
27183 breakpoint. Without this flag, @value{GDBN} will report
27184 an error, and won't create a breakpoint, if @var{location}
27187 Create a disabled breakpoint.
27189 Create a tracepoint. @xref{Tracepoints}. When this parameter
27190 is used together with @samp{-h}, a fast tracepoint is created.
27191 @item -c @var{condition}
27192 Make the breakpoint conditional on @var{condition}.
27193 @item -i @var{ignore-count}
27194 Initialize the @var{ignore-count}.
27195 @item -p @var{thread-id}
27196 Restrict the breakpoint to the thread with the specified global
27200 @subsubheading Result
27202 @xref{GDB/MI Breakpoint Information}, for details on the format of the
27203 resulting breakpoint.
27205 Note: this format is open to change.
27206 @c An out-of-band breakpoint instead of part of the result?
27208 @subsubheading @value{GDBN} Command
27210 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
27211 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
27213 @subsubheading Example
27218 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
27219 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
27222 -break-insert -t foo
27223 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
27224 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
27228 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27229 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27230 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27231 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27232 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27233 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27234 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27235 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27236 addr="0x0001072c", func="main",file="recursive2.c",
27237 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
27239 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
27240 addr="0x00010774",func="foo",file="recursive2.c",
27241 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
27244 @c -break-insert -r foo.*
27245 @c ~int foo(int, int);
27246 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
27247 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
27252 @subheading The @code{-dprintf-insert} Command
27253 @findex -dprintf-insert
27255 @subsubheading Synopsis
27258 -dprintf-insert [ -t ] [ -f ] [ -d ]
27259 [ -c @var{condition} ] [ -i @var{ignore-count} ]
27260 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
27265 If supplied, @var{location} may be specified the same way as for
27266 the @code{-break-insert} command. @xref{-break-insert}.
27268 The possible optional parameters of this command are:
27272 Insert a temporary breakpoint.
27274 If @var{location} cannot be parsed (for example, if it
27275 refers to unknown files or functions), create a pending
27276 breakpoint. Without this flag, @value{GDBN} will report
27277 an error, and won't create a breakpoint, if @var{location}
27280 Create a disabled breakpoint.
27281 @item -c @var{condition}
27282 Make the breakpoint conditional on @var{condition}.
27283 @item -i @var{ignore-count}
27284 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
27285 to @var{ignore-count}.
27286 @item -p @var{thread-id}
27287 Restrict the breakpoint to the thread with the specified global
27291 @subsubheading Result
27293 @xref{GDB/MI Breakpoint Information}, for details on the format of the
27294 resulting breakpoint.
27296 @c An out-of-band breakpoint instead of part of the result?
27298 @subsubheading @value{GDBN} Command
27300 The corresponding @value{GDBN} command is @samp{dprintf}.
27302 @subsubheading Example
27306 4-dprintf-insert foo "At foo entry\n"
27307 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
27308 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
27309 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
27310 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
27311 original-location="foo"@}
27313 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
27314 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
27315 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
27316 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
27317 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
27318 original-location="mi-dprintf.c:26"@}
27322 @subheading The @code{-break-list} Command
27323 @findex -break-list
27325 @subsubheading Synopsis
27331 Displays the list of inserted breakpoints, showing the following fields:
27335 number of the breakpoint
27337 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
27339 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
27342 is the breakpoint enabled or no: @samp{y} or @samp{n}
27344 memory location at which the breakpoint is set
27346 logical location of the breakpoint, expressed by function name, file
27348 @item Thread-groups
27349 list of thread groups to which this breakpoint applies
27351 number of times the breakpoint has been hit
27354 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
27355 @code{body} field is an empty list.
27357 @subsubheading @value{GDBN} Command
27359 The corresponding @value{GDBN} command is @samp{info break}.
27361 @subsubheading Example
27366 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27367 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27368 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27369 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27370 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27371 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27372 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27373 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27374 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
27376 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27377 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
27378 line="13",thread-groups=["i1"],times="0"@}]@}
27382 Here's an example of the result when there are no breakpoints:
27387 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27388 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27389 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27390 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27391 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27392 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27393 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27398 @subheading The @code{-break-passcount} Command
27399 @findex -break-passcount
27401 @subsubheading Synopsis
27404 -break-passcount @var{tracepoint-number} @var{passcount}
27407 Set the passcount for tracepoint @var{tracepoint-number} to
27408 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
27409 is not a tracepoint, error is emitted. This corresponds to CLI
27410 command @samp{passcount}.
27412 @subheading The @code{-break-watch} Command
27413 @findex -break-watch
27415 @subsubheading Synopsis
27418 -break-watch [ -a | -r ]
27421 Create a watchpoint. With the @samp{-a} option it will create an
27422 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
27423 read from or on a write to the memory location. With the @samp{-r}
27424 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
27425 trigger only when the memory location is accessed for reading. Without
27426 either of the options, the watchpoint created is a regular watchpoint,
27427 i.e., it will trigger when the memory location is accessed for writing.
27428 @xref{Set Watchpoints, , Setting Watchpoints}.
27430 Note that @samp{-break-list} will report a single list of watchpoints and
27431 breakpoints inserted.
27433 @subsubheading @value{GDBN} Command
27435 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
27438 @subsubheading Example
27440 Setting a watchpoint on a variable in the @code{main} function:
27445 ^done,wpt=@{number="2",exp="x"@}
27450 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
27451 value=@{old="-268439212",new="55"@},
27452 frame=@{func="main",args=[],file="recursive2.c",
27453 fullname="/home/foo/bar/recursive2.c",line="5"@}
27457 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
27458 the program execution twice: first for the variable changing value, then
27459 for the watchpoint going out of scope.
27464 ^done,wpt=@{number="5",exp="C"@}
27469 *stopped,reason="watchpoint-trigger",
27470 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
27471 frame=@{func="callee4",args=[],
27472 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27473 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27478 *stopped,reason="watchpoint-scope",wpnum="5",
27479 frame=@{func="callee3",args=[@{name="strarg",
27480 value="0x11940 \"A string argument.\""@}],
27481 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27482 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27486 Listing breakpoints and watchpoints, at different points in the program
27487 execution. Note that once the watchpoint goes out of scope, it is
27493 ^done,wpt=@{number="2",exp="C"@}
27496 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27497 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27498 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27499 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27500 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27501 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27502 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27503 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27504 addr="0x00010734",func="callee4",
27505 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27506 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
27508 bkpt=@{number="2",type="watchpoint",disp="keep",
27509 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
27514 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
27515 value=@{old="-276895068",new="3"@},
27516 frame=@{func="callee4",args=[],
27517 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27518 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27521 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27522 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27523 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27524 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27525 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27526 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27527 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27528 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27529 addr="0x00010734",func="callee4",
27530 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27531 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
27533 bkpt=@{number="2",type="watchpoint",disp="keep",
27534 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
27538 ^done,reason="watchpoint-scope",wpnum="2",
27539 frame=@{func="callee3",args=[@{name="strarg",
27540 value="0x11940 \"A string argument.\""@}],
27541 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27542 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27545 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27546 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27547 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27548 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27549 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27550 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27551 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27552 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27553 addr="0x00010734",func="callee4",
27554 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27555 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
27556 thread-groups=["i1"],times="1"@}]@}
27561 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27562 @node GDB/MI Catchpoint Commands
27563 @section @sc{gdb/mi} Catchpoint Commands
27565 This section documents @sc{gdb/mi} commands for manipulating
27569 * Shared Library GDB/MI Catchpoint Commands::
27570 * Ada Exception GDB/MI Catchpoint Commands::
27573 @node Shared Library GDB/MI Catchpoint Commands
27574 @subsection Shared Library @sc{gdb/mi} Catchpoints
27576 @subheading The @code{-catch-load} Command
27577 @findex -catch-load
27579 @subsubheading Synopsis
27582 -catch-load [ -t ] [ -d ] @var{regexp}
27585 Add a catchpoint for library load events. If the @samp{-t} option is used,
27586 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
27587 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
27588 in a disabled state. The @samp{regexp} argument is a regular
27589 expression used to match the name of the loaded library.
27592 @subsubheading @value{GDBN} Command
27594 The corresponding @value{GDBN} command is @samp{catch load}.
27596 @subsubheading Example
27599 -catch-load -t foo.so
27600 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
27601 what="load of library matching foo.so",catch-type="load",times="0"@}
27606 @subheading The @code{-catch-unload} Command
27607 @findex -catch-unload
27609 @subsubheading Synopsis
27612 -catch-unload [ -t ] [ -d ] @var{regexp}
27615 Add a catchpoint for library unload events. If the @samp{-t} option is
27616 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
27617 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
27618 created in a disabled state. The @samp{regexp} argument is a regular
27619 expression used to match the name of the unloaded library.
27621 @subsubheading @value{GDBN} Command
27623 The corresponding @value{GDBN} command is @samp{catch unload}.
27625 @subsubheading Example
27628 -catch-unload -d bar.so
27629 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
27630 what="load of library matching bar.so",catch-type="unload",times="0"@}
27634 @node Ada Exception GDB/MI Catchpoint Commands
27635 @subsection Ada Exception @sc{gdb/mi} Catchpoints
27637 The following @sc{gdb/mi} commands can be used to create catchpoints
27638 that stop the execution when Ada exceptions are being raised.
27640 @subheading The @code{-catch-assert} Command
27641 @findex -catch-assert
27643 @subsubheading Synopsis
27646 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
27649 Add a catchpoint for failed Ada assertions.
27651 The possible optional parameters for this command are:
27654 @item -c @var{condition}
27655 Make the catchpoint conditional on @var{condition}.
27657 Create a disabled catchpoint.
27659 Create a temporary catchpoint.
27662 @subsubheading @value{GDBN} Command
27664 The corresponding @value{GDBN} command is @samp{catch assert}.
27666 @subsubheading Example
27670 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
27671 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
27672 thread-groups=["i1"],times="0",
27673 original-location="__gnat_debug_raise_assert_failure"@}
27677 @subheading The @code{-catch-exception} Command
27678 @findex -catch-exception
27680 @subsubheading Synopsis
27683 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
27687 Add a catchpoint stopping when Ada exceptions are raised.
27688 By default, the command stops the program when any Ada exception
27689 gets raised. But it is also possible, by using some of the
27690 optional parameters described below, to create more selective
27693 The possible optional parameters for this command are:
27696 @item -c @var{condition}
27697 Make the catchpoint conditional on @var{condition}.
27699 Create a disabled catchpoint.
27700 @item -e @var{exception-name}
27701 Only stop when @var{exception-name} is raised. This option cannot
27702 be used combined with @samp{-u}.
27704 Create a temporary catchpoint.
27706 Stop only when an unhandled exception gets raised. This option
27707 cannot be used combined with @samp{-e}.
27710 @subsubheading @value{GDBN} Command
27712 The corresponding @value{GDBN} commands are @samp{catch exception}
27713 and @samp{catch exception unhandled}.
27715 @subsubheading Example
27718 -catch-exception -e Program_Error
27719 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
27720 enabled="y",addr="0x0000000000404874",
27721 what="`Program_Error' Ada exception", thread-groups=["i1"],
27722 times="0",original-location="__gnat_debug_raise_exception"@}
27726 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27727 @node GDB/MI Program Context
27728 @section @sc{gdb/mi} Program Context
27730 @subheading The @code{-exec-arguments} Command
27731 @findex -exec-arguments
27734 @subsubheading Synopsis
27737 -exec-arguments @var{args}
27740 Set the inferior program arguments, to be used in the next
27743 @subsubheading @value{GDBN} Command
27745 The corresponding @value{GDBN} command is @samp{set args}.
27747 @subsubheading Example
27751 -exec-arguments -v word
27758 @subheading The @code{-exec-show-arguments} Command
27759 @findex -exec-show-arguments
27761 @subsubheading Synopsis
27764 -exec-show-arguments
27767 Print the arguments of the program.
27769 @subsubheading @value{GDBN} Command
27771 The corresponding @value{GDBN} command is @samp{show args}.
27773 @subsubheading Example
27778 @subheading The @code{-environment-cd} Command
27779 @findex -environment-cd
27781 @subsubheading Synopsis
27784 -environment-cd @var{pathdir}
27787 Set @value{GDBN}'s working directory.
27789 @subsubheading @value{GDBN} Command
27791 The corresponding @value{GDBN} command is @samp{cd}.
27793 @subsubheading Example
27797 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27803 @subheading The @code{-environment-directory} Command
27804 @findex -environment-directory
27806 @subsubheading Synopsis
27809 -environment-directory [ -r ] [ @var{pathdir} ]+
27812 Add directories @var{pathdir} to beginning of search path for source files.
27813 If the @samp{-r} option is used, the search path is reset to the default
27814 search path. If directories @var{pathdir} are supplied in addition to the
27815 @samp{-r} option, the search path is first reset and then addition
27817 Multiple directories may be specified, separated by blanks. Specifying
27818 multiple directories in a single command
27819 results in the directories added to the beginning of the
27820 search path in the same order they were presented in the command.
27821 If blanks are needed as
27822 part of a directory name, double-quotes should be used around
27823 the name. In the command output, the path will show up separated
27824 by the system directory-separator character. The directory-separator
27825 character must not be used
27826 in any directory name.
27827 If no directories are specified, the current search path is displayed.
27829 @subsubheading @value{GDBN} Command
27831 The corresponding @value{GDBN} command is @samp{dir}.
27833 @subsubheading Example
27837 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27838 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27840 -environment-directory ""
27841 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27843 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
27844 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
27846 -environment-directory -r
27847 ^done,source-path="$cdir:$cwd"
27852 @subheading The @code{-environment-path} Command
27853 @findex -environment-path
27855 @subsubheading Synopsis
27858 -environment-path [ -r ] [ @var{pathdir} ]+
27861 Add directories @var{pathdir} to beginning of search path for object files.
27862 If the @samp{-r} option is used, the search path is reset to the original
27863 search path that existed at gdb start-up. If directories @var{pathdir} are
27864 supplied in addition to the
27865 @samp{-r} option, the search path is first reset and then addition
27867 Multiple directories may be specified, separated by blanks. Specifying
27868 multiple directories in a single command
27869 results in the directories added to the beginning of the
27870 search path in the same order they were presented in the command.
27871 If blanks are needed as
27872 part of a directory name, double-quotes should be used around
27873 the name. In the command output, the path will show up separated
27874 by the system directory-separator character. The directory-separator
27875 character must not be used
27876 in any directory name.
27877 If no directories are specified, the current path is displayed.
27880 @subsubheading @value{GDBN} Command
27882 The corresponding @value{GDBN} command is @samp{path}.
27884 @subsubheading Example
27889 ^done,path="/usr/bin"
27891 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
27892 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
27894 -environment-path -r /usr/local/bin
27895 ^done,path="/usr/local/bin:/usr/bin"
27900 @subheading The @code{-environment-pwd} Command
27901 @findex -environment-pwd
27903 @subsubheading Synopsis
27909 Show the current working directory.
27911 @subsubheading @value{GDBN} Command
27913 The corresponding @value{GDBN} command is @samp{pwd}.
27915 @subsubheading Example
27920 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
27924 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27925 @node GDB/MI Thread Commands
27926 @section @sc{gdb/mi} Thread Commands
27929 @subheading The @code{-thread-info} Command
27930 @findex -thread-info
27932 @subsubheading Synopsis
27935 -thread-info [ @var{thread-id} ]
27938 Reports information about either a specific thread, if the
27939 @var{thread-id} parameter is present, or about all threads.
27940 @var{thread-id} is the thread's global thread ID. When printing
27941 information about all threads, also reports the global ID of the
27944 @subsubheading @value{GDBN} Command
27946 The @samp{info thread} command prints the same information
27949 @subsubheading Result
27951 The result is a list of threads. The following attributes are
27952 defined for a given thread:
27956 This field exists only for the current thread. It has the value @samp{*}.
27959 The global identifier that @value{GDBN} uses to refer to the thread.
27962 The identifier that the target uses to refer to the thread.
27965 Extra information about the thread, in a target-specific format. This
27969 The name of the thread. If the user specified a name using the
27970 @code{thread name} command, then this name is given. Otherwise, if
27971 @value{GDBN} can extract the thread name from the target, then that
27972 name is given. If @value{GDBN} cannot find the thread name, then this
27976 The stack frame currently executing in the thread.
27979 The thread's state. The @samp{state} field may have the following
27984 The thread is stopped. Frame information is available for stopped
27988 The thread is running. There's no frame information for running
27994 If @value{GDBN} can find the CPU core on which this thread is running,
27995 then this field is the core identifier. This field is optional.
27999 @subsubheading Example
28004 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
28005 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
28006 args=[]@},state="running"@},
28007 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
28008 frame=@{level="0",addr="0x0804891f",func="foo",
28009 args=[@{name="i",value="10"@}],
28010 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
28011 state="running"@}],
28012 current-thread-id="1"
28016 @subheading The @code{-thread-list-ids} Command
28017 @findex -thread-list-ids
28019 @subsubheading Synopsis
28025 Produces a list of the currently known global @value{GDBN} thread ids.
28026 At the end of the list it also prints the total number of such
28029 This command is retained for historical reasons, the
28030 @code{-thread-info} command should be used instead.
28032 @subsubheading @value{GDBN} Command
28034 Part of @samp{info threads} supplies the same information.
28036 @subsubheading Example
28041 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
28042 current-thread-id="1",number-of-threads="3"
28047 @subheading The @code{-thread-select} Command
28048 @findex -thread-select
28050 @subsubheading Synopsis
28053 -thread-select @var{thread-id}
28056 Make thread with global thread number @var{thread-id} the current
28057 thread. It prints the number of the new current thread, and the
28058 topmost frame for that thread.
28060 This command is deprecated in favor of explicitly using the
28061 @samp{--thread} option to each command.
28063 @subsubheading @value{GDBN} Command
28065 The corresponding @value{GDBN} command is @samp{thread}.
28067 @subsubheading Example
28074 *stopped,reason="end-stepping-range",thread-id="2",line="187",
28075 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
28079 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
28080 number-of-threads="3"
28083 ^done,new-thread-id="3",
28084 frame=@{level="0",func="vprintf",
28085 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
28086 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
28090 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28091 @node GDB/MI Ada Tasking Commands
28092 @section @sc{gdb/mi} Ada Tasking Commands
28094 @subheading The @code{-ada-task-info} Command
28095 @findex -ada-task-info
28097 @subsubheading Synopsis
28100 -ada-task-info [ @var{task-id} ]
28103 Reports information about either a specific Ada task, if the
28104 @var{task-id} parameter is present, or about all Ada tasks.
28106 @subsubheading @value{GDBN} Command
28108 The @samp{info tasks} command prints the same information
28109 about all Ada tasks (@pxref{Ada Tasks}).
28111 @subsubheading Result
28113 The result is a table of Ada tasks. The following columns are
28114 defined for each Ada task:
28118 This field exists only for the current thread. It has the value @samp{*}.
28121 The identifier that @value{GDBN} uses to refer to the Ada task.
28124 The identifier that the target uses to refer to the Ada task.
28127 The global thread identifier of the thread corresponding to the Ada
28130 This field should always exist, as Ada tasks are always implemented
28131 on top of a thread. But if @value{GDBN} cannot find this corresponding
28132 thread for any reason, the field is omitted.
28135 This field exists only when the task was created by another task.
28136 In this case, it provides the ID of the parent task.
28139 The base priority of the task.
28142 The current state of the task. For a detailed description of the
28143 possible states, see @ref{Ada Tasks}.
28146 The name of the task.
28150 @subsubheading Example
28154 ^done,tasks=@{nr_rows="3",nr_cols="8",
28155 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
28156 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
28157 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
28158 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
28159 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
28160 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
28161 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
28162 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
28163 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
28164 state="Child Termination Wait",name="main_task"@}]@}
28168 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28169 @node GDB/MI Program Execution
28170 @section @sc{gdb/mi} Program Execution
28172 These are the asynchronous commands which generate the out-of-band
28173 record @samp{*stopped}. Currently @value{GDBN} only really executes
28174 asynchronously with remote targets and this interaction is mimicked in
28177 @subheading The @code{-exec-continue} Command
28178 @findex -exec-continue
28180 @subsubheading Synopsis
28183 -exec-continue [--reverse] [--all|--thread-group N]
28186 Resumes the execution of the inferior program, which will continue
28187 to execute until it reaches a debugger stop event. If the
28188 @samp{--reverse} option is specified, execution resumes in reverse until
28189 it reaches a stop event. Stop events may include
28192 breakpoints or watchpoints
28194 signals or exceptions
28196 the end of the process (or its beginning under @samp{--reverse})
28198 the end or beginning of a replay log if one is being used.
28200 In all-stop mode (@pxref{All-Stop
28201 Mode}), may resume only one thread, or all threads, depending on the
28202 value of the @samp{scheduler-locking} variable. If @samp{--all} is
28203 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
28204 ignored in all-stop mode. If the @samp{--thread-group} options is
28205 specified, then all threads in that thread group are resumed.
28207 @subsubheading @value{GDBN} Command
28209 The corresponding @value{GDBN} corresponding is @samp{continue}.
28211 @subsubheading Example
28218 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
28219 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
28225 @subheading The @code{-exec-finish} Command
28226 @findex -exec-finish
28228 @subsubheading Synopsis
28231 -exec-finish [--reverse]
28234 Resumes the execution of the inferior program until the current
28235 function is exited. Displays the results returned by the function.
28236 If the @samp{--reverse} option is specified, resumes the reverse
28237 execution of the inferior program until the point where current
28238 function was called.
28240 @subsubheading @value{GDBN} Command
28242 The corresponding @value{GDBN} command is @samp{finish}.
28244 @subsubheading Example
28246 Function returning @code{void}.
28253 *stopped,reason="function-finished",frame=@{func="main",args=[],
28254 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
28258 Function returning other than @code{void}. The name of the internal
28259 @value{GDBN} variable storing the result is printed, together with the
28266 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
28267 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
28268 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28269 gdb-result-var="$1",return-value="0"
28274 @subheading The @code{-exec-interrupt} Command
28275 @findex -exec-interrupt
28277 @subsubheading Synopsis
28280 -exec-interrupt [--all|--thread-group N]
28283 Interrupts the background execution of the target. Note how the token
28284 associated with the stop message is the one for the execution command
28285 that has been interrupted. The token for the interrupt itself only
28286 appears in the @samp{^done} output. If the user is trying to
28287 interrupt a non-running program, an error message will be printed.
28289 Note that when asynchronous execution is enabled, this command is
28290 asynchronous just like other execution commands. That is, first the
28291 @samp{^done} response will be printed, and the target stop will be
28292 reported after that using the @samp{*stopped} notification.
28294 In non-stop mode, only the context thread is interrupted by default.
28295 All threads (in all inferiors) will be interrupted if the
28296 @samp{--all} option is specified. If the @samp{--thread-group}
28297 option is specified, all threads in that group will be interrupted.
28299 @subsubheading @value{GDBN} Command
28301 The corresponding @value{GDBN} command is @samp{interrupt}.
28303 @subsubheading Example
28314 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
28315 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
28316 fullname="/home/foo/bar/try.c",line="13"@}
28321 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
28325 @subheading The @code{-exec-jump} Command
28328 @subsubheading Synopsis
28331 -exec-jump @var{location}
28334 Resumes execution of the inferior program at the location specified by
28335 parameter. @xref{Specify Location}, for a description of the
28336 different forms of @var{location}.
28338 @subsubheading @value{GDBN} Command
28340 The corresponding @value{GDBN} command is @samp{jump}.
28342 @subsubheading Example
28345 -exec-jump foo.c:10
28346 *running,thread-id="all"
28351 @subheading The @code{-exec-next} Command
28354 @subsubheading Synopsis
28357 -exec-next [--reverse]
28360 Resumes execution of the inferior program, stopping when the beginning
28361 of the next source line is reached.
28363 If the @samp{--reverse} option is specified, resumes reverse execution
28364 of the inferior program, stopping at the beginning of the previous
28365 source line. If you issue this command on the first line of a
28366 function, it will take you back to the caller of that function, to the
28367 source line where the function was called.
28370 @subsubheading @value{GDBN} Command
28372 The corresponding @value{GDBN} command is @samp{next}.
28374 @subsubheading Example
28380 *stopped,reason="end-stepping-range",line="8",file="hello.c"
28385 @subheading The @code{-exec-next-instruction} Command
28386 @findex -exec-next-instruction
28388 @subsubheading Synopsis
28391 -exec-next-instruction [--reverse]
28394 Executes one machine instruction. If the instruction is a function
28395 call, continues until the function returns. If the program stops at an
28396 instruction in the middle of a source line, the address will be
28399 If the @samp{--reverse} option is specified, resumes reverse execution
28400 of the inferior program, stopping at the previous instruction. If the
28401 previously executed instruction was a return from another function,
28402 it will continue to execute in reverse until the call to that function
28403 (from the current stack frame) is reached.
28405 @subsubheading @value{GDBN} Command
28407 The corresponding @value{GDBN} command is @samp{nexti}.
28409 @subsubheading Example
28413 -exec-next-instruction
28417 *stopped,reason="end-stepping-range",
28418 addr="0x000100d4",line="5",file="hello.c"
28423 @subheading The @code{-exec-return} Command
28424 @findex -exec-return
28426 @subsubheading Synopsis
28432 Makes current function return immediately. Doesn't execute the inferior.
28433 Displays the new current frame.
28435 @subsubheading @value{GDBN} Command
28437 The corresponding @value{GDBN} command is @samp{return}.
28439 @subsubheading Example
28443 200-break-insert callee4
28444 200^done,bkpt=@{number="1",addr="0x00010734",
28445 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28450 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28451 frame=@{func="callee4",args=[],
28452 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28453 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28459 111^done,frame=@{level="0",func="callee3",
28460 args=[@{name="strarg",
28461 value="0x11940 \"A string argument.\""@}],
28462 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28463 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28468 @subheading The @code{-exec-run} Command
28471 @subsubheading Synopsis
28474 -exec-run [ --all | --thread-group N ] [ --start ]
28477 Starts execution of the inferior from the beginning. The inferior
28478 executes until either a breakpoint is encountered or the program
28479 exits. In the latter case the output will include an exit code, if
28480 the program has exited exceptionally.
28482 When neither the @samp{--all} nor the @samp{--thread-group} option
28483 is specified, the current inferior is started. If the
28484 @samp{--thread-group} option is specified, it should refer to a thread
28485 group of type @samp{process}, and that thread group will be started.
28486 If the @samp{--all} option is specified, then all inferiors will be started.
28488 Using the @samp{--start} option instructs the debugger to stop
28489 the execution at the start of the inferior's main subprogram,
28490 following the same behavior as the @code{start} command
28491 (@pxref{Starting}).
28493 @subsubheading @value{GDBN} Command
28495 The corresponding @value{GDBN} command is @samp{run}.
28497 @subsubheading Examples
28502 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
28507 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28508 frame=@{func="main",args=[],file="recursive2.c",
28509 fullname="/home/foo/bar/recursive2.c",line="4"@}
28514 Program exited normally:
28522 *stopped,reason="exited-normally"
28527 Program exited exceptionally:
28535 *stopped,reason="exited",exit-code="01"
28539 Another way the program can terminate is if it receives a signal such as
28540 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
28544 *stopped,reason="exited-signalled",signal-name="SIGINT",
28545 signal-meaning="Interrupt"
28549 @c @subheading -exec-signal
28552 @subheading The @code{-exec-step} Command
28555 @subsubheading Synopsis
28558 -exec-step [--reverse]
28561 Resumes execution of the inferior program, stopping when the beginning
28562 of the next source line is reached, if the next source line is not a
28563 function call. If it is, stop at the first instruction of the called
28564 function. If the @samp{--reverse} option is specified, resumes reverse
28565 execution of the inferior program, stopping at the beginning of the
28566 previously executed source line.
28568 @subsubheading @value{GDBN} Command
28570 The corresponding @value{GDBN} command is @samp{step}.
28572 @subsubheading Example
28574 Stepping into a function:
28580 *stopped,reason="end-stepping-range",
28581 frame=@{func="foo",args=[@{name="a",value="10"@},
28582 @{name="b",value="0"@}],file="recursive2.c",
28583 fullname="/home/foo/bar/recursive2.c",line="11"@}
28593 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
28598 @subheading The @code{-exec-step-instruction} Command
28599 @findex -exec-step-instruction
28601 @subsubheading Synopsis
28604 -exec-step-instruction [--reverse]
28607 Resumes the inferior which executes one machine instruction. If the
28608 @samp{--reverse} option is specified, resumes reverse execution of the
28609 inferior program, stopping at the previously executed instruction.
28610 The output, once @value{GDBN} has stopped, will vary depending on
28611 whether we have stopped in the middle of a source line or not. In the
28612 former case, the address at which the program stopped will be printed
28615 @subsubheading @value{GDBN} Command
28617 The corresponding @value{GDBN} command is @samp{stepi}.
28619 @subsubheading Example
28623 -exec-step-instruction
28627 *stopped,reason="end-stepping-range",
28628 frame=@{func="foo",args=[],file="try.c",
28629 fullname="/home/foo/bar/try.c",line="10"@}
28631 -exec-step-instruction
28635 *stopped,reason="end-stepping-range",
28636 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
28637 fullname="/home/foo/bar/try.c",line="10"@}
28642 @subheading The @code{-exec-until} Command
28643 @findex -exec-until
28645 @subsubheading Synopsis
28648 -exec-until [ @var{location} ]
28651 Executes the inferior until the @var{location} specified in the
28652 argument is reached. If there is no argument, the inferior executes
28653 until a source line greater than the current one is reached. The
28654 reason for stopping in this case will be @samp{location-reached}.
28656 @subsubheading @value{GDBN} Command
28658 The corresponding @value{GDBN} command is @samp{until}.
28660 @subsubheading Example
28664 -exec-until recursive2.c:6
28668 *stopped,reason="location-reached",frame=@{func="main",args=[],
28669 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
28674 @subheading -file-clear
28675 Is this going away????
28678 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28679 @node GDB/MI Stack Manipulation
28680 @section @sc{gdb/mi} Stack Manipulation Commands
28682 @subheading The @code{-enable-frame-filters} Command
28683 @findex -enable-frame-filters
28686 -enable-frame-filters
28689 @value{GDBN} allows Python-based frame filters to affect the output of
28690 the MI commands relating to stack traces. As there is no way to
28691 implement this in a fully backward-compatible way, a front end must
28692 request that this functionality be enabled.
28694 Once enabled, this feature cannot be disabled.
28696 Note that if Python support has not been compiled into @value{GDBN},
28697 this command will still succeed (and do nothing).
28699 @subheading The @code{-stack-info-frame} Command
28700 @findex -stack-info-frame
28702 @subsubheading Synopsis
28708 Get info on the selected frame.
28710 @subsubheading @value{GDBN} Command
28712 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
28713 (without arguments).
28715 @subsubheading Example
28720 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
28721 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28722 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
28726 @subheading The @code{-stack-info-depth} Command
28727 @findex -stack-info-depth
28729 @subsubheading Synopsis
28732 -stack-info-depth [ @var{max-depth} ]
28735 Return the depth of the stack. If the integer argument @var{max-depth}
28736 is specified, do not count beyond @var{max-depth} frames.
28738 @subsubheading @value{GDBN} Command
28740 There's no equivalent @value{GDBN} command.
28742 @subsubheading Example
28744 For a stack with frame levels 0 through 11:
28751 -stack-info-depth 4
28754 -stack-info-depth 12
28757 -stack-info-depth 11
28760 -stack-info-depth 13
28765 @anchor{-stack-list-arguments}
28766 @subheading The @code{-stack-list-arguments} Command
28767 @findex -stack-list-arguments
28769 @subsubheading Synopsis
28772 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28773 [ @var{low-frame} @var{high-frame} ]
28776 Display a list of the arguments for the frames between @var{low-frame}
28777 and @var{high-frame} (inclusive). If @var{low-frame} and
28778 @var{high-frame} are not provided, list the arguments for the whole
28779 call stack. If the two arguments are equal, show the single frame
28780 at the corresponding level. It is an error if @var{low-frame} is
28781 larger than the actual number of frames. On the other hand,
28782 @var{high-frame} may be larger than the actual number of frames, in
28783 which case only existing frames will be returned.
28785 If @var{print-values} is 0 or @code{--no-values}, print only the names of
28786 the variables; if it is 1 or @code{--all-values}, print also their
28787 values; and if it is 2 or @code{--simple-values}, print the name,
28788 type and value for simple data types, and the name and type for arrays,
28789 structures and unions. If the option @code{--no-frame-filters} is
28790 supplied, then Python frame filters will not be executed.
28792 If the @code{--skip-unavailable} option is specified, arguments that
28793 are not available are not listed. Partially available arguments
28794 are still displayed, however.
28796 Use of this command to obtain arguments in a single frame is
28797 deprecated in favor of the @samp{-stack-list-variables} command.
28799 @subsubheading @value{GDBN} Command
28801 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
28802 @samp{gdb_get_args} command which partially overlaps with the
28803 functionality of @samp{-stack-list-arguments}.
28805 @subsubheading Example
28812 frame=@{level="0",addr="0x00010734",func="callee4",
28813 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28814 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
28815 frame=@{level="1",addr="0x0001076c",func="callee3",
28816 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28817 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
28818 frame=@{level="2",addr="0x0001078c",func="callee2",
28819 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28820 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
28821 frame=@{level="3",addr="0x000107b4",func="callee1",
28822 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28823 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
28824 frame=@{level="4",addr="0x000107e0",func="main",
28825 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28826 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
28828 -stack-list-arguments 0
28831 frame=@{level="0",args=[]@},
28832 frame=@{level="1",args=[name="strarg"]@},
28833 frame=@{level="2",args=[name="intarg",name="strarg"]@},
28834 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
28835 frame=@{level="4",args=[]@}]
28837 -stack-list-arguments 1
28840 frame=@{level="0",args=[]@},
28842 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28843 frame=@{level="2",args=[
28844 @{name="intarg",value="2"@},
28845 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28846 @{frame=@{level="3",args=[
28847 @{name="intarg",value="2"@},
28848 @{name="strarg",value="0x11940 \"A string argument.\""@},
28849 @{name="fltarg",value="3.5"@}]@},
28850 frame=@{level="4",args=[]@}]
28852 -stack-list-arguments 0 2 2
28853 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
28855 -stack-list-arguments 1 2 2
28856 ^done,stack-args=[frame=@{level="2",
28857 args=[@{name="intarg",value="2"@},
28858 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
28862 @c @subheading -stack-list-exception-handlers
28865 @anchor{-stack-list-frames}
28866 @subheading The @code{-stack-list-frames} Command
28867 @findex -stack-list-frames
28869 @subsubheading Synopsis
28872 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
28875 List the frames currently on the stack. For each frame it displays the
28880 The frame number, 0 being the topmost frame, i.e., the innermost function.
28882 The @code{$pc} value for that frame.
28886 File name of the source file where the function lives.
28887 @item @var{fullname}
28888 The full file name of the source file where the function lives.
28890 Line number corresponding to the @code{$pc}.
28892 The shared library where this function is defined. This is only given
28893 if the frame's function is not known.
28896 If invoked without arguments, this command prints a backtrace for the
28897 whole stack. If given two integer arguments, it shows the frames whose
28898 levels are between the two arguments (inclusive). If the two arguments
28899 are equal, it shows the single frame at the corresponding level. It is
28900 an error if @var{low-frame} is larger than the actual number of
28901 frames. On the other hand, @var{high-frame} may be larger than the
28902 actual number of frames, in which case only existing frames will be
28903 returned. If the option @code{--no-frame-filters} is supplied, then
28904 Python frame filters will not be executed.
28906 @subsubheading @value{GDBN} Command
28908 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
28910 @subsubheading Example
28912 Full stack backtrace:
28918 [frame=@{level="0",addr="0x0001076c",func="foo",
28919 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
28920 frame=@{level="1",addr="0x000107a4",func="foo",
28921 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28922 frame=@{level="2",addr="0x000107a4",func="foo",
28923 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28924 frame=@{level="3",addr="0x000107a4",func="foo",
28925 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28926 frame=@{level="4",addr="0x000107a4",func="foo",
28927 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28928 frame=@{level="5",addr="0x000107a4",func="foo",
28929 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28930 frame=@{level="6",addr="0x000107a4",func="foo",
28931 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28932 frame=@{level="7",addr="0x000107a4",func="foo",
28933 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28934 frame=@{level="8",addr="0x000107a4",func="foo",
28935 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28936 frame=@{level="9",addr="0x000107a4",func="foo",
28937 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28938 frame=@{level="10",addr="0x000107a4",func="foo",
28939 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28940 frame=@{level="11",addr="0x00010738",func="main",
28941 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
28945 Show frames between @var{low_frame} and @var{high_frame}:
28949 -stack-list-frames 3 5
28951 [frame=@{level="3",addr="0x000107a4",func="foo",
28952 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28953 frame=@{level="4",addr="0x000107a4",func="foo",
28954 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28955 frame=@{level="5",addr="0x000107a4",func="foo",
28956 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28960 Show a single frame:
28964 -stack-list-frames 3 3
28966 [frame=@{level="3",addr="0x000107a4",func="foo",
28967 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28972 @subheading The @code{-stack-list-locals} Command
28973 @findex -stack-list-locals
28974 @anchor{-stack-list-locals}
28976 @subsubheading Synopsis
28979 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28982 Display the local variable names for the selected frame. If
28983 @var{print-values} is 0 or @code{--no-values}, print only the names of
28984 the variables; if it is 1 or @code{--all-values}, print also their
28985 values; and if it is 2 or @code{--simple-values}, print the name,
28986 type and value for simple data types, and the name and type for arrays,
28987 structures and unions. In this last case, a frontend can immediately
28988 display the value of simple data types and create variable objects for
28989 other data types when the user wishes to explore their values in
28990 more detail. If the option @code{--no-frame-filters} is supplied, then
28991 Python frame filters will not be executed.
28993 If the @code{--skip-unavailable} option is specified, local variables
28994 that are not available are not listed. Partially available local
28995 variables are still displayed, however.
28997 This command is deprecated in favor of the
28998 @samp{-stack-list-variables} command.
29000 @subsubheading @value{GDBN} Command
29002 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
29004 @subsubheading Example
29008 -stack-list-locals 0
29009 ^done,locals=[name="A",name="B",name="C"]
29011 -stack-list-locals --all-values
29012 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
29013 @{name="C",value="@{1, 2, 3@}"@}]
29014 -stack-list-locals --simple-values
29015 ^done,locals=[@{name="A",type="int",value="1"@},
29016 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
29020 @anchor{-stack-list-variables}
29021 @subheading The @code{-stack-list-variables} Command
29022 @findex -stack-list-variables
29024 @subsubheading Synopsis
29027 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
29030 Display the names of local variables and function arguments for the selected frame. If
29031 @var{print-values} is 0 or @code{--no-values}, print only the names of
29032 the variables; if it is 1 or @code{--all-values}, print also their
29033 values; and if it is 2 or @code{--simple-values}, print the name,
29034 type and value for simple data types, and the name and type for arrays,
29035 structures and unions. If the option @code{--no-frame-filters} is
29036 supplied, then Python frame filters will not be executed.
29038 If the @code{--skip-unavailable} option is specified, local variables
29039 and arguments that are not available are not listed. Partially
29040 available arguments and local variables are still displayed, however.
29042 @subsubheading Example
29046 -stack-list-variables --thread 1 --frame 0 --all-values
29047 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
29052 @subheading The @code{-stack-select-frame} Command
29053 @findex -stack-select-frame
29055 @subsubheading Synopsis
29058 -stack-select-frame @var{framenum}
29061 Change the selected frame. Select a different frame @var{framenum} on
29064 This command in deprecated in favor of passing the @samp{--frame}
29065 option to every command.
29067 @subsubheading @value{GDBN} Command
29069 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
29070 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
29072 @subsubheading Example
29076 -stack-select-frame 2
29081 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29082 @node GDB/MI Variable Objects
29083 @section @sc{gdb/mi} Variable Objects
29087 @subheading Motivation for Variable Objects in @sc{gdb/mi}
29089 For the implementation of a variable debugger window (locals, watched
29090 expressions, etc.), we are proposing the adaptation of the existing code
29091 used by @code{Insight}.
29093 The two main reasons for that are:
29097 It has been proven in practice (it is already on its second generation).
29100 It will shorten development time (needless to say how important it is
29104 The original interface was designed to be used by Tcl code, so it was
29105 slightly changed so it could be used through @sc{gdb/mi}. This section
29106 describes the @sc{gdb/mi} operations that will be available and gives some
29107 hints about their use.
29109 @emph{Note}: In addition to the set of operations described here, we
29110 expect the @sc{gui} implementation of a variable window to require, at
29111 least, the following operations:
29114 @item @code{-gdb-show} @code{output-radix}
29115 @item @code{-stack-list-arguments}
29116 @item @code{-stack-list-locals}
29117 @item @code{-stack-select-frame}
29122 @subheading Introduction to Variable Objects
29124 @cindex variable objects in @sc{gdb/mi}
29126 Variable objects are "object-oriented" MI interface for examining and
29127 changing values of expressions. Unlike some other MI interfaces that
29128 work with expressions, variable objects are specifically designed for
29129 simple and efficient presentation in the frontend. A variable object
29130 is identified by string name. When a variable object is created, the
29131 frontend specifies the expression for that variable object. The
29132 expression can be a simple variable, or it can be an arbitrary complex
29133 expression, and can even involve CPU registers. After creating a
29134 variable object, the frontend can invoke other variable object
29135 operations---for example to obtain or change the value of a variable
29136 object, or to change display format.
29138 Variable objects have hierarchical tree structure. Any variable object
29139 that corresponds to a composite type, such as structure in C, has
29140 a number of child variable objects, for example corresponding to each
29141 element of a structure. A child variable object can itself have
29142 children, recursively. Recursion ends when we reach
29143 leaf variable objects, which always have built-in types. Child variable
29144 objects are created only by explicit request, so if a frontend
29145 is not interested in the children of a particular variable object, no
29146 child will be created.
29148 For a leaf variable object it is possible to obtain its value as a
29149 string, or set the value from a string. String value can be also
29150 obtained for a non-leaf variable object, but it's generally a string
29151 that only indicates the type of the object, and does not list its
29152 contents. Assignment to a non-leaf variable object is not allowed.
29154 A frontend does not need to read the values of all variable objects each time
29155 the program stops. Instead, MI provides an update command that lists all
29156 variable objects whose values has changed since the last update
29157 operation. This considerably reduces the amount of data that must
29158 be transferred to the frontend. As noted above, children variable
29159 objects are created on demand, and only leaf variable objects have a
29160 real value. As result, gdb will read target memory only for leaf
29161 variables that frontend has created.
29163 The automatic update is not always desirable. For example, a frontend
29164 might want to keep a value of some expression for future reference,
29165 and never update it. For another example, fetching memory is
29166 relatively slow for embedded targets, so a frontend might want
29167 to disable automatic update for the variables that are either not
29168 visible on the screen, or ``closed''. This is possible using so
29169 called ``frozen variable objects''. Such variable objects are never
29170 implicitly updated.
29172 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
29173 fixed variable object, the expression is parsed when the variable
29174 object is created, including associating identifiers to specific
29175 variables. The meaning of expression never changes. For a floating
29176 variable object the values of variables whose names appear in the
29177 expressions are re-evaluated every time in the context of the current
29178 frame. Consider this example:
29183 struct work_state state;
29190 If a fixed variable object for the @code{state} variable is created in
29191 this function, and we enter the recursive call, the variable
29192 object will report the value of @code{state} in the top-level
29193 @code{do_work} invocation. On the other hand, a floating variable
29194 object will report the value of @code{state} in the current frame.
29196 If an expression specified when creating a fixed variable object
29197 refers to a local variable, the variable object becomes bound to the
29198 thread and frame in which the variable object is created. When such
29199 variable object is updated, @value{GDBN} makes sure that the
29200 thread/frame combination the variable object is bound to still exists,
29201 and re-evaluates the variable object in context of that thread/frame.
29203 The following is the complete set of @sc{gdb/mi} operations defined to
29204 access this functionality:
29206 @multitable @columnfractions .4 .6
29207 @item @strong{Operation}
29208 @tab @strong{Description}
29210 @item @code{-enable-pretty-printing}
29211 @tab enable Python-based pretty-printing
29212 @item @code{-var-create}
29213 @tab create a variable object
29214 @item @code{-var-delete}
29215 @tab delete the variable object and/or its children
29216 @item @code{-var-set-format}
29217 @tab set the display format of this variable
29218 @item @code{-var-show-format}
29219 @tab show the display format of this variable
29220 @item @code{-var-info-num-children}
29221 @tab tells how many children this object has
29222 @item @code{-var-list-children}
29223 @tab return a list of the object's children
29224 @item @code{-var-info-type}
29225 @tab show the type of this variable object
29226 @item @code{-var-info-expression}
29227 @tab print parent-relative expression that this variable object represents
29228 @item @code{-var-info-path-expression}
29229 @tab print full expression that this variable object represents
29230 @item @code{-var-show-attributes}
29231 @tab is this variable editable? does it exist here?
29232 @item @code{-var-evaluate-expression}
29233 @tab get the value of this variable
29234 @item @code{-var-assign}
29235 @tab set the value of this variable
29236 @item @code{-var-update}
29237 @tab update the variable and its children
29238 @item @code{-var-set-frozen}
29239 @tab set frozeness attribute
29240 @item @code{-var-set-update-range}
29241 @tab set range of children to display on update
29244 In the next subsection we describe each operation in detail and suggest
29245 how it can be used.
29247 @subheading Description And Use of Operations on Variable Objects
29249 @subheading The @code{-enable-pretty-printing} Command
29250 @findex -enable-pretty-printing
29253 -enable-pretty-printing
29256 @value{GDBN} allows Python-based visualizers to affect the output of the
29257 MI variable object commands. However, because there was no way to
29258 implement this in a fully backward-compatible way, a front end must
29259 request that this functionality be enabled.
29261 Once enabled, this feature cannot be disabled.
29263 Note that if Python support has not been compiled into @value{GDBN},
29264 this command will still succeed (and do nothing).
29266 This feature is currently (as of @value{GDBN} 7.0) experimental, and
29267 may work differently in future versions of @value{GDBN}.
29269 @subheading The @code{-var-create} Command
29270 @findex -var-create
29272 @subsubheading Synopsis
29275 -var-create @{@var{name} | "-"@}
29276 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
29279 This operation creates a variable object, which allows the monitoring of
29280 a variable, the result of an expression, a memory cell or a CPU
29283 The @var{name} parameter is the string by which the object can be
29284 referenced. It must be unique. If @samp{-} is specified, the varobj
29285 system will generate a string ``varNNNNNN'' automatically. It will be
29286 unique provided that one does not specify @var{name} of that format.
29287 The command fails if a duplicate name is found.
29289 The frame under which the expression should be evaluated can be
29290 specified by @var{frame-addr}. A @samp{*} indicates that the current
29291 frame should be used. A @samp{@@} indicates that a floating variable
29292 object must be created.
29294 @var{expression} is any expression valid on the current language set (must not
29295 begin with a @samp{*}), or one of the following:
29299 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
29302 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
29305 @samp{$@var{regname}} --- a CPU register name
29308 @cindex dynamic varobj
29309 A varobj's contents may be provided by a Python-based pretty-printer. In this
29310 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
29311 have slightly different semantics in some cases. If the
29312 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
29313 will never create a dynamic varobj. This ensures backward
29314 compatibility for existing clients.
29316 @subsubheading Result
29318 This operation returns attributes of the newly-created varobj. These
29323 The name of the varobj.
29326 The number of children of the varobj. This number is not necessarily
29327 reliable for a dynamic varobj. Instead, you must examine the
29328 @samp{has_more} attribute.
29331 The varobj's scalar value. For a varobj whose type is some sort of
29332 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
29333 will not be interesting.
29336 The varobj's type. This is a string representation of the type, as
29337 would be printed by the @value{GDBN} CLI. If @samp{print object}
29338 (@pxref{Print Settings, set print object}) is set to @code{on}, the
29339 @emph{actual} (derived) type of the object is shown rather than the
29340 @emph{declared} one.
29343 If a variable object is bound to a specific thread, then this is the
29344 thread's global identifier.
29347 For a dynamic varobj, this indicates whether there appear to be any
29348 children available. For a non-dynamic varobj, this will be 0.
29351 This attribute will be present and have the value @samp{1} if the
29352 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29353 then this attribute will not be present.
29356 A dynamic varobj can supply a display hint to the front end. The
29357 value comes directly from the Python pretty-printer object's
29358 @code{display_hint} method. @xref{Pretty Printing API}.
29361 Typical output will look like this:
29364 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
29365 has_more="@var{has_more}"
29369 @subheading The @code{-var-delete} Command
29370 @findex -var-delete
29372 @subsubheading Synopsis
29375 -var-delete [ -c ] @var{name}
29378 Deletes a previously created variable object and all of its children.
29379 With the @samp{-c} option, just deletes the children.
29381 Returns an error if the object @var{name} is not found.
29384 @subheading The @code{-var-set-format} Command
29385 @findex -var-set-format
29387 @subsubheading Synopsis
29390 -var-set-format @var{name} @var{format-spec}
29393 Sets the output format for the value of the object @var{name} to be
29396 @anchor{-var-set-format}
29397 The syntax for the @var{format-spec} is as follows:
29400 @var{format-spec} @expansion{}
29401 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
29404 The natural format is the default format choosen automatically
29405 based on the variable type (like decimal for an @code{int}, hex
29406 for pointers, etc.).
29408 The zero-hexadecimal format has a representation similar to hexadecimal
29409 but with padding zeroes to the left of the value. For example, a 32-bit
29410 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
29411 zero-hexadecimal format.
29413 For a variable with children, the format is set only on the
29414 variable itself, and the children are not affected.
29416 @subheading The @code{-var-show-format} Command
29417 @findex -var-show-format
29419 @subsubheading Synopsis
29422 -var-show-format @var{name}
29425 Returns the format used to display the value of the object @var{name}.
29428 @var{format} @expansion{}
29433 @subheading The @code{-var-info-num-children} Command
29434 @findex -var-info-num-children
29436 @subsubheading Synopsis
29439 -var-info-num-children @var{name}
29442 Returns the number of children of a variable object @var{name}:
29448 Note that this number is not completely reliable for a dynamic varobj.
29449 It will return the current number of children, but more children may
29453 @subheading The @code{-var-list-children} Command
29454 @findex -var-list-children
29456 @subsubheading Synopsis
29459 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
29461 @anchor{-var-list-children}
29463 Return a list of the children of the specified variable object and
29464 create variable objects for them, if they do not already exist. With
29465 a single argument or if @var{print-values} has a value of 0 or
29466 @code{--no-values}, print only the names of the variables; if
29467 @var{print-values} is 1 or @code{--all-values}, also print their
29468 values; and if it is 2 or @code{--simple-values} print the name and
29469 value for simple data types and just the name for arrays, structures
29472 @var{from} and @var{to}, if specified, indicate the range of children
29473 to report. If @var{from} or @var{to} is less than zero, the range is
29474 reset and all children will be reported. Otherwise, children starting
29475 at @var{from} (zero-based) and up to and excluding @var{to} will be
29478 If a child range is requested, it will only affect the current call to
29479 @code{-var-list-children}, but not future calls to @code{-var-update}.
29480 For this, you must instead use @code{-var-set-update-range}. The
29481 intent of this approach is to enable a front end to implement any
29482 update approach it likes; for example, scrolling a view may cause the
29483 front end to request more children with @code{-var-list-children}, and
29484 then the front end could call @code{-var-set-update-range} with a
29485 different range to ensure that future updates are restricted to just
29488 For each child the following results are returned:
29493 Name of the variable object created for this child.
29496 The expression to be shown to the user by the front end to designate this child.
29497 For example this may be the name of a structure member.
29499 For a dynamic varobj, this value cannot be used to form an
29500 expression. There is no way to do this at all with a dynamic varobj.
29502 For C/C@t{++} structures there are several pseudo children returned to
29503 designate access qualifiers. For these pseudo children @var{exp} is
29504 @samp{public}, @samp{private}, or @samp{protected}. In this case the
29505 type and value are not present.
29507 A dynamic varobj will not report the access qualifying
29508 pseudo-children, regardless of the language. This information is not
29509 available at all with a dynamic varobj.
29512 Number of children this child has. For a dynamic varobj, this will be
29516 The type of the child. If @samp{print object}
29517 (@pxref{Print Settings, set print object}) is set to @code{on}, the
29518 @emph{actual} (derived) type of the object is shown rather than the
29519 @emph{declared} one.
29522 If values were requested, this is the value.
29525 If this variable object is associated with a thread, this is the
29526 thread's global thread id. Otherwise this result is not present.
29529 If the variable object is frozen, this variable will be present with a value of 1.
29532 A dynamic varobj can supply a display hint to the front end. The
29533 value comes directly from the Python pretty-printer object's
29534 @code{display_hint} method. @xref{Pretty Printing API}.
29537 This attribute will be present and have the value @samp{1} if the
29538 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29539 then this attribute will not be present.
29543 The result may have its own attributes:
29547 A dynamic varobj can supply a display hint to the front end. The
29548 value comes directly from the Python pretty-printer object's
29549 @code{display_hint} method. @xref{Pretty Printing API}.
29552 This is an integer attribute which is nonzero if there are children
29553 remaining after the end of the selected range.
29556 @subsubheading Example
29560 -var-list-children n
29561 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29562 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
29564 -var-list-children --all-values n
29565 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29566 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
29570 @subheading The @code{-var-info-type} Command
29571 @findex -var-info-type
29573 @subsubheading Synopsis
29576 -var-info-type @var{name}
29579 Returns the type of the specified variable @var{name}. The type is
29580 returned as a string in the same format as it is output by the
29584 type=@var{typename}
29588 @subheading The @code{-var-info-expression} Command
29589 @findex -var-info-expression
29591 @subsubheading Synopsis
29594 -var-info-expression @var{name}
29597 Returns a string that is suitable for presenting this
29598 variable object in user interface. The string is generally
29599 not valid expression in the current language, and cannot be evaluated.
29601 For example, if @code{a} is an array, and variable object
29602 @code{A} was created for @code{a}, then we'll get this output:
29605 (gdb) -var-info-expression A.1
29606 ^done,lang="C",exp="1"
29610 Here, the value of @code{lang} is the language name, which can be
29611 found in @ref{Supported Languages}.
29613 Note that the output of the @code{-var-list-children} command also
29614 includes those expressions, so the @code{-var-info-expression} command
29617 @subheading The @code{-var-info-path-expression} Command
29618 @findex -var-info-path-expression
29620 @subsubheading Synopsis
29623 -var-info-path-expression @var{name}
29626 Returns an expression that can be evaluated in the current
29627 context and will yield the same value that a variable object has.
29628 Compare this with the @code{-var-info-expression} command, which
29629 result can be used only for UI presentation. Typical use of
29630 the @code{-var-info-path-expression} command is creating a
29631 watchpoint from a variable object.
29633 This command is currently not valid for children of a dynamic varobj,
29634 and will give an error when invoked on one.
29636 For example, suppose @code{C} is a C@t{++} class, derived from class
29637 @code{Base}, and that the @code{Base} class has a member called
29638 @code{m_size}. Assume a variable @code{c} is has the type of
29639 @code{C} and a variable object @code{C} was created for variable
29640 @code{c}. Then, we'll get this output:
29642 (gdb) -var-info-path-expression C.Base.public.m_size
29643 ^done,path_expr=((Base)c).m_size)
29646 @subheading The @code{-var-show-attributes} Command
29647 @findex -var-show-attributes
29649 @subsubheading Synopsis
29652 -var-show-attributes @var{name}
29655 List attributes of the specified variable object @var{name}:
29658 status=@var{attr} [ ( ,@var{attr} )* ]
29662 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
29664 @subheading The @code{-var-evaluate-expression} Command
29665 @findex -var-evaluate-expression
29667 @subsubheading Synopsis
29670 -var-evaluate-expression [-f @var{format-spec}] @var{name}
29673 Evaluates the expression that is represented by the specified variable
29674 object and returns its value as a string. The format of the string
29675 can be specified with the @samp{-f} option. The possible values of
29676 this option are the same as for @code{-var-set-format}
29677 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
29678 the current display format will be used. The current display format
29679 can be changed using the @code{-var-set-format} command.
29685 Note that one must invoke @code{-var-list-children} for a variable
29686 before the value of a child variable can be evaluated.
29688 @subheading The @code{-var-assign} Command
29689 @findex -var-assign
29691 @subsubheading Synopsis
29694 -var-assign @var{name} @var{expression}
29697 Assigns the value of @var{expression} to the variable object specified
29698 by @var{name}. The object must be @samp{editable}. If the variable's
29699 value is altered by the assign, the variable will show up in any
29700 subsequent @code{-var-update} list.
29702 @subsubheading Example
29710 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
29714 @subheading The @code{-var-update} Command
29715 @findex -var-update
29717 @subsubheading Synopsis
29720 -var-update [@var{print-values}] @{@var{name} | "*"@}
29723 Reevaluate the expressions corresponding to the variable object
29724 @var{name} and all its direct and indirect children, and return the
29725 list of variable objects whose values have changed; @var{name} must
29726 be a root variable object. Here, ``changed'' means that the result of
29727 @code{-var-evaluate-expression} before and after the
29728 @code{-var-update} is different. If @samp{*} is used as the variable
29729 object names, all existing variable objects are updated, except
29730 for frozen ones (@pxref{-var-set-frozen}). The option
29731 @var{print-values} determines whether both names and values, or just
29732 names are printed. The possible values of this option are the same
29733 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
29734 recommended to use the @samp{--all-values} option, to reduce the
29735 number of MI commands needed on each program stop.
29737 With the @samp{*} parameter, if a variable object is bound to a
29738 currently running thread, it will not be updated, without any
29741 If @code{-var-set-update-range} was previously used on a varobj, then
29742 only the selected range of children will be reported.
29744 @code{-var-update} reports all the changed varobjs in a tuple named
29747 Each item in the change list is itself a tuple holding:
29751 The name of the varobj.
29754 If values were requested for this update, then this field will be
29755 present and will hold the value of the varobj.
29758 @anchor{-var-update}
29759 This field is a string which may take one of three values:
29763 The variable object's current value is valid.
29766 The variable object does not currently hold a valid value but it may
29767 hold one in the future if its associated expression comes back into
29771 The variable object no longer holds a valid value.
29772 This can occur when the executable file being debugged has changed,
29773 either through recompilation or by using the @value{GDBN} @code{file}
29774 command. The front end should normally choose to delete these variable
29778 In the future new values may be added to this list so the front should
29779 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
29782 This is only present if the varobj is still valid. If the type
29783 changed, then this will be the string @samp{true}; otherwise it will
29786 When a varobj's type changes, its children are also likely to have
29787 become incorrect. Therefore, the varobj's children are automatically
29788 deleted when this attribute is @samp{true}. Also, the varobj's update
29789 range, when set using the @code{-var-set-update-range} command, is
29793 If the varobj's type changed, then this field will be present and will
29796 @item new_num_children
29797 For a dynamic varobj, if the number of children changed, or if the
29798 type changed, this will be the new number of children.
29800 The @samp{numchild} field in other varobj responses is generally not
29801 valid for a dynamic varobj -- it will show the number of children that
29802 @value{GDBN} knows about, but because dynamic varobjs lazily
29803 instantiate their children, this will not reflect the number of
29804 children which may be available.
29806 The @samp{new_num_children} attribute only reports changes to the
29807 number of children known by @value{GDBN}. This is the only way to
29808 detect whether an update has removed children (which necessarily can
29809 only happen at the end of the update range).
29812 The display hint, if any.
29815 This is an integer value, which will be 1 if there are more children
29816 available outside the varobj's update range.
29819 This attribute will be present and have the value @samp{1} if the
29820 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29821 then this attribute will not be present.
29824 If new children were added to a dynamic varobj within the selected
29825 update range (as set by @code{-var-set-update-range}), then they will
29826 be listed in this attribute.
29829 @subsubheading Example
29836 -var-update --all-values var1
29837 ^done,changelist=[@{name="var1",value="3",in_scope="true",
29838 type_changed="false"@}]
29842 @subheading The @code{-var-set-frozen} Command
29843 @findex -var-set-frozen
29844 @anchor{-var-set-frozen}
29846 @subsubheading Synopsis
29849 -var-set-frozen @var{name} @var{flag}
29852 Set the frozenness flag on the variable object @var{name}. The
29853 @var{flag} parameter should be either @samp{1} to make the variable
29854 frozen or @samp{0} to make it unfrozen. If a variable object is
29855 frozen, then neither itself, nor any of its children, are
29856 implicitly updated by @code{-var-update} of
29857 a parent variable or by @code{-var-update *}. Only
29858 @code{-var-update} of the variable itself will update its value and
29859 values of its children. After a variable object is unfrozen, it is
29860 implicitly updated by all subsequent @code{-var-update} operations.
29861 Unfreezing a variable does not update it, only subsequent
29862 @code{-var-update} does.
29864 @subsubheading Example
29868 -var-set-frozen V 1
29873 @subheading The @code{-var-set-update-range} command
29874 @findex -var-set-update-range
29875 @anchor{-var-set-update-range}
29877 @subsubheading Synopsis
29880 -var-set-update-range @var{name} @var{from} @var{to}
29883 Set the range of children to be returned by future invocations of
29884 @code{-var-update}.
29886 @var{from} and @var{to} indicate the range of children to report. If
29887 @var{from} or @var{to} is less than zero, the range is reset and all
29888 children will be reported. Otherwise, children starting at @var{from}
29889 (zero-based) and up to and excluding @var{to} will be reported.
29891 @subsubheading Example
29895 -var-set-update-range V 1 2
29899 @subheading The @code{-var-set-visualizer} command
29900 @findex -var-set-visualizer
29901 @anchor{-var-set-visualizer}
29903 @subsubheading Synopsis
29906 -var-set-visualizer @var{name} @var{visualizer}
29909 Set a visualizer for the variable object @var{name}.
29911 @var{visualizer} is the visualizer to use. The special value
29912 @samp{None} means to disable any visualizer in use.
29914 If not @samp{None}, @var{visualizer} must be a Python expression.
29915 This expression must evaluate to a callable object which accepts a
29916 single argument. @value{GDBN} will call this object with the value of
29917 the varobj @var{name} as an argument (this is done so that the same
29918 Python pretty-printing code can be used for both the CLI and MI).
29919 When called, this object must return an object which conforms to the
29920 pretty-printing interface (@pxref{Pretty Printing API}).
29922 The pre-defined function @code{gdb.default_visualizer} may be used to
29923 select a visualizer by following the built-in process
29924 (@pxref{Selecting Pretty-Printers}). This is done automatically when
29925 a varobj is created, and so ordinarily is not needed.
29927 This feature is only available if Python support is enabled. The MI
29928 command @code{-list-features} (@pxref{GDB/MI Support Commands})
29929 can be used to check this.
29931 @subsubheading Example
29933 Resetting the visualizer:
29937 -var-set-visualizer V None
29941 Reselecting the default (type-based) visualizer:
29945 -var-set-visualizer V gdb.default_visualizer
29949 Suppose @code{SomeClass} is a visualizer class. A lambda expression
29950 can be used to instantiate this class for a varobj:
29954 -var-set-visualizer V "lambda val: SomeClass()"
29958 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29959 @node GDB/MI Data Manipulation
29960 @section @sc{gdb/mi} Data Manipulation
29962 @cindex data manipulation, in @sc{gdb/mi}
29963 @cindex @sc{gdb/mi}, data manipulation
29964 This section describes the @sc{gdb/mi} commands that manipulate data:
29965 examine memory and registers, evaluate expressions, etc.
29967 For details about what an addressable memory unit is,
29968 @pxref{addressable memory unit}.
29970 @c REMOVED FROM THE INTERFACE.
29971 @c @subheading -data-assign
29972 @c Change the value of a program variable. Plenty of side effects.
29973 @c @subsubheading GDB Command
29975 @c @subsubheading Example
29978 @subheading The @code{-data-disassemble} Command
29979 @findex -data-disassemble
29981 @subsubheading Synopsis
29985 [ -s @var{start-addr} -e @var{end-addr} ]
29986 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
29994 @item @var{start-addr}
29995 is the beginning address (or @code{$pc})
29996 @item @var{end-addr}
29998 @item @var{filename}
29999 is the name of the file to disassemble
30000 @item @var{linenum}
30001 is the line number to disassemble around
30003 is the number of disassembly lines to be produced. If it is -1,
30004 the whole function will be disassembled, in case no @var{end-addr} is
30005 specified. If @var{end-addr} is specified as a non-zero value, and
30006 @var{lines} is lower than the number of disassembly lines between
30007 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
30008 displayed; if @var{lines} is higher than the number of lines between
30009 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
30014 @item 0 disassembly only
30015 @item 1 mixed source and disassembly (deprecated)
30016 @item 2 disassembly with raw opcodes
30017 @item 3 mixed source and disassembly with raw opcodes (deprecated)
30018 @item 4 mixed source and disassembly
30019 @item 5 mixed source and disassembly with raw opcodes
30022 Modes 1 and 3 are deprecated. The output is ``source centric''
30023 which hasn't proved useful in practice.
30024 @xref{Machine Code}, for a discussion of the difference between
30025 @code{/m} and @code{/s} output of the @code{disassemble} command.
30028 @subsubheading Result
30030 The result of the @code{-data-disassemble} command will be a list named
30031 @samp{asm_insns}, the contents of this list depend on the @var{mode}
30032 used with the @code{-data-disassemble} command.
30034 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
30039 The address at which this instruction was disassembled.
30042 The name of the function this instruction is within.
30045 The decimal offset in bytes from the start of @samp{func-name}.
30048 The text disassembly for this @samp{address}.
30051 This field is only present for modes 2, 3 and 5. This contains the raw opcode
30052 bytes for the @samp{inst} field.
30056 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
30057 @samp{src_and_asm_line}, each of which has the following fields:
30061 The line number within @samp{file}.
30064 The file name from the compilation unit. This might be an absolute
30065 file name or a relative file name depending on the compile command
30069 Absolute file name of @samp{file}. It is converted to a canonical form
30070 using the source file search path
30071 (@pxref{Source Path, ,Specifying Source Directories})
30072 and after resolving all the symbolic links.
30074 If the source file is not found this field will contain the path as
30075 present in the debug information.
30077 @item line_asm_insn
30078 This is a list of tuples containing the disassembly for @samp{line} in
30079 @samp{file}. The fields of each tuple are the same as for
30080 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
30081 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
30086 Note that whatever included in the @samp{inst} field, is not
30087 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
30090 @subsubheading @value{GDBN} Command
30092 The corresponding @value{GDBN} command is @samp{disassemble}.
30094 @subsubheading Example
30096 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
30100 -data-disassemble -s $pc -e "$pc + 20" -- 0
30103 @{address="0x000107c0",func-name="main",offset="4",
30104 inst="mov 2, %o0"@},
30105 @{address="0x000107c4",func-name="main",offset="8",
30106 inst="sethi %hi(0x11800), %o2"@},
30107 @{address="0x000107c8",func-name="main",offset="12",
30108 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
30109 @{address="0x000107cc",func-name="main",offset="16",
30110 inst="sethi %hi(0x11800), %o2"@},
30111 @{address="0x000107d0",func-name="main",offset="20",
30112 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
30116 Disassemble the whole @code{main} function. Line 32 is part of
30120 -data-disassemble -f basics.c -l 32 -- 0
30122 @{address="0x000107bc",func-name="main",offset="0",
30123 inst="save %sp, -112, %sp"@},
30124 @{address="0x000107c0",func-name="main",offset="4",
30125 inst="mov 2, %o0"@},
30126 @{address="0x000107c4",func-name="main",offset="8",
30127 inst="sethi %hi(0x11800), %o2"@},
30129 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
30130 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
30134 Disassemble 3 instructions from the start of @code{main}:
30138 -data-disassemble -f basics.c -l 32 -n 3 -- 0
30140 @{address="0x000107bc",func-name="main",offset="0",
30141 inst="save %sp, -112, %sp"@},
30142 @{address="0x000107c0",func-name="main",offset="4",
30143 inst="mov 2, %o0"@},
30144 @{address="0x000107c4",func-name="main",offset="8",
30145 inst="sethi %hi(0x11800), %o2"@}]
30149 Disassemble 3 instructions from the start of @code{main} in mixed mode:
30153 -data-disassemble -f basics.c -l 32 -n 3 -- 1
30155 src_and_asm_line=@{line="31",
30156 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
30157 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
30158 line_asm_insn=[@{address="0x000107bc",
30159 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
30160 src_and_asm_line=@{line="32",
30161 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
30162 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
30163 line_asm_insn=[@{address="0x000107c0",
30164 func-name="main",offset="4",inst="mov 2, %o0"@},
30165 @{address="0x000107c4",func-name="main",offset="8",
30166 inst="sethi %hi(0x11800), %o2"@}]@}]
30171 @subheading The @code{-data-evaluate-expression} Command
30172 @findex -data-evaluate-expression
30174 @subsubheading Synopsis
30177 -data-evaluate-expression @var{expr}
30180 Evaluate @var{expr} as an expression. The expression could contain an
30181 inferior function call. The function call will execute synchronously.
30182 If the expression contains spaces, it must be enclosed in double quotes.
30184 @subsubheading @value{GDBN} Command
30186 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
30187 @samp{call}. In @code{gdbtk} only, there's a corresponding
30188 @samp{gdb_eval} command.
30190 @subsubheading Example
30192 In the following example, the numbers that precede the commands are the
30193 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
30194 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
30198 211-data-evaluate-expression A
30201 311-data-evaluate-expression &A
30202 311^done,value="0xefffeb7c"
30204 411-data-evaluate-expression A+3
30207 511-data-evaluate-expression "A + 3"
30213 @subheading The @code{-data-list-changed-registers} Command
30214 @findex -data-list-changed-registers
30216 @subsubheading Synopsis
30219 -data-list-changed-registers
30222 Display a list of the registers that have changed.
30224 @subsubheading @value{GDBN} Command
30226 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
30227 has the corresponding command @samp{gdb_changed_register_list}.
30229 @subsubheading Example
30231 On a PPC MBX board:
30239 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
30240 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
30243 -data-list-changed-registers
30244 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
30245 "10","11","13","14","15","16","17","18","19","20","21","22","23",
30246 "24","25","26","27","28","30","31","64","65","66","67","69"]
30251 @subheading The @code{-data-list-register-names} Command
30252 @findex -data-list-register-names
30254 @subsubheading Synopsis
30257 -data-list-register-names [ ( @var{regno} )+ ]
30260 Show a list of register names for the current target. If no arguments
30261 are given, it shows a list of the names of all the registers. If
30262 integer numbers are given as arguments, it will print a list of the
30263 names of the registers corresponding to the arguments. To ensure
30264 consistency between a register name and its number, the output list may
30265 include empty register names.
30267 @subsubheading @value{GDBN} Command
30269 @value{GDBN} does not have a command which corresponds to
30270 @samp{-data-list-register-names}. In @code{gdbtk} there is a
30271 corresponding command @samp{gdb_regnames}.
30273 @subsubheading Example
30275 For the PPC MBX board:
30278 -data-list-register-names
30279 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
30280 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
30281 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
30282 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
30283 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
30284 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
30285 "", "pc","ps","cr","lr","ctr","xer"]
30287 -data-list-register-names 1 2 3
30288 ^done,register-names=["r1","r2","r3"]
30292 @subheading The @code{-data-list-register-values} Command
30293 @findex -data-list-register-values
30295 @subsubheading Synopsis
30298 -data-list-register-values
30299 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
30302 Display the registers' contents. The format according to which the
30303 registers' contents are to be returned is given by @var{fmt}, followed
30304 by an optional list of numbers specifying the registers to display. A
30305 missing list of numbers indicates that the contents of all the
30306 registers must be returned. The @code{--skip-unavailable} option
30307 indicates that only the available registers are to be returned.
30309 Allowed formats for @var{fmt} are:
30326 @subsubheading @value{GDBN} Command
30328 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
30329 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
30331 @subsubheading Example
30333 For a PPC MBX board (note: line breaks are for readability only, they
30334 don't appear in the actual output):
30338 -data-list-register-values r 64 65
30339 ^done,register-values=[@{number="64",value="0xfe00a300"@},
30340 @{number="65",value="0x00029002"@}]
30342 -data-list-register-values x
30343 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
30344 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
30345 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
30346 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
30347 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
30348 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
30349 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
30350 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
30351 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
30352 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
30353 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
30354 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
30355 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
30356 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
30357 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
30358 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
30359 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
30360 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
30361 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
30362 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
30363 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
30364 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
30365 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
30366 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
30367 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
30368 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
30369 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
30370 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
30371 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
30372 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
30373 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
30374 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
30375 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
30376 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
30377 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
30378 @{number="69",value="0x20002b03"@}]
30383 @subheading The @code{-data-read-memory} Command
30384 @findex -data-read-memory
30386 This command is deprecated, use @code{-data-read-memory-bytes} instead.
30388 @subsubheading Synopsis
30391 -data-read-memory [ -o @var{byte-offset} ]
30392 @var{address} @var{word-format} @var{word-size}
30393 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
30400 @item @var{address}
30401 An expression specifying the address of the first memory word to be
30402 read. Complex expressions containing embedded white space should be
30403 quoted using the C convention.
30405 @item @var{word-format}
30406 The format to be used to print the memory words. The notation is the
30407 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
30410 @item @var{word-size}
30411 The size of each memory word in bytes.
30413 @item @var{nr-rows}
30414 The number of rows in the output table.
30416 @item @var{nr-cols}
30417 The number of columns in the output table.
30420 If present, indicates that each row should include an @sc{ascii} dump. The
30421 value of @var{aschar} is used as a padding character when a byte is not a
30422 member of the printable @sc{ascii} character set (printable @sc{ascii}
30423 characters are those whose code is between 32 and 126, inclusively).
30425 @item @var{byte-offset}
30426 An offset to add to the @var{address} before fetching memory.
30429 This command displays memory contents as a table of @var{nr-rows} by
30430 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
30431 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
30432 (returned as @samp{total-bytes}). Should less than the requested number
30433 of bytes be returned by the target, the missing words are identified
30434 using @samp{N/A}. The number of bytes read from the target is returned
30435 in @samp{nr-bytes} and the starting address used to read memory in
30438 The address of the next/previous row or page is available in
30439 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
30442 @subsubheading @value{GDBN} Command
30444 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
30445 @samp{gdb_get_mem} memory read command.
30447 @subsubheading Example
30449 Read six bytes of memory starting at @code{bytes+6} but then offset by
30450 @code{-6} bytes. Format as three rows of two columns. One byte per
30451 word. Display each word in hex.
30455 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
30456 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
30457 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
30458 prev-page="0x0000138a",memory=[
30459 @{addr="0x00001390",data=["0x00","0x01"]@},
30460 @{addr="0x00001392",data=["0x02","0x03"]@},
30461 @{addr="0x00001394",data=["0x04","0x05"]@}]
30465 Read two bytes of memory starting at address @code{shorts + 64} and
30466 display as a single word formatted in decimal.
30470 5-data-read-memory shorts+64 d 2 1 1
30471 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
30472 next-row="0x00001512",prev-row="0x0000150e",
30473 next-page="0x00001512",prev-page="0x0000150e",memory=[
30474 @{addr="0x00001510",data=["128"]@}]
30478 Read thirty two bytes of memory starting at @code{bytes+16} and format
30479 as eight rows of four columns. Include a string encoding with @samp{x}
30480 used as the non-printable character.
30484 4-data-read-memory bytes+16 x 1 8 4 x
30485 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
30486 next-row="0x000013c0",prev-row="0x0000139c",
30487 next-page="0x000013c0",prev-page="0x00001380",memory=[
30488 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
30489 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
30490 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
30491 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
30492 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
30493 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
30494 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
30495 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
30499 @subheading The @code{-data-read-memory-bytes} Command
30500 @findex -data-read-memory-bytes
30502 @subsubheading Synopsis
30505 -data-read-memory-bytes [ -o @var{offset} ]
30506 @var{address} @var{count}
30513 @item @var{address}
30514 An expression specifying the address of the first addressable memory unit
30515 to be read. Complex expressions containing embedded white space should be
30516 quoted using the C convention.
30519 The number of addressable memory units to read. This should be an integer
30523 The offset relative to @var{address} at which to start reading. This
30524 should be an integer literal. This option is provided so that a frontend
30525 is not required to first evaluate address and then perform address
30526 arithmetics itself.
30530 This command attempts to read all accessible memory regions in the
30531 specified range. First, all regions marked as unreadable in the memory
30532 map (if one is defined) will be skipped. @xref{Memory Region
30533 Attributes}. Second, @value{GDBN} will attempt to read the remaining
30534 regions. For each one, if reading full region results in an errors,
30535 @value{GDBN} will try to read a subset of the region.
30537 In general, every single memory unit in the region may be readable or not,
30538 and the only way to read every readable unit is to try a read at
30539 every address, which is not practical. Therefore, @value{GDBN} will
30540 attempt to read all accessible memory units at either beginning or the end
30541 of the region, using a binary division scheme. This heuristic works
30542 well for reading accross a memory map boundary. Note that if a region
30543 has a readable range that is neither at the beginning or the end,
30544 @value{GDBN} will not read it.
30546 The result record (@pxref{GDB/MI Result Records}) that is output of
30547 the command includes a field named @samp{memory} whose content is a
30548 list of tuples. Each tuple represent a successfully read memory block
30549 and has the following fields:
30553 The start address of the memory block, as hexadecimal literal.
30556 The end address of the memory block, as hexadecimal literal.
30559 The offset of the memory block, as hexadecimal literal, relative to
30560 the start address passed to @code{-data-read-memory-bytes}.
30563 The contents of the memory block, in hex.
30569 @subsubheading @value{GDBN} Command
30571 The corresponding @value{GDBN} command is @samp{x}.
30573 @subsubheading Example
30577 -data-read-memory-bytes &a 10
30578 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
30580 contents="01000000020000000300"@}]
30585 @subheading The @code{-data-write-memory-bytes} Command
30586 @findex -data-write-memory-bytes
30588 @subsubheading Synopsis
30591 -data-write-memory-bytes @var{address} @var{contents}
30592 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
30599 @item @var{address}
30600 An expression specifying the address of the first addressable memory unit
30601 to be written. Complex expressions containing embedded white space should
30602 be quoted using the C convention.
30604 @item @var{contents}
30605 The hex-encoded data to write. It is an error if @var{contents} does
30606 not represent an integral number of addressable memory units.
30609 Optional argument indicating the number of addressable memory units to be
30610 written. If @var{count} is greater than @var{contents}' length,
30611 @value{GDBN} will repeatedly write @var{contents} until it fills
30612 @var{count} memory units.
30616 @subsubheading @value{GDBN} Command
30618 There's no corresponding @value{GDBN} command.
30620 @subsubheading Example
30624 -data-write-memory-bytes &a "aabbccdd"
30631 -data-write-memory-bytes &a "aabbccdd" 16e
30636 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30637 @node GDB/MI Tracepoint Commands
30638 @section @sc{gdb/mi} Tracepoint Commands
30640 The commands defined in this section implement MI support for
30641 tracepoints. For detailed introduction, see @ref{Tracepoints}.
30643 @subheading The @code{-trace-find} Command
30644 @findex -trace-find
30646 @subsubheading Synopsis
30649 -trace-find @var{mode} [@var{parameters}@dots{}]
30652 Find a trace frame using criteria defined by @var{mode} and
30653 @var{parameters}. The following table lists permissible
30654 modes and their parameters. For details of operation, see @ref{tfind}.
30659 No parameters are required. Stops examining trace frames.
30662 An integer is required as parameter. Selects tracepoint frame with
30665 @item tracepoint-number
30666 An integer is required as parameter. Finds next
30667 trace frame that corresponds to tracepoint with the specified number.
30670 An address is required as parameter. Finds
30671 next trace frame that corresponds to any tracepoint at the specified
30674 @item pc-inside-range
30675 Two addresses are required as parameters. Finds next trace
30676 frame that corresponds to a tracepoint at an address inside the
30677 specified range. Both bounds are considered to be inside the range.
30679 @item pc-outside-range
30680 Two addresses are required as parameters. Finds
30681 next trace frame that corresponds to a tracepoint at an address outside
30682 the specified range. Both bounds are considered to be inside the range.
30685 Line specification is required as parameter. @xref{Specify Location}.
30686 Finds next trace frame that corresponds to a tracepoint at
30687 the specified location.
30691 If @samp{none} was passed as @var{mode}, the response does not
30692 have fields. Otherwise, the response may have the following fields:
30696 This field has either @samp{0} or @samp{1} as the value, depending
30697 on whether a matching tracepoint was found.
30700 The index of the found traceframe. This field is present iff
30701 the @samp{found} field has value of @samp{1}.
30704 The index of the found tracepoint. This field is present iff
30705 the @samp{found} field has value of @samp{1}.
30708 The information about the frame corresponding to the found trace
30709 frame. This field is present only if a trace frame was found.
30710 @xref{GDB/MI Frame Information}, for description of this field.
30714 @subsubheading @value{GDBN} Command
30716 The corresponding @value{GDBN} command is @samp{tfind}.
30718 @subheading -trace-define-variable
30719 @findex -trace-define-variable
30721 @subsubheading Synopsis
30724 -trace-define-variable @var{name} [ @var{value} ]
30727 Create trace variable @var{name} if it does not exist. If
30728 @var{value} is specified, sets the initial value of the specified
30729 trace variable to that value. Note that the @var{name} should start
30730 with the @samp{$} character.
30732 @subsubheading @value{GDBN} Command
30734 The corresponding @value{GDBN} command is @samp{tvariable}.
30736 @subheading The @code{-trace-frame-collected} Command
30737 @findex -trace-frame-collected
30739 @subsubheading Synopsis
30742 -trace-frame-collected
30743 [--var-print-values @var{var_pval}]
30744 [--comp-print-values @var{comp_pval}]
30745 [--registers-format @var{regformat}]
30746 [--memory-contents]
30749 This command returns the set of collected objects, register names,
30750 trace state variable names, memory ranges and computed expressions
30751 that have been collected at a particular trace frame. The optional
30752 parameters to the command affect the output format in different ways.
30753 See the output description table below for more details.
30755 The reported names can be used in the normal manner to create
30756 varobjs and inspect the objects themselves. The items returned by
30757 this command are categorized so that it is clear which is a variable,
30758 which is a register, which is a trace state variable, which is a
30759 memory range and which is a computed expression.
30761 For instance, if the actions were
30763 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
30764 collect *(int*)0xaf02bef0@@40
30768 the object collected in its entirety would be @code{myVar}. The
30769 object @code{myArray} would be partially collected, because only the
30770 element at index @code{myIndex} would be collected. The remaining
30771 objects would be computed expressions.
30773 An example output would be:
30777 -trace-frame-collected
30779 explicit-variables=[@{name="myVar",value="1"@}],
30780 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
30781 @{name="myObj.field",value="0"@},
30782 @{name="myPtr->field",value="1"@},
30783 @{name="myCount + 2",value="3"@},
30784 @{name="$tvar1 + 1",value="43970027"@}],
30785 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
30786 @{number="1",value="0x0"@},
30787 @{number="2",value="0x4"@},
30789 @{number="125",value="0x0"@}],
30790 tvars=[@{name="$tvar1",current="43970026"@}],
30791 memory=[@{address="0x0000000000602264",length="4"@},
30792 @{address="0x0000000000615bc0",length="4"@}]
30799 @item explicit-variables
30800 The set of objects that have been collected in their entirety (as
30801 opposed to collecting just a few elements of an array or a few struct
30802 members). For each object, its name and value are printed.
30803 The @code{--var-print-values} option affects how or whether the value
30804 field is output. If @var{var_pval} is 0, then print only the names;
30805 if it is 1, print also their values; and if it is 2, print the name,
30806 type and value for simple data types, and the name and type for
30807 arrays, structures and unions.
30809 @item computed-expressions
30810 The set of computed expressions that have been collected at the
30811 current trace frame. The @code{--comp-print-values} option affects
30812 this set like the @code{--var-print-values} option affects the
30813 @code{explicit-variables} set. See above.
30816 The registers that have been collected at the current trace frame.
30817 For each register collected, the name and current value are returned.
30818 The value is formatted according to the @code{--registers-format}
30819 option. See the @command{-data-list-register-values} command for a
30820 list of the allowed formats. The default is @samp{x}.
30823 The trace state variables that have been collected at the current
30824 trace frame. For each trace state variable collected, the name and
30825 current value are returned.
30828 The set of memory ranges that have been collected at the current trace
30829 frame. Its content is a list of tuples. Each tuple represents a
30830 collected memory range and has the following fields:
30834 The start address of the memory range, as hexadecimal literal.
30837 The length of the memory range, as decimal literal.
30840 The contents of the memory block, in hex. This field is only present
30841 if the @code{--memory-contents} option is specified.
30847 @subsubheading @value{GDBN} Command
30849 There is no corresponding @value{GDBN} command.
30851 @subsubheading Example
30853 @subheading -trace-list-variables
30854 @findex -trace-list-variables
30856 @subsubheading Synopsis
30859 -trace-list-variables
30862 Return a table of all defined trace variables. Each element of the
30863 table has the following fields:
30867 The name of the trace variable. This field is always present.
30870 The initial value. This is a 64-bit signed integer. This
30871 field is always present.
30874 The value the trace variable has at the moment. This is a 64-bit
30875 signed integer. This field is absent iff current value is
30876 not defined, for example if the trace was never run, or is
30881 @subsubheading @value{GDBN} Command
30883 The corresponding @value{GDBN} command is @samp{tvariables}.
30885 @subsubheading Example
30889 -trace-list-variables
30890 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
30891 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
30892 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
30893 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
30894 body=[variable=@{name="$trace_timestamp",initial="0"@}
30895 variable=@{name="$foo",initial="10",current="15"@}]@}
30899 @subheading -trace-save
30900 @findex -trace-save
30902 @subsubheading Synopsis
30905 -trace-save [-r ] @var{filename}
30908 Saves the collected trace data to @var{filename}. Without the
30909 @samp{-r} option, the data is downloaded from the target and saved
30910 in a local file. With the @samp{-r} option the target is asked
30911 to perform the save.
30913 @subsubheading @value{GDBN} Command
30915 The corresponding @value{GDBN} command is @samp{tsave}.
30918 @subheading -trace-start
30919 @findex -trace-start
30921 @subsubheading Synopsis
30927 Starts a tracing experiments. The result of this command does not
30930 @subsubheading @value{GDBN} Command
30932 The corresponding @value{GDBN} command is @samp{tstart}.
30934 @subheading -trace-status
30935 @findex -trace-status
30937 @subsubheading Synopsis
30943 Obtains the status of a tracing experiment. The result may include
30944 the following fields:
30949 May have a value of either @samp{0}, when no tracing operations are
30950 supported, @samp{1}, when all tracing operations are supported, or
30951 @samp{file} when examining trace file. In the latter case, examining
30952 of trace frame is possible but new tracing experiement cannot be
30953 started. This field is always present.
30956 May have a value of either @samp{0} or @samp{1} depending on whether
30957 tracing experiement is in progress on target. This field is present
30958 if @samp{supported} field is not @samp{0}.
30961 Report the reason why the tracing was stopped last time. This field
30962 may be absent iff tracing was never stopped on target yet. The
30963 value of @samp{request} means the tracing was stopped as result of
30964 the @code{-trace-stop} command. The value of @samp{overflow} means
30965 the tracing buffer is full. The value of @samp{disconnection} means
30966 tracing was automatically stopped when @value{GDBN} has disconnected.
30967 The value of @samp{passcount} means tracing was stopped when a
30968 tracepoint was passed a maximal number of times for that tracepoint.
30969 This field is present if @samp{supported} field is not @samp{0}.
30971 @item stopping-tracepoint
30972 The number of tracepoint whose passcount as exceeded. This field is
30973 present iff the @samp{stop-reason} field has the value of
30977 @itemx frames-created
30978 The @samp{frames} field is a count of the total number of trace frames
30979 in the trace buffer, while @samp{frames-created} is the total created
30980 during the run, including ones that were discarded, such as when a
30981 circular trace buffer filled up. Both fields are optional.
30985 These fields tell the current size of the tracing buffer and the
30986 remaining space. These fields are optional.
30989 The value of the circular trace buffer flag. @code{1} means that the
30990 trace buffer is circular and old trace frames will be discarded if
30991 necessary to make room, @code{0} means that the trace buffer is linear
30995 The value of the disconnected tracing flag. @code{1} means that
30996 tracing will continue after @value{GDBN} disconnects, @code{0} means
30997 that the trace run will stop.
31000 The filename of the trace file being examined. This field is
31001 optional, and only present when examining a trace file.
31005 @subsubheading @value{GDBN} Command
31007 The corresponding @value{GDBN} command is @samp{tstatus}.
31009 @subheading -trace-stop
31010 @findex -trace-stop
31012 @subsubheading Synopsis
31018 Stops a tracing experiment. The result of this command has the same
31019 fields as @code{-trace-status}, except that the @samp{supported} and
31020 @samp{running} fields are not output.
31022 @subsubheading @value{GDBN} Command
31024 The corresponding @value{GDBN} command is @samp{tstop}.
31027 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31028 @node GDB/MI Symbol Query
31029 @section @sc{gdb/mi} Symbol Query Commands
31033 @subheading The @code{-symbol-info-address} Command
31034 @findex -symbol-info-address
31036 @subsubheading Synopsis
31039 -symbol-info-address @var{symbol}
31042 Describe where @var{symbol} is stored.
31044 @subsubheading @value{GDBN} Command
31046 The corresponding @value{GDBN} command is @samp{info address}.
31048 @subsubheading Example
31052 @subheading The @code{-symbol-info-file} Command
31053 @findex -symbol-info-file
31055 @subsubheading Synopsis
31061 Show the file for the symbol.
31063 @subsubheading @value{GDBN} Command
31065 There's no equivalent @value{GDBN} command. @code{gdbtk} has
31066 @samp{gdb_find_file}.
31068 @subsubheading Example
31072 @subheading The @code{-symbol-info-function} Command
31073 @findex -symbol-info-function
31075 @subsubheading Synopsis
31078 -symbol-info-function
31081 Show which function the symbol lives in.
31083 @subsubheading @value{GDBN} Command
31085 @samp{gdb_get_function} in @code{gdbtk}.
31087 @subsubheading Example
31091 @subheading The @code{-symbol-info-line} Command
31092 @findex -symbol-info-line
31094 @subsubheading Synopsis
31100 Show the core addresses of the code for a source line.
31102 @subsubheading @value{GDBN} Command
31104 The corresponding @value{GDBN} command is @samp{info line}.
31105 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
31107 @subsubheading Example
31111 @subheading The @code{-symbol-info-symbol} Command
31112 @findex -symbol-info-symbol
31114 @subsubheading Synopsis
31117 -symbol-info-symbol @var{addr}
31120 Describe what symbol is at location @var{addr}.
31122 @subsubheading @value{GDBN} Command
31124 The corresponding @value{GDBN} command is @samp{info symbol}.
31126 @subsubheading Example
31130 @subheading The @code{-symbol-list-functions} Command
31131 @findex -symbol-list-functions
31133 @subsubheading Synopsis
31136 -symbol-list-functions
31139 List the functions in the executable.
31141 @subsubheading @value{GDBN} Command
31143 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
31144 @samp{gdb_search} in @code{gdbtk}.
31146 @subsubheading Example
31151 @subheading The @code{-symbol-list-lines} Command
31152 @findex -symbol-list-lines
31154 @subsubheading Synopsis
31157 -symbol-list-lines @var{filename}
31160 Print the list of lines that contain code and their associated program
31161 addresses for the given source filename. The entries are sorted in
31162 ascending PC order.
31164 @subsubheading @value{GDBN} Command
31166 There is no corresponding @value{GDBN} command.
31168 @subsubheading Example
31171 -symbol-list-lines basics.c
31172 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
31178 @subheading The @code{-symbol-list-types} Command
31179 @findex -symbol-list-types
31181 @subsubheading Synopsis
31187 List all the type names.
31189 @subsubheading @value{GDBN} Command
31191 The corresponding commands are @samp{info types} in @value{GDBN},
31192 @samp{gdb_search} in @code{gdbtk}.
31194 @subsubheading Example
31198 @subheading The @code{-symbol-list-variables} Command
31199 @findex -symbol-list-variables
31201 @subsubheading Synopsis
31204 -symbol-list-variables
31207 List all the global and static variable names.
31209 @subsubheading @value{GDBN} Command
31211 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
31213 @subsubheading Example
31217 @subheading The @code{-symbol-locate} Command
31218 @findex -symbol-locate
31220 @subsubheading Synopsis
31226 @subsubheading @value{GDBN} Command
31228 @samp{gdb_loc} in @code{gdbtk}.
31230 @subsubheading Example
31234 @subheading The @code{-symbol-type} Command
31235 @findex -symbol-type
31237 @subsubheading Synopsis
31240 -symbol-type @var{variable}
31243 Show type of @var{variable}.
31245 @subsubheading @value{GDBN} Command
31247 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
31248 @samp{gdb_obj_variable}.
31250 @subsubheading Example
31255 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31256 @node GDB/MI File Commands
31257 @section @sc{gdb/mi} File Commands
31259 This section describes the GDB/MI commands to specify executable file names
31260 and to read in and obtain symbol table information.
31262 @subheading The @code{-file-exec-and-symbols} Command
31263 @findex -file-exec-and-symbols
31265 @subsubheading Synopsis
31268 -file-exec-and-symbols @var{file}
31271 Specify the executable file to be debugged. This file is the one from
31272 which the symbol table is also read. If no file is specified, the
31273 command clears the executable and symbol information. If breakpoints
31274 are set when using this command with no arguments, @value{GDBN} will produce
31275 error messages. Otherwise, no output is produced, except a completion
31278 @subsubheading @value{GDBN} Command
31280 The corresponding @value{GDBN} command is @samp{file}.
31282 @subsubheading Example
31286 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31292 @subheading The @code{-file-exec-file} Command
31293 @findex -file-exec-file
31295 @subsubheading Synopsis
31298 -file-exec-file @var{file}
31301 Specify the executable file to be debugged. Unlike
31302 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
31303 from this file. If used without argument, @value{GDBN} clears the information
31304 about the executable file. No output is produced, except a completion
31307 @subsubheading @value{GDBN} Command
31309 The corresponding @value{GDBN} command is @samp{exec-file}.
31311 @subsubheading Example
31315 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31322 @subheading The @code{-file-list-exec-sections} Command
31323 @findex -file-list-exec-sections
31325 @subsubheading Synopsis
31328 -file-list-exec-sections
31331 List the sections of the current executable file.
31333 @subsubheading @value{GDBN} Command
31335 The @value{GDBN} command @samp{info file} shows, among the rest, the same
31336 information as this command. @code{gdbtk} has a corresponding command
31337 @samp{gdb_load_info}.
31339 @subsubheading Example
31344 @subheading The @code{-file-list-exec-source-file} Command
31345 @findex -file-list-exec-source-file
31347 @subsubheading Synopsis
31350 -file-list-exec-source-file
31353 List the line number, the current source file, and the absolute path
31354 to the current source file for the current executable. The macro
31355 information field has a value of @samp{1} or @samp{0} depending on
31356 whether or not the file includes preprocessor macro information.
31358 @subsubheading @value{GDBN} Command
31360 The @value{GDBN} equivalent is @samp{info source}
31362 @subsubheading Example
31366 123-file-list-exec-source-file
31367 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
31372 @subheading The @code{-file-list-exec-source-files} Command
31373 @findex -file-list-exec-source-files
31375 @subsubheading Synopsis
31378 -file-list-exec-source-files
31381 List the source files for the current executable.
31383 It will always output both the filename and fullname (absolute file
31384 name) of a source file.
31386 @subsubheading @value{GDBN} Command
31388 The @value{GDBN} equivalent is @samp{info sources}.
31389 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
31391 @subsubheading Example
31394 -file-list-exec-source-files
31396 @{file=foo.c,fullname=/home/foo.c@},
31397 @{file=/home/bar.c,fullname=/home/bar.c@},
31398 @{file=gdb_could_not_find_fullpath.c@}]
31403 @subheading The @code{-file-list-shared-libraries} Command
31404 @findex -file-list-shared-libraries
31406 @subsubheading Synopsis
31409 -file-list-shared-libraries
31412 List the shared libraries in the program.
31414 @subsubheading @value{GDBN} Command
31416 The corresponding @value{GDBN} command is @samp{info shared}.
31418 @subsubheading Example
31422 @subheading The @code{-file-list-symbol-files} Command
31423 @findex -file-list-symbol-files
31425 @subsubheading Synopsis
31428 -file-list-symbol-files
31433 @subsubheading @value{GDBN} Command
31435 The corresponding @value{GDBN} command is @samp{info file} (part of it).
31437 @subsubheading Example
31442 @subheading The @code{-file-symbol-file} Command
31443 @findex -file-symbol-file
31445 @subsubheading Synopsis
31448 -file-symbol-file @var{file}
31451 Read symbol table info from the specified @var{file} argument. When
31452 used without arguments, clears @value{GDBN}'s symbol table info. No output is
31453 produced, except for a completion notification.
31455 @subsubheading @value{GDBN} Command
31457 The corresponding @value{GDBN} command is @samp{symbol-file}.
31459 @subsubheading Example
31463 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31469 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31470 @node GDB/MI Memory Overlay Commands
31471 @section @sc{gdb/mi} Memory Overlay Commands
31473 The memory overlay commands are not implemented.
31475 @c @subheading -overlay-auto
31477 @c @subheading -overlay-list-mapping-state
31479 @c @subheading -overlay-list-overlays
31481 @c @subheading -overlay-map
31483 @c @subheading -overlay-off
31485 @c @subheading -overlay-on
31487 @c @subheading -overlay-unmap
31489 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31490 @node GDB/MI Signal Handling Commands
31491 @section @sc{gdb/mi} Signal Handling Commands
31493 Signal handling commands are not implemented.
31495 @c @subheading -signal-handle
31497 @c @subheading -signal-list-handle-actions
31499 @c @subheading -signal-list-signal-types
31503 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31504 @node GDB/MI Target Manipulation
31505 @section @sc{gdb/mi} Target Manipulation Commands
31508 @subheading The @code{-target-attach} Command
31509 @findex -target-attach
31511 @subsubheading Synopsis
31514 -target-attach @var{pid} | @var{gid} | @var{file}
31517 Attach to a process @var{pid} or a file @var{file} outside of
31518 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
31519 group, the id previously returned by
31520 @samp{-list-thread-groups --available} must be used.
31522 @subsubheading @value{GDBN} Command
31524 The corresponding @value{GDBN} command is @samp{attach}.
31526 @subsubheading Example
31530 =thread-created,id="1"
31531 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
31537 @subheading The @code{-target-compare-sections} Command
31538 @findex -target-compare-sections
31540 @subsubheading Synopsis
31543 -target-compare-sections [ @var{section} ]
31546 Compare data of section @var{section} on target to the exec file.
31547 Without the argument, all sections are compared.
31549 @subsubheading @value{GDBN} Command
31551 The @value{GDBN} equivalent is @samp{compare-sections}.
31553 @subsubheading Example
31558 @subheading The @code{-target-detach} Command
31559 @findex -target-detach
31561 @subsubheading Synopsis
31564 -target-detach [ @var{pid} | @var{gid} ]
31567 Detach from the remote target which normally resumes its execution.
31568 If either @var{pid} or @var{gid} is specified, detaches from either
31569 the specified process, or specified thread group. There's no output.
31571 @subsubheading @value{GDBN} Command
31573 The corresponding @value{GDBN} command is @samp{detach}.
31575 @subsubheading Example
31585 @subheading The @code{-target-disconnect} Command
31586 @findex -target-disconnect
31588 @subsubheading Synopsis
31594 Disconnect from the remote target. There's no output and the target is
31595 generally not resumed.
31597 @subsubheading @value{GDBN} Command
31599 The corresponding @value{GDBN} command is @samp{disconnect}.
31601 @subsubheading Example
31611 @subheading The @code{-target-download} Command
31612 @findex -target-download
31614 @subsubheading Synopsis
31620 Loads the executable onto the remote target.
31621 It prints out an update message every half second, which includes the fields:
31625 The name of the section.
31627 The size of what has been sent so far for that section.
31629 The size of the section.
31631 The total size of what was sent so far (the current and the previous sections).
31633 The size of the overall executable to download.
31637 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
31638 @sc{gdb/mi} Output Syntax}).
31640 In addition, it prints the name and size of the sections, as they are
31641 downloaded. These messages include the following fields:
31645 The name of the section.
31647 The size of the section.
31649 The size of the overall executable to download.
31653 At the end, a summary is printed.
31655 @subsubheading @value{GDBN} Command
31657 The corresponding @value{GDBN} command is @samp{load}.
31659 @subsubheading Example
31661 Note: each status message appears on a single line. Here the messages
31662 have been broken down so that they can fit onto a page.
31667 +download,@{section=".text",section-size="6668",total-size="9880"@}
31668 +download,@{section=".text",section-sent="512",section-size="6668",
31669 total-sent="512",total-size="9880"@}
31670 +download,@{section=".text",section-sent="1024",section-size="6668",
31671 total-sent="1024",total-size="9880"@}
31672 +download,@{section=".text",section-sent="1536",section-size="6668",
31673 total-sent="1536",total-size="9880"@}
31674 +download,@{section=".text",section-sent="2048",section-size="6668",
31675 total-sent="2048",total-size="9880"@}
31676 +download,@{section=".text",section-sent="2560",section-size="6668",
31677 total-sent="2560",total-size="9880"@}
31678 +download,@{section=".text",section-sent="3072",section-size="6668",
31679 total-sent="3072",total-size="9880"@}
31680 +download,@{section=".text",section-sent="3584",section-size="6668",
31681 total-sent="3584",total-size="9880"@}
31682 +download,@{section=".text",section-sent="4096",section-size="6668",
31683 total-sent="4096",total-size="9880"@}
31684 +download,@{section=".text",section-sent="4608",section-size="6668",
31685 total-sent="4608",total-size="9880"@}
31686 +download,@{section=".text",section-sent="5120",section-size="6668",
31687 total-sent="5120",total-size="9880"@}
31688 +download,@{section=".text",section-sent="5632",section-size="6668",
31689 total-sent="5632",total-size="9880"@}
31690 +download,@{section=".text",section-sent="6144",section-size="6668",
31691 total-sent="6144",total-size="9880"@}
31692 +download,@{section=".text",section-sent="6656",section-size="6668",
31693 total-sent="6656",total-size="9880"@}
31694 +download,@{section=".init",section-size="28",total-size="9880"@}
31695 +download,@{section=".fini",section-size="28",total-size="9880"@}
31696 +download,@{section=".data",section-size="3156",total-size="9880"@}
31697 +download,@{section=".data",section-sent="512",section-size="3156",
31698 total-sent="7236",total-size="9880"@}
31699 +download,@{section=".data",section-sent="1024",section-size="3156",
31700 total-sent="7748",total-size="9880"@}
31701 +download,@{section=".data",section-sent="1536",section-size="3156",
31702 total-sent="8260",total-size="9880"@}
31703 +download,@{section=".data",section-sent="2048",section-size="3156",
31704 total-sent="8772",total-size="9880"@}
31705 +download,@{section=".data",section-sent="2560",section-size="3156",
31706 total-sent="9284",total-size="9880"@}
31707 +download,@{section=".data",section-sent="3072",section-size="3156",
31708 total-sent="9796",total-size="9880"@}
31709 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
31716 @subheading The @code{-target-exec-status} Command
31717 @findex -target-exec-status
31719 @subsubheading Synopsis
31722 -target-exec-status
31725 Provide information on the state of the target (whether it is running or
31726 not, for instance).
31728 @subsubheading @value{GDBN} Command
31730 There's no equivalent @value{GDBN} command.
31732 @subsubheading Example
31736 @subheading The @code{-target-list-available-targets} Command
31737 @findex -target-list-available-targets
31739 @subsubheading Synopsis
31742 -target-list-available-targets
31745 List the possible targets to connect to.
31747 @subsubheading @value{GDBN} Command
31749 The corresponding @value{GDBN} command is @samp{help target}.
31751 @subsubheading Example
31755 @subheading The @code{-target-list-current-targets} Command
31756 @findex -target-list-current-targets
31758 @subsubheading Synopsis
31761 -target-list-current-targets
31764 Describe the current target.
31766 @subsubheading @value{GDBN} Command
31768 The corresponding information is printed by @samp{info file} (among
31771 @subsubheading Example
31775 @subheading The @code{-target-list-parameters} Command
31776 @findex -target-list-parameters
31778 @subsubheading Synopsis
31781 -target-list-parameters
31787 @subsubheading @value{GDBN} Command
31791 @subsubheading Example
31795 @subheading The @code{-target-select} Command
31796 @findex -target-select
31798 @subsubheading Synopsis
31801 -target-select @var{type} @var{parameters @dots{}}
31804 Connect @value{GDBN} to the remote target. This command takes two args:
31808 The type of target, for instance @samp{remote}, etc.
31809 @item @var{parameters}
31810 Device names, host names and the like. @xref{Target Commands, ,
31811 Commands for Managing Targets}, for more details.
31814 The output is a connection notification, followed by the address at
31815 which the target program is, in the following form:
31818 ^connected,addr="@var{address}",func="@var{function name}",
31819 args=[@var{arg list}]
31822 @subsubheading @value{GDBN} Command
31824 The corresponding @value{GDBN} command is @samp{target}.
31826 @subsubheading Example
31830 -target-select remote /dev/ttya
31831 ^connected,addr="0xfe00a300",func="??",args=[]
31835 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31836 @node GDB/MI File Transfer Commands
31837 @section @sc{gdb/mi} File Transfer Commands
31840 @subheading The @code{-target-file-put} Command
31841 @findex -target-file-put
31843 @subsubheading Synopsis
31846 -target-file-put @var{hostfile} @var{targetfile}
31849 Copy file @var{hostfile} from the host system (the machine running
31850 @value{GDBN}) to @var{targetfile} on the target system.
31852 @subsubheading @value{GDBN} Command
31854 The corresponding @value{GDBN} command is @samp{remote put}.
31856 @subsubheading Example
31860 -target-file-put localfile remotefile
31866 @subheading The @code{-target-file-get} Command
31867 @findex -target-file-get
31869 @subsubheading Synopsis
31872 -target-file-get @var{targetfile} @var{hostfile}
31875 Copy file @var{targetfile} from the target system to @var{hostfile}
31876 on the host system.
31878 @subsubheading @value{GDBN} Command
31880 The corresponding @value{GDBN} command is @samp{remote get}.
31882 @subsubheading Example
31886 -target-file-get remotefile localfile
31892 @subheading The @code{-target-file-delete} Command
31893 @findex -target-file-delete
31895 @subsubheading Synopsis
31898 -target-file-delete @var{targetfile}
31901 Delete @var{targetfile} from the target system.
31903 @subsubheading @value{GDBN} Command
31905 The corresponding @value{GDBN} command is @samp{remote delete}.
31907 @subsubheading Example
31911 -target-file-delete remotefile
31917 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31918 @node GDB/MI Ada Exceptions Commands
31919 @section Ada Exceptions @sc{gdb/mi} Commands
31921 @subheading The @code{-info-ada-exceptions} Command
31922 @findex -info-ada-exceptions
31924 @subsubheading Synopsis
31927 -info-ada-exceptions [ @var{regexp}]
31930 List all Ada exceptions defined within the program being debugged.
31931 With a regular expression @var{regexp}, only those exceptions whose
31932 names match @var{regexp} are listed.
31934 @subsubheading @value{GDBN} Command
31936 The corresponding @value{GDBN} command is @samp{info exceptions}.
31938 @subsubheading Result
31940 The result is a table of Ada exceptions. The following columns are
31941 defined for each exception:
31945 The name of the exception.
31948 The address of the exception.
31952 @subsubheading Example
31955 -info-ada-exceptions aint
31956 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
31957 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
31958 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
31959 body=[@{name="constraint_error",address="0x0000000000613da0"@},
31960 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
31963 @subheading Catching Ada Exceptions
31965 The commands describing how to ask @value{GDBN} to stop when a program
31966 raises an exception are described at @ref{Ada Exception GDB/MI
31967 Catchpoint Commands}.
31970 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31971 @node GDB/MI Support Commands
31972 @section @sc{gdb/mi} Support Commands
31974 Since new commands and features get regularly added to @sc{gdb/mi},
31975 some commands are available to help front-ends query the debugger
31976 about support for these capabilities. Similarly, it is also possible
31977 to query @value{GDBN} about target support of certain features.
31979 @subheading The @code{-info-gdb-mi-command} Command
31980 @cindex @code{-info-gdb-mi-command}
31981 @findex -info-gdb-mi-command
31983 @subsubheading Synopsis
31986 -info-gdb-mi-command @var{cmd_name}
31989 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
31991 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
31992 is technically not part of the command name (@pxref{GDB/MI Input
31993 Syntax}), and thus should be omitted in @var{cmd_name}. However,
31994 for ease of use, this command also accepts the form with the leading
31997 @subsubheading @value{GDBN} Command
31999 There is no corresponding @value{GDBN} command.
32001 @subsubheading Result
32003 The result is a tuple. There is currently only one field:
32007 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
32008 @code{"false"} otherwise.
32012 @subsubheading Example
32014 Here is an example where the @sc{gdb/mi} command does not exist:
32017 -info-gdb-mi-command unsupported-command
32018 ^done,command=@{exists="false"@}
32022 And here is an example where the @sc{gdb/mi} command is known
32026 -info-gdb-mi-command symbol-list-lines
32027 ^done,command=@{exists="true"@}
32030 @subheading The @code{-list-features} Command
32031 @findex -list-features
32032 @cindex supported @sc{gdb/mi} features, list
32034 Returns a list of particular features of the MI protocol that
32035 this version of gdb implements. A feature can be a command,
32036 or a new field in an output of some command, or even an
32037 important bugfix. While a frontend can sometimes detect presence
32038 of a feature at runtime, it is easier to perform detection at debugger
32041 The command returns a list of strings, with each string naming an
32042 available feature. Each returned string is just a name, it does not
32043 have any internal structure. The list of possible feature names
32049 (gdb) -list-features
32050 ^done,result=["feature1","feature2"]
32053 The current list of features is:
32056 @item frozen-varobjs
32057 Indicates support for the @code{-var-set-frozen} command, as well
32058 as possible presense of the @code{frozen} field in the output
32059 of @code{-varobj-create}.
32060 @item pending-breakpoints
32061 Indicates support for the @option{-f} option to the @code{-break-insert}
32064 Indicates Python scripting support, Python-based
32065 pretty-printing commands, and possible presence of the
32066 @samp{display_hint} field in the output of @code{-var-list-children}
32068 Indicates support for the @code{-thread-info} command.
32069 @item data-read-memory-bytes
32070 Indicates support for the @code{-data-read-memory-bytes} and the
32071 @code{-data-write-memory-bytes} commands.
32072 @item breakpoint-notifications
32073 Indicates that changes to breakpoints and breakpoints created via the
32074 CLI will be announced via async records.
32075 @item ada-task-info
32076 Indicates support for the @code{-ada-task-info} command.
32077 @item language-option
32078 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
32079 option (@pxref{Context management}).
32080 @item info-gdb-mi-command
32081 Indicates support for the @code{-info-gdb-mi-command} command.
32082 @item undefined-command-error-code
32083 Indicates support for the "undefined-command" error code in error result
32084 records, produced when trying to execute an undefined @sc{gdb/mi} command
32085 (@pxref{GDB/MI Result Records}).
32086 @item exec-run-start-option
32087 Indicates that the @code{-exec-run} command supports the @option{--start}
32088 option (@pxref{GDB/MI Program Execution}).
32091 @subheading The @code{-list-target-features} Command
32092 @findex -list-target-features
32094 Returns a list of particular features that are supported by the
32095 target. Those features affect the permitted MI commands, but
32096 unlike the features reported by the @code{-list-features} command, the
32097 features depend on which target GDB is using at the moment. Whenever
32098 a target can change, due to commands such as @code{-target-select},
32099 @code{-target-attach} or @code{-exec-run}, the list of target features
32100 may change, and the frontend should obtain it again.
32104 (gdb) -list-target-features
32105 ^done,result=["async"]
32108 The current list of features is:
32112 Indicates that the target is capable of asynchronous command
32113 execution, which means that @value{GDBN} will accept further commands
32114 while the target is running.
32117 Indicates that the target is capable of reverse execution.
32118 @xref{Reverse Execution}, for more information.
32122 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32123 @node GDB/MI Miscellaneous Commands
32124 @section Miscellaneous @sc{gdb/mi} Commands
32126 @c @subheading -gdb-complete
32128 @subheading The @code{-gdb-exit} Command
32131 @subsubheading Synopsis
32137 Exit @value{GDBN} immediately.
32139 @subsubheading @value{GDBN} Command
32141 Approximately corresponds to @samp{quit}.
32143 @subsubheading Example
32153 @subheading The @code{-exec-abort} Command
32154 @findex -exec-abort
32156 @subsubheading Synopsis
32162 Kill the inferior running program.
32164 @subsubheading @value{GDBN} Command
32166 The corresponding @value{GDBN} command is @samp{kill}.
32168 @subsubheading Example
32173 @subheading The @code{-gdb-set} Command
32176 @subsubheading Synopsis
32182 Set an internal @value{GDBN} variable.
32183 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
32185 @subsubheading @value{GDBN} Command
32187 The corresponding @value{GDBN} command is @samp{set}.
32189 @subsubheading Example
32199 @subheading The @code{-gdb-show} Command
32202 @subsubheading Synopsis
32208 Show the current value of a @value{GDBN} variable.
32210 @subsubheading @value{GDBN} Command
32212 The corresponding @value{GDBN} command is @samp{show}.
32214 @subsubheading Example
32223 @c @subheading -gdb-source
32226 @subheading The @code{-gdb-version} Command
32227 @findex -gdb-version
32229 @subsubheading Synopsis
32235 Show version information for @value{GDBN}. Used mostly in testing.
32237 @subsubheading @value{GDBN} Command
32239 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
32240 default shows this information when you start an interactive session.
32242 @subsubheading Example
32244 @c This example modifies the actual output from GDB to avoid overfull
32250 ~Copyright 2000 Free Software Foundation, Inc.
32251 ~GDB is free software, covered by the GNU General Public License, and
32252 ~you are welcome to change it and/or distribute copies of it under
32253 ~ certain conditions.
32254 ~Type "show copying" to see the conditions.
32255 ~There is absolutely no warranty for GDB. Type "show warranty" for
32257 ~This GDB was configured as
32258 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
32263 @subheading The @code{-list-thread-groups} Command
32264 @findex -list-thread-groups
32266 @subheading Synopsis
32269 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
32272 Lists thread groups (@pxref{Thread groups}). When a single thread
32273 group is passed as the argument, lists the children of that group.
32274 When several thread group are passed, lists information about those
32275 thread groups. Without any parameters, lists information about all
32276 top-level thread groups.
32278 Normally, thread groups that are being debugged are reported.
32279 With the @samp{--available} option, @value{GDBN} reports thread groups
32280 available on the target.
32282 The output of this command may have either a @samp{threads} result or
32283 a @samp{groups} result. The @samp{thread} result has a list of tuples
32284 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
32285 Information}). The @samp{groups} result has a list of tuples as value,
32286 each tuple describing a thread group. If top-level groups are
32287 requested (that is, no parameter is passed), or when several groups
32288 are passed, the output always has a @samp{groups} result. The format
32289 of the @samp{group} result is described below.
32291 To reduce the number of roundtrips it's possible to list thread groups
32292 together with their children, by passing the @samp{--recurse} option
32293 and the recursion depth. Presently, only recursion depth of 1 is
32294 permitted. If this option is present, then every reported thread group
32295 will also include its children, either as @samp{group} or
32296 @samp{threads} field.
32298 In general, any combination of option and parameters is permitted, with
32299 the following caveats:
32303 When a single thread group is passed, the output will typically
32304 be the @samp{threads} result. Because threads may not contain
32305 anything, the @samp{recurse} option will be ignored.
32308 When the @samp{--available} option is passed, limited information may
32309 be available. In particular, the list of threads of a process might
32310 be inaccessible. Further, specifying specific thread groups might
32311 not give any performance advantage over listing all thread groups.
32312 The frontend should assume that @samp{-list-thread-groups --available}
32313 is always an expensive operation and cache the results.
32317 The @samp{groups} result is a list of tuples, where each tuple may
32318 have the following fields:
32322 Identifier of the thread group. This field is always present.
32323 The identifier is an opaque string; frontends should not try to
32324 convert it to an integer, even though it might look like one.
32327 The type of the thread group. At present, only @samp{process} is a
32331 The target-specific process identifier. This field is only present
32332 for thread groups of type @samp{process} and only if the process exists.
32335 The exit code of this group's last exited thread, formatted in octal.
32336 This field is only present for thread groups of type @samp{process} and
32337 only if the process is not running.
32340 The number of children this thread group has. This field may be
32341 absent for an available thread group.
32344 This field has a list of tuples as value, each tuple describing a
32345 thread. It may be present if the @samp{--recurse} option is
32346 specified, and it's actually possible to obtain the threads.
32349 This field is a list of integers, each identifying a core that one
32350 thread of the group is running on. This field may be absent if
32351 such information is not available.
32354 The name of the executable file that corresponds to this thread group.
32355 The field is only present for thread groups of type @samp{process},
32356 and only if there is a corresponding executable file.
32360 @subheading Example
32364 -list-thread-groups
32365 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
32366 -list-thread-groups 17
32367 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
32368 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
32369 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
32370 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
32371 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
32372 -list-thread-groups --available
32373 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
32374 -list-thread-groups --available --recurse 1
32375 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
32376 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
32377 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
32378 -list-thread-groups --available --recurse 1 17 18
32379 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
32380 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
32381 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
32384 @subheading The @code{-info-os} Command
32387 @subsubheading Synopsis
32390 -info-os [ @var{type} ]
32393 If no argument is supplied, the command returns a table of available
32394 operating-system-specific information types. If one of these types is
32395 supplied as an argument @var{type}, then the command returns a table
32396 of data of that type.
32398 The types of information available depend on the target operating
32401 @subsubheading @value{GDBN} Command
32403 The corresponding @value{GDBN} command is @samp{info os}.
32405 @subsubheading Example
32407 When run on a @sc{gnu}/Linux system, the output will look something
32413 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
32414 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
32415 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
32416 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
32417 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
32419 item=@{col0="files",col1="Listing of all file descriptors",
32420 col2="File descriptors"@},
32421 item=@{col0="modules",col1="Listing of all loaded kernel modules",
32422 col2="Kernel modules"@},
32423 item=@{col0="msg",col1="Listing of all message queues",
32424 col2="Message queues"@},
32425 item=@{col0="processes",col1="Listing of all processes",
32426 col2="Processes"@},
32427 item=@{col0="procgroups",col1="Listing of all process groups",
32428 col2="Process groups"@},
32429 item=@{col0="semaphores",col1="Listing of all semaphores",
32430 col2="Semaphores"@},
32431 item=@{col0="shm",col1="Listing of all shared-memory regions",
32432 col2="Shared-memory regions"@},
32433 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
32435 item=@{col0="threads",col1="Listing of all threads",
32439 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
32440 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
32441 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
32442 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
32443 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
32444 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
32445 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
32446 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
32448 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
32449 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
32453 (Note that the MI output here includes a @code{"Title"} column that
32454 does not appear in command-line @code{info os}; this column is useful
32455 for MI clients that want to enumerate the types of data, such as in a
32456 popup menu, but is needless clutter on the command line, and
32457 @code{info os} omits it.)
32459 @subheading The @code{-add-inferior} Command
32460 @findex -add-inferior
32462 @subheading Synopsis
32468 Creates a new inferior (@pxref{Inferiors and Programs}). The created
32469 inferior is not associated with any executable. Such association may
32470 be established with the @samp{-file-exec-and-symbols} command
32471 (@pxref{GDB/MI File Commands}). The command response has a single
32472 field, @samp{inferior}, whose value is the identifier of the
32473 thread group corresponding to the new inferior.
32475 @subheading Example
32480 ^done,inferior="i3"
32483 @subheading The @code{-interpreter-exec} Command
32484 @findex -interpreter-exec
32486 @subheading Synopsis
32489 -interpreter-exec @var{interpreter} @var{command}
32491 @anchor{-interpreter-exec}
32493 Execute the specified @var{command} in the given @var{interpreter}.
32495 @subheading @value{GDBN} Command
32497 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
32499 @subheading Example
32503 -interpreter-exec console "break main"
32504 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
32505 &"During symbol reading, bad structure-type format.\n"
32506 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
32511 @subheading The @code{-inferior-tty-set} Command
32512 @findex -inferior-tty-set
32514 @subheading Synopsis
32517 -inferior-tty-set /dev/pts/1
32520 Set terminal for future runs of the program being debugged.
32522 @subheading @value{GDBN} Command
32524 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
32526 @subheading Example
32530 -inferior-tty-set /dev/pts/1
32535 @subheading The @code{-inferior-tty-show} Command
32536 @findex -inferior-tty-show
32538 @subheading Synopsis
32544 Show terminal for future runs of program being debugged.
32546 @subheading @value{GDBN} Command
32548 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
32550 @subheading Example
32554 -inferior-tty-set /dev/pts/1
32558 ^done,inferior_tty_terminal="/dev/pts/1"
32562 @subheading The @code{-enable-timings} Command
32563 @findex -enable-timings
32565 @subheading Synopsis
32568 -enable-timings [yes | no]
32571 Toggle the printing of the wallclock, user and system times for an MI
32572 command as a field in its output. This command is to help frontend
32573 developers optimize the performance of their code. No argument is
32574 equivalent to @samp{yes}.
32576 @subheading @value{GDBN} Command
32580 @subheading Example
32588 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
32589 addr="0x080484ed",func="main",file="myprog.c",
32590 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
32592 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
32600 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
32601 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
32602 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
32603 fullname="/home/nickrob/myprog.c",line="73"@}
32608 @chapter @value{GDBN} Annotations
32610 This chapter describes annotations in @value{GDBN}. Annotations were
32611 designed to interface @value{GDBN} to graphical user interfaces or other
32612 similar programs which want to interact with @value{GDBN} at a
32613 relatively high level.
32615 The annotation mechanism has largely been superseded by @sc{gdb/mi}
32619 This is Edition @value{EDITION}, @value{DATE}.
32623 * Annotations Overview:: What annotations are; the general syntax.
32624 * Server Prefix:: Issuing a command without affecting user state.
32625 * Prompting:: Annotations marking @value{GDBN}'s need for input.
32626 * Errors:: Annotations for error messages.
32627 * Invalidation:: Some annotations describe things now invalid.
32628 * Annotations for Running::
32629 Whether the program is running, how it stopped, etc.
32630 * Source Annotations:: Annotations describing source code.
32633 @node Annotations Overview
32634 @section What is an Annotation?
32635 @cindex annotations
32637 Annotations start with a newline character, two @samp{control-z}
32638 characters, and the name of the annotation. If there is no additional
32639 information associated with this annotation, the name of the annotation
32640 is followed immediately by a newline. If there is additional
32641 information, the name of the annotation is followed by a space, the
32642 additional information, and a newline. The additional information
32643 cannot contain newline characters.
32645 Any output not beginning with a newline and two @samp{control-z}
32646 characters denotes literal output from @value{GDBN}. Currently there is
32647 no need for @value{GDBN} to output a newline followed by two
32648 @samp{control-z} characters, but if there was such a need, the
32649 annotations could be extended with an @samp{escape} annotation which
32650 means those three characters as output.
32652 The annotation @var{level}, which is specified using the
32653 @option{--annotate} command line option (@pxref{Mode Options}), controls
32654 how much information @value{GDBN} prints together with its prompt,
32655 values of expressions, source lines, and other types of output. Level 0
32656 is for no annotations, level 1 is for use when @value{GDBN} is run as a
32657 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
32658 for programs that control @value{GDBN}, and level 2 annotations have
32659 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
32660 Interface, annotate, GDB's Obsolete Annotations}).
32663 @kindex set annotate
32664 @item set annotate @var{level}
32665 The @value{GDBN} command @code{set annotate} sets the level of
32666 annotations to the specified @var{level}.
32668 @item show annotate
32669 @kindex show annotate
32670 Show the current annotation level.
32673 This chapter describes level 3 annotations.
32675 A simple example of starting up @value{GDBN} with annotations is:
32678 $ @kbd{gdb --annotate=3}
32680 Copyright 2003 Free Software Foundation, Inc.
32681 GDB is free software, covered by the GNU General Public License,
32682 and you are welcome to change it and/or distribute copies of it
32683 under certain conditions.
32684 Type "show copying" to see the conditions.
32685 There is absolutely no warranty for GDB. Type "show warranty"
32687 This GDB was configured as "i386-pc-linux-gnu"
32698 Here @samp{quit} is input to @value{GDBN}; the rest is output from
32699 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
32700 denotes a @samp{control-z} character) are annotations; the rest is
32701 output from @value{GDBN}.
32703 @node Server Prefix
32704 @section The Server Prefix
32705 @cindex server prefix
32707 If you prefix a command with @samp{server } then it will not affect
32708 the command history, nor will it affect @value{GDBN}'s notion of which
32709 command to repeat if @key{RET} is pressed on a line by itself. This
32710 means that commands can be run behind a user's back by a front-end in
32711 a transparent manner.
32713 The @code{server } prefix does not affect the recording of values into
32714 the value history; to print a value without recording it into the
32715 value history, use the @code{output} command instead of the
32716 @code{print} command.
32718 Using this prefix also disables confirmation requests
32719 (@pxref{confirmation requests}).
32722 @section Annotation for @value{GDBN} Input
32724 @cindex annotations for prompts
32725 When @value{GDBN} prompts for input, it annotates this fact so it is possible
32726 to know when to send output, when the output from a given command is
32729 Different kinds of input each have a different @dfn{input type}. Each
32730 input type has three annotations: a @code{pre-} annotation, which
32731 denotes the beginning of any prompt which is being output, a plain
32732 annotation, which denotes the end of the prompt, and then a @code{post-}
32733 annotation which denotes the end of any echo which may (or may not) be
32734 associated with the input. For example, the @code{prompt} input type
32735 features the following annotations:
32743 The input types are
32746 @findex pre-prompt annotation
32747 @findex prompt annotation
32748 @findex post-prompt annotation
32750 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
32752 @findex pre-commands annotation
32753 @findex commands annotation
32754 @findex post-commands annotation
32756 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
32757 command. The annotations are repeated for each command which is input.
32759 @findex pre-overload-choice annotation
32760 @findex overload-choice annotation
32761 @findex post-overload-choice annotation
32762 @item overload-choice
32763 When @value{GDBN} wants the user to select between various overloaded functions.
32765 @findex pre-query annotation
32766 @findex query annotation
32767 @findex post-query annotation
32769 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
32771 @findex pre-prompt-for-continue annotation
32772 @findex prompt-for-continue annotation
32773 @findex post-prompt-for-continue annotation
32774 @item prompt-for-continue
32775 When @value{GDBN} is asking the user to press return to continue. Note: Don't
32776 expect this to work well; instead use @code{set height 0} to disable
32777 prompting. This is because the counting of lines is buggy in the
32778 presence of annotations.
32783 @cindex annotations for errors, warnings and interrupts
32785 @findex quit annotation
32790 This annotation occurs right before @value{GDBN} responds to an interrupt.
32792 @findex error annotation
32797 This annotation occurs right before @value{GDBN} responds to an error.
32799 Quit and error annotations indicate that any annotations which @value{GDBN} was
32800 in the middle of may end abruptly. For example, if a
32801 @code{value-history-begin} annotation is followed by a @code{error}, one
32802 cannot expect to receive the matching @code{value-history-end}. One
32803 cannot expect not to receive it either, however; an error annotation
32804 does not necessarily mean that @value{GDBN} is immediately returning all the way
32807 @findex error-begin annotation
32808 A quit or error annotation may be preceded by
32814 Any output between that and the quit or error annotation is the error
32817 Warning messages are not yet annotated.
32818 @c If we want to change that, need to fix warning(), type_error(),
32819 @c range_error(), and possibly other places.
32822 @section Invalidation Notices
32824 @cindex annotations for invalidation messages
32825 The following annotations say that certain pieces of state may have
32829 @findex frames-invalid annotation
32830 @item ^Z^Zframes-invalid
32832 The frames (for example, output from the @code{backtrace} command) may
32835 @findex breakpoints-invalid annotation
32836 @item ^Z^Zbreakpoints-invalid
32838 The breakpoints may have changed. For example, the user just added or
32839 deleted a breakpoint.
32842 @node Annotations for Running
32843 @section Running the Program
32844 @cindex annotations for running programs
32846 @findex starting annotation
32847 @findex stopping annotation
32848 When the program starts executing due to a @value{GDBN} command such as
32849 @code{step} or @code{continue},
32855 is output. When the program stops,
32861 is output. Before the @code{stopped} annotation, a variety of
32862 annotations describe how the program stopped.
32865 @findex exited annotation
32866 @item ^Z^Zexited @var{exit-status}
32867 The program exited, and @var{exit-status} is the exit status (zero for
32868 successful exit, otherwise nonzero).
32870 @findex signalled annotation
32871 @findex signal-name annotation
32872 @findex signal-name-end annotation
32873 @findex signal-string annotation
32874 @findex signal-string-end annotation
32875 @item ^Z^Zsignalled
32876 The program exited with a signal. After the @code{^Z^Zsignalled}, the
32877 annotation continues:
32883 ^Z^Zsignal-name-end
32887 ^Z^Zsignal-string-end
32892 where @var{name} is the name of the signal, such as @code{SIGILL} or
32893 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
32894 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
32895 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
32896 user's benefit and have no particular format.
32898 @findex signal annotation
32900 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
32901 just saying that the program received the signal, not that it was
32902 terminated with it.
32904 @findex breakpoint annotation
32905 @item ^Z^Zbreakpoint @var{number}
32906 The program hit breakpoint number @var{number}.
32908 @findex watchpoint annotation
32909 @item ^Z^Zwatchpoint @var{number}
32910 The program hit watchpoint number @var{number}.
32913 @node Source Annotations
32914 @section Displaying Source
32915 @cindex annotations for source display
32917 @findex source annotation
32918 The following annotation is used instead of displaying source code:
32921 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
32924 where @var{filename} is an absolute file name indicating which source
32925 file, @var{line} is the line number within that file (where 1 is the
32926 first line in the file), @var{character} is the character position
32927 within the file (where 0 is the first character in the file) (for most
32928 debug formats this will necessarily point to the beginning of a line),
32929 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
32930 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
32931 @var{addr} is the address in the target program associated with the
32932 source which is being displayed. The @var{addr} is in the form @samp{0x}
32933 followed by one or more lowercase hex digits (note that this does not
32934 depend on the language).
32936 @node JIT Interface
32937 @chapter JIT Compilation Interface
32938 @cindex just-in-time compilation
32939 @cindex JIT compilation interface
32941 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
32942 interface. A JIT compiler is a program or library that generates native
32943 executable code at runtime and executes it, usually in order to achieve good
32944 performance while maintaining platform independence.
32946 Programs that use JIT compilation are normally difficult to debug because
32947 portions of their code are generated at runtime, instead of being loaded from
32948 object files, which is where @value{GDBN} normally finds the program's symbols
32949 and debug information. In order to debug programs that use JIT compilation,
32950 @value{GDBN} has an interface that allows the program to register in-memory
32951 symbol files with @value{GDBN} at runtime.
32953 If you are using @value{GDBN} to debug a program that uses this interface, then
32954 it should work transparently so long as you have not stripped the binary. If
32955 you are developing a JIT compiler, then the interface is documented in the rest
32956 of this chapter. At this time, the only known client of this interface is the
32959 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
32960 JIT compiler communicates with @value{GDBN} by writing data into a global
32961 variable and calling a fuction at a well-known symbol. When @value{GDBN}
32962 attaches, it reads a linked list of symbol files from the global variable to
32963 find existing code, and puts a breakpoint in the function so that it can find
32964 out about additional code.
32967 * Declarations:: Relevant C struct declarations
32968 * Registering Code:: Steps to register code
32969 * Unregistering Code:: Steps to unregister code
32970 * Custom Debug Info:: Emit debug information in a custom format
32974 @section JIT Declarations
32976 These are the relevant struct declarations that a C program should include to
32977 implement the interface:
32987 struct jit_code_entry
32989 struct jit_code_entry *next_entry;
32990 struct jit_code_entry *prev_entry;
32991 const char *symfile_addr;
32992 uint64_t symfile_size;
32995 struct jit_descriptor
32998 /* This type should be jit_actions_t, but we use uint32_t
32999 to be explicit about the bitwidth. */
33000 uint32_t action_flag;
33001 struct jit_code_entry *relevant_entry;
33002 struct jit_code_entry *first_entry;
33005 /* GDB puts a breakpoint in this function. */
33006 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
33008 /* Make sure to specify the version statically, because the
33009 debugger may check the version before we can set it. */
33010 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
33013 If the JIT is multi-threaded, then it is important that the JIT synchronize any
33014 modifications to this global data properly, which can easily be done by putting
33015 a global mutex around modifications to these structures.
33017 @node Registering Code
33018 @section Registering Code
33020 To register code with @value{GDBN}, the JIT should follow this protocol:
33024 Generate an object file in memory with symbols and other desired debug
33025 information. The file must include the virtual addresses of the sections.
33028 Create a code entry for the file, which gives the start and size of the symbol
33032 Add it to the linked list in the JIT descriptor.
33035 Point the relevant_entry field of the descriptor at the entry.
33038 Set @code{action_flag} to @code{JIT_REGISTER} and call
33039 @code{__jit_debug_register_code}.
33042 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
33043 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
33044 new code. However, the linked list must still be maintained in order to allow
33045 @value{GDBN} to attach to a running process and still find the symbol files.
33047 @node Unregistering Code
33048 @section Unregistering Code
33050 If code is freed, then the JIT should use the following protocol:
33054 Remove the code entry corresponding to the code from the linked list.
33057 Point the @code{relevant_entry} field of the descriptor at the code entry.
33060 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
33061 @code{__jit_debug_register_code}.
33064 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
33065 and the JIT will leak the memory used for the associated symbol files.
33067 @node Custom Debug Info
33068 @section Custom Debug Info
33069 @cindex custom JIT debug info
33070 @cindex JIT debug info reader
33072 Generating debug information in platform-native file formats (like ELF
33073 or COFF) may be an overkill for JIT compilers; especially if all the
33074 debug info is used for is displaying a meaningful backtrace. The
33075 issue can be resolved by having the JIT writers decide on a debug info
33076 format and also provide a reader that parses the debug info generated
33077 by the JIT compiler. This section gives a brief overview on writing
33078 such a parser. More specific details can be found in the source file
33079 @file{gdb/jit-reader.in}, which is also installed as a header at
33080 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
33082 The reader is implemented as a shared object (so this functionality is
33083 not available on platforms which don't allow loading shared objects at
33084 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
33085 @code{jit-reader-unload} are provided, to be used to load and unload
33086 the readers from a preconfigured directory. Once loaded, the shared
33087 object is used the parse the debug information emitted by the JIT
33091 * Using JIT Debug Info Readers:: How to use supplied readers correctly
33092 * Writing JIT Debug Info Readers:: Creating a debug-info reader
33095 @node Using JIT Debug Info Readers
33096 @subsection Using JIT Debug Info Readers
33097 @kindex jit-reader-load
33098 @kindex jit-reader-unload
33100 Readers can be loaded and unloaded using the @code{jit-reader-load}
33101 and @code{jit-reader-unload} commands.
33104 @item jit-reader-load @var{reader}
33105 Load the JIT reader named @var{reader}, which is a shared
33106 object specified as either an absolute or a relative file name. In
33107 the latter case, @value{GDBN} will try to load the reader from a
33108 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
33109 system (here @var{libdir} is the system library directory, often
33110 @file{/usr/local/lib}).
33112 Only one reader can be active at a time; trying to load a second
33113 reader when one is already loaded will result in @value{GDBN}
33114 reporting an error. A new JIT reader can be loaded by first unloading
33115 the current one using @code{jit-reader-unload} and then invoking
33116 @code{jit-reader-load}.
33118 @item jit-reader-unload
33119 Unload the currently loaded JIT reader.
33123 @node Writing JIT Debug Info Readers
33124 @subsection Writing JIT Debug Info Readers
33125 @cindex writing JIT debug info readers
33127 As mentioned, a reader is essentially a shared object conforming to a
33128 certain ABI. This ABI is described in @file{jit-reader.h}.
33130 @file{jit-reader.h} defines the structures, macros and functions
33131 required to write a reader. It is installed (along with
33132 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
33133 the system include directory.
33135 Readers need to be released under a GPL compatible license. A reader
33136 can be declared as released under such a license by placing the macro
33137 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
33139 The entry point for readers is the symbol @code{gdb_init_reader},
33140 which is expected to be a function with the prototype
33142 @findex gdb_init_reader
33144 extern struct gdb_reader_funcs *gdb_init_reader (void);
33147 @cindex @code{struct gdb_reader_funcs}
33149 @code{struct gdb_reader_funcs} contains a set of pointers to callback
33150 functions. These functions are executed to read the debug info
33151 generated by the JIT compiler (@code{read}), to unwind stack frames
33152 (@code{unwind}) and to create canonical frame IDs
33153 (@code{get_Frame_id}). It also has a callback that is called when the
33154 reader is being unloaded (@code{destroy}). The struct looks like this
33157 struct gdb_reader_funcs
33159 /* Must be set to GDB_READER_INTERFACE_VERSION. */
33160 int reader_version;
33162 /* For use by the reader. */
33165 gdb_read_debug_info *read;
33166 gdb_unwind_frame *unwind;
33167 gdb_get_frame_id *get_frame_id;
33168 gdb_destroy_reader *destroy;
33172 @cindex @code{struct gdb_symbol_callbacks}
33173 @cindex @code{struct gdb_unwind_callbacks}
33175 The callbacks are provided with another set of callbacks by
33176 @value{GDBN} to do their job. For @code{read}, these callbacks are
33177 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
33178 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
33179 @code{struct gdb_symbol_callbacks} has callbacks to create new object
33180 files and new symbol tables inside those object files. @code{struct
33181 gdb_unwind_callbacks} has callbacks to read registers off the current
33182 frame and to write out the values of the registers in the previous
33183 frame. Both have a callback (@code{target_read}) to read bytes off the
33184 target's address space.
33186 @node In-Process Agent
33187 @chapter In-Process Agent
33188 @cindex debugging agent
33189 The traditional debugging model is conceptually low-speed, but works fine,
33190 because most bugs can be reproduced in debugging-mode execution. However,
33191 as multi-core or many-core processors are becoming mainstream, and
33192 multi-threaded programs become more and more popular, there should be more
33193 and more bugs that only manifest themselves at normal-mode execution, for
33194 example, thread races, because debugger's interference with the program's
33195 timing may conceal the bugs. On the other hand, in some applications,
33196 it is not feasible for the debugger to interrupt the program's execution
33197 long enough for the developer to learn anything helpful about its behavior.
33198 If the program's correctness depends on its real-time behavior, delays
33199 introduced by a debugger might cause the program to fail, even when the
33200 code itself is correct. It is useful to be able to observe the program's
33201 behavior without interrupting it.
33203 Therefore, traditional debugging model is too intrusive to reproduce
33204 some bugs. In order to reduce the interference with the program, we can
33205 reduce the number of operations performed by debugger. The
33206 @dfn{In-Process Agent}, a shared library, is running within the same
33207 process with inferior, and is able to perform some debugging operations
33208 itself. As a result, debugger is only involved when necessary, and
33209 performance of debugging can be improved accordingly. Note that
33210 interference with program can be reduced but can't be removed completely,
33211 because the in-process agent will still stop or slow down the program.
33213 The in-process agent can interpret and execute Agent Expressions
33214 (@pxref{Agent Expressions}) during performing debugging operations. The
33215 agent expressions can be used for different purposes, such as collecting
33216 data in tracepoints, and condition evaluation in breakpoints.
33218 @anchor{Control Agent}
33219 You can control whether the in-process agent is used as an aid for
33220 debugging with the following commands:
33223 @kindex set agent on
33225 Causes the in-process agent to perform some operations on behalf of the
33226 debugger. Just which operations requested by the user will be done
33227 by the in-process agent depends on the its capabilities. For example,
33228 if you request to evaluate breakpoint conditions in the in-process agent,
33229 and the in-process agent has such capability as well, then breakpoint
33230 conditions will be evaluated in the in-process agent.
33232 @kindex set agent off
33233 @item set agent off
33234 Disables execution of debugging operations by the in-process agent. All
33235 of the operations will be performed by @value{GDBN}.
33239 Display the current setting of execution of debugging operations by
33240 the in-process agent.
33244 * In-Process Agent Protocol::
33247 @node In-Process Agent Protocol
33248 @section In-Process Agent Protocol
33249 @cindex in-process agent protocol
33251 The in-process agent is able to communicate with both @value{GDBN} and
33252 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
33253 used for communications between @value{GDBN} or GDBserver and the IPA.
33254 In general, @value{GDBN} or GDBserver sends commands
33255 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
33256 in-process agent replies back with the return result of the command, or
33257 some other information. The data sent to in-process agent is composed
33258 of primitive data types, such as 4-byte or 8-byte type, and composite
33259 types, which are called objects (@pxref{IPA Protocol Objects}).
33262 * IPA Protocol Objects::
33263 * IPA Protocol Commands::
33266 @node IPA Protocol Objects
33267 @subsection IPA Protocol Objects
33268 @cindex ipa protocol objects
33270 The commands sent to and results received from agent may contain some
33271 complex data types called @dfn{objects}.
33273 The in-process agent is running on the same machine with @value{GDBN}
33274 or GDBserver, so it doesn't have to handle as much differences between
33275 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
33276 However, there are still some differences of two ends in two processes:
33280 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
33281 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
33283 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
33284 GDBserver is compiled with one, and in-process agent is compiled with
33288 Here are the IPA Protocol Objects:
33292 agent expression object. It represents an agent expression
33293 (@pxref{Agent Expressions}).
33294 @anchor{agent expression object}
33296 tracepoint action object. It represents a tracepoint action
33297 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
33298 memory, static trace data and to evaluate expression.
33299 @anchor{tracepoint action object}
33301 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
33302 @anchor{tracepoint object}
33306 The following table describes important attributes of each IPA protocol
33309 @multitable @columnfractions .30 .20 .50
33310 @headitem Name @tab Size @tab Description
33311 @item @emph{agent expression object} @tab @tab
33312 @item length @tab 4 @tab length of bytes code
33313 @item byte code @tab @var{length} @tab contents of byte code
33314 @item @emph{tracepoint action for collecting memory} @tab @tab
33315 @item 'M' @tab 1 @tab type of tracepoint action
33316 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
33317 address of the lowest byte to collect, otherwise @var{addr} is the offset
33318 of @var{basereg} for memory collecting.
33319 @item len @tab 8 @tab length of memory for collecting
33320 @item basereg @tab 4 @tab the register number containing the starting
33321 memory address for collecting.
33322 @item @emph{tracepoint action for collecting registers} @tab @tab
33323 @item 'R' @tab 1 @tab type of tracepoint action
33324 @item @emph{tracepoint action for collecting static trace data} @tab @tab
33325 @item 'L' @tab 1 @tab type of tracepoint action
33326 @item @emph{tracepoint action for expression evaluation} @tab @tab
33327 @item 'X' @tab 1 @tab type of tracepoint action
33328 @item agent expression @tab length of @tab @ref{agent expression object}
33329 @item @emph{tracepoint object} @tab @tab
33330 @item number @tab 4 @tab number of tracepoint
33331 @item address @tab 8 @tab address of tracepoint inserted on
33332 @item type @tab 4 @tab type of tracepoint
33333 @item enabled @tab 1 @tab enable or disable of tracepoint
33334 @item step_count @tab 8 @tab step
33335 @item pass_count @tab 8 @tab pass
33336 @item numactions @tab 4 @tab number of tracepoint actions
33337 @item hit count @tab 8 @tab hit count
33338 @item trace frame usage @tab 8 @tab trace frame usage
33339 @item compiled_cond @tab 8 @tab compiled condition
33340 @item orig_size @tab 8 @tab orig size
33341 @item condition @tab 4 if condition is NULL otherwise length of
33342 @ref{agent expression object}
33343 @tab zero if condition is NULL, otherwise is
33344 @ref{agent expression object}
33345 @item actions @tab variable
33346 @tab numactions number of @ref{tracepoint action object}
33349 @node IPA Protocol Commands
33350 @subsection IPA Protocol Commands
33351 @cindex ipa protocol commands
33353 The spaces in each command are delimiters to ease reading this commands
33354 specification. They don't exist in real commands.
33358 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
33359 Installs a new fast tracepoint described by @var{tracepoint_object}
33360 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
33361 head of @dfn{jumppad}, which is used to jump to data collection routine
33366 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
33367 @var{target_address} is address of tracepoint in the inferior.
33368 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
33369 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
33370 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
33371 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
33378 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
33379 is about to kill inferiors.
33387 @item probe_marker_at:@var{address}
33388 Asks in-process agent to probe the marker at @var{address}.
33395 @item unprobe_marker_at:@var{address}
33396 Asks in-process agent to unprobe the marker at @var{address}.
33400 @chapter Reporting Bugs in @value{GDBN}
33401 @cindex bugs in @value{GDBN}
33402 @cindex reporting bugs in @value{GDBN}
33404 Your bug reports play an essential role in making @value{GDBN} reliable.
33406 Reporting a bug may help you by bringing a solution to your problem, or it
33407 may not. But in any case the principal function of a bug report is to help
33408 the entire community by making the next version of @value{GDBN} work better. Bug
33409 reports are your contribution to the maintenance of @value{GDBN}.
33411 In order for a bug report to serve its purpose, you must include the
33412 information that enables us to fix the bug.
33415 * Bug Criteria:: Have you found a bug?
33416 * Bug Reporting:: How to report bugs
33420 @section Have You Found a Bug?
33421 @cindex bug criteria
33423 If you are not sure whether you have found a bug, here are some guidelines:
33426 @cindex fatal signal
33427 @cindex debugger crash
33428 @cindex crash of debugger
33430 If the debugger gets a fatal signal, for any input whatever, that is a
33431 @value{GDBN} bug. Reliable debuggers never crash.
33433 @cindex error on valid input
33435 If @value{GDBN} produces an error message for valid input, that is a
33436 bug. (Note that if you're cross debugging, the problem may also be
33437 somewhere in the connection to the target.)
33439 @cindex invalid input
33441 If @value{GDBN} does not produce an error message for invalid input,
33442 that is a bug. However, you should note that your idea of
33443 ``invalid input'' might be our idea of ``an extension'' or ``support
33444 for traditional practice''.
33447 If you are an experienced user of debugging tools, your suggestions
33448 for improvement of @value{GDBN} are welcome in any case.
33451 @node Bug Reporting
33452 @section How to Report Bugs
33453 @cindex bug reports
33454 @cindex @value{GDBN} bugs, reporting
33456 A number of companies and individuals offer support for @sc{gnu} products.
33457 If you obtained @value{GDBN} from a support organization, we recommend you
33458 contact that organization first.
33460 You can find contact information for many support companies and
33461 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
33463 @c should add a web page ref...
33466 @ifset BUGURL_DEFAULT
33467 In any event, we also recommend that you submit bug reports for
33468 @value{GDBN}. The preferred method is to submit them directly using
33469 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
33470 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
33473 @strong{Do not send bug reports to @samp{info-gdb}, or to
33474 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
33475 not want to receive bug reports. Those that do have arranged to receive
33478 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
33479 serves as a repeater. The mailing list and the newsgroup carry exactly
33480 the same messages. Often people think of posting bug reports to the
33481 newsgroup instead of mailing them. This appears to work, but it has one
33482 problem which can be crucial: a newsgroup posting often lacks a mail
33483 path back to the sender. Thus, if we need to ask for more information,
33484 we may be unable to reach you. For this reason, it is better to send
33485 bug reports to the mailing list.
33487 @ifclear BUGURL_DEFAULT
33488 In any event, we also recommend that you submit bug reports for
33489 @value{GDBN} to @value{BUGURL}.
33493 The fundamental principle of reporting bugs usefully is this:
33494 @strong{report all the facts}. If you are not sure whether to state a
33495 fact or leave it out, state it!
33497 Often people omit facts because they think they know what causes the
33498 problem and assume that some details do not matter. Thus, you might
33499 assume that the name of the variable you use in an example does not matter.
33500 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
33501 stray memory reference which happens to fetch from the location where that
33502 name is stored in memory; perhaps, if the name were different, the contents
33503 of that location would fool the debugger into doing the right thing despite
33504 the bug. Play it safe and give a specific, complete example. That is the
33505 easiest thing for you to do, and the most helpful.
33507 Keep in mind that the purpose of a bug report is to enable us to fix the
33508 bug. It may be that the bug has been reported previously, but neither
33509 you nor we can know that unless your bug report is complete and
33512 Sometimes people give a few sketchy facts and ask, ``Does this ring a
33513 bell?'' Those bug reports are useless, and we urge everyone to
33514 @emph{refuse to respond to them} except to chide the sender to report
33517 To enable us to fix the bug, you should include all these things:
33521 The version of @value{GDBN}. @value{GDBN} announces it if you start
33522 with no arguments; you can also print it at any time using @code{show
33525 Without this, we will not know whether there is any point in looking for
33526 the bug in the current version of @value{GDBN}.
33529 The type of machine you are using, and the operating system name and
33533 The details of the @value{GDBN} build-time configuration.
33534 @value{GDBN} shows these details if you invoke it with the
33535 @option{--configuration} command-line option, or if you type
33536 @code{show configuration} at @value{GDBN}'s prompt.
33539 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
33540 ``@value{GCC}--2.8.1''.
33543 What compiler (and its version) was used to compile the program you are
33544 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
33545 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
33546 to get this information; for other compilers, see the documentation for
33550 The command arguments you gave the compiler to compile your example and
33551 observe the bug. For example, did you use @samp{-O}? To guarantee
33552 you will not omit something important, list them all. A copy of the
33553 Makefile (or the output from make) is sufficient.
33555 If we were to try to guess the arguments, we would probably guess wrong
33556 and then we might not encounter the bug.
33559 A complete input script, and all necessary source files, that will
33563 A description of what behavior you observe that you believe is
33564 incorrect. For example, ``It gets a fatal signal.''
33566 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
33567 will certainly notice it. But if the bug is incorrect output, we might
33568 not notice unless it is glaringly wrong. You might as well not give us
33569 a chance to make a mistake.
33571 Even if the problem you experience is a fatal signal, you should still
33572 say so explicitly. Suppose something strange is going on, such as, your
33573 copy of @value{GDBN} is out of synch, or you have encountered a bug in
33574 the C library on your system. (This has happened!) Your copy might
33575 crash and ours would not. If you told us to expect a crash, then when
33576 ours fails to crash, we would know that the bug was not happening for
33577 us. If you had not told us to expect a crash, then we would not be able
33578 to draw any conclusion from our observations.
33581 @cindex recording a session script
33582 To collect all this information, you can use a session recording program
33583 such as @command{script}, which is available on many Unix systems.
33584 Just run your @value{GDBN} session inside @command{script} and then
33585 include the @file{typescript} file with your bug report.
33587 Another way to record a @value{GDBN} session is to run @value{GDBN}
33588 inside Emacs and then save the entire buffer to a file.
33591 If you wish to suggest changes to the @value{GDBN} source, send us context
33592 diffs. If you even discuss something in the @value{GDBN} source, refer to
33593 it by context, not by line number.
33595 The line numbers in our development sources will not match those in your
33596 sources. Your line numbers would convey no useful information to us.
33600 Here are some things that are not necessary:
33604 A description of the envelope of the bug.
33606 Often people who encounter a bug spend a lot of time investigating
33607 which changes to the input file will make the bug go away and which
33608 changes will not affect it.
33610 This is often time consuming and not very useful, because the way we
33611 will find the bug is by running a single example under the debugger
33612 with breakpoints, not by pure deduction from a series of examples.
33613 We recommend that you save your time for something else.
33615 Of course, if you can find a simpler example to report @emph{instead}
33616 of the original one, that is a convenience for us. Errors in the
33617 output will be easier to spot, running under the debugger will take
33618 less time, and so on.
33620 However, simplification is not vital; if you do not want to do this,
33621 report the bug anyway and send us the entire test case you used.
33624 A patch for the bug.
33626 A patch for the bug does help us if it is a good one. But do not omit
33627 the necessary information, such as the test case, on the assumption that
33628 a patch is all we need. We might see problems with your patch and decide
33629 to fix the problem another way, or we might not understand it at all.
33631 Sometimes with a program as complicated as @value{GDBN} it is very hard to
33632 construct an example that will make the program follow a certain path
33633 through the code. If you do not send us the example, we will not be able
33634 to construct one, so we will not be able to verify that the bug is fixed.
33636 And if we cannot understand what bug you are trying to fix, or why your
33637 patch should be an improvement, we will not install it. A test case will
33638 help us to understand.
33641 A guess about what the bug is or what it depends on.
33643 Such guesses are usually wrong. Even we cannot guess right about such
33644 things without first using the debugger to find the facts.
33647 @c The readline documentation is distributed with the readline code
33648 @c and consists of the two following files:
33651 @c Use -I with makeinfo to point to the appropriate directory,
33652 @c environment var TEXINPUTS with TeX.
33653 @ifclear SYSTEM_READLINE
33654 @include rluser.texi
33655 @include hsuser.texi
33659 @appendix In Memoriam
33661 The @value{GDBN} project mourns the loss of the following long-time
33666 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
33667 to Free Software in general. Outside of @value{GDBN}, he was known in
33668 the Amiga world for his series of Fish Disks, and the GeekGadget project.
33670 @item Michael Snyder
33671 Michael was one of the Global Maintainers of the @value{GDBN} project,
33672 with contributions recorded as early as 1996, until 2011. In addition
33673 to his day to day participation, he was a large driving force behind
33674 adding Reverse Debugging to @value{GDBN}.
33677 Beyond their technical contributions to the project, they were also
33678 enjoyable members of the Free Software Community. We will miss them.
33680 @node Formatting Documentation
33681 @appendix Formatting Documentation
33683 @cindex @value{GDBN} reference card
33684 @cindex reference card
33685 The @value{GDBN} 4 release includes an already-formatted reference card, ready
33686 for printing with PostScript or Ghostscript, in the @file{gdb}
33687 subdirectory of the main source directory@footnote{In
33688 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
33689 release.}. If you can use PostScript or Ghostscript with your printer,
33690 you can print the reference card immediately with @file{refcard.ps}.
33692 The release also includes the source for the reference card. You
33693 can format it, using @TeX{}, by typing:
33699 The @value{GDBN} reference card is designed to print in @dfn{landscape}
33700 mode on US ``letter'' size paper;
33701 that is, on a sheet 11 inches wide by 8.5 inches
33702 high. You will need to specify this form of printing as an option to
33703 your @sc{dvi} output program.
33705 @cindex documentation
33707 All the documentation for @value{GDBN} comes as part of the machine-readable
33708 distribution. The documentation is written in Texinfo format, which is
33709 a documentation system that uses a single source file to produce both
33710 on-line information and a printed manual. You can use one of the Info
33711 formatting commands to create the on-line version of the documentation
33712 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
33714 @value{GDBN} includes an already formatted copy of the on-line Info
33715 version of this manual in the @file{gdb} subdirectory. The main Info
33716 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
33717 subordinate files matching @samp{gdb.info*} in the same directory. If
33718 necessary, you can print out these files, or read them with any editor;
33719 but they are easier to read using the @code{info} subsystem in @sc{gnu}
33720 Emacs or the standalone @code{info} program, available as part of the
33721 @sc{gnu} Texinfo distribution.
33723 If you want to format these Info files yourself, you need one of the
33724 Info formatting programs, such as @code{texinfo-format-buffer} or
33727 If you have @code{makeinfo} installed, and are in the top level
33728 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
33729 version @value{GDBVN}), you can make the Info file by typing:
33736 If you want to typeset and print copies of this manual, you need @TeX{},
33737 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
33738 Texinfo definitions file.
33740 @TeX{} is a typesetting program; it does not print files directly, but
33741 produces output files called @sc{dvi} files. To print a typeset
33742 document, you need a program to print @sc{dvi} files. If your system
33743 has @TeX{} installed, chances are it has such a program. The precise
33744 command to use depends on your system; @kbd{lpr -d} is common; another
33745 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
33746 require a file name without any extension or a @samp{.dvi} extension.
33748 @TeX{} also requires a macro definitions file called
33749 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
33750 written in Texinfo format. On its own, @TeX{} cannot either read or
33751 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
33752 and is located in the @file{gdb-@var{version-number}/texinfo}
33755 If you have @TeX{} and a @sc{dvi} printer program installed, you can
33756 typeset and print this manual. First switch to the @file{gdb}
33757 subdirectory of the main source directory (for example, to
33758 @file{gdb-@value{GDBVN}/gdb}) and type:
33764 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
33766 @node Installing GDB
33767 @appendix Installing @value{GDBN}
33768 @cindex installation
33771 * Requirements:: Requirements for building @value{GDBN}
33772 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
33773 * Separate Objdir:: Compiling @value{GDBN} in another directory
33774 * Config Names:: Specifying names for hosts and targets
33775 * Configure Options:: Summary of options for configure
33776 * System-wide configuration:: Having a system-wide init file
33780 @section Requirements for Building @value{GDBN}
33781 @cindex building @value{GDBN}, requirements for
33783 Building @value{GDBN} requires various tools and packages to be available.
33784 Other packages will be used only if they are found.
33786 @heading Tools/Packages Necessary for Building @value{GDBN}
33788 @item ISO C90 compiler
33789 @value{GDBN} is written in ISO C90. It should be buildable with any
33790 working C90 compiler, e.g.@: GCC.
33794 @heading Tools/Packages Optional for Building @value{GDBN}
33798 @value{GDBN} can use the Expat XML parsing library. This library may be
33799 included with your operating system distribution; if it is not, you
33800 can get the latest version from @url{http://expat.sourceforge.net}.
33801 The @file{configure} script will search for this library in several
33802 standard locations; if it is installed in an unusual path, you can
33803 use the @option{--with-libexpat-prefix} option to specify its location.
33809 Remote protocol memory maps (@pxref{Memory Map Format})
33811 Target descriptions (@pxref{Target Descriptions})
33813 Remote shared library lists (@xref{Library List Format},
33814 or alternatively @pxref{Library List Format for SVR4 Targets})
33816 MS-Windows shared libraries (@pxref{Shared Libraries})
33818 Traceframe info (@pxref{Traceframe Info Format})
33820 Branch trace (@pxref{Branch Trace Format},
33821 @pxref{Branch Trace Configuration Format})
33825 @cindex compressed debug sections
33826 @value{GDBN} will use the @samp{zlib} library, if available, to read
33827 compressed debug sections. Some linkers, such as GNU gold, are capable
33828 of producing binaries with compressed debug sections. If @value{GDBN}
33829 is compiled with @samp{zlib}, it will be able to read the debug
33830 information in such binaries.
33832 The @samp{zlib} library is likely included with your operating system
33833 distribution; if it is not, you can get the latest version from
33834 @url{http://zlib.net}.
33837 @value{GDBN}'s features related to character sets (@pxref{Character
33838 Sets}) require a functioning @code{iconv} implementation. If you are
33839 on a GNU system, then this is provided by the GNU C Library. Some
33840 other systems also provide a working @code{iconv}.
33842 If @value{GDBN} is using the @code{iconv} program which is installed
33843 in a non-standard place, you will need to tell @value{GDBN} where to find it.
33844 This is done with @option{--with-iconv-bin} which specifies the
33845 directory that contains the @code{iconv} program.
33847 On systems without @code{iconv}, you can install GNU Libiconv. If you
33848 have previously installed Libiconv, you can use the
33849 @option{--with-libiconv-prefix} option to configure.
33851 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
33852 arrange to build Libiconv if a directory named @file{libiconv} appears
33853 in the top-most source directory. If Libiconv is built this way, and
33854 if the operating system does not provide a suitable @code{iconv}
33855 implementation, then the just-built library will automatically be used
33856 by @value{GDBN}. One easy way to set this up is to download GNU
33857 Libiconv, unpack it, and then rename the directory holding the
33858 Libiconv source code to @samp{libiconv}.
33861 @node Running Configure
33862 @section Invoking the @value{GDBN} @file{configure} Script
33863 @cindex configuring @value{GDBN}
33864 @value{GDBN} comes with a @file{configure} script that automates the process
33865 of preparing @value{GDBN} for installation; you can then use @code{make} to
33866 build the @code{gdb} program.
33868 @c irrelevant in info file; it's as current as the code it lives with.
33869 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
33870 look at the @file{README} file in the sources; we may have improved the
33871 installation procedures since publishing this manual.}
33874 The @value{GDBN} distribution includes all the source code you need for
33875 @value{GDBN} in a single directory, whose name is usually composed by
33876 appending the version number to @samp{gdb}.
33878 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
33879 @file{gdb-@value{GDBVN}} directory. That directory contains:
33882 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
33883 script for configuring @value{GDBN} and all its supporting libraries
33885 @item gdb-@value{GDBVN}/gdb
33886 the source specific to @value{GDBN} itself
33888 @item gdb-@value{GDBVN}/bfd
33889 source for the Binary File Descriptor library
33891 @item gdb-@value{GDBVN}/include
33892 @sc{gnu} include files
33894 @item gdb-@value{GDBVN}/libiberty
33895 source for the @samp{-liberty} free software library
33897 @item gdb-@value{GDBVN}/opcodes
33898 source for the library of opcode tables and disassemblers
33900 @item gdb-@value{GDBVN}/readline
33901 source for the @sc{gnu} command-line interface
33903 @item gdb-@value{GDBVN}/glob
33904 source for the @sc{gnu} filename pattern-matching subroutine
33906 @item gdb-@value{GDBVN}/mmalloc
33907 source for the @sc{gnu} memory-mapped malloc package
33910 The simplest way to configure and build @value{GDBN} is to run @file{configure}
33911 from the @file{gdb-@var{version-number}} source directory, which in
33912 this example is the @file{gdb-@value{GDBVN}} directory.
33914 First switch to the @file{gdb-@var{version-number}} source directory
33915 if you are not already in it; then run @file{configure}. Pass the
33916 identifier for the platform on which @value{GDBN} will run as an
33922 cd gdb-@value{GDBVN}
33923 ./configure @var{host}
33928 where @var{host} is an identifier such as @samp{sun4} or
33929 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
33930 (You can often leave off @var{host}; @file{configure} tries to guess the
33931 correct value by examining your system.)
33933 Running @samp{configure @var{host}} and then running @code{make} builds the
33934 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
33935 libraries, then @code{gdb} itself. The configured source files, and the
33936 binaries, are left in the corresponding source directories.
33939 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
33940 system does not recognize this automatically when you run a different
33941 shell, you may need to run @code{sh} on it explicitly:
33944 sh configure @var{host}
33947 If you run @file{configure} from a directory that contains source
33948 directories for multiple libraries or programs, such as the
33949 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
33951 creates configuration files for every directory level underneath (unless
33952 you tell it not to, with the @samp{--norecursion} option).
33954 You should run the @file{configure} script from the top directory in the
33955 source tree, the @file{gdb-@var{version-number}} directory. If you run
33956 @file{configure} from one of the subdirectories, you will configure only
33957 that subdirectory. That is usually not what you want. In particular,
33958 if you run the first @file{configure} from the @file{gdb} subdirectory
33959 of the @file{gdb-@var{version-number}} directory, you will omit the
33960 configuration of @file{bfd}, @file{readline}, and other sibling
33961 directories of the @file{gdb} subdirectory. This leads to build errors
33962 about missing include files such as @file{bfd/bfd.h}.
33964 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
33965 However, you should make sure that the shell on your path (named by
33966 the @samp{SHELL} environment variable) is publicly readable. Remember
33967 that @value{GDBN} uses the shell to start your program---some systems refuse to
33968 let @value{GDBN} debug child processes whose programs are not readable.
33970 @node Separate Objdir
33971 @section Compiling @value{GDBN} in Another Directory
33973 If you want to run @value{GDBN} versions for several host or target machines,
33974 you need a different @code{gdb} compiled for each combination of
33975 host and target. @file{configure} is designed to make this easy by
33976 allowing you to generate each configuration in a separate subdirectory,
33977 rather than in the source directory. If your @code{make} program
33978 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
33979 @code{make} in each of these directories builds the @code{gdb}
33980 program specified there.
33982 To build @code{gdb} in a separate directory, run @file{configure}
33983 with the @samp{--srcdir} option to specify where to find the source.
33984 (You also need to specify a path to find @file{configure}
33985 itself from your working directory. If the path to @file{configure}
33986 would be the same as the argument to @samp{--srcdir}, you can leave out
33987 the @samp{--srcdir} option; it is assumed.)
33989 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
33990 separate directory for a Sun 4 like this:
33994 cd gdb-@value{GDBVN}
33997 ../gdb-@value{GDBVN}/configure sun4
34002 When @file{configure} builds a configuration using a remote source
34003 directory, it creates a tree for the binaries with the same structure
34004 (and using the same names) as the tree under the source directory. In
34005 the example, you'd find the Sun 4 library @file{libiberty.a} in the
34006 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
34007 @file{gdb-sun4/gdb}.
34009 Make sure that your path to the @file{configure} script has just one
34010 instance of @file{gdb} in it. If your path to @file{configure} looks
34011 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
34012 one subdirectory of @value{GDBN}, not the whole package. This leads to
34013 build errors about missing include files such as @file{bfd/bfd.h}.
34015 One popular reason to build several @value{GDBN} configurations in separate
34016 directories is to configure @value{GDBN} for cross-compiling (where
34017 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
34018 programs that run on another machine---the @dfn{target}).
34019 You specify a cross-debugging target by
34020 giving the @samp{--target=@var{target}} option to @file{configure}.
34022 When you run @code{make} to build a program or library, you must run
34023 it in a configured directory---whatever directory you were in when you
34024 called @file{configure} (or one of its subdirectories).
34026 The @code{Makefile} that @file{configure} generates in each source
34027 directory also runs recursively. If you type @code{make} in a source
34028 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
34029 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
34030 will build all the required libraries, and then build GDB.
34032 When you have multiple hosts or targets configured in separate
34033 directories, you can run @code{make} on them in parallel (for example,
34034 if they are NFS-mounted on each of the hosts); they will not interfere
34038 @section Specifying Names for Hosts and Targets
34040 The specifications used for hosts and targets in the @file{configure}
34041 script are based on a three-part naming scheme, but some short predefined
34042 aliases are also supported. The full naming scheme encodes three pieces
34043 of information in the following pattern:
34046 @var{architecture}-@var{vendor}-@var{os}
34049 For example, you can use the alias @code{sun4} as a @var{host} argument,
34050 or as the value for @var{target} in a @code{--target=@var{target}}
34051 option. The equivalent full name is @samp{sparc-sun-sunos4}.
34053 The @file{configure} script accompanying @value{GDBN} does not provide
34054 any query facility to list all supported host and target names or
34055 aliases. @file{configure} calls the Bourne shell script
34056 @code{config.sub} to map abbreviations to full names; you can read the
34057 script, if you wish, or you can use it to test your guesses on
34058 abbreviations---for example:
34061 % sh config.sub i386-linux
34063 % sh config.sub alpha-linux
34064 alpha-unknown-linux-gnu
34065 % sh config.sub hp9k700
34067 % sh config.sub sun4
34068 sparc-sun-sunos4.1.1
34069 % sh config.sub sun3
34070 m68k-sun-sunos4.1.1
34071 % sh config.sub i986v
34072 Invalid configuration `i986v': machine `i986v' not recognized
34076 @code{config.sub} is also distributed in the @value{GDBN} source
34077 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
34079 @node Configure Options
34080 @section @file{configure} Options
34082 Here is a summary of the @file{configure} options and arguments that
34083 are most often useful for building @value{GDBN}. @file{configure} also has
34084 several other options not listed here. @inforef{What Configure
34085 Does,,configure.info}, for a full explanation of @file{configure}.
34088 configure @r{[}--help@r{]}
34089 @r{[}--prefix=@var{dir}@r{]}
34090 @r{[}--exec-prefix=@var{dir}@r{]}
34091 @r{[}--srcdir=@var{dirname}@r{]}
34092 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
34093 @r{[}--target=@var{target}@r{]}
34098 You may introduce options with a single @samp{-} rather than
34099 @samp{--} if you prefer; but you may abbreviate option names if you use
34104 Display a quick summary of how to invoke @file{configure}.
34106 @item --prefix=@var{dir}
34107 Configure the source to install programs and files under directory
34110 @item --exec-prefix=@var{dir}
34111 Configure the source to install programs under directory
34114 @c avoid splitting the warning from the explanation:
34116 @item --srcdir=@var{dirname}
34117 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
34118 @code{make} that implements the @code{VPATH} feature.}@*
34119 Use this option to make configurations in directories separate from the
34120 @value{GDBN} source directories. Among other things, you can use this to
34121 build (or maintain) several configurations simultaneously, in separate
34122 directories. @file{configure} writes configuration-specific files in
34123 the current directory, but arranges for them to use the source in the
34124 directory @var{dirname}. @file{configure} creates directories under
34125 the working directory in parallel to the source directories below
34128 @item --norecursion
34129 Configure only the directory level where @file{configure} is executed; do not
34130 propagate configuration to subdirectories.
34132 @item --target=@var{target}
34133 Configure @value{GDBN} for cross-debugging programs running on the specified
34134 @var{target}. Without this option, @value{GDBN} is configured to debug
34135 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
34137 There is no convenient way to generate a list of all available targets.
34139 @item @var{host} @dots{}
34140 Configure @value{GDBN} to run on the specified @var{host}.
34142 There is no convenient way to generate a list of all available hosts.
34145 There are many other options available as well, but they are generally
34146 needed for special purposes only.
34148 @node System-wide configuration
34149 @section System-wide configuration and settings
34150 @cindex system-wide init file
34152 @value{GDBN} can be configured to have a system-wide init file;
34153 this file will be read and executed at startup (@pxref{Startup, , What
34154 @value{GDBN} does during startup}).
34156 Here is the corresponding configure option:
34159 @item --with-system-gdbinit=@var{file}
34160 Specify that the default location of the system-wide init file is
34164 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
34165 it may be subject to relocation. Two possible cases:
34169 If the default location of this init file contains @file{$prefix},
34170 it will be subject to relocation. Suppose that the configure options
34171 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
34172 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
34173 init file is looked for as @file{$install/etc/gdbinit} instead of
34174 @file{$prefix/etc/gdbinit}.
34177 By contrast, if the default location does not contain the prefix,
34178 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
34179 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
34180 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
34181 wherever @value{GDBN} is installed.
34184 If the configured location of the system-wide init file (as given by the
34185 @option{--with-system-gdbinit} option at configure time) is in the
34186 data-directory (as specified by @option{--with-gdb-datadir} at configure
34187 time) or in one of its subdirectories, then @value{GDBN} will look for the
34188 system-wide init file in the directory specified by the
34189 @option{--data-directory} command-line option.
34190 Note that the system-wide init file is only read once, during @value{GDBN}
34191 initialization. If the data-directory is changed after @value{GDBN} has
34192 started with the @code{set data-directory} command, the file will not be
34196 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
34199 @node System-wide Configuration Scripts
34200 @subsection Installed System-wide Configuration Scripts
34201 @cindex system-wide configuration scripts
34203 The @file{system-gdbinit} directory, located inside the data-directory
34204 (as specified by @option{--with-gdb-datadir} at configure time) contains
34205 a number of scripts which can be used as system-wide init files. To
34206 automatically source those scripts at startup, @value{GDBN} should be
34207 configured with @option{--with-system-gdbinit}. Otherwise, any user
34208 should be able to source them by hand as needed.
34210 The following scripts are currently available:
34213 @item @file{elinos.py}
34215 @cindex ELinOS system-wide configuration script
34216 This script is useful when debugging a program on an ELinOS target.
34217 It takes advantage of the environment variables defined in a standard
34218 ELinOS environment in order to determine the location of the system
34219 shared libraries, and then sets the @samp{solib-absolute-prefix}
34220 and @samp{solib-search-path} variables appropriately.
34222 @item @file{wrs-linux.py}
34223 @pindex wrs-linux.py
34224 @cindex Wind River Linux system-wide configuration script
34225 This script is useful when debugging a program on a target running
34226 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
34227 the host-side sysroot used by the target system.
34231 @node Maintenance Commands
34232 @appendix Maintenance Commands
34233 @cindex maintenance commands
34234 @cindex internal commands
34236 In addition to commands intended for @value{GDBN} users, @value{GDBN}
34237 includes a number of commands intended for @value{GDBN} developers,
34238 that are not documented elsewhere in this manual. These commands are
34239 provided here for reference. (For commands that turn on debugging
34240 messages, see @ref{Debugging Output}.)
34243 @kindex maint agent
34244 @kindex maint agent-eval
34245 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
34246 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
34247 Translate the given @var{expression} into remote agent bytecodes.
34248 This command is useful for debugging the Agent Expression mechanism
34249 (@pxref{Agent Expressions}). The @samp{agent} version produces an
34250 expression useful for data collection, such as by tracepoints, while
34251 @samp{maint agent-eval} produces an expression that evaluates directly
34252 to a result. For instance, a collection expression for @code{globa +
34253 globb} will include bytecodes to record four bytes of memory at each
34254 of the addresses of @code{globa} and @code{globb}, while discarding
34255 the result of the addition, while an evaluation expression will do the
34256 addition and return the sum.
34257 If @code{-at} is given, generate remote agent bytecode for @var{location}.
34258 If not, generate remote agent bytecode for current frame PC address.
34260 @kindex maint agent-printf
34261 @item maint agent-printf @var{format},@var{expr},...
34262 Translate the given format string and list of argument expressions
34263 into remote agent bytecodes and display them as a disassembled list.
34264 This command is useful for debugging the agent version of dynamic
34265 printf (@pxref{Dynamic Printf}).
34267 @kindex maint info breakpoints
34268 @item @anchor{maint info breakpoints}maint info breakpoints
34269 Using the same format as @samp{info breakpoints}, display both the
34270 breakpoints you've set explicitly, and those @value{GDBN} is using for
34271 internal purposes. Internal breakpoints are shown with negative
34272 breakpoint numbers. The type column identifies what kind of breakpoint
34277 Normal, explicitly set breakpoint.
34280 Normal, explicitly set watchpoint.
34283 Internal breakpoint, used to handle correctly stepping through
34284 @code{longjmp} calls.
34286 @item longjmp resume
34287 Internal breakpoint at the target of a @code{longjmp}.
34290 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
34293 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
34296 Shared library events.
34300 @kindex maint info btrace
34301 @item maint info btrace
34302 Pint information about raw branch tracing data.
34304 @kindex maint btrace packet-history
34305 @item maint btrace packet-history
34306 Print the raw branch trace packets that are used to compute the
34307 execution history for the @samp{record btrace} command. Both the
34308 information and the format in which it is printed depend on the btrace
34313 For the BTS recording format, print a list of blocks of sequential
34314 code. For each block, the following information is printed:
34318 Newer blocks have higher numbers. The oldest block has number zero.
34319 @item Lowest @samp{PC}
34320 @item Highest @samp{PC}
34324 For the Intel Processor Trace recording format, print a list of
34325 Intel Processor Trace packets. For each packet, the following
34326 information is printed:
34329 @item Packet number
34330 Newer packets have higher numbers. The oldest packet has number zero.
34332 The packet's offset in the trace stream.
34333 @item Packet opcode and payload
34337 @kindex maint btrace clear-packet-history
34338 @item maint btrace clear-packet-history
34339 Discards the cached packet history printed by the @samp{maint btrace
34340 packet-history} command. The history will be computed again when
34343 @kindex maint btrace clear
34344 @item maint btrace clear
34345 Discard the branch trace data. The data will be fetched anew and the
34346 branch trace will be recomputed when needed.
34348 This implicitly truncates the branch trace to a single branch trace
34349 buffer. When updating branch trace incrementally, the branch trace
34350 available to @value{GDBN} may be bigger than a single branch trace
34353 @kindex maint set btrace pt skip-pad
34354 @item maint set btrace pt skip-pad
34355 @kindex maint show btrace pt skip-pad
34356 @item maint show btrace pt skip-pad
34357 Control whether @value{GDBN} will skip PAD packets when computing the
34360 @kindex set displaced-stepping
34361 @kindex show displaced-stepping
34362 @cindex displaced stepping support
34363 @cindex out-of-line single-stepping
34364 @item set displaced-stepping
34365 @itemx show displaced-stepping
34366 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
34367 if the target supports it. Displaced stepping is a way to single-step
34368 over breakpoints without removing them from the inferior, by executing
34369 an out-of-line copy of the instruction that was originally at the
34370 breakpoint location. It is also known as out-of-line single-stepping.
34373 @item set displaced-stepping on
34374 If the target architecture supports it, @value{GDBN} will use
34375 displaced stepping to step over breakpoints.
34377 @item set displaced-stepping off
34378 @value{GDBN} will not use displaced stepping to step over breakpoints,
34379 even if such is supported by the target architecture.
34381 @cindex non-stop mode, and @samp{set displaced-stepping}
34382 @item set displaced-stepping auto
34383 This is the default mode. @value{GDBN} will use displaced stepping
34384 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
34385 architecture supports displaced stepping.
34388 @kindex maint check-psymtabs
34389 @item maint check-psymtabs
34390 Check the consistency of currently expanded psymtabs versus symtabs.
34391 Use this to check, for example, whether a symbol is in one but not the other.
34393 @kindex maint check-symtabs
34394 @item maint check-symtabs
34395 Check the consistency of currently expanded symtabs.
34397 @kindex maint expand-symtabs
34398 @item maint expand-symtabs [@var{regexp}]
34399 Expand symbol tables.
34400 If @var{regexp} is specified, only expand symbol tables for file
34401 names matching @var{regexp}.
34403 @kindex maint set catch-demangler-crashes
34404 @kindex maint show catch-demangler-crashes
34405 @cindex demangler crashes
34406 @item maint set catch-demangler-crashes [on|off]
34407 @itemx maint show catch-demangler-crashes
34408 Control whether @value{GDBN} should attempt to catch crashes in the
34409 symbol name demangler. The default is to attempt to catch crashes.
34410 If enabled, the first time a crash is caught, a core file is created,
34411 the offending symbol is displayed and the user is presented with the
34412 option to terminate the current session.
34414 @kindex maint cplus first_component
34415 @item maint cplus first_component @var{name}
34416 Print the first C@t{++} class/namespace component of @var{name}.
34418 @kindex maint cplus namespace
34419 @item maint cplus namespace
34420 Print the list of possible C@t{++} namespaces.
34422 @kindex maint deprecate
34423 @kindex maint undeprecate
34424 @cindex deprecated commands
34425 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
34426 @itemx maint undeprecate @var{command}
34427 Deprecate or undeprecate the named @var{command}. Deprecated commands
34428 cause @value{GDBN} to issue a warning when you use them. The optional
34429 argument @var{replacement} says which newer command should be used in
34430 favor of the deprecated one; if it is given, @value{GDBN} will mention
34431 the replacement as part of the warning.
34433 @kindex maint dump-me
34434 @item maint dump-me
34435 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
34436 Cause a fatal signal in the debugger and force it to dump its core.
34437 This is supported only on systems which support aborting a program
34438 with the @code{SIGQUIT} signal.
34440 @kindex maint internal-error
34441 @kindex maint internal-warning
34442 @kindex maint demangler-warning
34443 @cindex demangler crashes
34444 @item maint internal-error @r{[}@var{message-text}@r{]}
34445 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
34446 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
34448 Cause @value{GDBN} to call the internal function @code{internal_error},
34449 @code{internal_warning} or @code{demangler_warning} and hence behave
34450 as though an internal problem has been detected. In addition to
34451 reporting the internal problem, these functions give the user the
34452 opportunity to either quit @value{GDBN} or (for @code{internal_error}
34453 and @code{internal_warning}) create a core file of the current
34454 @value{GDBN} session.
34456 These commands take an optional parameter @var{message-text} that is
34457 used as the text of the error or warning message.
34459 Here's an example of using @code{internal-error}:
34462 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
34463 @dots{}/maint.c:121: internal-error: testing, 1, 2
34464 A problem internal to GDB has been detected. Further
34465 debugging may prove unreliable.
34466 Quit this debugging session? (y or n) @kbd{n}
34467 Create a core file? (y or n) @kbd{n}
34471 @cindex @value{GDBN} internal error
34472 @cindex internal errors, control of @value{GDBN} behavior
34473 @cindex demangler crashes
34475 @kindex maint set internal-error
34476 @kindex maint show internal-error
34477 @kindex maint set internal-warning
34478 @kindex maint show internal-warning
34479 @kindex maint set demangler-warning
34480 @kindex maint show demangler-warning
34481 @item maint set internal-error @var{action} [ask|yes|no]
34482 @itemx maint show internal-error @var{action}
34483 @itemx maint set internal-warning @var{action} [ask|yes|no]
34484 @itemx maint show internal-warning @var{action}
34485 @itemx maint set demangler-warning @var{action} [ask|yes|no]
34486 @itemx maint show demangler-warning @var{action}
34487 When @value{GDBN} reports an internal problem (error or warning) it
34488 gives the user the opportunity to both quit @value{GDBN} and create a
34489 core file of the current @value{GDBN} session. These commands let you
34490 override the default behaviour for each particular @var{action},
34491 described in the table below.
34495 You can specify that @value{GDBN} should always (yes) or never (no)
34496 quit. The default is to ask the user what to do.
34499 You can specify that @value{GDBN} should always (yes) or never (no)
34500 create a core file. The default is to ask the user what to do. Note
34501 that there is no @code{corefile} option for @code{demangler-warning}:
34502 demangler warnings always create a core file and this cannot be
34506 @kindex maint packet
34507 @item maint packet @var{text}
34508 If @value{GDBN} is talking to an inferior via the serial protocol,
34509 then this command sends the string @var{text} to the inferior, and
34510 displays the response packet. @value{GDBN} supplies the initial
34511 @samp{$} character, the terminating @samp{#} character, and the
34514 @kindex maint print architecture
34515 @item maint print architecture @r{[}@var{file}@r{]}
34516 Print the entire architecture configuration. The optional argument
34517 @var{file} names the file where the output goes.
34519 @kindex maint print c-tdesc
34520 @item maint print c-tdesc
34521 Print the current target description (@pxref{Target Descriptions}) as
34522 a C source file. The created source file can be used in @value{GDBN}
34523 when an XML parser is not available to parse the description.
34525 @kindex maint print dummy-frames
34526 @item maint print dummy-frames
34527 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
34530 (@value{GDBP}) @kbd{b add}
34532 (@value{GDBP}) @kbd{print add(2,3)}
34533 Breakpoint 2, add (a=2, b=3) at @dots{}
34535 The program being debugged stopped while in a function called from GDB.
34537 (@value{GDBP}) @kbd{maint print dummy-frames}
34538 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
34542 Takes an optional file parameter.
34544 @kindex maint print registers
34545 @kindex maint print raw-registers
34546 @kindex maint print cooked-registers
34547 @kindex maint print register-groups
34548 @kindex maint print remote-registers
34549 @item maint print registers @r{[}@var{file}@r{]}
34550 @itemx maint print raw-registers @r{[}@var{file}@r{]}
34551 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
34552 @itemx maint print register-groups @r{[}@var{file}@r{]}
34553 @itemx maint print remote-registers @r{[}@var{file}@r{]}
34554 Print @value{GDBN}'s internal register data structures.
34556 The command @code{maint print raw-registers} includes the contents of
34557 the raw register cache; the command @code{maint print
34558 cooked-registers} includes the (cooked) value of all registers,
34559 including registers which aren't available on the target nor visible
34560 to user; the command @code{maint print register-groups} includes the
34561 groups that each register is a member of; and the command @code{maint
34562 print remote-registers} includes the remote target's register numbers
34563 and offsets in the `G' packets.
34565 These commands take an optional parameter, a file name to which to
34566 write the information.
34568 @kindex maint print reggroups
34569 @item maint print reggroups @r{[}@var{file}@r{]}
34570 Print @value{GDBN}'s internal register group data structures. The
34571 optional argument @var{file} tells to what file to write the
34574 The register groups info looks like this:
34577 (@value{GDBP}) @kbd{maint print reggroups}
34590 This command forces @value{GDBN} to flush its internal register cache.
34592 @kindex maint print objfiles
34593 @cindex info for known object files
34594 @item maint print objfiles @r{[}@var{regexp}@r{]}
34595 Print a dump of all known object files.
34596 If @var{regexp} is specified, only print object files whose names
34597 match @var{regexp}. For each object file, this command prints its name,
34598 address in memory, and all of its psymtabs and symtabs.
34600 @kindex maint print user-registers
34601 @cindex user registers
34602 @item maint print user-registers
34603 List all currently available @dfn{user registers}. User registers
34604 typically provide alternate names for actual hardware registers. They
34605 include the four ``standard'' registers @code{$fp}, @code{$pc},
34606 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
34607 registers can be used in expressions in the same way as the canonical
34608 register names, but only the latter are listed by the @code{info
34609 registers} and @code{maint print registers} commands.
34611 @kindex maint print section-scripts
34612 @cindex info for known .debug_gdb_scripts-loaded scripts
34613 @item maint print section-scripts [@var{regexp}]
34614 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
34615 If @var{regexp} is specified, only print scripts loaded by object files
34616 matching @var{regexp}.
34617 For each script, this command prints its name as specified in the objfile,
34618 and the full path if known.
34619 @xref{dotdebug_gdb_scripts section}.
34621 @kindex maint print statistics
34622 @cindex bcache statistics
34623 @item maint print statistics
34624 This command prints, for each object file in the program, various data
34625 about that object file followed by the byte cache (@dfn{bcache})
34626 statistics for the object file. The objfile data includes the number
34627 of minimal, partial, full, and stabs symbols, the number of types
34628 defined by the objfile, the number of as yet unexpanded psym tables,
34629 the number of line tables and string tables, and the amount of memory
34630 used by the various tables. The bcache statistics include the counts,
34631 sizes, and counts of duplicates of all and unique objects, max,
34632 average, and median entry size, total memory used and its overhead and
34633 savings, and various measures of the hash table size and chain
34636 @kindex maint print target-stack
34637 @cindex target stack description
34638 @item maint print target-stack
34639 A @dfn{target} is an interface between the debugger and a particular
34640 kind of file or process. Targets can be stacked in @dfn{strata},
34641 so that more than one target can potentially respond to a request.
34642 In particular, memory accesses will walk down the stack of targets
34643 until they find a target that is interested in handling that particular
34646 This command prints a short description of each layer that was pushed on
34647 the @dfn{target stack}, starting from the top layer down to the bottom one.
34649 @kindex maint print type
34650 @cindex type chain of a data type
34651 @item maint print type @var{expr}
34652 Print the type chain for a type specified by @var{expr}. The argument
34653 can be either a type name or a symbol. If it is a symbol, the type of
34654 that symbol is described. The type chain produced by this command is
34655 a recursive definition of the data type as stored in @value{GDBN}'s
34656 data structures, including its flags and contained types.
34658 @kindex maint selftest
34660 Run any self tests that were compiled in to @value{GDBN}. This will
34661 print a message showing how many tests were run, and how many failed.
34663 @kindex maint set dwarf always-disassemble
34664 @kindex maint show dwarf always-disassemble
34665 @item maint set dwarf always-disassemble
34666 @item maint show dwarf always-disassemble
34667 Control the behavior of @code{info address} when using DWARF debugging
34670 The default is @code{off}, which means that @value{GDBN} should try to
34671 describe a variable's location in an easily readable format. When
34672 @code{on}, @value{GDBN} will instead display the DWARF location
34673 expression in an assembly-like format. Note that some locations are
34674 too complex for @value{GDBN} to describe simply; in this case you will
34675 always see the disassembly form.
34677 Here is an example of the resulting disassembly:
34680 (gdb) info addr argc
34681 Symbol "argc" is a complex DWARF expression:
34685 For more information on these expressions, see
34686 @uref{http://www.dwarfstd.org/, the DWARF standard}.
34688 @kindex maint set dwarf max-cache-age
34689 @kindex maint show dwarf max-cache-age
34690 @item maint set dwarf max-cache-age
34691 @itemx maint show dwarf max-cache-age
34692 Control the DWARF compilation unit cache.
34694 @cindex DWARF compilation units cache
34695 In object files with inter-compilation-unit references, such as those
34696 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
34697 reader needs to frequently refer to previously read compilation units.
34698 This setting controls how long a compilation unit will remain in the
34699 cache if it is not referenced. A higher limit means that cached
34700 compilation units will be stored in memory longer, and more total
34701 memory will be used. Setting it to zero disables caching, which will
34702 slow down @value{GDBN} startup, but reduce memory consumption.
34704 @kindex maint set profile
34705 @kindex maint show profile
34706 @cindex profiling GDB
34707 @item maint set profile
34708 @itemx maint show profile
34709 Control profiling of @value{GDBN}.
34711 Profiling will be disabled until you use the @samp{maint set profile}
34712 command to enable it. When you enable profiling, the system will begin
34713 collecting timing and execution count data; when you disable profiling or
34714 exit @value{GDBN}, the results will be written to a log file. Remember that
34715 if you use profiling, @value{GDBN} will overwrite the profiling log file
34716 (often called @file{gmon.out}). If you have a record of important profiling
34717 data in a @file{gmon.out} file, be sure to move it to a safe location.
34719 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
34720 compiled with the @samp{-pg} compiler option.
34722 @kindex maint set show-debug-regs
34723 @kindex maint show show-debug-regs
34724 @cindex hardware debug registers
34725 @item maint set show-debug-regs
34726 @itemx maint show show-debug-regs
34727 Control whether to show variables that mirror the hardware debug
34728 registers. Use @code{on} to enable, @code{off} to disable. If
34729 enabled, the debug registers values are shown when @value{GDBN} inserts or
34730 removes a hardware breakpoint or watchpoint, and when the inferior
34731 triggers a hardware-assisted breakpoint or watchpoint.
34733 @kindex maint set show-all-tib
34734 @kindex maint show show-all-tib
34735 @item maint set show-all-tib
34736 @itemx maint show show-all-tib
34737 Control whether to show all non zero areas within a 1k block starting
34738 at thread local base, when using the @samp{info w32 thread-information-block}
34741 @kindex maint set target-async
34742 @kindex maint show target-async
34743 @item maint set target-async
34744 @itemx maint show target-async
34745 This controls whether @value{GDBN} targets operate in synchronous or
34746 asynchronous mode (@pxref{Background Execution}). Normally the
34747 default is asynchronous, if it is available; but this can be changed
34748 to more easily debug problems occurring only in synchronous mode.
34750 @kindex maint set target-non-stop @var{mode} [on|off|auto]
34751 @kindex maint show target-non-stop
34752 @item maint set target-non-stop
34753 @itemx maint show target-non-stop
34755 This controls whether @value{GDBN} targets always operate in non-stop
34756 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
34757 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
34758 if supported by the target.
34761 @item maint set target-non-stop auto
34762 This is the default mode. @value{GDBN} controls the target in
34763 non-stop mode if the target supports it.
34765 @item maint set target-non-stop on
34766 @value{GDBN} controls the target in non-stop mode even if the target
34767 does not indicate support.
34769 @item maint set target-non-stop off
34770 @value{GDBN} does not control the target in non-stop mode even if the
34771 target supports it.
34774 @kindex maint set per-command
34775 @kindex maint show per-command
34776 @item maint set per-command
34777 @itemx maint show per-command
34778 @cindex resources used by commands
34780 @value{GDBN} can display the resources used by each command.
34781 This is useful in debugging performance problems.
34784 @item maint set per-command space [on|off]
34785 @itemx maint show per-command space
34786 Enable or disable the printing of the memory used by GDB for each command.
34787 If enabled, @value{GDBN} will display how much memory each command
34788 took, following the command's own output.
34789 This can also be requested by invoking @value{GDBN} with the
34790 @option{--statistics} command-line switch (@pxref{Mode Options}).
34792 @item maint set per-command time [on|off]
34793 @itemx maint show per-command time
34794 Enable or disable the printing of the execution time of @value{GDBN}
34796 If enabled, @value{GDBN} will display how much time it
34797 took to execute each command, following the command's own output.
34798 Both CPU time and wallclock time are printed.
34799 Printing both is useful when trying to determine whether the cost is
34800 CPU or, e.g., disk/network latency.
34801 Note that the CPU time printed is for @value{GDBN} only, it does not include
34802 the execution time of the inferior because there's no mechanism currently
34803 to compute how much time was spent by @value{GDBN} and how much time was
34804 spent by the program been debugged.
34805 This can also be requested by invoking @value{GDBN} with the
34806 @option{--statistics} command-line switch (@pxref{Mode Options}).
34808 @item maint set per-command symtab [on|off]
34809 @itemx maint show per-command symtab
34810 Enable or disable the printing of basic symbol table statistics
34812 If enabled, @value{GDBN} will display the following information:
34816 number of symbol tables
34818 number of primary symbol tables
34820 number of blocks in the blockvector
34824 @kindex maint space
34825 @cindex memory used by commands
34826 @item maint space @var{value}
34827 An alias for @code{maint set per-command space}.
34828 A non-zero value enables it, zero disables it.
34831 @cindex time of command execution
34832 @item maint time @var{value}
34833 An alias for @code{maint set per-command time}.
34834 A non-zero value enables it, zero disables it.
34836 @kindex maint translate-address
34837 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
34838 Find the symbol stored at the location specified by the address
34839 @var{addr} and an optional section name @var{section}. If found,
34840 @value{GDBN} prints the name of the closest symbol and an offset from
34841 the symbol's location to the specified address. This is similar to
34842 the @code{info address} command (@pxref{Symbols}), except that this
34843 command also allows to find symbols in other sections.
34845 If section was not specified, the section in which the symbol was found
34846 is also printed. For dynamically linked executables, the name of
34847 executable or shared library containing the symbol is printed as well.
34851 The following command is useful for non-interactive invocations of
34852 @value{GDBN}, such as in the test suite.
34855 @item set watchdog @var{nsec}
34856 @kindex set watchdog
34857 @cindex watchdog timer
34858 @cindex timeout for commands
34859 Set the maximum number of seconds @value{GDBN} will wait for the
34860 target operation to finish. If this time expires, @value{GDBN}
34861 reports and error and the command is aborted.
34863 @item show watchdog
34864 Show the current setting of the target wait timeout.
34867 @node Remote Protocol
34868 @appendix @value{GDBN} Remote Serial Protocol
34873 * Stop Reply Packets::
34874 * General Query Packets::
34875 * Architecture-Specific Protocol Details::
34876 * Tracepoint Packets::
34877 * Host I/O Packets::
34879 * Notification Packets::
34880 * Remote Non-Stop::
34881 * Packet Acknowledgment::
34883 * File-I/O Remote Protocol Extension::
34884 * Library List Format::
34885 * Library List Format for SVR4 Targets::
34886 * Memory Map Format::
34887 * Thread List Format::
34888 * Traceframe Info Format::
34889 * Branch Trace Format::
34890 * Branch Trace Configuration Format::
34896 There may be occasions when you need to know something about the
34897 protocol---for example, if there is only one serial port to your target
34898 machine, you might want your program to do something special if it
34899 recognizes a packet meant for @value{GDBN}.
34901 In the examples below, @samp{->} and @samp{<-} are used to indicate
34902 transmitted and received data, respectively.
34904 @cindex protocol, @value{GDBN} remote serial
34905 @cindex serial protocol, @value{GDBN} remote
34906 @cindex remote serial protocol
34907 All @value{GDBN} commands and responses (other than acknowledgments
34908 and notifications, see @ref{Notification Packets}) are sent as a
34909 @var{packet}. A @var{packet} is introduced with the character
34910 @samp{$}, the actual @var{packet-data}, and the terminating character
34911 @samp{#} followed by a two-digit @var{checksum}:
34914 @code{$}@var{packet-data}@code{#}@var{checksum}
34918 @cindex checksum, for @value{GDBN} remote
34920 The two-digit @var{checksum} is computed as the modulo 256 sum of all
34921 characters between the leading @samp{$} and the trailing @samp{#} (an
34922 eight bit unsigned checksum).
34924 Implementors should note that prior to @value{GDBN} 5.0 the protocol
34925 specification also included an optional two-digit @var{sequence-id}:
34928 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
34931 @cindex sequence-id, for @value{GDBN} remote
34933 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
34934 has never output @var{sequence-id}s. Stubs that handle packets added
34935 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
34937 When either the host or the target machine receives a packet, the first
34938 response expected is an acknowledgment: either @samp{+} (to indicate
34939 the package was received correctly) or @samp{-} (to request
34943 -> @code{$}@var{packet-data}@code{#}@var{checksum}
34948 The @samp{+}/@samp{-} acknowledgments can be disabled
34949 once a connection is established.
34950 @xref{Packet Acknowledgment}, for details.
34952 The host (@value{GDBN}) sends @var{command}s, and the target (the
34953 debugging stub incorporated in your program) sends a @var{response}. In
34954 the case of step and continue @var{command}s, the response is only sent
34955 when the operation has completed, and the target has again stopped all
34956 threads in all attached processes. This is the default all-stop mode
34957 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
34958 execution mode; see @ref{Remote Non-Stop}, for details.
34960 @var{packet-data} consists of a sequence of characters with the
34961 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
34964 @cindex remote protocol, field separator
34965 Fields within the packet should be separated using @samp{,} @samp{;} or
34966 @samp{:}. Except where otherwise noted all numbers are represented in
34967 @sc{hex} with leading zeros suppressed.
34969 Implementors should note that prior to @value{GDBN} 5.0, the character
34970 @samp{:} could not appear as the third character in a packet (as it
34971 would potentially conflict with the @var{sequence-id}).
34973 @cindex remote protocol, binary data
34974 @anchor{Binary Data}
34975 Binary data in most packets is encoded either as two hexadecimal
34976 digits per byte of binary data. This allowed the traditional remote
34977 protocol to work over connections which were only seven-bit clean.
34978 Some packets designed more recently assume an eight-bit clean
34979 connection, and use a more efficient encoding to send and receive
34982 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
34983 as an escape character. Any escaped byte is transmitted as the escape
34984 character followed by the original character XORed with @code{0x20}.
34985 For example, the byte @code{0x7d} would be transmitted as the two
34986 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
34987 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
34988 @samp{@}}) must always be escaped. Responses sent by the stub
34989 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
34990 is not interpreted as the start of a run-length encoded sequence
34993 Response @var{data} can be run-length encoded to save space.
34994 Run-length encoding replaces runs of identical characters with one
34995 instance of the repeated character, followed by a @samp{*} and a
34996 repeat count. The repeat count is itself sent encoded, to avoid
34997 binary characters in @var{data}: a value of @var{n} is sent as
34998 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
34999 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
35000 code 32) for a repeat count of 3. (This is because run-length
35001 encoding starts to win for counts 3 or more.) Thus, for example,
35002 @samp{0* } is a run-length encoding of ``0000'': the space character
35003 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
35006 The printable characters @samp{#} and @samp{$} or with a numeric value
35007 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
35008 seven repeats (@samp{$}) can be expanded using a repeat count of only
35009 five (@samp{"}). For example, @samp{00000000} can be encoded as
35012 The error response returned for some packets includes a two character
35013 error number. That number is not well defined.
35015 @cindex empty response, for unsupported packets
35016 For any @var{command} not supported by the stub, an empty response
35017 (@samp{$#00}) should be returned. That way it is possible to extend the
35018 protocol. A newer @value{GDBN} can tell if a packet is supported based
35021 At a minimum, a stub is required to support the @samp{g} and @samp{G}
35022 commands for register access, and the @samp{m} and @samp{M} commands
35023 for memory access. Stubs that only control single-threaded targets
35024 can implement run control with the @samp{c} (continue), and @samp{s}
35025 (step) commands. Stubs that support multi-threading targets should
35026 support the @samp{vCont} command. All other commands are optional.
35031 The following table provides a complete list of all currently defined
35032 @var{command}s and their corresponding response @var{data}.
35033 @xref{File-I/O Remote Protocol Extension}, for details about the File
35034 I/O extension of the remote protocol.
35036 Each packet's description has a template showing the packet's overall
35037 syntax, followed by an explanation of the packet's meaning. We
35038 include spaces in some of the templates for clarity; these are not
35039 part of the packet's syntax. No @value{GDBN} packet uses spaces to
35040 separate its components. For example, a template like @samp{foo
35041 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
35042 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
35043 @var{baz}. @value{GDBN} does not transmit a space character between the
35044 @samp{foo} and the @var{bar}, or between the @var{bar} and the
35047 @cindex @var{thread-id}, in remote protocol
35048 @anchor{thread-id syntax}
35049 Several packets and replies include a @var{thread-id} field to identify
35050 a thread. Normally these are positive numbers with a target-specific
35051 interpretation, formatted as big-endian hex strings. A @var{thread-id}
35052 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
35055 In addition, the remote protocol supports a multiprocess feature in
35056 which the @var{thread-id} syntax is extended to optionally include both
35057 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
35058 The @var{pid} (process) and @var{tid} (thread) components each have the
35059 format described above: a positive number with target-specific
35060 interpretation formatted as a big-endian hex string, literal @samp{-1}
35061 to indicate all processes or threads (respectively), or @samp{0} to
35062 indicate an arbitrary process or thread. Specifying just a process, as
35063 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
35064 error to specify all processes but a specific thread, such as
35065 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
35066 for those packets and replies explicitly documented to include a process
35067 ID, rather than a @var{thread-id}.
35069 The multiprocess @var{thread-id} syntax extensions are only used if both
35070 @value{GDBN} and the stub report support for the @samp{multiprocess}
35071 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
35074 Note that all packet forms beginning with an upper- or lower-case
35075 letter, other than those described here, are reserved for future use.
35077 Here are the packet descriptions.
35082 @cindex @samp{!} packet
35083 @anchor{extended mode}
35084 Enable extended mode. In extended mode, the remote server is made
35085 persistent. The @samp{R} packet is used to restart the program being
35091 The remote target both supports and has enabled extended mode.
35095 @cindex @samp{?} packet
35097 Indicate the reason the target halted. The reply is the same as for
35098 step and continue. This packet has a special interpretation when the
35099 target is in non-stop mode; see @ref{Remote Non-Stop}.
35102 @xref{Stop Reply Packets}, for the reply specifications.
35104 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
35105 @cindex @samp{A} packet
35106 Initialized @code{argv[]} array passed into program. @var{arglen}
35107 specifies the number of bytes in the hex encoded byte stream
35108 @var{arg}. See @code{gdbserver} for more details.
35113 The arguments were set.
35119 @cindex @samp{b} packet
35120 (Don't use this packet; its behavior is not well-defined.)
35121 Change the serial line speed to @var{baud}.
35123 JTC: @emph{When does the transport layer state change? When it's
35124 received, or after the ACK is transmitted. In either case, there are
35125 problems if the command or the acknowledgment packet is dropped.}
35127 Stan: @emph{If people really wanted to add something like this, and get
35128 it working for the first time, they ought to modify ser-unix.c to send
35129 some kind of out-of-band message to a specially-setup stub and have the
35130 switch happen "in between" packets, so that from remote protocol's point
35131 of view, nothing actually happened.}
35133 @item B @var{addr},@var{mode}
35134 @cindex @samp{B} packet
35135 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
35136 breakpoint at @var{addr}.
35138 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
35139 (@pxref{insert breakpoint or watchpoint packet}).
35141 @cindex @samp{bc} packet
35144 Backward continue. Execute the target system in reverse. No parameter.
35145 @xref{Reverse Execution}, for more information.
35148 @xref{Stop Reply Packets}, for the reply specifications.
35150 @cindex @samp{bs} packet
35153 Backward single step. Execute one instruction in reverse. No parameter.
35154 @xref{Reverse Execution}, for more information.
35157 @xref{Stop Reply Packets}, for the reply specifications.
35159 @item c @r{[}@var{addr}@r{]}
35160 @cindex @samp{c} packet
35161 Continue at @var{addr}, which is the address to resume. If @var{addr}
35162 is omitted, resume at current address.
35164 This packet is deprecated for multi-threading support. @xref{vCont
35168 @xref{Stop Reply Packets}, for the reply specifications.
35170 @item C @var{sig}@r{[};@var{addr}@r{]}
35171 @cindex @samp{C} packet
35172 Continue with signal @var{sig} (hex signal number). If
35173 @samp{;@var{addr}} is omitted, resume at same address.
35175 This packet is deprecated for multi-threading support. @xref{vCont
35179 @xref{Stop Reply Packets}, for the reply specifications.
35182 @cindex @samp{d} packet
35185 Don't use this packet; instead, define a general set packet
35186 (@pxref{General Query Packets}).
35190 @cindex @samp{D} packet
35191 The first form of the packet is used to detach @value{GDBN} from the
35192 remote system. It is sent to the remote target
35193 before @value{GDBN} disconnects via the @code{detach} command.
35195 The second form, including a process ID, is used when multiprocess
35196 protocol extensions are enabled (@pxref{multiprocess extensions}), to
35197 detach only a specific process. The @var{pid} is specified as a
35198 big-endian hex string.
35208 @item F @var{RC},@var{EE},@var{CF};@var{XX}
35209 @cindex @samp{F} packet
35210 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
35211 This is part of the File-I/O protocol extension. @xref{File-I/O
35212 Remote Protocol Extension}, for the specification.
35215 @anchor{read registers packet}
35216 @cindex @samp{g} packet
35217 Read general registers.
35221 @item @var{XX@dots{}}
35222 Each byte of register data is described by two hex digits. The bytes
35223 with the register are transmitted in target byte order. The size of
35224 each register and their position within the @samp{g} packet are
35225 determined by the @value{GDBN} internal gdbarch functions
35226 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
35227 specification of several standard @samp{g} packets is specified below.
35229 When reading registers from a trace frame (@pxref{Analyze Collected
35230 Data,,Using the Collected Data}), the stub may also return a string of
35231 literal @samp{x}'s in place of the register data digits, to indicate
35232 that the corresponding register has not been collected, thus its value
35233 is unavailable. For example, for an architecture with 4 registers of
35234 4 bytes each, the following reply indicates to @value{GDBN} that
35235 registers 0 and 2 have not been collected, while registers 1 and 3
35236 have been collected, and both have zero value:
35240 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
35247 @item G @var{XX@dots{}}
35248 @cindex @samp{G} packet
35249 Write general registers. @xref{read registers packet}, for a
35250 description of the @var{XX@dots{}} data.
35260 @item H @var{op} @var{thread-id}
35261 @cindex @samp{H} packet
35262 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
35263 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
35264 should be @samp{c} for step and continue operations (note that this
35265 is deprecated, supporting the @samp{vCont} command is a better
35266 option), and @samp{g} for other operations. The thread designator
35267 @var{thread-id} has the format and interpretation described in
35268 @ref{thread-id syntax}.
35279 @c 'H': How restrictive (or permissive) is the thread model. If a
35280 @c thread is selected and stopped, are other threads allowed
35281 @c to continue to execute? As I mentioned above, I think the
35282 @c semantics of each command when a thread is selected must be
35283 @c described. For example:
35285 @c 'g': If the stub supports threads and a specific thread is
35286 @c selected, returns the register block from that thread;
35287 @c otherwise returns current registers.
35289 @c 'G' If the stub supports threads and a specific thread is
35290 @c selected, sets the registers of the register block of
35291 @c that thread; otherwise sets current registers.
35293 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
35294 @anchor{cycle step packet}
35295 @cindex @samp{i} packet
35296 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
35297 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
35298 step starting at that address.
35301 @cindex @samp{I} packet
35302 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
35306 @cindex @samp{k} packet
35309 The exact effect of this packet is not specified.
35311 For a bare-metal target, it may power cycle or reset the target
35312 system. For that reason, the @samp{k} packet has no reply.
35314 For a single-process target, it may kill that process if possible.
35316 A multiple-process target may choose to kill just one process, or all
35317 that are under @value{GDBN}'s control. For more precise control, use
35318 the vKill packet (@pxref{vKill packet}).
35320 If the target system immediately closes the connection in response to
35321 @samp{k}, @value{GDBN} does not consider the lack of packet
35322 acknowledgment to be an error, and assumes the kill was successful.
35324 If connected using @kbd{target extended-remote}, and the target does
35325 not close the connection in response to a kill request, @value{GDBN}
35326 probes the target state as if a new connection was opened
35327 (@pxref{? packet}).
35329 @item m @var{addr},@var{length}
35330 @cindex @samp{m} packet
35331 Read @var{length} addressable memory units starting at address @var{addr}
35332 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
35333 any particular boundary.
35335 The stub need not use any particular size or alignment when gathering
35336 data from memory for the response; even if @var{addr} is word-aligned
35337 and @var{length} is a multiple of the word size, the stub is free to
35338 use byte accesses, or not. For this reason, this packet may not be
35339 suitable for accessing memory-mapped I/O devices.
35340 @cindex alignment of remote memory accesses
35341 @cindex size of remote memory accesses
35342 @cindex memory, alignment and size of remote accesses
35346 @item @var{XX@dots{}}
35347 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
35348 The reply may contain fewer addressable memory units than requested if the
35349 server was able to read only part of the region of memory.
35354 @item M @var{addr},@var{length}:@var{XX@dots{}}
35355 @cindex @samp{M} packet
35356 Write @var{length} addressable memory units starting at address @var{addr}
35357 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
35358 byte is transmitted as a two-digit hexadecimal number.
35365 for an error (this includes the case where only part of the data was
35370 @cindex @samp{p} packet
35371 Read the value of register @var{n}; @var{n} is in hex.
35372 @xref{read registers packet}, for a description of how the returned
35373 register value is encoded.
35377 @item @var{XX@dots{}}
35378 the register's value
35382 Indicating an unrecognized @var{query}.
35385 @item P @var{n@dots{}}=@var{r@dots{}}
35386 @anchor{write register packet}
35387 @cindex @samp{P} packet
35388 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
35389 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
35390 digits for each byte in the register (target byte order).
35400 @item q @var{name} @var{params}@dots{}
35401 @itemx Q @var{name} @var{params}@dots{}
35402 @cindex @samp{q} packet
35403 @cindex @samp{Q} packet
35404 General query (@samp{q}) and set (@samp{Q}). These packets are
35405 described fully in @ref{General Query Packets}.
35408 @cindex @samp{r} packet
35409 Reset the entire system.
35411 Don't use this packet; use the @samp{R} packet instead.
35414 @cindex @samp{R} packet
35415 Restart the program being debugged. The @var{XX}, while needed, is ignored.
35416 This packet is only available in extended mode (@pxref{extended mode}).
35418 The @samp{R} packet has no reply.
35420 @item s @r{[}@var{addr}@r{]}
35421 @cindex @samp{s} packet
35422 Single step, resuming at @var{addr}. If
35423 @var{addr} is omitted, resume at same address.
35425 This packet is deprecated for multi-threading support. @xref{vCont
35429 @xref{Stop Reply Packets}, for the reply specifications.
35431 @item S @var{sig}@r{[};@var{addr}@r{]}
35432 @anchor{step with signal packet}
35433 @cindex @samp{S} packet
35434 Step with signal. This is analogous to the @samp{C} packet, but
35435 requests a single-step, rather than a normal resumption of execution.
35437 This packet is deprecated for multi-threading support. @xref{vCont
35441 @xref{Stop Reply Packets}, for the reply specifications.
35443 @item t @var{addr}:@var{PP},@var{MM}
35444 @cindex @samp{t} packet
35445 Search backwards starting at address @var{addr} for a match with pattern
35446 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
35447 There must be at least 3 digits in @var{addr}.
35449 @item T @var{thread-id}
35450 @cindex @samp{T} packet
35451 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
35456 thread is still alive
35462 Packets starting with @samp{v} are identified by a multi-letter name,
35463 up to the first @samp{;} or @samp{?} (or the end of the packet).
35465 @item vAttach;@var{pid}
35466 @cindex @samp{vAttach} packet
35467 Attach to a new process with the specified process ID @var{pid}.
35468 The process ID is a
35469 hexadecimal integer identifying the process. In all-stop mode, all
35470 threads in the attached process are stopped; in non-stop mode, it may be
35471 attached without being stopped if that is supported by the target.
35473 @c In non-stop mode, on a successful vAttach, the stub should set the
35474 @c current thread to a thread of the newly-attached process. After
35475 @c attaching, GDB queries for the attached process's thread ID with qC.
35476 @c Also note that, from a user perspective, whether or not the
35477 @c target is stopped on attach in non-stop mode depends on whether you
35478 @c use the foreground or background version of the attach command, not
35479 @c on what vAttach does; GDB does the right thing with respect to either
35480 @c stopping or restarting threads.
35482 This packet is only available in extended mode (@pxref{extended mode}).
35488 @item @r{Any stop packet}
35489 for success in all-stop mode (@pxref{Stop Reply Packets})
35491 for success in non-stop mode (@pxref{Remote Non-Stop})
35494 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
35495 @cindex @samp{vCont} packet
35496 @anchor{vCont packet}
35497 Resume the inferior, specifying different actions for each thread.
35498 If an action is specified with no @var{thread-id}, then it is applied to any
35499 threads that don't have a specific action specified; if no default action is
35500 specified then other threads should remain stopped in all-stop mode and
35501 in their current state in non-stop mode.
35502 Specifying multiple
35503 default actions is an error; specifying no actions is also an error.
35504 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
35506 Currently supported actions are:
35512 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
35516 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
35519 @item r @var{start},@var{end}
35520 Step once, and then keep stepping as long as the thread stops at
35521 addresses between @var{start} (inclusive) and @var{end} (exclusive).
35522 The remote stub reports a stop reply when either the thread goes out
35523 of the range or is stopped due to an unrelated reason, such as hitting
35524 a breakpoint. @xref{range stepping}.
35526 If the range is empty (@var{start} == @var{end}), then the action
35527 becomes equivalent to the @samp{s} action. In other words,
35528 single-step once, and report the stop (even if the stepped instruction
35529 jumps to @var{start}).
35531 (A stop reply may be sent at any point even if the PC is still within
35532 the stepping range; for example, it is valid to implement this packet
35533 in a degenerate way as a single instruction step operation.)
35537 The optional argument @var{addr} normally associated with the
35538 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
35539 not supported in @samp{vCont}.
35541 The @samp{t} action is only relevant in non-stop mode
35542 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
35543 A stop reply should be generated for any affected thread not already stopped.
35544 When a thread is stopped by means of a @samp{t} action,
35545 the corresponding stop reply should indicate that the thread has stopped with
35546 signal @samp{0}, regardless of whether the target uses some other signal
35547 as an implementation detail.
35549 The stub must support @samp{vCont} if it reports support for
35550 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
35551 this case @samp{vCont} actions can be specified to apply to all threads
35552 in a process by using the @samp{p@var{pid}.-1} form of the
35556 @xref{Stop Reply Packets}, for the reply specifications.
35559 @cindex @samp{vCont?} packet
35560 Request a list of actions supported by the @samp{vCont} packet.
35564 @item vCont@r{[};@var{action}@dots{}@r{]}
35565 The @samp{vCont} packet is supported. Each @var{action} is a supported
35566 command in the @samp{vCont} packet.
35568 The @samp{vCont} packet is not supported.
35571 @anchor{vCtrlC packet}
35573 @cindex @samp{vCtrlC} packet
35574 Interrupt remote target as if a control-C was pressed on the remote
35575 terminal. This is the equivalent to reacting to the @code{^C}
35576 (@samp{\003}, the control-C character) character in all-stop mode
35577 while the target is running, except this works in non-stop mode.
35578 @xref{interrupting remote targets}, for more info on the all-stop
35589 @item vFile:@var{operation}:@var{parameter}@dots{}
35590 @cindex @samp{vFile} packet
35591 Perform a file operation on the target system. For details,
35592 see @ref{Host I/O Packets}.
35594 @item vFlashErase:@var{addr},@var{length}
35595 @cindex @samp{vFlashErase} packet
35596 Direct the stub to erase @var{length} bytes of flash starting at
35597 @var{addr}. The region may enclose any number of flash blocks, but
35598 its start and end must fall on block boundaries, as indicated by the
35599 flash block size appearing in the memory map (@pxref{Memory Map
35600 Format}). @value{GDBN} groups flash memory programming operations
35601 together, and sends a @samp{vFlashDone} request after each group; the
35602 stub is allowed to delay erase operation until the @samp{vFlashDone}
35603 packet is received.
35613 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
35614 @cindex @samp{vFlashWrite} packet
35615 Direct the stub to write data to flash address @var{addr}. The data
35616 is passed in binary form using the same encoding as for the @samp{X}
35617 packet (@pxref{Binary Data}). The memory ranges specified by
35618 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
35619 not overlap, and must appear in order of increasing addresses
35620 (although @samp{vFlashErase} packets for higher addresses may already
35621 have been received; the ordering is guaranteed only between
35622 @samp{vFlashWrite} packets). If a packet writes to an address that was
35623 neither erased by a preceding @samp{vFlashErase} packet nor by some other
35624 target-specific method, the results are unpredictable.
35632 for vFlashWrite addressing non-flash memory
35638 @cindex @samp{vFlashDone} packet
35639 Indicate to the stub that flash programming operation is finished.
35640 The stub is permitted to delay or batch the effects of a group of
35641 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
35642 @samp{vFlashDone} packet is received. The contents of the affected
35643 regions of flash memory are unpredictable until the @samp{vFlashDone}
35644 request is completed.
35646 @item vKill;@var{pid}
35647 @cindex @samp{vKill} packet
35648 @anchor{vKill packet}
35649 Kill the process with the specified process ID @var{pid}, which is a
35650 hexadecimal integer identifying the process. This packet is used in
35651 preference to @samp{k} when multiprocess protocol extensions are
35652 supported; see @ref{multiprocess extensions}.
35662 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
35663 @cindex @samp{vRun} packet
35664 Run the program @var{filename}, passing it each @var{argument} on its
35665 command line. The file and arguments are hex-encoded strings. If
35666 @var{filename} is an empty string, the stub may use a default program
35667 (e.g.@: the last program run). The program is created in the stopped
35670 @c FIXME: What about non-stop mode?
35672 This packet is only available in extended mode (@pxref{extended mode}).
35678 @item @r{Any stop packet}
35679 for success (@pxref{Stop Reply Packets})
35683 @cindex @samp{vStopped} packet
35684 @xref{Notification Packets}.
35686 @item X @var{addr},@var{length}:@var{XX@dots{}}
35688 @cindex @samp{X} packet
35689 Write data to memory, where the data is transmitted in binary.
35690 Memory is specified by its address @var{addr} and number of addressable memory
35691 units @var{length} (@pxref{addressable memory unit});
35692 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
35702 @item z @var{type},@var{addr},@var{kind}
35703 @itemx Z @var{type},@var{addr},@var{kind}
35704 @anchor{insert breakpoint or watchpoint packet}
35705 @cindex @samp{z} packet
35706 @cindex @samp{Z} packets
35707 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
35708 watchpoint starting at address @var{address} of kind @var{kind}.
35710 Each breakpoint and watchpoint packet @var{type} is documented
35713 @emph{Implementation notes: A remote target shall return an empty string
35714 for an unrecognized breakpoint or watchpoint packet @var{type}. A
35715 remote target shall support either both or neither of a given
35716 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
35717 avoid potential problems with duplicate packets, the operations should
35718 be implemented in an idempotent way.}
35720 @item z0,@var{addr},@var{kind}
35721 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
35722 @cindex @samp{z0} packet
35723 @cindex @samp{Z0} packet
35724 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
35725 @var{addr} of type @var{kind}.
35727 A memory breakpoint is implemented by replacing the instruction at
35728 @var{addr} with a software breakpoint or trap instruction. The
35729 @var{kind} is target-specific and typically indicates the size of
35730 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
35731 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
35732 architectures have additional meanings for @var{kind};
35733 @var{cond_list} is an optional list of conditional expressions in bytecode
35734 form that should be evaluated on the target's side. These are the
35735 conditions that should be taken into consideration when deciding if
35736 the breakpoint trigger should be reported back to @var{GDBN}.
35738 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
35739 for how to best report a memory breakpoint event to @value{GDBN}.
35741 The @var{cond_list} parameter is comprised of a series of expressions,
35742 concatenated without separators. Each expression has the following form:
35746 @item X @var{len},@var{expr}
35747 @var{len} is the length of the bytecode expression and @var{expr} is the
35748 actual conditional expression in bytecode form.
35752 The optional @var{cmd_list} parameter introduces commands that may be
35753 run on the target, rather than being reported back to @value{GDBN}.
35754 The parameter starts with a numeric flag @var{persist}; if the flag is
35755 nonzero, then the breakpoint may remain active and the commands
35756 continue to be run even when @value{GDBN} disconnects from the target.
35757 Following this flag is a series of expressions concatenated with no
35758 separators. Each expression has the following form:
35762 @item X @var{len},@var{expr}
35763 @var{len} is the length of the bytecode expression and @var{expr} is the
35764 actual conditional expression in bytecode form.
35768 see @ref{Architecture-Specific Protocol Details}.
35770 @emph{Implementation note: It is possible for a target to copy or move
35771 code that contains memory breakpoints (e.g., when implementing
35772 overlays). The behavior of this packet, in the presence of such a
35773 target, is not defined.}
35785 @item z1,@var{addr},@var{kind}
35786 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
35787 @cindex @samp{z1} packet
35788 @cindex @samp{Z1} packet
35789 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
35790 address @var{addr}.
35792 A hardware breakpoint is implemented using a mechanism that is not
35793 dependant on being able to modify the target's memory. The @var{kind}
35794 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
35796 @emph{Implementation note: A hardware breakpoint is not affected by code
35809 @item z2,@var{addr},@var{kind}
35810 @itemx Z2,@var{addr},@var{kind}
35811 @cindex @samp{z2} packet
35812 @cindex @samp{Z2} packet
35813 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
35814 The number of bytes to watch is specified by @var{kind}.
35826 @item z3,@var{addr},@var{kind}
35827 @itemx Z3,@var{addr},@var{kind}
35828 @cindex @samp{z3} packet
35829 @cindex @samp{Z3} packet
35830 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
35831 The number of bytes to watch is specified by @var{kind}.
35843 @item z4,@var{addr},@var{kind}
35844 @itemx Z4,@var{addr},@var{kind}
35845 @cindex @samp{z4} packet
35846 @cindex @samp{Z4} packet
35847 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
35848 The number of bytes to watch is specified by @var{kind}.
35862 @node Stop Reply Packets
35863 @section Stop Reply Packets
35864 @cindex stop reply packets
35866 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
35867 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
35868 receive any of the below as a reply. Except for @samp{?}
35869 and @samp{vStopped}, that reply is only returned
35870 when the target halts. In the below the exact meaning of @dfn{signal
35871 number} is defined by the header @file{include/gdb/signals.h} in the
35872 @value{GDBN} source code.
35874 As in the description of request packets, we include spaces in the
35875 reply templates for clarity; these are not part of the reply packet's
35876 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
35882 The program received signal number @var{AA} (a two-digit hexadecimal
35883 number). This is equivalent to a @samp{T} response with no
35884 @var{n}:@var{r} pairs.
35886 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
35887 @cindex @samp{T} packet reply
35888 The program received signal number @var{AA} (a two-digit hexadecimal
35889 number). This is equivalent to an @samp{S} response, except that the
35890 @samp{@var{n}:@var{r}} pairs can carry values of important registers
35891 and other information directly in the stop reply packet, reducing
35892 round-trip latency. Single-step and breakpoint traps are reported
35893 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
35897 If @var{n} is a hexadecimal number, it is a register number, and the
35898 corresponding @var{r} gives that register's value. The data @var{r} is a
35899 series of bytes in target byte order, with each byte given by a
35900 two-digit hex number.
35903 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
35904 the stopped thread, as specified in @ref{thread-id syntax}.
35907 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
35908 the core on which the stop event was detected.
35911 If @var{n} is a recognized @dfn{stop reason}, it describes a more
35912 specific event that stopped the target. The currently defined stop
35913 reasons are listed below. The @var{aa} should be @samp{05}, the trap
35914 signal. At most one stop reason should be present.
35917 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
35918 and go on to the next; this allows us to extend the protocol in the
35922 The currently defined stop reasons are:
35928 The packet indicates a watchpoint hit, and @var{r} is the data address, in
35931 @item syscall_entry
35932 @itemx syscall_return
35933 The packet indicates a syscall entry or return, and @var{r} is the
35934 syscall number, in hex.
35936 @cindex shared library events, remote reply
35938 The packet indicates that the loaded libraries have changed.
35939 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
35940 list of loaded libraries. The @var{r} part is ignored.
35942 @cindex replay log events, remote reply
35944 The packet indicates that the target cannot continue replaying
35945 logged execution events, because it has reached the end (or the
35946 beginning when executing backward) of the log. The value of @var{r}
35947 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
35948 for more information.
35951 @anchor{swbreak stop reason}
35952 The packet indicates a memory breakpoint instruction was executed,
35953 irrespective of whether it was @value{GDBN} that planted the
35954 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
35955 part must be left empty.
35957 On some architectures, such as x86, at the architecture level, when a
35958 breakpoint instruction executes the program counter points at the
35959 breakpoint address plus an offset. On such targets, the stub is
35960 responsible for adjusting the PC to point back at the breakpoint
35963 This packet should not be sent by default; older @value{GDBN} versions
35964 did not support it. @value{GDBN} requests it, by supplying an
35965 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35966 remote stub must also supply the appropriate @samp{qSupported} feature
35967 indicating support.
35969 This packet is required for correct non-stop mode operation.
35972 The packet indicates the target stopped for a hardware breakpoint.
35973 The @var{r} part must be left empty.
35975 The same remarks about @samp{qSupported} and non-stop mode above
35978 @cindex fork events, remote reply
35980 The packet indicates that @code{fork} was called, and @var{r}
35981 is the thread ID of the new child process. Refer to
35982 @ref{thread-id syntax} for the format of the @var{thread-id}
35983 field. This packet is only applicable to targets that support
35986 This packet should not be sent by default; older @value{GDBN} versions
35987 did not support it. @value{GDBN} requests it, by supplying an
35988 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35989 remote stub must also supply the appropriate @samp{qSupported} feature
35990 indicating support.
35992 @cindex vfork events, remote reply
35994 The packet indicates that @code{vfork} was called, and @var{r}
35995 is the thread ID of the new child process. Refer to
35996 @ref{thread-id syntax} for the format of the @var{thread-id}
35997 field. This packet is only applicable to targets that support
36000 This packet should not be sent by default; older @value{GDBN} versions
36001 did not support it. @value{GDBN} requests it, by supplying an
36002 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36003 remote stub must also supply the appropriate @samp{qSupported} feature
36004 indicating support.
36006 @cindex vforkdone events, remote reply
36008 The packet indicates that a child process created by a vfork
36009 has either called @code{exec} or terminated, so that the
36010 address spaces of the parent and child process are no longer
36011 shared. The @var{r} part is ignored. This packet is only
36012 applicable to targets that support vforkdone events.
36014 This packet should not be sent by default; older @value{GDBN} versions
36015 did not support it. @value{GDBN} requests it, by supplying an
36016 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36017 remote stub must also supply the appropriate @samp{qSupported} feature
36018 indicating support.
36020 @cindex exec events, remote reply
36022 The packet indicates that @code{execve} was called, and @var{r}
36023 is the absolute pathname of the file that was executed, in hex.
36024 This packet is only applicable to targets that support exec events.
36026 This packet should not be sent by default; older @value{GDBN} versions
36027 did not support it. @value{GDBN} requests it, by supplying an
36028 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36029 remote stub must also supply the appropriate @samp{qSupported} feature
36030 indicating support.
36032 @cindex thread create event, remote reply
36033 @anchor{thread create event}
36035 The packet indicates that the thread was just created. The new thread
36036 is stopped until @value{GDBN} sets it running with a resumption packet
36037 (@pxref{vCont packet}). This packet should not be sent by default;
36038 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
36039 also the @samp{w} (@ref{thread exit event}) remote reply below.
36044 @itemx W @var{AA} ; process:@var{pid}
36045 The process exited, and @var{AA} is the exit status. This is only
36046 applicable to certain targets.
36048 The second form of the response, including the process ID of the exited
36049 process, can be used only when @value{GDBN} has reported support for
36050 multiprocess protocol extensions; see @ref{multiprocess extensions}.
36051 The @var{pid} is formatted as a big-endian hex string.
36054 @itemx X @var{AA} ; process:@var{pid}
36055 The process terminated with signal @var{AA}.
36057 The second form of the response, including the process ID of the
36058 terminated process, can be used only when @value{GDBN} has reported
36059 support for multiprocess protocol extensions; see @ref{multiprocess
36060 extensions}. The @var{pid} is formatted as a big-endian hex string.
36062 @anchor{thread exit event}
36063 @cindex thread exit event, remote reply
36064 @item w @var{AA} ; @var{tid}
36066 The thread exited, and @var{AA} is the exit status. This response
36067 should not be sent by default; @value{GDBN} requests it with the
36068 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
36071 There are no resumed threads left in the target. In other words, even
36072 though the process is alive, the last resumed thread has exited. For
36073 example, say the target process has two threads: thread 1 and thread
36074 2. The client leaves thread 1 stopped, and resumes thread 2, which
36075 subsequently exits. At this point, even though the process is still
36076 alive, and thus no @samp{W} stop reply is sent, no thread is actually
36077 executing either. The @samp{N} stop reply thus informs the client
36078 that it can stop waiting for stop replies. This packet should not be
36079 sent by default; older @value{GDBN} versions did not support it.
36080 @value{GDBN} requests it, by supplying an appropriate
36081 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
36082 also supply the appropriate @samp{qSupported} feature indicating
36085 @item O @var{XX}@dots{}
36086 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
36087 written as the program's console output. This can happen at any time
36088 while the program is running and the debugger should continue to wait
36089 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
36091 @item F @var{call-id},@var{parameter}@dots{}
36092 @var{call-id} is the identifier which says which host system call should
36093 be called. This is just the name of the function. Translation into the
36094 correct system call is only applicable as it's defined in @value{GDBN}.
36095 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
36098 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
36099 this very system call.
36101 The target replies with this packet when it expects @value{GDBN} to
36102 call a host system call on behalf of the target. @value{GDBN} replies
36103 with an appropriate @samp{F} packet and keeps up waiting for the next
36104 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
36105 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
36106 Protocol Extension}, for more details.
36110 @node General Query Packets
36111 @section General Query Packets
36112 @cindex remote query requests
36114 Packets starting with @samp{q} are @dfn{general query packets};
36115 packets starting with @samp{Q} are @dfn{general set packets}. General
36116 query and set packets are a semi-unified form for retrieving and
36117 sending information to and from the stub.
36119 The initial letter of a query or set packet is followed by a name
36120 indicating what sort of thing the packet applies to. For example,
36121 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
36122 definitions with the stub. These packet names follow some
36127 The name must not contain commas, colons or semicolons.
36129 Most @value{GDBN} query and set packets have a leading upper case
36132 The names of custom vendor packets should use a company prefix, in
36133 lower case, followed by a period. For example, packets designed at
36134 the Acme Corporation might begin with @samp{qacme.foo} (for querying
36135 foos) or @samp{Qacme.bar} (for setting bars).
36138 The name of a query or set packet should be separated from any
36139 parameters by a @samp{:}; the parameters themselves should be
36140 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
36141 full packet name, and check for a separator or the end of the packet,
36142 in case two packet names share a common prefix. New packets should not begin
36143 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
36144 packets predate these conventions, and have arguments without any terminator
36145 for the packet name; we suspect they are in widespread use in places that
36146 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
36147 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
36150 Like the descriptions of the other packets, each description here
36151 has a template showing the packet's overall syntax, followed by an
36152 explanation of the packet's meaning. We include spaces in some of the
36153 templates for clarity; these are not part of the packet's syntax. No
36154 @value{GDBN} packet uses spaces to separate its components.
36156 Here are the currently defined query and set packets:
36162 Turn on or off the agent as a helper to perform some debugging operations
36163 delegated from @value{GDBN} (@pxref{Control Agent}).
36165 @item QAllow:@var{op}:@var{val}@dots{}
36166 @cindex @samp{QAllow} packet
36167 Specify which operations @value{GDBN} expects to request of the
36168 target, as a semicolon-separated list of operation name and value
36169 pairs. Possible values for @var{op} include @samp{WriteReg},
36170 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
36171 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
36172 indicating that @value{GDBN} will not request the operation, or 1,
36173 indicating that it may. (The target can then use this to set up its
36174 own internals optimally, for instance if the debugger never expects to
36175 insert breakpoints, it may not need to install its own trap handler.)
36178 @cindex current thread, remote request
36179 @cindex @samp{qC} packet
36180 Return the current thread ID.
36184 @item QC @var{thread-id}
36185 Where @var{thread-id} is a thread ID as documented in
36186 @ref{thread-id syntax}.
36187 @item @r{(anything else)}
36188 Any other reply implies the old thread ID.
36191 @item qCRC:@var{addr},@var{length}
36192 @cindex CRC of memory block, remote request
36193 @cindex @samp{qCRC} packet
36194 @anchor{qCRC packet}
36195 Compute the CRC checksum of a block of memory using CRC-32 defined in
36196 IEEE 802.3. The CRC is computed byte at a time, taking the most
36197 significant bit of each byte first. The initial pattern code
36198 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
36200 @emph{Note:} This is the same CRC used in validating separate debug
36201 files (@pxref{Separate Debug Files, , Debugging Information in Separate
36202 Files}). However the algorithm is slightly different. When validating
36203 separate debug files, the CRC is computed taking the @emph{least}
36204 significant bit of each byte first, and the final result is inverted to
36205 detect trailing zeros.
36210 An error (such as memory fault)
36211 @item C @var{crc32}
36212 The specified memory region's checksum is @var{crc32}.
36215 @item QDisableRandomization:@var{value}
36216 @cindex disable address space randomization, remote request
36217 @cindex @samp{QDisableRandomization} packet
36218 Some target operating systems will randomize the virtual address space
36219 of the inferior process as a security feature, but provide a feature
36220 to disable such randomization, e.g.@: to allow for a more deterministic
36221 debugging experience. On such systems, this packet with a @var{value}
36222 of 1 directs the target to disable address space randomization for
36223 processes subsequently started via @samp{vRun} packets, while a packet
36224 with a @var{value} of 0 tells the target to enable address space
36227 This packet is only available in extended mode (@pxref{extended mode}).
36232 The request succeeded.
36235 An error occurred. The error number @var{nn} is given as hex digits.
36238 An empty reply indicates that @samp{QDisableRandomization} is not supported
36242 This packet is not probed by default; the remote stub must request it,
36243 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36244 This should only be done on targets that actually support disabling
36245 address space randomization.
36248 @itemx qsThreadInfo
36249 @cindex list active threads, remote request
36250 @cindex @samp{qfThreadInfo} packet
36251 @cindex @samp{qsThreadInfo} packet
36252 Obtain a list of all active thread IDs from the target (OS). Since there
36253 may be too many active threads to fit into one reply packet, this query
36254 works iteratively: it may require more than one query/reply sequence to
36255 obtain the entire list of threads. The first query of the sequence will
36256 be the @samp{qfThreadInfo} query; subsequent queries in the
36257 sequence will be the @samp{qsThreadInfo} query.
36259 NOTE: This packet replaces the @samp{qL} query (see below).
36263 @item m @var{thread-id}
36265 @item m @var{thread-id},@var{thread-id}@dots{}
36266 a comma-separated list of thread IDs
36268 (lower case letter @samp{L}) denotes end of list.
36271 In response to each query, the target will reply with a list of one or
36272 more thread IDs, separated by commas.
36273 @value{GDBN} will respond to each reply with a request for more thread
36274 ids (using the @samp{qs} form of the query), until the target responds
36275 with @samp{l} (lower-case ell, for @dfn{last}).
36276 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
36279 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
36280 initial connection with the remote target, and the very first thread ID
36281 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
36282 message. Therefore, the stub should ensure that the first thread ID in
36283 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
36285 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
36286 @cindex get thread-local storage address, remote request
36287 @cindex @samp{qGetTLSAddr} packet
36288 Fetch the address associated with thread local storage specified
36289 by @var{thread-id}, @var{offset}, and @var{lm}.
36291 @var{thread-id} is the thread ID associated with the
36292 thread for which to fetch the TLS address. @xref{thread-id syntax}.
36294 @var{offset} is the (big endian, hex encoded) offset associated with the
36295 thread local variable. (This offset is obtained from the debug
36296 information associated with the variable.)
36298 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
36299 load module associated with the thread local storage. For example,
36300 a @sc{gnu}/Linux system will pass the link map address of the shared
36301 object associated with the thread local storage under consideration.
36302 Other operating environments may choose to represent the load module
36303 differently, so the precise meaning of this parameter will vary.
36307 @item @var{XX}@dots{}
36308 Hex encoded (big endian) bytes representing the address of the thread
36309 local storage requested.
36312 An error occurred. The error number @var{nn} is given as hex digits.
36315 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
36318 @item qGetTIBAddr:@var{thread-id}
36319 @cindex get thread information block address
36320 @cindex @samp{qGetTIBAddr} packet
36321 Fetch address of the Windows OS specific Thread Information Block.
36323 @var{thread-id} is the thread ID associated with the thread.
36327 @item @var{XX}@dots{}
36328 Hex encoded (big endian) bytes representing the linear address of the
36329 thread information block.
36332 An error occured. This means that either the thread was not found, or the
36333 address could not be retrieved.
36336 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
36339 @item qL @var{startflag} @var{threadcount} @var{nextthread}
36340 Obtain thread information from RTOS. Where: @var{startflag} (one hex
36341 digit) is one to indicate the first query and zero to indicate a
36342 subsequent query; @var{threadcount} (two hex digits) is the maximum
36343 number of threads the response packet can contain; and @var{nextthread}
36344 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
36345 returned in the response as @var{argthread}.
36347 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
36351 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
36352 Where: @var{count} (two hex digits) is the number of threads being
36353 returned; @var{done} (one hex digit) is zero to indicate more threads
36354 and one indicates no further threads; @var{argthreadid} (eight hex
36355 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
36356 is a sequence of thread IDs, @var{threadid} (eight hex
36357 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
36361 @cindex section offsets, remote request
36362 @cindex @samp{qOffsets} packet
36363 Get section offsets that the target used when relocating the downloaded
36368 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
36369 Relocate the @code{Text} section by @var{xxx} from its original address.
36370 Relocate the @code{Data} section by @var{yyy} from its original address.
36371 If the object file format provides segment information (e.g.@: @sc{elf}
36372 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
36373 segments by the supplied offsets.
36375 @emph{Note: while a @code{Bss} offset may be included in the response,
36376 @value{GDBN} ignores this and instead applies the @code{Data} offset
36377 to the @code{Bss} section.}
36379 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
36380 Relocate the first segment of the object file, which conventionally
36381 contains program code, to a starting address of @var{xxx}. If
36382 @samp{DataSeg} is specified, relocate the second segment, which
36383 conventionally contains modifiable data, to a starting address of
36384 @var{yyy}. @value{GDBN} will report an error if the object file
36385 does not contain segment information, or does not contain at least
36386 as many segments as mentioned in the reply. Extra segments are
36387 kept at fixed offsets relative to the last relocated segment.
36390 @item qP @var{mode} @var{thread-id}
36391 @cindex thread information, remote request
36392 @cindex @samp{qP} packet
36393 Returns information on @var{thread-id}. Where: @var{mode} is a hex
36394 encoded 32 bit mode; @var{thread-id} is a thread ID
36395 (@pxref{thread-id syntax}).
36397 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
36400 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
36404 @cindex non-stop mode, remote request
36405 @cindex @samp{QNonStop} packet
36407 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
36408 @xref{Remote Non-Stop}, for more information.
36413 The request succeeded.
36416 An error occurred. The error number @var{nn} is given as hex digits.
36419 An empty reply indicates that @samp{QNonStop} is not supported by
36423 This packet is not probed by default; the remote stub must request it,
36424 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36425 Use of this packet is controlled by the @code{set non-stop} command;
36426 @pxref{Non-Stop Mode}.
36428 @item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
36429 @itemx QCatchSyscalls:0
36430 @cindex catch syscalls from inferior, remote request
36431 @cindex @samp{QCatchSyscalls} packet
36432 @anchor{QCatchSyscalls}
36433 Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
36434 catching syscalls from the inferior process.
36436 For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
36437 in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
36438 is listed, every system call should be reported.
36440 Note that if a syscall not in the list is reported, @value{GDBN} will
36441 still filter the event according to its own list from all corresponding
36442 @code{catch syscall} commands. However, it is more efficient to only
36443 report the requested syscalls.
36445 Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
36446 @samp{QCatchSyscalls:1} list is completely replaced by the new list.
36448 If the inferior process execs, the state of @samp{QCatchSyscalls} is
36449 kept for the new process too. On targets where exec may affect syscall
36450 numbers, for example with exec between 32 and 64-bit processes, the
36451 client should send a new packet with the new syscall list.
36456 The request succeeded.
36459 An error occurred. @var{nn} are hex digits.
36462 An empty reply indicates that @samp{QCatchSyscalls} is not supported by
36466 Use of this packet is controlled by the @code{set remote catch-syscalls}
36467 command (@pxref{Remote Configuration, set remote catch-syscalls}).
36468 This packet is not probed by default; the remote stub must request it,
36469 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36471 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
36472 @cindex pass signals to inferior, remote request
36473 @cindex @samp{QPassSignals} packet
36474 @anchor{QPassSignals}
36475 Each listed @var{signal} should be passed directly to the inferior process.
36476 Signals are numbered identically to continue packets and stop replies
36477 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
36478 strictly greater than the previous item. These signals do not need to stop
36479 the inferior, or be reported to @value{GDBN}. All other signals should be
36480 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
36481 combine; any earlier @samp{QPassSignals} list is completely replaced by the
36482 new list. This packet improves performance when using @samp{handle
36483 @var{signal} nostop noprint pass}.
36488 The request succeeded.
36491 An error occurred. The error number @var{nn} is given as hex digits.
36494 An empty reply indicates that @samp{QPassSignals} is not supported by
36498 Use of this packet is controlled by the @code{set remote pass-signals}
36499 command (@pxref{Remote Configuration, set remote pass-signals}).
36500 This packet is not probed by default; the remote stub must request it,
36501 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36503 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
36504 @cindex signals the inferior may see, remote request
36505 @cindex @samp{QProgramSignals} packet
36506 @anchor{QProgramSignals}
36507 Each listed @var{signal} may be delivered to the inferior process.
36508 Others should be silently discarded.
36510 In some cases, the remote stub may need to decide whether to deliver a
36511 signal to the program or not without @value{GDBN} involvement. One
36512 example of that is while detaching --- the program's threads may have
36513 stopped for signals that haven't yet had a chance of being reported to
36514 @value{GDBN}, and so the remote stub can use the signal list specified
36515 by this packet to know whether to deliver or ignore those pending
36518 This does not influence whether to deliver a signal as requested by a
36519 resumption packet (@pxref{vCont packet}).
36521 Signals are numbered identically to continue packets and stop replies
36522 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
36523 strictly greater than the previous item. Multiple
36524 @samp{QProgramSignals} packets do not combine; any earlier
36525 @samp{QProgramSignals} list is completely replaced by the new list.
36530 The request succeeded.
36533 An error occurred. The error number @var{nn} is given as hex digits.
36536 An empty reply indicates that @samp{QProgramSignals} is not supported
36540 Use of this packet is controlled by the @code{set remote program-signals}
36541 command (@pxref{Remote Configuration, set remote program-signals}).
36542 This packet is not probed by default; the remote stub must request it,
36543 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36545 @anchor{QThreadEvents}
36546 @item QThreadEvents:1
36547 @itemx QThreadEvents:0
36548 @cindex thread create/exit events, remote request
36549 @cindex @samp{QThreadEvents} packet
36551 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
36552 reporting of thread create and exit events. @xref{thread create
36553 event}, for the reply specifications. For example, this is used in
36554 non-stop mode when @value{GDBN} stops a set of threads and
36555 synchronously waits for the their corresponding stop replies. Without
36556 exit events, if one of the threads exits, @value{GDBN} would hang
36557 forever not knowing that it should no longer expect a stop for that
36558 same thread. @value{GDBN} does not enable this feature unless the
36559 stub reports that it supports it by including @samp{QThreadEvents+} in
36560 its @samp{qSupported} reply.
36565 The request succeeded.
36568 An error occurred. The error number @var{nn} is given as hex digits.
36571 An empty reply indicates that @samp{QThreadEvents} is not supported by
36575 Use of this packet is controlled by the @code{set remote thread-events}
36576 command (@pxref{Remote Configuration, set remote thread-events}).
36578 @item qRcmd,@var{command}
36579 @cindex execute remote command, remote request
36580 @cindex @samp{qRcmd} packet
36581 @var{command} (hex encoded) is passed to the local interpreter for
36582 execution. Invalid commands should be reported using the output
36583 string. Before the final result packet, the target may also respond
36584 with a number of intermediate @samp{O@var{output}} console output
36585 packets. @emph{Implementors should note that providing access to a
36586 stubs's interpreter may have security implications}.
36591 A command response with no output.
36593 A command response with the hex encoded output string @var{OUTPUT}.
36595 Indicate a badly formed request.
36597 An empty reply indicates that @samp{qRcmd} is not recognized.
36600 (Note that the @code{qRcmd} packet's name is separated from the
36601 command by a @samp{,}, not a @samp{:}, contrary to the naming
36602 conventions above. Please don't use this packet as a model for new
36605 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
36606 @cindex searching memory, in remote debugging
36608 @cindex @samp{qSearch:memory} packet
36610 @cindex @samp{qSearch memory} packet
36611 @anchor{qSearch memory}
36612 Search @var{length} bytes at @var{address} for @var{search-pattern}.
36613 Both @var{address} and @var{length} are encoded in hex;
36614 @var{search-pattern} is a sequence of bytes, also hex encoded.
36619 The pattern was not found.
36621 The pattern was found at @var{address}.
36623 A badly formed request or an error was encountered while searching memory.
36625 An empty reply indicates that @samp{qSearch:memory} is not recognized.
36628 @item QStartNoAckMode
36629 @cindex @samp{QStartNoAckMode} packet
36630 @anchor{QStartNoAckMode}
36631 Request that the remote stub disable the normal @samp{+}/@samp{-}
36632 protocol acknowledgments (@pxref{Packet Acknowledgment}).
36637 The stub has switched to no-acknowledgment mode.
36638 @value{GDBN} acknowledges this reponse,
36639 but neither the stub nor @value{GDBN} shall send or expect further
36640 @samp{+}/@samp{-} acknowledgments in the current connection.
36642 An empty reply indicates that the stub does not support no-acknowledgment mode.
36645 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
36646 @cindex supported packets, remote query
36647 @cindex features of the remote protocol
36648 @cindex @samp{qSupported} packet
36649 @anchor{qSupported}
36650 Tell the remote stub about features supported by @value{GDBN}, and
36651 query the stub for features it supports. This packet allows
36652 @value{GDBN} and the remote stub to take advantage of each others'
36653 features. @samp{qSupported} also consolidates multiple feature probes
36654 at startup, to improve @value{GDBN} performance---a single larger
36655 packet performs better than multiple smaller probe packets on
36656 high-latency links. Some features may enable behavior which must not
36657 be on by default, e.g.@: because it would confuse older clients or
36658 stubs. Other features may describe packets which could be
36659 automatically probed for, but are not. These features must be
36660 reported before @value{GDBN} will use them. This ``default
36661 unsupported'' behavior is not appropriate for all packets, but it
36662 helps to keep the initial connection time under control with new
36663 versions of @value{GDBN} which support increasing numbers of packets.
36667 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
36668 The stub supports or does not support each returned @var{stubfeature},
36669 depending on the form of each @var{stubfeature} (see below for the
36672 An empty reply indicates that @samp{qSupported} is not recognized,
36673 or that no features needed to be reported to @value{GDBN}.
36676 The allowed forms for each feature (either a @var{gdbfeature} in the
36677 @samp{qSupported} packet, or a @var{stubfeature} in the response)
36681 @item @var{name}=@var{value}
36682 The remote protocol feature @var{name} is supported, and associated
36683 with the specified @var{value}. The format of @var{value} depends
36684 on the feature, but it must not include a semicolon.
36686 The remote protocol feature @var{name} is supported, and does not
36687 need an associated value.
36689 The remote protocol feature @var{name} is not supported.
36691 The remote protocol feature @var{name} may be supported, and
36692 @value{GDBN} should auto-detect support in some other way when it is
36693 needed. This form will not be used for @var{gdbfeature} notifications,
36694 but may be used for @var{stubfeature} responses.
36697 Whenever the stub receives a @samp{qSupported} request, the
36698 supplied set of @value{GDBN} features should override any previous
36699 request. This allows @value{GDBN} to put the stub in a known
36700 state, even if the stub had previously been communicating with
36701 a different version of @value{GDBN}.
36703 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
36708 This feature indicates whether @value{GDBN} supports multiprocess
36709 extensions to the remote protocol. @value{GDBN} does not use such
36710 extensions unless the stub also reports that it supports them by
36711 including @samp{multiprocess+} in its @samp{qSupported} reply.
36712 @xref{multiprocess extensions}, for details.
36715 This feature indicates that @value{GDBN} supports the XML target
36716 description. If the stub sees @samp{xmlRegisters=} with target
36717 specific strings separated by a comma, it will report register
36721 This feature indicates whether @value{GDBN} supports the
36722 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
36723 instruction reply packet}).
36726 This feature indicates whether @value{GDBN} supports the swbreak stop
36727 reason in stop replies. @xref{swbreak stop reason}, for details.
36730 This feature indicates whether @value{GDBN} supports the hwbreak stop
36731 reason in stop replies. @xref{swbreak stop reason}, for details.
36734 This feature indicates whether @value{GDBN} supports fork event
36735 extensions to the remote protocol. @value{GDBN} does not use such
36736 extensions unless the stub also reports that it supports them by
36737 including @samp{fork-events+} in its @samp{qSupported} reply.
36740 This feature indicates whether @value{GDBN} supports vfork event
36741 extensions to the remote protocol. @value{GDBN} does not use such
36742 extensions unless the stub also reports that it supports them by
36743 including @samp{vfork-events+} in its @samp{qSupported} reply.
36746 This feature indicates whether @value{GDBN} supports exec event
36747 extensions to the remote protocol. @value{GDBN} does not use such
36748 extensions unless the stub also reports that it supports them by
36749 including @samp{exec-events+} in its @samp{qSupported} reply.
36751 @item vContSupported
36752 This feature indicates whether @value{GDBN} wants to know the
36753 supported actions in the reply to @samp{vCont?} packet.
36756 Stubs should ignore any unknown values for
36757 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
36758 packet supports receiving packets of unlimited length (earlier
36759 versions of @value{GDBN} may reject overly long responses). Additional values
36760 for @var{gdbfeature} may be defined in the future to let the stub take
36761 advantage of new features in @value{GDBN}, e.g.@: incompatible
36762 improvements in the remote protocol---the @samp{multiprocess} feature is
36763 an example of such a feature. The stub's reply should be independent
36764 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
36765 describes all the features it supports, and then the stub replies with
36766 all the features it supports.
36768 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
36769 responses, as long as each response uses one of the standard forms.
36771 Some features are flags. A stub which supports a flag feature
36772 should respond with a @samp{+} form response. Other features
36773 require values, and the stub should respond with an @samp{=}
36776 Each feature has a default value, which @value{GDBN} will use if
36777 @samp{qSupported} is not available or if the feature is not mentioned
36778 in the @samp{qSupported} response. The default values are fixed; a
36779 stub is free to omit any feature responses that match the defaults.
36781 Not all features can be probed, but for those which can, the probing
36782 mechanism is useful: in some cases, a stub's internal
36783 architecture may not allow the protocol layer to know some information
36784 about the underlying target in advance. This is especially common in
36785 stubs which may be configured for multiple targets.
36787 These are the currently defined stub features and their properties:
36789 @multitable @columnfractions 0.35 0.2 0.12 0.2
36790 @c NOTE: The first row should be @headitem, but we do not yet require
36791 @c a new enough version of Texinfo (4.7) to use @headitem.
36793 @tab Value Required
36797 @item @samp{PacketSize}
36802 @item @samp{qXfer:auxv:read}
36807 @item @samp{qXfer:btrace:read}
36812 @item @samp{qXfer:btrace-conf:read}
36817 @item @samp{qXfer:exec-file:read}
36822 @item @samp{qXfer:features:read}
36827 @item @samp{qXfer:libraries:read}
36832 @item @samp{qXfer:libraries-svr4:read}
36837 @item @samp{augmented-libraries-svr4-read}
36842 @item @samp{qXfer:memory-map:read}
36847 @item @samp{qXfer:sdata:read}
36852 @item @samp{qXfer:spu:read}
36857 @item @samp{qXfer:spu:write}
36862 @item @samp{qXfer:siginfo:read}
36867 @item @samp{qXfer:siginfo:write}
36872 @item @samp{qXfer:threads:read}
36877 @item @samp{qXfer:traceframe-info:read}
36882 @item @samp{qXfer:uib:read}
36887 @item @samp{qXfer:fdpic:read}
36892 @item @samp{Qbtrace:off}
36897 @item @samp{Qbtrace:bts}
36902 @item @samp{Qbtrace:pt}
36907 @item @samp{Qbtrace-conf:bts:size}
36912 @item @samp{Qbtrace-conf:pt:size}
36917 @item @samp{QNonStop}
36922 @item @samp{QCatchSyscalls}
36927 @item @samp{QPassSignals}
36932 @item @samp{QStartNoAckMode}
36937 @item @samp{multiprocess}
36942 @item @samp{ConditionalBreakpoints}
36947 @item @samp{ConditionalTracepoints}
36952 @item @samp{ReverseContinue}
36957 @item @samp{ReverseStep}
36962 @item @samp{TracepointSource}
36967 @item @samp{QAgent}
36972 @item @samp{QAllow}
36977 @item @samp{QDisableRandomization}
36982 @item @samp{EnableDisableTracepoints}
36987 @item @samp{QTBuffer:size}
36992 @item @samp{tracenz}
36997 @item @samp{BreakpointCommands}
37002 @item @samp{swbreak}
37007 @item @samp{hwbreak}
37012 @item @samp{fork-events}
37017 @item @samp{vfork-events}
37022 @item @samp{exec-events}
37027 @item @samp{QThreadEvents}
37032 @item @samp{no-resumed}
37039 These are the currently defined stub features, in more detail:
37042 @cindex packet size, remote protocol
37043 @item PacketSize=@var{bytes}
37044 The remote stub can accept packets up to at least @var{bytes} in
37045 length. @value{GDBN} will send packets up to this size for bulk
37046 transfers, and will never send larger packets. This is a limit on the
37047 data characters in the packet, including the frame and checksum.
37048 There is no trailing NUL byte in a remote protocol packet; if the stub
37049 stores packets in a NUL-terminated format, it should allow an extra
37050 byte in its buffer for the NUL. If this stub feature is not supported,
37051 @value{GDBN} guesses based on the size of the @samp{g} packet response.
37053 @item qXfer:auxv:read
37054 The remote stub understands the @samp{qXfer:auxv:read} packet
37055 (@pxref{qXfer auxiliary vector read}).
37057 @item qXfer:btrace:read
37058 The remote stub understands the @samp{qXfer:btrace:read}
37059 packet (@pxref{qXfer btrace read}).
37061 @item qXfer:btrace-conf:read
37062 The remote stub understands the @samp{qXfer:btrace-conf:read}
37063 packet (@pxref{qXfer btrace-conf read}).
37065 @item qXfer:exec-file:read
37066 The remote stub understands the @samp{qXfer:exec-file:read} packet
37067 (@pxref{qXfer executable filename read}).
37069 @item qXfer:features:read
37070 The remote stub understands the @samp{qXfer:features:read} packet
37071 (@pxref{qXfer target description read}).
37073 @item qXfer:libraries:read
37074 The remote stub understands the @samp{qXfer:libraries:read} packet
37075 (@pxref{qXfer library list read}).
37077 @item qXfer:libraries-svr4:read
37078 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
37079 (@pxref{qXfer svr4 library list read}).
37081 @item augmented-libraries-svr4-read
37082 The remote stub understands the augmented form of the
37083 @samp{qXfer:libraries-svr4:read} packet
37084 (@pxref{qXfer svr4 library list read}).
37086 @item qXfer:memory-map:read
37087 The remote stub understands the @samp{qXfer:memory-map:read} packet
37088 (@pxref{qXfer memory map read}).
37090 @item qXfer:sdata:read
37091 The remote stub understands the @samp{qXfer:sdata:read} packet
37092 (@pxref{qXfer sdata read}).
37094 @item qXfer:spu:read
37095 The remote stub understands the @samp{qXfer:spu:read} packet
37096 (@pxref{qXfer spu read}).
37098 @item qXfer:spu:write
37099 The remote stub understands the @samp{qXfer:spu:write} packet
37100 (@pxref{qXfer spu write}).
37102 @item qXfer:siginfo:read
37103 The remote stub understands the @samp{qXfer:siginfo:read} packet
37104 (@pxref{qXfer siginfo read}).
37106 @item qXfer:siginfo:write
37107 The remote stub understands the @samp{qXfer:siginfo:write} packet
37108 (@pxref{qXfer siginfo write}).
37110 @item qXfer:threads:read
37111 The remote stub understands the @samp{qXfer:threads:read} packet
37112 (@pxref{qXfer threads read}).
37114 @item qXfer:traceframe-info:read
37115 The remote stub understands the @samp{qXfer:traceframe-info:read}
37116 packet (@pxref{qXfer traceframe info read}).
37118 @item qXfer:uib:read
37119 The remote stub understands the @samp{qXfer:uib:read}
37120 packet (@pxref{qXfer unwind info block}).
37122 @item qXfer:fdpic:read
37123 The remote stub understands the @samp{qXfer:fdpic:read}
37124 packet (@pxref{qXfer fdpic loadmap read}).
37127 The remote stub understands the @samp{QNonStop} packet
37128 (@pxref{QNonStop}).
37130 @item QCatchSyscalls
37131 The remote stub understands the @samp{QCatchSyscalls} packet
37132 (@pxref{QCatchSyscalls}).
37135 The remote stub understands the @samp{QPassSignals} packet
37136 (@pxref{QPassSignals}).
37138 @item QStartNoAckMode
37139 The remote stub understands the @samp{QStartNoAckMode} packet and
37140 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
37143 @anchor{multiprocess extensions}
37144 @cindex multiprocess extensions, in remote protocol
37145 The remote stub understands the multiprocess extensions to the remote
37146 protocol syntax. The multiprocess extensions affect the syntax of
37147 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
37148 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
37149 replies. Note that reporting this feature indicates support for the
37150 syntactic extensions only, not that the stub necessarily supports
37151 debugging of more than one process at a time. The stub must not use
37152 multiprocess extensions in packet replies unless @value{GDBN} has also
37153 indicated it supports them in its @samp{qSupported} request.
37155 @item qXfer:osdata:read
37156 The remote stub understands the @samp{qXfer:osdata:read} packet
37157 ((@pxref{qXfer osdata read}).
37159 @item ConditionalBreakpoints
37160 The target accepts and implements evaluation of conditional expressions
37161 defined for breakpoints. The target will only report breakpoint triggers
37162 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
37164 @item ConditionalTracepoints
37165 The remote stub accepts and implements conditional expressions defined
37166 for tracepoints (@pxref{Tracepoint Conditions}).
37168 @item ReverseContinue
37169 The remote stub accepts and implements the reverse continue packet
37173 The remote stub accepts and implements the reverse step packet
37176 @item TracepointSource
37177 The remote stub understands the @samp{QTDPsrc} packet that supplies
37178 the source form of tracepoint definitions.
37181 The remote stub understands the @samp{QAgent} packet.
37184 The remote stub understands the @samp{QAllow} packet.
37186 @item QDisableRandomization
37187 The remote stub understands the @samp{QDisableRandomization} packet.
37189 @item StaticTracepoint
37190 @cindex static tracepoints, in remote protocol
37191 The remote stub supports static tracepoints.
37193 @item InstallInTrace
37194 @anchor{install tracepoint in tracing}
37195 The remote stub supports installing tracepoint in tracing.
37197 @item EnableDisableTracepoints
37198 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
37199 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
37200 to be enabled and disabled while a trace experiment is running.
37202 @item QTBuffer:size
37203 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
37204 packet that allows to change the size of the trace buffer.
37207 @cindex string tracing, in remote protocol
37208 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
37209 See @ref{Bytecode Descriptions} for details about the bytecode.
37211 @item BreakpointCommands
37212 @cindex breakpoint commands, in remote protocol
37213 The remote stub supports running a breakpoint's command list itself,
37214 rather than reporting the hit to @value{GDBN}.
37217 The remote stub understands the @samp{Qbtrace:off} packet.
37220 The remote stub understands the @samp{Qbtrace:bts} packet.
37223 The remote stub understands the @samp{Qbtrace:pt} packet.
37225 @item Qbtrace-conf:bts:size
37226 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
37228 @item Qbtrace-conf:pt:size
37229 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
37232 The remote stub reports the @samp{swbreak} stop reason for memory
37236 The remote stub reports the @samp{hwbreak} stop reason for hardware
37240 The remote stub reports the @samp{fork} stop reason for fork events.
37243 The remote stub reports the @samp{vfork} stop reason for vfork events
37244 and vforkdone events.
37247 The remote stub reports the @samp{exec} stop reason for exec events.
37249 @item vContSupported
37250 The remote stub reports the supported actions in the reply to
37251 @samp{vCont?} packet.
37253 @item QThreadEvents
37254 The remote stub understands the @samp{QThreadEvents} packet.
37257 The remote stub reports the @samp{N} stop reply.
37262 @cindex symbol lookup, remote request
37263 @cindex @samp{qSymbol} packet
37264 Notify the target that @value{GDBN} is prepared to serve symbol lookup
37265 requests. Accept requests from the target for the values of symbols.
37270 The target does not need to look up any (more) symbols.
37271 @item qSymbol:@var{sym_name}
37272 The target requests the value of symbol @var{sym_name} (hex encoded).
37273 @value{GDBN} may provide the value by using the
37274 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
37278 @item qSymbol:@var{sym_value}:@var{sym_name}
37279 Set the value of @var{sym_name} to @var{sym_value}.
37281 @var{sym_name} (hex encoded) is the name of a symbol whose value the
37282 target has previously requested.
37284 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
37285 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
37291 The target does not need to look up any (more) symbols.
37292 @item qSymbol:@var{sym_name}
37293 The target requests the value of a new symbol @var{sym_name} (hex
37294 encoded). @value{GDBN} will continue to supply the values of symbols
37295 (if available), until the target ceases to request them.
37300 @itemx QTDisconnected
37307 @itemx qTMinFTPILen
37309 @xref{Tracepoint Packets}.
37311 @item qThreadExtraInfo,@var{thread-id}
37312 @cindex thread attributes info, remote request
37313 @cindex @samp{qThreadExtraInfo} packet
37314 Obtain from the target OS a printable string description of thread
37315 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
37316 for the forms of @var{thread-id}. This
37317 string may contain anything that the target OS thinks is interesting
37318 for @value{GDBN} to tell the user about the thread. The string is
37319 displayed in @value{GDBN}'s @code{info threads} display. Some
37320 examples of possible thread extra info strings are @samp{Runnable}, or
37321 @samp{Blocked on Mutex}.
37325 @item @var{XX}@dots{}
37326 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
37327 comprising the printable string containing the extra information about
37328 the thread's attributes.
37331 (Note that the @code{qThreadExtraInfo} packet's name is separated from
37332 the command by a @samp{,}, not a @samp{:}, contrary to the naming
37333 conventions above. Please don't use this packet as a model for new
37352 @xref{Tracepoint Packets}.
37354 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
37355 @cindex read special object, remote request
37356 @cindex @samp{qXfer} packet
37357 @anchor{qXfer read}
37358 Read uninterpreted bytes from the target's special data area
37359 identified by the keyword @var{object}. Request @var{length} bytes
37360 starting at @var{offset} bytes into the data. The content and
37361 encoding of @var{annex} is specific to @var{object}; it can supply
37362 additional details about what data to access.
37367 Data @var{data} (@pxref{Binary Data}) has been read from the
37368 target. There may be more data at a higher address (although
37369 it is permitted to return @samp{m} even for the last valid
37370 block of data, as long as at least one byte of data was read).
37371 It is possible for @var{data} to have fewer bytes than the @var{length} in the
37375 Data @var{data} (@pxref{Binary Data}) has been read from the target.
37376 There is no more data to be read. It is possible for @var{data} to
37377 have fewer bytes than the @var{length} in the request.
37380 The @var{offset} in the request is at the end of the data.
37381 There is no more data to be read.
37384 The request was malformed, or @var{annex} was invalid.
37387 The offset was invalid, or there was an error encountered reading the data.
37388 The @var{nn} part is a hex-encoded @code{errno} value.
37391 An empty reply indicates the @var{object} string was not recognized by
37392 the stub, or that the object does not support reading.
37395 Here are the specific requests of this form defined so far. All the
37396 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
37397 formats, listed above.
37400 @item qXfer:auxv:read::@var{offset},@var{length}
37401 @anchor{qXfer auxiliary vector read}
37402 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
37403 auxiliary vector}. Note @var{annex} must be empty.
37405 This packet is not probed by default; the remote stub must request it,
37406 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37408 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
37409 @anchor{qXfer btrace read}
37411 Return a description of the current branch trace.
37412 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
37413 packet may have one of the following values:
37417 Returns all available branch trace.
37420 Returns all available branch trace if the branch trace changed since
37421 the last read request.
37424 Returns the new branch trace since the last read request. Adds a new
37425 block to the end of the trace that begins at zero and ends at the source
37426 location of the first branch in the trace buffer. This extra block is
37427 used to stitch traces together.
37429 If the trace buffer overflowed, returns an error indicating the overflow.
37432 This packet is not probed by default; the remote stub must request it
37433 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37435 @item qXfer:btrace-conf:read::@var{offset},@var{length}
37436 @anchor{qXfer btrace-conf read}
37438 Return a description of the current branch trace configuration.
37439 @xref{Branch Trace Configuration Format}.
37441 This packet is not probed by default; the remote stub must request it
37442 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37444 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
37445 @anchor{qXfer executable filename read}
37446 Return the full absolute name of the file that was executed to create
37447 a process running on the remote system. The annex specifies the
37448 numeric process ID of the process to query, encoded as a hexadecimal
37449 number. If the annex part is empty the remote stub should return the
37450 filename corresponding to the currently executing process.
37452 This packet is not probed by default; the remote stub must request it,
37453 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37455 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
37456 @anchor{qXfer target description read}
37457 Access the @dfn{target description}. @xref{Target Descriptions}. The
37458 annex specifies which XML document to access. The main description is
37459 always loaded from the @samp{target.xml} annex.
37461 This packet is not probed by default; the remote stub must request it,
37462 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37464 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
37465 @anchor{qXfer library list read}
37466 Access the target's list of loaded libraries. @xref{Library List Format}.
37467 The annex part of the generic @samp{qXfer} packet must be empty
37468 (@pxref{qXfer read}).
37470 Targets which maintain a list of libraries in the program's memory do
37471 not need to implement this packet; it is designed for platforms where
37472 the operating system manages the list of loaded libraries.
37474 This packet is not probed by default; the remote stub must request it,
37475 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37477 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
37478 @anchor{qXfer svr4 library list read}
37479 Access the target's list of loaded libraries when the target is an SVR4
37480 platform. @xref{Library List Format for SVR4 Targets}. The annex part
37481 of the generic @samp{qXfer} packet must be empty unless the remote
37482 stub indicated it supports the augmented form of this packet
37483 by supplying an appropriate @samp{qSupported} response
37484 (@pxref{qXfer read}, @ref{qSupported}).
37486 This packet is optional for better performance on SVR4 targets.
37487 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
37489 This packet is not probed by default; the remote stub must request it,
37490 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37492 If the remote stub indicates it supports the augmented form of this
37493 packet then the annex part of the generic @samp{qXfer} packet may
37494 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
37495 arguments. The currently supported arguments are:
37498 @item start=@var{address}
37499 A hexadecimal number specifying the address of the @samp{struct
37500 link_map} to start reading the library list from. If unset or zero
37501 then the first @samp{struct link_map} in the library list will be
37502 chosen as the starting point.
37504 @item prev=@var{address}
37505 A hexadecimal number specifying the address of the @samp{struct
37506 link_map} immediately preceding the @samp{struct link_map}
37507 specified by the @samp{start} argument. If unset or zero then
37508 the remote stub will expect that no @samp{struct link_map}
37509 exists prior to the starting point.
37513 Arguments that are not understood by the remote stub will be silently
37516 @item qXfer:memory-map:read::@var{offset},@var{length}
37517 @anchor{qXfer memory map read}
37518 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
37519 annex part of the generic @samp{qXfer} packet must be empty
37520 (@pxref{qXfer read}).
37522 This packet is not probed by default; the remote stub must request it,
37523 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37525 @item qXfer:sdata:read::@var{offset},@var{length}
37526 @anchor{qXfer sdata read}
37528 Read contents of the extra collected static tracepoint marker
37529 information. The annex part of the generic @samp{qXfer} packet must
37530 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
37533 This packet is not probed by default; the remote stub must request it,
37534 by supplying an appropriate @samp{qSupported} response
37535 (@pxref{qSupported}).
37537 @item qXfer:siginfo:read::@var{offset},@var{length}
37538 @anchor{qXfer siginfo read}
37539 Read contents of the extra signal information on the target
37540 system. The annex part of the generic @samp{qXfer} packet must be
37541 empty (@pxref{qXfer read}).
37543 This packet is not probed by default; the remote stub must request it,
37544 by supplying an appropriate @samp{qSupported} response
37545 (@pxref{qSupported}).
37547 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
37548 @anchor{qXfer spu read}
37549 Read contents of an @code{spufs} file on the target system. The
37550 annex specifies which file to read; it must be of the form
37551 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
37552 in the target process, and @var{name} identifes the @code{spufs} file
37553 in that context to be accessed.
37555 This packet is not probed by default; the remote stub must request it,
37556 by supplying an appropriate @samp{qSupported} response
37557 (@pxref{qSupported}).
37559 @item qXfer:threads:read::@var{offset},@var{length}
37560 @anchor{qXfer threads read}
37561 Access the list of threads on target. @xref{Thread List Format}. The
37562 annex part of the generic @samp{qXfer} packet must be empty
37563 (@pxref{qXfer read}).
37565 This packet is not probed by default; the remote stub must request it,
37566 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37568 @item qXfer:traceframe-info:read::@var{offset},@var{length}
37569 @anchor{qXfer traceframe info read}
37571 Return a description of the current traceframe's contents.
37572 @xref{Traceframe Info Format}. The annex part of the generic
37573 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
37575 This packet is not probed by default; the remote stub must request it,
37576 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37578 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
37579 @anchor{qXfer unwind info block}
37581 Return the unwind information block for @var{pc}. This packet is used
37582 on OpenVMS/ia64 to ask the kernel unwind information.
37584 This packet is not probed by default.
37586 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
37587 @anchor{qXfer fdpic loadmap read}
37588 Read contents of @code{loadmap}s on the target system. The
37589 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
37590 executable @code{loadmap} or interpreter @code{loadmap} to read.
37592 This packet is not probed by default; the remote stub must request it,
37593 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37595 @item qXfer:osdata:read::@var{offset},@var{length}
37596 @anchor{qXfer osdata read}
37597 Access the target's @dfn{operating system information}.
37598 @xref{Operating System Information}.
37602 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
37603 @cindex write data into object, remote request
37604 @anchor{qXfer write}
37605 Write uninterpreted bytes into the target's special data area
37606 identified by the keyword @var{object}, starting at @var{offset} bytes
37607 into the data. The binary-encoded data (@pxref{Binary Data}) to be
37608 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
37609 is specific to @var{object}; it can supply additional details about what data
37615 @var{nn} (hex encoded) is the number of bytes written.
37616 This may be fewer bytes than supplied in the request.
37619 The request was malformed, or @var{annex} was invalid.
37622 The offset was invalid, or there was an error encountered writing the data.
37623 The @var{nn} part is a hex-encoded @code{errno} value.
37626 An empty reply indicates the @var{object} string was not
37627 recognized by the stub, or that the object does not support writing.
37630 Here are the specific requests of this form defined so far. All the
37631 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
37632 formats, listed above.
37635 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
37636 @anchor{qXfer siginfo write}
37637 Write @var{data} to the extra signal information on the target system.
37638 The annex part of the generic @samp{qXfer} packet must be
37639 empty (@pxref{qXfer write}).
37641 This packet is not probed by default; the remote stub must request it,
37642 by supplying an appropriate @samp{qSupported} response
37643 (@pxref{qSupported}).
37645 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
37646 @anchor{qXfer spu write}
37647 Write @var{data} to an @code{spufs} file on the target system. The
37648 annex specifies which file to write; it must be of the form
37649 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
37650 in the target process, and @var{name} identifes the @code{spufs} file
37651 in that context to be accessed.
37653 This packet is not probed by default; the remote stub must request it,
37654 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37657 @item qXfer:@var{object}:@var{operation}:@dots{}
37658 Requests of this form may be added in the future. When a stub does
37659 not recognize the @var{object} keyword, or its support for
37660 @var{object} does not recognize the @var{operation} keyword, the stub
37661 must respond with an empty packet.
37663 @item qAttached:@var{pid}
37664 @cindex query attached, remote request
37665 @cindex @samp{qAttached} packet
37666 Return an indication of whether the remote server attached to an
37667 existing process or created a new process. When the multiprocess
37668 protocol extensions are supported (@pxref{multiprocess extensions}),
37669 @var{pid} is an integer in hexadecimal format identifying the target
37670 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
37671 the query packet will be simplified as @samp{qAttached}.
37673 This query is used, for example, to know whether the remote process
37674 should be detached or killed when a @value{GDBN} session is ended with
37675 the @code{quit} command.
37680 The remote server attached to an existing process.
37682 The remote server created a new process.
37684 A badly formed request or an error was encountered.
37688 Enable branch tracing for the current thread using Branch Trace Store.
37693 Branch tracing has been enabled.
37695 A badly formed request or an error was encountered.
37699 Enable branch tracing for the current thread using Intel Processor Trace.
37704 Branch tracing has been enabled.
37706 A badly formed request or an error was encountered.
37710 Disable branch tracing for the current thread.
37715 Branch tracing has been disabled.
37717 A badly formed request or an error was encountered.
37720 @item Qbtrace-conf:bts:size=@var{value}
37721 Set the requested ring buffer size for new threads that use the
37722 btrace recording method in bts format.
37727 The ring buffer size has been set.
37729 A badly formed request or an error was encountered.
37732 @item Qbtrace-conf:pt:size=@var{value}
37733 Set the requested ring buffer size for new threads that use the
37734 btrace recording method in pt format.
37739 The ring buffer size has been set.
37741 A badly formed request or an error was encountered.
37746 @node Architecture-Specific Protocol Details
37747 @section Architecture-Specific Protocol Details
37749 This section describes how the remote protocol is applied to specific
37750 target architectures. Also see @ref{Standard Target Features}, for
37751 details of XML target descriptions for each architecture.
37754 * ARM-Specific Protocol Details::
37755 * MIPS-Specific Protocol Details::
37758 @node ARM-Specific Protocol Details
37759 @subsection @acronym{ARM}-specific Protocol Details
37762 * ARM Breakpoint Kinds::
37765 @node ARM Breakpoint Kinds
37766 @subsubsection @acronym{ARM} Breakpoint Kinds
37767 @cindex breakpoint kinds, @acronym{ARM}
37769 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
37774 16-bit Thumb mode breakpoint.
37777 32-bit Thumb mode (Thumb-2) breakpoint.
37780 32-bit @acronym{ARM} mode breakpoint.
37784 @node MIPS-Specific Protocol Details
37785 @subsection @acronym{MIPS}-specific Protocol Details
37788 * MIPS Register packet Format::
37789 * MIPS Breakpoint Kinds::
37792 @node MIPS Register packet Format
37793 @subsubsection @acronym{MIPS} Register Packet Format
37794 @cindex register packet format, @acronym{MIPS}
37796 The following @code{g}/@code{G} packets have previously been defined.
37797 In the below, some thirty-two bit registers are transferred as
37798 sixty-four bits. Those registers should be zero/sign extended (which?)
37799 to fill the space allocated. Register bytes are transferred in target
37800 byte order. The two nibbles within a register byte are transferred
37801 most-significant -- least-significant.
37806 All registers are transferred as thirty-two bit quantities in the order:
37807 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
37808 registers; fsr; fir; fp.
37811 All registers are transferred as sixty-four bit quantities (including
37812 thirty-two bit registers such as @code{sr}). The ordering is the same
37817 @node MIPS Breakpoint Kinds
37818 @subsubsection @acronym{MIPS} Breakpoint Kinds
37819 @cindex breakpoint kinds, @acronym{MIPS}
37821 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
37826 16-bit @acronym{MIPS16} mode breakpoint.
37829 16-bit @acronym{microMIPS} mode breakpoint.
37832 32-bit standard @acronym{MIPS} mode breakpoint.
37835 32-bit @acronym{microMIPS} mode breakpoint.
37839 @node Tracepoint Packets
37840 @section Tracepoint Packets
37841 @cindex tracepoint packets
37842 @cindex packets, tracepoint
37844 Here we describe the packets @value{GDBN} uses to implement
37845 tracepoints (@pxref{Tracepoints}).
37849 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
37850 @cindex @samp{QTDP} packet
37851 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
37852 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
37853 the tracepoint is disabled. The @var{step} gives the tracepoint's step
37854 count, and @var{pass} gives its pass count. If an @samp{F} is present,
37855 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
37856 the number of bytes that the target should copy elsewhere to make room
37857 for the tracepoint. If an @samp{X} is present, it introduces a
37858 tracepoint condition, which consists of a hexadecimal length, followed
37859 by a comma and hex-encoded bytes, in a manner similar to action
37860 encodings as described below. If the trailing @samp{-} is present,
37861 further @samp{QTDP} packets will follow to specify this tracepoint's
37867 The packet was understood and carried out.
37869 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
37871 The packet was not recognized.
37874 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
37875 Define actions to be taken when a tracepoint is hit. The @var{n} and
37876 @var{addr} must be the same as in the initial @samp{QTDP} packet for
37877 this tracepoint. This packet may only be sent immediately after
37878 another @samp{QTDP} packet that ended with a @samp{-}. If the
37879 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
37880 specifying more actions for this tracepoint.
37882 In the series of action packets for a given tracepoint, at most one
37883 can have an @samp{S} before its first @var{action}. If such a packet
37884 is sent, it and the following packets define ``while-stepping''
37885 actions. Any prior packets define ordinary actions --- that is, those
37886 taken when the tracepoint is first hit. If no action packet has an
37887 @samp{S}, then all the packets in the series specify ordinary
37888 tracepoint actions.
37890 The @samp{@var{action}@dots{}} portion of the packet is a series of
37891 actions, concatenated without separators. Each action has one of the
37897 Collect the registers whose bits are set in @var{mask},
37898 a hexadecimal number whose @var{i}'th bit is set if register number
37899 @var{i} should be collected. (The least significant bit is numbered
37900 zero.) Note that @var{mask} may be any number of digits long; it may
37901 not fit in a 32-bit word.
37903 @item M @var{basereg},@var{offset},@var{len}
37904 Collect @var{len} bytes of memory starting at the address in register
37905 number @var{basereg}, plus @var{offset}. If @var{basereg} is
37906 @samp{-1}, then the range has a fixed address: @var{offset} is the
37907 address of the lowest byte to collect. The @var{basereg},
37908 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
37909 values (the @samp{-1} value for @var{basereg} is a special case).
37911 @item X @var{len},@var{expr}
37912 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
37913 it directs. The agent expression @var{expr} is as described in
37914 @ref{Agent Expressions}. Each byte of the expression is encoded as a
37915 two-digit hex number in the packet; @var{len} is the number of bytes
37916 in the expression (and thus one-half the number of hex digits in the
37921 Any number of actions may be packed together in a single @samp{QTDP}
37922 packet, as long as the packet does not exceed the maximum packet
37923 length (400 bytes, for many stubs). There may be only one @samp{R}
37924 action per tracepoint, and it must precede any @samp{M} or @samp{X}
37925 actions. Any registers referred to by @samp{M} and @samp{X} actions
37926 must be collected by a preceding @samp{R} action. (The
37927 ``while-stepping'' actions are treated as if they were attached to a
37928 separate tracepoint, as far as these restrictions are concerned.)
37933 The packet was understood and carried out.
37935 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
37937 The packet was not recognized.
37940 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
37941 @cindex @samp{QTDPsrc} packet
37942 Specify a source string of tracepoint @var{n} at address @var{addr}.
37943 This is useful to get accurate reproduction of the tracepoints
37944 originally downloaded at the beginning of the trace run. The @var{type}
37945 is the name of the tracepoint part, such as @samp{cond} for the
37946 tracepoint's conditional expression (see below for a list of types), while
37947 @var{bytes} is the string, encoded in hexadecimal.
37949 @var{start} is the offset of the @var{bytes} within the overall source
37950 string, while @var{slen} is the total length of the source string.
37951 This is intended for handling source strings that are longer than will
37952 fit in a single packet.
37953 @c Add detailed example when this info is moved into a dedicated
37954 @c tracepoint descriptions section.
37956 The available string types are @samp{at} for the location,
37957 @samp{cond} for the conditional, and @samp{cmd} for an action command.
37958 @value{GDBN} sends a separate packet for each command in the action
37959 list, in the same order in which the commands are stored in the list.
37961 The target does not need to do anything with source strings except
37962 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
37965 Although this packet is optional, and @value{GDBN} will only send it
37966 if the target replies with @samp{TracepointSource} @xref{General
37967 Query Packets}, it makes both disconnected tracing and trace files
37968 much easier to use. Otherwise the user must be careful that the
37969 tracepoints in effect while looking at trace frames are identical to
37970 the ones in effect during the trace run; even a small discrepancy
37971 could cause @samp{tdump} not to work, or a particular trace frame not
37974 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
37975 @cindex define trace state variable, remote request
37976 @cindex @samp{QTDV} packet
37977 Create a new trace state variable, number @var{n}, with an initial
37978 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
37979 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
37980 the option of not using this packet for initial values of zero; the
37981 target should simply create the trace state variables as they are
37982 mentioned in expressions. The value @var{builtin} should be 1 (one)
37983 if the trace state variable is builtin and 0 (zero) if it is not builtin.
37984 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
37985 @samp{qTsV} packet had it set. The contents of @var{name} is the
37986 hex-encoded name (without the leading @samp{$}) of the trace state
37989 @item QTFrame:@var{n}
37990 @cindex @samp{QTFrame} packet
37991 Select the @var{n}'th tracepoint frame from the buffer, and use the
37992 register and memory contents recorded there to answer subsequent
37993 request packets from @value{GDBN}.
37995 A successful reply from the stub indicates that the stub has found the
37996 requested frame. The response is a series of parts, concatenated
37997 without separators, describing the frame we selected. Each part has
37998 one of the following forms:
38002 The selected frame is number @var{n} in the trace frame buffer;
38003 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
38004 was no frame matching the criteria in the request packet.
38007 The selected trace frame records a hit of tracepoint number @var{t};
38008 @var{t} is a hexadecimal number.
38012 @item QTFrame:pc:@var{addr}
38013 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38014 currently selected frame whose PC is @var{addr};
38015 @var{addr} is a hexadecimal number.
38017 @item QTFrame:tdp:@var{t}
38018 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38019 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
38020 is a hexadecimal number.
38022 @item QTFrame:range:@var{start}:@var{end}
38023 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38024 currently selected frame whose PC is between @var{start} (inclusive)
38025 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
38028 @item QTFrame:outside:@var{start}:@var{end}
38029 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
38030 frame @emph{outside} the given range of addresses (exclusive).
38033 @cindex @samp{qTMinFTPILen} packet
38034 This packet requests the minimum length of instruction at which a fast
38035 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
38036 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
38037 it depends on the target system being able to create trampolines in
38038 the first 64K of memory, which might or might not be possible for that
38039 system. So the reply to this packet will be 4 if it is able to
38046 The minimum instruction length is currently unknown.
38048 The minimum instruction length is @var{length}, where @var{length}
38049 is a hexadecimal number greater or equal to 1. A reply
38050 of 1 means that a fast tracepoint may be placed on any instruction
38051 regardless of size.
38053 An error has occurred.
38055 An empty reply indicates that the request is not supported by the stub.
38059 @cindex @samp{QTStart} packet
38060 Begin the tracepoint experiment. Begin collecting data from
38061 tracepoint hits in the trace frame buffer. This packet supports the
38062 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
38063 instruction reply packet}).
38066 @cindex @samp{QTStop} packet
38067 End the tracepoint experiment. Stop collecting trace frames.
38069 @item QTEnable:@var{n}:@var{addr}
38071 @cindex @samp{QTEnable} packet
38072 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
38073 experiment. If the tracepoint was previously disabled, then collection
38074 of data from it will resume.
38076 @item QTDisable:@var{n}:@var{addr}
38078 @cindex @samp{QTDisable} packet
38079 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
38080 experiment. No more data will be collected from the tracepoint unless
38081 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
38084 @cindex @samp{QTinit} packet
38085 Clear the table of tracepoints, and empty the trace frame buffer.
38087 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
38088 @cindex @samp{QTro} packet
38089 Establish the given ranges of memory as ``transparent''. The stub
38090 will answer requests for these ranges from memory's current contents,
38091 if they were not collected as part of the tracepoint hit.
38093 @value{GDBN} uses this to mark read-only regions of memory, like those
38094 containing program code. Since these areas never change, they should
38095 still have the same contents they did when the tracepoint was hit, so
38096 there's no reason for the stub to refuse to provide their contents.
38098 @item QTDisconnected:@var{value}
38099 @cindex @samp{QTDisconnected} packet
38100 Set the choice to what to do with the tracing run when @value{GDBN}
38101 disconnects from the target. A @var{value} of 1 directs the target to
38102 continue the tracing run, while 0 tells the target to stop tracing if
38103 @value{GDBN} is no longer in the picture.
38106 @cindex @samp{qTStatus} packet
38107 Ask the stub if there is a trace experiment running right now.
38109 The reply has the form:
38113 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
38114 @var{running} is a single digit @code{1} if the trace is presently
38115 running, or @code{0} if not. It is followed by semicolon-separated
38116 optional fields that an agent may use to report additional status.
38120 If the trace is not running, the agent may report any of several
38121 explanations as one of the optional fields:
38126 No trace has been run yet.
38128 @item tstop[:@var{text}]:0
38129 The trace was stopped by a user-originated stop command. The optional
38130 @var{text} field is a user-supplied string supplied as part of the
38131 stop command (for instance, an explanation of why the trace was
38132 stopped manually). It is hex-encoded.
38135 The trace stopped because the trace buffer filled up.
38137 @item tdisconnected:0
38138 The trace stopped because @value{GDBN} disconnected from the target.
38140 @item tpasscount:@var{tpnum}
38141 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
38143 @item terror:@var{text}:@var{tpnum}
38144 The trace stopped because tracepoint @var{tpnum} had an error. The
38145 string @var{text} is available to describe the nature of the error
38146 (for instance, a divide by zero in the condition expression); it
38150 The trace stopped for some other reason.
38154 Additional optional fields supply statistical and other information.
38155 Although not required, they are extremely useful for users monitoring
38156 the progress of a trace run. If a trace has stopped, and these
38157 numbers are reported, they must reflect the state of the just-stopped
38162 @item tframes:@var{n}
38163 The number of trace frames in the buffer.
38165 @item tcreated:@var{n}
38166 The total number of trace frames created during the run. This may
38167 be larger than the trace frame count, if the buffer is circular.
38169 @item tsize:@var{n}
38170 The total size of the trace buffer, in bytes.
38172 @item tfree:@var{n}
38173 The number of bytes still unused in the buffer.
38175 @item circular:@var{n}
38176 The value of the circular trace buffer flag. @code{1} means that the
38177 trace buffer is circular and old trace frames will be discarded if
38178 necessary to make room, @code{0} means that the trace buffer is linear
38181 @item disconn:@var{n}
38182 The value of the disconnected tracing flag. @code{1} means that
38183 tracing will continue after @value{GDBN} disconnects, @code{0} means
38184 that the trace run will stop.
38188 @item qTP:@var{tp}:@var{addr}
38189 @cindex tracepoint status, remote request
38190 @cindex @samp{qTP} packet
38191 Ask the stub for the current state of tracepoint number @var{tp} at
38192 address @var{addr}.
38196 @item V@var{hits}:@var{usage}
38197 The tracepoint has been hit @var{hits} times so far during the trace
38198 run, and accounts for @var{usage} in the trace buffer. Note that
38199 @code{while-stepping} steps are not counted as separate hits, but the
38200 steps' space consumption is added into the usage number.
38204 @item qTV:@var{var}
38205 @cindex trace state variable value, remote request
38206 @cindex @samp{qTV} packet
38207 Ask the stub for the value of the trace state variable number @var{var}.
38212 The value of the variable is @var{value}. This will be the current
38213 value of the variable if the user is examining a running target, or a
38214 saved value if the variable was collected in the trace frame that the
38215 user is looking at. Note that multiple requests may result in
38216 different reply values, such as when requesting values while the
38217 program is running.
38220 The value of the variable is unknown. This would occur, for example,
38221 if the user is examining a trace frame in which the requested variable
38226 @cindex @samp{qTfP} packet
38228 @cindex @samp{qTsP} packet
38229 These packets request data about tracepoints that are being used by
38230 the target. @value{GDBN} sends @code{qTfP} to get the first piece
38231 of data, and multiple @code{qTsP} to get additional pieces. Replies
38232 to these packets generally take the form of the @code{QTDP} packets
38233 that define tracepoints. (FIXME add detailed syntax)
38236 @cindex @samp{qTfV} packet
38238 @cindex @samp{qTsV} packet
38239 These packets request data about trace state variables that are on the
38240 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
38241 and multiple @code{qTsV} to get additional variables. Replies to
38242 these packets follow the syntax of the @code{QTDV} packets that define
38243 trace state variables.
38249 @cindex @samp{qTfSTM} packet
38250 @cindex @samp{qTsSTM} packet
38251 These packets request data about static tracepoint markers that exist
38252 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
38253 first piece of data, and multiple @code{qTsSTM} to get additional
38254 pieces. Replies to these packets take the following form:
38258 @item m @var{address}:@var{id}:@var{extra}
38260 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
38261 a comma-separated list of markers
38263 (lower case letter @samp{L}) denotes end of list.
38265 An error occurred. The error number @var{nn} is given as hex digits.
38267 An empty reply indicates that the request is not supported by the
38271 The @var{address} is encoded in hex;
38272 @var{id} and @var{extra} are strings encoded in hex.
38274 In response to each query, the target will reply with a list of one or
38275 more markers, separated by commas. @value{GDBN} will respond to each
38276 reply with a request for more markers (using the @samp{qs} form of the
38277 query), until the target responds with @samp{l} (lower-case ell, for
38280 @item qTSTMat:@var{address}
38282 @cindex @samp{qTSTMat} packet
38283 This packets requests data about static tracepoint markers in the
38284 target program at @var{address}. Replies to this packet follow the
38285 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
38286 tracepoint markers.
38288 @item QTSave:@var{filename}
38289 @cindex @samp{QTSave} packet
38290 This packet directs the target to save trace data to the file name
38291 @var{filename} in the target's filesystem. The @var{filename} is encoded
38292 as a hex string; the interpretation of the file name (relative vs
38293 absolute, wild cards, etc) is up to the target.
38295 @item qTBuffer:@var{offset},@var{len}
38296 @cindex @samp{qTBuffer} packet
38297 Return up to @var{len} bytes of the current contents of trace buffer,
38298 starting at @var{offset}. The trace buffer is treated as if it were
38299 a contiguous collection of traceframes, as per the trace file format.
38300 The reply consists as many hex-encoded bytes as the target can deliver
38301 in a packet; it is not an error to return fewer than were asked for.
38302 A reply consisting of just @code{l} indicates that no bytes are
38305 @item QTBuffer:circular:@var{value}
38306 This packet directs the target to use a circular trace buffer if
38307 @var{value} is 1, or a linear buffer if the value is 0.
38309 @item QTBuffer:size:@var{size}
38310 @anchor{QTBuffer-size}
38311 @cindex @samp{QTBuffer size} packet
38312 This packet directs the target to make the trace buffer be of size
38313 @var{size} if possible. A value of @code{-1} tells the target to
38314 use whatever size it prefers.
38316 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
38317 @cindex @samp{QTNotes} packet
38318 This packet adds optional textual notes to the trace run. Allowable
38319 types include @code{user}, @code{notes}, and @code{tstop}, the
38320 @var{text} fields are arbitrary strings, hex-encoded.
38324 @subsection Relocate instruction reply packet
38325 When installing fast tracepoints in memory, the target may need to
38326 relocate the instruction currently at the tracepoint address to a
38327 different address in memory. For most instructions, a simple copy is
38328 enough, but, for example, call instructions that implicitly push the
38329 return address on the stack, and relative branches or other
38330 PC-relative instructions require offset adjustment, so that the effect
38331 of executing the instruction at a different address is the same as if
38332 it had executed in the original location.
38334 In response to several of the tracepoint packets, the target may also
38335 respond with a number of intermediate @samp{qRelocInsn} request
38336 packets before the final result packet, to have @value{GDBN} handle
38337 this relocation operation. If a packet supports this mechanism, its
38338 documentation will explicitly say so. See for example the above
38339 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
38340 format of the request is:
38343 @item qRelocInsn:@var{from};@var{to}
38345 This requests @value{GDBN} to copy instruction at address @var{from}
38346 to address @var{to}, possibly adjusted so that executing the
38347 instruction at @var{to} has the same effect as executing it at
38348 @var{from}. @value{GDBN} writes the adjusted instruction to target
38349 memory starting at @var{to}.
38354 @item qRelocInsn:@var{adjusted_size}
38355 Informs the stub the relocation is complete. The @var{adjusted_size} is
38356 the length in bytes of resulting relocated instruction sequence.
38358 A badly formed request was detected, or an error was encountered while
38359 relocating the instruction.
38362 @node Host I/O Packets
38363 @section Host I/O Packets
38364 @cindex Host I/O, remote protocol
38365 @cindex file transfer, remote protocol
38367 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
38368 operations on the far side of a remote link. For example, Host I/O is
38369 used to upload and download files to a remote target with its own
38370 filesystem. Host I/O uses the same constant values and data structure
38371 layout as the target-initiated File-I/O protocol. However, the
38372 Host I/O packets are structured differently. The target-initiated
38373 protocol relies on target memory to store parameters and buffers.
38374 Host I/O requests are initiated by @value{GDBN}, and the
38375 target's memory is not involved. @xref{File-I/O Remote Protocol
38376 Extension}, for more details on the target-initiated protocol.
38378 The Host I/O request packets all encode a single operation along with
38379 its arguments. They have this format:
38383 @item vFile:@var{operation}: @var{parameter}@dots{}
38384 @var{operation} is the name of the particular request; the target
38385 should compare the entire packet name up to the second colon when checking
38386 for a supported operation. The format of @var{parameter} depends on
38387 the operation. Numbers are always passed in hexadecimal. Negative
38388 numbers have an explicit minus sign (i.e.@: two's complement is not
38389 used). Strings (e.g.@: filenames) are encoded as a series of
38390 hexadecimal bytes. The last argument to a system call may be a
38391 buffer of escaped binary data (@pxref{Binary Data}).
38395 The valid responses to Host I/O packets are:
38399 @item F @var{result} [, @var{errno}] [; @var{attachment}]
38400 @var{result} is the integer value returned by this operation, usually
38401 non-negative for success and -1 for errors. If an error has occured,
38402 @var{errno} will be included in the result specifying a
38403 value defined by the File-I/O protocol (@pxref{Errno Values}). For
38404 operations which return data, @var{attachment} supplies the data as a
38405 binary buffer. Binary buffers in response packets are escaped in the
38406 normal way (@pxref{Binary Data}). See the individual packet
38407 documentation for the interpretation of @var{result} and
38411 An empty response indicates that this operation is not recognized.
38415 These are the supported Host I/O operations:
38418 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
38419 Open a file at @var{filename} and return a file descriptor for it, or
38420 return -1 if an error occurs. The @var{filename} is a string,
38421 @var{flags} is an integer indicating a mask of open flags
38422 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
38423 of mode bits to use if the file is created (@pxref{mode_t Values}).
38424 @xref{open}, for details of the open flags and mode values.
38426 @item vFile:close: @var{fd}
38427 Close the open file corresponding to @var{fd} and return 0, or
38428 -1 if an error occurs.
38430 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
38431 Read data from the open file corresponding to @var{fd}. Up to
38432 @var{count} bytes will be read from the file, starting at @var{offset}
38433 relative to the start of the file. The target may read fewer bytes;
38434 common reasons include packet size limits and an end-of-file
38435 condition. The number of bytes read is returned. Zero should only be
38436 returned for a successful read at the end of the file, or if
38437 @var{count} was zero.
38439 The data read should be returned as a binary attachment on success.
38440 If zero bytes were read, the response should include an empty binary
38441 attachment (i.e.@: a trailing semicolon). The return value is the
38442 number of target bytes read; the binary attachment may be longer if
38443 some characters were escaped.
38445 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
38446 Write @var{data} (a binary buffer) to the open file corresponding
38447 to @var{fd}. Start the write at @var{offset} from the start of the
38448 file. Unlike many @code{write} system calls, there is no
38449 separate @var{count} argument; the length of @var{data} in the
38450 packet is used. @samp{vFile:write} returns the number of bytes written,
38451 which may be shorter than the length of @var{data}, or -1 if an
38454 @item vFile:fstat: @var{fd}
38455 Get information about the open file corresponding to @var{fd}.
38456 On success the information is returned as a binary attachment
38457 and the return value is the size of this attachment in bytes.
38458 If an error occurs the return value is -1. The format of the
38459 returned binary attachment is as described in @ref{struct stat}.
38461 @item vFile:unlink: @var{filename}
38462 Delete the file at @var{filename} on the target. Return 0,
38463 or -1 if an error occurs. The @var{filename} is a string.
38465 @item vFile:readlink: @var{filename}
38466 Read value of symbolic link @var{filename} on the target. Return
38467 the number of bytes read, or -1 if an error occurs.
38469 The data read should be returned as a binary attachment on success.
38470 If zero bytes were read, the response should include an empty binary
38471 attachment (i.e.@: a trailing semicolon). The return value is the
38472 number of target bytes read; the binary attachment may be longer if
38473 some characters were escaped.
38475 @item vFile:setfs: @var{pid}
38476 Select the filesystem on which @code{vFile} operations with
38477 @var{filename} arguments will operate. This is required for
38478 @value{GDBN} to be able to access files on remote targets where
38479 the remote stub does not share a common filesystem with the
38482 If @var{pid} is nonzero, select the filesystem as seen by process
38483 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
38484 the remote stub. Return 0 on success, or -1 if an error occurs.
38485 If @code{vFile:setfs:} indicates success, the selected filesystem
38486 remains selected until the next successful @code{vFile:setfs:}
38492 @section Interrupts
38493 @cindex interrupts (remote protocol)
38494 @anchor{interrupting remote targets}
38496 In all-stop mode, when a program on the remote target is running,
38497 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
38498 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
38499 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
38501 The precise meaning of @code{BREAK} is defined by the transport
38502 mechanism and may, in fact, be undefined. @value{GDBN} does not
38503 currently define a @code{BREAK} mechanism for any of the network
38504 interfaces except for TCP, in which case @value{GDBN} sends the
38505 @code{telnet} BREAK sequence.
38507 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
38508 transport mechanisms. It is represented by sending the single byte
38509 @code{0x03} without any of the usual packet overhead described in
38510 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
38511 transmitted as part of a packet, it is considered to be packet data
38512 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
38513 (@pxref{X packet}), used for binary downloads, may include an unescaped
38514 @code{0x03} as part of its packet.
38516 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
38517 When Linux kernel receives this sequence from serial port,
38518 it stops execution and connects to gdb.
38520 In non-stop mode, because packet resumptions are asynchronous
38521 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
38522 command to the remote stub, even when the target is running. For that
38523 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
38524 packet}) with the usual packet framing instead of the single byte
38527 Stubs are not required to recognize these interrupt mechanisms and the
38528 precise meaning associated with receipt of the interrupt is
38529 implementation defined. If the target supports debugging of multiple
38530 threads and/or processes, it should attempt to interrupt all
38531 currently-executing threads and processes.
38532 If the stub is successful at interrupting the
38533 running program, it should send one of the stop
38534 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
38535 of successfully stopping the program in all-stop mode, and a stop reply
38536 for each stopped thread in non-stop mode.
38537 Interrupts received while the
38538 program is stopped are queued and the program will be interrupted when
38539 it is resumed next time.
38541 @node Notification Packets
38542 @section Notification Packets
38543 @cindex notification packets
38544 @cindex packets, notification
38546 The @value{GDBN} remote serial protocol includes @dfn{notifications},
38547 packets that require no acknowledgment. Both the GDB and the stub
38548 may send notifications (although the only notifications defined at
38549 present are sent by the stub). Notifications carry information
38550 without incurring the round-trip latency of an acknowledgment, and so
38551 are useful for low-impact communications where occasional packet loss
38554 A notification packet has the form @samp{% @var{data} #
38555 @var{checksum}}, where @var{data} is the content of the notification,
38556 and @var{checksum} is a checksum of @var{data}, computed and formatted
38557 as for ordinary @value{GDBN} packets. A notification's @var{data}
38558 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
38559 receiving a notification, the recipient sends no @samp{+} or @samp{-}
38560 to acknowledge the notification's receipt or to report its corruption.
38562 Every notification's @var{data} begins with a name, which contains no
38563 colon characters, followed by a colon character.
38565 Recipients should silently ignore corrupted notifications and
38566 notifications they do not understand. Recipients should restart
38567 timeout periods on receipt of a well-formed notification, whether or
38568 not they understand it.
38570 Senders should only send the notifications described here when this
38571 protocol description specifies that they are permitted. In the
38572 future, we may extend the protocol to permit existing notifications in
38573 new contexts; this rule helps older senders avoid confusing newer
38576 (Older versions of @value{GDBN} ignore bytes received until they see
38577 the @samp{$} byte that begins an ordinary packet, so new stubs may
38578 transmit notifications without fear of confusing older clients. There
38579 are no notifications defined for @value{GDBN} to send at the moment, but we
38580 assume that most older stubs would ignore them, as well.)
38582 Each notification is comprised of three parts:
38584 @item @var{name}:@var{event}
38585 The notification packet is sent by the side that initiates the
38586 exchange (currently, only the stub does that), with @var{event}
38587 carrying the specific information about the notification, and
38588 @var{name} specifying the name of the notification.
38590 The acknowledge sent by the other side, usually @value{GDBN}, to
38591 acknowledge the exchange and request the event.
38594 The purpose of an asynchronous notification mechanism is to report to
38595 @value{GDBN} that something interesting happened in the remote stub.
38597 The remote stub may send notification @var{name}:@var{event}
38598 at any time, but @value{GDBN} acknowledges the notification when
38599 appropriate. The notification event is pending before @value{GDBN}
38600 acknowledges. Only one notification at a time may be pending; if
38601 additional events occur before @value{GDBN} has acknowledged the
38602 previous notification, they must be queued by the stub for later
38603 synchronous transmission in response to @var{ack} packets from
38604 @value{GDBN}. Because the notification mechanism is unreliable,
38605 the stub is permitted to resend a notification if it believes
38606 @value{GDBN} may not have received it.
38608 Specifically, notifications may appear when @value{GDBN} is not
38609 otherwise reading input from the stub, or when @value{GDBN} is
38610 expecting to read a normal synchronous response or a
38611 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
38612 Notification packets are distinct from any other communication from
38613 the stub so there is no ambiguity.
38615 After receiving a notification, @value{GDBN} shall acknowledge it by
38616 sending a @var{ack} packet as a regular, synchronous request to the
38617 stub. Such acknowledgment is not required to happen immediately, as
38618 @value{GDBN} is permitted to send other, unrelated packets to the
38619 stub first, which the stub should process normally.
38621 Upon receiving a @var{ack} packet, if the stub has other queued
38622 events to report to @value{GDBN}, it shall respond by sending a
38623 normal @var{event}. @value{GDBN} shall then send another @var{ack}
38624 packet to solicit further responses; again, it is permitted to send
38625 other, unrelated packets as well which the stub should process
38628 If the stub receives a @var{ack} packet and there are no additional
38629 @var{event} to report, the stub shall return an @samp{OK} response.
38630 At this point, @value{GDBN} has finished processing a notification
38631 and the stub has completed sending any queued events. @value{GDBN}
38632 won't accept any new notifications until the final @samp{OK} is
38633 received . If further notification events occur, the stub shall send
38634 a new notification, @value{GDBN} shall accept the notification, and
38635 the process shall be repeated.
38637 The process of asynchronous notification can be illustrated by the
38640 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
38643 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
38645 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
38650 The following notifications are defined:
38651 @multitable @columnfractions 0.12 0.12 0.38 0.38
38660 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
38661 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
38662 for information on how these notifications are acknowledged by
38664 @tab Report an asynchronous stop event in non-stop mode.
38668 @node Remote Non-Stop
38669 @section Remote Protocol Support for Non-Stop Mode
38671 @value{GDBN}'s remote protocol supports non-stop debugging of
38672 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
38673 supports non-stop mode, it should report that to @value{GDBN} by including
38674 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
38676 @value{GDBN} typically sends a @samp{QNonStop} packet only when
38677 establishing a new connection with the stub. Entering non-stop mode
38678 does not alter the state of any currently-running threads, but targets
38679 must stop all threads in any already-attached processes when entering
38680 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
38681 probe the target state after a mode change.
38683 In non-stop mode, when an attached process encounters an event that
38684 would otherwise be reported with a stop reply, it uses the
38685 asynchronous notification mechanism (@pxref{Notification Packets}) to
38686 inform @value{GDBN}. In contrast to all-stop mode, where all threads
38687 in all processes are stopped when a stop reply is sent, in non-stop
38688 mode only the thread reporting the stop event is stopped. That is,
38689 when reporting a @samp{S} or @samp{T} response to indicate completion
38690 of a step operation, hitting a breakpoint, or a fault, only the
38691 affected thread is stopped; any other still-running threads continue
38692 to run. When reporting a @samp{W} or @samp{X} response, all running
38693 threads belonging to other attached processes continue to run.
38695 In non-stop mode, the target shall respond to the @samp{?} packet as
38696 follows. First, any incomplete stop reply notification/@samp{vStopped}
38697 sequence in progress is abandoned. The target must begin a new
38698 sequence reporting stop events for all stopped threads, whether or not
38699 it has previously reported those events to @value{GDBN}. The first
38700 stop reply is sent as a synchronous reply to the @samp{?} packet, and
38701 subsequent stop replies are sent as responses to @samp{vStopped} packets
38702 using the mechanism described above. The target must not send
38703 asynchronous stop reply notifications until the sequence is complete.
38704 If all threads are running when the target receives the @samp{?} packet,
38705 or if the target is not attached to any process, it shall respond
38708 If the stub supports non-stop mode, it should also support the
38709 @samp{swbreak} stop reason if software breakpoints are supported, and
38710 the @samp{hwbreak} stop reason if hardware breakpoints are supported
38711 (@pxref{swbreak stop reason}). This is because given the asynchronous
38712 nature of non-stop mode, between the time a thread hits a breakpoint
38713 and the time the event is finally processed by @value{GDBN}, the
38714 breakpoint may have already been removed from the target. Due to
38715 this, @value{GDBN} needs to be able to tell whether a trap stop was
38716 caused by a delayed breakpoint event, which should be ignored, as
38717 opposed to a random trap signal, which should be reported to the user.
38718 Note the @samp{swbreak} feature implies that the target is responsible
38719 for adjusting the PC when a software breakpoint triggers, if
38720 necessary, such as on the x86 architecture.
38722 @node Packet Acknowledgment
38723 @section Packet Acknowledgment
38725 @cindex acknowledgment, for @value{GDBN} remote
38726 @cindex packet acknowledgment, for @value{GDBN} remote
38727 By default, when either the host or the target machine receives a packet,
38728 the first response expected is an acknowledgment: either @samp{+} (to indicate
38729 the package was received correctly) or @samp{-} (to request retransmission).
38730 This mechanism allows the @value{GDBN} remote protocol to operate over
38731 unreliable transport mechanisms, such as a serial line.
38733 In cases where the transport mechanism is itself reliable (such as a pipe or
38734 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
38735 It may be desirable to disable them in that case to reduce communication
38736 overhead, or for other reasons. This can be accomplished by means of the
38737 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
38739 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
38740 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
38741 and response format still includes the normal checksum, as described in
38742 @ref{Overview}, but the checksum may be ignored by the receiver.
38744 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
38745 no-acknowledgment mode, it should report that to @value{GDBN}
38746 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
38747 @pxref{qSupported}.
38748 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
38749 disabled via the @code{set remote noack-packet off} command
38750 (@pxref{Remote Configuration}),
38751 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
38752 Only then may the stub actually turn off packet acknowledgments.
38753 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
38754 response, which can be safely ignored by the stub.
38756 Note that @code{set remote noack-packet} command only affects negotiation
38757 between @value{GDBN} and the stub when subsequent connections are made;
38758 it does not affect the protocol acknowledgment state for any current
38760 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
38761 new connection is established,
38762 there is also no protocol request to re-enable the acknowledgments
38763 for the current connection, once disabled.
38768 Example sequence of a target being re-started. Notice how the restart
38769 does not get any direct output:
38774 @emph{target restarts}
38777 <- @code{T001:1234123412341234}
38781 Example sequence of a target being stepped by a single instruction:
38784 -> @code{G1445@dots{}}
38789 <- @code{T001:1234123412341234}
38793 <- @code{1455@dots{}}
38797 @node File-I/O Remote Protocol Extension
38798 @section File-I/O Remote Protocol Extension
38799 @cindex File-I/O remote protocol extension
38802 * File-I/O Overview::
38803 * Protocol Basics::
38804 * The F Request Packet::
38805 * The F Reply Packet::
38806 * The Ctrl-C Message::
38808 * List of Supported Calls::
38809 * Protocol-specific Representation of Datatypes::
38811 * File-I/O Examples::
38814 @node File-I/O Overview
38815 @subsection File-I/O Overview
38816 @cindex file-i/o overview
38818 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
38819 target to use the host's file system and console I/O to perform various
38820 system calls. System calls on the target system are translated into a
38821 remote protocol packet to the host system, which then performs the needed
38822 actions and returns a response packet to the target system.
38823 This simulates file system operations even on targets that lack file systems.
38825 The protocol is defined to be independent of both the host and target systems.
38826 It uses its own internal representation of datatypes and values. Both
38827 @value{GDBN} and the target's @value{GDBN} stub are responsible for
38828 translating the system-dependent value representations into the internal
38829 protocol representations when data is transmitted.
38831 The communication is synchronous. A system call is possible only when
38832 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
38833 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
38834 the target is stopped to allow deterministic access to the target's
38835 memory. Therefore File-I/O is not interruptible by target signals. On
38836 the other hand, it is possible to interrupt File-I/O by a user interrupt
38837 (@samp{Ctrl-C}) within @value{GDBN}.
38839 The target's request to perform a host system call does not finish
38840 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
38841 after finishing the system call, the target returns to continuing the
38842 previous activity (continue, step). No additional continue or step
38843 request from @value{GDBN} is required.
38846 (@value{GDBP}) continue
38847 <- target requests 'system call X'
38848 target is stopped, @value{GDBN} executes system call
38849 -> @value{GDBN} returns result
38850 ... target continues, @value{GDBN} returns to wait for the target
38851 <- target hits breakpoint and sends a Txx packet
38854 The protocol only supports I/O on the console and to regular files on
38855 the host file system. Character or block special devices, pipes,
38856 named pipes, sockets or any other communication method on the host
38857 system are not supported by this protocol.
38859 File I/O is not supported in non-stop mode.
38861 @node Protocol Basics
38862 @subsection Protocol Basics
38863 @cindex protocol basics, file-i/o
38865 The File-I/O protocol uses the @code{F} packet as the request as well
38866 as reply packet. Since a File-I/O system call can only occur when
38867 @value{GDBN} is waiting for a response from the continuing or stepping target,
38868 the File-I/O request is a reply that @value{GDBN} has to expect as a result
38869 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
38870 This @code{F} packet contains all information needed to allow @value{GDBN}
38871 to call the appropriate host system call:
38875 A unique identifier for the requested system call.
38878 All parameters to the system call. Pointers are given as addresses
38879 in the target memory address space. Pointers to strings are given as
38880 pointer/length pair. Numerical values are given as they are.
38881 Numerical control flags are given in a protocol-specific representation.
38885 At this point, @value{GDBN} has to perform the following actions.
38889 If the parameters include pointer values to data needed as input to a
38890 system call, @value{GDBN} requests this data from the target with a
38891 standard @code{m} packet request. This additional communication has to be
38892 expected by the target implementation and is handled as any other @code{m}
38896 @value{GDBN} translates all value from protocol representation to host
38897 representation as needed. Datatypes are coerced into the host types.
38900 @value{GDBN} calls the system call.
38903 It then coerces datatypes back to protocol representation.
38906 If the system call is expected to return data in buffer space specified
38907 by pointer parameters to the call, the data is transmitted to the
38908 target using a @code{M} or @code{X} packet. This packet has to be expected
38909 by the target implementation and is handled as any other @code{M} or @code{X}
38914 Eventually @value{GDBN} replies with another @code{F} packet which contains all
38915 necessary information for the target to continue. This at least contains
38922 @code{errno}, if has been changed by the system call.
38929 After having done the needed type and value coercion, the target continues
38930 the latest continue or step action.
38932 @node The F Request Packet
38933 @subsection The @code{F} Request Packet
38934 @cindex file-i/o request packet
38935 @cindex @code{F} request packet
38937 The @code{F} request packet has the following format:
38940 @item F@var{call-id},@var{parameter@dots{}}
38942 @var{call-id} is the identifier to indicate the host system call to be called.
38943 This is just the name of the function.
38945 @var{parameter@dots{}} are the parameters to the system call.
38946 Parameters are hexadecimal integer values, either the actual values in case
38947 of scalar datatypes, pointers to target buffer space in case of compound
38948 datatypes and unspecified memory areas, or pointer/length pairs in case
38949 of string parameters. These are appended to the @var{call-id} as a
38950 comma-delimited list. All values are transmitted in ASCII
38951 string representation, pointer/length pairs separated by a slash.
38957 @node The F Reply Packet
38958 @subsection The @code{F} Reply Packet
38959 @cindex file-i/o reply packet
38960 @cindex @code{F} reply packet
38962 The @code{F} reply packet has the following format:
38966 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
38968 @var{retcode} is the return code of the system call as hexadecimal value.
38970 @var{errno} is the @code{errno} set by the call, in protocol-specific
38972 This parameter can be omitted if the call was successful.
38974 @var{Ctrl-C flag} is only sent if the user requested a break. In this
38975 case, @var{errno} must be sent as well, even if the call was successful.
38976 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
38983 or, if the call was interrupted before the host call has been performed:
38990 assuming 4 is the protocol-specific representation of @code{EINTR}.
38995 @node The Ctrl-C Message
38996 @subsection The @samp{Ctrl-C} Message
38997 @cindex ctrl-c message, in file-i/o protocol
38999 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
39000 reply packet (@pxref{The F Reply Packet}),
39001 the target should behave as if it had
39002 gotten a break message. The meaning for the target is ``system call
39003 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
39004 (as with a break message) and return to @value{GDBN} with a @code{T02}
39007 It's important for the target to know in which
39008 state the system call was interrupted. There are two possible cases:
39012 The system call hasn't been performed on the host yet.
39015 The system call on the host has been finished.
39019 These two states can be distinguished by the target by the value of the
39020 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
39021 call hasn't been performed. This is equivalent to the @code{EINTR} handling
39022 on POSIX systems. In any other case, the target may presume that the
39023 system call has been finished --- successfully or not --- and should behave
39024 as if the break message arrived right after the system call.
39026 @value{GDBN} must behave reliably. If the system call has not been called
39027 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
39028 @code{errno} in the packet. If the system call on the host has been finished
39029 before the user requests a break, the full action must be finished by
39030 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
39031 The @code{F} packet may only be sent when either nothing has happened
39032 or the full action has been completed.
39035 @subsection Console I/O
39036 @cindex console i/o as part of file-i/o
39038 By default and if not explicitly closed by the target system, the file
39039 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
39040 on the @value{GDBN} console is handled as any other file output operation
39041 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
39042 by @value{GDBN} so that after the target read request from file descriptor
39043 0 all following typing is buffered until either one of the following
39048 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
39050 system call is treated as finished.
39053 The user presses @key{RET}. This is treated as end of input with a trailing
39057 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
39058 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
39062 If the user has typed more characters than fit in the buffer given to
39063 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
39064 either another @code{read(0, @dots{})} is requested by the target, or debugging
39065 is stopped at the user's request.
39068 @node List of Supported Calls
39069 @subsection List of Supported Calls
39070 @cindex list of supported file-i/o calls
39087 @unnumberedsubsubsec open
39088 @cindex open, file-i/o system call
39093 int open(const char *pathname, int flags);
39094 int open(const char *pathname, int flags, mode_t mode);
39098 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
39101 @var{flags} is the bitwise @code{OR} of the following values:
39105 If the file does not exist it will be created. The host
39106 rules apply as far as file ownership and time stamps
39110 When used with @code{O_CREAT}, if the file already exists it is
39111 an error and open() fails.
39114 If the file already exists and the open mode allows
39115 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
39116 truncated to zero length.
39119 The file is opened in append mode.
39122 The file is opened for reading only.
39125 The file is opened for writing only.
39128 The file is opened for reading and writing.
39132 Other bits are silently ignored.
39136 @var{mode} is the bitwise @code{OR} of the following values:
39140 User has read permission.
39143 User has write permission.
39146 Group has read permission.
39149 Group has write permission.
39152 Others have read permission.
39155 Others have write permission.
39159 Other bits are silently ignored.
39162 @item Return value:
39163 @code{open} returns the new file descriptor or -1 if an error
39170 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
39173 @var{pathname} refers to a directory.
39176 The requested access is not allowed.
39179 @var{pathname} was too long.
39182 A directory component in @var{pathname} does not exist.
39185 @var{pathname} refers to a device, pipe, named pipe or socket.
39188 @var{pathname} refers to a file on a read-only filesystem and
39189 write access was requested.
39192 @var{pathname} is an invalid pointer value.
39195 No space on device to create the file.
39198 The process already has the maximum number of files open.
39201 The limit on the total number of files open on the system
39205 The call was interrupted by the user.
39211 @unnumberedsubsubsec close
39212 @cindex close, file-i/o system call
39221 @samp{Fclose,@var{fd}}
39223 @item Return value:
39224 @code{close} returns zero on success, or -1 if an error occurred.
39230 @var{fd} isn't a valid open file descriptor.
39233 The call was interrupted by the user.
39239 @unnumberedsubsubsec read
39240 @cindex read, file-i/o system call
39245 int read(int fd, void *buf, unsigned int count);
39249 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
39251 @item Return value:
39252 On success, the number of bytes read is returned.
39253 Zero indicates end of file. If count is zero, read
39254 returns zero as well. On error, -1 is returned.
39260 @var{fd} is not a valid file descriptor or is not open for
39264 @var{bufptr} is an invalid pointer value.
39267 The call was interrupted by the user.
39273 @unnumberedsubsubsec write
39274 @cindex write, file-i/o system call
39279 int write(int fd, const void *buf, unsigned int count);
39283 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
39285 @item Return value:
39286 On success, the number of bytes written are returned.
39287 Zero indicates nothing was written. On error, -1
39294 @var{fd} is not a valid file descriptor or is not open for
39298 @var{bufptr} is an invalid pointer value.
39301 An attempt was made to write a file that exceeds the
39302 host-specific maximum file size allowed.
39305 No space on device to write the data.
39308 The call was interrupted by the user.
39314 @unnumberedsubsubsec lseek
39315 @cindex lseek, file-i/o system call
39320 long lseek (int fd, long offset, int flag);
39324 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
39326 @var{flag} is one of:
39330 The offset is set to @var{offset} bytes.
39333 The offset is set to its current location plus @var{offset}
39337 The offset is set to the size of the file plus @var{offset}
39341 @item Return value:
39342 On success, the resulting unsigned offset in bytes from
39343 the beginning of the file is returned. Otherwise, a
39344 value of -1 is returned.
39350 @var{fd} is not a valid open file descriptor.
39353 @var{fd} is associated with the @value{GDBN} console.
39356 @var{flag} is not a proper value.
39359 The call was interrupted by the user.
39365 @unnumberedsubsubsec rename
39366 @cindex rename, file-i/o system call
39371 int rename(const char *oldpath, const char *newpath);
39375 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
39377 @item Return value:
39378 On success, zero is returned. On error, -1 is returned.
39384 @var{newpath} is an existing directory, but @var{oldpath} is not a
39388 @var{newpath} is a non-empty directory.
39391 @var{oldpath} or @var{newpath} is a directory that is in use by some
39395 An attempt was made to make a directory a subdirectory
39399 A component used as a directory in @var{oldpath} or new
39400 path is not a directory. Or @var{oldpath} is a directory
39401 and @var{newpath} exists but is not a directory.
39404 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
39407 No access to the file or the path of the file.
39411 @var{oldpath} or @var{newpath} was too long.
39414 A directory component in @var{oldpath} or @var{newpath} does not exist.
39417 The file is on a read-only filesystem.
39420 The device containing the file has no room for the new
39424 The call was interrupted by the user.
39430 @unnumberedsubsubsec unlink
39431 @cindex unlink, file-i/o system call
39436 int unlink(const char *pathname);
39440 @samp{Funlink,@var{pathnameptr}/@var{len}}
39442 @item Return value:
39443 On success, zero is returned. On error, -1 is returned.
39449 No access to the file or the path of the file.
39452 The system does not allow unlinking of directories.
39455 The file @var{pathname} cannot be unlinked because it's
39456 being used by another process.
39459 @var{pathnameptr} is an invalid pointer value.
39462 @var{pathname} was too long.
39465 A directory component in @var{pathname} does not exist.
39468 A component of the path is not a directory.
39471 The file is on a read-only filesystem.
39474 The call was interrupted by the user.
39480 @unnumberedsubsubsec stat/fstat
39481 @cindex fstat, file-i/o system call
39482 @cindex stat, file-i/o system call
39487 int stat(const char *pathname, struct stat *buf);
39488 int fstat(int fd, struct stat *buf);
39492 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
39493 @samp{Ffstat,@var{fd},@var{bufptr}}
39495 @item Return value:
39496 On success, zero is returned. On error, -1 is returned.
39502 @var{fd} is not a valid open file.
39505 A directory component in @var{pathname} does not exist or the
39506 path is an empty string.
39509 A component of the path is not a directory.
39512 @var{pathnameptr} is an invalid pointer value.
39515 No access to the file or the path of the file.
39518 @var{pathname} was too long.
39521 The call was interrupted by the user.
39527 @unnumberedsubsubsec gettimeofday
39528 @cindex gettimeofday, file-i/o system call
39533 int gettimeofday(struct timeval *tv, void *tz);
39537 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
39539 @item Return value:
39540 On success, 0 is returned, -1 otherwise.
39546 @var{tz} is a non-NULL pointer.
39549 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
39555 @unnumberedsubsubsec isatty
39556 @cindex isatty, file-i/o system call
39561 int isatty(int fd);
39565 @samp{Fisatty,@var{fd}}
39567 @item Return value:
39568 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
39574 The call was interrupted by the user.
39579 Note that the @code{isatty} call is treated as a special case: it returns
39580 1 to the target if the file descriptor is attached
39581 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
39582 would require implementing @code{ioctl} and would be more complex than
39587 @unnumberedsubsubsec system
39588 @cindex system, file-i/o system call
39593 int system(const char *command);
39597 @samp{Fsystem,@var{commandptr}/@var{len}}
39599 @item Return value:
39600 If @var{len} is zero, the return value indicates whether a shell is
39601 available. A zero return value indicates a shell is not available.
39602 For non-zero @var{len}, the value returned is -1 on error and the
39603 return status of the command otherwise. Only the exit status of the
39604 command is returned, which is extracted from the host's @code{system}
39605 return value by calling @code{WEXITSTATUS(retval)}. In case
39606 @file{/bin/sh} could not be executed, 127 is returned.
39612 The call was interrupted by the user.
39617 @value{GDBN} takes over the full task of calling the necessary host calls
39618 to perform the @code{system} call. The return value of @code{system} on
39619 the host is simplified before it's returned
39620 to the target. Any termination signal information from the child process
39621 is discarded, and the return value consists
39622 entirely of the exit status of the called command.
39624 Due to security concerns, the @code{system} call is by default refused
39625 by @value{GDBN}. The user has to allow this call explicitly with the
39626 @code{set remote system-call-allowed 1} command.
39629 @item set remote system-call-allowed
39630 @kindex set remote system-call-allowed
39631 Control whether to allow the @code{system} calls in the File I/O
39632 protocol for the remote target. The default is zero (disabled).
39634 @item show remote system-call-allowed
39635 @kindex show remote system-call-allowed
39636 Show whether the @code{system} calls are allowed in the File I/O
39640 @node Protocol-specific Representation of Datatypes
39641 @subsection Protocol-specific Representation of Datatypes
39642 @cindex protocol-specific representation of datatypes, in file-i/o protocol
39645 * Integral Datatypes::
39647 * Memory Transfer::
39652 @node Integral Datatypes
39653 @unnumberedsubsubsec Integral Datatypes
39654 @cindex integral datatypes, in file-i/o protocol
39656 The integral datatypes used in the system calls are @code{int},
39657 @code{unsigned int}, @code{long}, @code{unsigned long},
39658 @code{mode_t}, and @code{time_t}.
39660 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
39661 implemented as 32 bit values in this protocol.
39663 @code{long} and @code{unsigned long} are implemented as 64 bit types.
39665 @xref{Limits}, for corresponding MIN and MAX values (similar to those
39666 in @file{limits.h}) to allow range checking on host and target.
39668 @code{time_t} datatypes are defined as seconds since the Epoch.
39670 All integral datatypes transferred as part of a memory read or write of a
39671 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
39674 @node Pointer Values
39675 @unnumberedsubsubsec Pointer Values
39676 @cindex pointer values, in file-i/o protocol
39678 Pointers to target data are transmitted as they are. An exception
39679 is made for pointers to buffers for which the length isn't
39680 transmitted as part of the function call, namely strings. Strings
39681 are transmitted as a pointer/length pair, both as hex values, e.g.@:
39688 which is a pointer to data of length 18 bytes at position 0x1aaf.
39689 The length is defined as the full string length in bytes, including
39690 the trailing null byte. For example, the string @code{"hello world"}
39691 at address 0x123456 is transmitted as
39697 @node Memory Transfer
39698 @unnumberedsubsubsec Memory Transfer
39699 @cindex memory transfer, in file-i/o protocol
39701 Structured data which is transferred using a memory read or write (for
39702 example, a @code{struct stat}) is expected to be in a protocol-specific format
39703 with all scalar multibyte datatypes being big endian. Translation to
39704 this representation needs to be done both by the target before the @code{F}
39705 packet is sent, and by @value{GDBN} before
39706 it transfers memory to the target. Transferred pointers to structured
39707 data should point to the already-coerced data at any time.
39711 @unnumberedsubsubsec struct stat
39712 @cindex struct stat, in file-i/o protocol
39714 The buffer of type @code{struct stat} used by the target and @value{GDBN}
39715 is defined as follows:
39719 unsigned int st_dev; /* device */
39720 unsigned int st_ino; /* inode */
39721 mode_t st_mode; /* protection */
39722 unsigned int st_nlink; /* number of hard links */
39723 unsigned int st_uid; /* user ID of owner */
39724 unsigned int st_gid; /* group ID of owner */
39725 unsigned int st_rdev; /* device type (if inode device) */
39726 unsigned long st_size; /* total size, in bytes */
39727 unsigned long st_blksize; /* blocksize for filesystem I/O */
39728 unsigned long st_blocks; /* number of blocks allocated */
39729 time_t st_atime; /* time of last access */
39730 time_t st_mtime; /* time of last modification */
39731 time_t st_ctime; /* time of last change */
39735 The integral datatypes conform to the definitions given in the
39736 appropriate section (see @ref{Integral Datatypes}, for details) so this
39737 structure is of size 64 bytes.
39739 The values of several fields have a restricted meaning and/or
39745 A value of 0 represents a file, 1 the console.
39748 No valid meaning for the target. Transmitted unchanged.
39751 Valid mode bits are described in @ref{Constants}. Any other
39752 bits have currently no meaning for the target.
39757 No valid meaning for the target. Transmitted unchanged.
39762 These values have a host and file system dependent
39763 accuracy. Especially on Windows hosts, the file system may not
39764 support exact timing values.
39767 The target gets a @code{struct stat} of the above representation and is
39768 responsible for coercing it to the target representation before
39771 Note that due to size differences between the host, target, and protocol
39772 representations of @code{struct stat} members, these members could eventually
39773 get truncated on the target.
39775 @node struct timeval
39776 @unnumberedsubsubsec struct timeval
39777 @cindex struct timeval, in file-i/o protocol
39779 The buffer of type @code{struct timeval} used by the File-I/O protocol
39780 is defined as follows:
39784 time_t tv_sec; /* second */
39785 long tv_usec; /* microsecond */
39789 The integral datatypes conform to the definitions given in the
39790 appropriate section (see @ref{Integral Datatypes}, for details) so this
39791 structure is of size 8 bytes.
39794 @subsection Constants
39795 @cindex constants, in file-i/o protocol
39797 The following values are used for the constants inside of the
39798 protocol. @value{GDBN} and target are responsible for translating these
39799 values before and after the call as needed.
39810 @unnumberedsubsubsec Open Flags
39811 @cindex open flags, in file-i/o protocol
39813 All values are given in hexadecimal representation.
39825 @node mode_t Values
39826 @unnumberedsubsubsec mode_t Values
39827 @cindex mode_t values, in file-i/o protocol
39829 All values are given in octal representation.
39846 @unnumberedsubsubsec Errno Values
39847 @cindex errno values, in file-i/o protocol
39849 All values are given in decimal representation.
39874 @code{EUNKNOWN} is used as a fallback error value if a host system returns
39875 any error value not in the list of supported error numbers.
39878 @unnumberedsubsubsec Lseek Flags
39879 @cindex lseek flags, in file-i/o protocol
39888 @unnumberedsubsubsec Limits
39889 @cindex limits, in file-i/o protocol
39891 All values are given in decimal representation.
39894 INT_MIN -2147483648
39896 UINT_MAX 4294967295
39897 LONG_MIN -9223372036854775808
39898 LONG_MAX 9223372036854775807
39899 ULONG_MAX 18446744073709551615
39902 @node File-I/O Examples
39903 @subsection File-I/O Examples
39904 @cindex file-i/o examples
39906 Example sequence of a write call, file descriptor 3, buffer is at target
39907 address 0x1234, 6 bytes should be written:
39910 <- @code{Fwrite,3,1234,6}
39911 @emph{request memory read from target}
39914 @emph{return "6 bytes written"}
39918 Example sequence of a read call, file descriptor 3, buffer is at target
39919 address 0x1234, 6 bytes should be read:
39922 <- @code{Fread,3,1234,6}
39923 @emph{request memory write to target}
39924 -> @code{X1234,6:XXXXXX}
39925 @emph{return "6 bytes read"}
39929 Example sequence of a read call, call fails on the host due to invalid
39930 file descriptor (@code{EBADF}):
39933 <- @code{Fread,3,1234,6}
39937 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
39941 <- @code{Fread,3,1234,6}
39946 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
39950 <- @code{Fread,3,1234,6}
39951 -> @code{X1234,6:XXXXXX}
39955 @node Library List Format
39956 @section Library List Format
39957 @cindex library list format, remote protocol
39959 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
39960 same process as your application to manage libraries. In this case,
39961 @value{GDBN} can use the loader's symbol table and normal memory
39962 operations to maintain a list of shared libraries. On other
39963 platforms, the operating system manages loaded libraries.
39964 @value{GDBN} can not retrieve the list of currently loaded libraries
39965 through memory operations, so it uses the @samp{qXfer:libraries:read}
39966 packet (@pxref{qXfer library list read}) instead. The remote stub
39967 queries the target's operating system and reports which libraries
39970 The @samp{qXfer:libraries:read} packet returns an XML document which
39971 lists loaded libraries and their offsets. Each library has an
39972 associated name and one or more segment or section base addresses,
39973 which report where the library was loaded in memory.
39975 For the common case of libraries that are fully linked binaries, the
39976 library should have a list of segments. If the target supports
39977 dynamic linking of a relocatable object file, its library XML element
39978 should instead include a list of allocated sections. The segment or
39979 section bases are start addresses, not relocation offsets; they do not
39980 depend on the library's link-time base addresses.
39982 @value{GDBN} must be linked with the Expat library to support XML
39983 library lists. @xref{Expat}.
39985 A simple memory map, with one loaded library relocated by a single
39986 offset, looks like this:
39990 <library name="/lib/libc.so.6">
39991 <segment address="0x10000000"/>
39996 Another simple memory map, with one loaded library with three
39997 allocated sections (.text, .data, .bss), looks like this:
40001 <library name="sharedlib.o">
40002 <section address="0x10000000"/>
40003 <section address="0x20000000"/>
40004 <section address="0x30000000"/>
40009 The format of a library list is described by this DTD:
40012 <!-- library-list: Root element with versioning -->
40013 <!ELEMENT library-list (library)*>
40014 <!ATTLIST library-list version CDATA #FIXED "1.0">
40015 <!ELEMENT library (segment*, section*)>
40016 <!ATTLIST library name CDATA #REQUIRED>
40017 <!ELEMENT segment EMPTY>
40018 <!ATTLIST segment address CDATA #REQUIRED>
40019 <!ELEMENT section EMPTY>
40020 <!ATTLIST section address CDATA #REQUIRED>
40023 In addition, segments and section descriptors cannot be mixed within a
40024 single library element, and you must supply at least one segment or
40025 section for each library.
40027 @node Library List Format for SVR4 Targets
40028 @section Library List Format for SVR4 Targets
40029 @cindex library list format, remote protocol
40031 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
40032 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
40033 shared libraries. Still a special library list provided by this packet is
40034 more efficient for the @value{GDBN} remote protocol.
40036 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
40037 loaded libraries and their SVR4 linker parameters. For each library on SVR4
40038 target, the following parameters are reported:
40042 @code{name}, the absolute file name from the @code{l_name} field of
40043 @code{struct link_map}.
40045 @code{lm} with address of @code{struct link_map} used for TLS
40046 (Thread Local Storage) access.
40048 @code{l_addr}, the displacement as read from the field @code{l_addr} of
40049 @code{struct link_map}. For prelinked libraries this is not an absolute
40050 memory address. It is a displacement of absolute memory address against
40051 address the file was prelinked to during the library load.
40053 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
40056 Additionally the single @code{main-lm} attribute specifies address of
40057 @code{struct link_map} used for the main executable. This parameter is used
40058 for TLS access and its presence is optional.
40060 @value{GDBN} must be linked with the Expat library to support XML
40061 SVR4 library lists. @xref{Expat}.
40063 A simple memory map, with two loaded libraries (which do not use prelink),
40067 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
40068 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
40070 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
40072 </library-list-svr>
40075 The format of an SVR4 library list is described by this DTD:
40078 <!-- library-list-svr4: Root element with versioning -->
40079 <!ELEMENT library-list-svr4 (library)*>
40080 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
40081 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
40082 <!ELEMENT library EMPTY>
40083 <!ATTLIST library name CDATA #REQUIRED>
40084 <!ATTLIST library lm CDATA #REQUIRED>
40085 <!ATTLIST library l_addr CDATA #REQUIRED>
40086 <!ATTLIST library l_ld CDATA #REQUIRED>
40089 @node Memory Map Format
40090 @section Memory Map Format
40091 @cindex memory map format
40093 To be able to write into flash memory, @value{GDBN} needs to obtain a
40094 memory map from the target. This section describes the format of the
40097 The memory map is obtained using the @samp{qXfer:memory-map:read}
40098 (@pxref{qXfer memory map read}) packet and is an XML document that
40099 lists memory regions.
40101 @value{GDBN} must be linked with the Expat library to support XML
40102 memory maps. @xref{Expat}.
40104 The top-level structure of the document is shown below:
40107 <?xml version="1.0"?>
40108 <!DOCTYPE memory-map
40109 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
40110 "http://sourceware.org/gdb/gdb-memory-map.dtd">
40116 Each region can be either:
40121 A region of RAM starting at @var{addr} and extending for @var{length}
40125 <memory type="ram" start="@var{addr}" length="@var{length}"/>
40130 A region of read-only memory:
40133 <memory type="rom" start="@var{addr}" length="@var{length}"/>
40138 A region of flash memory, with erasure blocks @var{blocksize}
40142 <memory type="flash" start="@var{addr}" length="@var{length}">
40143 <property name="blocksize">@var{blocksize}</property>
40149 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
40150 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
40151 packets to write to addresses in such ranges.
40153 The formal DTD for memory map format is given below:
40156 <!-- ................................................... -->
40157 <!-- Memory Map XML DTD ................................ -->
40158 <!-- File: memory-map.dtd .............................. -->
40159 <!-- .................................... .............. -->
40160 <!-- memory-map.dtd -->
40161 <!-- memory-map: Root element with versioning -->
40162 <!ELEMENT memory-map (memory | property)>
40163 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
40164 <!ELEMENT memory (property)>
40165 <!-- memory: Specifies a memory region,
40166 and its type, or device. -->
40167 <!ATTLIST memory type CDATA #REQUIRED
40168 start CDATA #REQUIRED
40169 length CDATA #REQUIRED
40170 device CDATA #IMPLIED>
40171 <!-- property: Generic attribute tag -->
40172 <!ELEMENT property (#PCDATA | property)*>
40173 <!ATTLIST property name CDATA #REQUIRED>
40176 @node Thread List Format
40177 @section Thread List Format
40178 @cindex thread list format
40180 To efficiently update the list of threads and their attributes,
40181 @value{GDBN} issues the @samp{qXfer:threads:read} packet
40182 (@pxref{qXfer threads read}) and obtains the XML document with
40183 the following structure:
40186 <?xml version="1.0"?>
40188 <thread id="id" core="0" name="name">
40189 ... description ...
40194 Each @samp{thread} element must have the @samp{id} attribute that
40195 identifies the thread (@pxref{thread-id syntax}). The
40196 @samp{core} attribute, if present, specifies which processor core
40197 the thread was last executing on. The @samp{name} attribute, if
40198 present, specifies the human-readable name of the thread. The content
40199 of the of @samp{thread} element is interpreted as human-readable
40200 auxiliary information.
40202 @node Traceframe Info Format
40203 @section Traceframe Info Format
40204 @cindex traceframe info format
40206 To be able to know which objects in the inferior can be examined when
40207 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
40208 memory ranges, registers and trace state variables that have been
40209 collected in a traceframe.
40211 This list is obtained using the @samp{qXfer:traceframe-info:read}
40212 (@pxref{qXfer traceframe info read}) packet and is an XML document.
40214 @value{GDBN} must be linked with the Expat library to support XML
40215 traceframe info discovery. @xref{Expat}.
40217 The top-level structure of the document is shown below:
40220 <?xml version="1.0"?>
40221 <!DOCTYPE traceframe-info
40222 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
40223 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
40229 Each traceframe block can be either:
40234 A region of collected memory starting at @var{addr} and extending for
40235 @var{length} bytes from there:
40238 <memory start="@var{addr}" length="@var{length}"/>
40242 A block indicating trace state variable numbered @var{number} has been
40246 <tvar id="@var{number}"/>
40251 The formal DTD for the traceframe info format is given below:
40254 <!ELEMENT traceframe-info (memory | tvar)* >
40255 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
40257 <!ELEMENT memory EMPTY>
40258 <!ATTLIST memory start CDATA #REQUIRED
40259 length CDATA #REQUIRED>
40261 <!ATTLIST tvar id CDATA #REQUIRED>
40264 @node Branch Trace Format
40265 @section Branch Trace Format
40266 @cindex branch trace format
40268 In order to display the branch trace of an inferior thread,
40269 @value{GDBN} needs to obtain the list of branches. This list is
40270 represented as list of sequential code blocks that are connected via
40271 branches. The code in each block has been executed sequentially.
40273 This list is obtained using the @samp{qXfer:btrace:read}
40274 (@pxref{qXfer btrace read}) packet and is an XML document.
40276 @value{GDBN} must be linked with the Expat library to support XML
40277 traceframe info discovery. @xref{Expat}.
40279 The top-level structure of the document is shown below:
40282 <?xml version="1.0"?>
40284 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
40285 "http://sourceware.org/gdb/gdb-btrace.dtd">
40294 A block of sequentially executed instructions starting at @var{begin}
40295 and ending at @var{end}:
40298 <block begin="@var{begin}" end="@var{end}"/>
40303 The formal DTD for the branch trace format is given below:
40306 <!ELEMENT btrace (block* | pt) >
40307 <!ATTLIST btrace version CDATA #FIXED "1.0">
40309 <!ELEMENT block EMPTY>
40310 <!ATTLIST block begin CDATA #REQUIRED
40311 end CDATA #REQUIRED>
40313 <!ELEMENT pt (pt-config?, raw?)>
40315 <!ELEMENT pt-config (cpu?)>
40317 <!ELEMENT cpu EMPTY>
40318 <!ATTLIST cpu vendor CDATA #REQUIRED
40319 family CDATA #REQUIRED
40320 model CDATA #REQUIRED
40321 stepping CDATA #REQUIRED>
40323 <!ELEMENT raw (#PCDATA)>
40326 @node Branch Trace Configuration Format
40327 @section Branch Trace Configuration Format
40328 @cindex branch trace configuration format
40330 For each inferior thread, @value{GDBN} can obtain the branch trace
40331 configuration using the @samp{qXfer:btrace-conf:read}
40332 (@pxref{qXfer btrace-conf read}) packet.
40334 The configuration describes the branch trace format and configuration
40335 settings for that format. The following information is described:
40339 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
40342 The size of the @acronym{BTS} ring buffer in bytes.
40345 This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
40349 The size of the @acronym{Intel PT} ring buffer in bytes.
40353 @value{GDBN} must be linked with the Expat library to support XML
40354 branch trace configuration discovery. @xref{Expat}.
40356 The formal DTD for the branch trace configuration format is given below:
40359 <!ELEMENT btrace-conf (bts?, pt?)>
40360 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
40362 <!ELEMENT bts EMPTY>
40363 <!ATTLIST bts size CDATA #IMPLIED>
40365 <!ELEMENT pt EMPTY>
40366 <!ATTLIST pt size CDATA #IMPLIED>
40369 @include agentexpr.texi
40371 @node Target Descriptions
40372 @appendix Target Descriptions
40373 @cindex target descriptions
40375 One of the challenges of using @value{GDBN} to debug embedded systems
40376 is that there are so many minor variants of each processor
40377 architecture in use. It is common practice for vendors to start with
40378 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
40379 and then make changes to adapt it to a particular market niche. Some
40380 architectures have hundreds of variants, available from dozens of
40381 vendors. This leads to a number of problems:
40385 With so many different customized processors, it is difficult for
40386 the @value{GDBN} maintainers to keep up with the changes.
40388 Since individual variants may have short lifetimes or limited
40389 audiences, it may not be worthwhile to carry information about every
40390 variant in the @value{GDBN} source tree.
40392 When @value{GDBN} does support the architecture of the embedded system
40393 at hand, the task of finding the correct architecture name to give the
40394 @command{set architecture} command can be error-prone.
40397 To address these problems, the @value{GDBN} remote protocol allows a
40398 target system to not only identify itself to @value{GDBN}, but to
40399 actually describe its own features. This lets @value{GDBN} support
40400 processor variants it has never seen before --- to the extent that the
40401 descriptions are accurate, and that @value{GDBN} understands them.
40403 @value{GDBN} must be linked with the Expat library to support XML
40404 target descriptions. @xref{Expat}.
40407 * Retrieving Descriptions:: How descriptions are fetched from a target.
40408 * Target Description Format:: The contents of a target description.
40409 * Predefined Target Types:: Standard types available for target
40411 * Enum Target Types:: How to define enum target types.
40412 * Standard Target Features:: Features @value{GDBN} knows about.
40415 @node Retrieving Descriptions
40416 @section Retrieving Descriptions
40418 Target descriptions can be read from the target automatically, or
40419 specified by the user manually. The default behavior is to read the
40420 description from the target. @value{GDBN} retrieves it via the remote
40421 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
40422 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
40423 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
40424 XML document, of the form described in @ref{Target Description
40427 Alternatively, you can specify a file to read for the target description.
40428 If a file is set, the target will not be queried. The commands to
40429 specify a file are:
40432 @cindex set tdesc filename
40433 @item set tdesc filename @var{path}
40434 Read the target description from @var{path}.
40436 @cindex unset tdesc filename
40437 @item unset tdesc filename
40438 Do not read the XML target description from a file. @value{GDBN}
40439 will use the description supplied by the current target.
40441 @cindex show tdesc filename
40442 @item show tdesc filename
40443 Show the filename to read for a target description, if any.
40447 @node Target Description Format
40448 @section Target Description Format
40449 @cindex target descriptions, XML format
40451 A target description annex is an @uref{http://www.w3.org/XML/, XML}
40452 document which complies with the Document Type Definition provided in
40453 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
40454 means you can use generally available tools like @command{xmllint} to
40455 check that your feature descriptions are well-formed and valid.
40456 However, to help people unfamiliar with XML write descriptions for
40457 their targets, we also describe the grammar here.
40459 Target descriptions can identify the architecture of the remote target
40460 and (for some architectures) provide information about custom register
40461 sets. They can also identify the OS ABI of the remote target.
40462 @value{GDBN} can use this information to autoconfigure for your
40463 target, or to warn you if you connect to an unsupported target.
40465 Here is a simple target description:
40468 <target version="1.0">
40469 <architecture>i386:x86-64</architecture>
40474 This minimal description only says that the target uses
40475 the x86-64 architecture.
40477 A target description has the following overall form, with [ ] marking
40478 optional elements and @dots{} marking repeatable elements. The elements
40479 are explained further below.
40482 <?xml version="1.0"?>
40483 <!DOCTYPE target SYSTEM "gdb-target.dtd">
40484 <target version="1.0">
40485 @r{[}@var{architecture}@r{]}
40486 @r{[}@var{osabi}@r{]}
40487 @r{[}@var{compatible}@r{]}
40488 @r{[}@var{feature}@dots{}@r{]}
40493 The description is generally insensitive to whitespace and line
40494 breaks, under the usual common-sense rules. The XML version
40495 declaration and document type declaration can generally be omitted
40496 (@value{GDBN} does not require them), but specifying them may be
40497 useful for XML validation tools. The @samp{version} attribute for
40498 @samp{<target>} may also be omitted, but we recommend
40499 including it; if future versions of @value{GDBN} use an incompatible
40500 revision of @file{gdb-target.dtd}, they will detect and report
40501 the version mismatch.
40503 @subsection Inclusion
40504 @cindex target descriptions, inclusion
40507 @cindex <xi:include>
40510 It can sometimes be valuable to split a target description up into
40511 several different annexes, either for organizational purposes, or to
40512 share files between different possible target descriptions. You can
40513 divide a description into multiple files by replacing any element of
40514 the target description with an inclusion directive of the form:
40517 <xi:include href="@var{document}"/>
40521 When @value{GDBN} encounters an element of this form, it will retrieve
40522 the named XML @var{document}, and replace the inclusion directive with
40523 the contents of that document. If the current description was read
40524 using @samp{qXfer}, then so will be the included document;
40525 @var{document} will be interpreted as the name of an annex. If the
40526 current description was read from a file, @value{GDBN} will look for
40527 @var{document} as a file in the same directory where it found the
40528 original description.
40530 @subsection Architecture
40531 @cindex <architecture>
40533 An @samp{<architecture>} element has this form:
40536 <architecture>@var{arch}</architecture>
40539 @var{arch} is one of the architectures from the set accepted by
40540 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40543 @cindex @code{<osabi>}
40545 This optional field was introduced in @value{GDBN} version 7.0.
40546 Previous versions of @value{GDBN} ignore it.
40548 An @samp{<osabi>} element has this form:
40551 <osabi>@var{abi-name}</osabi>
40554 @var{abi-name} is an OS ABI name from the same selection accepted by
40555 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
40557 @subsection Compatible Architecture
40558 @cindex @code{<compatible>}
40560 This optional field was introduced in @value{GDBN} version 7.0.
40561 Previous versions of @value{GDBN} ignore it.
40563 A @samp{<compatible>} element has this form:
40566 <compatible>@var{arch}</compatible>
40569 @var{arch} is one of the architectures from the set accepted by
40570 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40572 A @samp{<compatible>} element is used to specify that the target
40573 is able to run binaries in some other than the main target architecture
40574 given by the @samp{<architecture>} element. For example, on the
40575 Cell Broadband Engine, the main architecture is @code{powerpc:common}
40576 or @code{powerpc:common64}, but the system is able to run binaries
40577 in the @code{spu} architecture as well. The way to describe this
40578 capability with @samp{<compatible>} is as follows:
40581 <architecture>powerpc:common</architecture>
40582 <compatible>spu</compatible>
40585 @subsection Features
40588 Each @samp{<feature>} describes some logical portion of the target
40589 system. Features are currently used to describe available CPU
40590 registers and the types of their contents. A @samp{<feature>} element
40594 <feature name="@var{name}">
40595 @r{[}@var{type}@dots{}@r{]}
40601 Each feature's name should be unique within the description. The name
40602 of a feature does not matter unless @value{GDBN} has some special
40603 knowledge of the contents of that feature; if it does, the feature
40604 should have its standard name. @xref{Standard Target Features}.
40608 Any register's value is a collection of bits which @value{GDBN} must
40609 interpret. The default interpretation is a two's complement integer,
40610 but other types can be requested by name in the register description.
40611 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
40612 Target Types}), and the description can define additional composite
40615 Each type element must have an @samp{id} attribute, which gives
40616 a unique (within the containing @samp{<feature>}) name to the type.
40617 Types must be defined before they are used.
40620 Some targets offer vector registers, which can be treated as arrays
40621 of scalar elements. These types are written as @samp{<vector>} elements,
40622 specifying the array element type, @var{type}, and the number of elements,
40626 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
40630 If a register's value is usefully viewed in multiple ways, define it
40631 with a union type containing the useful representations. The
40632 @samp{<union>} element contains one or more @samp{<field>} elements,
40633 each of which has a @var{name} and a @var{type}:
40636 <union id="@var{id}">
40637 <field name="@var{name}" type="@var{type}"/>
40644 If a register's value is composed from several separate values, define
40645 it with either a structure type or a flags type.
40646 A flags type may only contain bitfields.
40647 A structure type may either contain only bitfields or contain no bitfields.
40648 If the value contains only bitfields, its total size in bytes must be
40651 Non-bitfield values have a @var{name} and @var{type}.
40654 <struct id="@var{id}">
40655 <field name="@var{name}" type="@var{type}"/>
40660 Both @var{name} and @var{type} values are required.
40661 No implicit padding is added.
40663 Bitfield values have a @var{name}, @var{start}, @var{end} and @var{type}.
40666 <struct id="@var{id}" size="@var{size}">
40667 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
40673 <flags id="@var{id}" size="@var{size}">
40674 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
40679 The @var{name} value is required.
40680 Bitfield values may be named with the empty string, @samp{""},
40681 in which case the field is ``filler'' and its value is not printed.
40682 Not all bits need to be specified, so ``filler'' fields are optional.
40684 The @var{start} value is required, and @var{end} and @var{type}
40686 The field's @var{start} must be less than or equal to its @var{end},
40687 and zero represents the least significant bit.
40688 The default value of @var{end} is @var{start}, a single bit field.
40690 The default value of @var{type} depends on whether the
40691 @var{end} was specified. If @var{end} is specified then the default
40692 value of @var{type} is an unsigned integer. If @var{end} is unspecified
40693 then the default value of @var{type} is @code{bool}.
40695 Which to choose? Structures or flags?
40697 Registers defined with @samp{flags} have these advantages over
40698 defining them with @samp{struct}:
40702 Arithmetic may be performed on them as if they were integers.
40704 They are printed in a more readable fashion.
40707 Registers defined with @samp{struct} have one advantage over
40708 defining them with @samp{flags}:
40712 One can fetch individual fields like in @samp{C}.
40715 (gdb) print $my_struct_reg.field3
40721 @subsection Registers
40724 Each register is represented as an element with this form:
40727 <reg name="@var{name}"
40728 bitsize="@var{size}"
40729 @r{[}regnum="@var{num}"@r{]}
40730 @r{[}save-restore="@var{save-restore}"@r{]}
40731 @r{[}type="@var{type}"@r{]}
40732 @r{[}group="@var{group}"@r{]}/>
40736 The components are as follows:
40741 The register's name; it must be unique within the target description.
40744 The register's size, in bits.
40747 The register's number. If omitted, a register's number is one greater
40748 than that of the previous register (either in the current feature or in
40749 a preceding feature); the first register in the target description
40750 defaults to zero. This register number is used to read or write
40751 the register; e.g.@: it is used in the remote @code{p} and @code{P}
40752 packets, and registers appear in the @code{g} and @code{G} packets
40753 in order of increasing register number.
40756 Whether the register should be preserved across inferior function
40757 calls; this must be either @code{yes} or @code{no}. The default is
40758 @code{yes}, which is appropriate for most registers except for
40759 some system control registers; this is not related to the target's
40763 The type of the register. It may be a predefined type, a type
40764 defined in the current feature, or one of the special types @code{int}
40765 and @code{float}. @code{int} is an integer type of the correct size
40766 for @var{bitsize}, and @code{float} is a floating point type (in the
40767 architecture's normal floating point format) of the correct size for
40768 @var{bitsize}. The default is @code{int}.
40771 The register group to which this register belongs. It must
40772 be either @code{general}, @code{float}, or @code{vector}. If no
40773 @var{group} is specified, @value{GDBN} will not display the register
40774 in @code{info registers}.
40778 @node Predefined Target Types
40779 @section Predefined Target Types
40780 @cindex target descriptions, predefined types
40782 Type definitions in the self-description can build up composite types
40783 from basic building blocks, but can not define fundamental types. Instead,
40784 standard identifiers are provided by @value{GDBN} for the fundamental
40785 types. The currently supported types are:
40790 Boolean type, occupying a single bit.
40797 Signed integer types holding the specified number of bits.
40804 Unsigned integer types holding the specified number of bits.
40808 Pointers to unspecified code and data. The program counter and
40809 any dedicated return address register may be marked as code
40810 pointers; printing a code pointer converts it into a symbolic
40811 address. The stack pointer and any dedicated address registers
40812 may be marked as data pointers.
40815 Single precision IEEE floating point.
40818 Double precision IEEE floating point.
40821 The 12-byte extended precision format used by ARM FPA registers.
40824 The 10-byte extended precision format used by x87 registers.
40827 32bit @sc{eflags} register used by x86.
40830 32bit @sc{mxcsr} register used by x86.
40834 @node Enum Target Types
40835 @section Enum Target Types
40836 @cindex target descriptions, enum types
40838 Enum target types are useful in @samp{struct} and @samp{flags}
40839 register descriptions. @xref{Target Description Format}.
40841 Enum types have a name, size and a list of name/value pairs.
40844 <enum id="@var{id}" size="@var{size}">
40845 <evalue name="@var{name}" value="@var{value}"/>
40850 Enums must be defined before they are used.
40853 <enum id="levels_type" size="4">
40854 <evalue name="low" value="0"/>
40855 <evalue name="high" value="1"/>
40857 <flags id="flags_type" size="4">
40858 <field name="X" start="0"/>
40859 <field name="LEVEL" start="1" end="1" type="levels_type"/>
40861 <reg name="flags" bitsize="32" type="flags_type"/>
40864 Given that description, a value of 3 for the @samp{flags} register
40865 would be printed as:
40868 (gdb) info register flags
40869 flags 0x3 [ X LEVEL=high ]
40872 @node Standard Target Features
40873 @section Standard Target Features
40874 @cindex target descriptions, standard features
40876 A target description must contain either no registers or all the
40877 target's registers. If the description contains no registers, then
40878 @value{GDBN} will assume a default register layout, selected based on
40879 the architecture. If the description contains any registers, the
40880 default layout will not be used; the standard registers must be
40881 described in the target description, in such a way that @value{GDBN}
40882 can recognize them.
40884 This is accomplished by giving specific names to feature elements
40885 which contain standard registers. @value{GDBN} will look for features
40886 with those names and verify that they contain the expected registers;
40887 if any known feature is missing required registers, or if any required
40888 feature is missing, @value{GDBN} will reject the target
40889 description. You can add additional registers to any of the
40890 standard features --- @value{GDBN} will display them just as if
40891 they were added to an unrecognized feature.
40893 This section lists the known features and their expected contents.
40894 Sample XML documents for these features are included in the
40895 @value{GDBN} source tree, in the directory @file{gdb/features}.
40897 Names recognized by @value{GDBN} should include the name of the
40898 company or organization which selected the name, and the overall
40899 architecture to which the feature applies; so e.g.@: the feature
40900 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
40902 The names of registers are not case sensitive for the purpose
40903 of recognizing standard features, but @value{GDBN} will only display
40904 registers using the capitalization used in the description.
40907 * AArch64 Features::
40910 * MicroBlaze Features::
40914 * Nios II Features::
40915 * PowerPC Features::
40916 * S/390 and System z Features::
40921 @node AArch64 Features
40922 @subsection AArch64 Features
40923 @cindex target descriptions, AArch64 features
40925 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
40926 targets. It should contain registers @samp{x0} through @samp{x30},
40927 @samp{sp}, @samp{pc}, and @samp{cpsr}.
40929 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
40930 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
40934 @subsection ARM Features
40935 @cindex target descriptions, ARM features
40937 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
40939 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
40940 @samp{lr}, @samp{pc}, and @samp{cpsr}.
40942 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
40943 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
40944 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
40947 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
40948 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
40950 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
40951 it should contain at least registers @samp{wR0} through @samp{wR15} and
40952 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
40953 @samp{wCSSF}, and @samp{wCASF} registers are optional.
40955 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
40956 should contain at least registers @samp{d0} through @samp{d15}. If
40957 they are present, @samp{d16} through @samp{d31} should also be included.
40958 @value{GDBN} will synthesize the single-precision registers from
40959 halves of the double-precision registers.
40961 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
40962 need to contain registers; it instructs @value{GDBN} to display the
40963 VFP double-precision registers as vectors and to synthesize the
40964 quad-precision registers from pairs of double-precision registers.
40965 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
40966 be present and include 32 double-precision registers.
40968 @node i386 Features
40969 @subsection i386 Features
40970 @cindex target descriptions, i386 features
40972 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
40973 targets. It should describe the following registers:
40977 @samp{eax} through @samp{edi} plus @samp{eip} for i386
40979 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
40981 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
40982 @samp{fs}, @samp{gs}
40984 @samp{st0} through @samp{st7}
40986 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
40987 @samp{foseg}, @samp{fooff} and @samp{fop}
40990 The register sets may be different, depending on the target.
40992 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
40993 describe registers:
40997 @samp{xmm0} through @samp{xmm7} for i386
40999 @samp{xmm0} through @samp{xmm15} for amd64
41004 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
41005 @samp{org.gnu.gdb.i386.sse} feature. It should
41006 describe the upper 128 bits of @sc{ymm} registers:
41010 @samp{ymm0h} through @samp{ymm7h} for i386
41012 @samp{ymm0h} through @samp{ymm15h} for amd64
41015 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
41016 Memory Protection Extension (MPX). It should describe the following registers:
41020 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
41022 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
41025 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
41026 describe a single register, @samp{orig_eax}.
41028 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
41029 @samp{org.gnu.gdb.i386.avx} feature. It should
41030 describe additional @sc{xmm} registers:
41034 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
41037 It should describe the upper 128 bits of additional @sc{ymm} registers:
41041 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
41045 describe the upper 256 bits of @sc{zmm} registers:
41049 @samp{zmm0h} through @samp{zmm7h} for i386.
41051 @samp{zmm0h} through @samp{zmm15h} for amd64.
41055 describe the additional @sc{zmm} registers:
41059 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
41062 @node MicroBlaze Features
41063 @subsection MicroBlaze Features
41064 @cindex target descriptions, MicroBlaze features
41066 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
41067 targets. It should contain registers @samp{r0} through @samp{r31},
41068 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
41069 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
41070 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
41072 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
41073 If present, it should contain registers @samp{rshr} and @samp{rslr}
41075 @node MIPS Features
41076 @subsection @acronym{MIPS} Features
41077 @cindex target descriptions, @acronym{MIPS} features
41079 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
41080 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
41081 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
41084 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
41085 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
41086 registers. They may be 32-bit or 64-bit depending on the target.
41088 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
41089 it may be optional in a future version of @value{GDBN}. It should
41090 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
41091 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
41093 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
41094 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
41095 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
41096 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
41098 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
41099 contain a single register, @samp{restart}, which is used by the
41100 Linux kernel to control restartable syscalls.
41102 @node M68K Features
41103 @subsection M68K Features
41104 @cindex target descriptions, M68K features
41107 @item @samp{org.gnu.gdb.m68k.core}
41108 @itemx @samp{org.gnu.gdb.coldfire.core}
41109 @itemx @samp{org.gnu.gdb.fido.core}
41110 One of those features must be always present.
41111 The feature that is present determines which flavor of m68k is
41112 used. The feature that is present should contain registers
41113 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
41114 @samp{sp}, @samp{ps} and @samp{pc}.
41116 @item @samp{org.gnu.gdb.coldfire.fp}
41117 This feature is optional. If present, it should contain registers
41118 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
41122 @node NDS32 Features
41123 @subsection NDS32 Features
41124 @cindex target descriptions, NDS32 features
41126 The @samp{org.gnu.gdb.nds32.core} feature is required for NDS32
41127 targets. It should contain at least registers @samp{r0} through
41128 @samp{r10}, @samp{r15}, @samp{fp}, @samp{gp}, @samp{lp}, @samp{sp},
41131 The @samp{org.gnu.gdb.nds32.fpu} feature is optional. If present,
41132 it should contain 64-bit double-precision floating-point registers
41133 @samp{fd0} through @emph{fdN}, which should be @samp{fd3}, @samp{fd7},
41134 @samp{fd15}, or @samp{fd31} based on the FPU configuration implemented.
41136 @emph{Note:} The first sixteen 64-bit double-precision floating-point
41137 registers are overlapped with the thirty-two 32-bit single-precision
41138 floating-point registers. The 32-bit single-precision registers, if
41139 not being listed explicitly, will be synthesized from halves of the
41140 overlapping 64-bit double-precision registers. Listing 32-bit
41141 single-precision registers explicitly is deprecated, and the
41142 support to it could be totally removed some day.
41144 @node Nios II Features
41145 @subsection Nios II Features
41146 @cindex target descriptions, Nios II features
41148 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
41149 targets. It should contain the 32 core registers (@samp{zero},
41150 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
41151 @samp{pc}, and the 16 control registers (@samp{status} through
41154 @node PowerPC Features
41155 @subsection PowerPC Features
41156 @cindex target descriptions, PowerPC features
41158 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
41159 targets. It should contain registers @samp{r0} through @samp{r31},
41160 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
41161 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
41163 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
41164 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
41166 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
41167 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
41170 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
41171 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
41172 will combine these registers with the floating point registers
41173 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
41174 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
41175 through @samp{vs63}, the set of vector registers for POWER7.
41177 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
41178 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
41179 @samp{spefscr}. SPE targets should provide 32-bit registers in
41180 @samp{org.gnu.gdb.power.core} and provide the upper halves in
41181 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
41182 these to present registers @samp{ev0} through @samp{ev31} to the
41185 @node S/390 and System z Features
41186 @subsection S/390 and System z Features
41187 @cindex target descriptions, S/390 features
41188 @cindex target descriptions, System z features
41190 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
41191 System z targets. It should contain the PSW and the 16 general
41192 registers. In particular, System z targets should provide the 64-bit
41193 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
41194 S/390 targets should provide the 32-bit versions of these registers.
41195 A System z target that runs in 31-bit addressing mode should provide
41196 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
41197 register's upper halves @samp{r0h} through @samp{r15h}, and their
41198 lower halves @samp{r0l} through @samp{r15l}.
41200 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
41201 contain the 64-bit registers @samp{f0} through @samp{f15}, and
41204 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
41205 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
41207 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
41208 contain the register @samp{orig_r2}, which is 64-bit wide on System z
41209 targets and 32-bit otherwise. In addition, the feature may contain
41210 the @samp{last_break} register, whose width depends on the addressing
41211 mode, as well as the @samp{system_call} register, which is always
41214 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
41215 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
41216 @samp{atia}, and @samp{tr0} through @samp{tr15}.
41218 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
41219 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
41220 combined by @value{GDBN} with the floating point registers @samp{f0}
41221 through @samp{f15} to present the 128-bit wide vector registers
41222 @samp{v0} through @samp{v15}. In addition, this feature should
41223 contain the 128-bit wide vector registers @samp{v16} through
41226 @node TIC6x Features
41227 @subsection TMS320C6x Features
41228 @cindex target descriptions, TIC6x features
41229 @cindex target descriptions, TMS320C6x features
41230 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
41231 targets. It should contain registers @samp{A0} through @samp{A15},
41232 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
41234 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
41235 contain registers @samp{A16} through @samp{A31} and @samp{B16}
41236 through @samp{B31}.
41238 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
41239 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
41241 @node Operating System Information
41242 @appendix Operating System Information
41243 @cindex operating system information
41249 Users of @value{GDBN} often wish to obtain information about the state of
41250 the operating system running on the target---for example the list of
41251 processes, or the list of open files. This section describes the
41252 mechanism that makes it possible. This mechanism is similar to the
41253 target features mechanism (@pxref{Target Descriptions}), but focuses
41254 on a different aspect of target.
41256 Operating system information is retrived from the target via the
41257 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
41258 read}). The object name in the request should be @samp{osdata}, and
41259 the @var{annex} identifies the data to be fetched.
41262 @appendixsection Process list
41263 @cindex operating system information, process list
41265 When requesting the process list, the @var{annex} field in the
41266 @samp{qXfer} request should be @samp{processes}. The returned data is
41267 an XML document. The formal syntax of this document is defined in
41268 @file{gdb/features/osdata.dtd}.
41270 An example document is:
41273 <?xml version="1.0"?>
41274 <!DOCTYPE target SYSTEM "osdata.dtd">
41275 <osdata type="processes">
41277 <column name="pid">1</column>
41278 <column name="user">root</column>
41279 <column name="command">/sbin/init</column>
41280 <column name="cores">1,2,3</column>
41285 Each item should include a column whose name is @samp{pid}. The value
41286 of that column should identify the process on the target. The
41287 @samp{user} and @samp{command} columns are optional, and will be
41288 displayed by @value{GDBN}. The @samp{cores} column, if present,
41289 should contain a comma-separated list of cores that this process
41290 is running on. Target may provide additional columns,
41291 which @value{GDBN} currently ignores.
41293 @node Trace File Format
41294 @appendix Trace File Format
41295 @cindex trace file format
41297 The trace file comes in three parts: a header, a textual description
41298 section, and a trace frame section with binary data.
41300 The header has the form @code{\x7fTRACE0\n}. The first byte is
41301 @code{0x7f} so as to indicate that the file contains binary data,
41302 while the @code{0} is a version number that may have different values
41305 The description section consists of multiple lines of @sc{ascii} text
41306 separated by newline characters (@code{0xa}). The lines may include a
41307 variety of optional descriptive or context-setting information, such
41308 as tracepoint definitions or register set size. @value{GDBN} will
41309 ignore any line that it does not recognize. An empty line marks the end
41314 Specifies the size of a register block in bytes. This is equal to the
41315 size of a @code{g} packet payload in the remote protocol. @var{size}
41316 is an ascii decimal number. There should be only one such line in
41317 a single trace file.
41319 @item status @var{status}
41320 Trace status. @var{status} has the same format as a @code{qTStatus}
41321 remote packet reply. There should be only one such line in a single trace
41324 @item tp @var{payload}
41325 Tracepoint definition. The @var{payload} has the same format as
41326 @code{qTfP}/@code{qTsP} remote packet reply payload. A single tracepoint
41327 may take multiple lines of definition, corresponding to the multiple
41330 @item tsv @var{payload}
41331 Trace state variable definition. The @var{payload} has the same format as
41332 @code{qTfV}/@code{qTsV} remote packet reply payload. A single variable
41333 may take multiple lines of definition, corresponding to the multiple
41336 @item tdesc @var{payload}
41337 Target description in XML format. The @var{payload} is a single line of
41338 the XML file. All such lines should be concatenated together to get
41339 the original XML file. This file is in the same format as @code{qXfer}
41340 @code{features} payload, and corresponds to the main @code{target.xml}
41341 file. Includes are not allowed.
41345 The trace frame section consists of a number of consecutive frames.
41346 Each frame begins with a two-byte tracepoint number, followed by a
41347 four-byte size giving the amount of data in the frame. The data in
41348 the frame consists of a number of blocks, each introduced by a
41349 character indicating its type (at least register, memory, and trace
41350 state variable). The data in this section is raw binary, not a
41351 hexadecimal or other encoding; its endianness matches the target's
41354 @c FIXME bi-arch may require endianness/arch info in description section
41357 @item R @var{bytes}
41358 Register block. The number and ordering of bytes matches that of a
41359 @code{g} packet in the remote protocol. Note that these are the
41360 actual bytes, in target order, not a hexadecimal encoding.
41362 @item M @var{address} @var{length} @var{bytes}...
41363 Memory block. This is a contiguous block of memory, at the 8-byte
41364 address @var{address}, with a 2-byte length @var{length}, followed by
41365 @var{length} bytes.
41367 @item V @var{number} @var{value}
41368 Trace state variable block. This records the 8-byte signed value
41369 @var{value} of trace state variable numbered @var{number}.
41373 Future enhancements of the trace file format may include additional types
41376 @node Index Section Format
41377 @appendix @code{.gdb_index} section format
41378 @cindex .gdb_index section format
41379 @cindex index section format
41381 This section documents the index section that is created by @code{save
41382 gdb-index} (@pxref{Index Files}). The index section is
41383 DWARF-specific; some knowledge of DWARF is assumed in this
41386 The mapped index file format is designed to be directly
41387 @code{mmap}able on any architecture. In most cases, a datum is
41388 represented using a little-endian 32-bit integer value, called an
41389 @code{offset_type}. Big endian machines must byte-swap the values
41390 before using them. Exceptions to this rule are noted. The data is
41391 laid out such that alignment is always respected.
41393 A mapped index consists of several areas, laid out in order.
41397 The file header. This is a sequence of values, of @code{offset_type}
41398 unless otherwise noted:
41402 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
41403 Version 4 uses a different hashing function from versions 5 and 6.
41404 Version 6 includes symbols for inlined functions, whereas versions 4
41405 and 5 do not. Version 7 adds attributes to the CU indices in the
41406 symbol table. Version 8 specifies that symbols from DWARF type units
41407 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
41408 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
41410 @value{GDBN} will only read version 4, 5, or 6 indices
41411 by specifying @code{set use-deprecated-index-sections on}.
41412 GDB has a workaround for potentially broken version 7 indices so it is
41413 currently not flagged as deprecated.
41416 The offset, from the start of the file, of the CU list.
41419 The offset, from the start of the file, of the types CU list. Note
41420 that this area can be empty, in which case this offset will be equal
41421 to the next offset.
41424 The offset, from the start of the file, of the address area.
41427 The offset, from the start of the file, of the symbol table.
41430 The offset, from the start of the file, of the constant pool.
41434 The CU list. This is a sequence of pairs of 64-bit little-endian
41435 values, sorted by the CU offset. The first element in each pair is
41436 the offset of a CU in the @code{.debug_info} section. The second
41437 element in each pair is the length of that CU. References to a CU
41438 elsewhere in the map are done using a CU index, which is just the
41439 0-based index into this table. Note that if there are type CUs, then
41440 conceptually CUs and type CUs form a single list for the purposes of
41444 The types CU list. This is a sequence of triplets of 64-bit
41445 little-endian values. In a triplet, the first value is the CU offset,
41446 the second value is the type offset in the CU, and the third value is
41447 the type signature. The types CU list is not sorted.
41450 The address area. The address area consists of a sequence of address
41451 entries. Each address entry has three elements:
41455 The low address. This is a 64-bit little-endian value.
41458 The high address. This is a 64-bit little-endian value. Like
41459 @code{DW_AT_high_pc}, the value is one byte beyond the end.
41462 The CU index. This is an @code{offset_type} value.
41466 The symbol table. This is an open-addressed hash table. The size of
41467 the hash table is always a power of 2.
41469 Each slot in the hash table consists of a pair of @code{offset_type}
41470 values. The first value is the offset of the symbol's name in the
41471 constant pool. The second value is the offset of the CU vector in the
41474 If both values are 0, then this slot in the hash table is empty. This
41475 is ok because while 0 is a valid constant pool index, it cannot be a
41476 valid index for both a string and a CU vector.
41478 The hash value for a table entry is computed by applying an
41479 iterative hash function to the symbol's name. Starting with an
41480 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
41481 the string is incorporated into the hash using the formula depending on the
41486 The formula is @code{r = r * 67 + c - 113}.
41488 @item Versions 5 to 7
41489 The formula is @code{r = r * 67 + tolower (c) - 113}.
41492 The terminating @samp{\0} is not incorporated into the hash.
41494 The step size used in the hash table is computed via
41495 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
41496 value, and @samp{size} is the size of the hash table. The step size
41497 is used to find the next candidate slot when handling a hash
41500 The names of C@t{++} symbols in the hash table are canonicalized. We
41501 don't currently have a simple description of the canonicalization
41502 algorithm; if you intend to create new index sections, you must read
41506 The constant pool. This is simply a bunch of bytes. It is organized
41507 so that alignment is correct: CU vectors are stored first, followed by
41510 A CU vector in the constant pool is a sequence of @code{offset_type}
41511 values. The first value is the number of CU indices in the vector.
41512 Each subsequent value is the index and symbol attributes of a CU in
41513 the CU list. This element in the hash table is used to indicate which
41514 CUs define the symbol and how the symbol is used.
41515 See below for the format of each CU index+attributes entry.
41517 A string in the constant pool is zero-terminated.
41520 Attributes were added to CU index values in @code{.gdb_index} version 7.
41521 If a symbol has multiple uses within a CU then there is one
41522 CU index+attributes value for each use.
41524 The format of each CU index+attributes entry is as follows
41530 This is the index of the CU in the CU list.
41532 These bits are reserved for future purposes and must be zero.
41534 The kind of the symbol in the CU.
41538 This value is reserved and should not be used.
41539 By reserving zero the full @code{offset_type} value is backwards compatible
41540 with previous versions of the index.
41542 The symbol is a type.
41544 The symbol is a variable or an enum value.
41546 The symbol is a function.
41548 Any other kind of symbol.
41550 These values are reserved.
41554 This bit is zero if the value is global and one if it is static.
41556 The determination of whether a symbol is global or static is complicated.
41557 The authorative reference is the file @file{dwarf2read.c} in
41558 @value{GDBN} sources.
41562 This pseudo-code describes the computation of a symbol's kind and
41563 global/static attributes in the index.
41566 is_external = get_attribute (die, DW_AT_external);
41567 language = get_attribute (cu_die, DW_AT_language);
41570 case DW_TAG_typedef:
41571 case DW_TAG_base_type:
41572 case DW_TAG_subrange_type:
41576 case DW_TAG_enumerator:
41578 is_static = (language != CPLUS && language != JAVA);
41580 case DW_TAG_subprogram:
41582 is_static = ! (is_external || language == ADA);
41584 case DW_TAG_constant:
41586 is_static = ! is_external;
41588 case DW_TAG_variable:
41590 is_static = ! is_external;
41592 case DW_TAG_namespace:
41596 case DW_TAG_class_type:
41597 case DW_TAG_interface_type:
41598 case DW_TAG_structure_type:
41599 case DW_TAG_union_type:
41600 case DW_TAG_enumeration_type:
41602 is_static = (language != CPLUS && language != JAVA);
41610 @appendix Manual pages
41614 * gdb man:: The GNU Debugger man page
41615 * gdbserver man:: Remote Server for the GNU Debugger man page
41616 * gcore man:: Generate a core file of a running program
41617 * gdbinit man:: gdbinit scripts
41623 @c man title gdb The GNU Debugger
41625 @c man begin SYNOPSIS gdb
41626 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
41627 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
41628 [@option{-b}@w{ }@var{bps}]
41629 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
41630 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
41631 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
41632 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
41633 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
41636 @c man begin DESCRIPTION gdb
41637 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
41638 going on ``inside'' another program while it executes -- or what another
41639 program was doing at the moment it crashed.
41641 @value{GDBN} can do four main kinds of things (plus other things in support of
41642 these) to help you catch bugs in the act:
41646 Start your program, specifying anything that might affect its behavior.
41649 Make your program stop on specified conditions.
41652 Examine what has happened, when your program has stopped.
41655 Change things in your program, so you can experiment with correcting the
41656 effects of one bug and go on to learn about another.
41659 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
41662 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
41663 commands from the terminal until you tell it to exit with the @value{GDBN}
41664 command @code{quit}. You can get online help from @value{GDBN} itself
41665 by using the command @code{help}.
41667 You can run @code{gdb} with no arguments or options; but the most
41668 usual way to start @value{GDBN} is with one argument or two, specifying an
41669 executable program as the argument:
41675 You can also start with both an executable program and a core file specified:
41681 You can, instead, specify a process ID as a second argument, if you want
41682 to debug a running process:
41690 would attach @value{GDBN} to process @code{1234} (unless you also have a file
41691 named @file{1234}; @value{GDBN} does check for a core file first).
41692 With option @option{-p} you can omit the @var{program} filename.
41694 Here are some of the most frequently needed @value{GDBN} commands:
41696 @c pod2man highlights the right hand side of the @item lines.
41698 @item break [@var{file}:]@var{function}
41699 Set a breakpoint at @var{function} (in @var{file}).
41701 @item run [@var{arglist}]
41702 Start your program (with @var{arglist}, if specified).
41705 Backtrace: display the program stack.
41707 @item print @var{expr}
41708 Display the value of an expression.
41711 Continue running your program (after stopping, e.g. at a breakpoint).
41714 Execute next program line (after stopping); step @emph{over} any
41715 function calls in the line.
41717 @item edit [@var{file}:]@var{function}
41718 look at the program line where it is presently stopped.
41720 @item list [@var{file}:]@var{function}
41721 type the text of the program in the vicinity of where it is presently stopped.
41724 Execute next program line (after stopping); step @emph{into} any
41725 function calls in the line.
41727 @item help [@var{name}]
41728 Show information about @value{GDBN} command @var{name}, or general information
41729 about using @value{GDBN}.
41732 Exit from @value{GDBN}.
41736 For full details on @value{GDBN},
41737 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41738 by Richard M. Stallman and Roland H. Pesch. The same text is available online
41739 as the @code{gdb} entry in the @code{info} program.
41743 @c man begin OPTIONS gdb
41744 Any arguments other than options specify an executable
41745 file and core file (or process ID); that is, the first argument
41746 encountered with no
41747 associated option flag is equivalent to a @option{-se} option, and the second,
41748 if any, is equivalent to a @option{-c} option if it's the name of a file.
41750 both long and short forms; both are shown here. The long forms are also
41751 recognized if you truncate them, so long as enough of the option is
41752 present to be unambiguous. (If you prefer, you can flag option
41753 arguments with @option{+} rather than @option{-}, though we illustrate the
41754 more usual convention.)
41756 All the options and command line arguments you give are processed
41757 in sequential order. The order makes a difference when the @option{-x}
41763 List all options, with brief explanations.
41765 @item -symbols=@var{file}
41766 @itemx -s @var{file}
41767 Read symbol table from file @var{file}.
41770 Enable writing into executable and core files.
41772 @item -exec=@var{file}
41773 @itemx -e @var{file}
41774 Use file @var{file} as the executable file to execute when
41775 appropriate, and for examining pure data in conjunction with a core
41778 @item -se=@var{file}
41779 Read symbol table from file @var{file} and use it as the executable
41782 @item -core=@var{file}
41783 @itemx -c @var{file}
41784 Use file @var{file} as a core dump to examine.
41786 @item -command=@var{file}
41787 @itemx -x @var{file}
41788 Execute @value{GDBN} commands from file @var{file}.
41790 @item -ex @var{command}
41791 Execute given @value{GDBN} @var{command}.
41793 @item -directory=@var{directory}
41794 @itemx -d @var{directory}
41795 Add @var{directory} to the path to search for source files.
41798 Do not execute commands from @file{~/.gdbinit}.
41802 Do not execute commands from any @file{.gdbinit} initialization files.
41806 ``Quiet''. Do not print the introductory and copyright messages. These
41807 messages are also suppressed in batch mode.
41810 Run in batch mode. Exit with status @code{0} after processing all the command
41811 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
41812 Exit with nonzero status if an error occurs in executing the @value{GDBN}
41813 commands in the command files.
41815 Batch mode may be useful for running @value{GDBN} as a filter, for example to
41816 download and run a program on another computer; in order to make this
41817 more useful, the message
41820 Program exited normally.
41824 (which is ordinarily issued whenever a program running under @value{GDBN} control
41825 terminates) is not issued when running in batch mode.
41827 @item -cd=@var{directory}
41828 Run @value{GDBN} using @var{directory} as its working directory,
41829 instead of the current directory.
41833 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
41834 @value{GDBN} to output the full file name and line number in a standard,
41835 recognizable fashion each time a stack frame is displayed (which
41836 includes each time the program stops). This recognizable format looks
41837 like two @samp{\032} characters, followed by the file name, line number
41838 and character position separated by colons, and a newline. The
41839 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
41840 characters as a signal to display the source code for the frame.
41843 Set the line speed (baud rate or bits per second) of any serial
41844 interface used by @value{GDBN} for remote debugging.
41846 @item -tty=@var{device}
41847 Run using @var{device} for your program's standard input and output.
41851 @c man begin SEEALSO gdb
41853 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41854 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41855 documentation are properly installed at your site, the command
41862 should give you access to the complete manual.
41864 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41865 Richard M. Stallman and Roland H. Pesch, July 1991.
41869 @node gdbserver man
41870 @heading gdbserver man
41872 @c man title gdbserver Remote Server for the GNU Debugger
41874 @c man begin SYNOPSIS gdbserver
41875 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
41877 gdbserver --attach @var{comm} @var{pid}
41879 gdbserver --multi @var{comm}
41883 @c man begin DESCRIPTION gdbserver
41884 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
41885 than the one which is running the program being debugged.
41888 @subheading Usage (server (target) side)
41891 Usage (server (target) side):
41894 First, you need to have a copy of the program you want to debug put onto
41895 the target system. The program can be stripped to save space if needed, as
41896 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
41897 the @value{GDBN} running on the host system.
41899 To use the server, you log on to the target system, and run the @command{gdbserver}
41900 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
41901 your program, and (c) its arguments. The general syntax is:
41904 target> gdbserver @var{comm} @var{program} [@var{args} ...]
41907 For example, using a serial port, you might say:
41911 @c @file would wrap it as F</dev/com1>.
41912 target> gdbserver /dev/com1 emacs foo.txt
41915 target> gdbserver @file{/dev/com1} emacs foo.txt
41919 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
41920 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
41921 waits patiently for the host @value{GDBN} to communicate with it.
41923 To use a TCP connection, you could say:
41926 target> gdbserver host:2345 emacs foo.txt
41929 This says pretty much the same thing as the last example, except that we are
41930 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
41931 that we are expecting to see a TCP connection from @code{host} to local TCP port
41932 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
41933 want for the port number as long as it does not conflict with any existing TCP
41934 ports on the target system. This same port number must be used in the host
41935 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
41936 you chose a port number that conflicts with another service, @command{gdbserver} will
41937 print an error message and exit.
41939 @command{gdbserver} can also attach to running programs.
41940 This is accomplished via the @option{--attach} argument. The syntax is:
41943 target> gdbserver --attach @var{comm} @var{pid}
41946 @var{pid} is the process ID of a currently running process. It isn't
41947 necessary to point @command{gdbserver} at a binary for the running process.
41949 To start @code{gdbserver} without supplying an initial command to run
41950 or process ID to attach, use the @option{--multi} command line option.
41951 In such case you should connect using @kbd{target extended-remote} to start
41952 the program you want to debug.
41955 target> gdbserver --multi @var{comm}
41959 @subheading Usage (host side)
41965 You need an unstripped copy of the target program on your host system, since
41966 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
41967 would, with the target program as the first argument. (You may need to use the
41968 @option{--baud} option if the serial line is running at anything except 9600 baud.)
41969 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
41970 new command you need to know about is @code{target remote}
41971 (or @code{target extended-remote}). Its argument is either
41972 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
41973 descriptor. For example:
41977 @c @file would wrap it as F</dev/ttyb>.
41978 (gdb) target remote /dev/ttyb
41981 (gdb) target remote @file{/dev/ttyb}
41986 communicates with the server via serial line @file{/dev/ttyb}, and:
41989 (gdb) target remote the-target:2345
41993 communicates via a TCP connection to port 2345 on host `the-target', where
41994 you previously started up @command{gdbserver} with the same port number. Note that for
41995 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
41996 command, otherwise you may get an error that looks something like
41997 `Connection refused'.
41999 @command{gdbserver} can also debug multiple inferiors at once,
42002 the @value{GDBN} manual in node @code{Inferiors and Programs}
42003 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
42006 @ref{Inferiors and Programs}.
42008 In such case use the @code{extended-remote} @value{GDBN} command variant:
42011 (gdb) target extended-remote the-target:2345
42014 The @command{gdbserver} option @option{--multi} may or may not be used in such
42018 @c man begin OPTIONS gdbserver
42019 There are three different modes for invoking @command{gdbserver}:
42024 Debug a specific program specified by its program name:
42027 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
42030 The @var{comm} parameter specifies how should the server communicate
42031 with @value{GDBN}; it is either a device name (to use a serial line),
42032 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
42033 stdin/stdout of @code{gdbserver}. Specify the name of the program to
42034 debug in @var{prog}. Any remaining arguments will be passed to the
42035 program verbatim. When the program exits, @value{GDBN} will close the
42036 connection, and @code{gdbserver} will exit.
42039 Debug a specific program by specifying the process ID of a running
42043 gdbserver --attach @var{comm} @var{pid}
42046 The @var{comm} parameter is as described above. Supply the process ID
42047 of a running program in @var{pid}; @value{GDBN} will do everything
42048 else. Like with the previous mode, when the process @var{pid} exits,
42049 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
42052 Multi-process mode -- debug more than one program/process:
42055 gdbserver --multi @var{comm}
42058 In this mode, @value{GDBN} can instruct @command{gdbserver} which
42059 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
42060 close the connection when a process being debugged exits, so you can
42061 debug several processes in the same session.
42064 In each of the modes you may specify these options:
42069 List all options, with brief explanations.
42072 This option causes @command{gdbserver} to print its version number and exit.
42075 @command{gdbserver} will attach to a running program. The syntax is:
42078 target> gdbserver --attach @var{comm} @var{pid}
42081 @var{pid} is the process ID of a currently running process. It isn't
42082 necessary to point @command{gdbserver} at a binary for the running process.
42085 To start @code{gdbserver} without supplying an initial command to run
42086 or process ID to attach, use this command line option.
42087 Then you can connect using @kbd{target extended-remote} and start
42088 the program you want to debug. The syntax is:
42091 target> gdbserver --multi @var{comm}
42095 Instruct @code{gdbserver} to display extra status information about the debugging
42097 This option is intended for @code{gdbserver} development and for bug reports to
42100 @item --remote-debug
42101 Instruct @code{gdbserver} to display remote protocol debug output.
42102 This option is intended for @code{gdbserver} development and for bug reports to
42105 @item --debug-format=option1@r{[},option2,...@r{]}
42106 Instruct @code{gdbserver} to include extra information in each line
42107 of debugging output.
42108 @xref{Other Command-Line Arguments for gdbserver}.
42111 Specify a wrapper to launch programs
42112 for debugging. The option should be followed by the name of the
42113 wrapper, then any command-line arguments to pass to the wrapper, then
42114 @kbd{--} indicating the end of the wrapper arguments.
42117 By default, @command{gdbserver} keeps the listening TCP port open, so that
42118 additional connections are possible. However, if you start @code{gdbserver}
42119 with the @option{--once} option, it will stop listening for any further
42120 connection attempts after connecting to the first @value{GDBN} session.
42122 @c --disable-packet is not documented for users.
42124 @c --disable-randomization and --no-disable-randomization are superseded by
42125 @c QDisableRandomization.
42130 @c man begin SEEALSO gdbserver
42132 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42133 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42134 documentation are properly installed at your site, the command
42140 should give you access to the complete manual.
42142 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42143 Richard M. Stallman and Roland H. Pesch, July 1991.
42150 @c man title gcore Generate a core file of a running program
42153 @c man begin SYNOPSIS gcore
42154 gcore [-o @var{filename}] @var{pid}
42158 @c man begin DESCRIPTION gcore
42159 Generate a core dump of a running program with process ID @var{pid}.
42160 Produced file is equivalent to a kernel produced core file as if the process
42161 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
42162 limit). Unlike after a crash, after @command{gcore} the program remains
42163 running without any change.
42166 @c man begin OPTIONS gcore
42168 @item -o @var{filename}
42169 The optional argument
42170 @var{filename} specifies the file name where to put the core dump.
42171 If not specified, the file name defaults to @file{core.@var{pid}},
42172 where @var{pid} is the running program process ID.
42176 @c man begin SEEALSO gcore
42178 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42179 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42180 documentation are properly installed at your site, the command
42187 should give you access to the complete manual.
42189 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42190 Richard M. Stallman and Roland H. Pesch, July 1991.
42197 @c man title gdbinit GDB initialization scripts
42200 @c man begin SYNOPSIS gdbinit
42201 @ifset SYSTEM_GDBINIT
42202 @value{SYSTEM_GDBINIT}
42211 @c man begin DESCRIPTION gdbinit
42212 These files contain @value{GDBN} commands to automatically execute during
42213 @value{GDBN} startup. The lines of contents are canned sequences of commands,
42216 the @value{GDBN} manual in node @code{Sequences}
42217 -- shell command @code{info -f gdb -n Sequences}.
42223 Please read more in
42225 the @value{GDBN} manual in node @code{Startup}
42226 -- shell command @code{info -f gdb -n Startup}.
42233 @ifset SYSTEM_GDBINIT
42234 @item @value{SYSTEM_GDBINIT}
42236 @ifclear SYSTEM_GDBINIT
42237 @item (not enabled with @code{--with-system-gdbinit} during compilation)
42239 System-wide initialization file. It is executed unless user specified
42240 @value{GDBN} option @code{-nx} or @code{-n}.
42243 the @value{GDBN} manual in node @code{System-wide configuration}
42244 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
42247 @ref{System-wide configuration}.
42251 User initialization file. It is executed unless user specified
42252 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
42255 Initialization file for current directory. It may need to be enabled with
42256 @value{GDBN} security command @code{set auto-load local-gdbinit}.
42259 the @value{GDBN} manual in node @code{Init File in the Current Directory}
42260 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
42263 @ref{Init File in the Current Directory}.
42268 @c man begin SEEALSO gdbinit
42270 gdb(1), @code{info -f gdb -n Startup}
42272 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42273 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42274 documentation are properly installed at your site, the command
42280 should give you access to the complete manual.
42282 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42283 Richard M. Stallman and Roland H. Pesch, July 1991.
42289 @node GNU Free Documentation License
42290 @appendix GNU Free Documentation License
42293 @node Concept Index
42294 @unnumbered Concept Index
42298 @node Command and Variable Index
42299 @unnumbered Command, Variable, and Function Index
42304 % I think something like @@colophon should be in texinfo. In the
42306 \long\def\colophon{\hbox to0pt{}\vfill
42307 \centerline{The body of this manual is set in}
42308 \centerline{\fontname\tenrm,}
42309 \centerline{with headings in {\bf\fontname\tenbf}}
42310 \centerline{and examples in {\tt\fontname\tentt}.}
42311 \centerline{{\it\fontname\tenit\/},}
42312 \centerline{{\bf\fontname\tenbf}, and}
42313 \centerline{{\sl\fontname\tensl\/}}
42314 \centerline{are used for emphasis.}\vfill}
42316 % Blame: doc@@cygnus.com, 1991.