1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-2015 Free Software Foundation, Inc.
5 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
6 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
23 @c To avoid file-name clashes between index.html and Index.html, when
24 @c the manual is produced on a Posix host and then moved to a
25 @c case-insensitive filesystem (e.g., MS-Windows), we separate the
26 @c indices into two: Concept Index and all the rest.
30 @c readline appendices use @vindex, @findex and @ftable,
31 @c annotate.texi and gdbmi use @findex.
34 @c !!set GDB manual's edition---not the same as GDB version!
35 @c This is updated by GNU Press.
38 @c !!set GDB edit command default editor
41 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
43 @c This is a dir.info fragment to support semi-automated addition of
44 @c manuals to an info tree.
45 @dircategory Software development
47 * Gdb: (gdb). The GNU debugger.
48 * gdbserver: (gdb) Server. The GNU debugging server.
52 @c man begin COPYRIGHT
53 Copyright @copyright{} 1988-2015 Free Software Foundation, Inc.
55 Permission is granted to copy, distribute and/or modify this document
56 under the terms of the GNU Free Documentation License, Version 1.3 or
57 any later version published by the Free Software Foundation; with the
58 Invariant Sections being ``Free Software'' and ``Free Software Needs
59 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
60 and with the Back-Cover Texts as in (a) below.
62 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
63 this GNU Manual. Buying copies from GNU Press supports the FSF in
64 developing GNU and promoting software freedom.''
69 This file documents the @sc{gnu} debugger @value{GDBN}.
71 This is the @value{EDITION} Edition, of @cite{Debugging with
72 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
73 @ifset VERSION_PACKAGE
74 @value{VERSION_PACKAGE}
76 Version @value{GDBVN}.
82 @title Debugging with @value{GDBN}
83 @subtitle The @sc{gnu} Source-Level Debugger
85 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
86 @ifset VERSION_PACKAGE
88 @subtitle @value{VERSION_PACKAGE}
90 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
94 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
95 \hfill {\it Debugging with @value{GDBN}}\par
96 \hfill \TeX{}info \texinfoversion\par
100 @vskip 0pt plus 1filll
101 Published by the Free Software Foundation @*
102 51 Franklin Street, Fifth Floor,
103 Boston, MA 02110-1301, USA@*
104 ISBN 978-0-9831592-3-0 @*
111 @node Top, Summary, (dir), (dir)
113 @top Debugging with @value{GDBN}
115 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
117 This is the @value{EDITION} Edition, for @value{GDBN}
118 @ifset VERSION_PACKAGE
119 @value{VERSION_PACKAGE}
121 Version @value{GDBVN}.
123 Copyright (C) 1988-2015 Free Software Foundation, Inc.
125 This edition of the GDB manual is dedicated to the memory of Fred
126 Fish. Fred was a long-standing contributor to GDB and to Free
127 software in general. We will miss him.
130 * Summary:: Summary of @value{GDBN}
131 * Sample Session:: A sample @value{GDBN} session
133 * Invocation:: Getting in and out of @value{GDBN}
134 * Commands:: @value{GDBN} commands
135 * Running:: Running programs under @value{GDBN}
136 * Stopping:: Stopping and continuing
137 * Reverse Execution:: Running programs backward
138 * Process Record and Replay:: Recording inferior's execution and replaying it
139 * Stack:: Examining the stack
140 * Source:: Examining source files
141 * Data:: Examining data
142 * Optimized Code:: Debugging optimized code
143 * Macros:: Preprocessor Macros
144 * Tracepoints:: Debugging remote targets non-intrusively
145 * Overlays:: Debugging programs that use overlays
147 * Languages:: Using @value{GDBN} with different languages
149 * Symbols:: Examining the symbol table
150 * Altering:: Altering execution
151 * GDB Files:: @value{GDBN} files
152 * Targets:: Specifying a debugging target
153 * Remote Debugging:: Debugging remote programs
154 * Configurations:: Configuration-specific information
155 * Controlling GDB:: Controlling @value{GDBN}
156 * Extending GDB:: Extending @value{GDBN}
157 * Interpreters:: Command Interpreters
158 * TUI:: @value{GDBN} Text User Interface
159 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
160 * GDB/MI:: @value{GDBN}'s Machine Interface.
161 * Annotations:: @value{GDBN}'s annotation interface.
162 * JIT Interface:: Using the JIT debugging interface.
163 * In-Process Agent:: In-Process Agent
165 * GDB Bugs:: Reporting bugs in @value{GDBN}
167 @ifset SYSTEM_READLINE
168 * Command Line Editing: (rluserman). Command Line Editing
169 * Using History Interactively: (history). Using History Interactively
171 @ifclear SYSTEM_READLINE
172 * Command Line Editing:: Command Line Editing
173 * Using History Interactively:: Using History Interactively
175 * In Memoriam:: In Memoriam
176 * Formatting Documentation:: How to format and print @value{GDBN} documentation
177 * Installing GDB:: Installing GDB
178 * Maintenance Commands:: Maintenance Commands
179 * Remote Protocol:: GDB Remote Serial Protocol
180 * Agent Expressions:: The GDB Agent Expression Mechanism
181 * Target Descriptions:: How targets can describe themselves to
183 * Operating System Information:: Getting additional information from
185 * Trace File Format:: GDB trace file format
186 * Index Section Format:: .gdb_index section format
187 * Man Pages:: Manual pages
188 * Copying:: GNU General Public License says
189 how you can copy and share GDB
190 * GNU Free Documentation License:: The license for this documentation
191 * Concept Index:: Index of @value{GDBN} concepts
192 * Command and Variable Index:: Index of @value{GDBN} commands, variables,
193 functions, and Python data types
201 @unnumbered Summary of @value{GDBN}
203 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
204 going on ``inside'' another program while it executes---or what another
205 program was doing at the moment it crashed.
207 @value{GDBN} can do four main kinds of things (plus other things in support of
208 these) to help you catch bugs in the act:
212 Start your program, specifying anything that might affect its behavior.
215 Make your program stop on specified conditions.
218 Examine what has happened, when your program has stopped.
221 Change things in your program, so you can experiment with correcting the
222 effects of one bug and go on to learn about another.
225 You can use @value{GDBN} to debug programs written in C and C@t{++}.
226 For more information, see @ref{Supported Languages,,Supported Languages}.
227 For more information, see @ref{C,,C and C++}.
229 Support for D is partial. For information on D, see
233 Support for Modula-2 is partial. For information on Modula-2, see
234 @ref{Modula-2,,Modula-2}.
236 Support for OpenCL C is partial. For information on OpenCL C, see
237 @ref{OpenCL C,,OpenCL C}.
240 Debugging Pascal programs which use sets, subranges, file variables, or
241 nested functions does not currently work. @value{GDBN} does not support
242 entering expressions, printing values, or similar features using Pascal
246 @value{GDBN} can be used to debug programs written in Fortran, although
247 it may be necessary to refer to some variables with a trailing
250 @value{GDBN} can be used to debug programs written in Objective-C,
251 using either the Apple/NeXT or the GNU Objective-C runtime.
254 * Free Software:: Freely redistributable software
255 * Free Documentation:: Free Software Needs Free Documentation
256 * Contributors:: Contributors to GDB
260 @unnumberedsec Free Software
262 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
263 General Public License
264 (GPL). The GPL gives you the freedom to copy or adapt a licensed
265 program---but every person getting a copy also gets with it the
266 freedom to modify that copy (which means that they must get access to
267 the source code), and the freedom to distribute further copies.
268 Typical software companies use copyrights to limit your freedoms; the
269 Free Software Foundation uses the GPL to preserve these freedoms.
271 Fundamentally, the General Public License is a license which says that
272 you have these freedoms and that you cannot take these freedoms away
275 @node Free Documentation
276 @unnumberedsec Free Software Needs Free Documentation
278 The biggest deficiency in the free software community today is not in
279 the software---it is the lack of good free documentation that we can
280 include with the free software. Many of our most important
281 programs do not come with free reference manuals and free introductory
282 texts. Documentation is an essential part of any software package;
283 when an important free software package does not come with a free
284 manual and a free tutorial, that is a major gap. We have many such
287 Consider Perl, for instance. The tutorial manuals that people
288 normally use are non-free. How did this come about? Because the
289 authors of those manuals published them with restrictive terms---no
290 copying, no modification, source files not available---which exclude
291 them from the free software world.
293 That wasn't the first time this sort of thing happened, and it was far
294 from the last. Many times we have heard a GNU user eagerly describe a
295 manual that he is writing, his intended contribution to the community,
296 only to learn that he had ruined everything by signing a publication
297 contract to make it non-free.
299 Free documentation, like free software, is a matter of freedom, not
300 price. The problem with the non-free manual is not that publishers
301 charge a price for printed copies---that in itself is fine. (The Free
302 Software Foundation sells printed copies of manuals, too.) The
303 problem is the restrictions on the use of the manual. Free manuals
304 are available in source code form, and give you permission to copy and
305 modify. Non-free manuals do not allow this.
307 The criteria of freedom for a free manual are roughly the same as for
308 free software. Redistribution (including the normal kinds of
309 commercial redistribution) must be permitted, so that the manual can
310 accompany every copy of the program, both on-line and on paper.
312 Permission for modification of the technical content is crucial too.
313 When people modify the software, adding or changing features, if they
314 are conscientious they will change the manual too---so they can
315 provide accurate and clear documentation for the modified program. A
316 manual that leaves you no choice but to write a new manual to document
317 a changed version of the program is not really available to our
320 Some kinds of limits on the way modification is handled are
321 acceptable. For example, requirements to preserve the original
322 author's copyright notice, the distribution terms, or the list of
323 authors, are ok. It is also no problem to require modified versions
324 to include notice that they were modified. Even entire sections that
325 may not be deleted or changed are acceptable, as long as they deal
326 with nontechnical topics (like this one). These kinds of restrictions
327 are acceptable because they don't obstruct the community's normal use
330 However, it must be possible to modify all the @emph{technical}
331 content of the manual, and then distribute the result in all the usual
332 media, through all the usual channels. Otherwise, the restrictions
333 obstruct the use of the manual, it is not free, and we need another
334 manual to replace it.
336 Please spread the word about this issue. Our community continues to
337 lose manuals to proprietary publishing. If we spread the word that
338 free software needs free reference manuals and free tutorials, perhaps
339 the next person who wants to contribute by writing documentation will
340 realize, before it is too late, that only free manuals contribute to
341 the free software community.
343 If you are writing documentation, please insist on publishing it under
344 the GNU Free Documentation License or another free documentation
345 license. Remember that this decision requires your approval---you
346 don't have to let the publisher decide. Some commercial publishers
347 will use a free license if you insist, but they will not propose the
348 option; it is up to you to raise the issue and say firmly that this is
349 what you want. If the publisher you are dealing with refuses, please
350 try other publishers. If you're not sure whether a proposed license
351 is free, write to @email{licensing@@gnu.org}.
353 You can encourage commercial publishers to sell more free, copylefted
354 manuals and tutorials by buying them, and particularly by buying
355 copies from the publishers that paid for their writing or for major
356 improvements. Meanwhile, try to avoid buying non-free documentation
357 at all. Check the distribution terms of a manual before you buy it,
358 and insist that whoever seeks your business must respect your freedom.
359 Check the history of the book, and try to reward the publishers that
360 have paid or pay the authors to work on it.
362 The Free Software Foundation maintains a list of free documentation
363 published by other publishers, at
364 @url{http://www.fsf.org/doc/other-free-books.html}.
367 @unnumberedsec Contributors to @value{GDBN}
369 Richard Stallman was the original author of @value{GDBN}, and of many
370 other @sc{gnu} programs. Many others have contributed to its
371 development. This section attempts to credit major contributors. One
372 of the virtues of free software is that everyone is free to contribute
373 to it; with regret, we cannot actually acknowledge everyone here. The
374 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
375 blow-by-blow account.
377 Changes much prior to version 2.0 are lost in the mists of time.
380 @emph{Plea:} Additions to this section are particularly welcome. If you
381 or your friends (or enemies, to be evenhanded) have been unfairly
382 omitted from this list, we would like to add your names!
385 So that they may not regard their many labors as thankless, we
386 particularly thank those who shepherded @value{GDBN} through major
388 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
389 Jim Blandy (release 4.18);
390 Jason Molenda (release 4.17);
391 Stan Shebs (release 4.14);
392 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
393 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
394 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
395 Jim Kingdon (releases 3.5, 3.4, and 3.3);
396 and Randy Smith (releases 3.2, 3.1, and 3.0).
398 Richard Stallman, assisted at various times by Peter TerMaat, Chris
399 Hanson, and Richard Mlynarik, handled releases through 2.8.
401 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
402 in @value{GDBN}, with significant additional contributions from Per
403 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
404 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
405 much general update work leading to release 3.0).
407 @value{GDBN} uses the BFD subroutine library to examine multiple
408 object-file formats; BFD was a joint project of David V.
409 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
411 David Johnson wrote the original COFF support; Pace Willison did
412 the original support for encapsulated COFF.
414 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
416 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
417 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
419 Jean-Daniel Fekete contributed Sun 386i support.
420 Chris Hanson improved the HP9000 support.
421 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
422 David Johnson contributed Encore Umax support.
423 Jyrki Kuoppala contributed Altos 3068 support.
424 Jeff Law contributed HP PA and SOM support.
425 Keith Packard contributed NS32K support.
426 Doug Rabson contributed Acorn Risc Machine support.
427 Bob Rusk contributed Harris Nighthawk CX-UX support.
428 Chris Smith contributed Convex support (and Fortran debugging).
429 Jonathan Stone contributed Pyramid support.
430 Michael Tiemann contributed SPARC support.
431 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
432 Pace Willison contributed Intel 386 support.
433 Jay Vosburgh contributed Symmetry support.
434 Marko Mlinar contributed OpenRISC 1000 support.
436 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
438 Rich Schaefer and Peter Schauer helped with support of SunOS shared
441 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
442 about several machine instruction sets.
444 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
445 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
446 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
447 and RDI targets, respectively.
449 Brian Fox is the author of the readline libraries providing
450 command-line editing and command history.
452 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
453 Modula-2 support, and contributed the Languages chapter of this manual.
455 Fred Fish wrote most of the support for Unix System Vr4.
456 He also enhanced the command-completion support to cover C@t{++} overloaded
459 Hitachi America (now Renesas America), Ltd. sponsored the support for
460 H8/300, H8/500, and Super-H processors.
462 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
464 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
467 Toshiba sponsored the support for the TX39 Mips processor.
469 Matsushita sponsored the support for the MN10200 and MN10300 processors.
471 Fujitsu sponsored the support for SPARClite and FR30 processors.
473 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
476 Michael Snyder added support for tracepoints.
478 Stu Grossman wrote gdbserver.
480 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
481 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
483 The following people at the Hewlett-Packard Company contributed
484 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
485 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
486 compiler, and the Text User Interface (nee Terminal User Interface):
487 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
488 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
489 provided HP-specific information in this manual.
491 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
492 Robert Hoehne made significant contributions to the DJGPP port.
494 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
495 development since 1991. Cygnus engineers who have worked on @value{GDBN}
496 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
497 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
498 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
499 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
500 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
501 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
502 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
503 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
504 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
505 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
506 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
507 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
508 Zuhn have made contributions both large and small.
510 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
511 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
513 Jim Blandy added support for preprocessor macros, while working for Red
516 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
517 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
518 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
519 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
520 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
521 with the migration of old architectures to this new framework.
523 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
524 unwinder framework, this consisting of a fresh new design featuring
525 frame IDs, independent frame sniffers, and the sentinel frame. Mark
526 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
527 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
528 trad unwinders. The architecture-specific changes, each involving a
529 complete rewrite of the architecture's frame code, were carried out by
530 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
531 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
532 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
533 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
536 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
537 Tensilica, Inc.@: contributed support for Xtensa processors. Others
538 who have worked on the Xtensa port of @value{GDBN} in the past include
539 Steve Tjiang, John Newlin, and Scott Foehner.
541 Michael Eager and staff of Xilinx, Inc., contributed support for the
542 Xilinx MicroBlaze architecture.
545 @chapter A Sample @value{GDBN} Session
547 You can use this manual at your leisure to read all about @value{GDBN}.
548 However, a handful of commands are enough to get started using the
549 debugger. This chapter illustrates those commands.
552 In this sample session, we emphasize user input like this: @b{input},
553 to make it easier to pick out from the surrounding output.
556 @c FIXME: this example may not be appropriate for some configs, where
557 @c FIXME...primary interest is in remote use.
559 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
560 processor) exhibits the following bug: sometimes, when we change its
561 quote strings from the default, the commands used to capture one macro
562 definition within another stop working. In the following short @code{m4}
563 session, we define a macro @code{foo} which expands to @code{0000}; we
564 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
565 same thing. However, when we change the open quote string to
566 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
567 procedure fails to define a new synonym @code{baz}:
576 @b{define(bar,defn(`foo'))}
580 @b{changequote(<QUOTE>,<UNQUOTE>)}
582 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
585 m4: End of input: 0: fatal error: EOF in string
589 Let us use @value{GDBN} to try to see what is going on.
592 $ @b{@value{GDBP} m4}
593 @c FIXME: this falsifies the exact text played out, to permit smallbook
594 @c FIXME... format to come out better.
595 @value{GDBN} is free software and you are welcome to distribute copies
596 of it under certain conditions; type "show copying" to see
598 There is absolutely no warranty for @value{GDBN}; type "show warranty"
601 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
606 @value{GDBN} reads only enough symbol data to know where to find the
607 rest when needed; as a result, the first prompt comes up very quickly.
608 We now tell @value{GDBN} to use a narrower display width than usual, so
609 that examples fit in this manual.
612 (@value{GDBP}) @b{set width 70}
616 We need to see how the @code{m4} built-in @code{changequote} works.
617 Having looked at the source, we know the relevant subroutine is
618 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
619 @code{break} command.
622 (@value{GDBP}) @b{break m4_changequote}
623 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
627 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
628 control; as long as control does not reach the @code{m4_changequote}
629 subroutine, the program runs as usual:
632 (@value{GDBP}) @b{run}
633 Starting program: /work/Editorial/gdb/gnu/m4/m4
641 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
642 suspends execution of @code{m4}, displaying information about the
643 context where it stops.
646 @b{changequote(<QUOTE>,<UNQUOTE>)}
648 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
650 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
654 Now we use the command @code{n} (@code{next}) to advance execution to
655 the next line of the current function.
659 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
664 @code{set_quotes} looks like a promising subroutine. We can go into it
665 by using the command @code{s} (@code{step}) instead of @code{next}.
666 @code{step} goes to the next line to be executed in @emph{any}
667 subroutine, so it steps into @code{set_quotes}.
671 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
673 530 if (lquote != def_lquote)
677 The display that shows the subroutine where @code{m4} is now
678 suspended (and its arguments) is called a stack frame display. It
679 shows a summary of the stack. We can use the @code{backtrace}
680 command (which can also be spelled @code{bt}), to see where we are
681 in the stack as a whole: the @code{backtrace} command displays a
682 stack frame for each active subroutine.
685 (@value{GDBP}) @b{bt}
686 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
688 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
690 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
691 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
693 #4 0x79dc in expand_input () at macro.c:40
694 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
698 We step through a few more lines to see what happens. The first two
699 times, we can use @samp{s}; the next two times we use @code{n} to avoid
700 falling into the @code{xstrdup} subroutine.
704 0x3b5c 532 if (rquote != def_rquote)
706 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
707 def_lquote : xstrdup(lq);
709 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
712 538 len_lquote = strlen(rquote);
716 The last line displayed looks a little odd; we can examine the variables
717 @code{lquote} and @code{rquote} to see if they are in fact the new left
718 and right quotes we specified. We use the command @code{p}
719 (@code{print}) to see their values.
722 (@value{GDBP}) @b{p lquote}
723 $1 = 0x35d40 "<QUOTE>"
724 (@value{GDBP}) @b{p rquote}
725 $2 = 0x35d50 "<UNQUOTE>"
729 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
730 To look at some context, we can display ten lines of source
731 surrounding the current line with the @code{l} (@code{list}) command.
737 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
739 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
742 538 len_lquote = strlen(rquote);
743 539 len_rquote = strlen(lquote);
750 Let us step past the two lines that set @code{len_lquote} and
751 @code{len_rquote}, and then examine the values of those variables.
755 539 len_rquote = strlen(lquote);
758 (@value{GDBP}) @b{p len_lquote}
760 (@value{GDBP}) @b{p len_rquote}
765 That certainly looks wrong, assuming @code{len_lquote} and
766 @code{len_rquote} are meant to be the lengths of @code{lquote} and
767 @code{rquote} respectively. We can set them to better values using
768 the @code{p} command, since it can print the value of
769 any expression---and that expression can include subroutine calls and
773 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
775 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
780 Is that enough to fix the problem of using the new quotes with the
781 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
782 executing with the @code{c} (@code{continue}) command, and then try the
783 example that caused trouble initially:
789 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
796 Success! The new quotes now work just as well as the default ones. The
797 problem seems to have been just the two typos defining the wrong
798 lengths. We allow @code{m4} exit by giving it an EOF as input:
802 Program exited normally.
806 The message @samp{Program exited normally.} is from @value{GDBN}; it
807 indicates @code{m4} has finished executing. We can end our @value{GDBN}
808 session with the @value{GDBN} @code{quit} command.
811 (@value{GDBP}) @b{quit}
815 @chapter Getting In and Out of @value{GDBN}
817 This chapter discusses how to start @value{GDBN}, and how to get out of it.
821 type @samp{@value{GDBP}} to start @value{GDBN}.
823 type @kbd{quit} or @kbd{Ctrl-d} to exit.
827 * Invoking GDB:: How to start @value{GDBN}
828 * Quitting GDB:: How to quit @value{GDBN}
829 * Shell Commands:: How to use shell commands inside @value{GDBN}
830 * Logging Output:: How to log @value{GDBN}'s output to a file
834 @section Invoking @value{GDBN}
836 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
837 @value{GDBN} reads commands from the terminal until you tell it to exit.
839 You can also run @code{@value{GDBP}} with a variety of arguments and options,
840 to specify more of your debugging environment at the outset.
842 The command-line options described here are designed
843 to cover a variety of situations; in some environments, some of these
844 options may effectively be unavailable.
846 The most usual way to start @value{GDBN} is with one argument,
847 specifying an executable program:
850 @value{GDBP} @var{program}
854 You can also start with both an executable program and a core file
858 @value{GDBP} @var{program} @var{core}
861 You can, instead, specify a process ID as a second argument, if you want
862 to debug a running process:
865 @value{GDBP} @var{program} 1234
869 would attach @value{GDBN} to process @code{1234} (unless you also have a file
870 named @file{1234}; @value{GDBN} does check for a core file first).
872 Taking advantage of the second command-line argument requires a fairly
873 complete operating system; when you use @value{GDBN} as a remote
874 debugger attached to a bare board, there may not be any notion of
875 ``process'', and there is often no way to get a core dump. @value{GDBN}
876 will warn you if it is unable to attach or to read core dumps.
878 You can optionally have @code{@value{GDBP}} pass any arguments after the
879 executable file to the inferior using @code{--args}. This option stops
882 @value{GDBP} --args gcc -O2 -c foo.c
884 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
885 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
887 You can run @code{@value{GDBP}} without printing the front material, which describes
888 @value{GDBN}'s non-warranty, by specifying @code{--silent}
889 (or @code{-q}/@code{--quiet}):
892 @value{GDBP} --silent
896 You can further control how @value{GDBN} starts up by using command-line
897 options. @value{GDBN} itself can remind you of the options available.
907 to display all available options and briefly describe their use
908 (@samp{@value{GDBP} -h} is a shorter equivalent).
910 All options and command line arguments you give are processed
911 in sequential order. The order makes a difference when the
912 @samp{-x} option is used.
916 * File Options:: Choosing files
917 * Mode Options:: Choosing modes
918 * Startup:: What @value{GDBN} does during startup
922 @subsection Choosing Files
924 When @value{GDBN} starts, it reads any arguments other than options as
925 specifying an executable file and core file (or process ID). This is
926 the same as if the arguments were specified by the @samp{-se} and
927 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
928 first argument that does not have an associated option flag as
929 equivalent to the @samp{-se} option followed by that argument; and the
930 second argument that does not have an associated option flag, if any, as
931 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
932 If the second argument begins with a decimal digit, @value{GDBN} will
933 first attempt to attach to it as a process, and if that fails, attempt
934 to open it as a corefile. If you have a corefile whose name begins with
935 a digit, you can prevent @value{GDBN} from treating it as a pid by
936 prefixing it with @file{./}, e.g.@: @file{./12345}.
938 If @value{GDBN} has not been configured to included core file support,
939 such as for most embedded targets, then it will complain about a second
940 argument and ignore it.
942 Many options have both long and short forms; both are shown in the
943 following list. @value{GDBN} also recognizes the long forms if you truncate
944 them, so long as enough of the option is present to be unambiguous.
945 (If you prefer, you can flag option arguments with @samp{--} rather
946 than @samp{-}, though we illustrate the more usual convention.)
948 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
949 @c way, both those who look for -foo and --foo in the index, will find
953 @item -symbols @var{file}
955 @cindex @code{--symbols}
957 Read symbol table from file @var{file}.
959 @item -exec @var{file}
961 @cindex @code{--exec}
963 Use file @var{file} as the executable file to execute when appropriate,
964 and for examining pure data in conjunction with a core dump.
968 Read symbol table from file @var{file} and use it as the executable
971 @item -core @var{file}
973 @cindex @code{--core}
975 Use file @var{file} as a core dump to examine.
977 @item -pid @var{number}
978 @itemx -p @var{number}
981 Connect to process ID @var{number}, as with the @code{attach} command.
983 @item -command @var{file}
985 @cindex @code{--command}
987 Execute commands from file @var{file}. The contents of this file is
988 evaluated exactly as the @code{source} command would.
989 @xref{Command Files,, Command files}.
991 @item -eval-command @var{command}
992 @itemx -ex @var{command}
993 @cindex @code{--eval-command}
995 Execute a single @value{GDBN} command.
997 This option may be used multiple times to call multiple commands. It may
998 also be interleaved with @samp{-command} as required.
1001 @value{GDBP} -ex 'target sim' -ex 'load' \
1002 -x setbreakpoints -ex 'run' a.out
1005 @item -init-command @var{file}
1006 @itemx -ix @var{file}
1007 @cindex @code{--init-command}
1009 Execute commands from file @var{file} before loading the inferior (but
1010 after loading gdbinit files).
1013 @item -init-eval-command @var{command}
1014 @itemx -iex @var{command}
1015 @cindex @code{--init-eval-command}
1017 Execute a single @value{GDBN} command before loading the inferior (but
1018 after loading gdbinit files).
1021 @item -directory @var{directory}
1022 @itemx -d @var{directory}
1023 @cindex @code{--directory}
1025 Add @var{directory} to the path to search for source and script files.
1029 @cindex @code{--readnow}
1031 Read each symbol file's entire symbol table immediately, rather than
1032 the default, which is to read it incrementally as it is needed.
1033 This makes startup slower, but makes future operations faster.
1038 @subsection Choosing Modes
1040 You can run @value{GDBN} in various alternative modes---for example, in
1041 batch mode or quiet mode.
1049 Do not execute commands found in any initialization file.
1050 There are three init files, loaded in the following order:
1053 @item @file{system.gdbinit}
1054 This is the system-wide init file.
1055 Its location is specified with the @code{--with-system-gdbinit}
1056 configure option (@pxref{System-wide configuration}).
1057 It is loaded first when @value{GDBN} starts, before command line options
1058 have been processed.
1059 @item @file{~/.gdbinit}
1060 This is the init file in your home directory.
1061 It is loaded next, after @file{system.gdbinit}, and before
1062 command options have been processed.
1063 @item @file{./.gdbinit}
1064 This is the init file in the current directory.
1065 It is loaded last, after command line options other than @code{-x} and
1066 @code{-ex} have been processed. Command line options @code{-x} and
1067 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1070 For further documentation on startup processing, @xref{Startup}.
1071 For documentation on how to write command files,
1072 @xref{Command Files,,Command Files}.
1077 Do not execute commands found in @file{~/.gdbinit}, the init file
1078 in your home directory.
1084 @cindex @code{--quiet}
1085 @cindex @code{--silent}
1087 ``Quiet''. Do not print the introductory and copyright messages. These
1088 messages are also suppressed in batch mode.
1091 @cindex @code{--batch}
1092 Run in batch mode. Exit with status @code{0} after processing all the
1093 command files specified with @samp{-x} (and all commands from
1094 initialization files, if not inhibited with @samp{-n}). Exit with
1095 nonzero status if an error occurs in executing the @value{GDBN} commands
1096 in the command files. Batch mode also disables pagination, sets unlimited
1097 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1098 off} were in effect (@pxref{Messages/Warnings}).
1100 Batch mode may be useful for running @value{GDBN} as a filter, for
1101 example to download and run a program on another computer; in order to
1102 make this more useful, the message
1105 Program exited normally.
1109 (which is ordinarily issued whenever a program running under
1110 @value{GDBN} control terminates) is not issued when running in batch
1114 @cindex @code{--batch-silent}
1115 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1116 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1117 unaffected). This is much quieter than @samp{-silent} and would be useless
1118 for an interactive session.
1120 This is particularly useful when using targets that give @samp{Loading section}
1121 messages, for example.
1123 Note that targets that give their output via @value{GDBN}, as opposed to
1124 writing directly to @code{stdout}, will also be made silent.
1126 @item -return-child-result
1127 @cindex @code{--return-child-result}
1128 The return code from @value{GDBN} will be the return code from the child
1129 process (the process being debugged), with the following exceptions:
1133 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1134 internal error. In this case the exit code is the same as it would have been
1135 without @samp{-return-child-result}.
1137 The user quits with an explicit value. E.g., @samp{quit 1}.
1139 The child process never runs, or is not allowed to terminate, in which case
1140 the exit code will be -1.
1143 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1144 when @value{GDBN} is being used as a remote program loader or simulator
1149 @cindex @code{--nowindows}
1151 ``No windows''. If @value{GDBN} comes with a graphical user interface
1152 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1153 interface. If no GUI is available, this option has no effect.
1157 @cindex @code{--windows}
1159 If @value{GDBN} includes a GUI, then this option requires it to be
1162 @item -cd @var{directory}
1164 Run @value{GDBN} using @var{directory} as its working directory,
1165 instead of the current directory.
1167 @item -data-directory @var{directory}
1168 @itemx -D @var{directory}
1169 @cindex @code{--data-directory}
1171 Run @value{GDBN} using @var{directory} as its data directory.
1172 The data directory is where @value{GDBN} searches for its
1173 auxiliary files. @xref{Data Files}.
1177 @cindex @code{--fullname}
1179 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1180 subprocess. It tells @value{GDBN} to output the full file name and line
1181 number in a standard, recognizable fashion each time a stack frame is
1182 displayed (which includes each time your program stops). This
1183 recognizable format looks like two @samp{\032} characters, followed by
1184 the file name, line number and character position separated by colons,
1185 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1186 @samp{\032} characters as a signal to display the source code for the
1189 @item -annotate @var{level}
1190 @cindex @code{--annotate}
1191 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1192 effect is identical to using @samp{set annotate @var{level}}
1193 (@pxref{Annotations}). The annotation @var{level} controls how much
1194 information @value{GDBN} prints together with its prompt, values of
1195 expressions, source lines, and other types of output. Level 0 is the
1196 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1197 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1198 that control @value{GDBN}, and level 2 has been deprecated.
1200 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1204 @cindex @code{--args}
1205 Change interpretation of command line so that arguments following the
1206 executable file are passed as command line arguments to the inferior.
1207 This option stops option processing.
1209 @item -baud @var{bps}
1211 @cindex @code{--baud}
1213 Set the line speed (baud rate or bits per second) of any serial
1214 interface used by @value{GDBN} for remote debugging.
1216 @item -l @var{timeout}
1218 Set the timeout (in seconds) of any communication used by @value{GDBN}
1219 for remote debugging.
1221 @item -tty @var{device}
1222 @itemx -t @var{device}
1223 @cindex @code{--tty}
1225 Run using @var{device} for your program's standard input and output.
1226 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1228 @c resolve the situation of these eventually
1230 @cindex @code{--tui}
1231 Activate the @dfn{Text User Interface} when starting. The Text User
1232 Interface manages several text windows on the terminal, showing
1233 source, assembly, registers and @value{GDBN} command outputs
1234 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1235 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1236 Using @value{GDBN} under @sc{gnu} Emacs}).
1238 @item -interpreter @var{interp}
1239 @cindex @code{--interpreter}
1240 Use the interpreter @var{interp} for interface with the controlling
1241 program or device. This option is meant to be set by programs which
1242 communicate with @value{GDBN} using it as a back end.
1243 @xref{Interpreters, , Command Interpreters}.
1245 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1246 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1247 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1248 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1249 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1250 @sc{gdb/mi} interfaces are no longer supported.
1253 @cindex @code{--write}
1254 Open the executable and core files for both reading and writing. This
1255 is equivalent to the @samp{set write on} command inside @value{GDBN}
1259 @cindex @code{--statistics}
1260 This option causes @value{GDBN} to print statistics about time and
1261 memory usage after it completes each command and returns to the prompt.
1264 @cindex @code{--version}
1265 This option causes @value{GDBN} to print its version number and
1266 no-warranty blurb, and exit.
1268 @item -configuration
1269 @cindex @code{--configuration}
1270 This option causes @value{GDBN} to print details about its build-time
1271 configuration parameters, and then exit. These details can be
1272 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1277 @subsection What @value{GDBN} Does During Startup
1278 @cindex @value{GDBN} startup
1280 Here's the description of what @value{GDBN} does during session startup:
1284 Sets up the command interpreter as specified by the command line
1285 (@pxref{Mode Options, interpreter}).
1289 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1290 used when building @value{GDBN}; @pxref{System-wide configuration,
1291 ,System-wide configuration and settings}) and executes all the commands in
1294 @anchor{Home Directory Init File}
1296 Reads the init file (if any) in your home directory@footnote{On
1297 DOS/Windows systems, the home directory is the one pointed to by the
1298 @code{HOME} environment variable.} and executes all the commands in
1301 @anchor{Option -init-eval-command}
1303 Executes commands and command files specified by the @samp{-iex} and
1304 @samp{-ix} options in their specified order. Usually you should use the
1305 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1306 settings before @value{GDBN} init files get executed and before inferior
1310 Processes command line options and operands.
1312 @anchor{Init File in the Current Directory during Startup}
1314 Reads and executes the commands from init file (if any) in the current
1315 working directory as long as @samp{set auto-load local-gdbinit} is set to
1316 @samp{on} (@pxref{Init File in the Current Directory}).
1317 This is only done if the current directory is
1318 different from your home directory. Thus, you can have more than one
1319 init file, one generic in your home directory, and another, specific
1320 to the program you are debugging, in the directory where you invoke
1324 If the command line specified a program to debug, or a process to
1325 attach to, or a core file, @value{GDBN} loads any auto-loaded
1326 scripts provided for the program or for its loaded shared libraries.
1327 @xref{Auto-loading}.
1329 If you wish to disable the auto-loading during startup,
1330 you must do something like the following:
1333 $ gdb -iex "set auto-load python-scripts off" myprogram
1336 Option @samp{-ex} does not work because the auto-loading is then turned
1340 Executes commands and command files specified by the @samp{-ex} and
1341 @samp{-x} options in their specified order. @xref{Command Files}, for
1342 more details about @value{GDBN} command files.
1345 Reads the command history recorded in the @dfn{history file}.
1346 @xref{Command History}, for more details about the command history and the
1347 files where @value{GDBN} records it.
1350 Init files use the same syntax as @dfn{command files} (@pxref{Command
1351 Files}) and are processed by @value{GDBN} in the same way. The init
1352 file in your home directory can set options (such as @samp{set
1353 complaints}) that affect subsequent processing of command line options
1354 and operands. Init files are not executed if you use the @samp{-nx}
1355 option (@pxref{Mode Options, ,Choosing Modes}).
1357 To display the list of init files loaded by gdb at startup, you
1358 can use @kbd{gdb --help}.
1360 @cindex init file name
1361 @cindex @file{.gdbinit}
1362 @cindex @file{gdb.ini}
1363 The @value{GDBN} init files are normally called @file{.gdbinit}.
1364 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1365 the limitations of file names imposed by DOS filesystems. The Windows
1366 port of @value{GDBN} uses the standard name, but if it finds a
1367 @file{gdb.ini} file in your home directory, it warns you about that
1368 and suggests to rename the file to the standard name.
1372 @section Quitting @value{GDBN}
1373 @cindex exiting @value{GDBN}
1374 @cindex leaving @value{GDBN}
1377 @kindex quit @r{[}@var{expression}@r{]}
1378 @kindex q @r{(@code{quit})}
1379 @item quit @r{[}@var{expression}@r{]}
1381 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1382 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1383 do not supply @var{expression}, @value{GDBN} will terminate normally;
1384 otherwise it will terminate using the result of @var{expression} as the
1389 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1390 terminates the action of any @value{GDBN} command that is in progress and
1391 returns to @value{GDBN} command level. It is safe to type the interrupt
1392 character at any time because @value{GDBN} does not allow it to take effect
1393 until a time when it is safe.
1395 If you have been using @value{GDBN} to control an attached process or
1396 device, you can release it with the @code{detach} command
1397 (@pxref{Attach, ,Debugging an Already-running Process}).
1399 @node Shell Commands
1400 @section Shell Commands
1402 If you need to execute occasional shell commands during your
1403 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1404 just use the @code{shell} command.
1409 @cindex shell escape
1410 @item shell @var{command-string}
1411 @itemx !@var{command-string}
1412 Invoke a standard shell to execute @var{command-string}.
1413 Note that no space is needed between @code{!} and @var{command-string}.
1414 If it exists, the environment variable @code{SHELL} determines which
1415 shell to run. Otherwise @value{GDBN} uses the default shell
1416 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1419 The utility @code{make} is often needed in development environments.
1420 You do not have to use the @code{shell} command for this purpose in
1425 @cindex calling make
1426 @item make @var{make-args}
1427 Execute the @code{make} program with the specified
1428 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1431 @node Logging Output
1432 @section Logging Output
1433 @cindex logging @value{GDBN} output
1434 @cindex save @value{GDBN} output to a file
1436 You may want to save the output of @value{GDBN} commands to a file.
1437 There are several commands to control @value{GDBN}'s logging.
1441 @item set logging on
1443 @item set logging off
1445 @cindex logging file name
1446 @item set logging file @var{file}
1447 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1448 @item set logging overwrite [on|off]
1449 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1450 you want @code{set logging on} to overwrite the logfile instead.
1451 @item set logging redirect [on|off]
1452 By default, @value{GDBN} output will go to both the terminal and the logfile.
1453 Set @code{redirect} if you want output to go only to the log file.
1454 @kindex show logging
1456 Show the current values of the logging settings.
1460 @chapter @value{GDBN} Commands
1462 You can abbreviate a @value{GDBN} command to the first few letters of the command
1463 name, if that abbreviation is unambiguous; and you can repeat certain
1464 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1465 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1466 show you the alternatives available, if there is more than one possibility).
1469 * Command Syntax:: How to give commands to @value{GDBN}
1470 * Completion:: Command completion
1471 * Help:: How to ask @value{GDBN} for help
1474 @node Command Syntax
1475 @section Command Syntax
1477 A @value{GDBN} command is a single line of input. There is no limit on
1478 how long it can be. It starts with a command name, which is followed by
1479 arguments whose meaning depends on the command name. For example, the
1480 command @code{step} accepts an argument which is the number of times to
1481 step, as in @samp{step 5}. You can also use the @code{step} command
1482 with no arguments. Some commands do not allow any arguments.
1484 @cindex abbreviation
1485 @value{GDBN} command names may always be truncated if that abbreviation is
1486 unambiguous. Other possible command abbreviations are listed in the
1487 documentation for individual commands. In some cases, even ambiguous
1488 abbreviations are allowed; for example, @code{s} is specially defined as
1489 equivalent to @code{step} even though there are other commands whose
1490 names start with @code{s}. You can test abbreviations by using them as
1491 arguments to the @code{help} command.
1493 @cindex repeating commands
1494 @kindex RET @r{(repeat last command)}
1495 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1496 repeat the previous command. Certain commands (for example, @code{run})
1497 will not repeat this way; these are commands whose unintentional
1498 repetition might cause trouble and which you are unlikely to want to
1499 repeat. User-defined commands can disable this feature; see
1500 @ref{Define, dont-repeat}.
1502 The @code{list} and @code{x} commands, when you repeat them with
1503 @key{RET}, construct new arguments rather than repeating
1504 exactly as typed. This permits easy scanning of source or memory.
1506 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1507 output, in a way similar to the common utility @code{more}
1508 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1509 @key{RET} too many in this situation, @value{GDBN} disables command
1510 repetition after any command that generates this sort of display.
1512 @kindex # @r{(a comment)}
1514 Any text from a @kbd{#} to the end of the line is a comment; it does
1515 nothing. This is useful mainly in command files (@pxref{Command
1516 Files,,Command Files}).
1518 @cindex repeating command sequences
1519 @kindex Ctrl-o @r{(operate-and-get-next)}
1520 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1521 commands. This command accepts the current line, like @key{RET}, and
1522 then fetches the next line relative to the current line from the history
1526 @section Command Completion
1529 @cindex word completion
1530 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1531 only one possibility; it can also show you what the valid possibilities
1532 are for the next word in a command, at any time. This works for @value{GDBN}
1533 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1535 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1536 of a word. If there is only one possibility, @value{GDBN} fills in the
1537 word, and waits for you to finish the command (or press @key{RET} to
1538 enter it). For example, if you type
1540 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1541 @c complete accuracy in these examples; space introduced for clarity.
1542 @c If texinfo enhancements make it unnecessary, it would be nice to
1543 @c replace " @key" by "@key" in the following...
1545 (@value{GDBP}) info bre @key{TAB}
1549 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1550 the only @code{info} subcommand beginning with @samp{bre}:
1553 (@value{GDBP}) info breakpoints
1557 You can either press @key{RET} at this point, to run the @code{info
1558 breakpoints} command, or backspace and enter something else, if
1559 @samp{breakpoints} does not look like the command you expected. (If you
1560 were sure you wanted @code{info breakpoints} in the first place, you
1561 might as well just type @key{RET} immediately after @samp{info bre},
1562 to exploit command abbreviations rather than command completion).
1564 If there is more than one possibility for the next word when you press
1565 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1566 characters and try again, or just press @key{TAB} a second time;
1567 @value{GDBN} displays all the possible completions for that word. For
1568 example, you might want to set a breakpoint on a subroutine whose name
1569 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1570 just sounds the bell. Typing @key{TAB} again displays all the
1571 function names in your program that begin with those characters, for
1575 (@value{GDBP}) b make_ @key{TAB}
1576 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1577 make_a_section_from_file make_environ
1578 make_abs_section make_function_type
1579 make_blockvector make_pointer_type
1580 make_cleanup make_reference_type
1581 make_command make_symbol_completion_list
1582 (@value{GDBP}) b make_
1586 After displaying the available possibilities, @value{GDBN} copies your
1587 partial input (@samp{b make_} in the example) so you can finish the
1590 If you just want to see the list of alternatives in the first place, you
1591 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1592 means @kbd{@key{META} ?}. You can type this either by holding down a
1593 key designated as the @key{META} shift on your keyboard (if there is
1594 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1596 If the number of possible completions is large, @value{GDBN} will
1597 print as much of the list as it has collected, as well as a message
1598 indicating that the list may be truncated.
1601 (@value{GDBP}) b m@key{TAB}@key{TAB}
1603 <... the rest of the possible completions ...>
1604 *** List may be truncated, max-completions reached. ***
1609 This behavior can be controlled with the following commands:
1612 @kindex set max-completions
1613 @item set max-completions @var{limit}
1614 @itemx set max-completions unlimited
1615 Set the maximum number of completion candidates. @value{GDBN} will
1616 stop looking for more completions once it collects this many candidates.
1617 This is useful when completing on things like function names as collecting
1618 all the possible candidates can be time consuming.
1619 The default value is 200. A value of zero disables tab-completion.
1620 Note that setting either no limit or a very large limit can make
1622 @kindex show max-completions
1623 @item show max-completions
1624 Show the maximum number of candidates that @value{GDBN} will collect and show
1628 @cindex quotes in commands
1629 @cindex completion of quoted strings
1630 Sometimes the string you need, while logically a ``word'', may contain
1631 parentheses or other characters that @value{GDBN} normally excludes from
1632 its notion of a word. To permit word completion to work in this
1633 situation, you may enclose words in @code{'} (single quote marks) in
1634 @value{GDBN} commands.
1636 The most likely situation where you might need this is in typing the
1637 name of a C@t{++} function. This is because C@t{++} allows function
1638 overloading (multiple definitions of the same function, distinguished
1639 by argument type). For example, when you want to set a breakpoint you
1640 may need to distinguish whether you mean the version of @code{name}
1641 that takes an @code{int} parameter, @code{name(int)}, or the version
1642 that takes a @code{float} parameter, @code{name(float)}. To use the
1643 word-completion facilities in this situation, type a single quote
1644 @code{'} at the beginning of the function name. This alerts
1645 @value{GDBN} that it may need to consider more information than usual
1646 when you press @key{TAB} or @kbd{M-?} to request word completion:
1649 (@value{GDBP}) b 'bubble( @kbd{M-?}
1650 bubble(double,double) bubble(int,int)
1651 (@value{GDBP}) b 'bubble(
1654 In some cases, @value{GDBN} can tell that completing a name requires using
1655 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1656 completing as much as it can) if you do not type the quote in the first
1660 (@value{GDBP}) b bub @key{TAB}
1661 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1662 (@value{GDBP}) b 'bubble(
1666 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1667 you have not yet started typing the argument list when you ask for
1668 completion on an overloaded symbol.
1670 For more information about overloaded functions, see @ref{C Plus Plus
1671 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1672 overload-resolution off} to disable overload resolution;
1673 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1675 @cindex completion of structure field names
1676 @cindex structure field name completion
1677 @cindex completion of union field names
1678 @cindex union field name completion
1679 When completing in an expression which looks up a field in a
1680 structure, @value{GDBN} also tries@footnote{The completer can be
1681 confused by certain kinds of invalid expressions. Also, it only
1682 examines the static type of the expression, not the dynamic type.} to
1683 limit completions to the field names available in the type of the
1687 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1688 magic to_fputs to_rewind
1689 to_data to_isatty to_write
1690 to_delete to_put to_write_async_safe
1695 This is because the @code{gdb_stdout} is a variable of the type
1696 @code{struct ui_file} that is defined in @value{GDBN} sources as
1703 ui_file_flush_ftype *to_flush;
1704 ui_file_write_ftype *to_write;
1705 ui_file_write_async_safe_ftype *to_write_async_safe;
1706 ui_file_fputs_ftype *to_fputs;
1707 ui_file_read_ftype *to_read;
1708 ui_file_delete_ftype *to_delete;
1709 ui_file_isatty_ftype *to_isatty;
1710 ui_file_rewind_ftype *to_rewind;
1711 ui_file_put_ftype *to_put;
1718 @section Getting Help
1719 @cindex online documentation
1722 You can always ask @value{GDBN} itself for information on its commands,
1723 using the command @code{help}.
1726 @kindex h @r{(@code{help})}
1729 You can use @code{help} (abbreviated @code{h}) with no arguments to
1730 display a short list of named classes of commands:
1734 List of classes of commands:
1736 aliases -- Aliases of other commands
1737 breakpoints -- Making program stop at certain points
1738 data -- Examining data
1739 files -- Specifying and examining files
1740 internals -- Maintenance commands
1741 obscure -- Obscure features
1742 running -- Running the program
1743 stack -- Examining the stack
1744 status -- Status inquiries
1745 support -- Support facilities
1746 tracepoints -- Tracing of program execution without
1747 stopping the program
1748 user-defined -- User-defined commands
1750 Type "help" followed by a class name for a list of
1751 commands in that class.
1752 Type "help" followed by command name for full
1754 Command name abbreviations are allowed if unambiguous.
1757 @c the above line break eliminates huge line overfull...
1759 @item help @var{class}
1760 Using one of the general help classes as an argument, you can get a
1761 list of the individual commands in that class. For example, here is the
1762 help display for the class @code{status}:
1765 (@value{GDBP}) help status
1770 @c Line break in "show" line falsifies real output, but needed
1771 @c to fit in smallbook page size.
1772 info -- Generic command for showing things
1773 about the program being debugged
1774 show -- Generic command for showing things
1777 Type "help" followed by command name for full
1779 Command name abbreviations are allowed if unambiguous.
1783 @item help @var{command}
1784 With a command name as @code{help} argument, @value{GDBN} displays a
1785 short paragraph on how to use that command.
1788 @item apropos @var{args}
1789 The @code{apropos} command searches through all of the @value{GDBN}
1790 commands, and their documentation, for the regular expression specified in
1791 @var{args}. It prints out all matches found. For example:
1802 alias -- Define a new command that is an alias of an existing command
1803 aliases -- Aliases of other commands
1804 d -- Delete some breakpoints or auto-display expressions
1805 del -- Delete some breakpoints or auto-display expressions
1806 delete -- Delete some breakpoints or auto-display expressions
1811 @item complete @var{args}
1812 The @code{complete @var{args}} command lists all the possible completions
1813 for the beginning of a command. Use @var{args} to specify the beginning of the
1814 command you want completed. For example:
1820 @noindent results in:
1831 @noindent This is intended for use by @sc{gnu} Emacs.
1834 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1835 and @code{show} to inquire about the state of your program, or the state
1836 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1837 manual introduces each of them in the appropriate context. The listings
1838 under @code{info} and under @code{show} in the Command, Variable, and
1839 Function Index point to all the sub-commands. @xref{Command and Variable
1845 @kindex i @r{(@code{info})}
1847 This command (abbreviated @code{i}) is for describing the state of your
1848 program. For example, you can show the arguments passed to a function
1849 with @code{info args}, list the registers currently in use with @code{info
1850 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1851 You can get a complete list of the @code{info} sub-commands with
1852 @w{@code{help info}}.
1856 You can assign the result of an expression to an environment variable with
1857 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1858 @code{set prompt $}.
1862 In contrast to @code{info}, @code{show} is for describing the state of
1863 @value{GDBN} itself.
1864 You can change most of the things you can @code{show}, by using the
1865 related command @code{set}; for example, you can control what number
1866 system is used for displays with @code{set radix}, or simply inquire
1867 which is currently in use with @code{show radix}.
1870 To display all the settable parameters and their current
1871 values, you can use @code{show} with no arguments; you may also use
1872 @code{info set}. Both commands produce the same display.
1873 @c FIXME: "info set" violates the rule that "info" is for state of
1874 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1875 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1879 Here are several miscellaneous @code{show} subcommands, all of which are
1880 exceptional in lacking corresponding @code{set} commands:
1883 @kindex show version
1884 @cindex @value{GDBN} version number
1886 Show what version of @value{GDBN} is running. You should include this
1887 information in @value{GDBN} bug-reports. If multiple versions of
1888 @value{GDBN} are in use at your site, you may need to determine which
1889 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1890 commands are introduced, and old ones may wither away. Also, many
1891 system vendors ship variant versions of @value{GDBN}, and there are
1892 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1893 The version number is the same as the one announced when you start
1896 @kindex show copying
1897 @kindex info copying
1898 @cindex display @value{GDBN} copyright
1901 Display information about permission for copying @value{GDBN}.
1903 @kindex show warranty
1904 @kindex info warranty
1906 @itemx info warranty
1907 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1908 if your version of @value{GDBN} comes with one.
1910 @kindex show configuration
1911 @item show configuration
1912 Display detailed information about the way @value{GDBN} was configured
1913 when it was built. This displays the optional arguments passed to the
1914 @file{configure} script and also configuration parameters detected
1915 automatically by @command{configure}. When reporting a @value{GDBN}
1916 bug (@pxref{GDB Bugs}), it is important to include this information in
1922 @chapter Running Programs Under @value{GDBN}
1924 When you run a program under @value{GDBN}, you must first generate
1925 debugging information when you compile it.
1927 You may start @value{GDBN} with its arguments, if any, in an environment
1928 of your choice. If you are doing native debugging, you may redirect
1929 your program's input and output, debug an already running process, or
1930 kill a child process.
1933 * Compilation:: Compiling for debugging
1934 * Starting:: Starting your program
1935 * Arguments:: Your program's arguments
1936 * Environment:: Your program's environment
1938 * Working Directory:: Your program's working directory
1939 * Input/Output:: Your program's input and output
1940 * Attach:: Debugging an already-running process
1941 * Kill Process:: Killing the child process
1943 * Inferiors and Programs:: Debugging multiple inferiors and programs
1944 * Threads:: Debugging programs with multiple threads
1945 * Forks:: Debugging forks
1946 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1950 @section Compiling for Debugging
1952 In order to debug a program effectively, you need to generate
1953 debugging information when you compile it. This debugging information
1954 is stored in the object file; it describes the data type of each
1955 variable or function and the correspondence between source line numbers
1956 and addresses in the executable code.
1958 To request debugging information, specify the @samp{-g} option when you run
1961 Programs that are to be shipped to your customers are compiled with
1962 optimizations, using the @samp{-O} compiler option. However, some
1963 compilers are unable to handle the @samp{-g} and @samp{-O} options
1964 together. Using those compilers, you cannot generate optimized
1965 executables containing debugging information.
1967 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1968 without @samp{-O}, making it possible to debug optimized code. We
1969 recommend that you @emph{always} use @samp{-g} whenever you compile a
1970 program. You may think your program is correct, but there is no sense
1971 in pushing your luck. For more information, see @ref{Optimized Code}.
1973 Older versions of the @sc{gnu} C compiler permitted a variant option
1974 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1975 format; if your @sc{gnu} C compiler has this option, do not use it.
1977 @value{GDBN} knows about preprocessor macros and can show you their
1978 expansion (@pxref{Macros}). Most compilers do not include information
1979 about preprocessor macros in the debugging information if you specify
1980 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
1981 the @sc{gnu} C compiler, provides macro information if you are using
1982 the DWARF debugging format, and specify the option @option{-g3}.
1984 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1985 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1986 information on @value{NGCC} options affecting debug information.
1988 You will have the best debugging experience if you use the latest
1989 version of the DWARF debugging format that your compiler supports.
1990 DWARF is currently the most expressive and best supported debugging
1991 format in @value{GDBN}.
1995 @section Starting your Program
2001 @kindex r @r{(@code{run})}
2004 Use the @code{run} command to start your program under @value{GDBN}.
2005 You must first specify the program name with an argument to
2006 @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
2007 @value{GDBN}}), or by using the @code{file} or @code{exec-file}
2008 command (@pxref{Files, ,Commands to Specify Files}).
2012 If you are running your program in an execution environment that
2013 supports processes, @code{run} creates an inferior process and makes
2014 that process run your program. In some environments without processes,
2015 @code{run} jumps to the start of your program. Other targets,
2016 like @samp{remote}, are always running. If you get an error
2017 message like this one:
2020 The "remote" target does not support "run".
2021 Try "help target" or "continue".
2025 then use @code{continue} to run your program. You may need @code{load}
2026 first (@pxref{load}).
2028 The execution of a program is affected by certain information it
2029 receives from its superior. @value{GDBN} provides ways to specify this
2030 information, which you must do @emph{before} starting your program. (You
2031 can change it after starting your program, but such changes only affect
2032 your program the next time you start it.) This information may be
2033 divided into four categories:
2036 @item The @emph{arguments.}
2037 Specify the arguments to give your program as the arguments of the
2038 @code{run} command. If a shell is available on your target, the shell
2039 is used to pass the arguments, so that you may use normal conventions
2040 (such as wildcard expansion or variable substitution) in describing
2042 In Unix systems, you can control which shell is used with the
2043 @code{SHELL} environment variable. If you do not define @code{SHELL},
2044 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2045 use of any shell with the @code{set startup-with-shell} command (see
2048 @item The @emph{environment.}
2049 Your program normally inherits its environment from @value{GDBN}, but you can
2050 use the @value{GDBN} commands @code{set environment} and @code{unset
2051 environment} to change parts of the environment that affect
2052 your program. @xref{Environment, ,Your Program's Environment}.
2054 @item The @emph{working directory.}
2055 Your program inherits its working directory from @value{GDBN}. You can set
2056 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
2057 @xref{Working Directory, ,Your Program's Working Directory}.
2059 @item The @emph{standard input and output.}
2060 Your program normally uses the same device for standard input and
2061 standard output as @value{GDBN} is using. You can redirect input and output
2062 in the @code{run} command line, or you can use the @code{tty} command to
2063 set a different device for your program.
2064 @xref{Input/Output, ,Your Program's Input and Output}.
2067 @emph{Warning:} While input and output redirection work, you cannot use
2068 pipes to pass the output of the program you are debugging to another
2069 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2073 When you issue the @code{run} command, your program begins to execute
2074 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2075 of how to arrange for your program to stop. Once your program has
2076 stopped, you may call functions in your program, using the @code{print}
2077 or @code{call} commands. @xref{Data, ,Examining Data}.
2079 If the modification time of your symbol file has changed since the last
2080 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2081 table, and reads it again. When it does this, @value{GDBN} tries to retain
2082 your current breakpoints.
2087 @cindex run to main procedure
2088 The name of the main procedure can vary from language to language.
2089 With C or C@t{++}, the main procedure name is always @code{main}, but
2090 other languages such as Ada do not require a specific name for their
2091 main procedure. The debugger provides a convenient way to start the
2092 execution of the program and to stop at the beginning of the main
2093 procedure, depending on the language used.
2095 The @samp{start} command does the equivalent of setting a temporary
2096 breakpoint at the beginning of the main procedure and then invoking
2097 the @samp{run} command.
2099 @cindex elaboration phase
2100 Some programs contain an @dfn{elaboration} phase where some startup code is
2101 executed before the main procedure is called. This depends on the
2102 languages used to write your program. In C@t{++}, for instance,
2103 constructors for static and global objects are executed before
2104 @code{main} is called. It is therefore possible that the debugger stops
2105 before reaching the main procedure. However, the temporary breakpoint
2106 will remain to halt execution.
2108 Specify the arguments to give to your program as arguments to the
2109 @samp{start} command. These arguments will be given verbatim to the
2110 underlying @samp{run} command. Note that the same arguments will be
2111 reused if no argument is provided during subsequent calls to
2112 @samp{start} or @samp{run}.
2114 It is sometimes necessary to debug the program during elaboration. In
2115 these cases, using the @code{start} command would stop the execution of
2116 your program too late, as the program would have already completed the
2117 elaboration phase. Under these circumstances, insert breakpoints in your
2118 elaboration code before running your program.
2120 @anchor{set exec-wrapper}
2121 @kindex set exec-wrapper
2122 @item set exec-wrapper @var{wrapper}
2123 @itemx show exec-wrapper
2124 @itemx unset exec-wrapper
2125 When @samp{exec-wrapper} is set, the specified wrapper is used to
2126 launch programs for debugging. @value{GDBN} starts your program
2127 with a shell command of the form @kbd{exec @var{wrapper}
2128 @var{program}}. Quoting is added to @var{program} and its
2129 arguments, but not to @var{wrapper}, so you should add quotes if
2130 appropriate for your shell. The wrapper runs until it executes
2131 your program, and then @value{GDBN} takes control.
2133 You can use any program that eventually calls @code{execve} with
2134 its arguments as a wrapper. Several standard Unix utilities do
2135 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2136 with @code{exec "$@@"} will also work.
2138 For example, you can use @code{env} to pass an environment variable to
2139 the debugged program, without setting the variable in your shell's
2143 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2147 This command is available when debugging locally on most targets, excluding
2148 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2150 @kindex set startup-with-shell
2151 @item set startup-with-shell
2152 @itemx set startup-with-shell on
2153 @itemx set startup-with-shell off
2154 @itemx show set startup-with-shell
2155 On Unix systems, by default, if a shell is available on your target,
2156 @value{GDBN}) uses it to start your program. Arguments of the
2157 @code{run} command are passed to the shell, which does variable
2158 substitution, expands wildcard characters and performs redirection of
2159 I/O. In some circumstances, it may be useful to disable such use of a
2160 shell, for example, when debugging the shell itself or diagnosing
2161 startup failures such as:
2165 Starting program: ./a.out
2166 During startup program terminated with signal SIGSEGV, Segmentation fault.
2170 which indicates the shell or the wrapper specified with
2171 @samp{exec-wrapper} crashed, not your program. Most often, this is
2172 caused by something odd in your shell's non-interactive mode
2173 initialization file---such as @file{.cshrc} for C-shell,
2174 $@file{.zshenv} for the Z shell, or the file specified in the
2175 @samp{BASH_ENV} environment variable for BASH.
2177 @anchor{set auto-connect-native-target}
2178 @kindex set auto-connect-native-target
2179 @item set auto-connect-native-target
2180 @itemx set auto-connect-native-target on
2181 @itemx set auto-connect-native-target off
2182 @itemx show auto-connect-native-target
2184 By default, if not connected to any target yet (e.g., with
2185 @code{target remote}), the @code{run} command starts your program as a
2186 native process under @value{GDBN}, on your local machine. If you're
2187 sure you don't want to debug programs on your local machine, you can
2188 tell @value{GDBN} to not connect to the native target automatically
2189 with the @code{set auto-connect-native-target off} command.
2191 If @code{on}, which is the default, and if @value{GDBN} is not
2192 connected to a target already, the @code{run} command automaticaly
2193 connects to the native target, if one is available.
2195 If @code{off}, and if @value{GDBN} is not connected to a target
2196 already, the @code{run} command fails with an error:
2200 Don't know how to run. Try "help target".
2203 If @value{GDBN} is already connected to a target, @value{GDBN} always
2204 uses it with the @code{run} command.
2206 In any case, you can explicitly connect to the native target with the
2207 @code{target native} command. For example,
2210 (@value{GDBP}) set auto-connect-native-target off
2212 Don't know how to run. Try "help target".
2213 (@value{GDBP}) target native
2215 Starting program: ./a.out
2216 [Inferior 1 (process 10421) exited normally]
2219 In case you connected explicitly to the @code{native} target,
2220 @value{GDBN} remains connected even if all inferiors exit, ready for
2221 the next @code{run} command. Use the @code{disconnect} command to
2224 Examples of other commands that likewise respect the
2225 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2226 proc}, @code{info os}.
2228 @kindex set disable-randomization
2229 @item set disable-randomization
2230 @itemx set disable-randomization on
2231 This option (enabled by default in @value{GDBN}) will turn off the native
2232 randomization of the virtual address space of the started program. This option
2233 is useful for multiple debugging sessions to make the execution better
2234 reproducible and memory addresses reusable across debugging sessions.
2236 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2237 On @sc{gnu}/Linux you can get the same behavior using
2240 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2243 @item set disable-randomization off
2244 Leave the behavior of the started executable unchanged. Some bugs rear their
2245 ugly heads only when the program is loaded at certain addresses. If your bug
2246 disappears when you run the program under @value{GDBN}, that might be because
2247 @value{GDBN} by default disables the address randomization on platforms, such
2248 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2249 disable-randomization off} to try to reproduce such elusive bugs.
2251 On targets where it is available, virtual address space randomization
2252 protects the programs against certain kinds of security attacks. In these
2253 cases the attacker needs to know the exact location of a concrete executable
2254 code. Randomizing its location makes it impossible to inject jumps misusing
2255 a code at its expected addresses.
2257 Prelinking shared libraries provides a startup performance advantage but it
2258 makes addresses in these libraries predictable for privileged processes by
2259 having just unprivileged access at the target system. Reading the shared
2260 library binary gives enough information for assembling the malicious code
2261 misusing it. Still even a prelinked shared library can get loaded at a new
2262 random address just requiring the regular relocation process during the
2263 startup. Shared libraries not already prelinked are always loaded at
2264 a randomly chosen address.
2266 Position independent executables (PIE) contain position independent code
2267 similar to the shared libraries and therefore such executables get loaded at
2268 a randomly chosen address upon startup. PIE executables always load even
2269 already prelinked shared libraries at a random address. You can build such
2270 executable using @command{gcc -fPIE -pie}.
2272 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2273 (as long as the randomization is enabled).
2275 @item show disable-randomization
2276 Show the current setting of the explicit disable of the native randomization of
2277 the virtual address space of the started program.
2282 @section Your Program's Arguments
2284 @cindex arguments (to your program)
2285 The arguments to your program can be specified by the arguments of the
2287 They are passed to a shell, which expands wildcard characters and
2288 performs redirection of I/O, and thence to your program. Your
2289 @code{SHELL} environment variable (if it exists) specifies what shell
2290 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2291 the default shell (@file{/bin/sh} on Unix).
2293 On non-Unix systems, the program is usually invoked directly by
2294 @value{GDBN}, which emulates I/O redirection via the appropriate system
2295 calls, and the wildcard characters are expanded by the startup code of
2296 the program, not by the shell.
2298 @code{run} with no arguments uses the same arguments used by the previous
2299 @code{run}, or those set by the @code{set args} command.
2304 Specify the arguments to be used the next time your program is run. If
2305 @code{set args} has no arguments, @code{run} executes your program
2306 with no arguments. Once you have run your program with arguments,
2307 using @code{set args} before the next @code{run} is the only way to run
2308 it again without arguments.
2312 Show the arguments to give your program when it is started.
2316 @section Your Program's Environment
2318 @cindex environment (of your program)
2319 The @dfn{environment} consists of a set of environment variables and
2320 their values. Environment variables conventionally record such things as
2321 your user name, your home directory, your terminal type, and your search
2322 path for programs to run. Usually you set up environment variables with
2323 the shell and they are inherited by all the other programs you run. When
2324 debugging, it can be useful to try running your program with a modified
2325 environment without having to start @value{GDBN} over again.
2329 @item path @var{directory}
2330 Add @var{directory} to the front of the @code{PATH} environment variable
2331 (the search path for executables) that will be passed to your program.
2332 The value of @code{PATH} used by @value{GDBN} does not change.
2333 You may specify several directory names, separated by whitespace or by a
2334 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2335 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2336 is moved to the front, so it is searched sooner.
2338 You can use the string @samp{$cwd} to refer to whatever is the current
2339 working directory at the time @value{GDBN} searches the path. If you
2340 use @samp{.} instead, it refers to the directory where you executed the
2341 @code{path} command. @value{GDBN} replaces @samp{.} in the
2342 @var{directory} argument (with the current path) before adding
2343 @var{directory} to the search path.
2344 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2345 @c document that, since repeating it would be a no-op.
2349 Display the list of search paths for executables (the @code{PATH}
2350 environment variable).
2352 @kindex show environment
2353 @item show environment @r{[}@var{varname}@r{]}
2354 Print the value of environment variable @var{varname} to be given to
2355 your program when it starts. If you do not supply @var{varname},
2356 print the names and values of all environment variables to be given to
2357 your program. You can abbreviate @code{environment} as @code{env}.
2359 @kindex set environment
2360 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2361 Set environment variable @var{varname} to @var{value}. The value
2362 changes for your program (and the shell @value{GDBN} uses to launch
2363 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2364 values of environment variables are just strings, and any
2365 interpretation is supplied by your program itself. The @var{value}
2366 parameter is optional; if it is eliminated, the variable is set to a
2368 @c "any string" here does not include leading, trailing
2369 @c blanks. Gnu asks: does anyone care?
2371 For example, this command:
2378 tells the debugged program, when subsequently run, that its user is named
2379 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2380 are not actually required.)
2382 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2383 which also inherits the environment set with @code{set environment}.
2384 If necessary, you can avoid that by using the @samp{env} program as a
2385 wrapper instead of using @code{set environment}. @xref{set
2386 exec-wrapper}, for an example doing just that.
2388 @kindex unset environment
2389 @item unset environment @var{varname}
2390 Remove variable @var{varname} from the environment to be passed to your
2391 program. This is different from @samp{set env @var{varname} =};
2392 @code{unset environment} removes the variable from the environment,
2393 rather than assigning it an empty value.
2396 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2397 the shell indicated by your @code{SHELL} environment variable if it
2398 exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
2399 names a shell that runs an initialization file when started
2400 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2401 for the Z shell, or the file specified in the @samp{BASH_ENV}
2402 environment variable for BASH---any variables you set in that file
2403 affect your program. You may wish to move setting of environment
2404 variables to files that are only run when you sign on, such as
2405 @file{.login} or @file{.profile}.
2407 @node Working Directory
2408 @section Your Program's Working Directory
2410 @cindex working directory (of your program)
2411 Each time you start your program with @code{run}, it inherits its
2412 working directory from the current working directory of @value{GDBN}.
2413 The @value{GDBN} working directory is initially whatever it inherited
2414 from its parent process (typically the shell), but you can specify a new
2415 working directory in @value{GDBN} with the @code{cd} command.
2417 The @value{GDBN} working directory also serves as a default for the commands
2418 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2423 @cindex change working directory
2424 @item cd @r{[}@var{directory}@r{]}
2425 Set the @value{GDBN} working directory to @var{directory}. If not
2426 given, @var{directory} uses @file{'~'}.
2430 Print the @value{GDBN} working directory.
2433 It is generally impossible to find the current working directory of
2434 the process being debugged (since a program can change its directory
2435 during its run). If you work on a system where @value{GDBN} is
2436 configured with the @file{/proc} support, you can use the @code{info
2437 proc} command (@pxref{SVR4 Process Information}) to find out the
2438 current working directory of the debuggee.
2441 @section Your Program's Input and Output
2446 By default, the program you run under @value{GDBN} does input and output to
2447 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2448 to its own terminal modes to interact with you, but it records the terminal
2449 modes your program was using and switches back to them when you continue
2450 running your program.
2453 @kindex info terminal
2455 Displays information recorded by @value{GDBN} about the terminal modes your
2459 You can redirect your program's input and/or output using shell
2460 redirection with the @code{run} command. For example,
2467 starts your program, diverting its output to the file @file{outfile}.
2470 @cindex controlling terminal
2471 Another way to specify where your program should do input and output is
2472 with the @code{tty} command. This command accepts a file name as
2473 argument, and causes this file to be the default for future @code{run}
2474 commands. It also resets the controlling terminal for the child
2475 process, for future @code{run} commands. For example,
2482 directs that processes started with subsequent @code{run} commands
2483 default to do input and output on the terminal @file{/dev/ttyb} and have
2484 that as their controlling terminal.
2486 An explicit redirection in @code{run} overrides the @code{tty} command's
2487 effect on the input/output device, but not its effect on the controlling
2490 When you use the @code{tty} command or redirect input in the @code{run}
2491 command, only the input @emph{for your program} is affected. The input
2492 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2493 for @code{set inferior-tty}.
2495 @cindex inferior tty
2496 @cindex set inferior controlling terminal
2497 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2498 display the name of the terminal that will be used for future runs of your
2502 @item set inferior-tty /dev/ttyb
2503 @kindex set inferior-tty
2504 Set the tty for the program being debugged to /dev/ttyb.
2506 @item show inferior-tty
2507 @kindex show inferior-tty
2508 Show the current tty for the program being debugged.
2512 @section Debugging an Already-running Process
2517 @item attach @var{process-id}
2518 This command attaches to a running process---one that was started
2519 outside @value{GDBN}. (@code{info files} shows your active
2520 targets.) The command takes as argument a process ID. The usual way to
2521 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2522 or with the @samp{jobs -l} shell command.
2524 @code{attach} does not repeat if you press @key{RET} a second time after
2525 executing the command.
2528 To use @code{attach}, your program must be running in an environment
2529 which supports processes; for example, @code{attach} does not work for
2530 programs on bare-board targets that lack an operating system. You must
2531 also have permission to send the process a signal.
2533 When you use @code{attach}, the debugger finds the program running in
2534 the process first by looking in the current working directory, then (if
2535 the program is not found) by using the source file search path
2536 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2537 the @code{file} command to load the program. @xref{Files, ,Commands to
2540 The first thing @value{GDBN} does after arranging to debug the specified
2541 process is to stop it. You can examine and modify an attached process
2542 with all the @value{GDBN} commands that are ordinarily available when
2543 you start processes with @code{run}. You can insert breakpoints; you
2544 can step and continue; you can modify storage. If you would rather the
2545 process continue running, you may use the @code{continue} command after
2546 attaching @value{GDBN} to the process.
2551 When you have finished debugging the attached process, you can use the
2552 @code{detach} command to release it from @value{GDBN} control. Detaching
2553 the process continues its execution. After the @code{detach} command,
2554 that process and @value{GDBN} become completely independent once more, and you
2555 are ready to @code{attach} another process or start one with @code{run}.
2556 @code{detach} does not repeat if you press @key{RET} again after
2557 executing the command.
2560 If you exit @value{GDBN} while you have an attached process, you detach
2561 that process. If you use the @code{run} command, you kill that process.
2562 By default, @value{GDBN} asks for confirmation if you try to do either of these
2563 things; you can control whether or not you need to confirm by using the
2564 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2568 @section Killing the Child Process
2573 Kill the child process in which your program is running under @value{GDBN}.
2576 This command is useful if you wish to debug a core dump instead of a
2577 running process. @value{GDBN} ignores any core dump file while your program
2580 On some operating systems, a program cannot be executed outside @value{GDBN}
2581 while you have breakpoints set on it inside @value{GDBN}. You can use the
2582 @code{kill} command in this situation to permit running your program
2583 outside the debugger.
2585 The @code{kill} command is also useful if you wish to recompile and
2586 relink your program, since on many systems it is impossible to modify an
2587 executable file while it is running in a process. In this case, when you
2588 next type @code{run}, @value{GDBN} notices that the file has changed, and
2589 reads the symbol table again (while trying to preserve your current
2590 breakpoint settings).
2592 @node Inferiors and Programs
2593 @section Debugging Multiple Inferiors and Programs
2595 @value{GDBN} lets you run and debug multiple programs in a single
2596 session. In addition, @value{GDBN} on some systems may let you run
2597 several programs simultaneously (otherwise you have to exit from one
2598 before starting another). In the most general case, you can have
2599 multiple threads of execution in each of multiple processes, launched
2600 from multiple executables.
2603 @value{GDBN} represents the state of each program execution with an
2604 object called an @dfn{inferior}. An inferior typically corresponds to
2605 a process, but is more general and applies also to targets that do not
2606 have processes. Inferiors may be created before a process runs, and
2607 may be retained after a process exits. Inferiors have unique
2608 identifiers that are different from process ids. Usually each
2609 inferior will also have its own distinct address space, although some
2610 embedded targets may have several inferiors running in different parts
2611 of a single address space. Each inferior may in turn have multiple
2612 threads running in it.
2614 To find out what inferiors exist at any moment, use @w{@code{info
2618 @kindex info inferiors
2619 @item info inferiors
2620 Print a list of all inferiors currently being managed by @value{GDBN}.
2622 @value{GDBN} displays for each inferior (in this order):
2626 the inferior number assigned by @value{GDBN}
2629 the target system's inferior identifier
2632 the name of the executable the inferior is running.
2637 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2638 indicates the current inferior.
2642 @c end table here to get a little more width for example
2645 (@value{GDBP}) info inferiors
2646 Num Description Executable
2647 2 process 2307 hello
2648 * 1 process 3401 goodbye
2651 To switch focus between inferiors, use the @code{inferior} command:
2654 @kindex inferior @var{infno}
2655 @item inferior @var{infno}
2656 Make inferior number @var{infno} the current inferior. The argument
2657 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2658 in the first field of the @samp{info inferiors} display.
2662 You can get multiple executables into a debugging session via the
2663 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2664 systems @value{GDBN} can add inferiors to the debug session
2665 automatically by following calls to @code{fork} and @code{exec}. To
2666 remove inferiors from the debugging session use the
2667 @w{@code{remove-inferiors}} command.
2670 @kindex add-inferior
2671 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2672 Adds @var{n} inferiors to be run using @var{executable} as the
2673 executable; @var{n} defaults to 1. If no executable is specified,
2674 the inferiors begins empty, with no program. You can still assign or
2675 change the program assigned to the inferior at any time by using the
2676 @code{file} command with the executable name as its argument.
2678 @kindex clone-inferior
2679 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2680 Adds @var{n} inferiors ready to execute the same program as inferior
2681 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
2682 number of the current inferior. This is a convenient command when you
2683 want to run another instance of the inferior you are debugging.
2686 (@value{GDBP}) info inferiors
2687 Num Description Executable
2688 * 1 process 29964 helloworld
2689 (@value{GDBP}) clone-inferior
2692 (@value{GDBP}) info inferiors
2693 Num Description Executable
2695 * 1 process 29964 helloworld
2698 You can now simply switch focus to inferior 2 and run it.
2700 @kindex remove-inferiors
2701 @item remove-inferiors @var{infno}@dots{}
2702 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2703 possible to remove an inferior that is running with this command. For
2704 those, use the @code{kill} or @code{detach} command first.
2708 To quit debugging one of the running inferiors that is not the current
2709 inferior, you can either detach from it by using the @w{@code{detach
2710 inferior}} command (allowing it to run independently), or kill it
2711 using the @w{@code{kill inferiors}} command:
2714 @kindex detach inferiors @var{infno}@dots{}
2715 @item detach inferior @var{infno}@dots{}
2716 Detach from the inferior or inferiors identified by @value{GDBN}
2717 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2718 still stays on the list of inferiors shown by @code{info inferiors},
2719 but its Description will show @samp{<null>}.
2721 @kindex kill inferiors @var{infno}@dots{}
2722 @item kill inferiors @var{infno}@dots{}
2723 Kill the inferior or inferiors identified by @value{GDBN} inferior
2724 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2725 stays on the list of inferiors shown by @code{info inferiors}, but its
2726 Description will show @samp{<null>}.
2729 After the successful completion of a command such as @code{detach},
2730 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2731 a normal process exit, the inferior is still valid and listed with
2732 @code{info inferiors}, ready to be restarted.
2735 To be notified when inferiors are started or exit under @value{GDBN}'s
2736 control use @w{@code{set print inferior-events}}:
2739 @kindex set print inferior-events
2740 @cindex print messages on inferior start and exit
2741 @item set print inferior-events
2742 @itemx set print inferior-events on
2743 @itemx set print inferior-events off
2744 The @code{set print inferior-events} command allows you to enable or
2745 disable printing of messages when @value{GDBN} notices that new
2746 inferiors have started or that inferiors have exited or have been
2747 detached. By default, these messages will not be printed.
2749 @kindex show print inferior-events
2750 @item show print inferior-events
2751 Show whether messages will be printed when @value{GDBN} detects that
2752 inferiors have started, exited or have been detached.
2755 Many commands will work the same with multiple programs as with a
2756 single program: e.g., @code{print myglobal} will simply display the
2757 value of @code{myglobal} in the current inferior.
2760 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2761 get more info about the relationship of inferiors, programs, address
2762 spaces in a debug session. You can do that with the @w{@code{maint
2763 info program-spaces}} command.
2766 @kindex maint info program-spaces
2767 @item maint info program-spaces
2768 Print a list of all program spaces currently being managed by
2771 @value{GDBN} displays for each program space (in this order):
2775 the program space number assigned by @value{GDBN}
2778 the name of the executable loaded into the program space, with e.g.,
2779 the @code{file} command.
2784 An asterisk @samp{*} preceding the @value{GDBN} program space number
2785 indicates the current program space.
2787 In addition, below each program space line, @value{GDBN} prints extra
2788 information that isn't suitable to display in tabular form. For
2789 example, the list of inferiors bound to the program space.
2792 (@value{GDBP}) maint info program-spaces
2795 Bound inferiors: ID 1 (process 21561)
2799 Here we can see that no inferior is running the program @code{hello},
2800 while @code{process 21561} is running the program @code{goodbye}. On
2801 some targets, it is possible that multiple inferiors are bound to the
2802 same program space. The most common example is that of debugging both
2803 the parent and child processes of a @code{vfork} call. For example,
2806 (@value{GDBP}) maint info program-spaces
2809 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2812 Here, both inferior 2 and inferior 1 are running in the same program
2813 space as a result of inferior 1 having executed a @code{vfork} call.
2817 @section Debugging Programs with Multiple Threads
2819 @cindex threads of execution
2820 @cindex multiple threads
2821 @cindex switching threads
2822 In some operating systems, such as HP-UX and Solaris, a single program
2823 may have more than one @dfn{thread} of execution. The precise semantics
2824 of threads differ from one operating system to another, but in general
2825 the threads of a single program are akin to multiple processes---except
2826 that they share one address space (that is, they can all examine and
2827 modify the same variables). On the other hand, each thread has its own
2828 registers and execution stack, and perhaps private memory.
2830 @value{GDBN} provides these facilities for debugging multi-thread
2834 @item automatic notification of new threads
2835 @item @samp{thread @var{threadno}}, a command to switch among threads
2836 @item @samp{info threads}, a command to inquire about existing threads
2837 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2838 a command to apply a command to a list of threads
2839 @item thread-specific breakpoints
2840 @item @samp{set print thread-events}, which controls printing of
2841 messages on thread start and exit.
2842 @item @samp{set libthread-db-search-path @var{path}}, which lets
2843 the user specify which @code{libthread_db} to use if the default choice
2844 isn't compatible with the program.
2848 @emph{Warning:} These facilities are not yet available on every
2849 @value{GDBN} configuration where the operating system supports threads.
2850 If your @value{GDBN} does not support threads, these commands have no
2851 effect. For example, a system without thread support shows no output
2852 from @samp{info threads}, and always rejects the @code{thread} command,
2856 (@value{GDBP}) info threads
2857 (@value{GDBP}) thread 1
2858 Thread ID 1 not known. Use the "info threads" command to
2859 see the IDs of currently known threads.
2861 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2862 @c doesn't support threads"?
2865 @cindex focus of debugging
2866 @cindex current thread
2867 The @value{GDBN} thread debugging facility allows you to observe all
2868 threads while your program runs---but whenever @value{GDBN} takes
2869 control, one thread in particular is always the focus of debugging.
2870 This thread is called the @dfn{current thread}. Debugging commands show
2871 program information from the perspective of the current thread.
2873 @cindex @code{New} @var{systag} message
2874 @cindex thread identifier (system)
2875 @c FIXME-implementors!! It would be more helpful if the [New...] message
2876 @c included GDB's numeric thread handle, so you could just go to that
2877 @c thread without first checking `info threads'.
2878 Whenever @value{GDBN} detects a new thread in your program, it displays
2879 the target system's identification for the thread with a message in the
2880 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
2881 whose form varies depending on the particular system. For example, on
2882 @sc{gnu}/Linux, you might see
2885 [New Thread 0x41e02940 (LWP 25582)]
2889 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2890 the @var{systag} is simply something like @samp{process 368}, with no
2893 @c FIXME!! (1) Does the [New...] message appear even for the very first
2894 @c thread of a program, or does it only appear for the
2895 @c second---i.e.@: when it becomes obvious we have a multithread
2897 @c (2) *Is* there necessarily a first thread always? Or do some
2898 @c multithread systems permit starting a program with multiple
2899 @c threads ab initio?
2901 @cindex thread number
2902 @cindex thread identifier (GDB)
2903 For debugging purposes, @value{GDBN} associates its own thread
2904 number---always a single integer---with each thread in your program.
2907 @kindex info threads
2908 @item info threads @r{[}@var{id}@dots{}@r{]}
2909 Display a summary of all threads currently in your program. Optional
2910 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2911 means to print information only about the specified thread or threads.
2912 @value{GDBN} displays for each thread (in this order):
2916 the thread number assigned by @value{GDBN}
2919 the target system's thread identifier (@var{systag})
2922 the thread's name, if one is known. A thread can either be named by
2923 the user (see @code{thread name}, below), or, in some cases, by the
2927 the current stack frame summary for that thread
2931 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2932 indicates the current thread.
2936 @c end table here to get a little more width for example
2939 (@value{GDBP}) info threads
2941 3 process 35 thread 27 0x34e5 in sigpause ()
2942 2 process 35 thread 23 0x34e5 in sigpause ()
2943 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2947 On Solaris, you can display more information about user threads with a
2948 Solaris-specific command:
2951 @item maint info sol-threads
2952 @kindex maint info sol-threads
2953 @cindex thread info (Solaris)
2954 Display info on Solaris user threads.
2958 @kindex thread @var{threadno}
2959 @item thread @var{threadno}
2960 Make thread number @var{threadno} the current thread. The command
2961 argument @var{threadno} is the internal @value{GDBN} thread number, as
2962 shown in the first field of the @samp{info threads} display.
2963 @value{GDBN} responds by displaying the system identifier of the thread
2964 you selected, and its current stack frame summary:
2967 (@value{GDBP}) thread 2
2968 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2969 #0 some_function (ignore=0x0) at example.c:8
2970 8 printf ("hello\n");
2974 As with the @samp{[New @dots{}]} message, the form of the text after
2975 @samp{Switching to} depends on your system's conventions for identifying
2978 @vindex $_thread@r{, convenience variable}
2979 The debugger convenience variable @samp{$_thread} contains the number
2980 of the current thread. You may find this useful in writing breakpoint
2981 conditional expressions, command scripts, and so forth. See
2982 @xref{Convenience Vars,, Convenience Variables}, for general
2983 information on convenience variables.
2985 @kindex thread apply
2986 @cindex apply command to several threads
2987 @item thread apply [@var{threadno} | all [-ascending]] @var{command}
2988 The @code{thread apply} command allows you to apply the named
2989 @var{command} to one or more threads. Specify the numbers of the
2990 threads that you want affected with the command argument
2991 @var{threadno}. It can be a single thread number, one of the numbers
2992 shown in the first field of the @samp{info threads} display; or it
2993 could be a range of thread numbers, as in @code{2-4}. To apply
2994 a command to all threads in descending order, type @kbd{thread apply all
2995 @var{command}}. To apply a command to all threads in ascending order,
2996 type @kbd{thread apply all -ascending @var{command}}.
3000 @cindex name a thread
3001 @item thread name [@var{name}]
3002 This command assigns a name to the current thread. If no argument is
3003 given, any existing user-specified name is removed. The thread name
3004 appears in the @samp{info threads} display.
3006 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3007 determine the name of the thread as given by the OS. On these
3008 systems, a name specified with @samp{thread name} will override the
3009 system-give name, and removing the user-specified name will cause
3010 @value{GDBN} to once again display the system-specified name.
3013 @cindex search for a thread
3014 @item thread find [@var{regexp}]
3015 Search for and display thread ids whose name or @var{systag}
3016 matches the supplied regular expression.
3018 As well as being the complement to the @samp{thread name} command,
3019 this command also allows you to identify a thread by its target
3020 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3024 (@value{GDBN}) thread find 26688
3025 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3026 (@value{GDBN}) info thread 4
3028 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3031 @kindex set print thread-events
3032 @cindex print messages on thread start and exit
3033 @item set print thread-events
3034 @itemx set print thread-events on
3035 @itemx set print thread-events off
3036 The @code{set print thread-events} command allows you to enable or
3037 disable printing of messages when @value{GDBN} notices that new threads have
3038 started or that threads have exited. By default, these messages will
3039 be printed if detection of these events is supported by the target.
3040 Note that these messages cannot be disabled on all targets.
3042 @kindex show print thread-events
3043 @item show print thread-events
3044 Show whether messages will be printed when @value{GDBN} detects that threads
3045 have started and exited.
3048 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3049 more information about how @value{GDBN} behaves when you stop and start
3050 programs with multiple threads.
3052 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3053 watchpoints in programs with multiple threads.
3055 @anchor{set libthread-db-search-path}
3057 @kindex set libthread-db-search-path
3058 @cindex search path for @code{libthread_db}
3059 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3060 If this variable is set, @var{path} is a colon-separated list of
3061 directories @value{GDBN} will use to search for @code{libthread_db}.
3062 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3063 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3064 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3067 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3068 @code{libthread_db} library to obtain information about threads in the
3069 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3070 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3071 specific thread debugging library loading is enabled
3072 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3074 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3075 refers to the default system directories that are
3076 normally searched for loading shared libraries. The @samp{$sdir} entry
3077 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3078 (@pxref{libthread_db.so.1 file}).
3080 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3081 refers to the directory from which @code{libpthread}
3082 was loaded in the inferior process.
3084 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3085 @value{GDBN} attempts to initialize it with the current inferior process.
3086 If this initialization fails (which could happen because of a version
3087 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3088 will unload @code{libthread_db}, and continue with the next directory.
3089 If none of @code{libthread_db} libraries initialize successfully,
3090 @value{GDBN} will issue a warning and thread debugging will be disabled.
3092 Setting @code{libthread-db-search-path} is currently implemented
3093 only on some platforms.
3095 @kindex show libthread-db-search-path
3096 @item show libthread-db-search-path
3097 Display current libthread_db search path.
3099 @kindex set debug libthread-db
3100 @kindex show debug libthread-db
3101 @cindex debugging @code{libthread_db}
3102 @item set debug libthread-db
3103 @itemx show debug libthread-db
3104 Turns on or off display of @code{libthread_db}-related events.
3105 Use @code{1} to enable, @code{0} to disable.
3109 @section Debugging Forks
3111 @cindex fork, debugging programs which call
3112 @cindex multiple processes
3113 @cindex processes, multiple
3114 On most systems, @value{GDBN} has no special support for debugging
3115 programs which create additional processes using the @code{fork}
3116 function. When a program forks, @value{GDBN} will continue to debug the
3117 parent process and the child process will run unimpeded. If you have
3118 set a breakpoint in any code which the child then executes, the child
3119 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3120 will cause it to terminate.
3122 However, if you want to debug the child process there is a workaround
3123 which isn't too painful. Put a call to @code{sleep} in the code which
3124 the child process executes after the fork. It may be useful to sleep
3125 only if a certain environment variable is set, or a certain file exists,
3126 so that the delay need not occur when you don't want to run @value{GDBN}
3127 on the child. While the child is sleeping, use the @code{ps} program to
3128 get its process ID. Then tell @value{GDBN} (a new invocation of
3129 @value{GDBN} if you are also debugging the parent process) to attach to
3130 the child process (@pxref{Attach}). From that point on you can debug
3131 the child process just like any other process which you attached to.
3133 On some systems, @value{GDBN} provides support for debugging programs that
3134 create additional processes using the @code{fork} or @code{vfork} functions.
3135 Currently, the only platforms with this feature are HP-UX (11.x and later
3136 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
3138 The fork debugging commands are supported in both native mode and when
3139 connected to @code{gdbserver} using @kbd{target extended-remote}.
3141 By default, when a program forks, @value{GDBN} will continue to debug
3142 the parent process and the child process will run unimpeded.
3144 If you want to follow the child process instead of the parent process,
3145 use the command @w{@code{set follow-fork-mode}}.
3148 @kindex set follow-fork-mode
3149 @item set follow-fork-mode @var{mode}
3150 Set the debugger response to a program call of @code{fork} or
3151 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3152 process. The @var{mode} argument can be:
3156 The original process is debugged after a fork. The child process runs
3157 unimpeded. This is the default.
3160 The new process is debugged after a fork. The parent process runs
3165 @kindex show follow-fork-mode
3166 @item show follow-fork-mode
3167 Display the current debugger response to a @code{fork} or @code{vfork} call.
3170 @cindex debugging multiple processes
3171 On Linux, if you want to debug both the parent and child processes, use the
3172 command @w{@code{set detach-on-fork}}.
3175 @kindex set detach-on-fork
3176 @item set detach-on-fork @var{mode}
3177 Tells gdb whether to detach one of the processes after a fork, or
3178 retain debugger control over them both.
3182 The child process (or parent process, depending on the value of
3183 @code{follow-fork-mode}) will be detached and allowed to run
3184 independently. This is the default.
3187 Both processes will be held under the control of @value{GDBN}.
3188 One process (child or parent, depending on the value of
3189 @code{follow-fork-mode}) is debugged as usual, while the other
3194 @kindex show detach-on-fork
3195 @item show detach-on-fork
3196 Show whether detach-on-fork mode is on/off.
3199 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3200 will retain control of all forked processes (including nested forks).
3201 You can list the forked processes under the control of @value{GDBN} by
3202 using the @w{@code{info inferiors}} command, and switch from one fork
3203 to another by using the @code{inferior} command (@pxref{Inferiors and
3204 Programs, ,Debugging Multiple Inferiors and Programs}).
3206 To quit debugging one of the forked processes, you can either detach
3207 from it by using the @w{@code{detach inferiors}} command (allowing it
3208 to run independently), or kill it using the @w{@code{kill inferiors}}
3209 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3212 If you ask to debug a child process and a @code{vfork} is followed by an
3213 @code{exec}, @value{GDBN} executes the new target up to the first
3214 breakpoint in the new target. If you have a breakpoint set on
3215 @code{main} in your original program, the breakpoint will also be set on
3216 the child process's @code{main}.
3218 On some systems, when a child process is spawned by @code{vfork}, you
3219 cannot debug the child or parent until an @code{exec} call completes.
3221 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3222 call executes, the new target restarts. To restart the parent
3223 process, use the @code{file} command with the parent executable name
3224 as its argument. By default, after an @code{exec} call executes,
3225 @value{GDBN} discards the symbols of the previous executable image.
3226 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3230 @kindex set follow-exec-mode
3231 @item set follow-exec-mode @var{mode}
3233 Set debugger response to a program call of @code{exec}. An
3234 @code{exec} call replaces the program image of a process.
3236 @code{follow-exec-mode} can be:
3240 @value{GDBN} creates a new inferior and rebinds the process to this
3241 new inferior. The program the process was running before the
3242 @code{exec} call can be restarted afterwards by restarting the
3248 (@value{GDBP}) info inferiors
3250 Id Description Executable
3253 process 12020 is executing new program: prog2
3254 Program exited normally.
3255 (@value{GDBP}) info inferiors
3256 Id Description Executable
3262 @value{GDBN} keeps the process bound to the same inferior. The new
3263 executable image replaces the previous executable loaded in the
3264 inferior. Restarting the inferior after the @code{exec} call, with
3265 e.g., the @code{run} command, restarts the executable the process was
3266 running after the @code{exec} call. This is the default mode.
3271 (@value{GDBP}) info inferiors
3272 Id Description Executable
3275 process 12020 is executing new program: prog2
3276 Program exited normally.
3277 (@value{GDBP}) info inferiors
3278 Id Description Executable
3285 You can use the @code{catch} command to make @value{GDBN} stop whenever
3286 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3287 Catchpoints, ,Setting Catchpoints}.
3289 @node Checkpoint/Restart
3290 @section Setting a @emph{Bookmark} to Return to Later
3295 @cindex snapshot of a process
3296 @cindex rewind program state
3298 On certain operating systems@footnote{Currently, only
3299 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3300 program's state, called a @dfn{checkpoint}, and come back to it
3303 Returning to a checkpoint effectively undoes everything that has
3304 happened in the program since the @code{checkpoint} was saved. This
3305 includes changes in memory, registers, and even (within some limits)
3306 system state. Effectively, it is like going back in time to the
3307 moment when the checkpoint was saved.
3309 Thus, if you're stepping thru a program and you think you're
3310 getting close to the point where things go wrong, you can save
3311 a checkpoint. Then, if you accidentally go too far and miss
3312 the critical statement, instead of having to restart your program
3313 from the beginning, you can just go back to the checkpoint and
3314 start again from there.
3316 This can be especially useful if it takes a lot of time or
3317 steps to reach the point where you think the bug occurs.
3319 To use the @code{checkpoint}/@code{restart} method of debugging:
3324 Save a snapshot of the debugged program's current execution state.
3325 The @code{checkpoint} command takes no arguments, but each checkpoint
3326 is assigned a small integer id, similar to a breakpoint id.
3328 @kindex info checkpoints
3329 @item info checkpoints
3330 List the checkpoints that have been saved in the current debugging
3331 session. For each checkpoint, the following information will be
3338 @item Source line, or label
3341 @kindex restart @var{checkpoint-id}
3342 @item restart @var{checkpoint-id}
3343 Restore the program state that was saved as checkpoint number
3344 @var{checkpoint-id}. All program variables, registers, stack frames
3345 etc.@: will be returned to the values that they had when the checkpoint
3346 was saved. In essence, gdb will ``wind back the clock'' to the point
3347 in time when the checkpoint was saved.
3349 Note that breakpoints, @value{GDBN} variables, command history etc.
3350 are not affected by restoring a checkpoint. In general, a checkpoint
3351 only restores things that reside in the program being debugged, not in
3354 @kindex delete checkpoint @var{checkpoint-id}
3355 @item delete checkpoint @var{checkpoint-id}
3356 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3360 Returning to a previously saved checkpoint will restore the user state
3361 of the program being debugged, plus a significant subset of the system
3362 (OS) state, including file pointers. It won't ``un-write'' data from
3363 a file, but it will rewind the file pointer to the previous location,
3364 so that the previously written data can be overwritten. For files
3365 opened in read mode, the pointer will also be restored so that the
3366 previously read data can be read again.
3368 Of course, characters that have been sent to a printer (or other
3369 external device) cannot be ``snatched back'', and characters received
3370 from eg.@: a serial device can be removed from internal program buffers,
3371 but they cannot be ``pushed back'' into the serial pipeline, ready to
3372 be received again. Similarly, the actual contents of files that have
3373 been changed cannot be restored (at this time).
3375 However, within those constraints, you actually can ``rewind'' your
3376 program to a previously saved point in time, and begin debugging it
3377 again --- and you can change the course of events so as to debug a
3378 different execution path this time.
3380 @cindex checkpoints and process id
3381 Finally, there is one bit of internal program state that will be
3382 different when you return to a checkpoint --- the program's process
3383 id. Each checkpoint will have a unique process id (or @var{pid}),
3384 and each will be different from the program's original @var{pid}.
3385 If your program has saved a local copy of its process id, this could
3386 potentially pose a problem.
3388 @subsection A Non-obvious Benefit of Using Checkpoints
3390 On some systems such as @sc{gnu}/Linux, address space randomization
3391 is performed on new processes for security reasons. This makes it
3392 difficult or impossible to set a breakpoint, or watchpoint, on an
3393 absolute address if you have to restart the program, since the
3394 absolute location of a symbol will change from one execution to the
3397 A checkpoint, however, is an @emph{identical} copy of a process.
3398 Therefore if you create a checkpoint at (eg.@:) the start of main,
3399 and simply return to that checkpoint instead of restarting the
3400 process, you can avoid the effects of address randomization and
3401 your symbols will all stay in the same place.
3404 @chapter Stopping and Continuing
3406 The principal purposes of using a debugger are so that you can stop your
3407 program before it terminates; or so that, if your program runs into
3408 trouble, you can investigate and find out why.
3410 Inside @value{GDBN}, your program may stop for any of several reasons,
3411 such as a signal, a breakpoint, or reaching a new line after a
3412 @value{GDBN} command such as @code{step}. You may then examine and
3413 change variables, set new breakpoints or remove old ones, and then
3414 continue execution. Usually, the messages shown by @value{GDBN} provide
3415 ample explanation of the status of your program---but you can also
3416 explicitly request this information at any time.
3419 @kindex info program
3421 Display information about the status of your program: whether it is
3422 running or not, what process it is, and why it stopped.
3426 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3427 * Continuing and Stepping:: Resuming execution
3428 * Skipping Over Functions and Files::
3429 Skipping over functions and files
3431 * Thread Stops:: Stopping and starting multi-thread programs
3435 @section Breakpoints, Watchpoints, and Catchpoints
3438 A @dfn{breakpoint} makes your program stop whenever a certain point in
3439 the program is reached. For each breakpoint, you can add conditions to
3440 control in finer detail whether your program stops. You can set
3441 breakpoints with the @code{break} command and its variants (@pxref{Set
3442 Breaks, ,Setting Breakpoints}), to specify the place where your program
3443 should stop by line number, function name or exact address in the
3446 On some systems, you can set breakpoints in shared libraries before
3447 the executable is run. There is a minor limitation on HP-UX systems:
3448 you must wait until the executable is run in order to set breakpoints
3449 in shared library routines that are not called directly by the program
3450 (for example, routines that are arguments in a @code{pthread_create}
3454 @cindex data breakpoints
3455 @cindex memory tracing
3456 @cindex breakpoint on memory address
3457 @cindex breakpoint on variable modification
3458 A @dfn{watchpoint} is a special breakpoint that stops your program
3459 when the value of an expression changes. The expression may be a value
3460 of a variable, or it could involve values of one or more variables
3461 combined by operators, such as @samp{a + b}. This is sometimes called
3462 @dfn{data breakpoints}. You must use a different command to set
3463 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3464 from that, you can manage a watchpoint like any other breakpoint: you
3465 enable, disable, and delete both breakpoints and watchpoints using the
3468 You can arrange to have values from your program displayed automatically
3469 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3473 @cindex breakpoint on events
3474 A @dfn{catchpoint} is another special breakpoint that stops your program
3475 when a certain kind of event occurs, such as the throwing of a C@t{++}
3476 exception or the loading of a library. As with watchpoints, you use a
3477 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3478 Catchpoints}), but aside from that, you can manage a catchpoint like any
3479 other breakpoint. (To stop when your program receives a signal, use the
3480 @code{handle} command; see @ref{Signals, ,Signals}.)
3482 @cindex breakpoint numbers
3483 @cindex numbers for breakpoints
3484 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3485 catchpoint when you create it; these numbers are successive integers
3486 starting with one. In many of the commands for controlling various
3487 features of breakpoints you use the breakpoint number to say which
3488 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3489 @dfn{disabled}; if disabled, it has no effect on your program until you
3492 @cindex breakpoint ranges
3493 @cindex ranges of breakpoints
3494 Some @value{GDBN} commands accept a range of breakpoints on which to
3495 operate. A breakpoint range is either a single breakpoint number, like
3496 @samp{5}, or two such numbers, in increasing order, separated by a
3497 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3498 all breakpoints in that range are operated on.
3501 * Set Breaks:: Setting breakpoints
3502 * Set Watchpoints:: Setting watchpoints
3503 * Set Catchpoints:: Setting catchpoints
3504 * Delete Breaks:: Deleting breakpoints
3505 * Disabling:: Disabling breakpoints
3506 * Conditions:: Break conditions
3507 * Break Commands:: Breakpoint command lists
3508 * Dynamic Printf:: Dynamic printf
3509 * Save Breakpoints:: How to save breakpoints in a file
3510 * Static Probe Points:: Listing static probe points
3511 * Error in Breakpoints:: ``Cannot insert breakpoints''
3512 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3516 @subsection Setting Breakpoints
3518 @c FIXME LMB what does GDB do if no code on line of breakpt?
3519 @c consider in particular declaration with/without initialization.
3521 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3524 @kindex b @r{(@code{break})}
3525 @vindex $bpnum@r{, convenience variable}
3526 @cindex latest breakpoint
3527 Breakpoints are set with the @code{break} command (abbreviated
3528 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3529 number of the breakpoint you've set most recently; see @ref{Convenience
3530 Vars,, Convenience Variables}, for a discussion of what you can do with
3531 convenience variables.
3534 @item break @var{location}
3535 Set a breakpoint at the given @var{location}, which can specify a
3536 function name, a line number, or an address of an instruction.
3537 (@xref{Specify Location}, for a list of all the possible ways to
3538 specify a @var{location}.) The breakpoint will stop your program just
3539 before it executes any of the code in the specified @var{location}.
3541 When using source languages that permit overloading of symbols, such as
3542 C@t{++}, a function name may refer to more than one possible place to break.
3543 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3546 It is also possible to insert a breakpoint that will stop the program
3547 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3548 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3551 When called without any arguments, @code{break} sets a breakpoint at
3552 the next instruction to be executed in the selected stack frame
3553 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3554 innermost, this makes your program stop as soon as control
3555 returns to that frame. This is similar to the effect of a
3556 @code{finish} command in the frame inside the selected frame---except
3557 that @code{finish} does not leave an active breakpoint. If you use
3558 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3559 the next time it reaches the current location; this may be useful
3562 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3563 least one instruction has been executed. If it did not do this, you
3564 would be unable to proceed past a breakpoint without first disabling the
3565 breakpoint. This rule applies whether or not the breakpoint already
3566 existed when your program stopped.
3568 @item break @dots{} if @var{cond}
3569 Set a breakpoint with condition @var{cond}; evaluate the expression
3570 @var{cond} each time the breakpoint is reached, and stop only if the
3571 value is nonzero---that is, if @var{cond} evaluates as true.
3572 @samp{@dots{}} stands for one of the possible arguments described
3573 above (or no argument) specifying where to break. @xref{Conditions,
3574 ,Break Conditions}, for more information on breakpoint conditions.
3577 @item tbreak @var{args}
3578 Set a breakpoint enabled only for one stop. The @var{args} are the
3579 same as for the @code{break} command, and the breakpoint is set in the same
3580 way, but the breakpoint is automatically deleted after the first time your
3581 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3584 @cindex hardware breakpoints
3585 @item hbreak @var{args}
3586 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
3587 @code{break} command and the breakpoint is set in the same way, but the
3588 breakpoint requires hardware support and some target hardware may not
3589 have this support. The main purpose of this is EPROM/ROM code
3590 debugging, so you can set a breakpoint at an instruction without
3591 changing the instruction. This can be used with the new trap-generation
3592 provided by SPARClite DSU and most x86-based targets. These targets
3593 will generate traps when a program accesses some data or instruction
3594 address that is assigned to the debug registers. However the hardware
3595 breakpoint registers can take a limited number of breakpoints. For
3596 example, on the DSU, only two data breakpoints can be set at a time, and
3597 @value{GDBN} will reject this command if more than two are used. Delete
3598 or disable unused hardware breakpoints before setting new ones
3599 (@pxref{Disabling, ,Disabling Breakpoints}).
3600 @xref{Conditions, ,Break Conditions}.
3601 For remote targets, you can restrict the number of hardware
3602 breakpoints @value{GDBN} will use, see @ref{set remote
3603 hardware-breakpoint-limit}.
3606 @item thbreak @var{args}
3607 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
3608 are the same as for the @code{hbreak} command and the breakpoint is set in
3609 the same way. However, like the @code{tbreak} command,
3610 the breakpoint is automatically deleted after the
3611 first time your program stops there. Also, like the @code{hbreak}
3612 command, the breakpoint requires hardware support and some target hardware
3613 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3614 See also @ref{Conditions, ,Break Conditions}.
3617 @cindex regular expression
3618 @cindex breakpoints at functions matching a regexp
3619 @cindex set breakpoints in many functions
3620 @item rbreak @var{regex}
3621 Set breakpoints on all functions matching the regular expression
3622 @var{regex}. This command sets an unconditional breakpoint on all
3623 matches, printing a list of all breakpoints it set. Once these
3624 breakpoints are set, they are treated just like the breakpoints set with
3625 the @code{break} command. You can delete them, disable them, or make
3626 them conditional the same way as any other breakpoint.
3628 The syntax of the regular expression is the standard one used with tools
3629 like @file{grep}. Note that this is different from the syntax used by
3630 shells, so for instance @code{foo*} matches all functions that include
3631 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3632 @code{.*} leading and trailing the regular expression you supply, so to
3633 match only functions that begin with @code{foo}, use @code{^foo}.
3635 @cindex non-member C@t{++} functions, set breakpoint in
3636 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3637 breakpoints on overloaded functions that are not members of any special
3640 @cindex set breakpoints on all functions
3641 The @code{rbreak} command can be used to set breakpoints in
3642 @strong{all} the functions in a program, like this:
3645 (@value{GDBP}) rbreak .
3648 @item rbreak @var{file}:@var{regex}
3649 If @code{rbreak} is called with a filename qualification, it limits
3650 the search for functions matching the given regular expression to the
3651 specified @var{file}. This can be used, for example, to set breakpoints on
3652 every function in a given file:
3655 (@value{GDBP}) rbreak file.c:.
3658 The colon separating the filename qualifier from the regex may
3659 optionally be surrounded by spaces.
3661 @kindex info breakpoints
3662 @cindex @code{$_} and @code{info breakpoints}
3663 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3664 @itemx info break @r{[}@var{n}@dots{}@r{]}
3665 Print a table of all breakpoints, watchpoints, and catchpoints set and
3666 not deleted. Optional argument @var{n} means print information only
3667 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3668 For each breakpoint, following columns are printed:
3671 @item Breakpoint Numbers
3673 Breakpoint, watchpoint, or catchpoint.
3675 Whether the breakpoint is marked to be disabled or deleted when hit.
3676 @item Enabled or Disabled
3677 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3678 that are not enabled.
3680 Where the breakpoint is in your program, as a memory address. For a
3681 pending breakpoint whose address is not yet known, this field will
3682 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3683 library that has the symbol or line referred by breakpoint is loaded.
3684 See below for details. A breakpoint with several locations will
3685 have @samp{<MULTIPLE>} in this field---see below for details.
3687 Where the breakpoint is in the source for your program, as a file and
3688 line number. For a pending breakpoint, the original string passed to
3689 the breakpoint command will be listed as it cannot be resolved until
3690 the appropriate shared library is loaded in the future.
3694 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3695 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3696 @value{GDBN} on the host's side. If it is ``target'', then the condition
3697 is evaluated by the target. The @code{info break} command shows
3698 the condition on the line following the affected breakpoint, together with
3699 its condition evaluation mode in between parentheses.
3701 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3702 allowed to have a condition specified for it. The condition is not parsed for
3703 validity until a shared library is loaded that allows the pending
3704 breakpoint to resolve to a valid location.
3707 @code{info break} with a breakpoint
3708 number @var{n} as argument lists only that breakpoint. The
3709 convenience variable @code{$_} and the default examining-address for
3710 the @code{x} command are set to the address of the last breakpoint
3711 listed (@pxref{Memory, ,Examining Memory}).
3714 @code{info break} displays a count of the number of times the breakpoint
3715 has been hit. This is especially useful in conjunction with the
3716 @code{ignore} command. You can ignore a large number of breakpoint
3717 hits, look at the breakpoint info to see how many times the breakpoint
3718 was hit, and then run again, ignoring one less than that number. This
3719 will get you quickly to the last hit of that breakpoint.
3722 For a breakpoints with an enable count (xref) greater than 1,
3723 @code{info break} also displays that count.
3727 @value{GDBN} allows you to set any number of breakpoints at the same place in
3728 your program. There is nothing silly or meaningless about this. When
3729 the breakpoints are conditional, this is even useful
3730 (@pxref{Conditions, ,Break Conditions}).
3732 @cindex multiple locations, breakpoints
3733 @cindex breakpoints, multiple locations
3734 It is possible that a breakpoint corresponds to several locations
3735 in your program. Examples of this situation are:
3739 Multiple functions in the program may have the same name.
3742 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3743 instances of the function body, used in different cases.
3746 For a C@t{++} template function, a given line in the function can
3747 correspond to any number of instantiations.
3750 For an inlined function, a given source line can correspond to
3751 several places where that function is inlined.
3754 In all those cases, @value{GDBN} will insert a breakpoint at all
3755 the relevant locations.
3757 A breakpoint with multiple locations is displayed in the breakpoint
3758 table using several rows---one header row, followed by one row for
3759 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3760 address column. The rows for individual locations contain the actual
3761 addresses for locations, and show the functions to which those
3762 locations belong. The number column for a location is of the form
3763 @var{breakpoint-number}.@var{location-number}.
3768 Num Type Disp Enb Address What
3769 1 breakpoint keep y <MULTIPLE>
3771 breakpoint already hit 1 time
3772 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3773 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3776 Each location can be individually enabled or disabled by passing
3777 @var{breakpoint-number}.@var{location-number} as argument to the
3778 @code{enable} and @code{disable} commands. Note that you cannot
3779 delete the individual locations from the list, you can only delete the
3780 entire list of locations that belong to their parent breakpoint (with
3781 the @kbd{delete @var{num}} command, where @var{num} is the number of
3782 the parent breakpoint, 1 in the above example). Disabling or enabling
3783 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3784 that belong to that breakpoint.
3786 @cindex pending breakpoints
3787 It's quite common to have a breakpoint inside a shared library.
3788 Shared libraries can be loaded and unloaded explicitly,
3789 and possibly repeatedly, as the program is executed. To support
3790 this use case, @value{GDBN} updates breakpoint locations whenever
3791 any shared library is loaded or unloaded. Typically, you would
3792 set a breakpoint in a shared library at the beginning of your
3793 debugging session, when the library is not loaded, and when the
3794 symbols from the library are not available. When you try to set
3795 breakpoint, @value{GDBN} will ask you if you want to set
3796 a so called @dfn{pending breakpoint}---breakpoint whose address
3797 is not yet resolved.
3799 After the program is run, whenever a new shared library is loaded,
3800 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3801 shared library contains the symbol or line referred to by some
3802 pending breakpoint, that breakpoint is resolved and becomes an
3803 ordinary breakpoint. When a library is unloaded, all breakpoints
3804 that refer to its symbols or source lines become pending again.
3806 This logic works for breakpoints with multiple locations, too. For
3807 example, if you have a breakpoint in a C@t{++} template function, and
3808 a newly loaded shared library has an instantiation of that template,
3809 a new location is added to the list of locations for the breakpoint.
3811 Except for having unresolved address, pending breakpoints do not
3812 differ from regular breakpoints. You can set conditions or commands,
3813 enable and disable them and perform other breakpoint operations.
3815 @value{GDBN} provides some additional commands for controlling what
3816 happens when the @samp{break} command cannot resolve breakpoint
3817 address specification to an address:
3819 @kindex set breakpoint pending
3820 @kindex show breakpoint pending
3822 @item set breakpoint pending auto
3823 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3824 location, it queries you whether a pending breakpoint should be created.
3826 @item set breakpoint pending on
3827 This indicates that an unrecognized breakpoint location should automatically
3828 result in a pending breakpoint being created.
3830 @item set breakpoint pending off
3831 This indicates that pending breakpoints are not to be created. Any
3832 unrecognized breakpoint location results in an error. This setting does
3833 not affect any pending breakpoints previously created.
3835 @item show breakpoint pending
3836 Show the current behavior setting for creating pending breakpoints.
3839 The settings above only affect the @code{break} command and its
3840 variants. Once breakpoint is set, it will be automatically updated
3841 as shared libraries are loaded and unloaded.
3843 @cindex automatic hardware breakpoints
3844 For some targets, @value{GDBN} can automatically decide if hardware or
3845 software breakpoints should be used, depending on whether the
3846 breakpoint address is read-only or read-write. This applies to
3847 breakpoints set with the @code{break} command as well as to internal
3848 breakpoints set by commands like @code{next} and @code{finish}. For
3849 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3852 You can control this automatic behaviour with the following commands::
3854 @kindex set breakpoint auto-hw
3855 @kindex show breakpoint auto-hw
3857 @item set breakpoint auto-hw on
3858 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3859 will try to use the target memory map to decide if software or hardware
3860 breakpoint must be used.
3862 @item set breakpoint auto-hw off
3863 This indicates @value{GDBN} should not automatically select breakpoint
3864 type. If the target provides a memory map, @value{GDBN} will warn when
3865 trying to set software breakpoint at a read-only address.
3868 @value{GDBN} normally implements breakpoints by replacing the program code
3869 at the breakpoint address with a special instruction, which, when
3870 executed, given control to the debugger. By default, the program
3871 code is so modified only when the program is resumed. As soon as
3872 the program stops, @value{GDBN} restores the original instructions. This
3873 behaviour guards against leaving breakpoints inserted in the
3874 target should gdb abrubptly disconnect. However, with slow remote
3875 targets, inserting and removing breakpoint can reduce the performance.
3876 This behavior can be controlled with the following commands::
3878 @kindex set breakpoint always-inserted
3879 @kindex show breakpoint always-inserted
3881 @item set breakpoint always-inserted off
3882 All breakpoints, including newly added by the user, are inserted in
3883 the target only when the target is resumed. All breakpoints are
3884 removed from the target when it stops. This is the default mode.
3886 @item set breakpoint always-inserted on
3887 Causes all breakpoints to be inserted in the target at all times. If
3888 the user adds a new breakpoint, or changes an existing breakpoint, the
3889 breakpoints in the target are updated immediately. A breakpoint is
3890 removed from the target only when breakpoint itself is deleted.
3893 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3894 when a breakpoint breaks. If the condition is true, then the process being
3895 debugged stops, otherwise the process is resumed.
3897 If the target supports evaluating conditions on its end, @value{GDBN} may
3898 download the breakpoint, together with its conditions, to it.
3900 This feature can be controlled via the following commands:
3902 @kindex set breakpoint condition-evaluation
3903 @kindex show breakpoint condition-evaluation
3905 @item set breakpoint condition-evaluation host
3906 This option commands @value{GDBN} to evaluate the breakpoint
3907 conditions on the host's side. Unconditional breakpoints are sent to
3908 the target which in turn receives the triggers and reports them back to GDB
3909 for condition evaluation. This is the standard evaluation mode.
3911 @item set breakpoint condition-evaluation target
3912 This option commands @value{GDBN} to download breakpoint conditions
3913 to the target at the moment of their insertion. The target
3914 is responsible for evaluating the conditional expression and reporting
3915 breakpoint stop events back to @value{GDBN} whenever the condition
3916 is true. Due to limitations of target-side evaluation, some conditions
3917 cannot be evaluated there, e.g., conditions that depend on local data
3918 that is only known to the host. Examples include
3919 conditional expressions involving convenience variables, complex types
3920 that cannot be handled by the agent expression parser and expressions
3921 that are too long to be sent over to the target, specially when the
3922 target is a remote system. In these cases, the conditions will be
3923 evaluated by @value{GDBN}.
3925 @item set breakpoint condition-evaluation auto
3926 This is the default mode. If the target supports evaluating breakpoint
3927 conditions on its end, @value{GDBN} will download breakpoint conditions to
3928 the target (limitations mentioned previously apply). If the target does
3929 not support breakpoint condition evaluation, then @value{GDBN} will fallback
3930 to evaluating all these conditions on the host's side.
3934 @cindex negative breakpoint numbers
3935 @cindex internal @value{GDBN} breakpoints
3936 @value{GDBN} itself sometimes sets breakpoints in your program for
3937 special purposes, such as proper handling of @code{longjmp} (in C
3938 programs). These internal breakpoints are assigned negative numbers,
3939 starting with @code{-1}; @samp{info breakpoints} does not display them.
3940 You can see these breakpoints with the @value{GDBN} maintenance command
3941 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3944 @node Set Watchpoints
3945 @subsection Setting Watchpoints
3947 @cindex setting watchpoints
3948 You can use a watchpoint to stop execution whenever the value of an
3949 expression changes, without having to predict a particular place where
3950 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3951 The expression may be as simple as the value of a single variable, or
3952 as complex as many variables combined by operators. Examples include:
3956 A reference to the value of a single variable.
3959 An address cast to an appropriate data type. For example,
3960 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3961 address (assuming an @code{int} occupies 4 bytes).
3964 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3965 expression can use any operators valid in the program's native
3966 language (@pxref{Languages}).
3969 You can set a watchpoint on an expression even if the expression can
3970 not be evaluated yet. For instance, you can set a watchpoint on
3971 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3972 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3973 the expression produces a valid value. If the expression becomes
3974 valid in some other way than changing a variable (e.g.@: if the memory
3975 pointed to by @samp{*global_ptr} becomes readable as the result of a
3976 @code{malloc} call), @value{GDBN} may not stop until the next time
3977 the expression changes.
3979 @cindex software watchpoints
3980 @cindex hardware watchpoints
3981 Depending on your system, watchpoints may be implemented in software or
3982 hardware. @value{GDBN} does software watchpointing by single-stepping your
3983 program and testing the variable's value each time, which is hundreds of
3984 times slower than normal execution. (But this may still be worth it, to
3985 catch errors where you have no clue what part of your program is the
3988 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3989 x86-based targets, @value{GDBN} includes support for hardware
3990 watchpoints, which do not slow down the running of your program.
3994 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3995 Set a watchpoint for an expression. @value{GDBN} will break when the
3996 expression @var{expr} is written into by the program and its value
3997 changes. The simplest (and the most popular) use of this command is
3998 to watch the value of a single variable:
4001 (@value{GDBP}) watch foo
4004 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
4005 argument, @value{GDBN} breaks only when the thread identified by
4006 @var{threadnum} changes the value of @var{expr}. If any other threads
4007 change the value of @var{expr}, @value{GDBN} will not break. Note
4008 that watchpoints restricted to a single thread in this way only work
4009 with Hardware Watchpoints.
4011 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4012 (see below). The @code{-location} argument tells @value{GDBN} to
4013 instead watch the memory referred to by @var{expr}. In this case,
4014 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4015 and watch the memory at that address. The type of the result is used
4016 to determine the size of the watched memory. If the expression's
4017 result does not have an address, then @value{GDBN} will print an
4020 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4021 of masked watchpoints, if the current architecture supports this
4022 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4023 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4024 to an address to watch. The mask specifies that some bits of an address
4025 (the bits which are reset in the mask) should be ignored when matching
4026 the address accessed by the inferior against the watchpoint address.
4027 Thus, a masked watchpoint watches many addresses simultaneously---those
4028 addresses whose unmasked bits are identical to the unmasked bits in the
4029 watchpoint address. The @code{mask} argument implies @code{-location}.
4033 (@value{GDBP}) watch foo mask 0xffff00ff
4034 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4038 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
4039 Set a watchpoint that will break when the value of @var{expr} is read
4043 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
4044 Set a watchpoint that will break when @var{expr} is either read from
4045 or written into by the program.
4047 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
4048 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
4049 This command prints a list of watchpoints, using the same format as
4050 @code{info break} (@pxref{Set Breaks}).
4053 If you watch for a change in a numerically entered address you need to
4054 dereference it, as the address itself is just a constant number which will
4055 never change. @value{GDBN} refuses to create a watchpoint that watches
4056 a never-changing value:
4059 (@value{GDBP}) watch 0x600850
4060 Cannot watch constant value 0x600850.
4061 (@value{GDBP}) watch *(int *) 0x600850
4062 Watchpoint 1: *(int *) 6293584
4065 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4066 watchpoints execute very quickly, and the debugger reports a change in
4067 value at the exact instruction where the change occurs. If @value{GDBN}
4068 cannot set a hardware watchpoint, it sets a software watchpoint, which
4069 executes more slowly and reports the change in value at the next
4070 @emph{statement}, not the instruction, after the change occurs.
4072 @cindex use only software watchpoints
4073 You can force @value{GDBN} to use only software watchpoints with the
4074 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4075 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4076 the underlying system supports them. (Note that hardware-assisted
4077 watchpoints that were set @emph{before} setting
4078 @code{can-use-hw-watchpoints} to zero will still use the hardware
4079 mechanism of watching expression values.)
4082 @item set can-use-hw-watchpoints
4083 @kindex set can-use-hw-watchpoints
4084 Set whether or not to use hardware watchpoints.
4086 @item show can-use-hw-watchpoints
4087 @kindex show can-use-hw-watchpoints
4088 Show the current mode of using hardware watchpoints.
4091 For remote targets, you can restrict the number of hardware
4092 watchpoints @value{GDBN} will use, see @ref{set remote
4093 hardware-breakpoint-limit}.
4095 When you issue the @code{watch} command, @value{GDBN} reports
4098 Hardware watchpoint @var{num}: @var{expr}
4102 if it was able to set a hardware watchpoint.
4104 Currently, the @code{awatch} and @code{rwatch} commands can only set
4105 hardware watchpoints, because accesses to data that don't change the
4106 value of the watched expression cannot be detected without examining
4107 every instruction as it is being executed, and @value{GDBN} does not do
4108 that currently. If @value{GDBN} finds that it is unable to set a
4109 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4110 will print a message like this:
4113 Expression cannot be implemented with read/access watchpoint.
4116 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4117 data type of the watched expression is wider than what a hardware
4118 watchpoint on the target machine can handle. For example, some systems
4119 can only watch regions that are up to 4 bytes wide; on such systems you
4120 cannot set hardware watchpoints for an expression that yields a
4121 double-precision floating-point number (which is typically 8 bytes
4122 wide). As a work-around, it might be possible to break the large region
4123 into a series of smaller ones and watch them with separate watchpoints.
4125 If you set too many hardware watchpoints, @value{GDBN} might be unable
4126 to insert all of them when you resume the execution of your program.
4127 Since the precise number of active watchpoints is unknown until such
4128 time as the program is about to be resumed, @value{GDBN} might not be
4129 able to warn you about this when you set the watchpoints, and the
4130 warning will be printed only when the program is resumed:
4133 Hardware watchpoint @var{num}: Could not insert watchpoint
4137 If this happens, delete or disable some of the watchpoints.
4139 Watching complex expressions that reference many variables can also
4140 exhaust the resources available for hardware-assisted watchpoints.
4141 That's because @value{GDBN} needs to watch every variable in the
4142 expression with separately allocated resources.
4144 If you call a function interactively using @code{print} or @code{call},
4145 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4146 kind of breakpoint or the call completes.
4148 @value{GDBN} automatically deletes watchpoints that watch local
4149 (automatic) variables, or expressions that involve such variables, when
4150 they go out of scope, that is, when the execution leaves the block in
4151 which these variables were defined. In particular, when the program
4152 being debugged terminates, @emph{all} local variables go out of scope,
4153 and so only watchpoints that watch global variables remain set. If you
4154 rerun the program, you will need to set all such watchpoints again. One
4155 way of doing that would be to set a code breakpoint at the entry to the
4156 @code{main} function and when it breaks, set all the watchpoints.
4158 @cindex watchpoints and threads
4159 @cindex threads and watchpoints
4160 In multi-threaded programs, watchpoints will detect changes to the
4161 watched expression from every thread.
4164 @emph{Warning:} In multi-threaded programs, software watchpoints
4165 have only limited usefulness. If @value{GDBN} creates a software
4166 watchpoint, it can only watch the value of an expression @emph{in a
4167 single thread}. If you are confident that the expression can only
4168 change due to the current thread's activity (and if you are also
4169 confident that no other thread can become current), then you can use
4170 software watchpoints as usual. However, @value{GDBN} may not notice
4171 when a non-current thread's activity changes the expression. (Hardware
4172 watchpoints, in contrast, watch an expression in all threads.)
4175 @xref{set remote hardware-watchpoint-limit}.
4177 @node Set Catchpoints
4178 @subsection Setting Catchpoints
4179 @cindex catchpoints, setting
4180 @cindex exception handlers
4181 @cindex event handling
4183 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4184 kinds of program events, such as C@t{++} exceptions or the loading of a
4185 shared library. Use the @code{catch} command to set a catchpoint.
4189 @item catch @var{event}
4190 Stop when @var{event} occurs. The @var{event} can be any of the following:
4193 @item throw @r{[}@var{regexp}@r{]}
4194 @itemx rethrow @r{[}@var{regexp}@r{]}
4195 @itemx catch @r{[}@var{regexp}@r{]}
4197 @kindex catch rethrow
4199 @cindex stop on C@t{++} exceptions
4200 The throwing, re-throwing, or catching of a C@t{++} exception.
4202 If @var{regexp} is given, then only exceptions whose type matches the
4203 regular expression will be caught.
4205 @vindex $_exception@r{, convenience variable}
4206 The convenience variable @code{$_exception} is available at an
4207 exception-related catchpoint, on some systems. This holds the
4208 exception being thrown.
4210 There are currently some limitations to C@t{++} exception handling in
4215 The support for these commands is system-dependent. Currently, only
4216 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4220 The regular expression feature and the @code{$_exception} convenience
4221 variable rely on the presence of some SDT probes in @code{libstdc++}.
4222 If these probes are not present, then these features cannot be used.
4223 These probes were first available in the GCC 4.8 release, but whether
4224 or not they are available in your GCC also depends on how it was
4228 The @code{$_exception} convenience variable is only valid at the
4229 instruction at which an exception-related catchpoint is set.
4232 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4233 location in the system library which implements runtime exception
4234 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4235 (@pxref{Selection}) to get to your code.
4238 If you call a function interactively, @value{GDBN} normally returns
4239 control to you when the function has finished executing. If the call
4240 raises an exception, however, the call may bypass the mechanism that
4241 returns control to you and cause your program either to abort or to
4242 simply continue running until it hits a breakpoint, catches a signal
4243 that @value{GDBN} is listening for, or exits. This is the case even if
4244 you set a catchpoint for the exception; catchpoints on exceptions are
4245 disabled within interactive calls. @xref{Calling}, for information on
4246 controlling this with @code{set unwind-on-terminating-exception}.
4249 You cannot raise an exception interactively.
4252 You cannot install an exception handler interactively.
4256 @kindex catch exception
4257 @cindex Ada exception catching
4258 @cindex catch Ada exceptions
4259 An Ada exception being raised. If an exception name is specified
4260 at the end of the command (eg @code{catch exception Program_Error}),
4261 the debugger will stop only when this specific exception is raised.
4262 Otherwise, the debugger stops execution when any Ada exception is raised.
4264 When inserting an exception catchpoint on a user-defined exception whose
4265 name is identical to one of the exceptions defined by the language, the
4266 fully qualified name must be used as the exception name. Otherwise,
4267 @value{GDBN} will assume that it should stop on the pre-defined exception
4268 rather than the user-defined one. For instance, assuming an exception
4269 called @code{Constraint_Error} is defined in package @code{Pck}, then
4270 the command to use to catch such exceptions is @kbd{catch exception
4271 Pck.Constraint_Error}.
4273 @item exception unhandled
4274 @kindex catch exception unhandled
4275 An exception that was raised but is not handled by the program.
4278 @kindex catch assert
4279 A failed Ada assertion.
4283 @cindex break on fork/exec
4284 A call to @code{exec}. This is currently only available for HP-UX
4288 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4289 @kindex catch syscall
4290 @cindex break on a system call.
4291 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4292 syscall is a mechanism for application programs to request a service
4293 from the operating system (OS) or one of the OS system services.
4294 @value{GDBN} can catch some or all of the syscalls issued by the
4295 debuggee, and show the related information for each syscall. If no
4296 argument is specified, calls to and returns from all system calls
4299 @var{name} can be any system call name that is valid for the
4300 underlying OS. Just what syscalls are valid depends on the OS. On
4301 GNU and Unix systems, you can find the full list of valid syscall
4302 names on @file{/usr/include/asm/unistd.h}.
4304 @c For MS-Windows, the syscall names and the corresponding numbers
4305 @c can be found, e.g., on this URL:
4306 @c http://www.metasploit.com/users/opcode/syscalls.html
4307 @c but we don't support Windows syscalls yet.
4309 Normally, @value{GDBN} knows in advance which syscalls are valid for
4310 each OS, so you can use the @value{GDBN} command-line completion
4311 facilities (@pxref{Completion,, command completion}) to list the
4314 You may also specify the system call numerically. A syscall's
4315 number is the value passed to the OS's syscall dispatcher to
4316 identify the requested service. When you specify the syscall by its
4317 name, @value{GDBN} uses its database of syscalls to convert the name
4318 into the corresponding numeric code, but using the number directly
4319 may be useful if @value{GDBN}'s database does not have the complete
4320 list of syscalls on your system (e.g., because @value{GDBN} lags
4321 behind the OS upgrades).
4323 The example below illustrates how this command works if you don't provide
4327 (@value{GDBP}) catch syscall
4328 Catchpoint 1 (syscall)
4330 Starting program: /tmp/catch-syscall
4332 Catchpoint 1 (call to syscall 'close'), \
4333 0xffffe424 in __kernel_vsyscall ()
4337 Catchpoint 1 (returned from syscall 'close'), \
4338 0xffffe424 in __kernel_vsyscall ()
4342 Here is an example of catching a system call by name:
4345 (@value{GDBP}) catch syscall chroot
4346 Catchpoint 1 (syscall 'chroot' [61])
4348 Starting program: /tmp/catch-syscall
4350 Catchpoint 1 (call to syscall 'chroot'), \
4351 0xffffe424 in __kernel_vsyscall ()
4355 Catchpoint 1 (returned from syscall 'chroot'), \
4356 0xffffe424 in __kernel_vsyscall ()
4360 An example of specifying a system call numerically. In the case
4361 below, the syscall number has a corresponding entry in the XML
4362 file, so @value{GDBN} finds its name and prints it:
4365 (@value{GDBP}) catch syscall 252
4366 Catchpoint 1 (syscall(s) 'exit_group')
4368 Starting program: /tmp/catch-syscall
4370 Catchpoint 1 (call to syscall 'exit_group'), \
4371 0xffffe424 in __kernel_vsyscall ()
4375 Program exited normally.
4379 However, there can be situations when there is no corresponding name
4380 in XML file for that syscall number. In this case, @value{GDBN} prints
4381 a warning message saying that it was not able to find the syscall name,
4382 but the catchpoint will be set anyway. See the example below:
4385 (@value{GDBP}) catch syscall 764
4386 warning: The number '764' does not represent a known syscall.
4387 Catchpoint 2 (syscall 764)
4391 If you configure @value{GDBN} using the @samp{--without-expat} option,
4392 it will not be able to display syscall names. Also, if your
4393 architecture does not have an XML file describing its system calls,
4394 you will not be able to see the syscall names. It is important to
4395 notice that these two features are used for accessing the syscall
4396 name database. In either case, you will see a warning like this:
4399 (@value{GDBP}) catch syscall
4400 warning: Could not open "syscalls/i386-linux.xml"
4401 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4402 GDB will not be able to display syscall names.
4403 Catchpoint 1 (syscall)
4407 Of course, the file name will change depending on your architecture and system.
4409 Still using the example above, you can also try to catch a syscall by its
4410 number. In this case, you would see something like:
4413 (@value{GDBP}) catch syscall 252
4414 Catchpoint 1 (syscall(s) 252)
4417 Again, in this case @value{GDBN} would not be able to display syscall's names.
4421 A call to @code{fork}. This is currently only available for HP-UX
4426 A call to @code{vfork}. This is currently only available for HP-UX
4429 @item load @r{[}regexp@r{]}
4430 @itemx unload @r{[}regexp@r{]}
4432 @kindex catch unload
4433 The loading or unloading of a shared library. If @var{regexp} is
4434 given, then the catchpoint will stop only if the regular expression
4435 matches one of the affected libraries.
4437 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4438 @kindex catch signal
4439 The delivery of a signal.
4441 With no arguments, this catchpoint will catch any signal that is not
4442 used internally by @value{GDBN}, specifically, all signals except
4443 @samp{SIGTRAP} and @samp{SIGINT}.
4445 With the argument @samp{all}, all signals, including those used by
4446 @value{GDBN}, will be caught. This argument cannot be used with other
4449 Otherwise, the arguments are a list of signal names as given to
4450 @code{handle} (@pxref{Signals}). Only signals specified in this list
4453 One reason that @code{catch signal} can be more useful than
4454 @code{handle} is that you can attach commands and conditions to the
4457 When a signal is caught by a catchpoint, the signal's @code{stop} and
4458 @code{print} settings, as specified by @code{handle}, are ignored.
4459 However, whether the signal is still delivered to the inferior depends
4460 on the @code{pass} setting; this can be changed in the catchpoint's
4465 @item tcatch @var{event}
4467 Set a catchpoint that is enabled only for one stop. The catchpoint is
4468 automatically deleted after the first time the event is caught.
4472 Use the @code{info break} command to list the current catchpoints.
4476 @subsection Deleting Breakpoints
4478 @cindex clearing breakpoints, watchpoints, catchpoints
4479 @cindex deleting breakpoints, watchpoints, catchpoints
4480 It is often necessary to eliminate a breakpoint, watchpoint, or
4481 catchpoint once it has done its job and you no longer want your program
4482 to stop there. This is called @dfn{deleting} the breakpoint. A
4483 breakpoint that has been deleted no longer exists; it is forgotten.
4485 With the @code{clear} command you can delete breakpoints according to
4486 where they are in your program. With the @code{delete} command you can
4487 delete individual breakpoints, watchpoints, or catchpoints by specifying
4488 their breakpoint numbers.
4490 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4491 automatically ignores breakpoints on the first instruction to be executed
4492 when you continue execution without changing the execution address.
4497 Delete any breakpoints at the next instruction to be executed in the
4498 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4499 the innermost frame is selected, this is a good way to delete a
4500 breakpoint where your program just stopped.
4502 @item clear @var{location}
4503 Delete any breakpoints set at the specified @var{location}.
4504 @xref{Specify Location}, for the various forms of @var{location}; the
4505 most useful ones are listed below:
4508 @item clear @var{function}
4509 @itemx clear @var{filename}:@var{function}
4510 Delete any breakpoints set at entry to the named @var{function}.
4512 @item clear @var{linenum}
4513 @itemx clear @var{filename}:@var{linenum}
4514 Delete any breakpoints set at or within the code of the specified
4515 @var{linenum} of the specified @var{filename}.
4518 @cindex delete breakpoints
4520 @kindex d @r{(@code{delete})}
4521 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4522 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4523 ranges specified as arguments. If no argument is specified, delete all
4524 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4525 confirm off}). You can abbreviate this command as @code{d}.
4529 @subsection Disabling Breakpoints
4531 @cindex enable/disable a breakpoint
4532 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4533 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4534 it had been deleted, but remembers the information on the breakpoint so
4535 that you can @dfn{enable} it again later.
4537 You disable and enable breakpoints, watchpoints, and catchpoints with
4538 the @code{enable} and @code{disable} commands, optionally specifying
4539 one or more breakpoint numbers as arguments. Use @code{info break} to
4540 print a list of all breakpoints, watchpoints, and catchpoints if you
4541 do not know which numbers to use.
4543 Disabling and enabling a breakpoint that has multiple locations
4544 affects all of its locations.
4546 A breakpoint, watchpoint, or catchpoint can have any of several
4547 different states of enablement:
4551 Enabled. The breakpoint stops your program. A breakpoint set
4552 with the @code{break} command starts out in this state.
4554 Disabled. The breakpoint has no effect on your program.
4556 Enabled once. The breakpoint stops your program, but then becomes
4559 Enabled for a count. The breakpoint stops your program for the next
4560 N times, then becomes disabled.
4562 Enabled for deletion. The breakpoint stops your program, but
4563 immediately after it does so it is deleted permanently. A breakpoint
4564 set with the @code{tbreak} command starts out in this state.
4567 You can use the following commands to enable or disable breakpoints,
4568 watchpoints, and catchpoints:
4572 @kindex dis @r{(@code{disable})}
4573 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4574 Disable the specified breakpoints---or all breakpoints, if none are
4575 listed. A disabled breakpoint has no effect but is not forgotten. All
4576 options such as ignore-counts, conditions and commands are remembered in
4577 case the breakpoint is enabled again later. You may abbreviate
4578 @code{disable} as @code{dis}.
4581 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4582 Enable the specified breakpoints (or all defined breakpoints). They
4583 become effective once again in stopping your program.
4585 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4586 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4587 of these breakpoints immediately after stopping your program.
4589 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4590 Enable the specified breakpoints temporarily. @value{GDBN} records
4591 @var{count} with each of the specified breakpoints, and decrements a
4592 breakpoint's count when it is hit. When any count reaches 0,
4593 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4594 count (@pxref{Conditions, ,Break Conditions}), that will be
4595 decremented to 0 before @var{count} is affected.
4597 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4598 Enable the specified breakpoints to work once, then die. @value{GDBN}
4599 deletes any of these breakpoints as soon as your program stops there.
4600 Breakpoints set by the @code{tbreak} command start out in this state.
4603 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4604 @c confusing: tbreak is also initially enabled.
4605 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4606 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4607 subsequently, they become disabled or enabled only when you use one of
4608 the commands above. (The command @code{until} can set and delete a
4609 breakpoint of its own, but it does not change the state of your other
4610 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4614 @subsection Break Conditions
4615 @cindex conditional breakpoints
4616 @cindex breakpoint conditions
4618 @c FIXME what is scope of break condition expr? Context where wanted?
4619 @c in particular for a watchpoint?
4620 The simplest sort of breakpoint breaks every time your program reaches a
4621 specified place. You can also specify a @dfn{condition} for a
4622 breakpoint. A condition is just a Boolean expression in your
4623 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4624 a condition evaluates the expression each time your program reaches it,
4625 and your program stops only if the condition is @emph{true}.
4627 This is the converse of using assertions for program validation; in that
4628 situation, you want to stop when the assertion is violated---that is,
4629 when the condition is false. In C, if you want to test an assertion expressed
4630 by the condition @var{assert}, you should set the condition
4631 @samp{! @var{assert}} on the appropriate breakpoint.
4633 Conditions are also accepted for watchpoints; you may not need them,
4634 since a watchpoint is inspecting the value of an expression anyhow---but
4635 it might be simpler, say, to just set a watchpoint on a variable name,
4636 and specify a condition that tests whether the new value is an interesting
4639 Break conditions can have side effects, and may even call functions in
4640 your program. This can be useful, for example, to activate functions
4641 that log program progress, or to use your own print functions to
4642 format special data structures. The effects are completely predictable
4643 unless there is another enabled breakpoint at the same address. (In
4644 that case, @value{GDBN} might see the other breakpoint first and stop your
4645 program without checking the condition of this one.) Note that
4646 breakpoint commands are usually more convenient and flexible than break
4648 purpose of performing side effects when a breakpoint is reached
4649 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4651 Breakpoint conditions can also be evaluated on the target's side if
4652 the target supports it. Instead of evaluating the conditions locally,
4653 @value{GDBN} encodes the expression into an agent expression
4654 (@pxref{Agent Expressions}) suitable for execution on the target,
4655 independently of @value{GDBN}. Global variables become raw memory
4656 locations, locals become stack accesses, and so forth.
4658 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4659 when its condition evaluates to true. This mechanism may provide faster
4660 response times depending on the performance characteristics of the target
4661 since it does not need to keep @value{GDBN} informed about
4662 every breakpoint trigger, even those with false conditions.
4664 Break conditions can be specified when a breakpoint is set, by using
4665 @samp{if} in the arguments to the @code{break} command. @xref{Set
4666 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4667 with the @code{condition} command.
4669 You can also use the @code{if} keyword with the @code{watch} command.
4670 The @code{catch} command does not recognize the @code{if} keyword;
4671 @code{condition} is the only way to impose a further condition on a
4676 @item condition @var{bnum} @var{expression}
4677 Specify @var{expression} as the break condition for breakpoint,
4678 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4679 breakpoint @var{bnum} stops your program only if the value of
4680 @var{expression} is true (nonzero, in C). When you use
4681 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4682 syntactic correctness, and to determine whether symbols in it have
4683 referents in the context of your breakpoint. If @var{expression} uses
4684 symbols not referenced in the context of the breakpoint, @value{GDBN}
4685 prints an error message:
4688 No symbol "foo" in current context.
4693 not actually evaluate @var{expression} at the time the @code{condition}
4694 command (or a command that sets a breakpoint with a condition, like
4695 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4697 @item condition @var{bnum}
4698 Remove the condition from breakpoint number @var{bnum}. It becomes
4699 an ordinary unconditional breakpoint.
4702 @cindex ignore count (of breakpoint)
4703 A special case of a breakpoint condition is to stop only when the
4704 breakpoint has been reached a certain number of times. This is so
4705 useful that there is a special way to do it, using the @dfn{ignore
4706 count} of the breakpoint. Every breakpoint has an ignore count, which
4707 is an integer. Most of the time, the ignore count is zero, and
4708 therefore has no effect. But if your program reaches a breakpoint whose
4709 ignore count is positive, then instead of stopping, it just decrements
4710 the ignore count by one and continues. As a result, if the ignore count
4711 value is @var{n}, the breakpoint does not stop the next @var{n} times
4712 your program reaches it.
4716 @item ignore @var{bnum} @var{count}
4717 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4718 The next @var{count} times the breakpoint is reached, your program's
4719 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4722 To make the breakpoint stop the next time it is reached, specify
4725 When you use @code{continue} to resume execution of your program from a
4726 breakpoint, you can specify an ignore count directly as an argument to
4727 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4728 Stepping,,Continuing and Stepping}.
4730 If a breakpoint has a positive ignore count and a condition, the
4731 condition is not checked. Once the ignore count reaches zero,
4732 @value{GDBN} resumes checking the condition.
4734 You could achieve the effect of the ignore count with a condition such
4735 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4736 is decremented each time. @xref{Convenience Vars, ,Convenience
4740 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4743 @node Break Commands
4744 @subsection Breakpoint Command Lists
4746 @cindex breakpoint commands
4747 You can give any breakpoint (or watchpoint or catchpoint) a series of
4748 commands to execute when your program stops due to that breakpoint. For
4749 example, you might want to print the values of certain expressions, or
4750 enable other breakpoints.
4754 @kindex end@r{ (breakpoint commands)}
4755 @item commands @r{[}@var{range}@dots{}@r{]}
4756 @itemx @dots{} @var{command-list} @dots{}
4758 Specify a list of commands for the given breakpoints. The commands
4759 themselves appear on the following lines. Type a line containing just
4760 @code{end} to terminate the commands.
4762 To remove all commands from a breakpoint, type @code{commands} and
4763 follow it immediately with @code{end}; that is, give no commands.
4765 With no argument, @code{commands} refers to the last breakpoint,
4766 watchpoint, or catchpoint set (not to the breakpoint most recently
4767 encountered). If the most recent breakpoints were set with a single
4768 command, then the @code{commands} will apply to all the breakpoints
4769 set by that command. This applies to breakpoints set by
4770 @code{rbreak}, and also applies when a single @code{break} command
4771 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4775 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4776 disabled within a @var{command-list}.
4778 You can use breakpoint commands to start your program up again. Simply
4779 use the @code{continue} command, or @code{step}, or any other command
4780 that resumes execution.
4782 Any other commands in the command list, after a command that resumes
4783 execution, are ignored. This is because any time you resume execution
4784 (even with a simple @code{next} or @code{step}), you may encounter
4785 another breakpoint---which could have its own command list, leading to
4786 ambiguities about which list to execute.
4789 If the first command you specify in a command list is @code{silent}, the
4790 usual message about stopping at a breakpoint is not printed. This may
4791 be desirable for breakpoints that are to print a specific message and
4792 then continue. If none of the remaining commands print anything, you
4793 see no sign that the breakpoint was reached. @code{silent} is
4794 meaningful only at the beginning of a breakpoint command list.
4796 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4797 print precisely controlled output, and are often useful in silent
4798 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4800 For example, here is how you could use breakpoint commands to print the
4801 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4807 printf "x is %d\n",x
4812 One application for breakpoint commands is to compensate for one bug so
4813 you can test for another. Put a breakpoint just after the erroneous line
4814 of code, give it a condition to detect the case in which something
4815 erroneous has been done, and give it commands to assign correct values
4816 to any variables that need them. End with the @code{continue} command
4817 so that your program does not stop, and start with the @code{silent}
4818 command so that no output is produced. Here is an example:
4829 @node Dynamic Printf
4830 @subsection Dynamic Printf
4832 @cindex dynamic printf
4834 The dynamic printf command @code{dprintf} combines a breakpoint with
4835 formatted printing of your program's data to give you the effect of
4836 inserting @code{printf} calls into your program on-the-fly, without
4837 having to recompile it.
4839 In its most basic form, the output goes to the GDB console. However,
4840 you can set the variable @code{dprintf-style} for alternate handling.
4841 For instance, you can ask to format the output by calling your
4842 program's @code{printf} function. This has the advantage that the
4843 characters go to the program's output device, so they can recorded in
4844 redirects to files and so forth.
4846 If you are doing remote debugging with a stub or agent, you can also
4847 ask to have the printf handled by the remote agent. In addition to
4848 ensuring that the output goes to the remote program's device along
4849 with any other output the program might produce, you can also ask that
4850 the dprintf remain active even after disconnecting from the remote
4851 target. Using the stub/agent is also more efficient, as it can do
4852 everything without needing to communicate with @value{GDBN}.
4856 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4857 Whenever execution reaches @var{location}, print the values of one or
4858 more @var{expressions} under the control of the string @var{template}.
4859 To print several values, separate them with commas.
4861 @item set dprintf-style @var{style}
4862 Set the dprintf output to be handled in one of several different
4863 styles enumerated below. A change of style affects all existing
4864 dynamic printfs immediately. (If you need individual control over the
4865 print commands, simply define normal breakpoints with
4866 explicitly-supplied command lists.)
4869 @kindex dprintf-style gdb
4870 Handle the output using the @value{GDBN} @code{printf} command.
4873 @kindex dprintf-style call
4874 Handle the output by calling a function in your program (normally
4878 @kindex dprintf-style agent
4879 Have the remote debugging agent (such as @code{gdbserver}) handle
4880 the output itself. This style is only available for agents that
4881 support running commands on the target.
4883 @item set dprintf-function @var{function}
4884 Set the function to call if the dprintf style is @code{call}. By
4885 default its value is @code{printf}. You may set it to any expression.
4886 that @value{GDBN} can evaluate to a function, as per the @code{call}
4889 @item set dprintf-channel @var{channel}
4890 Set a ``channel'' for dprintf. If set to a non-empty value,
4891 @value{GDBN} will evaluate it as an expression and pass the result as
4892 a first argument to the @code{dprintf-function}, in the manner of
4893 @code{fprintf} and similar functions. Otherwise, the dprintf format
4894 string will be the first argument, in the manner of @code{printf}.
4896 As an example, if you wanted @code{dprintf} output to go to a logfile
4897 that is a standard I/O stream assigned to the variable @code{mylog},
4898 you could do the following:
4901 (gdb) set dprintf-style call
4902 (gdb) set dprintf-function fprintf
4903 (gdb) set dprintf-channel mylog
4904 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
4905 Dprintf 1 at 0x123456: file main.c, line 25.
4907 1 dprintf keep y 0x00123456 in main at main.c:25
4908 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
4913 Note that the @code{info break} displays the dynamic printf commands
4914 as normal breakpoint commands; you can thus easily see the effect of
4915 the variable settings.
4917 @item set disconnected-dprintf on
4918 @itemx set disconnected-dprintf off
4919 @kindex set disconnected-dprintf
4920 Choose whether @code{dprintf} commands should continue to run if
4921 @value{GDBN} has disconnected from the target. This only applies
4922 if the @code{dprintf-style} is @code{agent}.
4924 @item show disconnected-dprintf off
4925 @kindex show disconnected-dprintf
4926 Show the current choice for disconnected @code{dprintf}.
4930 @value{GDBN} does not check the validity of function and channel,
4931 relying on you to supply values that are meaningful for the contexts
4932 in which they are being used. For instance, the function and channel
4933 may be the values of local variables, but if that is the case, then
4934 all enabled dynamic prints must be at locations within the scope of
4935 those locals. If evaluation fails, @value{GDBN} will report an error.
4937 @node Save Breakpoints
4938 @subsection How to save breakpoints to a file
4940 To save breakpoint definitions to a file use the @w{@code{save
4941 breakpoints}} command.
4944 @kindex save breakpoints
4945 @cindex save breakpoints to a file for future sessions
4946 @item save breakpoints [@var{filename}]
4947 This command saves all current breakpoint definitions together with
4948 their commands and ignore counts, into a file @file{@var{filename}}
4949 suitable for use in a later debugging session. This includes all
4950 types of breakpoints (breakpoints, watchpoints, catchpoints,
4951 tracepoints). To read the saved breakpoint definitions, use the
4952 @code{source} command (@pxref{Command Files}). Note that watchpoints
4953 with expressions involving local variables may fail to be recreated
4954 because it may not be possible to access the context where the
4955 watchpoint is valid anymore. Because the saved breakpoint definitions
4956 are simply a sequence of @value{GDBN} commands that recreate the
4957 breakpoints, you can edit the file in your favorite editing program,
4958 and remove the breakpoint definitions you're not interested in, or
4959 that can no longer be recreated.
4962 @node Static Probe Points
4963 @subsection Static Probe Points
4965 @cindex static probe point, SystemTap
4966 @cindex static probe point, DTrace
4967 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
4968 for Statically Defined Tracing, and the probes are designed to have a tiny
4969 runtime code and data footprint, and no dynamic relocations.
4971 Currently, the following types of probes are supported on
4972 ELF-compatible systems:
4976 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
4977 @acronym{SDT} probes@footnote{See
4978 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
4979 for more information on how to add @code{SystemTap} @acronym{SDT}
4980 probes in your applications.}. @code{SystemTap} probes are usable
4981 from assembly, C and C@t{++} languages@footnote{See
4982 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
4983 for a good reference on how the @acronym{SDT} probes are implemented.}.
4985 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
4986 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
4990 @cindex semaphores on static probe points
4991 Some @code{SystemTap} probes have an associated semaphore variable;
4992 for instance, this happens automatically if you defined your probe
4993 using a DTrace-style @file{.d} file. If your probe has a semaphore,
4994 @value{GDBN} will automatically enable it when you specify a
4995 breakpoint using the @samp{-probe-stap} notation. But, if you put a
4996 breakpoint at a probe's location by some other method (e.g.,
4997 @code{break file:line}), then @value{GDBN} will not automatically set
4998 the semaphore. @code{DTrace} probes do not support semaphores.
5000 You can examine the available static static probes using @code{info
5001 probes}, with optional arguments:
5005 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5006 If given, @var{type} is either @code{stap} for listing
5007 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5008 probes. If omitted all probes are listed regardless of their types.
5010 If given, @var{provider} is a regular expression used to match against provider
5011 names when selecting which probes to list. If omitted, probes by all
5012 probes from all providers are listed.
5014 If given, @var{name} is a regular expression to match against probe names
5015 when selecting which probes to list. If omitted, probe names are not
5016 considered when deciding whether to display them.
5018 If given, @var{objfile} is a regular expression used to select which
5019 object files (executable or shared libraries) to examine. If not
5020 given, all object files are considered.
5022 @item info probes all
5023 List the available static probes, from all types.
5026 @cindex enabling and disabling probes
5027 Some probe points can be enabled and/or disabled. The effect of
5028 enabling or disabling a probe depends on the type of probe being
5029 handled. Some @code{DTrace} probes can be enabled or
5030 disabled, but @code{SystemTap} probes cannot be disabled.
5032 You can enable (or disable) one or more probes using the following
5033 commands, with optional arguments:
5036 @kindex enable probes
5037 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5038 If given, @var{provider} is a regular expression used to match against
5039 provider names when selecting which probes to enable. If omitted,
5040 all probes from all providers are enabled.
5042 If given, @var{name} is a regular expression to match against probe
5043 names when selecting which probes to enable. If omitted, probe names
5044 are not considered when deciding whether to enable them.
5046 If given, @var{objfile} is a regular expression used to select which
5047 object files (executable or shared libraries) to examine. If not
5048 given, all object files are considered.
5050 @kindex disable probes
5051 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5052 See the @code{enable probes} command above for a description of the
5053 optional arguments accepted by this command.
5056 @vindex $_probe_arg@r{, convenience variable}
5057 A probe may specify up to twelve arguments. These are available at the
5058 point at which the probe is defined---that is, when the current PC is
5059 at the probe's location. The arguments are available using the
5060 convenience variables (@pxref{Convenience Vars})
5061 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
5062 probes each probe argument is an integer of the appropriate size;
5063 types are not preserved. In @code{DTrace} probes types are preserved
5064 provided that they are recognized as such by @value{GDBN}; otherwise
5065 the value of the probe argument will be a long integer. The
5066 convenience variable @code{$_probe_argc} holds the number of arguments
5067 at the current probe point.
5069 These variables are always available, but attempts to access them at
5070 any location other than a probe point will cause @value{GDBN} to give
5074 @c @ifclear BARETARGET
5075 @node Error in Breakpoints
5076 @subsection ``Cannot insert breakpoints''
5078 If you request too many active hardware-assisted breakpoints and
5079 watchpoints, you will see this error message:
5081 @c FIXME: the precise wording of this message may change; the relevant
5082 @c source change is not committed yet (Sep 3, 1999).
5084 Stopped; cannot insert breakpoints.
5085 You may have requested too many hardware breakpoints and watchpoints.
5089 This message is printed when you attempt to resume the program, since
5090 only then @value{GDBN} knows exactly how many hardware breakpoints and
5091 watchpoints it needs to insert.
5093 When this message is printed, you need to disable or remove some of the
5094 hardware-assisted breakpoints and watchpoints, and then continue.
5096 @node Breakpoint-related Warnings
5097 @subsection ``Breakpoint address adjusted...''
5098 @cindex breakpoint address adjusted
5100 Some processor architectures place constraints on the addresses at
5101 which breakpoints may be placed. For architectures thus constrained,
5102 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5103 with the constraints dictated by the architecture.
5105 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5106 a VLIW architecture in which a number of RISC-like instructions may be
5107 bundled together for parallel execution. The FR-V architecture
5108 constrains the location of a breakpoint instruction within such a
5109 bundle to the instruction with the lowest address. @value{GDBN}
5110 honors this constraint by adjusting a breakpoint's address to the
5111 first in the bundle.
5113 It is not uncommon for optimized code to have bundles which contain
5114 instructions from different source statements, thus it may happen that
5115 a breakpoint's address will be adjusted from one source statement to
5116 another. Since this adjustment may significantly alter @value{GDBN}'s
5117 breakpoint related behavior from what the user expects, a warning is
5118 printed when the breakpoint is first set and also when the breakpoint
5121 A warning like the one below is printed when setting a breakpoint
5122 that's been subject to address adjustment:
5125 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5128 Such warnings are printed both for user settable and @value{GDBN}'s
5129 internal breakpoints. If you see one of these warnings, you should
5130 verify that a breakpoint set at the adjusted address will have the
5131 desired affect. If not, the breakpoint in question may be removed and
5132 other breakpoints may be set which will have the desired behavior.
5133 E.g., it may be sufficient to place the breakpoint at a later
5134 instruction. A conditional breakpoint may also be useful in some
5135 cases to prevent the breakpoint from triggering too often.
5137 @value{GDBN} will also issue a warning when stopping at one of these
5138 adjusted breakpoints:
5141 warning: Breakpoint 1 address previously adjusted from 0x00010414
5145 When this warning is encountered, it may be too late to take remedial
5146 action except in cases where the breakpoint is hit earlier or more
5147 frequently than expected.
5149 @node Continuing and Stepping
5150 @section Continuing and Stepping
5154 @cindex resuming execution
5155 @dfn{Continuing} means resuming program execution until your program
5156 completes normally. In contrast, @dfn{stepping} means executing just
5157 one more ``step'' of your program, where ``step'' may mean either one
5158 line of source code, or one machine instruction (depending on what
5159 particular command you use). Either when continuing or when stepping,
5160 your program may stop even sooner, due to a breakpoint or a signal. (If
5161 it stops due to a signal, you may want to use @code{handle}, or use
5162 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5163 or you may step into the signal's handler (@pxref{stepping and signal
5168 @kindex c @r{(@code{continue})}
5169 @kindex fg @r{(resume foreground execution)}
5170 @item continue @r{[}@var{ignore-count}@r{]}
5171 @itemx c @r{[}@var{ignore-count}@r{]}
5172 @itemx fg @r{[}@var{ignore-count}@r{]}
5173 Resume program execution, at the address where your program last stopped;
5174 any breakpoints set at that address are bypassed. The optional argument
5175 @var{ignore-count} allows you to specify a further number of times to
5176 ignore a breakpoint at this location; its effect is like that of
5177 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5179 The argument @var{ignore-count} is meaningful only when your program
5180 stopped due to a breakpoint. At other times, the argument to
5181 @code{continue} is ignored.
5183 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5184 debugged program is deemed to be the foreground program) are provided
5185 purely for convenience, and have exactly the same behavior as
5189 To resume execution at a different place, you can use @code{return}
5190 (@pxref{Returning, ,Returning from a Function}) to go back to the
5191 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5192 Different Address}) to go to an arbitrary location in your program.
5194 A typical technique for using stepping is to set a breakpoint
5195 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5196 beginning of the function or the section of your program where a problem
5197 is believed to lie, run your program until it stops at that breakpoint,
5198 and then step through the suspect area, examining the variables that are
5199 interesting, until you see the problem happen.
5203 @kindex s @r{(@code{step})}
5205 Continue running your program until control reaches a different source
5206 line, then stop it and return control to @value{GDBN}. This command is
5207 abbreviated @code{s}.
5210 @c "without debugging information" is imprecise; actually "without line
5211 @c numbers in the debugging information". (gcc -g1 has debugging info but
5212 @c not line numbers). But it seems complex to try to make that
5213 @c distinction here.
5214 @emph{Warning:} If you use the @code{step} command while control is
5215 within a function that was compiled without debugging information,
5216 execution proceeds until control reaches a function that does have
5217 debugging information. Likewise, it will not step into a function which
5218 is compiled without debugging information. To step through functions
5219 without debugging information, use the @code{stepi} command, described
5223 The @code{step} command only stops at the first instruction of a source
5224 line. This prevents the multiple stops that could otherwise occur in
5225 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5226 to stop if a function that has debugging information is called within
5227 the line. In other words, @code{step} @emph{steps inside} any functions
5228 called within the line.
5230 Also, the @code{step} command only enters a function if there is line
5231 number information for the function. Otherwise it acts like the
5232 @code{next} command. This avoids problems when using @code{cc -gl}
5233 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5234 was any debugging information about the routine.
5236 @item step @var{count}
5237 Continue running as in @code{step}, but do so @var{count} times. If a
5238 breakpoint is reached, or a signal not related to stepping occurs before
5239 @var{count} steps, stepping stops right away.
5242 @kindex n @r{(@code{next})}
5243 @item next @r{[}@var{count}@r{]}
5244 Continue to the next source line in the current (innermost) stack frame.
5245 This is similar to @code{step}, but function calls that appear within
5246 the line of code are executed without stopping. Execution stops when
5247 control reaches a different line of code at the original stack level
5248 that was executing when you gave the @code{next} command. This command
5249 is abbreviated @code{n}.
5251 An argument @var{count} is a repeat count, as for @code{step}.
5254 @c FIX ME!! Do we delete this, or is there a way it fits in with
5255 @c the following paragraph? --- Vctoria
5257 @c @code{next} within a function that lacks debugging information acts like
5258 @c @code{step}, but any function calls appearing within the code of the
5259 @c function are executed without stopping.
5261 The @code{next} command only stops at the first instruction of a
5262 source line. This prevents multiple stops that could otherwise occur in
5263 @code{switch} statements, @code{for} loops, etc.
5265 @kindex set step-mode
5267 @cindex functions without line info, and stepping
5268 @cindex stepping into functions with no line info
5269 @itemx set step-mode on
5270 The @code{set step-mode on} command causes the @code{step} command to
5271 stop at the first instruction of a function which contains no debug line
5272 information rather than stepping over it.
5274 This is useful in cases where you may be interested in inspecting the
5275 machine instructions of a function which has no symbolic info and do not
5276 want @value{GDBN} to automatically skip over this function.
5278 @item set step-mode off
5279 Causes the @code{step} command to step over any functions which contains no
5280 debug information. This is the default.
5282 @item show step-mode
5283 Show whether @value{GDBN} will stop in or step over functions without
5284 source line debug information.
5287 @kindex fin @r{(@code{finish})}
5289 Continue running until just after function in the selected stack frame
5290 returns. Print the returned value (if any). This command can be
5291 abbreviated as @code{fin}.
5293 Contrast this with the @code{return} command (@pxref{Returning,
5294 ,Returning from a Function}).
5297 @kindex u @r{(@code{until})}
5298 @cindex run until specified location
5301 Continue running until a source line past the current line, in the
5302 current stack frame, is reached. This command is used to avoid single
5303 stepping through a loop more than once. It is like the @code{next}
5304 command, except that when @code{until} encounters a jump, it
5305 automatically continues execution until the program counter is greater
5306 than the address of the jump.
5308 This means that when you reach the end of a loop after single stepping
5309 though it, @code{until} makes your program continue execution until it
5310 exits the loop. In contrast, a @code{next} command at the end of a loop
5311 simply steps back to the beginning of the loop, which forces you to step
5312 through the next iteration.
5314 @code{until} always stops your program if it attempts to exit the current
5317 @code{until} may produce somewhat counterintuitive results if the order
5318 of machine code does not match the order of the source lines. For
5319 example, in the following excerpt from a debugging session, the @code{f}
5320 (@code{frame}) command shows that execution is stopped at line
5321 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5325 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5327 (@value{GDBP}) until
5328 195 for ( ; argc > 0; NEXTARG) @{
5331 This happened because, for execution efficiency, the compiler had
5332 generated code for the loop closure test at the end, rather than the
5333 start, of the loop---even though the test in a C @code{for}-loop is
5334 written before the body of the loop. The @code{until} command appeared
5335 to step back to the beginning of the loop when it advanced to this
5336 expression; however, it has not really gone to an earlier
5337 statement---not in terms of the actual machine code.
5339 @code{until} with no argument works by means of single
5340 instruction stepping, and hence is slower than @code{until} with an
5343 @item until @var{location}
5344 @itemx u @var{location}
5345 Continue running your program until either the specified @var{location} is
5346 reached, or the current stack frame returns. The location is any of
5347 the forms described in @ref{Specify Location}.
5348 This form of the command uses temporary breakpoints, and
5349 hence is quicker than @code{until} without an argument. The specified
5350 location is actually reached only if it is in the current frame. This
5351 implies that @code{until} can be used to skip over recursive function
5352 invocations. For instance in the code below, if the current location is
5353 line @code{96}, issuing @code{until 99} will execute the program up to
5354 line @code{99} in the same invocation of factorial, i.e., after the inner
5355 invocations have returned.
5358 94 int factorial (int value)
5360 96 if (value > 1) @{
5361 97 value *= factorial (value - 1);
5368 @kindex advance @var{location}
5369 @item advance @var{location}
5370 Continue running the program up to the given @var{location}. An argument is
5371 required, which should be of one of the forms described in
5372 @ref{Specify Location}.
5373 Execution will also stop upon exit from the current stack
5374 frame. This command is similar to @code{until}, but @code{advance} will
5375 not skip over recursive function calls, and the target location doesn't
5376 have to be in the same frame as the current one.
5380 @kindex si @r{(@code{stepi})}
5382 @itemx stepi @var{arg}
5384 Execute one machine instruction, then stop and return to the debugger.
5386 It is often useful to do @samp{display/i $pc} when stepping by machine
5387 instructions. This makes @value{GDBN} automatically display the next
5388 instruction to be executed, each time your program stops. @xref{Auto
5389 Display,, Automatic Display}.
5391 An argument is a repeat count, as in @code{step}.
5395 @kindex ni @r{(@code{nexti})}
5397 @itemx nexti @var{arg}
5399 Execute one machine instruction, but if it is a function call,
5400 proceed until the function returns.
5402 An argument is a repeat count, as in @code{next}.
5406 @anchor{range stepping}
5407 @cindex range stepping
5408 @cindex target-assisted range stepping
5409 By default, and if available, @value{GDBN} makes use of
5410 target-assisted @dfn{range stepping}. In other words, whenever you
5411 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5412 tells the target to step the corresponding range of instruction
5413 addresses instead of issuing multiple single-steps. This speeds up
5414 line stepping, particularly for remote targets. Ideally, there should
5415 be no reason you would want to turn range stepping off. However, it's
5416 possible that a bug in the debug info, a bug in the remote stub (for
5417 remote targets), or even a bug in @value{GDBN} could make line
5418 stepping behave incorrectly when target-assisted range stepping is
5419 enabled. You can use the following command to turn off range stepping
5423 @kindex set range-stepping
5424 @kindex show range-stepping
5425 @item set range-stepping
5426 @itemx show range-stepping
5427 Control whether range stepping is enabled.
5429 If @code{on}, and the target supports it, @value{GDBN} tells the
5430 target to step a range of addresses itself, instead of issuing
5431 multiple single-steps. If @code{off}, @value{GDBN} always issues
5432 single-steps, even if range stepping is supported by the target. The
5433 default is @code{on}.
5437 @node Skipping Over Functions and Files
5438 @section Skipping Over Functions and Files
5439 @cindex skipping over functions and files
5441 The program you are debugging may contain some functions which are
5442 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
5443 skip a function or all functions in a file when stepping.
5445 For example, consider the following C function:
5456 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5457 are not interested in stepping through @code{boring}. If you run @code{step}
5458 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5459 step over both @code{foo} and @code{boring}!
5461 One solution is to @code{step} into @code{boring} and use the @code{finish}
5462 command to immediately exit it. But this can become tedious if @code{boring}
5463 is called from many places.
5465 A more flexible solution is to execute @kbd{skip boring}. This instructs
5466 @value{GDBN} never to step into @code{boring}. Now when you execute
5467 @code{step} at line 103, you'll step over @code{boring} and directly into
5470 You can also instruct @value{GDBN} to skip all functions in a file, with, for
5471 example, @code{skip file boring.c}.
5474 @kindex skip function
5475 @item skip @r{[}@var{linespec}@r{]}
5476 @itemx skip function @r{[}@var{linespec}@r{]}
5477 After running this command, the function named by @var{linespec} or the
5478 function containing the line named by @var{linespec} will be skipped over when
5479 stepping. @xref{Specify Location}.
5481 If you do not specify @var{linespec}, the function you're currently debugging
5484 (If you have a function called @code{file} that you want to skip, use
5485 @kbd{skip function file}.)
5488 @item skip file @r{[}@var{filename}@r{]}
5489 After running this command, any function whose source lives in @var{filename}
5490 will be skipped over when stepping.
5492 If you do not specify @var{filename}, functions whose source lives in the file
5493 you're currently debugging will be skipped.
5496 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5497 These are the commands for managing your list of skips:
5501 @item info skip @r{[}@var{range}@r{]}
5502 Print details about the specified skip(s). If @var{range} is not specified,
5503 print a table with details about all functions and files marked for skipping.
5504 @code{info skip} prints the following information about each skip:
5508 A number identifying this skip.
5510 The type of this skip, either @samp{function} or @samp{file}.
5511 @item Enabled or Disabled
5512 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
5514 For function skips, this column indicates the address in memory of the function
5515 being skipped. If you've set a function skip on a function which has not yet
5516 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
5517 which has the function is loaded, @code{info skip} will show the function's
5520 For file skips, this field contains the filename being skipped. For functions
5521 skips, this field contains the function name and its line number in the file
5522 where it is defined.
5526 @item skip delete @r{[}@var{range}@r{]}
5527 Delete the specified skip(s). If @var{range} is not specified, delete all
5531 @item skip enable @r{[}@var{range}@r{]}
5532 Enable the specified skip(s). If @var{range} is not specified, enable all
5535 @kindex skip disable
5536 @item skip disable @r{[}@var{range}@r{]}
5537 Disable the specified skip(s). If @var{range} is not specified, disable all
5546 A signal is an asynchronous event that can happen in a program. The
5547 operating system defines the possible kinds of signals, and gives each
5548 kind a name and a number. For example, in Unix @code{SIGINT} is the
5549 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5550 @code{SIGSEGV} is the signal a program gets from referencing a place in
5551 memory far away from all the areas in use; @code{SIGALRM} occurs when
5552 the alarm clock timer goes off (which happens only if your program has
5553 requested an alarm).
5555 @cindex fatal signals
5556 Some signals, including @code{SIGALRM}, are a normal part of the
5557 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5558 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5559 program has not specified in advance some other way to handle the signal.
5560 @code{SIGINT} does not indicate an error in your program, but it is normally
5561 fatal so it can carry out the purpose of the interrupt: to kill the program.
5563 @value{GDBN} has the ability to detect any occurrence of a signal in your
5564 program. You can tell @value{GDBN} in advance what to do for each kind of
5567 @cindex handling signals
5568 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5569 @code{SIGALRM} be silently passed to your program
5570 (so as not to interfere with their role in the program's functioning)
5571 but to stop your program immediately whenever an error signal happens.
5572 You can change these settings with the @code{handle} command.
5575 @kindex info signals
5579 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5580 handle each one. You can use this to see the signal numbers of all
5581 the defined types of signals.
5583 @item info signals @var{sig}
5584 Similar, but print information only about the specified signal number.
5586 @code{info handle} is an alias for @code{info signals}.
5588 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5589 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5590 for details about this command.
5593 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5594 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
5595 can be the number of a signal or its name (with or without the
5596 @samp{SIG} at the beginning); a list of signal numbers of the form
5597 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5598 known signals. Optional arguments @var{keywords}, described below,
5599 say what change to make.
5603 The keywords allowed by the @code{handle} command can be abbreviated.
5604 Their full names are:
5608 @value{GDBN} should not stop your program when this signal happens. It may
5609 still print a message telling you that the signal has come in.
5612 @value{GDBN} should stop your program when this signal happens. This implies
5613 the @code{print} keyword as well.
5616 @value{GDBN} should print a message when this signal happens.
5619 @value{GDBN} should not mention the occurrence of the signal at all. This
5620 implies the @code{nostop} keyword as well.
5624 @value{GDBN} should allow your program to see this signal; your program
5625 can handle the signal, or else it may terminate if the signal is fatal
5626 and not handled. @code{pass} and @code{noignore} are synonyms.
5630 @value{GDBN} should not allow your program to see this signal.
5631 @code{nopass} and @code{ignore} are synonyms.
5635 When a signal stops your program, the signal is not visible to the
5637 continue. Your program sees the signal then, if @code{pass} is in
5638 effect for the signal in question @emph{at that time}. In other words,
5639 after @value{GDBN} reports a signal, you can use the @code{handle}
5640 command with @code{pass} or @code{nopass} to control whether your
5641 program sees that signal when you continue.
5643 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5644 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5645 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5648 You can also use the @code{signal} command to prevent your program from
5649 seeing a signal, or cause it to see a signal it normally would not see,
5650 or to give it any signal at any time. For example, if your program stopped
5651 due to some sort of memory reference error, you might store correct
5652 values into the erroneous variables and continue, hoping to see more
5653 execution; but your program would probably terminate immediately as
5654 a result of the fatal signal once it saw the signal. To prevent this,
5655 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5658 @cindex stepping and signal handlers
5659 @anchor{stepping and signal handlers}
5661 @value{GDBN} optimizes for stepping the mainline code. If a signal
5662 that has @code{handle nostop} and @code{handle pass} set arrives while
5663 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
5664 in progress, @value{GDBN} lets the signal handler run and then resumes
5665 stepping the mainline code once the signal handler returns. In other
5666 words, @value{GDBN} steps over the signal handler. This prevents
5667 signals that you've specified as not interesting (with @code{handle
5668 nostop}) from changing the focus of debugging unexpectedly. Note that
5669 the signal handler itself may still hit a breakpoint, stop for another
5670 signal that has @code{handle stop} in effect, or for any other event
5671 that normally results in stopping the stepping command sooner. Also
5672 note that @value{GDBN} still informs you that the program received a
5673 signal if @code{handle print} is set.
5675 @anchor{stepping into signal handlers}
5677 If you set @code{handle pass} for a signal, and your program sets up a
5678 handler for it, then issuing a stepping command, such as @code{step}
5679 or @code{stepi}, when your program is stopped due to the signal will
5680 step @emph{into} the signal handler (if the target supports that).
5682 Likewise, if you use the @code{queue-signal} command to queue a signal
5683 to be delivered to the current thread when execution of the thread
5684 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
5685 stepping command will step into the signal handler.
5687 Here's an example, using @code{stepi} to step to the first instruction
5688 of @code{SIGUSR1}'s handler:
5691 (@value{GDBP}) handle SIGUSR1
5692 Signal Stop Print Pass to program Description
5693 SIGUSR1 Yes Yes Yes User defined signal 1
5697 Program received signal SIGUSR1, User defined signal 1.
5698 main () sigusr1.c:28
5701 sigusr1_handler () at sigusr1.c:9
5705 The same, but using @code{queue-signal} instead of waiting for the
5706 program to receive the signal first:
5711 (@value{GDBP}) queue-signal SIGUSR1
5713 sigusr1_handler () at sigusr1.c:9
5718 @cindex extra signal information
5719 @anchor{extra signal information}
5721 On some targets, @value{GDBN} can inspect extra signal information
5722 associated with the intercepted signal, before it is actually
5723 delivered to the program being debugged. This information is exported
5724 by the convenience variable @code{$_siginfo}, and consists of data
5725 that is passed by the kernel to the signal handler at the time of the
5726 receipt of a signal. The data type of the information itself is
5727 target dependent. You can see the data type using the @code{ptype
5728 $_siginfo} command. On Unix systems, it typically corresponds to the
5729 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5732 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5733 referenced address that raised a segmentation fault.
5737 (@value{GDBP}) continue
5738 Program received signal SIGSEGV, Segmentation fault.
5739 0x0000000000400766 in main ()
5741 (@value{GDBP}) ptype $_siginfo
5748 struct @{...@} _kill;
5749 struct @{...@} _timer;
5751 struct @{...@} _sigchld;
5752 struct @{...@} _sigfault;
5753 struct @{...@} _sigpoll;
5756 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5760 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5761 $1 = (void *) 0x7ffff7ff7000
5765 Depending on target support, @code{$_siginfo} may also be writable.
5768 @section Stopping and Starting Multi-thread Programs
5770 @cindex stopped threads
5771 @cindex threads, stopped
5773 @cindex continuing threads
5774 @cindex threads, continuing
5776 @value{GDBN} supports debugging programs with multiple threads
5777 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5778 are two modes of controlling execution of your program within the
5779 debugger. In the default mode, referred to as @dfn{all-stop mode},
5780 when any thread in your program stops (for example, at a breakpoint
5781 or while being stepped), all other threads in the program are also stopped by
5782 @value{GDBN}. On some targets, @value{GDBN} also supports
5783 @dfn{non-stop mode}, in which other threads can continue to run freely while
5784 you examine the stopped thread in the debugger.
5787 * All-Stop Mode:: All threads stop when GDB takes control
5788 * Non-Stop Mode:: Other threads continue to execute
5789 * Background Execution:: Running your program asynchronously
5790 * Thread-Specific Breakpoints:: Controlling breakpoints
5791 * Interrupted System Calls:: GDB may interfere with system calls
5792 * Observer Mode:: GDB does not alter program behavior
5796 @subsection All-Stop Mode
5798 @cindex all-stop mode
5800 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5801 @emph{all} threads of execution stop, not just the current thread. This
5802 allows you to examine the overall state of the program, including
5803 switching between threads, without worrying that things may change
5806 Conversely, whenever you restart the program, @emph{all} threads start
5807 executing. @emph{This is true even when single-stepping} with commands
5808 like @code{step} or @code{next}.
5810 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5811 Since thread scheduling is up to your debugging target's operating
5812 system (not controlled by @value{GDBN}), other threads may
5813 execute more than one statement while the current thread completes a
5814 single step. Moreover, in general other threads stop in the middle of a
5815 statement, rather than at a clean statement boundary, when the program
5818 You might even find your program stopped in another thread after
5819 continuing or even single-stepping. This happens whenever some other
5820 thread runs into a breakpoint, a signal, or an exception before the
5821 first thread completes whatever you requested.
5823 @cindex automatic thread selection
5824 @cindex switching threads automatically
5825 @cindex threads, automatic switching
5826 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5827 signal, it automatically selects the thread where that breakpoint or
5828 signal happened. @value{GDBN} alerts you to the context switch with a
5829 message such as @samp{[Switching to Thread @var{n}]} to identify the
5832 On some OSes, you can modify @value{GDBN}'s default behavior by
5833 locking the OS scheduler to allow only a single thread to run.
5836 @item set scheduler-locking @var{mode}
5837 @cindex scheduler locking mode
5838 @cindex lock scheduler
5839 Set the scheduler locking mode. If it is @code{off}, then there is no
5840 locking and any thread may run at any time. If @code{on}, then only the
5841 current thread may run when the inferior is resumed. The @code{step}
5842 mode optimizes for single-stepping; it prevents other threads
5843 from preempting the current thread while you are stepping, so that
5844 the focus of debugging does not change unexpectedly.
5845 Other threads never get a chance to run when you step, and they are
5846 completely free to run when you use commands
5847 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5848 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5849 the current thread away from the thread that you are debugging.
5851 @item show scheduler-locking
5852 Display the current scheduler locking mode.
5855 @cindex resume threads of multiple processes simultaneously
5856 By default, when you issue one of the execution commands such as
5857 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5858 threads of the current inferior to run. For example, if @value{GDBN}
5859 is attached to two inferiors, each with two threads, the
5860 @code{continue} command resumes only the two threads of the current
5861 inferior. This is useful, for example, when you debug a program that
5862 forks and you want to hold the parent stopped (so that, for instance,
5863 it doesn't run to exit), while you debug the child. In other
5864 situations, you may not be interested in inspecting the current state
5865 of any of the processes @value{GDBN} is attached to, and you may want
5866 to resume them all until some breakpoint is hit. In the latter case,
5867 you can instruct @value{GDBN} to allow all threads of all the
5868 inferiors to run with the @w{@code{set schedule-multiple}} command.
5871 @kindex set schedule-multiple
5872 @item set schedule-multiple
5873 Set the mode for allowing threads of multiple processes to be resumed
5874 when an execution command is issued. When @code{on}, all threads of
5875 all processes are allowed to run. When @code{off}, only the threads
5876 of the current process are resumed. The default is @code{off}. The
5877 @code{scheduler-locking} mode takes precedence when set to @code{on},
5878 or while you are stepping and set to @code{step}.
5880 @item show schedule-multiple
5881 Display the current mode for resuming the execution of threads of
5886 @subsection Non-Stop Mode
5888 @cindex non-stop mode
5890 @c This section is really only a place-holder, and needs to be expanded
5891 @c with more details.
5893 For some multi-threaded targets, @value{GDBN} supports an optional
5894 mode of operation in which you can examine stopped program threads in
5895 the debugger while other threads continue to execute freely. This
5896 minimizes intrusion when debugging live systems, such as programs
5897 where some threads have real-time constraints or must continue to
5898 respond to external events. This is referred to as @dfn{non-stop} mode.
5900 In non-stop mode, when a thread stops to report a debugging event,
5901 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5902 threads as well, in contrast to the all-stop mode behavior. Additionally,
5903 execution commands such as @code{continue} and @code{step} apply by default
5904 only to the current thread in non-stop mode, rather than all threads as
5905 in all-stop mode. This allows you to control threads explicitly in
5906 ways that are not possible in all-stop mode --- for example, stepping
5907 one thread while allowing others to run freely, stepping
5908 one thread while holding all others stopped, or stepping several threads
5909 independently and simultaneously.
5911 To enter non-stop mode, use this sequence of commands before you run
5912 or attach to your program:
5915 # If using the CLI, pagination breaks non-stop.
5918 # Finally, turn it on!
5922 You can use these commands to manipulate the non-stop mode setting:
5925 @kindex set non-stop
5926 @item set non-stop on
5927 Enable selection of non-stop mode.
5928 @item set non-stop off
5929 Disable selection of non-stop mode.
5930 @kindex show non-stop
5932 Show the current non-stop enablement setting.
5935 Note these commands only reflect whether non-stop mode is enabled,
5936 not whether the currently-executing program is being run in non-stop mode.
5937 In particular, the @code{set non-stop} preference is only consulted when
5938 @value{GDBN} starts or connects to the target program, and it is generally
5939 not possible to switch modes once debugging has started. Furthermore,
5940 since not all targets support non-stop mode, even when you have enabled
5941 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5944 In non-stop mode, all execution commands apply only to the current thread
5945 by default. That is, @code{continue} only continues one thread.
5946 To continue all threads, issue @code{continue -a} or @code{c -a}.
5948 You can use @value{GDBN}'s background execution commands
5949 (@pxref{Background Execution}) to run some threads in the background
5950 while you continue to examine or step others from @value{GDBN}.
5951 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5952 always executed asynchronously in non-stop mode.
5954 Suspending execution is done with the @code{interrupt} command when
5955 running in the background, or @kbd{Ctrl-c} during foreground execution.
5956 In all-stop mode, this stops the whole process;
5957 but in non-stop mode the interrupt applies only to the current thread.
5958 To stop the whole program, use @code{interrupt -a}.
5960 Other execution commands do not currently support the @code{-a} option.
5962 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5963 that thread current, as it does in all-stop mode. This is because the
5964 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5965 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5966 changed to a different thread just as you entered a command to operate on the
5967 previously current thread.
5969 @node Background Execution
5970 @subsection Background Execution
5972 @cindex foreground execution
5973 @cindex background execution
5974 @cindex asynchronous execution
5975 @cindex execution, foreground, background and asynchronous
5977 @value{GDBN}'s execution commands have two variants: the normal
5978 foreground (synchronous) behavior, and a background
5979 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5980 the program to report that some thread has stopped before prompting for
5981 another command. In background execution, @value{GDBN} immediately gives
5982 a command prompt so that you can issue other commands while your program runs.
5984 If the target doesn't support async mode, @value{GDBN} issues an error
5985 message if you attempt to use the background execution commands.
5987 To specify background execution, add a @code{&} to the command. For example,
5988 the background form of the @code{continue} command is @code{continue&}, or
5989 just @code{c&}. The execution commands that accept background execution
5995 @xref{Starting, , Starting your Program}.
5999 @xref{Attach, , Debugging an Already-running Process}.
6003 @xref{Continuing and Stepping, step}.
6007 @xref{Continuing and Stepping, stepi}.
6011 @xref{Continuing and Stepping, next}.
6015 @xref{Continuing and Stepping, nexti}.
6019 @xref{Continuing and Stepping, continue}.
6023 @xref{Continuing and Stepping, finish}.
6027 @xref{Continuing and Stepping, until}.
6031 Background execution is especially useful in conjunction with non-stop
6032 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
6033 However, you can also use these commands in the normal all-stop mode with
6034 the restriction that you cannot issue another execution command until the
6035 previous one finishes. Examples of commands that are valid in all-stop
6036 mode while the program is running include @code{help} and @code{info break}.
6038 You can interrupt your program while it is running in the background by
6039 using the @code{interrupt} command.
6046 Suspend execution of the running program. In all-stop mode,
6047 @code{interrupt} stops the whole process, but in non-stop mode, it stops
6048 only the current thread. To stop the whole program in non-stop mode,
6049 use @code{interrupt -a}.
6052 @node Thread-Specific Breakpoints
6053 @subsection Thread-Specific Breakpoints
6055 When your program has multiple threads (@pxref{Threads,, Debugging
6056 Programs with Multiple Threads}), you can choose whether to set
6057 breakpoints on all threads, or on a particular thread.
6060 @cindex breakpoints and threads
6061 @cindex thread breakpoints
6062 @kindex break @dots{} thread @var{threadno}
6063 @item break @var{location} thread @var{threadno}
6064 @itemx break @var{location} thread @var{threadno} if @dots{}
6065 @var{location} specifies source lines; there are several ways of
6066 writing them (@pxref{Specify Location}), but the effect is always to
6067 specify some source line.
6069 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
6070 to specify that you only want @value{GDBN} to stop the program when a
6071 particular thread reaches this breakpoint. The @var{threadno} specifier
6072 is one of the numeric thread identifiers assigned by @value{GDBN}, shown
6073 in the first column of the @samp{info threads} display.
6075 If you do not specify @samp{thread @var{threadno}} when you set a
6076 breakpoint, the breakpoint applies to @emph{all} threads of your
6079 You can use the @code{thread} qualifier on conditional breakpoints as
6080 well; in this case, place @samp{thread @var{threadno}} before or
6081 after the breakpoint condition, like this:
6084 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6089 Thread-specific breakpoints are automatically deleted when
6090 @value{GDBN} detects the corresponding thread is no longer in the
6091 thread list. For example:
6095 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6098 There are several ways for a thread to disappear, such as a regular
6099 thread exit, but also when you detach from the process with the
6100 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6101 Process}), or if @value{GDBN} loses the remote connection
6102 (@pxref{Remote Debugging}), etc. Note that with some targets,
6103 @value{GDBN} is only able to detect a thread has exited when the user
6104 explictly asks for the thread list with the @code{info threads}
6107 @node Interrupted System Calls
6108 @subsection Interrupted System Calls
6110 @cindex thread breakpoints and system calls
6111 @cindex system calls and thread breakpoints
6112 @cindex premature return from system calls
6113 There is an unfortunate side effect when using @value{GDBN} to debug
6114 multi-threaded programs. If one thread stops for a
6115 breakpoint, or for some other reason, and another thread is blocked in a
6116 system call, then the system call may return prematurely. This is a
6117 consequence of the interaction between multiple threads and the signals
6118 that @value{GDBN} uses to implement breakpoints and other events that
6121 To handle this problem, your program should check the return value of
6122 each system call and react appropriately. This is good programming
6125 For example, do not write code like this:
6131 The call to @code{sleep} will return early if a different thread stops
6132 at a breakpoint or for some other reason.
6134 Instead, write this:
6139 unslept = sleep (unslept);
6142 A system call is allowed to return early, so the system is still
6143 conforming to its specification. But @value{GDBN} does cause your
6144 multi-threaded program to behave differently than it would without
6147 Also, @value{GDBN} uses internal breakpoints in the thread library to
6148 monitor certain events such as thread creation and thread destruction.
6149 When such an event happens, a system call in another thread may return
6150 prematurely, even though your program does not appear to stop.
6153 @subsection Observer Mode
6155 If you want to build on non-stop mode and observe program behavior
6156 without any chance of disruption by @value{GDBN}, you can set
6157 variables to disable all of the debugger's attempts to modify state,
6158 whether by writing memory, inserting breakpoints, etc. These operate
6159 at a low level, intercepting operations from all commands.
6161 When all of these are set to @code{off}, then @value{GDBN} is said to
6162 be @dfn{observer mode}. As a convenience, the variable
6163 @code{observer} can be set to disable these, plus enable non-stop
6166 Note that @value{GDBN} will not prevent you from making nonsensical
6167 combinations of these settings. For instance, if you have enabled
6168 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6169 then breakpoints that work by writing trap instructions into the code
6170 stream will still not be able to be placed.
6175 @item set observer on
6176 @itemx set observer off
6177 When set to @code{on}, this disables all the permission variables
6178 below (except for @code{insert-fast-tracepoints}), plus enables
6179 non-stop debugging. Setting this to @code{off} switches back to
6180 normal debugging, though remaining in non-stop mode.
6183 Show whether observer mode is on or off.
6185 @kindex may-write-registers
6186 @item set may-write-registers on
6187 @itemx set may-write-registers off
6188 This controls whether @value{GDBN} will attempt to alter the values of
6189 registers, such as with assignment expressions in @code{print}, or the
6190 @code{jump} command. It defaults to @code{on}.
6192 @item show may-write-registers
6193 Show the current permission to write registers.
6195 @kindex may-write-memory
6196 @item set may-write-memory on
6197 @itemx set may-write-memory off
6198 This controls whether @value{GDBN} will attempt to alter the contents
6199 of memory, such as with assignment expressions in @code{print}. It
6200 defaults to @code{on}.
6202 @item show may-write-memory
6203 Show the current permission to write memory.
6205 @kindex may-insert-breakpoints
6206 @item set may-insert-breakpoints on
6207 @itemx set may-insert-breakpoints off
6208 This controls whether @value{GDBN} will attempt to insert breakpoints.
6209 This affects all breakpoints, including internal breakpoints defined
6210 by @value{GDBN}. It defaults to @code{on}.
6212 @item show may-insert-breakpoints
6213 Show the current permission to insert breakpoints.
6215 @kindex may-insert-tracepoints
6216 @item set may-insert-tracepoints on
6217 @itemx set may-insert-tracepoints off
6218 This controls whether @value{GDBN} will attempt to insert (regular)
6219 tracepoints at the beginning of a tracing experiment. It affects only
6220 non-fast tracepoints, fast tracepoints being under the control of
6221 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6223 @item show may-insert-tracepoints
6224 Show the current permission to insert tracepoints.
6226 @kindex may-insert-fast-tracepoints
6227 @item set may-insert-fast-tracepoints on
6228 @itemx set may-insert-fast-tracepoints off
6229 This controls whether @value{GDBN} will attempt to insert fast
6230 tracepoints at the beginning of a tracing experiment. It affects only
6231 fast tracepoints, regular (non-fast) tracepoints being under the
6232 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6234 @item show may-insert-fast-tracepoints
6235 Show the current permission to insert fast tracepoints.
6237 @kindex may-interrupt
6238 @item set may-interrupt on
6239 @itemx set may-interrupt off
6240 This controls whether @value{GDBN} will attempt to interrupt or stop
6241 program execution. When this variable is @code{off}, the
6242 @code{interrupt} command will have no effect, nor will
6243 @kbd{Ctrl-c}. It defaults to @code{on}.
6245 @item show may-interrupt
6246 Show the current permission to interrupt or stop the program.
6250 @node Reverse Execution
6251 @chapter Running programs backward
6252 @cindex reverse execution
6253 @cindex running programs backward
6255 When you are debugging a program, it is not unusual to realize that
6256 you have gone too far, and some event of interest has already happened.
6257 If the target environment supports it, @value{GDBN} can allow you to
6258 ``rewind'' the program by running it backward.
6260 A target environment that supports reverse execution should be able
6261 to ``undo'' the changes in machine state that have taken place as the
6262 program was executing normally. Variables, registers etc.@: should
6263 revert to their previous values. Obviously this requires a great
6264 deal of sophistication on the part of the target environment; not
6265 all target environments can support reverse execution.
6267 When a program is executed in reverse, the instructions that
6268 have most recently been executed are ``un-executed'', in reverse
6269 order. The program counter runs backward, following the previous
6270 thread of execution in reverse. As each instruction is ``un-executed'',
6271 the values of memory and/or registers that were changed by that
6272 instruction are reverted to their previous states. After executing
6273 a piece of source code in reverse, all side effects of that code
6274 should be ``undone'', and all variables should be returned to their
6275 prior values@footnote{
6276 Note that some side effects are easier to undo than others. For instance,
6277 memory and registers are relatively easy, but device I/O is hard. Some
6278 targets may be able undo things like device I/O, and some may not.
6280 The contract between @value{GDBN} and the reverse executing target
6281 requires only that the target do something reasonable when
6282 @value{GDBN} tells it to execute backwards, and then report the
6283 results back to @value{GDBN}. Whatever the target reports back to
6284 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6285 assumes that the memory and registers that the target reports are in a
6286 consistant state, but @value{GDBN} accepts whatever it is given.
6289 If you are debugging in a target environment that supports
6290 reverse execution, @value{GDBN} provides the following commands.
6293 @kindex reverse-continue
6294 @kindex rc @r{(@code{reverse-continue})}
6295 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6296 @itemx rc @r{[}@var{ignore-count}@r{]}
6297 Beginning at the point where your program last stopped, start executing
6298 in reverse. Reverse execution will stop for breakpoints and synchronous
6299 exceptions (signals), just like normal execution. Behavior of
6300 asynchronous signals depends on the target environment.
6302 @kindex reverse-step
6303 @kindex rs @r{(@code{step})}
6304 @item reverse-step @r{[}@var{count}@r{]}
6305 Run the program backward until control reaches the start of a
6306 different source line; then stop it, and return control to @value{GDBN}.
6308 Like the @code{step} command, @code{reverse-step} will only stop
6309 at the beginning of a source line. It ``un-executes'' the previously
6310 executed source line. If the previous source line included calls to
6311 debuggable functions, @code{reverse-step} will step (backward) into
6312 the called function, stopping at the beginning of the @emph{last}
6313 statement in the called function (typically a return statement).
6315 Also, as with the @code{step} command, if non-debuggable functions are
6316 called, @code{reverse-step} will run thru them backward without stopping.
6318 @kindex reverse-stepi
6319 @kindex rsi @r{(@code{reverse-stepi})}
6320 @item reverse-stepi @r{[}@var{count}@r{]}
6321 Reverse-execute one machine instruction. Note that the instruction
6322 to be reverse-executed is @emph{not} the one pointed to by the program
6323 counter, but the instruction executed prior to that one. For instance,
6324 if the last instruction was a jump, @code{reverse-stepi} will take you
6325 back from the destination of the jump to the jump instruction itself.
6327 @kindex reverse-next
6328 @kindex rn @r{(@code{reverse-next})}
6329 @item reverse-next @r{[}@var{count}@r{]}
6330 Run backward to the beginning of the previous line executed in
6331 the current (innermost) stack frame. If the line contains function
6332 calls, they will be ``un-executed'' without stopping. Starting from
6333 the first line of a function, @code{reverse-next} will take you back
6334 to the caller of that function, @emph{before} the function was called,
6335 just as the normal @code{next} command would take you from the last
6336 line of a function back to its return to its caller
6337 @footnote{Unless the code is too heavily optimized.}.
6339 @kindex reverse-nexti
6340 @kindex rni @r{(@code{reverse-nexti})}
6341 @item reverse-nexti @r{[}@var{count}@r{]}
6342 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6343 in reverse, except that called functions are ``un-executed'' atomically.
6344 That is, if the previously executed instruction was a return from
6345 another function, @code{reverse-nexti} will continue to execute
6346 in reverse until the call to that function (from the current stack
6349 @kindex reverse-finish
6350 @item reverse-finish
6351 Just as the @code{finish} command takes you to the point where the
6352 current function returns, @code{reverse-finish} takes you to the point
6353 where it was called. Instead of ending up at the end of the current
6354 function invocation, you end up at the beginning.
6356 @kindex set exec-direction
6357 @item set exec-direction
6358 Set the direction of target execution.
6359 @item set exec-direction reverse
6360 @cindex execute forward or backward in time
6361 @value{GDBN} will perform all execution commands in reverse, until the
6362 exec-direction mode is changed to ``forward''. Affected commands include
6363 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6364 command cannot be used in reverse mode.
6365 @item set exec-direction forward
6366 @value{GDBN} will perform all execution commands in the normal fashion.
6367 This is the default.
6371 @node Process Record and Replay
6372 @chapter Recording Inferior's Execution and Replaying It
6373 @cindex process record and replay
6374 @cindex recording inferior's execution and replaying it
6376 On some platforms, @value{GDBN} provides a special @dfn{process record
6377 and replay} target that can record a log of the process execution, and
6378 replay it later with both forward and reverse execution commands.
6381 When this target is in use, if the execution log includes the record
6382 for the next instruction, @value{GDBN} will debug in @dfn{replay
6383 mode}. In the replay mode, the inferior does not really execute code
6384 instructions. Instead, all the events that normally happen during
6385 code execution are taken from the execution log. While code is not
6386 really executed in replay mode, the values of registers (including the
6387 program counter register) and the memory of the inferior are still
6388 changed as they normally would. Their contents are taken from the
6392 If the record for the next instruction is not in the execution log,
6393 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6394 inferior executes normally, and @value{GDBN} records the execution log
6397 The process record and replay target supports reverse execution
6398 (@pxref{Reverse Execution}), even if the platform on which the
6399 inferior runs does not. However, the reverse execution is limited in
6400 this case by the range of the instructions recorded in the execution
6401 log. In other words, reverse execution on platforms that don't
6402 support it directly can only be done in the replay mode.
6404 When debugging in the reverse direction, @value{GDBN} will work in
6405 replay mode as long as the execution log includes the record for the
6406 previous instruction; otherwise, it will work in record mode, if the
6407 platform supports reverse execution, or stop if not.
6409 For architecture environments that support process record and replay,
6410 @value{GDBN} provides the following commands:
6413 @kindex target record
6414 @kindex target record-full
6415 @kindex target record-btrace
6418 @kindex record btrace
6419 @kindex record btrace bts
6420 @kindex record btrace pt
6426 @kindex rec btrace bts
6427 @kindex rec btrace pt
6430 @item record @var{method}
6431 This command starts the process record and replay target. The
6432 recording method can be specified as parameter. Without a parameter
6433 the command uses the @code{full} recording method. The following
6434 recording methods are available:
6438 Full record/replay recording using @value{GDBN}'s software record and
6439 replay implementation. This method allows replaying and reverse
6442 @item btrace @var{format}
6443 Hardware-supported instruction recording. This method does not record
6444 data. Further, the data is collected in a ring buffer so old data will
6445 be overwritten when the buffer is full. It allows limited reverse
6446 execution. Variables and registers are not available during reverse
6449 The recording format can be specified as parameter. Without a parameter
6450 the command chooses the recording format. The following recording
6451 formats are available:
6455 @cindex branch trace store
6456 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
6457 this format, the processor stores a from/to record for each executed
6458 branch in the btrace ring buffer.
6461 @cindex Intel(R) Processor Trace
6462 Use the @dfn{Intel(R) Processor Trace} recording format. In this
6463 format, the processor stores the execution trace in a compressed form
6464 that is afterwards decoded by @value{GDBN}.
6466 The trace can be recorded with very low overhead. The compressed
6467 trace format also allows small trace buffers to already contain a big
6468 number of instructions compared to @acronym{BTS}.
6470 Decoding the recorded execution trace, on the other hand, is more
6471 expensive than decoding @acronym{BTS} trace. This is mostly due to the
6472 increased number of instructions to process. You should increase the
6473 buffer-size with care.
6476 Not all recording formats may be available on all processors.
6479 The process record and replay target can only debug a process that is
6480 already running. Therefore, you need first to start the process with
6481 the @kbd{run} or @kbd{start} commands, and then start the recording
6482 with the @kbd{record @var{method}} command.
6484 @cindex displaced stepping, and process record and replay
6485 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6486 will be automatically disabled when process record and replay target
6487 is started. That's because the process record and replay target
6488 doesn't support displaced stepping.
6490 @cindex non-stop mode, and process record and replay
6491 @cindex asynchronous execution, and process record and replay
6492 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6493 the asynchronous execution mode (@pxref{Background Execution}), not
6494 all recording methods are available. The @code{full} recording method
6495 does not support these two modes.
6500 Stop the process record and replay target. When process record and
6501 replay target stops, the entire execution log will be deleted and the
6502 inferior will either be terminated, or will remain in its final state.
6504 When you stop the process record and replay target in record mode (at
6505 the end of the execution log), the inferior will be stopped at the
6506 next instruction that would have been recorded. In other words, if
6507 you record for a while and then stop recording, the inferior process
6508 will be left in the same state as if the recording never happened.
6510 On the other hand, if the process record and replay target is stopped
6511 while in replay mode (that is, not at the end of the execution log,
6512 but at some earlier point), the inferior process will become ``live''
6513 at that earlier state, and it will then be possible to continue the
6514 usual ``live'' debugging of the process from that state.
6516 When the inferior process exits, or @value{GDBN} detaches from it,
6517 process record and replay target will automatically stop itself.
6521 Go to a specific location in the execution log. There are several
6522 ways to specify the location to go to:
6525 @item record goto begin
6526 @itemx record goto start
6527 Go to the beginning of the execution log.
6529 @item record goto end
6530 Go to the end of the execution log.
6532 @item record goto @var{n}
6533 Go to instruction number @var{n} in the execution log.
6537 @item record save @var{filename}
6538 Save the execution log to a file @file{@var{filename}}.
6539 Default filename is @file{gdb_record.@var{process_id}}, where
6540 @var{process_id} is the process ID of the inferior.
6542 This command may not be available for all recording methods.
6544 @kindex record restore
6545 @item record restore @var{filename}
6546 Restore the execution log from a file @file{@var{filename}}.
6547 File must have been created with @code{record save}.
6549 @kindex set record full
6550 @item set record full insn-number-max @var{limit}
6551 @itemx set record full insn-number-max unlimited
6552 Set the limit of instructions to be recorded for the @code{full}
6553 recording method. Default value is 200000.
6555 If @var{limit} is a positive number, then @value{GDBN} will start
6556 deleting instructions from the log once the number of the record
6557 instructions becomes greater than @var{limit}. For every new recorded
6558 instruction, @value{GDBN} will delete the earliest recorded
6559 instruction to keep the number of recorded instructions at the limit.
6560 (Since deleting recorded instructions loses information, @value{GDBN}
6561 lets you control what happens when the limit is reached, by means of
6562 the @code{stop-at-limit} option, described below.)
6564 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6565 delete recorded instructions from the execution log. The number of
6566 recorded instructions is limited only by the available memory.
6568 @kindex show record full
6569 @item show record full insn-number-max
6570 Show the limit of instructions to be recorded with the @code{full}
6573 @item set record full stop-at-limit
6574 Control the behavior of the @code{full} recording method when the
6575 number of recorded instructions reaches the limit. If ON (the
6576 default), @value{GDBN} will stop when the limit is reached for the
6577 first time and ask you whether you want to stop the inferior or
6578 continue running it and recording the execution log. If you decide
6579 to continue recording, each new recorded instruction will cause the
6580 oldest one to be deleted.
6582 If this option is OFF, @value{GDBN} will automatically delete the
6583 oldest record to make room for each new one, without asking.
6585 @item show record full stop-at-limit
6586 Show the current setting of @code{stop-at-limit}.
6588 @item set record full memory-query
6589 Control the behavior when @value{GDBN} is unable to record memory
6590 changes caused by an instruction for the @code{full} recording method.
6591 If ON, @value{GDBN} will query whether to stop the inferior in that
6594 If this option is OFF (the default), @value{GDBN} will automatically
6595 ignore the effect of such instructions on memory. Later, when
6596 @value{GDBN} replays this execution log, it will mark the log of this
6597 instruction as not accessible, and it will not affect the replay
6600 @item show record full memory-query
6601 Show the current setting of @code{memory-query}.
6603 @kindex set record btrace
6604 The @code{btrace} record target does not trace data. As a
6605 convenience, when replaying, @value{GDBN} reads read-only memory off
6606 the live program directly, assuming that the addresses of the
6607 read-only areas don't change. This for example makes it possible to
6608 disassemble code while replaying, but not to print variables.
6609 In some cases, being able to inspect variables might be useful.
6610 You can use the following command for that:
6612 @item set record btrace replay-memory-access
6613 Control the behavior of the @code{btrace} recording method when
6614 accessing memory during replay. If @code{read-only} (the default),
6615 @value{GDBN} will only allow accesses to read-only memory.
6616 If @code{read-write}, @value{GDBN} will allow accesses to read-only
6617 and to read-write memory. Beware that the accessed memory corresponds
6618 to the live target and not necessarily to the current replay
6621 @kindex show record btrace
6622 @item show record btrace replay-memory-access
6623 Show the current setting of @code{replay-memory-access}.
6625 @kindex set record btrace bts
6626 @item set record btrace bts buffer-size @var{size}
6627 @itemx set record btrace bts buffer-size unlimited
6628 Set the requested ring buffer size for branch tracing in @acronym{BTS}
6629 format. Default is 64KB.
6631 If @var{size} is a positive number, then @value{GDBN} will try to
6632 allocate a buffer of at least @var{size} bytes for each new thread
6633 that uses the btrace recording method and the @acronym{BTS} format.
6634 The actually obtained buffer size may differ from the requested
6635 @var{size}. Use the @code{info record} command to see the actual
6636 buffer size for each thread that uses the btrace recording method and
6637 the @acronym{BTS} format.
6639 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6640 allocate a buffer of 4MB.
6642 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6643 also need longer to process the branch trace data before it can be used.
6645 @item show record btrace bts buffer-size @var{size}
6646 Show the current setting of the requested ring buffer size for branch
6647 tracing in @acronym{BTS} format.
6649 @kindex set record btrace pt
6650 @item set record btrace pt buffer-size @var{size}
6651 @itemx set record btrace pt buffer-size unlimited
6652 Set the requested ring buffer size for branch tracing in Intel(R)
6653 Processor Trace format. Default is 16KB.
6655 If @var{size} is a positive number, then @value{GDBN} will try to
6656 allocate a buffer of at least @var{size} bytes for each new thread
6657 that uses the btrace recording method and the Intel(R) Processor Trace
6658 format. The actually obtained buffer size may differ from the
6659 requested @var{size}. Use the @code{info record} command to see the
6660 actual buffer size for each thread.
6662 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6663 allocate a buffer of 4MB.
6665 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6666 also need longer to process the branch trace data before it can be used.
6668 @item show record btrace pt buffer-size @var{size}
6669 Show the current setting of the requested ring buffer size for branch
6670 tracing in Intel(R) Processor Trace format.
6674 Show various statistics about the recording depending on the recording
6679 For the @code{full} recording method, it shows the state of process
6680 record and its in-memory execution log buffer, including:
6684 Whether in record mode or replay mode.
6686 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6688 Highest recorded instruction number.
6690 Current instruction about to be replayed (if in replay mode).
6692 Number of instructions contained in the execution log.
6694 Maximum number of instructions that may be contained in the execution log.
6698 For the @code{btrace} recording method, it shows:
6704 Number of instructions that have been recorded.
6706 Number of blocks of sequential control-flow formed by the recorded
6709 Whether in record mode or replay mode.
6712 For the @code{bts} recording format, it also shows:
6715 Size of the perf ring buffer.
6718 For the @code{pt} recording format, it also shows:
6721 Size of the perf ring buffer.
6725 @kindex record delete
6728 When record target runs in replay mode (``in the past''), delete the
6729 subsequent execution log and begin to record a new execution log starting
6730 from the current address. This means you will abandon the previously
6731 recorded ``future'' and begin recording a new ``future''.
6733 @kindex record instruction-history
6734 @kindex rec instruction-history
6735 @item record instruction-history
6736 Disassembles instructions from the recorded execution log. By
6737 default, ten instructions are disassembled. This can be changed using
6738 the @code{set record instruction-history-size} command. Instructions
6739 are printed in execution order.
6741 Speculatively executed instructions are prefixed with @samp{?}. This
6742 feature is not available for all recording formats.
6744 There are several ways to specify what part of the execution log to
6748 @item record instruction-history @var{insn}
6749 Disassembles ten instructions starting from instruction number
6752 @item record instruction-history @var{insn}, +/-@var{n}
6753 Disassembles @var{n} instructions around instruction number
6754 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
6755 @var{n} instructions after instruction number @var{insn}. If
6756 @var{n} is preceded with @code{-}, disassembles @var{n}
6757 instructions before instruction number @var{insn}.
6759 @item record instruction-history
6760 Disassembles ten more instructions after the last disassembly.
6762 @item record instruction-history -
6763 Disassembles ten more instructions before the last disassembly.
6765 @item record instruction-history @var{begin} @var{end}
6766 Disassembles instructions beginning with instruction number
6767 @var{begin} until instruction number @var{end}. The instruction
6768 number @var{end} is included.
6771 This command may not be available for all recording methods.
6774 @item set record instruction-history-size @var{size}
6775 @itemx set record instruction-history-size unlimited
6776 Define how many instructions to disassemble in the @code{record
6777 instruction-history} command. The default value is 10.
6778 A @var{size} of @code{unlimited} means unlimited instructions.
6781 @item show record instruction-history-size
6782 Show how many instructions to disassemble in the @code{record
6783 instruction-history} command.
6785 @kindex record function-call-history
6786 @kindex rec function-call-history
6787 @item record function-call-history
6788 Prints the execution history at function granularity. It prints one
6789 line for each sequence of instructions that belong to the same
6790 function giving the name of that function, the source lines
6791 for this instruction sequence (if the @code{/l} modifier is
6792 specified), and the instructions numbers that form the sequence (if
6793 the @code{/i} modifier is specified). The function names are indented
6794 to reflect the call stack depth if the @code{/c} modifier is
6795 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
6799 (@value{GDBP}) @b{list 1, 10}
6810 (@value{GDBP}) @b{record function-call-history /ilc}
6811 1 bar inst 1,4 at foo.c:6,8
6812 2 foo inst 5,10 at foo.c:2,3
6813 3 bar inst 11,13 at foo.c:9,10
6816 By default, ten lines are printed. This can be changed using the
6817 @code{set record function-call-history-size} command. Functions are
6818 printed in execution order. There are several ways to specify what
6822 @item record function-call-history @var{func}
6823 Prints ten functions starting from function number @var{func}.
6825 @item record function-call-history @var{func}, +/-@var{n}
6826 Prints @var{n} functions around function number @var{func}. If
6827 @var{n} is preceded with @code{+}, prints @var{n} functions after
6828 function number @var{func}. If @var{n} is preceded with @code{-},
6829 prints @var{n} functions before function number @var{func}.
6831 @item record function-call-history
6832 Prints ten more functions after the last ten-line print.
6834 @item record function-call-history -
6835 Prints ten more functions before the last ten-line print.
6837 @item record function-call-history @var{begin} @var{end}
6838 Prints functions beginning with function number @var{begin} until
6839 function number @var{end}. The function number @var{end} is included.
6842 This command may not be available for all recording methods.
6844 @item set record function-call-history-size @var{size}
6845 @itemx set record function-call-history-size unlimited
6846 Define how many lines to print in the
6847 @code{record function-call-history} command. The default value is 10.
6848 A size of @code{unlimited} means unlimited lines.
6850 @item show record function-call-history-size
6851 Show how many lines to print in the
6852 @code{record function-call-history} command.
6857 @chapter Examining the Stack
6859 When your program has stopped, the first thing you need to know is where it
6860 stopped and how it got there.
6863 Each time your program performs a function call, information about the call
6865 That information includes the location of the call in your program,
6866 the arguments of the call,
6867 and the local variables of the function being called.
6868 The information is saved in a block of data called a @dfn{stack frame}.
6869 The stack frames are allocated in a region of memory called the @dfn{call
6872 When your program stops, the @value{GDBN} commands for examining the
6873 stack allow you to see all of this information.
6875 @cindex selected frame
6876 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6877 @value{GDBN} commands refer implicitly to the selected frame. In
6878 particular, whenever you ask @value{GDBN} for the value of a variable in
6879 your program, the value is found in the selected frame. There are
6880 special @value{GDBN} commands to select whichever frame you are
6881 interested in. @xref{Selection, ,Selecting a Frame}.
6883 When your program stops, @value{GDBN} automatically selects the
6884 currently executing frame and describes it briefly, similar to the
6885 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6888 * Frames:: Stack frames
6889 * Backtrace:: Backtraces
6890 * Frame Filter Management:: Managing frame filters
6891 * Selection:: Selecting a frame
6892 * Frame Info:: Information on a frame
6897 @section Stack Frames
6899 @cindex frame, definition
6901 The call stack is divided up into contiguous pieces called @dfn{stack
6902 frames}, or @dfn{frames} for short; each frame is the data associated
6903 with one call to one function. The frame contains the arguments given
6904 to the function, the function's local variables, and the address at
6905 which the function is executing.
6907 @cindex initial frame
6908 @cindex outermost frame
6909 @cindex innermost frame
6910 When your program is started, the stack has only one frame, that of the
6911 function @code{main}. This is called the @dfn{initial} frame or the
6912 @dfn{outermost} frame. Each time a function is called, a new frame is
6913 made. Each time a function returns, the frame for that function invocation
6914 is eliminated. If a function is recursive, there can be many frames for
6915 the same function. The frame for the function in which execution is
6916 actually occurring is called the @dfn{innermost} frame. This is the most
6917 recently created of all the stack frames that still exist.
6919 @cindex frame pointer
6920 Inside your program, stack frames are identified by their addresses. A
6921 stack frame consists of many bytes, each of which has its own address; each
6922 kind of computer has a convention for choosing one byte whose
6923 address serves as the address of the frame. Usually this address is kept
6924 in a register called the @dfn{frame pointer register}
6925 (@pxref{Registers, $fp}) while execution is going on in that frame.
6927 @cindex frame number
6928 @value{GDBN} assigns numbers to all existing stack frames, starting with
6929 zero for the innermost frame, one for the frame that called it,
6930 and so on upward. These numbers do not really exist in your program;
6931 they are assigned by @value{GDBN} to give you a way of designating stack
6932 frames in @value{GDBN} commands.
6934 @c The -fomit-frame-pointer below perennially causes hbox overflow
6935 @c underflow problems.
6936 @cindex frameless execution
6937 Some compilers provide a way to compile functions so that they operate
6938 without stack frames. (For example, the @value{NGCC} option
6940 @samp{-fomit-frame-pointer}
6942 generates functions without a frame.)
6943 This is occasionally done with heavily used library functions to save
6944 the frame setup time. @value{GDBN} has limited facilities for dealing
6945 with these function invocations. If the innermost function invocation
6946 has no stack frame, @value{GDBN} nevertheless regards it as though
6947 it had a separate frame, which is numbered zero as usual, allowing
6948 correct tracing of the function call chain. However, @value{GDBN} has
6949 no provision for frameless functions elsewhere in the stack.
6952 @kindex frame@r{, command}
6953 @cindex current stack frame
6954 @item frame @r{[}@var{framespec}@r{]}
6955 The @code{frame} command allows you to move from one stack frame to another,
6956 and to print the stack frame you select. The @var{framespec} may be either the
6957 address of the frame or the stack frame number. Without an argument,
6958 @code{frame} prints the current stack frame.
6960 @kindex select-frame
6961 @cindex selecting frame silently
6963 The @code{select-frame} command allows you to move from one stack frame
6964 to another without printing the frame. This is the silent version of
6972 @cindex call stack traces
6973 A backtrace is a summary of how your program got where it is. It shows one
6974 line per frame, for many frames, starting with the currently executing
6975 frame (frame zero), followed by its caller (frame one), and on up the
6978 @anchor{backtrace-command}
6981 @kindex bt @r{(@code{backtrace})}
6984 Print a backtrace of the entire stack: one line per frame for all
6985 frames in the stack.
6987 You can stop the backtrace at any time by typing the system interrupt
6988 character, normally @kbd{Ctrl-c}.
6990 @item backtrace @var{n}
6992 Similar, but print only the innermost @var{n} frames.
6994 @item backtrace -@var{n}
6996 Similar, but print only the outermost @var{n} frames.
6998 @item backtrace full
7000 @itemx bt full @var{n}
7001 @itemx bt full -@var{n}
7002 Print the values of the local variables also. As described above,
7003 @var{n} specifies the number of frames to print.
7005 @item backtrace no-filters
7006 @itemx bt no-filters
7007 @itemx bt no-filters @var{n}
7008 @itemx bt no-filters -@var{n}
7009 @itemx bt no-filters full
7010 @itemx bt no-filters full @var{n}
7011 @itemx bt no-filters full -@var{n}
7012 Do not run Python frame filters on this backtrace. @xref{Frame
7013 Filter API}, for more information. Additionally use @ref{disable
7014 frame-filter all} to turn off all frame filters. This is only
7015 relevant when @value{GDBN} has been configured with @code{Python}
7021 The names @code{where} and @code{info stack} (abbreviated @code{info s})
7022 are additional aliases for @code{backtrace}.
7024 @cindex multiple threads, backtrace
7025 In a multi-threaded program, @value{GDBN} by default shows the
7026 backtrace only for the current thread. To display the backtrace for
7027 several or all of the threads, use the command @code{thread apply}
7028 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
7029 apply all backtrace}, @value{GDBN} will display the backtrace for all
7030 the threads; this is handy when you debug a core dump of a
7031 multi-threaded program.
7033 Each line in the backtrace shows the frame number and the function name.
7034 The program counter value is also shown---unless you use @code{set
7035 print address off}. The backtrace also shows the source file name and
7036 line number, as well as the arguments to the function. The program
7037 counter value is omitted if it is at the beginning of the code for that
7040 Here is an example of a backtrace. It was made with the command
7041 @samp{bt 3}, so it shows the innermost three frames.
7045 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7047 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
7048 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
7050 (More stack frames follow...)
7055 The display for frame zero does not begin with a program counter
7056 value, indicating that your program has stopped at the beginning of the
7057 code for line @code{993} of @code{builtin.c}.
7060 The value of parameter @code{data} in frame 1 has been replaced by
7061 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
7062 only if it is a scalar (integer, pointer, enumeration, etc). See command
7063 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
7064 on how to configure the way function parameter values are printed.
7066 @cindex optimized out, in backtrace
7067 @cindex function call arguments, optimized out
7068 If your program was compiled with optimizations, some compilers will
7069 optimize away arguments passed to functions if those arguments are
7070 never used after the call. Such optimizations generate code that
7071 passes arguments through registers, but doesn't store those arguments
7072 in the stack frame. @value{GDBN} has no way of displaying such
7073 arguments in stack frames other than the innermost one. Here's what
7074 such a backtrace might look like:
7078 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7080 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
7081 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
7083 (More stack frames follow...)
7088 The values of arguments that were not saved in their stack frames are
7089 shown as @samp{<optimized out>}.
7091 If you need to display the values of such optimized-out arguments,
7092 either deduce that from other variables whose values depend on the one
7093 you are interested in, or recompile without optimizations.
7095 @cindex backtrace beyond @code{main} function
7096 @cindex program entry point
7097 @cindex startup code, and backtrace
7098 Most programs have a standard user entry point---a place where system
7099 libraries and startup code transition into user code. For C this is
7100 @code{main}@footnote{
7101 Note that embedded programs (the so-called ``free-standing''
7102 environment) are not required to have a @code{main} function as the
7103 entry point. They could even have multiple entry points.}.
7104 When @value{GDBN} finds the entry function in a backtrace
7105 it will terminate the backtrace, to avoid tracing into highly
7106 system-specific (and generally uninteresting) code.
7108 If you need to examine the startup code, or limit the number of levels
7109 in a backtrace, you can change this behavior:
7112 @item set backtrace past-main
7113 @itemx set backtrace past-main on
7114 @kindex set backtrace
7115 Backtraces will continue past the user entry point.
7117 @item set backtrace past-main off
7118 Backtraces will stop when they encounter the user entry point. This is the
7121 @item show backtrace past-main
7122 @kindex show backtrace
7123 Display the current user entry point backtrace policy.
7125 @item set backtrace past-entry
7126 @itemx set backtrace past-entry on
7127 Backtraces will continue past the internal entry point of an application.
7128 This entry point is encoded by the linker when the application is built,
7129 and is likely before the user entry point @code{main} (or equivalent) is called.
7131 @item set backtrace past-entry off
7132 Backtraces will stop when they encounter the internal entry point of an
7133 application. This is the default.
7135 @item show backtrace past-entry
7136 Display the current internal entry point backtrace policy.
7138 @item set backtrace limit @var{n}
7139 @itemx set backtrace limit 0
7140 @itemx set backtrace limit unlimited
7141 @cindex backtrace limit
7142 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
7143 or zero means unlimited levels.
7145 @item show backtrace limit
7146 Display the current limit on backtrace levels.
7149 You can control how file names are displayed.
7152 @item set filename-display
7153 @itemx set filename-display relative
7154 @cindex filename-display
7155 Display file names relative to the compilation directory. This is the default.
7157 @item set filename-display basename
7158 Display only basename of a filename.
7160 @item set filename-display absolute
7161 Display an absolute filename.
7163 @item show filename-display
7164 Show the current way to display filenames.
7167 @node Frame Filter Management
7168 @section Management of Frame Filters.
7169 @cindex managing frame filters
7171 Frame filters are Python based utilities to manage and decorate the
7172 output of frames. @xref{Frame Filter API}, for further information.
7174 Managing frame filters is performed by several commands available
7175 within @value{GDBN}, detailed here.
7178 @kindex info frame-filter
7179 @item info frame-filter
7180 Print a list of installed frame filters from all dictionaries, showing
7181 their name, priority and enabled status.
7183 @kindex disable frame-filter
7184 @anchor{disable frame-filter all}
7185 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
7186 Disable a frame filter in the dictionary matching
7187 @var{filter-dictionary} and @var{filter-name}. The
7188 @var{filter-dictionary} may be @code{all}, @code{global},
7189 @code{progspace}, or the name of the object file where the frame filter
7190 dictionary resides. When @code{all} is specified, all frame filters
7191 across all dictionaries are disabled. The @var{filter-name} is the name
7192 of the frame filter and is used when @code{all} is not the option for
7193 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
7194 may be enabled again later.
7196 @kindex enable frame-filter
7197 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
7198 Enable a frame filter in the dictionary matching
7199 @var{filter-dictionary} and @var{filter-name}. The
7200 @var{filter-dictionary} may be @code{all}, @code{global},
7201 @code{progspace} or the name of the object file where the frame filter
7202 dictionary resides. When @code{all} is specified, all frame filters across
7203 all dictionaries are enabled. The @var{filter-name} is the name of the frame
7204 filter and is used when @code{all} is not the option for
7205 @var{filter-dictionary}.
7210 (gdb) info frame-filter
7212 global frame-filters:
7213 Priority Enabled Name
7214 1000 No PrimaryFunctionFilter
7217 progspace /build/test frame-filters:
7218 Priority Enabled Name
7219 100 Yes ProgspaceFilter
7221 objfile /build/test frame-filters:
7222 Priority Enabled Name
7223 999 Yes BuildProgra Filter
7225 (gdb) disable frame-filter /build/test BuildProgramFilter
7226 (gdb) info frame-filter
7228 global frame-filters:
7229 Priority Enabled Name
7230 1000 No PrimaryFunctionFilter
7233 progspace /build/test frame-filters:
7234 Priority Enabled Name
7235 100 Yes ProgspaceFilter
7237 objfile /build/test frame-filters:
7238 Priority Enabled Name
7239 999 No BuildProgramFilter
7241 (gdb) enable frame-filter global PrimaryFunctionFilter
7242 (gdb) info frame-filter
7244 global frame-filters:
7245 Priority Enabled Name
7246 1000 Yes PrimaryFunctionFilter
7249 progspace /build/test frame-filters:
7250 Priority Enabled Name
7251 100 Yes ProgspaceFilter
7253 objfile /build/test frame-filters:
7254 Priority Enabled Name
7255 999 No BuildProgramFilter
7258 @kindex set frame-filter priority
7259 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
7260 Set the @var{priority} of a frame filter in the dictionary matching
7261 @var{filter-dictionary}, and the frame filter name matching
7262 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7263 @code{progspace} or the name of the object file where the frame filter
7264 dictionary resides. The @var{priority} is an integer.
7266 @kindex show frame-filter priority
7267 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
7268 Show the @var{priority} of a frame filter in the dictionary matching
7269 @var{filter-dictionary}, and the frame filter name matching
7270 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7271 @code{progspace} or the name of the object file where the frame filter
7277 (gdb) info frame-filter
7279 global frame-filters:
7280 Priority Enabled Name
7281 1000 Yes PrimaryFunctionFilter
7284 progspace /build/test frame-filters:
7285 Priority Enabled Name
7286 100 Yes ProgspaceFilter
7288 objfile /build/test frame-filters:
7289 Priority Enabled Name
7290 999 No BuildProgramFilter
7292 (gdb) set frame-filter priority global Reverse 50
7293 (gdb) info frame-filter
7295 global frame-filters:
7296 Priority Enabled Name
7297 1000 Yes PrimaryFunctionFilter
7300 progspace /build/test frame-filters:
7301 Priority Enabled Name
7302 100 Yes ProgspaceFilter
7304 objfile /build/test frame-filters:
7305 Priority Enabled Name
7306 999 No BuildProgramFilter
7311 @section Selecting a Frame
7313 Most commands for examining the stack and other data in your program work on
7314 whichever stack frame is selected at the moment. Here are the commands for
7315 selecting a stack frame; all of them finish by printing a brief description
7316 of the stack frame just selected.
7319 @kindex frame@r{, selecting}
7320 @kindex f @r{(@code{frame})}
7323 Select frame number @var{n}. Recall that frame zero is the innermost
7324 (currently executing) frame, frame one is the frame that called the
7325 innermost one, and so on. The highest-numbered frame is the one for
7328 @item frame @var{stack-addr} [ @var{pc-addr} ]
7329 @itemx f @var{stack-addr} [ @var{pc-addr} ]
7330 Select the frame at address @var{stack-addr}. This is useful mainly if the
7331 chaining of stack frames has been damaged by a bug, making it
7332 impossible for @value{GDBN} to assign numbers properly to all frames. In
7333 addition, this can be useful when your program has multiple stacks and
7334 switches between them. The optional @var{pc-addr} can also be given to
7335 specify the value of PC for the stack frame.
7339 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
7340 numbers @var{n}, this advances toward the outermost frame, to higher
7341 frame numbers, to frames that have existed longer.
7344 @kindex do @r{(@code{down})}
7346 Move @var{n} frames down the stack; @var{n} defaults to 1. For
7347 positive numbers @var{n}, this advances toward the innermost frame, to
7348 lower frame numbers, to frames that were created more recently.
7349 You may abbreviate @code{down} as @code{do}.
7352 All of these commands end by printing two lines of output describing the
7353 frame. The first line shows the frame number, the function name, the
7354 arguments, and the source file and line number of execution in that
7355 frame. The second line shows the text of that source line.
7363 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7365 10 read_input_file (argv[i]);
7369 After such a printout, the @code{list} command with no arguments
7370 prints ten lines centered on the point of execution in the frame.
7371 You can also edit the program at the point of execution with your favorite
7372 editing program by typing @code{edit}.
7373 @xref{List, ,Printing Source Lines},
7377 @kindex down-silently
7379 @item up-silently @var{n}
7380 @itemx down-silently @var{n}
7381 These two commands are variants of @code{up} and @code{down},
7382 respectively; they differ in that they do their work silently, without
7383 causing display of the new frame. They are intended primarily for use
7384 in @value{GDBN} command scripts, where the output might be unnecessary and
7389 @section Information About a Frame
7391 There are several other commands to print information about the selected
7397 When used without any argument, this command does not change which
7398 frame is selected, but prints a brief description of the currently
7399 selected stack frame. It can be abbreviated @code{f}. With an
7400 argument, this command is used to select a stack frame.
7401 @xref{Selection, ,Selecting a Frame}.
7404 @kindex info f @r{(@code{info frame})}
7407 This command prints a verbose description of the selected stack frame,
7412 the address of the frame
7414 the address of the next frame down (called by this frame)
7416 the address of the next frame up (caller of this frame)
7418 the language in which the source code corresponding to this frame is written
7420 the address of the frame's arguments
7422 the address of the frame's local variables
7424 the program counter saved in it (the address of execution in the caller frame)
7426 which registers were saved in the frame
7429 @noindent The verbose description is useful when
7430 something has gone wrong that has made the stack format fail to fit
7431 the usual conventions.
7433 @item info frame @var{addr}
7434 @itemx info f @var{addr}
7435 Print a verbose description of the frame at address @var{addr}, without
7436 selecting that frame. The selected frame remains unchanged by this
7437 command. This requires the same kind of address (more than one for some
7438 architectures) that you specify in the @code{frame} command.
7439 @xref{Selection, ,Selecting a Frame}.
7443 Print the arguments of the selected frame, each on a separate line.
7447 Print the local variables of the selected frame, each on a separate
7448 line. These are all variables (declared either static or automatic)
7449 accessible at the point of execution of the selected frame.
7455 @chapter Examining Source Files
7457 @value{GDBN} can print parts of your program's source, since the debugging
7458 information recorded in the program tells @value{GDBN} what source files were
7459 used to build it. When your program stops, @value{GDBN} spontaneously prints
7460 the line where it stopped. Likewise, when you select a stack frame
7461 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7462 execution in that frame has stopped. You can print other portions of
7463 source files by explicit command.
7465 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7466 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7467 @value{GDBN} under @sc{gnu} Emacs}.
7470 * List:: Printing source lines
7471 * Specify Location:: How to specify code locations
7472 * Edit:: Editing source files
7473 * Search:: Searching source files
7474 * Source Path:: Specifying source directories
7475 * Machine Code:: Source and machine code
7479 @section Printing Source Lines
7482 @kindex l @r{(@code{list})}
7483 To print lines from a source file, use the @code{list} command
7484 (abbreviated @code{l}). By default, ten lines are printed.
7485 There are several ways to specify what part of the file you want to
7486 print; see @ref{Specify Location}, for the full list.
7488 Here are the forms of the @code{list} command most commonly used:
7491 @item list @var{linenum}
7492 Print lines centered around line number @var{linenum} in the
7493 current source file.
7495 @item list @var{function}
7496 Print lines centered around the beginning of function
7500 Print more lines. If the last lines printed were printed with a
7501 @code{list} command, this prints lines following the last lines
7502 printed; however, if the last line printed was a solitary line printed
7503 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7504 Stack}), this prints lines centered around that line.
7507 Print lines just before the lines last printed.
7510 @cindex @code{list}, how many lines to display
7511 By default, @value{GDBN} prints ten source lines with any of these forms of
7512 the @code{list} command. You can change this using @code{set listsize}:
7515 @kindex set listsize
7516 @item set listsize @var{count}
7517 @itemx set listsize unlimited
7518 Make the @code{list} command display @var{count} source lines (unless
7519 the @code{list} argument explicitly specifies some other number).
7520 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7522 @kindex show listsize
7524 Display the number of lines that @code{list} prints.
7527 Repeating a @code{list} command with @key{RET} discards the argument,
7528 so it is equivalent to typing just @code{list}. This is more useful
7529 than listing the same lines again. An exception is made for an
7530 argument of @samp{-}; that argument is preserved in repetition so that
7531 each repetition moves up in the source file.
7533 In general, the @code{list} command expects you to supply zero, one or two
7534 @dfn{locations}. Locations specify source lines; there are several ways
7535 of writing them (@pxref{Specify Location}), but the effect is always
7536 to specify some source line.
7538 Here is a complete description of the possible arguments for @code{list}:
7541 @item list @var{location}
7542 Print lines centered around the line specified by @var{location}.
7544 @item list @var{first},@var{last}
7545 Print lines from @var{first} to @var{last}. Both arguments are
7546 locations. When a @code{list} command has two locations, and the
7547 source file of the second location is omitted, this refers to
7548 the same source file as the first location.
7550 @item list ,@var{last}
7551 Print lines ending with @var{last}.
7553 @item list @var{first},
7554 Print lines starting with @var{first}.
7557 Print lines just after the lines last printed.
7560 Print lines just before the lines last printed.
7563 As described in the preceding table.
7566 @node Specify Location
7567 @section Specifying a Location
7568 @cindex specifying location
7570 @cindex source location
7573 * Linespec Locations:: Linespec locations
7574 * Explicit Locations:: Explicit locations
7575 * Address Locations:: Address locations
7578 Several @value{GDBN} commands accept arguments that specify a location
7579 of your program's code. Since @value{GDBN} is a source-level
7580 debugger, a location usually specifies some line in the source code.
7581 Locations may be specified using three different formats:
7582 linespec locations, explicit locations, or address locations.
7584 @node Linespec Locations
7585 @subsection Linespec Locations
7586 @cindex linespec locations
7588 A @dfn{linespec} is a colon-separated list of source location parameters such
7589 as file name, function name, etc. Here are all the different ways of
7590 specifying a linespec:
7594 Specifies the line number @var{linenum} of the current source file.
7597 @itemx +@var{offset}
7598 Specifies the line @var{offset} lines before or after the @dfn{current
7599 line}. For the @code{list} command, the current line is the last one
7600 printed; for the breakpoint commands, this is the line at which
7601 execution stopped in the currently selected @dfn{stack frame}
7602 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7603 used as the second of the two linespecs in a @code{list} command,
7604 this specifies the line @var{offset} lines up or down from the first
7607 @item @var{filename}:@var{linenum}
7608 Specifies the line @var{linenum} in the source file @var{filename}.
7609 If @var{filename} is a relative file name, then it will match any
7610 source file name with the same trailing components. For example, if
7611 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7612 name of @file{/build/trunk/gcc/expr.c}, but not
7613 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7615 @item @var{function}
7616 Specifies the line that begins the body of the function @var{function}.
7617 For example, in C, this is the line with the open brace.
7619 @item @var{function}:@var{label}
7620 Specifies the line where @var{label} appears in @var{function}.
7622 @item @var{filename}:@var{function}
7623 Specifies the line that begins the body of the function @var{function}
7624 in the file @var{filename}. You only need the file name with a
7625 function name to avoid ambiguity when there are identically named
7626 functions in different source files.
7629 Specifies the line at which the label named @var{label} appears
7630 in the function corresponding to the currently selected stack frame.
7631 If there is no current selected stack frame (for instance, if the inferior
7632 is not running), then @value{GDBN} will not search for a label.
7634 @cindex breakpoint at static probe point
7635 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7636 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7637 applications to embed static probes. @xref{Static Probe Points}, for more
7638 information on finding and using static probes. This form of linespec
7639 specifies the location of such a static probe.
7641 If @var{objfile} is given, only probes coming from that shared library
7642 or executable matching @var{objfile} as a regular expression are considered.
7643 If @var{provider} is given, then only probes from that provider are considered.
7644 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7645 each one of those probes.
7648 @node Explicit Locations
7649 @subsection Explicit Locations
7650 @cindex explicit locations
7652 @dfn{Explicit locations} allow the user to directly specify the source
7653 location's parameters using option-value pairs.
7655 Explicit locations are useful when several functions, labels, or
7656 file names have the same name (base name for files) in the program's
7657 sources. In these cases, explicit locations point to the source
7658 line you meant more accurately and unambiguously. Also, using
7659 explicit locations might be faster in large programs.
7661 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
7662 defined in the file named @file{foo} or the label @code{bar} in a function
7663 named @code{foo}. @value{GDBN} must search either the file system or
7664 the symbol table to know.
7666 The list of valid explicit location options is summarized in the
7670 @item -source @var{filename}
7671 The value specifies the source file name. To differentiate between
7672 files with the same base name, prepend as many directories as is necessary
7673 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
7674 @value{GDBN} will use the first file it finds with the given base
7675 name. This option requires the use of either @code{-function} or @code{-line}.
7677 @item -function @var{function}
7678 The value specifies the name of a function. Operations
7679 on function locations unmodified by other options (such as @code{-label}
7680 or @code{-line}) refer to the line that begins the body of the function.
7681 In C, for example, this is the line with the open brace.
7683 @item -label @var{label}
7684 The value specifies the name of a label. When the function
7685 name is not specified, the label is searched in the function of the currently
7686 selected stack frame.
7688 @item -line @var{number}
7689 The value specifies a line offset for the location. The offset may either
7690 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
7691 the command. When specified without any other options, the line offset is
7692 relative to the current line.
7695 Explicit location options may be abbreviated by omitting any non-unique
7696 trailing characters from the option name, e.g., @code{break -s main.c -li 3}.
7698 @node Address Locations
7699 @subsection Address Locations
7700 @cindex address locations
7702 @dfn{Address locations} indicate a specific program address. They have
7703 the generalized form *@var{address}.
7705 For line-oriented commands, such as @code{list} and @code{edit}, this
7706 specifies a source line that contains @var{address}. For @code{break} and
7707 other breakpoint-oriented commands, this can be used to set breakpoints in
7708 parts of your program which do not have debugging information or
7711 Here @var{address} may be any expression valid in the current working
7712 language (@pxref{Languages, working language}) that specifies a code
7713 address. In addition, as a convenience, @value{GDBN} extends the
7714 semantics of expressions used in locations to cover several situations
7715 that frequently occur during debugging. Here are the various forms
7719 @item @var{expression}
7720 Any expression valid in the current working language.
7722 @item @var{funcaddr}
7723 An address of a function or procedure derived from its name. In C,
7724 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
7725 simply the function's name @var{function} (and actually a special case
7726 of a valid expression). In Pascal and Modula-2, this is
7727 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
7728 (although the Pascal form also works).
7730 This form specifies the address of the function's first instruction,
7731 before the stack frame and arguments have been set up.
7733 @item '@var{filename}':@var{funcaddr}
7734 Like @var{funcaddr} above, but also specifies the name of the source
7735 file explicitly. This is useful if the name of the function does not
7736 specify the function unambiguously, e.g., if there are several
7737 functions with identical names in different source files.
7741 @section Editing Source Files
7742 @cindex editing source files
7745 @kindex e @r{(@code{edit})}
7746 To edit the lines in a source file, use the @code{edit} command.
7747 The editing program of your choice
7748 is invoked with the current line set to
7749 the active line in the program.
7750 Alternatively, there are several ways to specify what part of the file you
7751 want to print if you want to see other parts of the program:
7754 @item edit @var{location}
7755 Edit the source file specified by @code{location}. Editing starts at
7756 that @var{location}, e.g., at the specified source line of the
7757 specified file. @xref{Specify Location}, for all the possible forms
7758 of the @var{location} argument; here are the forms of the @code{edit}
7759 command most commonly used:
7762 @item edit @var{number}
7763 Edit the current source file with @var{number} as the active line number.
7765 @item edit @var{function}
7766 Edit the file containing @var{function} at the beginning of its definition.
7771 @subsection Choosing your Editor
7772 You can customize @value{GDBN} to use any editor you want
7774 The only restriction is that your editor (say @code{ex}), recognizes the
7775 following command-line syntax:
7777 ex +@var{number} file
7779 The optional numeric value +@var{number} specifies the number of the line in
7780 the file where to start editing.}.
7781 By default, it is @file{@value{EDITOR}}, but you can change this
7782 by setting the environment variable @code{EDITOR} before using
7783 @value{GDBN}. For example, to configure @value{GDBN} to use the
7784 @code{vi} editor, you could use these commands with the @code{sh} shell:
7790 or in the @code{csh} shell,
7792 setenv EDITOR /usr/bin/vi
7797 @section Searching Source Files
7798 @cindex searching source files
7800 There are two commands for searching through the current source file for a
7805 @kindex forward-search
7806 @kindex fo @r{(@code{forward-search})}
7807 @item forward-search @var{regexp}
7808 @itemx search @var{regexp}
7809 The command @samp{forward-search @var{regexp}} checks each line,
7810 starting with the one following the last line listed, for a match for
7811 @var{regexp}. It lists the line that is found. You can use the
7812 synonym @samp{search @var{regexp}} or abbreviate the command name as
7815 @kindex reverse-search
7816 @item reverse-search @var{regexp}
7817 The command @samp{reverse-search @var{regexp}} checks each line, starting
7818 with the one before the last line listed and going backward, for a match
7819 for @var{regexp}. It lists the line that is found. You can abbreviate
7820 this command as @code{rev}.
7824 @section Specifying Source Directories
7827 @cindex directories for source files
7828 Executable programs sometimes do not record the directories of the source
7829 files from which they were compiled, just the names. Even when they do,
7830 the directories could be moved between the compilation and your debugging
7831 session. @value{GDBN} has a list of directories to search for source files;
7832 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
7833 it tries all the directories in the list, in the order they are present
7834 in the list, until it finds a file with the desired name.
7836 For example, suppose an executable references the file
7837 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
7838 @file{/mnt/cross}. The file is first looked up literally; if this
7839 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
7840 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
7841 message is printed. @value{GDBN} does not look up the parts of the
7842 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
7843 Likewise, the subdirectories of the source path are not searched: if
7844 the source path is @file{/mnt/cross}, and the binary refers to
7845 @file{foo.c}, @value{GDBN} would not find it under
7846 @file{/mnt/cross/usr/src/foo-1.0/lib}.
7848 Plain file names, relative file names with leading directories, file
7849 names containing dots, etc.@: are all treated as described above; for
7850 instance, if the source path is @file{/mnt/cross}, and the source file
7851 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
7852 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
7853 that---@file{/mnt/cross/foo.c}.
7855 Note that the executable search path is @emph{not} used to locate the
7858 Whenever you reset or rearrange the source path, @value{GDBN} clears out
7859 any information it has cached about where source files are found and where
7860 each line is in the file.
7864 When you start @value{GDBN}, its source path includes only @samp{cdir}
7865 and @samp{cwd}, in that order.
7866 To add other directories, use the @code{directory} command.
7868 The search path is used to find both program source files and @value{GDBN}
7869 script files (read using the @samp{-command} option and @samp{source} command).
7871 In addition to the source path, @value{GDBN} provides a set of commands
7872 that manage a list of source path substitution rules. A @dfn{substitution
7873 rule} specifies how to rewrite source directories stored in the program's
7874 debug information in case the sources were moved to a different
7875 directory between compilation and debugging. A rule is made of
7876 two strings, the first specifying what needs to be rewritten in
7877 the path, and the second specifying how it should be rewritten.
7878 In @ref{set substitute-path}, we name these two parts @var{from} and
7879 @var{to} respectively. @value{GDBN} does a simple string replacement
7880 of @var{from} with @var{to} at the start of the directory part of the
7881 source file name, and uses that result instead of the original file
7882 name to look up the sources.
7884 Using the previous example, suppose the @file{foo-1.0} tree has been
7885 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
7886 @value{GDBN} to replace @file{/usr/src} in all source path names with
7887 @file{/mnt/cross}. The first lookup will then be
7888 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
7889 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
7890 substitution rule, use the @code{set substitute-path} command
7891 (@pxref{set substitute-path}).
7893 To avoid unexpected substitution results, a rule is applied only if the
7894 @var{from} part of the directory name ends at a directory separator.
7895 For instance, a rule substituting @file{/usr/source} into
7896 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
7897 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
7898 is applied only at the beginning of the directory name, this rule will
7899 not be applied to @file{/root/usr/source/baz.c} either.
7901 In many cases, you can achieve the same result using the @code{directory}
7902 command. However, @code{set substitute-path} can be more efficient in
7903 the case where the sources are organized in a complex tree with multiple
7904 subdirectories. With the @code{directory} command, you need to add each
7905 subdirectory of your project. If you moved the entire tree while
7906 preserving its internal organization, then @code{set substitute-path}
7907 allows you to direct the debugger to all the sources with one single
7910 @code{set substitute-path} is also more than just a shortcut command.
7911 The source path is only used if the file at the original location no
7912 longer exists. On the other hand, @code{set substitute-path} modifies
7913 the debugger behavior to look at the rewritten location instead. So, if
7914 for any reason a source file that is not relevant to your executable is
7915 located at the original location, a substitution rule is the only
7916 method available to point @value{GDBN} at the new location.
7918 @cindex @samp{--with-relocated-sources}
7919 @cindex default source path substitution
7920 You can configure a default source path substitution rule by
7921 configuring @value{GDBN} with the
7922 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
7923 should be the name of a directory under @value{GDBN}'s configured
7924 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
7925 directory names in debug information under @var{dir} will be adjusted
7926 automatically if the installed @value{GDBN} is moved to a new
7927 location. This is useful if @value{GDBN}, libraries or executables
7928 with debug information and corresponding source code are being moved
7932 @item directory @var{dirname} @dots{}
7933 @item dir @var{dirname} @dots{}
7934 Add directory @var{dirname} to the front of the source path. Several
7935 directory names may be given to this command, separated by @samp{:}
7936 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
7937 part of absolute file names) or
7938 whitespace. You may specify a directory that is already in the source
7939 path; this moves it forward, so @value{GDBN} searches it sooner.
7943 @vindex $cdir@r{, convenience variable}
7944 @vindex $cwd@r{, convenience variable}
7945 @cindex compilation directory
7946 @cindex current directory
7947 @cindex working directory
7948 @cindex directory, current
7949 @cindex directory, compilation
7950 You can use the string @samp{$cdir} to refer to the compilation
7951 directory (if one is recorded), and @samp{$cwd} to refer to the current
7952 working directory. @samp{$cwd} is not the same as @samp{.}---the former
7953 tracks the current working directory as it changes during your @value{GDBN}
7954 session, while the latter is immediately expanded to the current
7955 directory at the time you add an entry to the source path.
7958 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
7960 @c RET-repeat for @code{directory} is explicitly disabled, but since
7961 @c repeating it would be a no-op we do not say that. (thanks to RMS)
7963 @item set directories @var{path-list}
7964 @kindex set directories
7965 Set the source path to @var{path-list}.
7966 @samp{$cdir:$cwd} are added if missing.
7968 @item show directories
7969 @kindex show directories
7970 Print the source path: show which directories it contains.
7972 @anchor{set substitute-path}
7973 @item set substitute-path @var{from} @var{to}
7974 @kindex set substitute-path
7975 Define a source path substitution rule, and add it at the end of the
7976 current list of existing substitution rules. If a rule with the same
7977 @var{from} was already defined, then the old rule is also deleted.
7979 For example, if the file @file{/foo/bar/baz.c} was moved to
7980 @file{/mnt/cross/baz.c}, then the command
7983 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
7987 will tell @value{GDBN} to replace @samp{/usr/src} with
7988 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
7989 @file{baz.c} even though it was moved.
7991 In the case when more than one substitution rule have been defined,
7992 the rules are evaluated one by one in the order where they have been
7993 defined. The first one matching, if any, is selected to perform
7996 For instance, if we had entered the following commands:
7999 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
8000 (@value{GDBP}) set substitute-path /usr/src /mnt/src
8004 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
8005 @file{/mnt/include/defs.h} by using the first rule. However, it would
8006 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
8007 @file{/mnt/src/lib/foo.c}.
8010 @item unset substitute-path [path]
8011 @kindex unset substitute-path
8012 If a path is specified, search the current list of substitution rules
8013 for a rule that would rewrite that path. Delete that rule if found.
8014 A warning is emitted by the debugger if no rule could be found.
8016 If no path is specified, then all substitution rules are deleted.
8018 @item show substitute-path [path]
8019 @kindex show substitute-path
8020 If a path is specified, then print the source path substitution rule
8021 which would rewrite that path, if any.
8023 If no path is specified, then print all existing source path substitution
8028 If your source path is cluttered with directories that are no longer of
8029 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
8030 versions of source. You can correct the situation as follows:
8034 Use @code{directory} with no argument to reset the source path to its default value.
8037 Use @code{directory} with suitable arguments to reinstall the
8038 directories you want in the source path. You can add all the
8039 directories in one command.
8043 @section Source and Machine Code
8044 @cindex source line and its code address
8046 You can use the command @code{info line} to map source lines to program
8047 addresses (and vice versa), and the command @code{disassemble} to display
8048 a range of addresses as machine instructions. You can use the command
8049 @code{set disassemble-next-line} to set whether to disassemble next
8050 source line when execution stops. When run under @sc{gnu} Emacs
8051 mode, the @code{info line} command causes the arrow to point to the
8052 line specified. Also, @code{info line} prints addresses in symbolic form as
8057 @item info line @var{location}
8058 Print the starting and ending addresses of the compiled code for
8059 source line @var{location}. You can specify source lines in any of
8060 the ways documented in @ref{Specify Location}.
8063 For example, we can use @code{info line} to discover the location of
8064 the object code for the first line of function
8065 @code{m4_changequote}:
8067 @c FIXME: I think this example should also show the addresses in
8068 @c symbolic form, as they usually would be displayed.
8070 (@value{GDBP}) info line m4_changequote
8071 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
8075 @cindex code address and its source line
8076 We can also inquire (using @code{*@var{addr}} as the form for
8077 @var{location}) what source line covers a particular address:
8079 (@value{GDBP}) info line *0x63ff
8080 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
8083 @cindex @code{$_} and @code{info line}
8084 @cindex @code{x} command, default address
8085 @kindex x@r{(examine), and} info line
8086 After @code{info line}, the default address for the @code{x} command
8087 is changed to the starting address of the line, so that @samp{x/i} is
8088 sufficient to begin examining the machine code (@pxref{Memory,
8089 ,Examining Memory}). Also, this address is saved as the value of the
8090 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
8095 @cindex assembly instructions
8096 @cindex instructions, assembly
8097 @cindex machine instructions
8098 @cindex listing machine instructions
8100 @itemx disassemble /m
8101 @itemx disassemble /s
8102 @itemx disassemble /r
8103 This specialized command dumps a range of memory as machine
8104 instructions. It can also print mixed source+disassembly by specifying
8105 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
8106 as well as in symbolic form by specifying the @code{/r} modifier.
8107 The default memory range is the function surrounding the
8108 program counter of the selected frame. A single argument to this
8109 command is a program counter value; @value{GDBN} dumps the function
8110 surrounding this value. When two arguments are given, they should
8111 be separated by a comma, possibly surrounded by whitespace. The
8112 arguments specify a range of addresses to dump, in one of two forms:
8115 @item @var{start},@var{end}
8116 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
8117 @item @var{start},+@var{length}
8118 the addresses from @var{start} (inclusive) to
8119 @code{@var{start}+@var{length}} (exclusive).
8123 When 2 arguments are specified, the name of the function is also
8124 printed (since there could be several functions in the given range).
8126 The argument(s) can be any expression yielding a numeric value, such as
8127 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
8129 If the range of memory being disassembled contains current program counter,
8130 the instruction at that location is shown with a @code{=>} marker.
8133 The following example shows the disassembly of a range of addresses of
8134 HP PA-RISC 2.0 code:
8137 (@value{GDBP}) disas 0x32c4, 0x32e4
8138 Dump of assembler code from 0x32c4 to 0x32e4:
8139 0x32c4 <main+204>: addil 0,dp
8140 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
8141 0x32cc <main+212>: ldil 0x3000,r31
8142 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
8143 0x32d4 <main+220>: ldo 0(r31),rp
8144 0x32d8 <main+224>: addil -0x800,dp
8145 0x32dc <main+228>: ldo 0x588(r1),r26
8146 0x32e0 <main+232>: ldil 0x3000,r31
8147 End of assembler dump.
8150 Here is an example showing mixed source+assembly for Intel x86
8151 with @code{/m} or @code{/s}, when the program is stopped just after
8152 function prologue in a non-optimized function with no inline code.
8155 (@value{GDBP}) disas /m main
8156 Dump of assembler code for function main:
8158 0x08048330 <+0>: push %ebp
8159 0x08048331 <+1>: mov %esp,%ebp
8160 0x08048333 <+3>: sub $0x8,%esp
8161 0x08048336 <+6>: and $0xfffffff0,%esp
8162 0x08048339 <+9>: sub $0x10,%esp
8164 6 printf ("Hello.\n");
8165 => 0x0804833c <+12>: movl $0x8048440,(%esp)
8166 0x08048343 <+19>: call 0x8048284 <puts@@plt>
8170 0x08048348 <+24>: mov $0x0,%eax
8171 0x0804834d <+29>: leave
8172 0x0804834e <+30>: ret
8174 End of assembler dump.
8177 The @code{/m} option is deprecated as its output is not useful when
8178 there is either inlined code or re-ordered code.
8179 The @code{/s} option is the preferred choice.
8180 Here is an example for AMD x86-64 showing the difference between
8181 @code{/m} output and @code{/s} output.
8182 This example has one inline function defined in a header file,
8183 and the code is compiled with @samp{-O2} optimization.
8184 Note how the @code{/m} output is missing the disassembly of
8185 several instructions that are present in the @code{/s} output.
8215 (@value{GDBP}) disas /m main
8216 Dump of assembler code for function main:
8220 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8221 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8225 0x000000000040041d <+29>: xor %eax,%eax
8226 0x000000000040041f <+31>: retq
8227 0x0000000000400420 <+32>: add %eax,%eax
8228 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8230 End of assembler dump.
8231 (@value{GDBP}) disas /s main
8232 Dump of assembler code for function main:
8236 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8240 0x0000000000400406 <+6>: test %eax,%eax
8241 0x0000000000400408 <+8>: js 0x400420 <main+32>
8246 0x000000000040040a <+10>: lea 0xa(%rax),%edx
8247 0x000000000040040d <+13>: test %eax,%eax
8248 0x000000000040040f <+15>: mov $0x1,%eax
8249 0x0000000000400414 <+20>: cmovne %edx,%eax
8253 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8257 0x000000000040041d <+29>: xor %eax,%eax
8258 0x000000000040041f <+31>: retq
8262 0x0000000000400420 <+32>: add %eax,%eax
8263 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8264 End of assembler dump.
8267 Here is another example showing raw instructions in hex for AMD x86-64,
8270 (gdb) disas /r 0x400281,+10
8271 Dump of assembler code from 0x400281 to 0x40028b:
8272 0x0000000000400281: 38 36 cmp %dh,(%rsi)
8273 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
8274 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
8275 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
8276 End of assembler dump.
8279 Addresses cannot be specified as a location (@pxref{Specify Location}).
8280 So, for example, if you want to disassemble function @code{bar}
8281 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
8282 and not @samp{disassemble foo.c:bar}.
8284 Some architectures have more than one commonly-used set of instruction
8285 mnemonics or other syntax.
8287 For programs that were dynamically linked and use shared libraries,
8288 instructions that call functions or branch to locations in the shared
8289 libraries might show a seemingly bogus location---it's actually a
8290 location of the relocation table. On some architectures, @value{GDBN}
8291 might be able to resolve these to actual function names.
8294 @kindex set disassembly-flavor
8295 @cindex Intel disassembly flavor
8296 @cindex AT&T disassembly flavor
8297 @item set disassembly-flavor @var{instruction-set}
8298 Select the instruction set to use when disassembling the
8299 program via the @code{disassemble} or @code{x/i} commands.
8301 Currently this command is only defined for the Intel x86 family. You
8302 can set @var{instruction-set} to either @code{intel} or @code{att}.
8303 The default is @code{att}, the AT&T flavor used by default by Unix
8304 assemblers for x86-based targets.
8306 @kindex show disassembly-flavor
8307 @item show disassembly-flavor
8308 Show the current setting of the disassembly flavor.
8312 @kindex set disassemble-next-line
8313 @kindex show disassemble-next-line
8314 @item set disassemble-next-line
8315 @itemx show disassemble-next-line
8316 Control whether or not @value{GDBN} will disassemble the next source
8317 line or instruction when execution stops. If ON, @value{GDBN} will
8318 display disassembly of the next source line when execution of the
8319 program being debugged stops. This is @emph{in addition} to
8320 displaying the source line itself, which @value{GDBN} always does if
8321 possible. If the next source line cannot be displayed for some reason
8322 (e.g., if @value{GDBN} cannot find the source file, or there's no line
8323 info in the debug info), @value{GDBN} will display disassembly of the
8324 next @emph{instruction} instead of showing the next source line. If
8325 AUTO, @value{GDBN} will display disassembly of next instruction only
8326 if the source line cannot be displayed. This setting causes
8327 @value{GDBN} to display some feedback when you step through a function
8328 with no line info or whose source file is unavailable. The default is
8329 OFF, which means never display the disassembly of the next line or
8335 @chapter Examining Data
8337 @cindex printing data
8338 @cindex examining data
8341 The usual way to examine data in your program is with the @code{print}
8342 command (abbreviated @code{p}), or its synonym @code{inspect}. It
8343 evaluates and prints the value of an expression of the language your
8344 program is written in (@pxref{Languages, ,Using @value{GDBN} with
8345 Different Languages}). It may also print the expression using a
8346 Python-based pretty-printer (@pxref{Pretty Printing}).
8349 @item print @var{expr}
8350 @itemx print /@var{f} @var{expr}
8351 @var{expr} is an expression (in the source language). By default the
8352 value of @var{expr} is printed in a format appropriate to its data type;
8353 you can choose a different format by specifying @samp{/@var{f}}, where
8354 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
8358 @itemx print /@var{f}
8359 @cindex reprint the last value
8360 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
8361 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
8362 conveniently inspect the same value in an alternative format.
8365 A more low-level way of examining data is with the @code{x} command.
8366 It examines data in memory at a specified address and prints it in a
8367 specified format. @xref{Memory, ,Examining Memory}.
8369 If you are interested in information about types, or about how the
8370 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
8371 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
8374 @cindex exploring hierarchical data structures
8376 Another way of examining values of expressions and type information is
8377 through the Python extension command @code{explore} (available only if
8378 the @value{GDBN} build is configured with @code{--with-python}). It
8379 offers an interactive way to start at the highest level (or, the most
8380 abstract level) of the data type of an expression (or, the data type
8381 itself) and explore all the way down to leaf scalar values/fields
8382 embedded in the higher level data types.
8385 @item explore @var{arg}
8386 @var{arg} is either an expression (in the source language), or a type
8387 visible in the current context of the program being debugged.
8390 The working of the @code{explore} command can be illustrated with an
8391 example. If a data type @code{struct ComplexStruct} is defined in your
8401 struct ComplexStruct
8403 struct SimpleStruct *ss_p;
8409 followed by variable declarations as
8412 struct SimpleStruct ss = @{ 10, 1.11 @};
8413 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
8417 then, the value of the variable @code{cs} can be explored using the
8418 @code{explore} command as follows.
8422 The value of `cs' is a struct/class of type `struct ComplexStruct' with
8423 the following fields:
8425 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
8426 arr = <Enter 1 to explore this field of type `int [10]'>
8428 Enter the field number of choice:
8432 Since the fields of @code{cs} are not scalar values, you are being
8433 prompted to chose the field you want to explore. Let's say you choose
8434 the field @code{ss_p} by entering @code{0}. Then, since this field is a
8435 pointer, you will be asked if it is pointing to a single value. From
8436 the declaration of @code{cs} above, it is indeed pointing to a single
8437 value, hence you enter @code{y}. If you enter @code{n}, then you will
8438 be asked if it were pointing to an array of values, in which case this
8439 field will be explored as if it were an array.
8442 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
8443 Continue exploring it as a pointer to a single value [y/n]: y
8444 The value of `*(cs.ss_p)' is a struct/class of type `struct
8445 SimpleStruct' with the following fields:
8447 i = 10 .. (Value of type `int')
8448 d = 1.1100000000000001 .. (Value of type `double')
8450 Press enter to return to parent value:
8454 If the field @code{arr} of @code{cs} was chosen for exploration by
8455 entering @code{1} earlier, then since it is as array, you will be
8456 prompted to enter the index of the element in the array that you want
8460 `cs.arr' is an array of `int'.
8461 Enter the index of the element you want to explore in `cs.arr': 5
8463 `(cs.arr)[5]' is a scalar value of type `int'.
8467 Press enter to return to parent value:
8470 In general, at any stage of exploration, you can go deeper towards the
8471 leaf values by responding to the prompts appropriately, or hit the
8472 return key to return to the enclosing data structure (the @i{higher}
8473 level data structure).
8475 Similar to exploring values, you can use the @code{explore} command to
8476 explore types. Instead of specifying a value (which is typically a
8477 variable name or an expression valid in the current context of the
8478 program being debugged), you specify a type name. If you consider the
8479 same example as above, your can explore the type
8480 @code{struct ComplexStruct} by passing the argument
8481 @code{struct ComplexStruct} to the @code{explore} command.
8484 (gdb) explore struct ComplexStruct
8488 By responding to the prompts appropriately in the subsequent interactive
8489 session, you can explore the type @code{struct ComplexStruct} in a
8490 manner similar to how the value @code{cs} was explored in the above
8493 The @code{explore} command also has two sub-commands,
8494 @code{explore value} and @code{explore type}. The former sub-command is
8495 a way to explicitly specify that value exploration of the argument is
8496 being invoked, while the latter is a way to explicitly specify that type
8497 exploration of the argument is being invoked.
8500 @item explore value @var{expr}
8501 @cindex explore value
8502 This sub-command of @code{explore} explores the value of the
8503 expression @var{expr} (if @var{expr} is an expression valid in the
8504 current context of the program being debugged). The behavior of this
8505 command is identical to that of the behavior of the @code{explore}
8506 command being passed the argument @var{expr}.
8508 @item explore type @var{arg}
8509 @cindex explore type
8510 This sub-command of @code{explore} explores the type of @var{arg} (if
8511 @var{arg} is a type visible in the current context of program being
8512 debugged), or the type of the value/expression @var{arg} (if @var{arg}
8513 is an expression valid in the current context of the program being
8514 debugged). If @var{arg} is a type, then the behavior of this command is
8515 identical to that of the @code{explore} command being passed the
8516 argument @var{arg}. If @var{arg} is an expression, then the behavior of
8517 this command will be identical to that of the @code{explore} command
8518 being passed the type of @var{arg} as the argument.
8522 * Expressions:: Expressions
8523 * Ambiguous Expressions:: Ambiguous Expressions
8524 * Variables:: Program variables
8525 * Arrays:: Artificial arrays
8526 * Output Formats:: Output formats
8527 * Memory:: Examining memory
8528 * Auto Display:: Automatic display
8529 * Print Settings:: Print settings
8530 * Pretty Printing:: Python pretty printing
8531 * Value History:: Value history
8532 * Convenience Vars:: Convenience variables
8533 * Convenience Funs:: Convenience functions
8534 * Registers:: Registers
8535 * Floating Point Hardware:: Floating point hardware
8536 * Vector Unit:: Vector Unit
8537 * OS Information:: Auxiliary data provided by operating system
8538 * Memory Region Attributes:: Memory region attributes
8539 * Dump/Restore Files:: Copy between memory and a file
8540 * Core File Generation:: Cause a program dump its core
8541 * Character Sets:: Debugging programs that use a different
8542 character set than GDB does
8543 * Caching Target Data:: Data caching for targets
8544 * Searching Memory:: Searching memory for a sequence of bytes
8548 @section Expressions
8551 @code{print} and many other @value{GDBN} commands accept an expression and
8552 compute its value. Any kind of constant, variable or operator defined
8553 by the programming language you are using is valid in an expression in
8554 @value{GDBN}. This includes conditional expressions, function calls,
8555 casts, and string constants. It also includes preprocessor macros, if
8556 you compiled your program to include this information; see
8559 @cindex arrays in expressions
8560 @value{GDBN} supports array constants in expressions input by
8561 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
8562 you can use the command @code{print @{1, 2, 3@}} to create an array
8563 of three integers. If you pass an array to a function or assign it
8564 to a program variable, @value{GDBN} copies the array to memory that
8565 is @code{malloc}ed in the target program.
8567 Because C is so widespread, most of the expressions shown in examples in
8568 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
8569 Languages}, for information on how to use expressions in other
8572 In this section, we discuss operators that you can use in @value{GDBN}
8573 expressions regardless of your programming language.
8575 @cindex casts, in expressions
8576 Casts are supported in all languages, not just in C, because it is so
8577 useful to cast a number into a pointer in order to examine a structure
8578 at that address in memory.
8579 @c FIXME: casts supported---Mod2 true?
8581 @value{GDBN} supports these operators, in addition to those common
8582 to programming languages:
8586 @samp{@@} is a binary operator for treating parts of memory as arrays.
8587 @xref{Arrays, ,Artificial Arrays}, for more information.
8590 @samp{::} allows you to specify a variable in terms of the file or
8591 function where it is defined. @xref{Variables, ,Program Variables}.
8593 @cindex @{@var{type}@}
8594 @cindex type casting memory
8595 @cindex memory, viewing as typed object
8596 @cindex casts, to view memory
8597 @item @{@var{type}@} @var{addr}
8598 Refers to an object of type @var{type} stored at address @var{addr} in
8599 memory. The address @var{addr} may be any expression whose value is
8600 an integer or pointer (but parentheses are required around binary
8601 operators, just as in a cast). This construct is allowed regardless
8602 of what kind of data is normally supposed to reside at @var{addr}.
8605 @node Ambiguous Expressions
8606 @section Ambiguous Expressions
8607 @cindex ambiguous expressions
8609 Expressions can sometimes contain some ambiguous elements. For instance,
8610 some programming languages (notably Ada, C@t{++} and Objective-C) permit
8611 a single function name to be defined several times, for application in
8612 different contexts. This is called @dfn{overloading}. Another example
8613 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
8614 templates and is typically instantiated several times, resulting in
8615 the same function name being defined in different contexts.
8617 In some cases and depending on the language, it is possible to adjust
8618 the expression to remove the ambiguity. For instance in C@t{++}, you
8619 can specify the signature of the function you want to break on, as in
8620 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
8621 qualified name of your function often makes the expression unambiguous
8624 When an ambiguity that needs to be resolved is detected, the debugger
8625 has the capability to display a menu of numbered choices for each
8626 possibility, and then waits for the selection with the prompt @samp{>}.
8627 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
8628 aborts the current command. If the command in which the expression was
8629 used allows more than one choice to be selected, the next option in the
8630 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
8633 For example, the following session excerpt shows an attempt to set a
8634 breakpoint at the overloaded symbol @code{String::after}.
8635 We choose three particular definitions of that function name:
8637 @c FIXME! This is likely to change to show arg type lists, at least
8640 (@value{GDBP}) b String::after
8643 [2] file:String.cc; line number:867
8644 [3] file:String.cc; line number:860
8645 [4] file:String.cc; line number:875
8646 [5] file:String.cc; line number:853
8647 [6] file:String.cc; line number:846
8648 [7] file:String.cc; line number:735
8650 Breakpoint 1 at 0xb26c: file String.cc, line 867.
8651 Breakpoint 2 at 0xb344: file String.cc, line 875.
8652 Breakpoint 3 at 0xafcc: file String.cc, line 846.
8653 Multiple breakpoints were set.
8654 Use the "delete" command to delete unwanted
8661 @kindex set multiple-symbols
8662 @item set multiple-symbols @var{mode}
8663 @cindex multiple-symbols menu
8665 This option allows you to adjust the debugger behavior when an expression
8668 By default, @var{mode} is set to @code{all}. If the command with which
8669 the expression is used allows more than one choice, then @value{GDBN}
8670 automatically selects all possible choices. For instance, inserting
8671 a breakpoint on a function using an ambiguous name results in a breakpoint
8672 inserted on each possible match. However, if a unique choice must be made,
8673 then @value{GDBN} uses the menu to help you disambiguate the expression.
8674 For instance, printing the address of an overloaded function will result
8675 in the use of the menu.
8677 When @var{mode} is set to @code{ask}, the debugger always uses the menu
8678 when an ambiguity is detected.
8680 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
8681 an error due to the ambiguity and the command is aborted.
8683 @kindex show multiple-symbols
8684 @item show multiple-symbols
8685 Show the current value of the @code{multiple-symbols} setting.
8689 @section Program Variables
8691 The most common kind of expression to use is the name of a variable
8694 Variables in expressions are understood in the selected stack frame
8695 (@pxref{Selection, ,Selecting a Frame}); they must be either:
8699 global (or file-static)
8706 visible according to the scope rules of the
8707 programming language from the point of execution in that frame
8710 @noindent This means that in the function
8725 you can examine and use the variable @code{a} whenever your program is
8726 executing within the function @code{foo}, but you can only use or
8727 examine the variable @code{b} while your program is executing inside
8728 the block where @code{b} is declared.
8730 @cindex variable name conflict
8731 There is an exception: you can refer to a variable or function whose
8732 scope is a single source file even if the current execution point is not
8733 in this file. But it is possible to have more than one such variable or
8734 function with the same name (in different source files). If that
8735 happens, referring to that name has unpredictable effects. If you wish,
8736 you can specify a static variable in a particular function or file by
8737 using the colon-colon (@code{::}) notation:
8739 @cindex colon-colon, context for variables/functions
8741 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
8742 @cindex @code{::}, context for variables/functions
8745 @var{file}::@var{variable}
8746 @var{function}::@var{variable}
8750 Here @var{file} or @var{function} is the name of the context for the
8751 static @var{variable}. In the case of file names, you can use quotes to
8752 make sure @value{GDBN} parses the file name as a single word---for example,
8753 to print a global value of @code{x} defined in @file{f2.c}:
8756 (@value{GDBP}) p 'f2.c'::x
8759 The @code{::} notation is normally used for referring to
8760 static variables, since you typically disambiguate uses of local variables
8761 in functions by selecting the appropriate frame and using the
8762 simple name of the variable. However, you may also use this notation
8763 to refer to local variables in frames enclosing the selected frame:
8772 process (a); /* Stop here */
8783 For example, if there is a breakpoint at the commented line,
8784 here is what you might see
8785 when the program stops after executing the call @code{bar(0)}:
8790 (@value{GDBP}) p bar::a
8793 #2 0x080483d0 in foo (a=5) at foobar.c:12
8796 (@value{GDBP}) p bar::a
8800 @cindex C@t{++} scope resolution
8801 These uses of @samp{::} are very rarely in conflict with the very
8802 similar use of the same notation in C@t{++}. When they are in
8803 conflict, the C@t{++} meaning takes precedence; however, this can be
8804 overridden by quoting the file or function name with single quotes.
8806 For example, suppose the program is stopped in a method of a class
8807 that has a field named @code{includefile}, and there is also an
8808 include file named @file{includefile} that defines a variable,
8812 (@value{GDBP}) p includefile
8814 (@value{GDBP}) p includefile::some_global
8815 A syntax error in expression, near `'.
8816 (@value{GDBP}) p 'includefile'::some_global
8820 @cindex wrong values
8821 @cindex variable values, wrong
8822 @cindex function entry/exit, wrong values of variables
8823 @cindex optimized code, wrong values of variables
8825 @emph{Warning:} Occasionally, a local variable may appear to have the
8826 wrong value at certain points in a function---just after entry to a new
8827 scope, and just before exit.
8829 You may see this problem when you are stepping by machine instructions.
8830 This is because, on most machines, it takes more than one instruction to
8831 set up a stack frame (including local variable definitions); if you are
8832 stepping by machine instructions, variables may appear to have the wrong
8833 values until the stack frame is completely built. On exit, it usually
8834 also takes more than one machine instruction to destroy a stack frame;
8835 after you begin stepping through that group of instructions, local
8836 variable definitions may be gone.
8838 This may also happen when the compiler does significant optimizations.
8839 To be sure of always seeing accurate values, turn off all optimization
8842 @cindex ``No symbol "foo" in current context''
8843 Another possible effect of compiler optimizations is to optimize
8844 unused variables out of existence, or assign variables to registers (as
8845 opposed to memory addresses). Depending on the support for such cases
8846 offered by the debug info format used by the compiler, @value{GDBN}
8847 might not be able to display values for such local variables. If that
8848 happens, @value{GDBN} will print a message like this:
8851 No symbol "foo" in current context.
8854 To solve such problems, either recompile without optimizations, or use a
8855 different debug info format, if the compiler supports several such
8856 formats. @xref{Compilation}, for more information on choosing compiler
8857 options. @xref{C, ,C and C@t{++}}, for more information about debug
8858 info formats that are best suited to C@t{++} programs.
8860 If you ask to print an object whose contents are unknown to
8861 @value{GDBN}, e.g., because its data type is not completely specified
8862 by the debug information, @value{GDBN} will say @samp{<incomplete
8863 type>}. @xref{Symbols, incomplete type}, for more about this.
8865 If you append @kbd{@@entry} string to a function parameter name you get its
8866 value at the time the function got called. If the value is not available an
8867 error message is printed. Entry values are available only with some compilers.
8868 Entry values are normally also printed at the function parameter list according
8869 to @ref{set print entry-values}.
8872 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
8878 (gdb) print i@@entry
8882 Strings are identified as arrays of @code{char} values without specified
8883 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
8884 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
8885 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
8886 defines literal string type @code{"char"} as @code{char} without a sign.
8891 signed char var1[] = "A";
8894 You get during debugging
8899 $2 = @{65 'A', 0 '\0'@}
8903 @section Artificial Arrays
8905 @cindex artificial array
8907 @kindex @@@r{, referencing memory as an array}
8908 It is often useful to print out several successive objects of the
8909 same type in memory; a section of an array, or an array of
8910 dynamically determined size for which only a pointer exists in the
8913 You can do this by referring to a contiguous span of memory as an
8914 @dfn{artificial array}, using the binary operator @samp{@@}. The left
8915 operand of @samp{@@} should be the first element of the desired array
8916 and be an individual object. The right operand should be the desired length
8917 of the array. The result is an array value whose elements are all of
8918 the type of the left argument. The first element is actually the left
8919 argument; the second element comes from bytes of memory immediately
8920 following those that hold the first element, and so on. Here is an
8921 example. If a program says
8924 int *array = (int *) malloc (len * sizeof (int));
8928 you can print the contents of @code{array} with
8934 The left operand of @samp{@@} must reside in memory. Array values made
8935 with @samp{@@} in this way behave just like other arrays in terms of
8936 subscripting, and are coerced to pointers when used in expressions.
8937 Artificial arrays most often appear in expressions via the value history
8938 (@pxref{Value History, ,Value History}), after printing one out.
8940 Another way to create an artificial array is to use a cast.
8941 This re-interprets a value as if it were an array.
8942 The value need not be in memory:
8944 (@value{GDBP}) p/x (short[2])0x12345678
8945 $1 = @{0x1234, 0x5678@}
8948 As a convenience, if you leave the array length out (as in
8949 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
8950 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
8952 (@value{GDBP}) p/x (short[])0x12345678
8953 $2 = @{0x1234, 0x5678@}
8956 Sometimes the artificial array mechanism is not quite enough; in
8957 moderately complex data structures, the elements of interest may not
8958 actually be adjacent---for example, if you are interested in the values
8959 of pointers in an array. One useful work-around in this situation is
8960 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
8961 Variables}) as a counter in an expression that prints the first
8962 interesting value, and then repeat that expression via @key{RET}. For
8963 instance, suppose you have an array @code{dtab} of pointers to
8964 structures, and you are interested in the values of a field @code{fv}
8965 in each structure. Here is an example of what you might type:
8975 @node Output Formats
8976 @section Output Formats
8978 @cindex formatted output
8979 @cindex output formats
8980 By default, @value{GDBN} prints a value according to its data type. Sometimes
8981 this is not what you want. For example, you might want to print a number
8982 in hex, or a pointer in decimal. Or you might want to view data in memory
8983 at a certain address as a character string or as an instruction. To do
8984 these things, specify an @dfn{output format} when you print a value.
8986 The simplest use of output formats is to say how to print a value
8987 already computed. This is done by starting the arguments of the
8988 @code{print} command with a slash and a format letter. The format
8989 letters supported are:
8993 Regard the bits of the value as an integer, and print the integer in
8997 Print as integer in signed decimal.
9000 Print as integer in unsigned decimal.
9003 Print as integer in octal.
9006 Print as integer in binary. The letter @samp{t} stands for ``two''.
9007 @footnote{@samp{b} cannot be used because these format letters are also
9008 used with the @code{x} command, where @samp{b} stands for ``byte'';
9009 see @ref{Memory,,Examining Memory}.}
9012 @cindex unknown address, locating
9013 @cindex locate address
9014 Print as an address, both absolute in hexadecimal and as an offset from
9015 the nearest preceding symbol. You can use this format used to discover
9016 where (in what function) an unknown address is located:
9019 (@value{GDBP}) p/a 0x54320
9020 $3 = 0x54320 <_initialize_vx+396>
9024 The command @code{info symbol 0x54320} yields similar results.
9025 @xref{Symbols, info symbol}.
9028 Regard as an integer and print it as a character constant. This
9029 prints both the numerical value and its character representation. The
9030 character representation is replaced with the octal escape @samp{\nnn}
9031 for characters outside the 7-bit @sc{ascii} range.
9033 Without this format, @value{GDBN} displays @code{char},
9034 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
9035 constants. Single-byte members of vectors are displayed as integer
9039 Regard the bits of the value as a floating point number and print
9040 using typical floating point syntax.
9043 @cindex printing strings
9044 @cindex printing byte arrays
9045 Regard as a string, if possible. With this format, pointers to single-byte
9046 data are displayed as null-terminated strings and arrays of single-byte data
9047 are displayed as fixed-length strings. Other values are displayed in their
9050 Without this format, @value{GDBN} displays pointers to and arrays of
9051 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
9052 strings. Single-byte members of a vector are displayed as an integer
9056 Like @samp{x} formatting, the value is treated as an integer and
9057 printed as hexadecimal, but leading zeros are printed to pad the value
9058 to the size of the integer type.
9061 @cindex raw printing
9062 Print using the @samp{raw} formatting. By default, @value{GDBN} will
9063 use a Python-based pretty-printer, if one is available (@pxref{Pretty
9064 Printing}). This typically results in a higher-level display of the
9065 value's contents. The @samp{r} format bypasses any Python
9066 pretty-printer which might exist.
9069 For example, to print the program counter in hex (@pxref{Registers}), type
9076 Note that no space is required before the slash; this is because command
9077 names in @value{GDBN} cannot contain a slash.
9079 To reprint the last value in the value history with a different format,
9080 you can use the @code{print} command with just a format and no
9081 expression. For example, @samp{p/x} reprints the last value in hex.
9084 @section Examining Memory
9086 You can use the command @code{x} (for ``examine'') to examine memory in
9087 any of several formats, independently of your program's data types.
9089 @cindex examining memory
9091 @kindex x @r{(examine memory)}
9092 @item x/@var{nfu} @var{addr}
9095 Use the @code{x} command to examine memory.
9098 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
9099 much memory to display and how to format it; @var{addr} is an
9100 expression giving the address where you want to start displaying memory.
9101 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
9102 Several commands set convenient defaults for @var{addr}.
9105 @item @var{n}, the repeat count
9106 The repeat count is a decimal integer; the default is 1. It specifies
9107 how much memory (counting by units @var{u}) to display.
9108 @c This really is **decimal**; unaffected by 'set radix' as of GDB
9111 @item @var{f}, the display format
9112 The display format is one of the formats used by @code{print}
9113 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
9114 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
9115 The default is @samp{x} (hexadecimal) initially. The default changes
9116 each time you use either @code{x} or @code{print}.
9118 @item @var{u}, the unit size
9119 The unit size is any of
9125 Halfwords (two bytes).
9127 Words (four bytes). This is the initial default.
9129 Giant words (eight bytes).
9132 Each time you specify a unit size with @code{x}, that size becomes the
9133 default unit the next time you use @code{x}. For the @samp{i} format,
9134 the unit size is ignored and is normally not written. For the @samp{s} format,
9135 the unit size defaults to @samp{b}, unless it is explicitly given.
9136 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
9137 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
9138 Note that the results depend on the programming language of the
9139 current compilation unit. If the language is C, the @samp{s}
9140 modifier will use the UTF-16 encoding while @samp{w} will use
9141 UTF-32. The encoding is set by the programming language and cannot
9144 @item @var{addr}, starting display address
9145 @var{addr} is the address where you want @value{GDBN} to begin displaying
9146 memory. The expression need not have a pointer value (though it may);
9147 it is always interpreted as an integer address of a byte of memory.
9148 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
9149 @var{addr} is usually just after the last address examined---but several
9150 other commands also set the default address: @code{info breakpoints} (to
9151 the address of the last breakpoint listed), @code{info line} (to the
9152 starting address of a line), and @code{print} (if you use it to display
9153 a value from memory).
9156 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
9157 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
9158 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
9159 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
9160 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
9162 Since the letters indicating unit sizes are all distinct from the
9163 letters specifying output formats, you do not have to remember whether
9164 unit size or format comes first; either order works. The output
9165 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
9166 (However, the count @var{n} must come first; @samp{wx4} does not work.)
9168 Even though the unit size @var{u} is ignored for the formats @samp{s}
9169 and @samp{i}, you might still want to use a count @var{n}; for example,
9170 @samp{3i} specifies that you want to see three machine instructions,
9171 including any operands. For convenience, especially when used with
9172 the @code{display} command, the @samp{i} format also prints branch delay
9173 slot instructions, if any, beyond the count specified, which immediately
9174 follow the last instruction that is within the count. The command
9175 @code{disassemble} gives an alternative way of inspecting machine
9176 instructions; see @ref{Machine Code,,Source and Machine Code}.
9178 All the defaults for the arguments to @code{x} are designed to make it
9179 easy to continue scanning memory with minimal specifications each time
9180 you use @code{x}. For example, after you have inspected three machine
9181 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
9182 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
9183 the repeat count @var{n} is used again; the other arguments default as
9184 for successive uses of @code{x}.
9186 When examining machine instructions, the instruction at current program
9187 counter is shown with a @code{=>} marker. For example:
9190 (@value{GDBP}) x/5i $pc-6
9191 0x804837f <main+11>: mov %esp,%ebp
9192 0x8048381 <main+13>: push %ecx
9193 0x8048382 <main+14>: sub $0x4,%esp
9194 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
9195 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
9198 @cindex @code{$_}, @code{$__}, and value history
9199 The addresses and contents printed by the @code{x} command are not saved
9200 in the value history because there is often too much of them and they
9201 would get in the way. Instead, @value{GDBN} makes these values available for
9202 subsequent use in expressions as values of the convenience variables
9203 @code{$_} and @code{$__}. After an @code{x} command, the last address
9204 examined is available for use in expressions in the convenience variable
9205 @code{$_}. The contents of that address, as examined, are available in
9206 the convenience variable @code{$__}.
9208 If the @code{x} command has a repeat count, the address and contents saved
9209 are from the last memory unit printed; this is not the same as the last
9210 address printed if several units were printed on the last line of output.
9212 @anchor{addressable memory unit}
9213 @cindex addressable memory unit
9214 Most targets have an addressable memory unit size of 8 bits. This means
9215 that to each memory address are associated 8 bits of data. Some
9216 targets, however, have other addressable memory unit sizes.
9217 Within @value{GDBN} and this document, the term
9218 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
9219 when explicitly referring to a chunk of data of that size. The word
9220 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
9221 the addressable memory unit size of the target. For most systems,
9222 addressable memory unit is a synonym of byte.
9224 @cindex remote memory comparison
9225 @cindex target memory comparison
9226 @cindex verify remote memory image
9227 @cindex verify target memory image
9228 When you are debugging a program running on a remote target machine
9229 (@pxref{Remote Debugging}), you may wish to verify the program's image
9230 in the remote machine's memory against the executable file you
9231 downloaded to the target. Or, on any target, you may want to check
9232 whether the program has corrupted its own read-only sections. The
9233 @code{compare-sections} command is provided for such situations.
9236 @kindex compare-sections
9237 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
9238 Compare the data of a loadable section @var{section-name} in the
9239 executable file of the program being debugged with the same section in
9240 the target machine's memory, and report any mismatches. With no
9241 arguments, compares all loadable sections. With an argument of
9242 @code{-r}, compares all loadable read-only sections.
9244 Note: for remote targets, this command can be accelerated if the
9245 target supports computing the CRC checksum of a block of memory
9246 (@pxref{qCRC packet}).
9250 @section Automatic Display
9251 @cindex automatic display
9252 @cindex display of expressions
9254 If you find that you want to print the value of an expression frequently
9255 (to see how it changes), you might want to add it to the @dfn{automatic
9256 display list} so that @value{GDBN} prints its value each time your program stops.
9257 Each expression added to the list is given a number to identify it;
9258 to remove an expression from the list, you specify that number.
9259 The automatic display looks like this:
9263 3: bar[5] = (struct hack *) 0x3804
9267 This display shows item numbers, expressions and their current values. As with
9268 displays you request manually using @code{x} or @code{print}, you can
9269 specify the output format you prefer; in fact, @code{display} decides
9270 whether to use @code{print} or @code{x} depending your format
9271 specification---it uses @code{x} if you specify either the @samp{i}
9272 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
9276 @item display @var{expr}
9277 Add the expression @var{expr} to the list of expressions to display
9278 each time your program stops. @xref{Expressions, ,Expressions}.
9280 @code{display} does not repeat if you press @key{RET} again after using it.
9282 @item display/@var{fmt} @var{expr}
9283 For @var{fmt} specifying only a display format and not a size or
9284 count, add the expression @var{expr} to the auto-display list but
9285 arrange to display it each time in the specified format @var{fmt}.
9286 @xref{Output Formats,,Output Formats}.
9288 @item display/@var{fmt} @var{addr}
9289 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
9290 number of units, add the expression @var{addr} as a memory address to
9291 be examined each time your program stops. Examining means in effect
9292 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
9295 For example, @samp{display/i $pc} can be helpful, to see the machine
9296 instruction about to be executed each time execution stops (@samp{$pc}
9297 is a common name for the program counter; @pxref{Registers, ,Registers}).
9300 @kindex delete display
9302 @item undisplay @var{dnums}@dots{}
9303 @itemx delete display @var{dnums}@dots{}
9304 Remove items from the list of expressions to display. Specify the
9305 numbers of the displays that you want affected with the command
9306 argument @var{dnums}. It can be a single display number, one of the
9307 numbers shown in the first field of the @samp{info display} display;
9308 or it could be a range of display numbers, as in @code{2-4}.
9310 @code{undisplay} does not repeat if you press @key{RET} after using it.
9311 (Otherwise you would just get the error @samp{No display number @dots{}}.)
9313 @kindex disable display
9314 @item disable display @var{dnums}@dots{}
9315 Disable the display of item numbers @var{dnums}. A disabled display
9316 item is not printed automatically, but is not forgotten. It may be
9317 enabled again later. Specify the numbers of the displays that you
9318 want affected with the command argument @var{dnums}. It can be a
9319 single display number, one of the numbers shown in the first field of
9320 the @samp{info display} display; or it could be a range of display
9321 numbers, as in @code{2-4}.
9323 @kindex enable display
9324 @item enable display @var{dnums}@dots{}
9325 Enable display of item numbers @var{dnums}. It becomes effective once
9326 again in auto display of its expression, until you specify otherwise.
9327 Specify the numbers of the displays that you want affected with the
9328 command argument @var{dnums}. It can be a single display number, one
9329 of the numbers shown in the first field of the @samp{info display}
9330 display; or it could be a range of display numbers, as in @code{2-4}.
9333 Display the current values of the expressions on the list, just as is
9334 done when your program stops.
9336 @kindex info display
9338 Print the list of expressions previously set up to display
9339 automatically, each one with its item number, but without showing the
9340 values. This includes disabled expressions, which are marked as such.
9341 It also includes expressions which would not be displayed right now
9342 because they refer to automatic variables not currently available.
9345 @cindex display disabled out of scope
9346 If a display expression refers to local variables, then it does not make
9347 sense outside the lexical context for which it was set up. Such an
9348 expression is disabled when execution enters a context where one of its
9349 variables is not defined. For example, if you give the command
9350 @code{display last_char} while inside a function with an argument
9351 @code{last_char}, @value{GDBN} displays this argument while your program
9352 continues to stop inside that function. When it stops elsewhere---where
9353 there is no variable @code{last_char}---the display is disabled
9354 automatically. The next time your program stops where @code{last_char}
9355 is meaningful, you can enable the display expression once again.
9357 @node Print Settings
9358 @section Print Settings
9360 @cindex format options
9361 @cindex print settings
9362 @value{GDBN} provides the following ways to control how arrays, structures,
9363 and symbols are printed.
9366 These settings are useful for debugging programs in any language:
9370 @item set print address
9371 @itemx set print address on
9372 @cindex print/don't print memory addresses
9373 @value{GDBN} prints memory addresses showing the location of stack
9374 traces, structure values, pointer values, breakpoints, and so forth,
9375 even when it also displays the contents of those addresses. The default
9376 is @code{on}. For example, this is what a stack frame display looks like with
9377 @code{set print address on}:
9382 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
9384 530 if (lquote != def_lquote)
9388 @item set print address off
9389 Do not print addresses when displaying their contents. For example,
9390 this is the same stack frame displayed with @code{set print address off}:
9394 (@value{GDBP}) set print addr off
9396 #0 set_quotes (lq="<<", rq=">>") at input.c:530
9397 530 if (lquote != def_lquote)
9401 You can use @samp{set print address off} to eliminate all machine
9402 dependent displays from the @value{GDBN} interface. For example, with
9403 @code{print address off}, you should get the same text for backtraces on
9404 all machines---whether or not they involve pointer arguments.
9407 @item show print address
9408 Show whether or not addresses are to be printed.
9411 When @value{GDBN} prints a symbolic address, it normally prints the
9412 closest earlier symbol plus an offset. If that symbol does not uniquely
9413 identify the address (for example, it is a name whose scope is a single
9414 source file), you may need to clarify. One way to do this is with
9415 @code{info line}, for example @samp{info line *0x4537}. Alternately,
9416 you can set @value{GDBN} to print the source file and line number when
9417 it prints a symbolic address:
9420 @item set print symbol-filename on
9421 @cindex source file and line of a symbol
9422 @cindex symbol, source file and line
9423 Tell @value{GDBN} to print the source file name and line number of a
9424 symbol in the symbolic form of an address.
9426 @item set print symbol-filename off
9427 Do not print source file name and line number of a symbol. This is the
9430 @item show print symbol-filename
9431 Show whether or not @value{GDBN} will print the source file name and
9432 line number of a symbol in the symbolic form of an address.
9435 Another situation where it is helpful to show symbol filenames and line
9436 numbers is when disassembling code; @value{GDBN} shows you the line
9437 number and source file that corresponds to each instruction.
9439 Also, you may wish to see the symbolic form only if the address being
9440 printed is reasonably close to the closest earlier symbol:
9443 @item set print max-symbolic-offset @var{max-offset}
9444 @itemx set print max-symbolic-offset unlimited
9445 @cindex maximum value for offset of closest symbol
9446 Tell @value{GDBN} to only display the symbolic form of an address if the
9447 offset between the closest earlier symbol and the address is less than
9448 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
9449 to always print the symbolic form of an address if any symbol precedes
9450 it. Zero is equivalent to @code{unlimited}.
9452 @item show print max-symbolic-offset
9453 Ask how large the maximum offset is that @value{GDBN} prints in a
9457 @cindex wild pointer, interpreting
9458 @cindex pointer, finding referent
9459 If you have a pointer and you are not sure where it points, try
9460 @samp{set print symbol-filename on}. Then you can determine the name
9461 and source file location of the variable where it points, using
9462 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
9463 For example, here @value{GDBN} shows that a variable @code{ptt} points
9464 at another variable @code{t}, defined in @file{hi2.c}:
9467 (@value{GDBP}) set print symbol-filename on
9468 (@value{GDBP}) p/a ptt
9469 $4 = 0xe008 <t in hi2.c>
9473 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
9474 does not show the symbol name and filename of the referent, even with
9475 the appropriate @code{set print} options turned on.
9478 You can also enable @samp{/a}-like formatting all the time using
9479 @samp{set print symbol on}:
9482 @item set print symbol on
9483 Tell @value{GDBN} to print the symbol corresponding to an address, if
9486 @item set print symbol off
9487 Tell @value{GDBN} not to print the symbol corresponding to an
9488 address. In this mode, @value{GDBN} will still print the symbol
9489 corresponding to pointers to functions. This is the default.
9491 @item show print symbol
9492 Show whether @value{GDBN} will display the symbol corresponding to an
9496 Other settings control how different kinds of objects are printed:
9499 @item set print array
9500 @itemx set print array on
9501 @cindex pretty print arrays
9502 Pretty print arrays. This format is more convenient to read,
9503 but uses more space. The default is off.
9505 @item set print array off
9506 Return to compressed format for arrays.
9508 @item show print array
9509 Show whether compressed or pretty format is selected for displaying
9512 @cindex print array indexes
9513 @item set print array-indexes
9514 @itemx set print array-indexes on
9515 Print the index of each element when displaying arrays. May be more
9516 convenient to locate a given element in the array or quickly find the
9517 index of a given element in that printed array. The default is off.
9519 @item set print array-indexes off
9520 Stop printing element indexes when displaying arrays.
9522 @item show print array-indexes
9523 Show whether the index of each element is printed when displaying
9526 @item set print elements @var{number-of-elements}
9527 @itemx set print elements unlimited
9528 @cindex number of array elements to print
9529 @cindex limit on number of printed array elements
9530 Set a limit on how many elements of an array @value{GDBN} will print.
9531 If @value{GDBN} is printing a large array, it stops printing after it has
9532 printed the number of elements set by the @code{set print elements} command.
9533 This limit also applies to the display of strings.
9534 When @value{GDBN} starts, this limit is set to 200.
9535 Setting @var{number-of-elements} to @code{unlimited} or zero means
9536 that the number of elements to print is unlimited.
9538 @item show print elements
9539 Display the number of elements of a large array that @value{GDBN} will print.
9540 If the number is 0, then the printing is unlimited.
9542 @item set print frame-arguments @var{value}
9543 @kindex set print frame-arguments
9544 @cindex printing frame argument values
9545 @cindex print all frame argument values
9546 @cindex print frame argument values for scalars only
9547 @cindex do not print frame argument values
9548 This command allows to control how the values of arguments are printed
9549 when the debugger prints a frame (@pxref{Frames}). The possible
9554 The values of all arguments are printed.
9557 Print the value of an argument only if it is a scalar. The value of more
9558 complex arguments such as arrays, structures, unions, etc, is replaced
9559 by @code{@dots{}}. This is the default. Here is an example where
9560 only scalar arguments are shown:
9563 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9568 None of the argument values are printed. Instead, the value of each argument
9569 is replaced by @code{@dots{}}. In this case, the example above now becomes:
9572 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
9577 By default, only scalar arguments are printed. This command can be used
9578 to configure the debugger to print the value of all arguments, regardless
9579 of their type. However, it is often advantageous to not print the value
9580 of more complex parameters. For instance, it reduces the amount of
9581 information printed in each frame, making the backtrace more readable.
9582 Also, it improves performance when displaying Ada frames, because
9583 the computation of large arguments can sometimes be CPU-intensive,
9584 especially in large applications. Setting @code{print frame-arguments}
9585 to @code{scalars} (the default) or @code{none} avoids this computation,
9586 thus speeding up the display of each Ada frame.
9588 @item show print frame-arguments
9589 Show how the value of arguments should be displayed when printing a frame.
9591 @item set print raw frame-arguments on
9592 Print frame arguments in raw, non pretty-printed, form.
9594 @item set print raw frame-arguments off
9595 Print frame arguments in pretty-printed form, if there is a pretty-printer
9596 for the value (@pxref{Pretty Printing}),
9597 otherwise print the value in raw form.
9598 This is the default.
9600 @item show print raw frame-arguments
9601 Show whether to print frame arguments in raw form.
9603 @anchor{set print entry-values}
9604 @item set print entry-values @var{value}
9605 @kindex set print entry-values
9606 Set printing of frame argument values at function entry. In some cases
9607 @value{GDBN} can determine the value of function argument which was passed by
9608 the function caller, even if the value was modified inside the called function
9609 and therefore is different. With optimized code, the current value could be
9610 unavailable, but the entry value may still be known.
9612 The default value is @code{default} (see below for its description). Older
9613 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
9614 this feature will behave in the @code{default} setting the same way as with the
9617 This functionality is currently supported only by DWARF 2 debugging format and
9618 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9619 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9622 The @var{value} parameter can be one of the following:
9626 Print only actual parameter values, never print values from function entry
9630 #0 different (val=6)
9631 #0 lost (val=<optimized out>)
9633 #0 invalid (val=<optimized out>)
9637 Print only parameter values from function entry point. The actual parameter
9638 values are never printed.
9640 #0 equal (val@@entry=5)
9641 #0 different (val@@entry=5)
9642 #0 lost (val@@entry=5)
9643 #0 born (val@@entry=<optimized out>)
9644 #0 invalid (val@@entry=<optimized out>)
9648 Print only parameter values from function entry point. If value from function
9649 entry point is not known while the actual value is known, print the actual
9650 value for such parameter.
9652 #0 equal (val@@entry=5)
9653 #0 different (val@@entry=5)
9654 #0 lost (val@@entry=5)
9656 #0 invalid (val@@entry=<optimized out>)
9660 Print actual parameter values. If actual parameter value is not known while
9661 value from function entry point is known, print the entry point value for such
9665 #0 different (val=6)
9666 #0 lost (val@@entry=5)
9668 #0 invalid (val=<optimized out>)
9672 Always print both the actual parameter value and its value from function entry
9673 point, even if values of one or both are not available due to compiler
9676 #0 equal (val=5, val@@entry=5)
9677 #0 different (val=6, val@@entry=5)
9678 #0 lost (val=<optimized out>, val@@entry=5)
9679 #0 born (val=10, val@@entry=<optimized out>)
9680 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
9684 Print the actual parameter value if it is known and also its value from
9685 function entry point if it is known. If neither is known, print for the actual
9686 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
9687 values are known and identical, print the shortened
9688 @code{param=param@@entry=VALUE} notation.
9690 #0 equal (val=val@@entry=5)
9691 #0 different (val=6, val@@entry=5)
9692 #0 lost (val@@entry=5)
9694 #0 invalid (val=<optimized out>)
9698 Always print the actual parameter value. Print also its value from function
9699 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
9700 if both values are known and identical, print the shortened
9701 @code{param=param@@entry=VALUE} notation.
9703 #0 equal (val=val@@entry=5)
9704 #0 different (val=6, val@@entry=5)
9705 #0 lost (val=<optimized out>, val@@entry=5)
9707 #0 invalid (val=<optimized out>)
9711 For analysis messages on possible failures of frame argument values at function
9712 entry resolution see @ref{set debug entry-values}.
9714 @item show print entry-values
9715 Show the method being used for printing of frame argument values at function
9718 @item set print repeats @var{number-of-repeats}
9719 @itemx set print repeats unlimited
9720 @cindex repeated array elements
9721 Set the threshold for suppressing display of repeated array
9722 elements. When the number of consecutive identical elements of an
9723 array exceeds the threshold, @value{GDBN} prints the string
9724 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
9725 identical repetitions, instead of displaying the identical elements
9726 themselves. Setting the threshold to @code{unlimited} or zero will
9727 cause all elements to be individually printed. The default threshold
9730 @item show print repeats
9731 Display the current threshold for printing repeated identical
9734 @item set print null-stop
9735 @cindex @sc{null} elements in arrays
9736 Cause @value{GDBN} to stop printing the characters of an array when the first
9737 @sc{null} is encountered. This is useful when large arrays actually
9738 contain only short strings.
9741 @item show print null-stop
9742 Show whether @value{GDBN} stops printing an array on the first
9743 @sc{null} character.
9745 @item set print pretty on
9746 @cindex print structures in indented form
9747 @cindex indentation in structure display
9748 Cause @value{GDBN} to print structures in an indented format with one member
9749 per line, like this:
9764 @item set print pretty off
9765 Cause @value{GDBN} to print structures in a compact format, like this:
9769 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
9770 meat = 0x54 "Pork"@}
9775 This is the default format.
9777 @item show print pretty
9778 Show which format @value{GDBN} is using to print structures.
9780 @item set print sevenbit-strings on
9781 @cindex eight-bit characters in strings
9782 @cindex octal escapes in strings
9783 Print using only seven-bit characters; if this option is set,
9784 @value{GDBN} displays any eight-bit characters (in strings or
9785 character values) using the notation @code{\}@var{nnn}. This setting is
9786 best if you are working in English (@sc{ascii}) and you use the
9787 high-order bit of characters as a marker or ``meta'' bit.
9789 @item set print sevenbit-strings off
9790 Print full eight-bit characters. This allows the use of more
9791 international character sets, and is the default.
9793 @item show print sevenbit-strings
9794 Show whether or not @value{GDBN} is printing only seven-bit characters.
9796 @item set print union on
9797 @cindex unions in structures, printing
9798 Tell @value{GDBN} to print unions which are contained in structures
9799 and other unions. This is the default setting.
9801 @item set print union off
9802 Tell @value{GDBN} not to print unions which are contained in
9803 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
9806 @item show print union
9807 Ask @value{GDBN} whether or not it will print unions which are contained in
9808 structures and other unions.
9810 For example, given the declarations
9813 typedef enum @{Tree, Bug@} Species;
9814 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
9815 typedef enum @{Caterpillar, Cocoon, Butterfly@}
9826 struct thing foo = @{Tree, @{Acorn@}@};
9830 with @code{set print union on} in effect @samp{p foo} would print
9833 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
9837 and with @code{set print union off} in effect it would print
9840 $1 = @{it = Tree, form = @{...@}@}
9844 @code{set print union} affects programs written in C-like languages
9850 These settings are of interest when debugging C@t{++} programs:
9853 @cindex demangling C@t{++} names
9854 @item set print demangle
9855 @itemx set print demangle on
9856 Print C@t{++} names in their source form rather than in the encoded
9857 (``mangled'') form passed to the assembler and linker for type-safe
9858 linkage. The default is on.
9860 @item show print demangle
9861 Show whether C@t{++} names are printed in mangled or demangled form.
9863 @item set print asm-demangle
9864 @itemx set print asm-demangle on
9865 Print C@t{++} names in their source form rather than their mangled form, even
9866 in assembler code printouts such as instruction disassemblies.
9869 @item show print asm-demangle
9870 Show whether C@t{++} names in assembly listings are printed in mangled
9873 @cindex C@t{++} symbol decoding style
9874 @cindex symbol decoding style, C@t{++}
9875 @kindex set demangle-style
9876 @item set demangle-style @var{style}
9877 Choose among several encoding schemes used by different compilers to
9878 represent C@t{++} names. The choices for @var{style} are currently:
9882 Allow @value{GDBN} to choose a decoding style by inspecting your program.
9883 This is the default.
9886 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
9889 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
9892 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
9895 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
9896 @strong{Warning:} this setting alone is not sufficient to allow
9897 debugging @code{cfront}-generated executables. @value{GDBN} would
9898 require further enhancement to permit that.
9901 If you omit @var{style}, you will see a list of possible formats.
9903 @item show demangle-style
9904 Display the encoding style currently in use for decoding C@t{++} symbols.
9906 @item set print object
9907 @itemx set print object on
9908 @cindex derived type of an object, printing
9909 @cindex display derived types
9910 When displaying a pointer to an object, identify the @emph{actual}
9911 (derived) type of the object rather than the @emph{declared} type, using
9912 the virtual function table. Note that the virtual function table is
9913 required---this feature can only work for objects that have run-time
9914 type identification; a single virtual method in the object's declared
9915 type is sufficient. Note that this setting is also taken into account when
9916 working with variable objects via MI (@pxref{GDB/MI}).
9918 @item set print object off
9919 Display only the declared type of objects, without reference to the
9920 virtual function table. This is the default setting.
9922 @item show print object
9923 Show whether actual, or declared, object types are displayed.
9925 @item set print static-members
9926 @itemx set print static-members on
9927 @cindex static members of C@t{++} objects
9928 Print static members when displaying a C@t{++} object. The default is on.
9930 @item set print static-members off
9931 Do not print static members when displaying a C@t{++} object.
9933 @item show print static-members
9934 Show whether C@t{++} static members are printed or not.
9936 @item set print pascal_static-members
9937 @itemx set print pascal_static-members on
9938 @cindex static members of Pascal objects
9939 @cindex Pascal objects, static members display
9940 Print static members when displaying a Pascal object. The default is on.
9942 @item set print pascal_static-members off
9943 Do not print static members when displaying a Pascal object.
9945 @item show print pascal_static-members
9946 Show whether Pascal static members are printed or not.
9948 @c These don't work with HP ANSI C++ yet.
9949 @item set print vtbl
9950 @itemx set print vtbl on
9951 @cindex pretty print C@t{++} virtual function tables
9952 @cindex virtual functions (C@t{++}) display
9953 @cindex VTBL display
9954 Pretty print C@t{++} virtual function tables. The default is off.
9955 (The @code{vtbl} commands do not work on programs compiled with the HP
9956 ANSI C@t{++} compiler (@code{aCC}).)
9958 @item set print vtbl off
9959 Do not pretty print C@t{++} virtual function tables.
9961 @item show print vtbl
9962 Show whether C@t{++} virtual function tables are pretty printed, or not.
9965 @node Pretty Printing
9966 @section Pretty Printing
9968 @value{GDBN} provides a mechanism to allow pretty-printing of values using
9969 Python code. It greatly simplifies the display of complex objects. This
9970 mechanism works for both MI and the CLI.
9973 * Pretty-Printer Introduction:: Introduction to pretty-printers
9974 * Pretty-Printer Example:: An example pretty-printer
9975 * Pretty-Printer Commands:: Pretty-printer commands
9978 @node Pretty-Printer Introduction
9979 @subsection Pretty-Printer Introduction
9981 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
9982 registered for the value. If there is then @value{GDBN} invokes the
9983 pretty-printer to print the value. Otherwise the value is printed normally.
9985 Pretty-printers are normally named. This makes them easy to manage.
9986 The @samp{info pretty-printer} command will list all the installed
9987 pretty-printers with their names.
9988 If a pretty-printer can handle multiple data types, then its
9989 @dfn{subprinters} are the printers for the individual data types.
9990 Each such subprinter has its own name.
9991 The format of the name is @var{printer-name};@var{subprinter-name}.
9993 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
9994 Typically they are automatically loaded and registered when the corresponding
9995 debug information is loaded, thus making them available without having to
9996 do anything special.
9998 There are three places where a pretty-printer can be registered.
10002 Pretty-printers registered globally are available when debugging
10006 Pretty-printers registered with a program space are available only
10007 when debugging that program.
10008 @xref{Progspaces In Python}, for more details on program spaces in Python.
10011 Pretty-printers registered with an objfile are loaded and unloaded
10012 with the corresponding objfile (e.g., shared library).
10013 @xref{Objfiles In Python}, for more details on objfiles in Python.
10016 @xref{Selecting Pretty-Printers}, for further information on how
10017 pretty-printers are selected,
10019 @xref{Writing a Pretty-Printer}, for implementing pretty printers
10022 @node Pretty-Printer Example
10023 @subsection Pretty-Printer Example
10025 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
10028 (@value{GDBP}) print s
10030 static npos = 4294967295,
10032 <std::allocator<char>> = @{
10033 <__gnu_cxx::new_allocator<char>> = @{
10034 <No data fields>@}, <No data fields>
10036 members of std::basic_string<char, std::char_traits<char>,
10037 std::allocator<char> >::_Alloc_hider:
10038 _M_p = 0x804a014 "abcd"
10043 With a pretty-printer for @code{std::string} only the contents are printed:
10046 (@value{GDBP}) print s
10050 @node Pretty-Printer Commands
10051 @subsection Pretty-Printer Commands
10052 @cindex pretty-printer commands
10055 @kindex info pretty-printer
10056 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10057 Print the list of installed pretty-printers.
10058 This includes disabled pretty-printers, which are marked as such.
10060 @var{object-regexp} is a regular expression matching the objects
10061 whose pretty-printers to list.
10062 Objects can be @code{global}, the program space's file
10063 (@pxref{Progspaces In Python}),
10064 and the object files within that program space (@pxref{Objfiles In Python}).
10065 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
10066 looks up a printer from these three objects.
10068 @var{name-regexp} is a regular expression matching the name of the printers
10071 @kindex disable pretty-printer
10072 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10073 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10074 A disabled pretty-printer is not forgotten, it may be enabled again later.
10076 @kindex enable pretty-printer
10077 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10078 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10083 Suppose we have three pretty-printers installed: one from library1.so
10084 named @code{foo} that prints objects of type @code{foo}, and
10085 another from library2.so named @code{bar} that prints two types of objects,
10086 @code{bar1} and @code{bar2}.
10089 (gdb) info pretty-printer
10096 (gdb) info pretty-printer library2
10101 (gdb) disable pretty-printer library1
10103 2 of 3 printers enabled
10104 (gdb) info pretty-printer
10111 (gdb) disable pretty-printer library2 bar:bar1
10113 1 of 3 printers enabled
10114 (gdb) info pretty-printer library2
10121 (gdb) disable pretty-printer library2 bar
10123 0 of 3 printers enabled
10124 (gdb) info pretty-printer library2
10133 Note that for @code{bar} the entire printer can be disabled,
10134 as can each individual subprinter.
10136 @node Value History
10137 @section Value History
10139 @cindex value history
10140 @cindex history of values printed by @value{GDBN}
10141 Values printed by the @code{print} command are saved in the @value{GDBN}
10142 @dfn{value history}. This allows you to refer to them in other expressions.
10143 Values are kept until the symbol table is re-read or discarded
10144 (for example with the @code{file} or @code{symbol-file} commands).
10145 When the symbol table changes, the value history is discarded,
10146 since the values may contain pointers back to the types defined in the
10151 @cindex history number
10152 The values printed are given @dfn{history numbers} by which you can
10153 refer to them. These are successive integers starting with one.
10154 @code{print} shows you the history number assigned to a value by
10155 printing @samp{$@var{num} = } before the value; here @var{num} is the
10158 To refer to any previous value, use @samp{$} followed by the value's
10159 history number. The way @code{print} labels its output is designed to
10160 remind you of this. Just @code{$} refers to the most recent value in
10161 the history, and @code{$$} refers to the value before that.
10162 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
10163 is the value just prior to @code{$$}, @code{$$1} is equivalent to
10164 @code{$$}, and @code{$$0} is equivalent to @code{$}.
10166 For example, suppose you have just printed a pointer to a structure and
10167 want to see the contents of the structure. It suffices to type
10173 If you have a chain of structures where the component @code{next} points
10174 to the next one, you can print the contents of the next one with this:
10181 You can print successive links in the chain by repeating this
10182 command---which you can do by just typing @key{RET}.
10184 Note that the history records values, not expressions. If the value of
10185 @code{x} is 4 and you type these commands:
10193 then the value recorded in the value history by the @code{print} command
10194 remains 4 even though the value of @code{x} has changed.
10197 @kindex show values
10199 Print the last ten values in the value history, with their item numbers.
10200 This is like @samp{p@ $$9} repeated ten times, except that @code{show
10201 values} does not change the history.
10203 @item show values @var{n}
10204 Print ten history values centered on history item number @var{n}.
10206 @item show values +
10207 Print ten history values just after the values last printed. If no more
10208 values are available, @code{show values +} produces no display.
10211 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
10212 same effect as @samp{show values +}.
10214 @node Convenience Vars
10215 @section Convenience Variables
10217 @cindex convenience variables
10218 @cindex user-defined variables
10219 @value{GDBN} provides @dfn{convenience variables} that you can use within
10220 @value{GDBN} to hold on to a value and refer to it later. These variables
10221 exist entirely within @value{GDBN}; they are not part of your program, and
10222 setting a convenience variable has no direct effect on further execution
10223 of your program. That is why you can use them freely.
10225 Convenience variables are prefixed with @samp{$}. Any name preceded by
10226 @samp{$} can be used for a convenience variable, unless it is one of
10227 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
10228 (Value history references, in contrast, are @emph{numbers} preceded
10229 by @samp{$}. @xref{Value History, ,Value History}.)
10231 You can save a value in a convenience variable with an assignment
10232 expression, just as you would set a variable in your program.
10236 set $foo = *object_ptr
10240 would save in @code{$foo} the value contained in the object pointed to by
10243 Using a convenience variable for the first time creates it, but its
10244 value is @code{void} until you assign a new value. You can alter the
10245 value with another assignment at any time.
10247 Convenience variables have no fixed types. You can assign a convenience
10248 variable any type of value, including structures and arrays, even if
10249 that variable already has a value of a different type. The convenience
10250 variable, when used as an expression, has the type of its current value.
10253 @kindex show convenience
10254 @cindex show all user variables and functions
10255 @item show convenience
10256 Print a list of convenience variables used so far, and their values,
10257 as well as a list of the convenience functions.
10258 Abbreviated @code{show conv}.
10260 @kindex init-if-undefined
10261 @cindex convenience variables, initializing
10262 @item init-if-undefined $@var{variable} = @var{expression}
10263 Set a convenience variable if it has not already been set. This is useful
10264 for user-defined commands that keep some state. It is similar, in concept,
10265 to using local static variables with initializers in C (except that
10266 convenience variables are global). It can also be used to allow users to
10267 override default values used in a command script.
10269 If the variable is already defined then the expression is not evaluated so
10270 any side-effects do not occur.
10273 One of the ways to use a convenience variable is as a counter to be
10274 incremented or a pointer to be advanced. For example, to print
10275 a field from successive elements of an array of structures:
10279 print bar[$i++]->contents
10283 Repeat that command by typing @key{RET}.
10285 Some convenience variables are created automatically by @value{GDBN} and given
10286 values likely to be useful.
10289 @vindex $_@r{, convenience variable}
10291 The variable @code{$_} is automatically set by the @code{x} command to
10292 the last address examined (@pxref{Memory, ,Examining Memory}). Other
10293 commands which provide a default address for @code{x} to examine also
10294 set @code{$_} to that address; these commands include @code{info line}
10295 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
10296 except when set by the @code{x} command, in which case it is a pointer
10297 to the type of @code{$__}.
10299 @vindex $__@r{, convenience variable}
10301 The variable @code{$__} is automatically set by the @code{x} command
10302 to the value found in the last address examined. Its type is chosen
10303 to match the format in which the data was printed.
10306 @vindex $_exitcode@r{, convenience variable}
10307 When the program being debugged terminates normally, @value{GDBN}
10308 automatically sets this variable to the exit code of the program, and
10309 resets @code{$_exitsignal} to @code{void}.
10312 @vindex $_exitsignal@r{, convenience variable}
10313 When the program being debugged dies due to an uncaught signal,
10314 @value{GDBN} automatically sets this variable to that signal's number,
10315 and resets @code{$_exitcode} to @code{void}.
10317 To distinguish between whether the program being debugged has exited
10318 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
10319 @code{$_exitsignal} is not @code{void}), the convenience function
10320 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
10321 Functions}). For example, considering the following source code:
10324 #include <signal.h>
10327 main (int argc, char *argv[])
10334 A valid way of telling whether the program being debugged has exited
10335 or signalled would be:
10338 (@value{GDBP}) define has_exited_or_signalled
10339 Type commands for definition of ``has_exited_or_signalled''.
10340 End with a line saying just ``end''.
10341 >if $_isvoid ($_exitsignal)
10342 >echo The program has exited\n
10344 >echo The program has signalled\n
10350 Program terminated with signal SIGALRM, Alarm clock.
10351 The program no longer exists.
10352 (@value{GDBP}) has_exited_or_signalled
10353 The program has signalled
10356 As can be seen, @value{GDBN} correctly informs that the program being
10357 debugged has signalled, since it calls @code{raise} and raises a
10358 @code{SIGALRM} signal. If the program being debugged had not called
10359 @code{raise}, then @value{GDBN} would report a normal exit:
10362 (@value{GDBP}) has_exited_or_signalled
10363 The program has exited
10367 The variable @code{$_exception} is set to the exception object being
10368 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
10371 @itemx $_probe_arg0@dots{}$_probe_arg11
10372 Arguments to a static probe. @xref{Static Probe Points}.
10375 @vindex $_sdata@r{, inspect, convenience variable}
10376 The variable @code{$_sdata} contains extra collected static tracepoint
10377 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
10378 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
10379 if extra static tracepoint data has not been collected.
10382 @vindex $_siginfo@r{, convenience variable}
10383 The variable @code{$_siginfo} contains extra signal information
10384 (@pxref{extra signal information}). Note that @code{$_siginfo}
10385 could be empty, if the application has not yet received any signals.
10386 For example, it will be empty before you execute the @code{run} command.
10389 @vindex $_tlb@r{, convenience variable}
10390 The variable @code{$_tlb} is automatically set when debugging
10391 applications running on MS-Windows in native mode or connected to
10392 gdbserver that supports the @code{qGetTIBAddr} request.
10393 @xref{General Query Packets}.
10394 This variable contains the address of the thread information block.
10398 On HP-UX systems, if you refer to a function or variable name that
10399 begins with a dollar sign, @value{GDBN} searches for a user or system
10400 name first, before it searches for a convenience variable.
10402 @node Convenience Funs
10403 @section Convenience Functions
10405 @cindex convenience functions
10406 @value{GDBN} also supplies some @dfn{convenience functions}. These
10407 have a syntax similar to convenience variables. A convenience
10408 function can be used in an expression just like an ordinary function;
10409 however, a convenience function is implemented internally to
10412 These functions do not require @value{GDBN} to be configured with
10413 @code{Python} support, which means that they are always available.
10417 @item $_isvoid (@var{expr})
10418 @findex $_isvoid@r{, convenience function}
10419 Return one if the expression @var{expr} is @code{void}. Otherwise it
10422 A @code{void} expression is an expression where the type of the result
10423 is @code{void}. For example, you can examine a convenience variable
10424 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
10428 (@value{GDBP}) print $_exitcode
10430 (@value{GDBP}) print $_isvoid ($_exitcode)
10433 Starting program: ./a.out
10434 [Inferior 1 (process 29572) exited normally]
10435 (@value{GDBP}) print $_exitcode
10437 (@value{GDBP}) print $_isvoid ($_exitcode)
10441 In the example above, we used @code{$_isvoid} to check whether
10442 @code{$_exitcode} is @code{void} before and after the execution of the
10443 program being debugged. Before the execution there is no exit code to
10444 be examined, therefore @code{$_exitcode} is @code{void}. After the
10445 execution the program being debugged returned zero, therefore
10446 @code{$_exitcode} is zero, which means that it is not @code{void}
10449 The @code{void} expression can also be a call of a function from the
10450 program being debugged. For example, given the following function:
10459 The result of calling it inside @value{GDBN} is @code{void}:
10462 (@value{GDBP}) print foo ()
10464 (@value{GDBP}) print $_isvoid (foo ())
10466 (@value{GDBP}) set $v = foo ()
10467 (@value{GDBP}) print $v
10469 (@value{GDBP}) print $_isvoid ($v)
10475 These functions require @value{GDBN} to be configured with
10476 @code{Python} support.
10480 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
10481 @findex $_memeq@r{, convenience function}
10482 Returns one if the @var{length} bytes at the addresses given by
10483 @var{buf1} and @var{buf2} are equal.
10484 Otherwise it returns zero.
10486 @item $_regex(@var{str}, @var{regex})
10487 @findex $_regex@r{, convenience function}
10488 Returns one if the string @var{str} matches the regular expression
10489 @var{regex}. Otherwise it returns zero.
10490 The syntax of the regular expression is that specified by @code{Python}'s
10491 regular expression support.
10493 @item $_streq(@var{str1}, @var{str2})
10494 @findex $_streq@r{, convenience function}
10495 Returns one if the strings @var{str1} and @var{str2} are equal.
10496 Otherwise it returns zero.
10498 @item $_strlen(@var{str})
10499 @findex $_strlen@r{, convenience function}
10500 Returns the length of string @var{str}.
10502 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10503 @findex $_caller_is@r{, convenience function}
10504 Returns one if the calling function's name is equal to @var{name}.
10505 Otherwise it returns zero.
10507 If the optional argument @var{number_of_frames} is provided,
10508 it is the number of frames up in the stack to look.
10516 at testsuite/gdb.python/py-caller-is.c:21
10517 #1 0x00000000004005a0 in middle_func ()
10518 at testsuite/gdb.python/py-caller-is.c:27
10519 #2 0x00000000004005ab in top_func ()
10520 at testsuite/gdb.python/py-caller-is.c:33
10521 #3 0x00000000004005b6 in main ()
10522 at testsuite/gdb.python/py-caller-is.c:39
10523 (gdb) print $_caller_is ("middle_func")
10525 (gdb) print $_caller_is ("top_func", 2)
10529 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10530 @findex $_caller_matches@r{, convenience function}
10531 Returns one if the calling function's name matches the regular expression
10532 @var{regexp}. Otherwise it returns zero.
10534 If the optional argument @var{number_of_frames} is provided,
10535 it is the number of frames up in the stack to look.
10538 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10539 @findex $_any_caller_is@r{, convenience function}
10540 Returns one if any calling function's name is equal to @var{name}.
10541 Otherwise it returns zero.
10543 If the optional argument @var{number_of_frames} is provided,
10544 it is the number of frames up in the stack to look.
10547 This function differs from @code{$_caller_is} in that this function
10548 checks all stack frames from the immediate caller to the frame specified
10549 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
10550 frame specified by @var{number_of_frames}.
10552 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10553 @findex $_any_caller_matches@r{, convenience function}
10554 Returns one if any calling function's name matches the regular expression
10555 @var{regexp}. Otherwise it returns zero.
10557 If the optional argument @var{number_of_frames} is provided,
10558 it is the number of frames up in the stack to look.
10561 This function differs from @code{$_caller_matches} in that this function
10562 checks all stack frames from the immediate caller to the frame specified
10563 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
10564 frame specified by @var{number_of_frames}.
10568 @value{GDBN} provides the ability to list and get help on
10569 convenience functions.
10572 @item help function
10573 @kindex help function
10574 @cindex show all convenience functions
10575 Print a list of all convenience functions.
10582 You can refer to machine register contents, in expressions, as variables
10583 with names starting with @samp{$}. The names of registers are different
10584 for each machine; use @code{info registers} to see the names used on
10588 @kindex info registers
10589 @item info registers
10590 Print the names and values of all registers except floating-point
10591 and vector registers (in the selected stack frame).
10593 @kindex info all-registers
10594 @cindex floating point registers
10595 @item info all-registers
10596 Print the names and values of all registers, including floating-point
10597 and vector registers (in the selected stack frame).
10599 @item info registers @var{regname} @dots{}
10600 Print the @dfn{relativized} value of each specified register @var{regname}.
10601 As discussed in detail below, register values are normally relative to
10602 the selected stack frame. The @var{regname} may be any register name valid on
10603 the machine you are using, with or without the initial @samp{$}.
10606 @anchor{standard registers}
10607 @cindex stack pointer register
10608 @cindex program counter register
10609 @cindex process status register
10610 @cindex frame pointer register
10611 @cindex standard registers
10612 @value{GDBN} has four ``standard'' register names that are available (in
10613 expressions) on most machines---whenever they do not conflict with an
10614 architecture's canonical mnemonics for registers. The register names
10615 @code{$pc} and @code{$sp} are used for the program counter register and
10616 the stack pointer. @code{$fp} is used for a register that contains a
10617 pointer to the current stack frame, and @code{$ps} is used for a
10618 register that contains the processor status. For example,
10619 you could print the program counter in hex with
10626 or print the instruction to be executed next with
10633 or add four to the stack pointer@footnote{This is a way of removing
10634 one word from the stack, on machines where stacks grow downward in
10635 memory (most machines, nowadays). This assumes that the innermost
10636 stack frame is selected; setting @code{$sp} is not allowed when other
10637 stack frames are selected. To pop entire frames off the stack,
10638 regardless of machine architecture, use @code{return};
10639 see @ref{Returning, ,Returning from a Function}.} with
10645 Whenever possible, these four standard register names are available on
10646 your machine even though the machine has different canonical mnemonics,
10647 so long as there is no conflict. The @code{info registers} command
10648 shows the canonical names. For example, on the SPARC, @code{info
10649 registers} displays the processor status register as @code{$psr} but you
10650 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
10651 is an alias for the @sc{eflags} register.
10653 @value{GDBN} always considers the contents of an ordinary register as an
10654 integer when the register is examined in this way. Some machines have
10655 special registers which can hold nothing but floating point; these
10656 registers are considered to have floating point values. There is no way
10657 to refer to the contents of an ordinary register as floating point value
10658 (although you can @emph{print} it as a floating point value with
10659 @samp{print/f $@var{regname}}).
10661 Some registers have distinct ``raw'' and ``virtual'' data formats. This
10662 means that the data format in which the register contents are saved by
10663 the operating system is not the same one that your program normally
10664 sees. For example, the registers of the 68881 floating point
10665 coprocessor are always saved in ``extended'' (raw) format, but all C
10666 programs expect to work with ``double'' (virtual) format. In such
10667 cases, @value{GDBN} normally works with the virtual format only (the format
10668 that makes sense for your program), but the @code{info registers} command
10669 prints the data in both formats.
10671 @cindex SSE registers (x86)
10672 @cindex MMX registers (x86)
10673 Some machines have special registers whose contents can be interpreted
10674 in several different ways. For example, modern x86-based machines
10675 have SSE and MMX registers that can hold several values packed
10676 together in several different formats. @value{GDBN} refers to such
10677 registers in @code{struct} notation:
10680 (@value{GDBP}) print $xmm1
10682 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
10683 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
10684 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
10685 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
10686 v4_int32 = @{0, 20657912, 11, 13@},
10687 v2_int64 = @{88725056443645952, 55834574859@},
10688 uint128 = 0x0000000d0000000b013b36f800000000
10693 To set values of such registers, you need to tell @value{GDBN} which
10694 view of the register you wish to change, as if you were assigning
10695 value to a @code{struct} member:
10698 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
10701 Normally, register values are relative to the selected stack frame
10702 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
10703 value that the register would contain if all stack frames farther in
10704 were exited and their saved registers restored. In order to see the
10705 true contents of hardware registers, you must select the innermost
10706 frame (with @samp{frame 0}).
10708 @cindex caller-saved registers
10709 @cindex call-clobbered registers
10710 @cindex volatile registers
10711 @cindex <not saved> values
10712 Usually ABIs reserve some registers as not needed to be saved by the
10713 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
10714 registers). It may therefore not be possible for @value{GDBN} to know
10715 the value a register had before the call (in other words, in the outer
10716 frame), if the register value has since been changed by the callee.
10717 @value{GDBN} tries to deduce where the inner frame saved
10718 (``callee-saved'') registers, from the debug info, unwind info, or the
10719 machine code generated by your compiler. If some register is not
10720 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
10721 its own knowledge of the ABI, or because the debug/unwind info
10722 explicitly says the register's value is undefined), @value{GDBN}
10723 displays @w{@samp{<not saved>}} as the register's value. With targets
10724 that @value{GDBN} has no knowledge of the register saving convention,
10725 if a register was not saved by the callee, then its value and location
10726 in the outer frame are assumed to be the same of the inner frame.
10727 This is usually harmless, because if the register is call-clobbered,
10728 the caller either does not care what is in the register after the
10729 call, or has code to restore the value that it does care about. Note,
10730 however, that if you change such a register in the outer frame, you
10731 may also be affecting the inner frame. Also, the more ``outer'' the
10732 frame is you're looking at, the more likely a call-clobbered
10733 register's value is to be wrong, in the sense that it doesn't actually
10734 represent the value the register had just before the call.
10736 @node Floating Point Hardware
10737 @section Floating Point Hardware
10738 @cindex floating point
10740 Depending on the configuration, @value{GDBN} may be able to give
10741 you more information about the status of the floating point hardware.
10746 Display hardware-dependent information about the floating
10747 point unit. The exact contents and layout vary depending on the
10748 floating point chip. Currently, @samp{info float} is supported on
10749 the ARM and x86 machines.
10753 @section Vector Unit
10754 @cindex vector unit
10756 Depending on the configuration, @value{GDBN} may be able to give you
10757 more information about the status of the vector unit.
10760 @kindex info vector
10762 Display information about the vector unit. The exact contents and
10763 layout vary depending on the hardware.
10766 @node OS Information
10767 @section Operating System Auxiliary Information
10768 @cindex OS information
10770 @value{GDBN} provides interfaces to useful OS facilities that can help
10771 you debug your program.
10773 @cindex auxiliary vector
10774 @cindex vector, auxiliary
10775 Some operating systems supply an @dfn{auxiliary vector} to programs at
10776 startup. This is akin to the arguments and environment that you
10777 specify for a program, but contains a system-dependent variety of
10778 binary values that tell system libraries important details about the
10779 hardware, operating system, and process. Each value's purpose is
10780 identified by an integer tag; the meanings are well-known but system-specific.
10781 Depending on the configuration and operating system facilities,
10782 @value{GDBN} may be able to show you this information. For remote
10783 targets, this functionality may further depend on the remote stub's
10784 support of the @samp{qXfer:auxv:read} packet, see
10785 @ref{qXfer auxiliary vector read}.
10790 Display the auxiliary vector of the inferior, which can be either a
10791 live process or a core dump file. @value{GDBN} prints each tag value
10792 numerically, and also shows names and text descriptions for recognized
10793 tags. Some values in the vector are numbers, some bit masks, and some
10794 pointers to strings or other data. @value{GDBN} displays each value in the
10795 most appropriate form for a recognized tag, and in hexadecimal for
10796 an unrecognized tag.
10799 On some targets, @value{GDBN} can access operating system-specific
10800 information and show it to you. The types of information available
10801 will differ depending on the type of operating system running on the
10802 target. The mechanism used to fetch the data is described in
10803 @ref{Operating System Information}. For remote targets, this
10804 functionality depends on the remote stub's support of the
10805 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
10809 @item info os @var{infotype}
10811 Display OS information of the requested type.
10813 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
10815 @anchor{linux info os infotypes}
10817 @kindex info os cpus
10819 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
10820 the available fields from /proc/cpuinfo. For each supported architecture
10821 different fields are available. Two common entries are processor which gives
10822 CPU number and bogomips; a system constant that is calculated during
10823 kernel initialization.
10825 @kindex info os files
10827 Display the list of open file descriptors on the target. For each
10828 file descriptor, @value{GDBN} prints the identifier of the process
10829 owning the descriptor, the command of the owning process, the value
10830 of the descriptor, and the target of the descriptor.
10832 @kindex info os modules
10834 Display the list of all loaded kernel modules on the target. For each
10835 module, @value{GDBN} prints the module name, the size of the module in
10836 bytes, the number of times the module is used, the dependencies of the
10837 module, the status of the module, and the address of the loaded module
10840 @kindex info os msg
10842 Display the list of all System V message queues on the target. For each
10843 message queue, @value{GDBN} prints the message queue key, the message
10844 queue identifier, the access permissions, the current number of bytes
10845 on the queue, the current number of messages on the queue, the processes
10846 that last sent and received a message on the queue, the user and group
10847 of the owner and creator of the message queue, the times at which a
10848 message was last sent and received on the queue, and the time at which
10849 the message queue was last changed.
10851 @kindex info os processes
10853 Display the list of processes on the target. For each process,
10854 @value{GDBN} prints the process identifier, the name of the user, the
10855 command corresponding to the process, and the list of processor cores
10856 that the process is currently running on. (To understand what these
10857 properties mean, for this and the following info types, please consult
10858 the general @sc{gnu}/Linux documentation.)
10860 @kindex info os procgroups
10862 Display the list of process groups on the target. For each process,
10863 @value{GDBN} prints the identifier of the process group that it belongs
10864 to, the command corresponding to the process group leader, the process
10865 identifier, and the command line of the process. The list is sorted
10866 first by the process group identifier, then by the process identifier,
10867 so that processes belonging to the same process group are grouped together
10868 and the process group leader is listed first.
10870 @kindex info os semaphores
10872 Display the list of all System V semaphore sets on the target. For each
10873 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
10874 set identifier, the access permissions, the number of semaphores in the
10875 set, the user and group of the owner and creator of the semaphore set,
10876 and the times at which the semaphore set was operated upon and changed.
10878 @kindex info os shm
10880 Display the list of all System V shared-memory regions on the target.
10881 For each shared-memory region, @value{GDBN} prints the region key,
10882 the shared-memory identifier, the access permissions, the size of the
10883 region, the process that created the region, the process that last
10884 attached to or detached from the region, the current number of live
10885 attaches to the region, and the times at which the region was last
10886 attached to, detach from, and changed.
10888 @kindex info os sockets
10890 Display the list of Internet-domain sockets on the target. For each
10891 socket, @value{GDBN} prints the address and port of the local and
10892 remote endpoints, the current state of the connection, the creator of
10893 the socket, the IP address family of the socket, and the type of the
10896 @kindex info os threads
10898 Display the list of threads running on the target. For each thread,
10899 @value{GDBN} prints the identifier of the process that the thread
10900 belongs to, the command of the process, the thread identifier, and the
10901 processor core that it is currently running on. The main thread of a
10902 process is not listed.
10906 If @var{infotype} is omitted, then list the possible values for
10907 @var{infotype} and the kind of OS information available for each
10908 @var{infotype}. If the target does not return a list of possible
10909 types, this command will report an error.
10912 @node Memory Region Attributes
10913 @section Memory Region Attributes
10914 @cindex memory region attributes
10916 @dfn{Memory region attributes} allow you to describe special handling
10917 required by regions of your target's memory. @value{GDBN} uses
10918 attributes to determine whether to allow certain types of memory
10919 accesses; whether to use specific width accesses; and whether to cache
10920 target memory. By default the description of memory regions is
10921 fetched from the target (if the current target supports this), but the
10922 user can override the fetched regions.
10924 Defined memory regions can be individually enabled and disabled. When a
10925 memory region is disabled, @value{GDBN} uses the default attributes when
10926 accessing memory in that region. Similarly, if no memory regions have
10927 been defined, @value{GDBN} uses the default attributes when accessing
10930 When a memory region is defined, it is given a number to identify it;
10931 to enable, disable, or remove a memory region, you specify that number.
10935 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
10936 Define a memory region bounded by @var{lower} and @var{upper} with
10937 attributes @var{attributes}@dots{}, and add it to the list of regions
10938 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
10939 case: it is treated as the target's maximum memory address.
10940 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
10943 Discard any user changes to the memory regions and use target-supplied
10944 regions, if available, or no regions if the target does not support.
10947 @item delete mem @var{nums}@dots{}
10948 Remove memory regions @var{nums}@dots{} from the list of regions
10949 monitored by @value{GDBN}.
10951 @kindex disable mem
10952 @item disable mem @var{nums}@dots{}
10953 Disable monitoring of memory regions @var{nums}@dots{}.
10954 A disabled memory region is not forgotten.
10955 It may be enabled again later.
10958 @item enable mem @var{nums}@dots{}
10959 Enable monitoring of memory regions @var{nums}@dots{}.
10963 Print a table of all defined memory regions, with the following columns
10967 @item Memory Region Number
10968 @item Enabled or Disabled.
10969 Enabled memory regions are marked with @samp{y}.
10970 Disabled memory regions are marked with @samp{n}.
10973 The address defining the inclusive lower bound of the memory region.
10976 The address defining the exclusive upper bound of the memory region.
10979 The list of attributes set for this memory region.
10984 @subsection Attributes
10986 @subsubsection Memory Access Mode
10987 The access mode attributes set whether @value{GDBN} may make read or
10988 write accesses to a memory region.
10990 While these attributes prevent @value{GDBN} from performing invalid
10991 memory accesses, they do nothing to prevent the target system, I/O DMA,
10992 etc.@: from accessing memory.
10996 Memory is read only.
10998 Memory is write only.
11000 Memory is read/write. This is the default.
11003 @subsubsection Memory Access Size
11004 The access size attribute tells @value{GDBN} to use specific sized
11005 accesses in the memory region. Often memory mapped device registers
11006 require specific sized accesses. If no access size attribute is
11007 specified, @value{GDBN} may use accesses of any size.
11011 Use 8 bit memory accesses.
11013 Use 16 bit memory accesses.
11015 Use 32 bit memory accesses.
11017 Use 64 bit memory accesses.
11020 @c @subsubsection Hardware/Software Breakpoints
11021 @c The hardware/software breakpoint attributes set whether @value{GDBN}
11022 @c will use hardware or software breakpoints for the internal breakpoints
11023 @c used by the step, next, finish, until, etc. commands.
11027 @c Always use hardware breakpoints
11028 @c @item swbreak (default)
11031 @subsubsection Data Cache
11032 The data cache attributes set whether @value{GDBN} will cache target
11033 memory. While this generally improves performance by reducing debug
11034 protocol overhead, it can lead to incorrect results because @value{GDBN}
11035 does not know about volatile variables or memory mapped device
11040 Enable @value{GDBN} to cache target memory.
11042 Disable @value{GDBN} from caching target memory. This is the default.
11045 @subsection Memory Access Checking
11046 @value{GDBN} can be instructed to refuse accesses to memory that is
11047 not explicitly described. This can be useful if accessing such
11048 regions has undesired effects for a specific target, or to provide
11049 better error checking. The following commands control this behaviour.
11052 @kindex set mem inaccessible-by-default
11053 @item set mem inaccessible-by-default [on|off]
11054 If @code{on} is specified, make @value{GDBN} treat memory not
11055 explicitly described by the memory ranges as non-existent and refuse accesses
11056 to such memory. The checks are only performed if there's at least one
11057 memory range defined. If @code{off} is specified, make @value{GDBN}
11058 treat the memory not explicitly described by the memory ranges as RAM.
11059 The default value is @code{on}.
11060 @kindex show mem inaccessible-by-default
11061 @item show mem inaccessible-by-default
11062 Show the current handling of accesses to unknown memory.
11066 @c @subsubsection Memory Write Verification
11067 @c The memory write verification attributes set whether @value{GDBN}
11068 @c will re-reads data after each write to verify the write was successful.
11072 @c @item noverify (default)
11075 @node Dump/Restore Files
11076 @section Copy Between Memory and a File
11077 @cindex dump/restore files
11078 @cindex append data to a file
11079 @cindex dump data to a file
11080 @cindex restore data from a file
11082 You can use the commands @code{dump}, @code{append}, and
11083 @code{restore} to copy data between target memory and a file. The
11084 @code{dump} and @code{append} commands write data to a file, and the
11085 @code{restore} command reads data from a file back into the inferior's
11086 memory. Files may be in binary, Motorola S-record, Intel hex,
11087 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
11088 append to binary files, and cannot read from Verilog Hex files.
11093 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11094 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
11095 Dump the contents of memory from @var{start_addr} to @var{end_addr},
11096 or the value of @var{expr}, to @var{filename} in the given format.
11098 The @var{format} parameter may be any one of:
11105 Motorola S-record format.
11107 Tektronix Hex format.
11109 Verilog Hex format.
11112 @value{GDBN} uses the same definitions of these formats as the
11113 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
11114 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
11118 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11119 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
11120 Append the contents of memory from @var{start_addr} to @var{end_addr},
11121 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
11122 (@value{GDBN} can only append data to files in raw binary form.)
11125 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
11126 Restore the contents of file @var{filename} into memory. The
11127 @code{restore} command can automatically recognize any known @sc{bfd}
11128 file format, except for raw binary. To restore a raw binary file you
11129 must specify the optional keyword @code{binary} after the filename.
11131 If @var{bias} is non-zero, its value will be added to the addresses
11132 contained in the file. Binary files always start at address zero, so
11133 they will be restored at address @var{bias}. Other bfd files have
11134 a built-in location; they will be restored at offset @var{bias}
11135 from that location.
11137 If @var{start} and/or @var{end} are non-zero, then only data between
11138 file offset @var{start} and file offset @var{end} will be restored.
11139 These offsets are relative to the addresses in the file, before
11140 the @var{bias} argument is applied.
11144 @node Core File Generation
11145 @section How to Produce a Core File from Your Program
11146 @cindex dump core from inferior
11148 A @dfn{core file} or @dfn{core dump} is a file that records the memory
11149 image of a running process and its process status (register values
11150 etc.). Its primary use is post-mortem debugging of a program that
11151 crashed while it ran outside a debugger. A program that crashes
11152 automatically produces a core file, unless this feature is disabled by
11153 the user. @xref{Files}, for information on invoking @value{GDBN} in
11154 the post-mortem debugging mode.
11156 Occasionally, you may wish to produce a core file of the program you
11157 are debugging in order to preserve a snapshot of its state.
11158 @value{GDBN} has a special command for that.
11162 @kindex generate-core-file
11163 @item generate-core-file [@var{file}]
11164 @itemx gcore [@var{file}]
11165 Produce a core dump of the inferior process. The optional argument
11166 @var{file} specifies the file name where to put the core dump. If not
11167 specified, the file name defaults to @file{core.@var{pid}}, where
11168 @var{pid} is the inferior process ID.
11170 Note that this command is implemented only for some systems (as of
11171 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
11173 On @sc{gnu}/Linux, this command can take into account the value of the
11174 file @file{/proc/@var{pid}/coredump_filter} when generating the core
11175 dump (@pxref{set use-coredump-filter}).
11177 @kindex set use-coredump-filter
11178 @anchor{set use-coredump-filter}
11179 @item set use-coredump-filter on
11180 @itemx set use-coredump-filter off
11181 Enable or disable the use of the file
11182 @file{/proc/@var{pid}/coredump_filter} when generating core dump
11183 files. This file is used by the Linux kernel to decide what types of
11184 memory mappings will be dumped or ignored when generating a core dump
11185 file. @var{pid} is the process ID of a currently running process.
11187 To make use of this feature, you have to write in the
11188 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
11189 which is a bit mask representing the memory mapping types. If a bit
11190 is set in the bit mask, then the memory mappings of the corresponding
11191 types will be dumped; otherwise, they will be ignored. This
11192 configuration is inherited by child processes. For more information
11193 about the bits that can be set in the
11194 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
11195 manpage of @code{core(5)}.
11197 By default, this option is @code{on}. If this option is turned
11198 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
11199 and instead uses the same default value as the Linux kernel in order
11200 to decide which pages will be dumped in the core dump file. This
11201 value is currently @code{0x33}, which means that bits @code{0}
11202 (anonymous private mappings), @code{1} (anonymous shared mappings),
11203 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
11204 This will cause these memory mappings to be dumped automatically.
11207 @node Character Sets
11208 @section Character Sets
11209 @cindex character sets
11211 @cindex translating between character sets
11212 @cindex host character set
11213 @cindex target character set
11215 If the program you are debugging uses a different character set to
11216 represent characters and strings than the one @value{GDBN} uses itself,
11217 @value{GDBN} can automatically translate between the character sets for
11218 you. The character set @value{GDBN} uses we call the @dfn{host
11219 character set}; the one the inferior program uses we call the
11220 @dfn{target character set}.
11222 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
11223 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
11224 remote protocol (@pxref{Remote Debugging}) to debug a program
11225 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
11226 then the host character set is Latin-1, and the target character set is
11227 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
11228 target-charset EBCDIC-US}, then @value{GDBN} translates between
11229 @sc{ebcdic} and Latin 1 as you print character or string values, or use
11230 character and string literals in expressions.
11232 @value{GDBN} has no way to automatically recognize which character set
11233 the inferior program uses; you must tell it, using the @code{set
11234 target-charset} command, described below.
11236 Here are the commands for controlling @value{GDBN}'s character set
11240 @item set target-charset @var{charset}
11241 @kindex set target-charset
11242 Set the current target character set to @var{charset}. To display the
11243 list of supported target character sets, type
11244 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
11246 @item set host-charset @var{charset}
11247 @kindex set host-charset
11248 Set the current host character set to @var{charset}.
11250 By default, @value{GDBN} uses a host character set appropriate to the
11251 system it is running on; you can override that default using the
11252 @code{set host-charset} command. On some systems, @value{GDBN} cannot
11253 automatically determine the appropriate host character set. In this
11254 case, @value{GDBN} uses @samp{UTF-8}.
11256 @value{GDBN} can only use certain character sets as its host character
11257 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
11258 @value{GDBN} will list the host character sets it supports.
11260 @item set charset @var{charset}
11261 @kindex set charset
11262 Set the current host and target character sets to @var{charset}. As
11263 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
11264 @value{GDBN} will list the names of the character sets that can be used
11265 for both host and target.
11268 @kindex show charset
11269 Show the names of the current host and target character sets.
11271 @item show host-charset
11272 @kindex show host-charset
11273 Show the name of the current host character set.
11275 @item show target-charset
11276 @kindex show target-charset
11277 Show the name of the current target character set.
11279 @item set target-wide-charset @var{charset}
11280 @kindex set target-wide-charset
11281 Set the current target's wide character set to @var{charset}. This is
11282 the character set used by the target's @code{wchar_t} type. To
11283 display the list of supported wide character sets, type
11284 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
11286 @item show target-wide-charset
11287 @kindex show target-wide-charset
11288 Show the name of the current target's wide character set.
11291 Here is an example of @value{GDBN}'s character set support in action.
11292 Assume that the following source code has been placed in the file
11293 @file{charset-test.c}:
11299 = @{72, 101, 108, 108, 111, 44, 32, 119,
11300 111, 114, 108, 100, 33, 10, 0@};
11301 char ibm1047_hello[]
11302 = @{200, 133, 147, 147, 150, 107, 64, 166,
11303 150, 153, 147, 132, 90, 37, 0@};
11307 printf ("Hello, world!\n");
11311 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
11312 containing the string @samp{Hello, world!} followed by a newline,
11313 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
11315 We compile the program, and invoke the debugger on it:
11318 $ gcc -g charset-test.c -o charset-test
11319 $ gdb -nw charset-test
11320 GNU gdb 2001-12-19-cvs
11321 Copyright 2001 Free Software Foundation, Inc.
11326 We can use the @code{show charset} command to see what character sets
11327 @value{GDBN} is currently using to interpret and display characters and
11331 (@value{GDBP}) show charset
11332 The current host and target character set is `ISO-8859-1'.
11336 For the sake of printing this manual, let's use @sc{ascii} as our
11337 initial character set:
11339 (@value{GDBP}) set charset ASCII
11340 (@value{GDBP}) show charset
11341 The current host and target character set is `ASCII'.
11345 Let's assume that @sc{ascii} is indeed the correct character set for our
11346 host system --- in other words, let's assume that if @value{GDBN} prints
11347 characters using the @sc{ascii} character set, our terminal will display
11348 them properly. Since our current target character set is also
11349 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
11352 (@value{GDBP}) print ascii_hello
11353 $1 = 0x401698 "Hello, world!\n"
11354 (@value{GDBP}) print ascii_hello[0]
11359 @value{GDBN} uses the target character set for character and string
11360 literals you use in expressions:
11363 (@value{GDBP}) print '+'
11368 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
11371 @value{GDBN} relies on the user to tell it which character set the
11372 target program uses. If we print @code{ibm1047_hello} while our target
11373 character set is still @sc{ascii}, we get jibberish:
11376 (@value{GDBP}) print ibm1047_hello
11377 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
11378 (@value{GDBP}) print ibm1047_hello[0]
11383 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
11384 @value{GDBN} tells us the character sets it supports:
11387 (@value{GDBP}) set target-charset
11388 ASCII EBCDIC-US IBM1047 ISO-8859-1
11389 (@value{GDBP}) set target-charset
11392 We can select @sc{ibm1047} as our target character set, and examine the
11393 program's strings again. Now the @sc{ascii} string is wrong, but
11394 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
11395 target character set, @sc{ibm1047}, to the host character set,
11396 @sc{ascii}, and they display correctly:
11399 (@value{GDBP}) set target-charset IBM1047
11400 (@value{GDBP}) show charset
11401 The current host character set is `ASCII'.
11402 The current target character set is `IBM1047'.
11403 (@value{GDBP}) print ascii_hello
11404 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
11405 (@value{GDBP}) print ascii_hello[0]
11407 (@value{GDBP}) print ibm1047_hello
11408 $8 = 0x4016a8 "Hello, world!\n"
11409 (@value{GDBP}) print ibm1047_hello[0]
11414 As above, @value{GDBN} uses the target character set for character and
11415 string literals you use in expressions:
11418 (@value{GDBP}) print '+'
11423 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
11426 @node Caching Target Data
11427 @section Caching Data of Targets
11428 @cindex caching data of targets
11430 @value{GDBN} caches data exchanged between the debugger and a target.
11431 Each cache is associated with the address space of the inferior.
11432 @xref{Inferiors and Programs}, about inferior and address space.
11433 Such caching generally improves performance in remote debugging
11434 (@pxref{Remote Debugging}), because it reduces the overhead of the
11435 remote protocol by bundling memory reads and writes into large chunks.
11436 Unfortunately, simply caching everything would lead to incorrect results,
11437 since @value{GDBN} does not necessarily know anything about volatile
11438 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
11439 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
11441 Therefore, by default, @value{GDBN} only caches data
11442 known to be on the stack@footnote{In non-stop mode, it is moderately
11443 rare for a running thread to modify the stack of a stopped thread
11444 in a way that would interfere with a backtrace, and caching of
11445 stack reads provides a significant speed up of remote backtraces.} or
11446 in the code segment.
11447 Other regions of memory can be explicitly marked as
11448 cacheable; @pxref{Memory Region Attributes}.
11451 @kindex set remotecache
11452 @item set remotecache on
11453 @itemx set remotecache off
11454 This option no longer does anything; it exists for compatibility
11457 @kindex show remotecache
11458 @item show remotecache
11459 Show the current state of the obsolete remotecache flag.
11461 @kindex set stack-cache
11462 @item set stack-cache on
11463 @itemx set stack-cache off
11464 Enable or disable caching of stack accesses. When @code{on}, use
11465 caching. By default, this option is @code{on}.
11467 @kindex show stack-cache
11468 @item show stack-cache
11469 Show the current state of data caching for memory accesses.
11471 @kindex set code-cache
11472 @item set code-cache on
11473 @itemx set code-cache off
11474 Enable or disable caching of code segment accesses. When @code{on},
11475 use caching. By default, this option is @code{on}. This improves
11476 performance of disassembly in remote debugging.
11478 @kindex show code-cache
11479 @item show code-cache
11480 Show the current state of target memory cache for code segment
11483 @kindex info dcache
11484 @item info dcache @r{[}line@r{]}
11485 Print the information about the performance of data cache of the
11486 current inferior's address space. The information displayed
11487 includes the dcache width and depth, and for each cache line, its
11488 number, address, and how many times it was referenced. This
11489 command is useful for debugging the data cache operation.
11491 If a line number is specified, the contents of that line will be
11494 @item set dcache size @var{size}
11495 @cindex dcache size
11496 @kindex set dcache size
11497 Set maximum number of entries in dcache (dcache depth above).
11499 @item set dcache line-size @var{line-size}
11500 @cindex dcache line-size
11501 @kindex set dcache line-size
11502 Set number of bytes each dcache entry caches (dcache width above).
11503 Must be a power of 2.
11505 @item show dcache size
11506 @kindex show dcache size
11507 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
11509 @item show dcache line-size
11510 @kindex show dcache line-size
11511 Show default size of dcache lines.
11515 @node Searching Memory
11516 @section Search Memory
11517 @cindex searching memory
11519 Memory can be searched for a particular sequence of bytes with the
11520 @code{find} command.
11524 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11525 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11526 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
11527 etc. The search begins at address @var{start_addr} and continues for either
11528 @var{len} bytes or through to @var{end_addr} inclusive.
11531 @var{s} and @var{n} are optional parameters.
11532 They may be specified in either order, apart or together.
11535 @item @var{s}, search query size
11536 The size of each search query value.
11542 halfwords (two bytes)
11546 giant words (eight bytes)
11549 All values are interpreted in the current language.
11550 This means, for example, that if the current source language is C/C@t{++}
11551 then searching for the string ``hello'' includes the trailing '\0'.
11553 If the value size is not specified, it is taken from the
11554 value's type in the current language.
11555 This is useful when one wants to specify the search
11556 pattern as a mixture of types.
11557 Note that this means, for example, that in the case of C-like languages
11558 a search for an untyped 0x42 will search for @samp{(int) 0x42}
11559 which is typically four bytes.
11561 @item @var{n}, maximum number of finds
11562 The maximum number of matches to print. The default is to print all finds.
11565 You can use strings as search values. Quote them with double-quotes
11567 The string value is copied into the search pattern byte by byte,
11568 regardless of the endianness of the target and the size specification.
11570 The address of each match found is printed as well as a count of the
11571 number of matches found.
11573 The address of the last value found is stored in convenience variable
11575 A count of the number of matches is stored in @samp{$numfound}.
11577 For example, if stopped at the @code{printf} in this function:
11583 static char hello[] = "hello-hello";
11584 static struct @{ char c; short s; int i; @}
11585 __attribute__ ((packed)) mixed
11586 = @{ 'c', 0x1234, 0x87654321 @};
11587 printf ("%s\n", hello);
11592 you get during debugging:
11595 (gdb) find &hello[0], +sizeof(hello), "hello"
11596 0x804956d <hello.1620+6>
11598 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
11599 0x8049567 <hello.1620>
11600 0x804956d <hello.1620+6>
11602 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
11603 0x8049567 <hello.1620>
11605 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
11606 0x8049560 <mixed.1625>
11608 (gdb) print $numfound
11611 $2 = (void *) 0x8049560
11614 @node Optimized Code
11615 @chapter Debugging Optimized Code
11616 @cindex optimized code, debugging
11617 @cindex debugging optimized code
11619 Almost all compilers support optimization. With optimization
11620 disabled, the compiler generates assembly code that corresponds
11621 directly to your source code, in a simplistic way. As the compiler
11622 applies more powerful optimizations, the generated assembly code
11623 diverges from your original source code. With help from debugging
11624 information generated by the compiler, @value{GDBN} can map from
11625 the running program back to constructs from your original source.
11627 @value{GDBN} is more accurate with optimization disabled. If you
11628 can recompile without optimization, it is easier to follow the
11629 progress of your program during debugging. But, there are many cases
11630 where you may need to debug an optimized version.
11632 When you debug a program compiled with @samp{-g -O}, remember that the
11633 optimizer has rearranged your code; the debugger shows you what is
11634 really there. Do not be too surprised when the execution path does not
11635 exactly match your source file! An extreme example: if you define a
11636 variable, but never use it, @value{GDBN} never sees that
11637 variable---because the compiler optimizes it out of existence.
11639 Some things do not work as well with @samp{-g -O} as with just
11640 @samp{-g}, particularly on machines with instruction scheduling. If in
11641 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
11642 please report it to us as a bug (including a test case!).
11643 @xref{Variables}, for more information about debugging optimized code.
11646 * Inline Functions:: How @value{GDBN} presents inlining
11647 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
11650 @node Inline Functions
11651 @section Inline Functions
11652 @cindex inline functions, debugging
11654 @dfn{Inlining} is an optimization that inserts a copy of the function
11655 body directly at each call site, instead of jumping to a shared
11656 routine. @value{GDBN} displays inlined functions just like
11657 non-inlined functions. They appear in backtraces. You can view their
11658 arguments and local variables, step into them with @code{step}, skip
11659 them with @code{next}, and escape from them with @code{finish}.
11660 You can check whether a function was inlined by using the
11661 @code{info frame} command.
11663 For @value{GDBN} to support inlined functions, the compiler must
11664 record information about inlining in the debug information ---
11665 @value{NGCC} using the @sc{dwarf 2} format does this, and several
11666 other compilers do also. @value{GDBN} only supports inlined functions
11667 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
11668 do not emit two required attributes (@samp{DW_AT_call_file} and
11669 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
11670 function calls with earlier versions of @value{NGCC}. It instead
11671 displays the arguments and local variables of inlined functions as
11672 local variables in the caller.
11674 The body of an inlined function is directly included at its call site;
11675 unlike a non-inlined function, there are no instructions devoted to
11676 the call. @value{GDBN} still pretends that the call site and the
11677 start of the inlined function are different instructions. Stepping to
11678 the call site shows the call site, and then stepping again shows
11679 the first line of the inlined function, even though no additional
11680 instructions are executed.
11682 This makes source-level debugging much clearer; you can see both the
11683 context of the call and then the effect of the call. Only stepping by
11684 a single instruction using @code{stepi} or @code{nexti} does not do
11685 this; single instruction steps always show the inlined body.
11687 There are some ways that @value{GDBN} does not pretend that inlined
11688 function calls are the same as normal calls:
11692 Setting breakpoints at the call site of an inlined function may not
11693 work, because the call site does not contain any code. @value{GDBN}
11694 may incorrectly move the breakpoint to the next line of the enclosing
11695 function, after the call. This limitation will be removed in a future
11696 version of @value{GDBN}; until then, set a breakpoint on an earlier line
11697 or inside the inlined function instead.
11700 @value{GDBN} cannot locate the return value of inlined calls after
11701 using the @code{finish} command. This is a limitation of compiler-generated
11702 debugging information; after @code{finish}, you can step to the next line
11703 and print a variable where your program stored the return value.
11707 @node Tail Call Frames
11708 @section Tail Call Frames
11709 @cindex tail call frames, debugging
11711 Function @code{B} can call function @code{C} in its very last statement. In
11712 unoptimized compilation the call of @code{C} is immediately followed by return
11713 instruction at the end of @code{B} code. Optimizing compiler may replace the
11714 call and return in function @code{B} into one jump to function @code{C}
11715 instead. Such use of a jump instruction is called @dfn{tail call}.
11717 During execution of function @code{C}, there will be no indication in the
11718 function call stack frames that it was tail-called from @code{B}. If function
11719 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
11720 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
11721 some cases @value{GDBN} can determine that @code{C} was tail-called from
11722 @code{B}, and it will then create fictitious call frame for that, with the
11723 return address set up as if @code{B} called @code{C} normally.
11725 This functionality is currently supported only by DWARF 2 debugging format and
11726 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
11727 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11730 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
11731 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
11735 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
11737 Stack level 1, frame at 0x7fffffffda30:
11738 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
11739 tail call frame, caller of frame at 0x7fffffffda30
11740 source language c++.
11741 Arglist at unknown address.
11742 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
11745 The detection of all the possible code path executions can find them ambiguous.
11746 There is no execution history stored (possible @ref{Reverse Execution} is never
11747 used for this purpose) and the last known caller could have reached the known
11748 callee by multiple different jump sequences. In such case @value{GDBN} still
11749 tries to show at least all the unambiguous top tail callers and all the
11750 unambiguous bottom tail calees, if any.
11753 @anchor{set debug entry-values}
11754 @item set debug entry-values
11755 @kindex set debug entry-values
11756 When set to on, enables printing of analysis messages for both frame argument
11757 values at function entry and tail calls. It will show all the possible valid
11758 tail calls code paths it has considered. It will also print the intersection
11759 of them with the final unambiguous (possibly partial or even empty) code path
11762 @item show debug entry-values
11763 @kindex show debug entry-values
11764 Show the current state of analysis messages printing for both frame argument
11765 values at function entry and tail calls.
11768 The analysis messages for tail calls can for example show why the virtual tail
11769 call frame for function @code{c} has not been recognized (due to the indirect
11770 reference by variable @code{x}):
11773 static void __attribute__((noinline, noclone)) c (void);
11774 void (*x) (void) = c;
11775 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11776 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
11777 int main (void) @{ x (); return 0; @}
11779 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
11780 DW_TAG_GNU_call_site 0x40039a in main
11782 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11785 #1 0x000000000040039a in main () at t.c:5
11788 Another possibility is an ambiguous virtual tail call frames resolution:
11792 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
11793 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
11794 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
11795 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
11796 static void __attribute__((noinline, noclone)) b (void)
11797 @{ if (i) c (); else e (); @}
11798 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
11799 int main (void) @{ a (); return 0; @}
11801 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
11802 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
11803 tailcall: reduced: 0x4004d2(a) |
11806 #1 0x00000000004004d2 in a () at t.c:8
11807 #2 0x0000000000400395 in main () at t.c:9
11810 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
11811 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
11813 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
11814 @ifset HAVE_MAKEINFO_CLICK
11815 @set ARROW @click{}
11816 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
11817 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
11819 @ifclear HAVE_MAKEINFO_CLICK
11821 @set CALLSEQ1B @value{CALLSEQ1A}
11822 @set CALLSEQ2B @value{CALLSEQ2A}
11825 Frames #0 and #2 are real, #1 is a virtual tail call frame.
11826 The code can have possible execution paths @value{CALLSEQ1B} or
11827 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
11829 @code{initial:} state shows some random possible calling sequence @value{GDBN}
11830 has found. It then finds another possible calling sequcen - that one is
11831 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
11832 printed as the @code{reduced:} calling sequence. That one could have many
11833 futher @code{compare:} and @code{reduced:} statements as long as there remain
11834 any non-ambiguous sequence entries.
11836 For the frame of function @code{b} in both cases there are different possible
11837 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
11838 also ambigous. The only non-ambiguous frame is the one for function @code{a},
11839 therefore this one is displayed to the user while the ambiguous frames are
11842 There can be also reasons why printing of frame argument values at function
11847 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
11848 static void __attribute__((noinline, noclone)) a (int i);
11849 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
11850 static void __attribute__((noinline, noclone)) a (int i)
11851 @{ if (i) b (i - 1); else c (0); @}
11852 int main (void) @{ a (5); return 0; @}
11855 #0 c (i=i@@entry=0) at t.c:2
11856 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
11857 function "a" at 0x400420 can call itself via tail calls
11858 i=<optimized out>) at t.c:6
11859 #2 0x000000000040036e in main () at t.c:7
11862 @value{GDBN} cannot find out from the inferior state if and how many times did
11863 function @code{a} call itself (via function @code{b}) as these calls would be
11864 tail calls. Such tail calls would modify thue @code{i} variable, therefore
11865 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
11866 prints @code{<optimized out>} instead.
11869 @chapter C Preprocessor Macros
11871 Some languages, such as C and C@t{++}, provide a way to define and invoke
11872 ``preprocessor macros'' which expand into strings of tokens.
11873 @value{GDBN} can evaluate expressions containing macro invocations, show
11874 the result of macro expansion, and show a macro's definition, including
11875 where it was defined.
11877 You may need to compile your program specially to provide @value{GDBN}
11878 with information about preprocessor macros. Most compilers do not
11879 include macros in their debugging information, even when you compile
11880 with the @option{-g} flag. @xref{Compilation}.
11882 A program may define a macro at one point, remove that definition later,
11883 and then provide a different definition after that. Thus, at different
11884 points in the program, a macro may have different definitions, or have
11885 no definition at all. If there is a current stack frame, @value{GDBN}
11886 uses the macros in scope at that frame's source code line. Otherwise,
11887 @value{GDBN} uses the macros in scope at the current listing location;
11890 Whenever @value{GDBN} evaluates an expression, it always expands any
11891 macro invocations present in the expression. @value{GDBN} also provides
11892 the following commands for working with macros explicitly.
11896 @kindex macro expand
11897 @cindex macro expansion, showing the results of preprocessor
11898 @cindex preprocessor macro expansion, showing the results of
11899 @cindex expanding preprocessor macros
11900 @item macro expand @var{expression}
11901 @itemx macro exp @var{expression}
11902 Show the results of expanding all preprocessor macro invocations in
11903 @var{expression}. Since @value{GDBN} simply expands macros, but does
11904 not parse the result, @var{expression} need not be a valid expression;
11905 it can be any string of tokens.
11908 @item macro expand-once @var{expression}
11909 @itemx macro exp1 @var{expression}
11910 @cindex expand macro once
11911 @i{(This command is not yet implemented.)} Show the results of
11912 expanding those preprocessor macro invocations that appear explicitly in
11913 @var{expression}. Macro invocations appearing in that expansion are
11914 left unchanged. This command allows you to see the effect of a
11915 particular macro more clearly, without being confused by further
11916 expansions. Since @value{GDBN} simply expands macros, but does not
11917 parse the result, @var{expression} need not be a valid expression; it
11918 can be any string of tokens.
11921 @cindex macro definition, showing
11922 @cindex definition of a macro, showing
11923 @cindex macros, from debug info
11924 @item info macro [-a|-all] [--] @var{macro}
11925 Show the current definition or all definitions of the named @var{macro},
11926 and describe the source location or compiler command-line where that
11927 definition was established. The optional double dash is to signify the end of
11928 argument processing and the beginning of @var{macro} for non C-like macros where
11929 the macro may begin with a hyphen.
11931 @kindex info macros
11932 @item info macros @var{location}
11933 Show all macro definitions that are in effect at the location specified
11934 by @var{location}, and describe the source location or compiler
11935 command-line where those definitions were established.
11937 @kindex macro define
11938 @cindex user-defined macros
11939 @cindex defining macros interactively
11940 @cindex macros, user-defined
11941 @item macro define @var{macro} @var{replacement-list}
11942 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
11943 Introduce a definition for a preprocessor macro named @var{macro},
11944 invocations of which are replaced by the tokens given in
11945 @var{replacement-list}. The first form of this command defines an
11946 ``object-like'' macro, which takes no arguments; the second form
11947 defines a ``function-like'' macro, which takes the arguments given in
11950 A definition introduced by this command is in scope in every
11951 expression evaluated in @value{GDBN}, until it is removed with the
11952 @code{macro undef} command, described below. The definition overrides
11953 all definitions for @var{macro} present in the program being debugged,
11954 as well as any previous user-supplied definition.
11956 @kindex macro undef
11957 @item macro undef @var{macro}
11958 Remove any user-supplied definition for the macro named @var{macro}.
11959 This command only affects definitions provided with the @code{macro
11960 define} command, described above; it cannot remove definitions present
11961 in the program being debugged.
11965 List all the macros defined using the @code{macro define} command.
11968 @cindex macros, example of debugging with
11969 Here is a transcript showing the above commands in action. First, we
11970 show our source files:
11975 #include "sample.h"
11978 #define ADD(x) (M + x)
11983 printf ("Hello, world!\n");
11985 printf ("We're so creative.\n");
11987 printf ("Goodbye, world!\n");
11994 Now, we compile the program using the @sc{gnu} C compiler,
11995 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
11996 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
11997 and @option{-gdwarf-4}; we recommend always choosing the most recent
11998 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
11999 includes information about preprocessor macros in the debugging
12003 $ gcc -gdwarf-2 -g3 sample.c -o sample
12007 Now, we start @value{GDBN} on our sample program:
12011 GNU gdb 2002-05-06-cvs
12012 Copyright 2002 Free Software Foundation, Inc.
12013 GDB is free software, @dots{}
12017 We can expand macros and examine their definitions, even when the
12018 program is not running. @value{GDBN} uses the current listing position
12019 to decide which macro definitions are in scope:
12022 (@value{GDBP}) list main
12025 5 #define ADD(x) (M + x)
12030 10 printf ("Hello, world!\n");
12032 12 printf ("We're so creative.\n");
12033 (@value{GDBP}) info macro ADD
12034 Defined at /home/jimb/gdb/macros/play/sample.c:5
12035 #define ADD(x) (M + x)
12036 (@value{GDBP}) info macro Q
12037 Defined at /home/jimb/gdb/macros/play/sample.h:1
12038 included at /home/jimb/gdb/macros/play/sample.c:2
12040 (@value{GDBP}) macro expand ADD(1)
12041 expands to: (42 + 1)
12042 (@value{GDBP}) macro expand-once ADD(1)
12043 expands to: once (M + 1)
12047 In the example above, note that @code{macro expand-once} expands only
12048 the macro invocation explicit in the original text --- the invocation of
12049 @code{ADD} --- but does not expand the invocation of the macro @code{M},
12050 which was introduced by @code{ADD}.
12052 Once the program is running, @value{GDBN} uses the macro definitions in
12053 force at the source line of the current stack frame:
12056 (@value{GDBP}) break main
12057 Breakpoint 1 at 0x8048370: file sample.c, line 10.
12059 Starting program: /home/jimb/gdb/macros/play/sample
12061 Breakpoint 1, main () at sample.c:10
12062 10 printf ("Hello, world!\n");
12066 At line 10, the definition of the macro @code{N} at line 9 is in force:
12069 (@value{GDBP}) info macro N
12070 Defined at /home/jimb/gdb/macros/play/sample.c:9
12072 (@value{GDBP}) macro expand N Q M
12073 expands to: 28 < 42
12074 (@value{GDBP}) print N Q M
12079 As we step over directives that remove @code{N}'s definition, and then
12080 give it a new definition, @value{GDBN} finds the definition (or lack
12081 thereof) in force at each point:
12084 (@value{GDBP}) next
12086 12 printf ("We're so creative.\n");
12087 (@value{GDBP}) info macro N
12088 The symbol `N' has no definition as a C/C++ preprocessor macro
12089 at /home/jimb/gdb/macros/play/sample.c:12
12090 (@value{GDBP}) next
12092 14 printf ("Goodbye, world!\n");
12093 (@value{GDBP}) info macro N
12094 Defined at /home/jimb/gdb/macros/play/sample.c:13
12096 (@value{GDBP}) macro expand N Q M
12097 expands to: 1729 < 42
12098 (@value{GDBP}) print N Q M
12103 In addition to source files, macros can be defined on the compilation command
12104 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
12105 such a way, @value{GDBN} displays the location of their definition as line zero
12106 of the source file submitted to the compiler.
12109 (@value{GDBP}) info macro __STDC__
12110 Defined at /home/jimb/gdb/macros/play/sample.c:0
12117 @chapter Tracepoints
12118 @c This chapter is based on the documentation written by Michael
12119 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
12121 @cindex tracepoints
12122 In some applications, it is not feasible for the debugger to interrupt
12123 the program's execution long enough for the developer to learn
12124 anything helpful about its behavior. If the program's correctness
12125 depends on its real-time behavior, delays introduced by a debugger
12126 might cause the program to change its behavior drastically, or perhaps
12127 fail, even when the code itself is correct. It is useful to be able
12128 to observe the program's behavior without interrupting it.
12130 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
12131 specify locations in the program, called @dfn{tracepoints}, and
12132 arbitrary expressions to evaluate when those tracepoints are reached.
12133 Later, using the @code{tfind} command, you can examine the values
12134 those expressions had when the program hit the tracepoints. The
12135 expressions may also denote objects in memory---structures or arrays,
12136 for example---whose values @value{GDBN} should record; while visiting
12137 a particular tracepoint, you may inspect those objects as if they were
12138 in memory at that moment. However, because @value{GDBN} records these
12139 values without interacting with you, it can do so quickly and
12140 unobtrusively, hopefully not disturbing the program's behavior.
12142 The tracepoint facility is currently available only for remote
12143 targets. @xref{Targets}. In addition, your remote target must know
12144 how to collect trace data. This functionality is implemented in the
12145 remote stub; however, none of the stubs distributed with @value{GDBN}
12146 support tracepoints as of this writing. The format of the remote
12147 packets used to implement tracepoints are described in @ref{Tracepoint
12150 It is also possible to get trace data from a file, in a manner reminiscent
12151 of corefiles; you specify the filename, and use @code{tfind} to search
12152 through the file. @xref{Trace Files}, for more details.
12154 This chapter describes the tracepoint commands and features.
12157 * Set Tracepoints::
12158 * Analyze Collected Data::
12159 * Tracepoint Variables::
12163 @node Set Tracepoints
12164 @section Commands to Set Tracepoints
12166 Before running such a @dfn{trace experiment}, an arbitrary number of
12167 tracepoints can be set. A tracepoint is actually a special type of
12168 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
12169 standard breakpoint commands. For instance, as with breakpoints,
12170 tracepoint numbers are successive integers starting from one, and many
12171 of the commands associated with tracepoints take the tracepoint number
12172 as their argument, to identify which tracepoint to work on.
12174 For each tracepoint, you can specify, in advance, some arbitrary set
12175 of data that you want the target to collect in the trace buffer when
12176 it hits that tracepoint. The collected data can include registers,
12177 local variables, or global data. Later, you can use @value{GDBN}
12178 commands to examine the values these data had at the time the
12179 tracepoint was hit.
12181 Tracepoints do not support every breakpoint feature. Ignore counts on
12182 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
12183 commands when they are hit. Tracepoints may not be thread-specific
12186 @cindex fast tracepoints
12187 Some targets may support @dfn{fast tracepoints}, which are inserted in
12188 a different way (such as with a jump instead of a trap), that is
12189 faster but possibly restricted in where they may be installed.
12191 @cindex static tracepoints
12192 @cindex markers, static tracepoints
12193 @cindex probing markers, static tracepoints
12194 Regular and fast tracepoints are dynamic tracing facilities, meaning
12195 that they can be used to insert tracepoints at (almost) any location
12196 in the target. Some targets may also support controlling @dfn{static
12197 tracepoints} from @value{GDBN}. With static tracing, a set of
12198 instrumentation points, also known as @dfn{markers}, are embedded in
12199 the target program, and can be activated or deactivated by name or
12200 address. These are usually placed at locations which facilitate
12201 investigating what the target is actually doing. @value{GDBN}'s
12202 support for static tracing includes being able to list instrumentation
12203 points, and attach them with @value{GDBN} defined high level
12204 tracepoints that expose the whole range of convenience of
12205 @value{GDBN}'s tracepoints support. Namely, support for collecting
12206 registers values and values of global or local (to the instrumentation
12207 point) variables; tracepoint conditions and trace state variables.
12208 The act of installing a @value{GDBN} static tracepoint on an
12209 instrumentation point, or marker, is referred to as @dfn{probing} a
12210 static tracepoint marker.
12212 @code{gdbserver} supports tracepoints on some target systems.
12213 @xref{Server,,Tracepoints support in @code{gdbserver}}.
12215 This section describes commands to set tracepoints and associated
12216 conditions and actions.
12219 * Create and Delete Tracepoints::
12220 * Enable and Disable Tracepoints::
12221 * Tracepoint Passcounts::
12222 * Tracepoint Conditions::
12223 * Trace State Variables::
12224 * Tracepoint Actions::
12225 * Listing Tracepoints::
12226 * Listing Static Tracepoint Markers::
12227 * Starting and Stopping Trace Experiments::
12228 * Tracepoint Restrictions::
12231 @node Create and Delete Tracepoints
12232 @subsection Create and Delete Tracepoints
12235 @cindex set tracepoint
12237 @item trace @var{location}
12238 The @code{trace} command is very similar to the @code{break} command.
12239 Its argument @var{location} can be any valid location.
12240 @xref{Specify Location}. The @code{trace} command defines a tracepoint,
12241 which is a point in the target program where the debugger will briefly stop,
12242 collect some data, and then allow the program to continue. Setting a tracepoint
12243 or changing its actions takes effect immediately if the remote stub
12244 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
12246 If remote stub doesn't support the @samp{InstallInTrace} feature, all
12247 these changes don't take effect until the next @code{tstart}
12248 command, and once a trace experiment is running, further changes will
12249 not have any effect until the next trace experiment starts. In addition,
12250 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
12251 address is not yet resolved. (This is similar to pending breakpoints.)
12252 Pending tracepoints are not downloaded to the target and not installed
12253 until they are resolved. The resolution of pending tracepoints requires
12254 @value{GDBN} support---when debugging with the remote target, and
12255 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
12256 tracing}), pending tracepoints can not be resolved (and downloaded to
12257 the remote stub) while @value{GDBN} is disconnected.
12259 Here are some examples of using the @code{trace} command:
12262 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
12264 (@value{GDBP}) @b{trace +2} // 2 lines forward
12266 (@value{GDBP}) @b{trace my_function} // first source line of function
12268 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
12270 (@value{GDBP}) @b{trace *0x2117c4} // an address
12274 You can abbreviate @code{trace} as @code{tr}.
12276 @item trace @var{location} if @var{cond}
12277 Set a tracepoint with condition @var{cond}; evaluate the expression
12278 @var{cond} each time the tracepoint is reached, and collect data only
12279 if the value is nonzero---that is, if @var{cond} evaluates as true.
12280 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
12281 information on tracepoint conditions.
12283 @item ftrace @var{location} [ if @var{cond} ]
12284 @cindex set fast tracepoint
12285 @cindex fast tracepoints, setting
12287 The @code{ftrace} command sets a fast tracepoint. For targets that
12288 support them, fast tracepoints will use a more efficient but possibly
12289 less general technique to trigger data collection, such as a jump
12290 instruction instead of a trap, or some sort of hardware support. It
12291 may not be possible to create a fast tracepoint at the desired
12292 location, in which case the command will exit with an explanatory
12295 @value{GDBN} handles arguments to @code{ftrace} exactly as for
12298 On 32-bit x86-architecture systems, fast tracepoints normally need to
12299 be placed at an instruction that is 5 bytes or longer, but can be
12300 placed at 4-byte instructions if the low 64K of memory of the target
12301 program is available to install trampolines. Some Unix-type systems,
12302 such as @sc{gnu}/Linux, exclude low addresses from the program's
12303 address space; but for instance with the Linux kernel it is possible
12304 to let @value{GDBN} use this area by doing a @command{sysctl} command
12305 to set the @code{mmap_min_addr} kernel parameter, as in
12308 sudo sysctl -w vm.mmap_min_addr=32768
12312 which sets the low address to 32K, which leaves plenty of room for
12313 trampolines. The minimum address should be set to a page boundary.
12315 @item strace @var{location} [ if @var{cond} ]
12316 @cindex set static tracepoint
12317 @cindex static tracepoints, setting
12318 @cindex probe static tracepoint marker
12320 The @code{strace} command sets a static tracepoint. For targets that
12321 support it, setting a static tracepoint probes a static
12322 instrumentation point, or marker, found at @var{location}. It may not
12323 be possible to set a static tracepoint at the desired location, in
12324 which case the command will exit with an explanatory message.
12326 @value{GDBN} handles arguments to @code{strace} exactly as for
12327 @code{trace}, with the addition that the user can also specify
12328 @code{-m @var{marker}} as @var{location}. This probes the marker
12329 identified by the @var{marker} string identifier. This identifier
12330 depends on the static tracepoint backend library your program is
12331 using. You can find all the marker identifiers in the @samp{ID} field
12332 of the @code{info static-tracepoint-markers} command output.
12333 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
12334 Markers}. For example, in the following small program using the UST
12340 trace_mark(ust, bar33, "str %s", "FOOBAZ");
12345 the marker id is composed of joining the first two arguments to the
12346 @code{trace_mark} call with a slash, which translates to:
12349 (@value{GDBP}) info static-tracepoint-markers
12350 Cnt Enb ID Address What
12351 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
12357 so you may probe the marker above with:
12360 (@value{GDBP}) strace -m ust/bar33
12363 Static tracepoints accept an extra collect action --- @code{collect
12364 $_sdata}. This collects arbitrary user data passed in the probe point
12365 call to the tracing library. In the UST example above, you'll see
12366 that the third argument to @code{trace_mark} is a printf-like format
12367 string. The user data is then the result of running that formating
12368 string against the following arguments. Note that @code{info
12369 static-tracepoint-markers} command output lists that format string in
12370 the @samp{Data:} field.
12372 You can inspect this data when analyzing the trace buffer, by printing
12373 the $_sdata variable like any other variable available to
12374 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
12377 @cindex last tracepoint number
12378 @cindex recent tracepoint number
12379 @cindex tracepoint number
12380 The convenience variable @code{$tpnum} records the tracepoint number
12381 of the most recently set tracepoint.
12383 @kindex delete tracepoint
12384 @cindex tracepoint deletion
12385 @item delete tracepoint @r{[}@var{num}@r{]}
12386 Permanently delete one or more tracepoints. With no argument, the
12387 default is to delete all tracepoints. Note that the regular
12388 @code{delete} command can remove tracepoints also.
12393 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
12395 (@value{GDBP}) @b{delete trace} // remove all tracepoints
12399 You can abbreviate this command as @code{del tr}.
12402 @node Enable and Disable Tracepoints
12403 @subsection Enable and Disable Tracepoints
12405 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
12408 @kindex disable tracepoint
12409 @item disable tracepoint @r{[}@var{num}@r{]}
12410 Disable tracepoint @var{num}, or all tracepoints if no argument
12411 @var{num} is given. A disabled tracepoint will have no effect during
12412 a trace experiment, but it is not forgotten. You can re-enable
12413 a disabled tracepoint using the @code{enable tracepoint} command.
12414 If the command is issued during a trace experiment and the debug target
12415 has support for disabling tracepoints during a trace experiment, then the
12416 change will be effective immediately. Otherwise, it will be applied to the
12417 next trace experiment.
12419 @kindex enable tracepoint
12420 @item enable tracepoint @r{[}@var{num}@r{]}
12421 Enable tracepoint @var{num}, or all tracepoints. If this command is
12422 issued during a trace experiment and the debug target supports enabling
12423 tracepoints during a trace experiment, then the enabled tracepoints will
12424 become effective immediately. Otherwise, they will become effective the
12425 next time a trace experiment is run.
12428 @node Tracepoint Passcounts
12429 @subsection Tracepoint Passcounts
12433 @cindex tracepoint pass count
12434 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
12435 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
12436 automatically stop a trace experiment. If a tracepoint's passcount is
12437 @var{n}, then the trace experiment will be automatically stopped on
12438 the @var{n}'th time that tracepoint is hit. If the tracepoint number
12439 @var{num} is not specified, the @code{passcount} command sets the
12440 passcount of the most recently defined tracepoint. If no passcount is
12441 given, the trace experiment will run until stopped explicitly by the
12447 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
12448 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
12450 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
12451 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
12452 (@value{GDBP}) @b{trace foo}
12453 (@value{GDBP}) @b{pass 3}
12454 (@value{GDBP}) @b{trace bar}
12455 (@value{GDBP}) @b{pass 2}
12456 (@value{GDBP}) @b{trace baz}
12457 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
12458 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
12459 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
12460 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
12464 @node Tracepoint Conditions
12465 @subsection Tracepoint Conditions
12466 @cindex conditional tracepoints
12467 @cindex tracepoint conditions
12469 The simplest sort of tracepoint collects data every time your program
12470 reaches a specified place. You can also specify a @dfn{condition} for
12471 a tracepoint. A condition is just a Boolean expression in your
12472 programming language (@pxref{Expressions, ,Expressions}). A
12473 tracepoint with a condition evaluates the expression each time your
12474 program reaches it, and data collection happens only if the condition
12477 Tracepoint conditions can be specified when a tracepoint is set, by
12478 using @samp{if} in the arguments to the @code{trace} command.
12479 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
12480 also be set or changed at any time with the @code{condition} command,
12481 just as with breakpoints.
12483 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
12484 the conditional expression itself. Instead, @value{GDBN} encodes the
12485 expression into an agent expression (@pxref{Agent Expressions})
12486 suitable for execution on the target, independently of @value{GDBN}.
12487 Global variables become raw memory locations, locals become stack
12488 accesses, and so forth.
12490 For instance, suppose you have a function that is usually called
12491 frequently, but should not be called after an error has occurred. You
12492 could use the following tracepoint command to collect data about calls
12493 of that function that happen while the error code is propagating
12494 through the program; an unconditional tracepoint could end up
12495 collecting thousands of useless trace frames that you would have to
12499 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
12502 @node Trace State Variables
12503 @subsection Trace State Variables
12504 @cindex trace state variables
12506 A @dfn{trace state variable} is a special type of variable that is
12507 created and managed by target-side code. The syntax is the same as
12508 that for GDB's convenience variables (a string prefixed with ``$''),
12509 but they are stored on the target. They must be created explicitly,
12510 using a @code{tvariable} command. They are always 64-bit signed
12513 Trace state variables are remembered by @value{GDBN}, and downloaded
12514 to the target along with tracepoint information when the trace
12515 experiment starts. There are no intrinsic limits on the number of
12516 trace state variables, beyond memory limitations of the target.
12518 @cindex convenience variables, and trace state variables
12519 Although trace state variables are managed by the target, you can use
12520 them in print commands and expressions as if they were convenience
12521 variables; @value{GDBN} will get the current value from the target
12522 while the trace experiment is running. Trace state variables share
12523 the same namespace as other ``$'' variables, which means that you
12524 cannot have trace state variables with names like @code{$23} or
12525 @code{$pc}, nor can you have a trace state variable and a convenience
12526 variable with the same name.
12530 @item tvariable $@var{name} [ = @var{expression} ]
12532 The @code{tvariable} command creates a new trace state variable named
12533 @code{$@var{name}}, and optionally gives it an initial value of
12534 @var{expression}. The @var{expression} is evaluated when this command is
12535 entered; the result will be converted to an integer if possible,
12536 otherwise @value{GDBN} will report an error. A subsequent
12537 @code{tvariable} command specifying the same name does not create a
12538 variable, but instead assigns the supplied initial value to the
12539 existing variable of that name, overwriting any previous initial
12540 value. The default initial value is 0.
12542 @item info tvariables
12543 @kindex info tvariables
12544 List all the trace state variables along with their initial values.
12545 Their current values may also be displayed, if the trace experiment is
12548 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
12549 @kindex delete tvariable
12550 Delete the given trace state variables, or all of them if no arguments
12555 @node Tracepoint Actions
12556 @subsection Tracepoint Action Lists
12560 @cindex tracepoint actions
12561 @item actions @r{[}@var{num}@r{]}
12562 This command will prompt for a list of actions to be taken when the
12563 tracepoint is hit. If the tracepoint number @var{num} is not
12564 specified, this command sets the actions for the one that was most
12565 recently defined (so that you can define a tracepoint and then say
12566 @code{actions} without bothering about its number). You specify the
12567 actions themselves on the following lines, one action at a time, and
12568 terminate the actions list with a line containing just @code{end}. So
12569 far, the only defined actions are @code{collect}, @code{teval}, and
12570 @code{while-stepping}.
12572 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
12573 Commands, ,Breakpoint Command Lists}), except that only the defined
12574 actions are allowed; any other @value{GDBN} command is rejected.
12576 @cindex remove actions from a tracepoint
12577 To remove all actions from a tracepoint, type @samp{actions @var{num}}
12578 and follow it immediately with @samp{end}.
12581 (@value{GDBP}) @b{collect @var{data}} // collect some data
12583 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
12585 (@value{GDBP}) @b{end} // signals the end of actions.
12588 In the following example, the action list begins with @code{collect}
12589 commands indicating the things to be collected when the tracepoint is
12590 hit. Then, in order to single-step and collect additional data
12591 following the tracepoint, a @code{while-stepping} command is used,
12592 followed by the list of things to be collected after each step in a
12593 sequence of single steps. The @code{while-stepping} command is
12594 terminated by its own separate @code{end} command. Lastly, the action
12595 list is terminated by an @code{end} command.
12598 (@value{GDBP}) @b{trace foo}
12599 (@value{GDBP}) @b{actions}
12600 Enter actions for tracepoint 1, one per line:
12603 > while-stepping 12
12604 > collect $pc, arr[i]
12609 @kindex collect @r{(tracepoints)}
12610 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
12611 Collect values of the given expressions when the tracepoint is hit.
12612 This command accepts a comma-separated list of any valid expressions.
12613 In addition to global, static, or local variables, the following
12614 special arguments are supported:
12618 Collect all registers.
12621 Collect all function arguments.
12624 Collect all local variables.
12627 Collect the return address. This is helpful if you want to see more
12631 Collects the number of arguments from the static probe at which the
12632 tracepoint is located.
12633 @xref{Static Probe Points}.
12635 @item $_probe_arg@var{n}
12636 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
12637 from the static probe at which the tracepoint is located.
12638 @xref{Static Probe Points}.
12641 @vindex $_sdata@r{, collect}
12642 Collect static tracepoint marker specific data. Only available for
12643 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
12644 Lists}. On the UST static tracepoints library backend, an
12645 instrumentation point resembles a @code{printf} function call. The
12646 tracing library is able to collect user specified data formatted to a
12647 character string using the format provided by the programmer that
12648 instrumented the program. Other backends have similar mechanisms.
12649 Here's an example of a UST marker call:
12652 const char master_name[] = "$your_name";
12653 trace_mark(channel1, marker1, "hello %s", master_name)
12656 In this case, collecting @code{$_sdata} collects the string
12657 @samp{hello $yourname}. When analyzing the trace buffer, you can
12658 inspect @samp{$_sdata} like any other variable available to
12662 You can give several consecutive @code{collect} commands, each one
12663 with a single argument, or one @code{collect} command with several
12664 arguments separated by commas; the effect is the same.
12666 The optional @var{mods} changes the usual handling of the arguments.
12667 @code{s} requests that pointers to chars be handled as strings, in
12668 particular collecting the contents of the memory being pointed at, up
12669 to the first zero. The upper bound is by default the value of the
12670 @code{print elements} variable; if @code{s} is followed by a decimal
12671 number, that is the upper bound instead. So for instance
12672 @samp{collect/s25 mystr} collects as many as 25 characters at
12675 The command @code{info scope} (@pxref{Symbols, info scope}) is
12676 particularly useful for figuring out what data to collect.
12678 @kindex teval @r{(tracepoints)}
12679 @item teval @var{expr1}, @var{expr2}, @dots{}
12680 Evaluate the given expressions when the tracepoint is hit. This
12681 command accepts a comma-separated list of expressions. The results
12682 are discarded, so this is mainly useful for assigning values to trace
12683 state variables (@pxref{Trace State Variables}) without adding those
12684 values to the trace buffer, as would be the case if the @code{collect}
12687 @kindex while-stepping @r{(tracepoints)}
12688 @item while-stepping @var{n}
12689 Perform @var{n} single-step instruction traces after the tracepoint,
12690 collecting new data after each step. The @code{while-stepping}
12691 command is followed by the list of what to collect while stepping
12692 (followed by its own @code{end} command):
12695 > while-stepping 12
12696 > collect $regs, myglobal
12702 Note that @code{$pc} is not automatically collected by
12703 @code{while-stepping}; you need to explicitly collect that register if
12704 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
12707 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
12708 @kindex set default-collect
12709 @cindex default collection action
12710 This variable is a list of expressions to collect at each tracepoint
12711 hit. It is effectively an additional @code{collect} action prepended
12712 to every tracepoint action list. The expressions are parsed
12713 individually for each tracepoint, so for instance a variable named
12714 @code{xyz} may be interpreted as a global for one tracepoint, and a
12715 local for another, as appropriate to the tracepoint's location.
12717 @item show default-collect
12718 @kindex show default-collect
12719 Show the list of expressions that are collected by default at each
12724 @node Listing Tracepoints
12725 @subsection Listing Tracepoints
12728 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
12729 @kindex info tp @r{[}@var{n}@dots{}@r{]}
12730 @cindex information about tracepoints
12731 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
12732 Display information about the tracepoint @var{num}. If you don't
12733 specify a tracepoint number, displays information about all the
12734 tracepoints defined so far. The format is similar to that used for
12735 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
12736 command, simply restricting itself to tracepoints.
12738 A tracepoint's listing may include additional information specific to
12743 its passcount as given by the @code{passcount @var{n}} command
12746 the state about installed on target of each location
12750 (@value{GDBP}) @b{info trace}
12751 Num Type Disp Enb Address What
12752 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
12754 collect globfoo, $regs
12759 2 tracepoint keep y <MULTIPLE>
12761 2.1 y 0x0804859c in func4 at change-loc.h:35
12762 installed on target
12763 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
12764 installed on target
12765 2.3 y <PENDING> set_tracepoint
12766 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
12767 not installed on target
12772 This command can be abbreviated @code{info tp}.
12775 @node Listing Static Tracepoint Markers
12776 @subsection Listing Static Tracepoint Markers
12779 @kindex info static-tracepoint-markers
12780 @cindex information about static tracepoint markers
12781 @item info static-tracepoint-markers
12782 Display information about all static tracepoint markers defined in the
12785 For each marker, the following columns are printed:
12789 An incrementing counter, output to help readability. This is not a
12792 The marker ID, as reported by the target.
12793 @item Enabled or Disabled
12794 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
12795 that are not enabled.
12797 Where the marker is in your program, as a memory address.
12799 Where the marker is in the source for your program, as a file and line
12800 number. If the debug information included in the program does not
12801 allow @value{GDBN} to locate the source of the marker, this column
12802 will be left blank.
12806 In addition, the following information may be printed for each marker:
12810 User data passed to the tracing library by the marker call. In the
12811 UST backend, this is the format string passed as argument to the
12813 @item Static tracepoints probing the marker
12814 The list of static tracepoints attached to the marker.
12818 (@value{GDBP}) info static-tracepoint-markers
12819 Cnt ID Enb Address What
12820 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
12821 Data: number1 %d number2 %d
12822 Probed by static tracepoints: #2
12823 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
12829 @node Starting and Stopping Trace Experiments
12830 @subsection Starting and Stopping Trace Experiments
12833 @kindex tstart [ @var{notes} ]
12834 @cindex start a new trace experiment
12835 @cindex collected data discarded
12837 This command starts the trace experiment, and begins collecting data.
12838 It has the side effect of discarding all the data collected in the
12839 trace buffer during the previous trace experiment. If any arguments
12840 are supplied, they are taken as a note and stored with the trace
12841 experiment's state. The notes may be arbitrary text, and are
12842 especially useful with disconnected tracing in a multi-user context;
12843 the notes can explain what the trace is doing, supply user contact
12844 information, and so forth.
12846 @kindex tstop [ @var{notes} ]
12847 @cindex stop a running trace experiment
12849 This command stops the trace experiment. If any arguments are
12850 supplied, they are recorded with the experiment as a note. This is
12851 useful if you are stopping a trace started by someone else, for
12852 instance if the trace is interfering with the system's behavior and
12853 needs to be stopped quickly.
12855 @strong{Note}: a trace experiment and data collection may stop
12856 automatically if any tracepoint's passcount is reached
12857 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
12860 @cindex status of trace data collection
12861 @cindex trace experiment, status of
12863 This command displays the status of the current trace data
12867 Here is an example of the commands we described so far:
12870 (@value{GDBP}) @b{trace gdb_c_test}
12871 (@value{GDBP}) @b{actions}
12872 Enter actions for tracepoint #1, one per line.
12873 > collect $regs,$locals,$args
12874 > while-stepping 11
12878 (@value{GDBP}) @b{tstart}
12879 [time passes @dots{}]
12880 (@value{GDBP}) @b{tstop}
12883 @anchor{disconnected tracing}
12884 @cindex disconnected tracing
12885 You can choose to continue running the trace experiment even if
12886 @value{GDBN} disconnects from the target, voluntarily or
12887 involuntarily. For commands such as @code{detach}, the debugger will
12888 ask what you want to do with the trace. But for unexpected
12889 terminations (@value{GDBN} crash, network outage), it would be
12890 unfortunate to lose hard-won trace data, so the variable
12891 @code{disconnected-tracing} lets you decide whether the trace should
12892 continue running without @value{GDBN}.
12895 @item set disconnected-tracing on
12896 @itemx set disconnected-tracing off
12897 @kindex set disconnected-tracing
12898 Choose whether a tracing run should continue to run if @value{GDBN}
12899 has disconnected from the target. Note that @code{detach} or
12900 @code{quit} will ask you directly what to do about a running trace no
12901 matter what this variable's setting, so the variable is mainly useful
12902 for handling unexpected situations, such as loss of the network.
12904 @item show disconnected-tracing
12905 @kindex show disconnected-tracing
12906 Show the current choice for disconnected tracing.
12910 When you reconnect to the target, the trace experiment may or may not
12911 still be running; it might have filled the trace buffer in the
12912 meantime, or stopped for one of the other reasons. If it is running,
12913 it will continue after reconnection.
12915 Upon reconnection, the target will upload information about the
12916 tracepoints in effect. @value{GDBN} will then compare that
12917 information to the set of tracepoints currently defined, and attempt
12918 to match them up, allowing for the possibility that the numbers may
12919 have changed due to creation and deletion in the meantime. If one of
12920 the target's tracepoints does not match any in @value{GDBN}, the
12921 debugger will create a new tracepoint, so that you have a number with
12922 which to specify that tracepoint. This matching-up process is
12923 necessarily heuristic, and it may result in useless tracepoints being
12924 created; you may simply delete them if they are of no use.
12926 @cindex circular trace buffer
12927 If your target agent supports a @dfn{circular trace buffer}, then you
12928 can run a trace experiment indefinitely without filling the trace
12929 buffer; when space runs out, the agent deletes already-collected trace
12930 frames, oldest first, until there is enough room to continue
12931 collecting. This is especially useful if your tracepoints are being
12932 hit too often, and your trace gets terminated prematurely because the
12933 buffer is full. To ask for a circular trace buffer, simply set
12934 @samp{circular-trace-buffer} to on. You can set this at any time,
12935 including during tracing; if the agent can do it, it will change
12936 buffer handling on the fly, otherwise it will not take effect until
12940 @item set circular-trace-buffer on
12941 @itemx set circular-trace-buffer off
12942 @kindex set circular-trace-buffer
12943 Choose whether a tracing run should use a linear or circular buffer
12944 for trace data. A linear buffer will not lose any trace data, but may
12945 fill up prematurely, while a circular buffer will discard old trace
12946 data, but it will have always room for the latest tracepoint hits.
12948 @item show circular-trace-buffer
12949 @kindex show circular-trace-buffer
12950 Show the current choice for the trace buffer. Note that this may not
12951 match the agent's current buffer handling, nor is it guaranteed to
12952 match the setting that might have been in effect during a past run,
12953 for instance if you are looking at frames from a trace file.
12958 @item set trace-buffer-size @var{n}
12959 @itemx set trace-buffer-size unlimited
12960 @kindex set trace-buffer-size
12961 Request that the target use a trace buffer of @var{n} bytes. Not all
12962 targets will honor the request; they may have a compiled-in size for
12963 the trace buffer, or some other limitation. Set to a value of
12964 @code{unlimited} or @code{-1} to let the target use whatever size it
12965 likes. This is also the default.
12967 @item show trace-buffer-size
12968 @kindex show trace-buffer-size
12969 Show the current requested size for the trace buffer. Note that this
12970 will only match the actual size if the target supports size-setting,
12971 and was able to handle the requested size. For instance, if the
12972 target can only change buffer size between runs, this variable will
12973 not reflect the change until the next run starts. Use @code{tstatus}
12974 to get a report of the actual buffer size.
12978 @item set trace-user @var{text}
12979 @kindex set trace-user
12981 @item show trace-user
12982 @kindex show trace-user
12984 @item set trace-notes @var{text}
12985 @kindex set trace-notes
12986 Set the trace run's notes.
12988 @item show trace-notes
12989 @kindex show trace-notes
12990 Show the trace run's notes.
12992 @item set trace-stop-notes @var{text}
12993 @kindex set trace-stop-notes
12994 Set the trace run's stop notes. The handling of the note is as for
12995 @code{tstop} arguments; the set command is convenient way to fix a
12996 stop note that is mistaken or incomplete.
12998 @item show trace-stop-notes
12999 @kindex show trace-stop-notes
13000 Show the trace run's stop notes.
13004 @node Tracepoint Restrictions
13005 @subsection Tracepoint Restrictions
13007 @cindex tracepoint restrictions
13008 There are a number of restrictions on the use of tracepoints. As
13009 described above, tracepoint data gathering occurs on the target
13010 without interaction from @value{GDBN}. Thus the full capabilities of
13011 the debugger are not available during data gathering, and then at data
13012 examination time, you will be limited by only having what was
13013 collected. The following items describe some common problems, but it
13014 is not exhaustive, and you may run into additional difficulties not
13020 Tracepoint expressions are intended to gather objects (lvalues). Thus
13021 the full flexibility of GDB's expression evaluator is not available.
13022 You cannot call functions, cast objects to aggregate types, access
13023 convenience variables or modify values (except by assignment to trace
13024 state variables). Some language features may implicitly call
13025 functions (for instance Objective-C fields with accessors), and therefore
13026 cannot be collected either.
13029 Collection of local variables, either individually or in bulk with
13030 @code{$locals} or @code{$args}, during @code{while-stepping} may
13031 behave erratically. The stepping action may enter a new scope (for
13032 instance by stepping into a function), or the location of the variable
13033 may change (for instance it is loaded into a register). The
13034 tracepoint data recorded uses the location information for the
13035 variables that is correct for the tracepoint location. When the
13036 tracepoint is created, it is not possible, in general, to determine
13037 where the steps of a @code{while-stepping} sequence will advance the
13038 program---particularly if a conditional branch is stepped.
13041 Collection of an incompletely-initialized or partially-destroyed object
13042 may result in something that @value{GDBN} cannot display, or displays
13043 in a misleading way.
13046 When @value{GDBN} displays a pointer to character it automatically
13047 dereferences the pointer to also display characters of the string
13048 being pointed to. However, collecting the pointer during tracing does
13049 not automatically collect the string. You need to explicitly
13050 dereference the pointer and provide size information if you want to
13051 collect not only the pointer, but the memory pointed to. For example,
13052 @code{*ptr@@50} can be used to collect the 50 element array pointed to
13056 It is not possible to collect a complete stack backtrace at a
13057 tracepoint. Instead, you may collect the registers and a few hundred
13058 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
13059 (adjust to use the name of the actual stack pointer register on your
13060 target architecture, and the amount of stack you wish to capture).
13061 Then the @code{backtrace} command will show a partial backtrace when
13062 using a trace frame. The number of stack frames that can be examined
13063 depends on the sizes of the frames in the collected stack. Note that
13064 if you ask for a block so large that it goes past the bottom of the
13065 stack, the target agent may report an error trying to read from an
13069 If you do not collect registers at a tracepoint, @value{GDBN} can
13070 infer that the value of @code{$pc} must be the same as the address of
13071 the tracepoint and use that when you are looking at a trace frame
13072 for that tracepoint. However, this cannot work if the tracepoint has
13073 multiple locations (for instance if it was set in a function that was
13074 inlined), or if it has a @code{while-stepping} loop. In those cases
13075 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
13080 @node Analyze Collected Data
13081 @section Using the Collected Data
13083 After the tracepoint experiment ends, you use @value{GDBN} commands
13084 for examining the trace data. The basic idea is that each tracepoint
13085 collects a trace @dfn{snapshot} every time it is hit and another
13086 snapshot every time it single-steps. All these snapshots are
13087 consecutively numbered from zero and go into a buffer, and you can
13088 examine them later. The way you examine them is to @dfn{focus} on a
13089 specific trace snapshot. When the remote stub is focused on a trace
13090 snapshot, it will respond to all @value{GDBN} requests for memory and
13091 registers by reading from the buffer which belongs to that snapshot,
13092 rather than from @emph{real} memory or registers of the program being
13093 debugged. This means that @strong{all} @value{GDBN} commands
13094 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
13095 behave as if we were currently debugging the program state as it was
13096 when the tracepoint occurred. Any requests for data that are not in
13097 the buffer will fail.
13100 * tfind:: How to select a trace snapshot
13101 * tdump:: How to display all data for a snapshot
13102 * save tracepoints:: How to save tracepoints for a future run
13106 @subsection @code{tfind @var{n}}
13109 @cindex select trace snapshot
13110 @cindex find trace snapshot
13111 The basic command for selecting a trace snapshot from the buffer is
13112 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
13113 counting from zero. If no argument @var{n} is given, the next
13114 snapshot is selected.
13116 Here are the various forms of using the @code{tfind} command.
13120 Find the first snapshot in the buffer. This is a synonym for
13121 @code{tfind 0} (since 0 is the number of the first snapshot).
13124 Stop debugging trace snapshots, resume @emph{live} debugging.
13127 Same as @samp{tfind none}.
13130 No argument means find the next trace snapshot.
13133 Find the previous trace snapshot before the current one. This permits
13134 retracing earlier steps.
13136 @item tfind tracepoint @var{num}
13137 Find the next snapshot associated with tracepoint @var{num}. Search
13138 proceeds forward from the last examined trace snapshot. If no
13139 argument @var{num} is given, it means find the next snapshot collected
13140 for the same tracepoint as the current snapshot.
13142 @item tfind pc @var{addr}
13143 Find the next snapshot associated with the value @var{addr} of the
13144 program counter. Search proceeds forward from the last examined trace
13145 snapshot. If no argument @var{addr} is given, it means find the next
13146 snapshot with the same value of PC as the current snapshot.
13148 @item tfind outside @var{addr1}, @var{addr2}
13149 Find the next snapshot whose PC is outside the given range of
13150 addresses (exclusive).
13152 @item tfind range @var{addr1}, @var{addr2}
13153 Find the next snapshot whose PC is between @var{addr1} and
13154 @var{addr2} (inclusive).
13156 @item tfind line @r{[}@var{file}:@r{]}@var{n}
13157 Find the next snapshot associated with the source line @var{n}. If
13158 the optional argument @var{file} is given, refer to line @var{n} in
13159 that source file. Search proceeds forward from the last examined
13160 trace snapshot. If no argument @var{n} is given, it means find the
13161 next line other than the one currently being examined; thus saying
13162 @code{tfind line} repeatedly can appear to have the same effect as
13163 stepping from line to line in a @emph{live} debugging session.
13166 The default arguments for the @code{tfind} commands are specifically
13167 designed to make it easy to scan through the trace buffer. For
13168 instance, @code{tfind} with no argument selects the next trace
13169 snapshot, and @code{tfind -} with no argument selects the previous
13170 trace snapshot. So, by giving one @code{tfind} command, and then
13171 simply hitting @key{RET} repeatedly you can examine all the trace
13172 snapshots in order. Or, by saying @code{tfind -} and then hitting
13173 @key{RET} repeatedly you can examine the snapshots in reverse order.
13174 The @code{tfind line} command with no argument selects the snapshot
13175 for the next source line executed. The @code{tfind pc} command with
13176 no argument selects the next snapshot with the same program counter
13177 (PC) as the current frame. The @code{tfind tracepoint} command with
13178 no argument selects the next trace snapshot collected by the same
13179 tracepoint as the current one.
13181 In addition to letting you scan through the trace buffer manually,
13182 these commands make it easy to construct @value{GDBN} scripts that
13183 scan through the trace buffer and print out whatever collected data
13184 you are interested in. Thus, if we want to examine the PC, FP, and SP
13185 registers from each trace frame in the buffer, we can say this:
13188 (@value{GDBP}) @b{tfind start}
13189 (@value{GDBP}) @b{while ($trace_frame != -1)}
13190 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
13191 $trace_frame, $pc, $sp, $fp
13195 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
13196 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
13197 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
13198 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
13199 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
13200 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
13201 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
13202 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
13203 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
13204 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
13205 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
13208 Or, if we want to examine the variable @code{X} at each source line in
13212 (@value{GDBP}) @b{tfind start}
13213 (@value{GDBP}) @b{while ($trace_frame != -1)}
13214 > printf "Frame %d, X == %d\n", $trace_frame, X
13224 @subsection @code{tdump}
13226 @cindex dump all data collected at tracepoint
13227 @cindex tracepoint data, display
13229 This command takes no arguments. It prints all the data collected at
13230 the current trace snapshot.
13233 (@value{GDBP}) @b{trace 444}
13234 (@value{GDBP}) @b{actions}
13235 Enter actions for tracepoint #2, one per line:
13236 > collect $regs, $locals, $args, gdb_long_test
13239 (@value{GDBP}) @b{tstart}
13241 (@value{GDBP}) @b{tfind line 444}
13242 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
13244 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
13246 (@value{GDBP}) @b{tdump}
13247 Data collected at tracepoint 2, trace frame 1:
13248 d0 0xc4aa0085 -995491707
13252 d4 0x71aea3d 119204413
13255 d7 0x380035 3670069
13256 a0 0x19e24a 1696330
13257 a1 0x3000668 50333288
13259 a3 0x322000 3284992
13260 a4 0x3000698 50333336
13261 a5 0x1ad3cc 1758156
13262 fp 0x30bf3c 0x30bf3c
13263 sp 0x30bf34 0x30bf34
13265 pc 0x20b2c8 0x20b2c8
13269 p = 0x20e5b4 "gdb-test"
13276 gdb_long_test = 17 '\021'
13281 @code{tdump} works by scanning the tracepoint's current collection
13282 actions and printing the value of each expression listed. So
13283 @code{tdump} can fail, if after a run, you change the tracepoint's
13284 actions to mention variables that were not collected during the run.
13286 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
13287 uses the collected value of @code{$pc} to distinguish between trace
13288 frames that were collected at the tracepoint hit, and frames that were
13289 collected while stepping. This allows it to correctly choose whether
13290 to display the basic list of collections, or the collections from the
13291 body of the while-stepping loop. However, if @code{$pc} was not collected,
13292 then @code{tdump} will always attempt to dump using the basic collection
13293 list, and may fail if a while-stepping frame does not include all the
13294 same data that is collected at the tracepoint hit.
13295 @c This is getting pretty arcane, example would be good.
13297 @node save tracepoints
13298 @subsection @code{save tracepoints @var{filename}}
13299 @kindex save tracepoints
13300 @kindex save-tracepoints
13301 @cindex save tracepoints for future sessions
13303 This command saves all current tracepoint definitions together with
13304 their actions and passcounts, into a file @file{@var{filename}}
13305 suitable for use in a later debugging session. To read the saved
13306 tracepoint definitions, use the @code{source} command (@pxref{Command
13307 Files}). The @w{@code{save-tracepoints}} command is a deprecated
13308 alias for @w{@code{save tracepoints}}
13310 @node Tracepoint Variables
13311 @section Convenience Variables for Tracepoints
13312 @cindex tracepoint variables
13313 @cindex convenience variables for tracepoints
13316 @vindex $trace_frame
13317 @item (int) $trace_frame
13318 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
13319 snapshot is selected.
13321 @vindex $tracepoint
13322 @item (int) $tracepoint
13323 The tracepoint for the current trace snapshot.
13325 @vindex $trace_line
13326 @item (int) $trace_line
13327 The line number for the current trace snapshot.
13329 @vindex $trace_file
13330 @item (char []) $trace_file
13331 The source file for the current trace snapshot.
13333 @vindex $trace_func
13334 @item (char []) $trace_func
13335 The name of the function containing @code{$tracepoint}.
13338 Note: @code{$trace_file} is not suitable for use in @code{printf},
13339 use @code{output} instead.
13341 Here's a simple example of using these convenience variables for
13342 stepping through all the trace snapshots and printing some of their
13343 data. Note that these are not the same as trace state variables,
13344 which are managed by the target.
13347 (@value{GDBP}) @b{tfind start}
13349 (@value{GDBP}) @b{while $trace_frame != -1}
13350 > output $trace_file
13351 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
13357 @section Using Trace Files
13358 @cindex trace files
13360 In some situations, the target running a trace experiment may no
13361 longer be available; perhaps it crashed, or the hardware was needed
13362 for a different activity. To handle these cases, you can arrange to
13363 dump the trace data into a file, and later use that file as a source
13364 of trace data, via the @code{target tfile} command.
13369 @item tsave [ -r ] @var{filename}
13370 @itemx tsave [-ctf] @var{dirname}
13371 Save the trace data to @var{filename}. By default, this command
13372 assumes that @var{filename} refers to the host filesystem, so if
13373 necessary @value{GDBN} will copy raw trace data up from the target and
13374 then save it. If the target supports it, you can also supply the
13375 optional argument @code{-r} (``remote'') to direct the target to save
13376 the data directly into @var{filename} in its own filesystem, which may be
13377 more efficient if the trace buffer is very large. (Note, however, that
13378 @code{target tfile} can only read from files accessible to the host.)
13379 By default, this command will save trace frame in tfile format.
13380 You can supply the optional argument @code{-ctf} to save date in CTF
13381 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
13382 that can be shared by multiple debugging and tracing tools. Please go to
13383 @indicateurl{http://www.efficios.com/ctf} to get more information.
13385 @kindex target tfile
13389 @item target tfile @var{filename}
13390 @itemx target ctf @var{dirname}
13391 Use the file named @var{filename} or directory named @var{dirname} as
13392 a source of trace data. Commands that examine data work as they do with
13393 a live target, but it is not possible to run any new trace experiments.
13394 @code{tstatus} will report the state of the trace run at the moment
13395 the data was saved, as well as the current trace frame you are examining.
13396 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
13400 (@value{GDBP}) target ctf ctf.ctf
13401 (@value{GDBP}) tfind
13402 Found trace frame 0, tracepoint 2
13403 39 ++a; /* set tracepoint 1 here */
13404 (@value{GDBP}) tdump
13405 Data collected at tracepoint 2, trace frame 0:
13409 c = @{"123", "456", "789", "123", "456", "789"@}
13410 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
13418 @chapter Debugging Programs That Use Overlays
13421 If your program is too large to fit completely in your target system's
13422 memory, you can sometimes use @dfn{overlays} to work around this
13423 problem. @value{GDBN} provides some support for debugging programs that
13427 * How Overlays Work:: A general explanation of overlays.
13428 * Overlay Commands:: Managing overlays in @value{GDBN}.
13429 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
13430 mapped by asking the inferior.
13431 * Overlay Sample Program:: A sample program using overlays.
13434 @node How Overlays Work
13435 @section How Overlays Work
13436 @cindex mapped overlays
13437 @cindex unmapped overlays
13438 @cindex load address, overlay's
13439 @cindex mapped address
13440 @cindex overlay area
13442 Suppose you have a computer whose instruction address space is only 64
13443 kilobytes long, but which has much more memory which can be accessed by
13444 other means: special instructions, segment registers, or memory
13445 management hardware, for example. Suppose further that you want to
13446 adapt a program which is larger than 64 kilobytes to run on this system.
13448 One solution is to identify modules of your program which are relatively
13449 independent, and need not call each other directly; call these modules
13450 @dfn{overlays}. Separate the overlays from the main program, and place
13451 their machine code in the larger memory. Place your main program in
13452 instruction memory, but leave at least enough space there to hold the
13453 largest overlay as well.
13455 Now, to call a function located in an overlay, you must first copy that
13456 overlay's machine code from the large memory into the space set aside
13457 for it in the instruction memory, and then jump to its entry point
13460 @c NB: In the below the mapped area's size is greater or equal to the
13461 @c size of all overlays. This is intentional to remind the developer
13462 @c that overlays don't necessarily need to be the same size.
13466 Data Instruction Larger
13467 Address Space Address Space Address Space
13468 +-----------+ +-----------+ +-----------+
13470 +-----------+ +-----------+ +-----------+<-- overlay 1
13471 | program | | main | .----| overlay 1 | load address
13472 | variables | | program | | +-----------+
13473 | and heap | | | | | |
13474 +-----------+ | | | +-----------+<-- overlay 2
13475 | | +-----------+ | | | load address
13476 +-----------+ | | | .-| overlay 2 |
13478 mapped --->+-----------+ | | +-----------+
13479 address | | | | | |
13480 | overlay | <-' | | |
13481 | area | <---' +-----------+<-- overlay 3
13482 | | <---. | | load address
13483 +-----------+ `--| overlay 3 |
13490 @anchor{A code overlay}A code overlay
13494 The diagram (@pxref{A code overlay}) shows a system with separate data
13495 and instruction address spaces. To map an overlay, the program copies
13496 its code from the larger address space to the instruction address space.
13497 Since the overlays shown here all use the same mapped address, only one
13498 may be mapped at a time. For a system with a single address space for
13499 data and instructions, the diagram would be similar, except that the
13500 program variables and heap would share an address space with the main
13501 program and the overlay area.
13503 An overlay loaded into instruction memory and ready for use is called a
13504 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
13505 instruction memory. An overlay not present (or only partially present)
13506 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
13507 is its address in the larger memory. The mapped address is also called
13508 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
13509 called the @dfn{load memory address}, or @dfn{LMA}.
13511 Unfortunately, overlays are not a completely transparent way to adapt a
13512 program to limited instruction memory. They introduce a new set of
13513 global constraints you must keep in mind as you design your program:
13518 Before calling or returning to a function in an overlay, your program
13519 must make sure that overlay is actually mapped. Otherwise, the call or
13520 return will transfer control to the right address, but in the wrong
13521 overlay, and your program will probably crash.
13524 If the process of mapping an overlay is expensive on your system, you
13525 will need to choose your overlays carefully to minimize their effect on
13526 your program's performance.
13529 The executable file you load onto your system must contain each
13530 overlay's instructions, appearing at the overlay's load address, not its
13531 mapped address. However, each overlay's instructions must be relocated
13532 and its symbols defined as if the overlay were at its mapped address.
13533 You can use GNU linker scripts to specify different load and relocation
13534 addresses for pieces of your program; see @ref{Overlay Description,,,
13535 ld.info, Using ld: the GNU linker}.
13538 The procedure for loading executable files onto your system must be able
13539 to load their contents into the larger address space as well as the
13540 instruction and data spaces.
13544 The overlay system described above is rather simple, and could be
13545 improved in many ways:
13550 If your system has suitable bank switch registers or memory management
13551 hardware, you could use those facilities to make an overlay's load area
13552 contents simply appear at their mapped address in instruction space.
13553 This would probably be faster than copying the overlay to its mapped
13554 area in the usual way.
13557 If your overlays are small enough, you could set aside more than one
13558 overlay area, and have more than one overlay mapped at a time.
13561 You can use overlays to manage data, as well as instructions. In
13562 general, data overlays are even less transparent to your design than
13563 code overlays: whereas code overlays only require care when you call or
13564 return to functions, data overlays require care every time you access
13565 the data. Also, if you change the contents of a data overlay, you
13566 must copy its contents back out to its load address before you can copy a
13567 different data overlay into the same mapped area.
13572 @node Overlay Commands
13573 @section Overlay Commands
13575 To use @value{GDBN}'s overlay support, each overlay in your program must
13576 correspond to a separate section of the executable file. The section's
13577 virtual memory address and load memory address must be the overlay's
13578 mapped and load addresses. Identifying overlays with sections allows
13579 @value{GDBN} to determine the appropriate address of a function or
13580 variable, depending on whether the overlay is mapped or not.
13582 @value{GDBN}'s overlay commands all start with the word @code{overlay};
13583 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
13588 Disable @value{GDBN}'s overlay support. When overlay support is
13589 disabled, @value{GDBN} assumes that all functions and variables are
13590 always present at their mapped addresses. By default, @value{GDBN}'s
13591 overlay support is disabled.
13593 @item overlay manual
13594 @cindex manual overlay debugging
13595 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
13596 relies on you to tell it which overlays are mapped, and which are not,
13597 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
13598 commands described below.
13600 @item overlay map-overlay @var{overlay}
13601 @itemx overlay map @var{overlay}
13602 @cindex map an overlay
13603 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
13604 be the name of the object file section containing the overlay. When an
13605 overlay is mapped, @value{GDBN} assumes it can find the overlay's
13606 functions and variables at their mapped addresses. @value{GDBN} assumes
13607 that any other overlays whose mapped ranges overlap that of
13608 @var{overlay} are now unmapped.
13610 @item overlay unmap-overlay @var{overlay}
13611 @itemx overlay unmap @var{overlay}
13612 @cindex unmap an overlay
13613 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
13614 must be the name of the object file section containing the overlay.
13615 When an overlay is unmapped, @value{GDBN} assumes it can find the
13616 overlay's functions and variables at their load addresses.
13619 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
13620 consults a data structure the overlay manager maintains in the inferior
13621 to see which overlays are mapped. For details, see @ref{Automatic
13622 Overlay Debugging}.
13624 @item overlay load-target
13625 @itemx overlay load
13626 @cindex reloading the overlay table
13627 Re-read the overlay table from the inferior. Normally, @value{GDBN}
13628 re-reads the table @value{GDBN} automatically each time the inferior
13629 stops, so this command should only be necessary if you have changed the
13630 overlay mapping yourself using @value{GDBN}. This command is only
13631 useful when using automatic overlay debugging.
13633 @item overlay list-overlays
13634 @itemx overlay list
13635 @cindex listing mapped overlays
13636 Display a list of the overlays currently mapped, along with their mapped
13637 addresses, load addresses, and sizes.
13641 Normally, when @value{GDBN} prints a code address, it includes the name
13642 of the function the address falls in:
13645 (@value{GDBP}) print main
13646 $3 = @{int ()@} 0x11a0 <main>
13649 When overlay debugging is enabled, @value{GDBN} recognizes code in
13650 unmapped overlays, and prints the names of unmapped functions with
13651 asterisks around them. For example, if @code{foo} is a function in an
13652 unmapped overlay, @value{GDBN} prints it this way:
13655 (@value{GDBP}) overlay list
13656 No sections are mapped.
13657 (@value{GDBP}) print foo
13658 $5 = @{int (int)@} 0x100000 <*foo*>
13661 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
13665 (@value{GDBP}) overlay list
13666 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
13667 mapped at 0x1016 - 0x104a
13668 (@value{GDBP}) print foo
13669 $6 = @{int (int)@} 0x1016 <foo>
13672 When overlay debugging is enabled, @value{GDBN} can find the correct
13673 address for functions and variables in an overlay, whether or not the
13674 overlay is mapped. This allows most @value{GDBN} commands, like
13675 @code{break} and @code{disassemble}, to work normally, even on unmapped
13676 code. However, @value{GDBN}'s breakpoint support has some limitations:
13680 @cindex breakpoints in overlays
13681 @cindex overlays, setting breakpoints in
13682 You can set breakpoints in functions in unmapped overlays, as long as
13683 @value{GDBN} can write to the overlay at its load address.
13685 @value{GDBN} can not set hardware or simulator-based breakpoints in
13686 unmapped overlays. However, if you set a breakpoint at the end of your
13687 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
13688 you are using manual overlay management), @value{GDBN} will re-set its
13689 breakpoints properly.
13693 @node Automatic Overlay Debugging
13694 @section Automatic Overlay Debugging
13695 @cindex automatic overlay debugging
13697 @value{GDBN} can automatically track which overlays are mapped and which
13698 are not, given some simple co-operation from the overlay manager in the
13699 inferior. If you enable automatic overlay debugging with the
13700 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
13701 looks in the inferior's memory for certain variables describing the
13702 current state of the overlays.
13704 Here are the variables your overlay manager must define to support
13705 @value{GDBN}'s automatic overlay debugging:
13709 @item @code{_ovly_table}:
13710 This variable must be an array of the following structures:
13715 /* The overlay's mapped address. */
13718 /* The size of the overlay, in bytes. */
13719 unsigned long size;
13721 /* The overlay's load address. */
13724 /* Non-zero if the overlay is currently mapped;
13726 unsigned long mapped;
13730 @item @code{_novlys}:
13731 This variable must be a four-byte signed integer, holding the total
13732 number of elements in @code{_ovly_table}.
13736 To decide whether a particular overlay is mapped or not, @value{GDBN}
13737 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
13738 @code{lma} members equal the VMA and LMA of the overlay's section in the
13739 executable file. When @value{GDBN} finds a matching entry, it consults
13740 the entry's @code{mapped} member to determine whether the overlay is
13743 In addition, your overlay manager may define a function called
13744 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
13745 will silently set a breakpoint there. If the overlay manager then
13746 calls this function whenever it has changed the overlay table, this
13747 will enable @value{GDBN} to accurately keep track of which overlays
13748 are in program memory, and update any breakpoints that may be set
13749 in overlays. This will allow breakpoints to work even if the
13750 overlays are kept in ROM or other non-writable memory while they
13751 are not being executed.
13753 @node Overlay Sample Program
13754 @section Overlay Sample Program
13755 @cindex overlay example program
13757 When linking a program which uses overlays, you must place the overlays
13758 at their load addresses, while relocating them to run at their mapped
13759 addresses. To do this, you must write a linker script (@pxref{Overlay
13760 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
13761 since linker scripts are specific to a particular host system, target
13762 architecture, and target memory layout, this manual cannot provide
13763 portable sample code demonstrating @value{GDBN}'s overlay support.
13765 However, the @value{GDBN} source distribution does contain an overlaid
13766 program, with linker scripts for a few systems, as part of its test
13767 suite. The program consists of the following files from
13768 @file{gdb/testsuite/gdb.base}:
13772 The main program file.
13774 A simple overlay manager, used by @file{overlays.c}.
13779 Overlay modules, loaded and used by @file{overlays.c}.
13782 Linker scripts for linking the test program on the @code{d10v-elf}
13783 and @code{m32r-elf} targets.
13786 You can build the test program using the @code{d10v-elf} GCC
13787 cross-compiler like this:
13790 $ d10v-elf-gcc -g -c overlays.c
13791 $ d10v-elf-gcc -g -c ovlymgr.c
13792 $ d10v-elf-gcc -g -c foo.c
13793 $ d10v-elf-gcc -g -c bar.c
13794 $ d10v-elf-gcc -g -c baz.c
13795 $ d10v-elf-gcc -g -c grbx.c
13796 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
13797 baz.o grbx.o -Wl,-Td10v.ld -o overlays
13800 The build process is identical for any other architecture, except that
13801 you must substitute the appropriate compiler and linker script for the
13802 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
13806 @chapter Using @value{GDBN} with Different Languages
13809 Although programming languages generally have common aspects, they are
13810 rarely expressed in the same manner. For instance, in ANSI C,
13811 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
13812 Modula-2, it is accomplished by @code{p^}. Values can also be
13813 represented (and displayed) differently. Hex numbers in C appear as
13814 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
13816 @cindex working language
13817 Language-specific information is built into @value{GDBN} for some languages,
13818 allowing you to express operations like the above in your program's
13819 native language, and allowing @value{GDBN} to output values in a manner
13820 consistent with the syntax of your program's native language. The
13821 language you use to build expressions is called the @dfn{working
13825 * Setting:: Switching between source languages
13826 * Show:: Displaying the language
13827 * Checks:: Type and range checks
13828 * Supported Languages:: Supported languages
13829 * Unsupported Languages:: Unsupported languages
13833 @section Switching Between Source Languages
13835 There are two ways to control the working language---either have @value{GDBN}
13836 set it automatically, or select it manually yourself. You can use the
13837 @code{set language} command for either purpose. On startup, @value{GDBN}
13838 defaults to setting the language automatically. The working language is
13839 used to determine how expressions you type are interpreted, how values
13842 In addition to the working language, every source file that
13843 @value{GDBN} knows about has its own working language. For some object
13844 file formats, the compiler might indicate which language a particular
13845 source file is in. However, most of the time @value{GDBN} infers the
13846 language from the name of the file. The language of a source file
13847 controls whether C@t{++} names are demangled---this way @code{backtrace} can
13848 show each frame appropriately for its own language. There is no way to
13849 set the language of a source file from within @value{GDBN}, but you can
13850 set the language associated with a filename extension. @xref{Show, ,
13851 Displaying the Language}.
13853 This is most commonly a problem when you use a program, such
13854 as @code{cfront} or @code{f2c}, that generates C but is written in
13855 another language. In that case, make the
13856 program use @code{#line} directives in its C output; that way
13857 @value{GDBN} will know the correct language of the source code of the original
13858 program, and will display that source code, not the generated C code.
13861 * Filenames:: Filename extensions and languages.
13862 * Manually:: Setting the working language manually
13863 * Automatically:: Having @value{GDBN} infer the source language
13867 @subsection List of Filename Extensions and Languages
13869 If a source file name ends in one of the following extensions, then
13870 @value{GDBN} infers that its language is the one indicated.
13888 C@t{++} source file
13894 Objective-C source file
13898 Fortran source file
13901 Modula-2 source file
13905 Assembler source file. This actually behaves almost like C, but
13906 @value{GDBN} does not skip over function prologues when stepping.
13909 In addition, you may set the language associated with a filename
13910 extension. @xref{Show, , Displaying the Language}.
13913 @subsection Setting the Working Language
13915 If you allow @value{GDBN} to set the language automatically,
13916 expressions are interpreted the same way in your debugging session and
13919 @kindex set language
13920 If you wish, you may set the language manually. To do this, issue the
13921 command @samp{set language @var{lang}}, where @var{lang} is the name of
13922 a language, such as
13923 @code{c} or @code{modula-2}.
13924 For a list of the supported languages, type @samp{set language}.
13926 Setting the language manually prevents @value{GDBN} from updating the working
13927 language automatically. This can lead to confusion if you try
13928 to debug a program when the working language is not the same as the
13929 source language, when an expression is acceptable to both
13930 languages---but means different things. For instance, if the current
13931 source file were written in C, and @value{GDBN} was parsing Modula-2, a
13939 might not have the effect you intended. In C, this means to add
13940 @code{b} and @code{c} and place the result in @code{a}. The result
13941 printed would be the value of @code{a}. In Modula-2, this means to compare
13942 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
13944 @node Automatically
13945 @subsection Having @value{GDBN} Infer the Source Language
13947 To have @value{GDBN} set the working language automatically, use
13948 @samp{set language local} or @samp{set language auto}. @value{GDBN}
13949 then infers the working language. That is, when your program stops in a
13950 frame (usually by encountering a breakpoint), @value{GDBN} sets the
13951 working language to the language recorded for the function in that
13952 frame. If the language for a frame is unknown (that is, if the function
13953 or block corresponding to the frame was defined in a source file that
13954 does not have a recognized extension), the current working language is
13955 not changed, and @value{GDBN} issues a warning.
13957 This may not seem necessary for most programs, which are written
13958 entirely in one source language. However, program modules and libraries
13959 written in one source language can be used by a main program written in
13960 a different source language. Using @samp{set language auto} in this
13961 case frees you from having to set the working language manually.
13964 @section Displaying the Language
13966 The following commands help you find out which language is the
13967 working language, and also what language source files were written in.
13970 @item show language
13971 @anchor{show language}
13972 @kindex show language
13973 Display the current working language. This is the
13974 language you can use with commands such as @code{print} to
13975 build and compute expressions that may involve variables in your program.
13978 @kindex info frame@r{, show the source language}
13979 Display the source language for this frame. This language becomes the
13980 working language if you use an identifier from this frame.
13981 @xref{Frame Info, ,Information about a Frame}, to identify the other
13982 information listed here.
13985 @kindex info source@r{, show the source language}
13986 Display the source language of this source file.
13987 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
13988 information listed here.
13991 In unusual circumstances, you may have source files with extensions
13992 not in the standard list. You can then set the extension associated
13993 with a language explicitly:
13996 @item set extension-language @var{ext} @var{language}
13997 @kindex set extension-language
13998 Tell @value{GDBN} that source files with extension @var{ext} are to be
13999 assumed as written in the source language @var{language}.
14001 @item info extensions
14002 @kindex info extensions
14003 List all the filename extensions and the associated languages.
14007 @section Type and Range Checking
14009 Some languages are designed to guard you against making seemingly common
14010 errors through a series of compile- and run-time checks. These include
14011 checking the type of arguments to functions and operators and making
14012 sure mathematical overflows are caught at run time. Checks such as
14013 these help to ensure a program's correctness once it has been compiled
14014 by eliminating type mismatches and providing active checks for range
14015 errors when your program is running.
14017 By default @value{GDBN} checks for these errors according to the
14018 rules of the current source language. Although @value{GDBN} does not check
14019 the statements in your program, it can check expressions entered directly
14020 into @value{GDBN} for evaluation via the @code{print} command, for example.
14023 * Type Checking:: An overview of type checking
14024 * Range Checking:: An overview of range checking
14027 @cindex type checking
14028 @cindex checks, type
14029 @node Type Checking
14030 @subsection An Overview of Type Checking
14032 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
14033 arguments to operators and functions have to be of the correct type,
14034 otherwise an error occurs. These checks prevent type mismatch
14035 errors from ever causing any run-time problems. For example,
14038 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
14040 (@value{GDBP}) print obj.my_method (0)
14043 (@value{GDBP}) print obj.my_method (0x1234)
14044 Cannot resolve method klass::my_method to any overloaded instance
14047 The second example fails because in C@t{++} the integer constant
14048 @samp{0x1234} is not type-compatible with the pointer parameter type.
14050 For the expressions you use in @value{GDBN} commands, you can tell
14051 @value{GDBN} to not enforce strict type checking or
14052 to treat any mismatches as errors and abandon the expression;
14053 When type checking is disabled, @value{GDBN} successfully evaluates
14054 expressions like the second example above.
14056 Even if type checking is off, there may be other reasons
14057 related to type that prevent @value{GDBN} from evaluating an expression.
14058 For instance, @value{GDBN} does not know how to add an @code{int} and
14059 a @code{struct foo}. These particular type errors have nothing to do
14060 with the language in use and usually arise from expressions which make
14061 little sense to evaluate anyway.
14063 @value{GDBN} provides some additional commands for controlling type checking:
14065 @kindex set check type
14066 @kindex show check type
14068 @item set check type on
14069 @itemx set check type off
14070 Set strict type checking on or off. If any type mismatches occur in
14071 evaluating an expression while type checking is on, @value{GDBN} prints a
14072 message and aborts evaluation of the expression.
14074 @item show check type
14075 Show the current setting of type checking and whether @value{GDBN}
14076 is enforcing strict type checking rules.
14079 @cindex range checking
14080 @cindex checks, range
14081 @node Range Checking
14082 @subsection An Overview of Range Checking
14084 In some languages (such as Modula-2), it is an error to exceed the
14085 bounds of a type; this is enforced with run-time checks. Such range
14086 checking is meant to ensure program correctness by making sure
14087 computations do not overflow, or indices on an array element access do
14088 not exceed the bounds of the array.
14090 For expressions you use in @value{GDBN} commands, you can tell
14091 @value{GDBN} to treat range errors in one of three ways: ignore them,
14092 always treat them as errors and abandon the expression, or issue
14093 warnings but evaluate the expression anyway.
14095 A range error can result from numerical overflow, from exceeding an
14096 array index bound, or when you type a constant that is not a member
14097 of any type. Some languages, however, do not treat overflows as an
14098 error. In many implementations of C, mathematical overflow causes the
14099 result to ``wrap around'' to lower values---for example, if @var{m} is
14100 the largest integer value, and @var{s} is the smallest, then
14103 @var{m} + 1 @result{} @var{s}
14106 This, too, is specific to individual languages, and in some cases
14107 specific to individual compilers or machines. @xref{Supported Languages, ,
14108 Supported Languages}, for further details on specific languages.
14110 @value{GDBN} provides some additional commands for controlling the range checker:
14112 @kindex set check range
14113 @kindex show check range
14115 @item set check range auto
14116 Set range checking on or off based on the current working language.
14117 @xref{Supported Languages, ,Supported Languages}, for the default settings for
14120 @item set check range on
14121 @itemx set check range off
14122 Set range checking on or off, overriding the default setting for the
14123 current working language. A warning is issued if the setting does not
14124 match the language default. If a range error occurs and range checking is on,
14125 then a message is printed and evaluation of the expression is aborted.
14127 @item set check range warn
14128 Output messages when the @value{GDBN} range checker detects a range error,
14129 but attempt to evaluate the expression anyway. Evaluating the
14130 expression may still be impossible for other reasons, such as accessing
14131 memory that the process does not own (a typical example from many Unix
14135 Show the current setting of the range checker, and whether or not it is
14136 being set automatically by @value{GDBN}.
14139 @node Supported Languages
14140 @section Supported Languages
14142 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
14143 OpenCL C, Pascal, assembly, Modula-2, and Ada.
14144 @c This is false ...
14145 Some @value{GDBN} features may be used in expressions regardless of the
14146 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
14147 and the @samp{@{type@}addr} construct (@pxref{Expressions,
14148 ,Expressions}) can be used with the constructs of any supported
14151 The following sections detail to what degree each source language is
14152 supported by @value{GDBN}. These sections are not meant to be language
14153 tutorials or references, but serve only as a reference guide to what the
14154 @value{GDBN} expression parser accepts, and what input and output
14155 formats should look like for different languages. There are many good
14156 books written on each of these languages; please look to these for a
14157 language reference or tutorial.
14160 * C:: C and C@t{++}
14163 * Objective-C:: Objective-C
14164 * OpenCL C:: OpenCL C
14165 * Fortran:: Fortran
14167 * Modula-2:: Modula-2
14172 @subsection C and C@t{++}
14174 @cindex C and C@t{++}
14175 @cindex expressions in C or C@t{++}
14177 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
14178 to both languages. Whenever this is the case, we discuss those languages
14182 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
14183 @cindex @sc{gnu} C@t{++}
14184 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
14185 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
14186 effectively, you must compile your C@t{++} programs with a supported
14187 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
14188 compiler (@code{aCC}).
14191 * C Operators:: C and C@t{++} operators
14192 * C Constants:: C and C@t{++} constants
14193 * C Plus Plus Expressions:: C@t{++} expressions
14194 * C Defaults:: Default settings for C and C@t{++}
14195 * C Checks:: C and C@t{++} type and range checks
14196 * Debugging C:: @value{GDBN} and C
14197 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
14198 * Decimal Floating Point:: Numbers in Decimal Floating Point format
14202 @subsubsection C and C@t{++} Operators
14204 @cindex C and C@t{++} operators
14206 Operators must be defined on values of specific types. For instance,
14207 @code{+} is defined on numbers, but not on structures. Operators are
14208 often defined on groups of types.
14210 For the purposes of C and C@t{++}, the following definitions hold:
14215 @emph{Integral types} include @code{int} with any of its storage-class
14216 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
14219 @emph{Floating-point types} include @code{float}, @code{double}, and
14220 @code{long double} (if supported by the target platform).
14223 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
14226 @emph{Scalar types} include all of the above.
14231 The following operators are supported. They are listed here
14232 in order of increasing precedence:
14236 The comma or sequencing operator. Expressions in a comma-separated list
14237 are evaluated from left to right, with the result of the entire
14238 expression being the last expression evaluated.
14241 Assignment. The value of an assignment expression is the value
14242 assigned. Defined on scalar types.
14245 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
14246 and translated to @w{@code{@var{a} = @var{a op b}}}.
14247 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
14248 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
14249 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
14252 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
14253 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
14254 should be of an integral type.
14257 Logical @sc{or}. Defined on integral types.
14260 Logical @sc{and}. Defined on integral types.
14263 Bitwise @sc{or}. Defined on integral types.
14266 Bitwise exclusive-@sc{or}. Defined on integral types.
14269 Bitwise @sc{and}. Defined on integral types.
14272 Equality and inequality. Defined on scalar types. The value of these
14273 expressions is 0 for false and non-zero for true.
14275 @item <@r{, }>@r{, }<=@r{, }>=
14276 Less than, greater than, less than or equal, greater than or equal.
14277 Defined on scalar types. The value of these expressions is 0 for false
14278 and non-zero for true.
14281 left shift, and right shift. Defined on integral types.
14284 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14287 Addition and subtraction. Defined on integral types, floating-point types and
14290 @item *@r{, }/@r{, }%
14291 Multiplication, division, and modulus. Multiplication and division are
14292 defined on integral and floating-point types. Modulus is defined on
14296 Increment and decrement. When appearing before a variable, the
14297 operation is performed before the variable is used in an expression;
14298 when appearing after it, the variable's value is used before the
14299 operation takes place.
14302 Pointer dereferencing. Defined on pointer types. Same precedence as
14306 Address operator. Defined on variables. Same precedence as @code{++}.
14308 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
14309 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
14310 to examine the address
14311 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
14315 Negative. Defined on integral and floating-point types. Same
14316 precedence as @code{++}.
14319 Logical negation. Defined on integral types. Same precedence as
14323 Bitwise complement operator. Defined on integral types. Same precedence as
14328 Structure member, and pointer-to-structure member. For convenience,
14329 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
14330 pointer based on the stored type information.
14331 Defined on @code{struct} and @code{union} data.
14334 Dereferences of pointers to members.
14337 Array indexing. @code{@var{a}[@var{i}]} is defined as
14338 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
14341 Function parameter list. Same precedence as @code{->}.
14344 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
14345 and @code{class} types.
14348 Doubled colons also represent the @value{GDBN} scope operator
14349 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
14353 If an operator is redefined in the user code, @value{GDBN} usually
14354 attempts to invoke the redefined version instead of using the operator's
14355 predefined meaning.
14358 @subsubsection C and C@t{++} Constants
14360 @cindex C and C@t{++} constants
14362 @value{GDBN} allows you to express the constants of C and C@t{++} in the
14367 Integer constants are a sequence of digits. Octal constants are
14368 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
14369 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
14370 @samp{l}, specifying that the constant should be treated as a
14374 Floating point constants are a sequence of digits, followed by a decimal
14375 point, followed by a sequence of digits, and optionally followed by an
14376 exponent. An exponent is of the form:
14377 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
14378 sequence of digits. The @samp{+} is optional for positive exponents.
14379 A floating-point constant may also end with a letter @samp{f} or
14380 @samp{F}, specifying that the constant should be treated as being of
14381 the @code{float} (as opposed to the default @code{double}) type; or with
14382 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
14386 Enumerated constants consist of enumerated identifiers, or their
14387 integral equivalents.
14390 Character constants are a single character surrounded by single quotes
14391 (@code{'}), or a number---the ordinal value of the corresponding character
14392 (usually its @sc{ascii} value). Within quotes, the single character may
14393 be represented by a letter or by @dfn{escape sequences}, which are of
14394 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
14395 of the character's ordinal value; or of the form @samp{\@var{x}}, where
14396 @samp{@var{x}} is a predefined special character---for example,
14397 @samp{\n} for newline.
14399 Wide character constants can be written by prefixing a character
14400 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
14401 form of @samp{x}. The target wide character set is used when
14402 computing the value of this constant (@pxref{Character Sets}).
14405 String constants are a sequence of character constants surrounded by
14406 double quotes (@code{"}). Any valid character constant (as described
14407 above) may appear. Double quotes within the string must be preceded by
14408 a backslash, so for instance @samp{"a\"b'c"} is a string of five
14411 Wide string constants can be written by prefixing a string constant
14412 with @samp{L}, as in C. The target wide character set is used when
14413 computing the value of this constant (@pxref{Character Sets}).
14416 Pointer constants are an integral value. You can also write pointers
14417 to constants using the C operator @samp{&}.
14420 Array constants are comma-separated lists surrounded by braces @samp{@{}
14421 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
14422 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
14423 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
14426 @node C Plus Plus Expressions
14427 @subsubsection C@t{++} Expressions
14429 @cindex expressions in C@t{++}
14430 @value{GDBN} expression handling can interpret most C@t{++} expressions.
14432 @cindex debugging C@t{++} programs
14433 @cindex C@t{++} compilers
14434 @cindex debug formats and C@t{++}
14435 @cindex @value{NGCC} and C@t{++}
14437 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
14438 the proper compiler and the proper debug format. Currently,
14439 @value{GDBN} works best when debugging C@t{++} code that is compiled
14440 with the most recent version of @value{NGCC} possible. The DWARF
14441 debugging format is preferred; @value{NGCC} defaults to this on most
14442 popular platforms. Other compilers and/or debug formats are likely to
14443 work badly or not at all when using @value{GDBN} to debug C@t{++}
14444 code. @xref{Compilation}.
14449 @cindex member functions
14451 Member function calls are allowed; you can use expressions like
14454 count = aml->GetOriginal(x, y)
14457 @vindex this@r{, inside C@t{++} member functions}
14458 @cindex namespace in C@t{++}
14460 While a member function is active (in the selected stack frame), your
14461 expressions have the same namespace available as the member function;
14462 that is, @value{GDBN} allows implicit references to the class instance
14463 pointer @code{this} following the same rules as C@t{++}. @code{using}
14464 declarations in the current scope are also respected by @value{GDBN}.
14466 @cindex call overloaded functions
14467 @cindex overloaded functions, calling
14468 @cindex type conversions in C@t{++}
14470 You can call overloaded functions; @value{GDBN} resolves the function
14471 call to the right definition, with some restrictions. @value{GDBN} does not
14472 perform overload resolution involving user-defined type conversions,
14473 calls to constructors, or instantiations of templates that do not exist
14474 in the program. It also cannot handle ellipsis argument lists or
14477 It does perform integral conversions and promotions, floating-point
14478 promotions, arithmetic conversions, pointer conversions, conversions of
14479 class objects to base classes, and standard conversions such as those of
14480 functions or arrays to pointers; it requires an exact match on the
14481 number of function arguments.
14483 Overload resolution is always performed, unless you have specified
14484 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
14485 ,@value{GDBN} Features for C@t{++}}.
14487 You must specify @code{set overload-resolution off} in order to use an
14488 explicit function signature to call an overloaded function, as in
14490 p 'foo(char,int)'('x', 13)
14493 The @value{GDBN} command-completion facility can simplify this;
14494 see @ref{Completion, ,Command Completion}.
14496 @cindex reference declarations
14498 @value{GDBN} understands variables declared as C@t{++} references; you can use
14499 them in expressions just as you do in C@t{++} source---they are automatically
14502 In the parameter list shown when @value{GDBN} displays a frame, the values of
14503 reference variables are not displayed (unlike other variables); this
14504 avoids clutter, since references are often used for large structures.
14505 The @emph{address} of a reference variable is always shown, unless
14506 you have specified @samp{set print address off}.
14509 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
14510 expressions can use it just as expressions in your program do. Since
14511 one scope may be defined in another, you can use @code{::} repeatedly if
14512 necessary, for example in an expression like
14513 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
14514 resolving name scope by reference to source files, in both C and C@t{++}
14515 debugging (@pxref{Variables, ,Program Variables}).
14518 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
14523 @subsubsection C and C@t{++} Defaults
14525 @cindex C and C@t{++} defaults
14527 If you allow @value{GDBN} to set range checking automatically, it
14528 defaults to @code{off} whenever the working language changes to
14529 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
14530 selects the working language.
14532 If you allow @value{GDBN} to set the language automatically, it
14533 recognizes source files whose names end with @file{.c}, @file{.C}, or
14534 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
14535 these files, it sets the working language to C or C@t{++}.
14536 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
14537 for further details.
14540 @subsubsection C and C@t{++} Type and Range Checks
14542 @cindex C and C@t{++} checks
14544 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
14545 checking is used. However, if you turn type checking off, @value{GDBN}
14546 will allow certain non-standard conversions, such as promoting integer
14547 constants to pointers.
14549 Range checking, if turned on, is done on mathematical operations. Array
14550 indices are not checked, since they are often used to index a pointer
14551 that is not itself an array.
14554 @subsubsection @value{GDBN} and C
14556 The @code{set print union} and @code{show print union} commands apply to
14557 the @code{union} type. When set to @samp{on}, any @code{union} that is
14558 inside a @code{struct} or @code{class} is also printed. Otherwise, it
14559 appears as @samp{@{...@}}.
14561 The @code{@@} operator aids in the debugging of dynamic arrays, formed
14562 with pointers and a memory allocation function. @xref{Expressions,
14565 @node Debugging C Plus Plus
14566 @subsubsection @value{GDBN} Features for C@t{++}
14568 @cindex commands for C@t{++}
14570 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
14571 designed specifically for use with C@t{++}. Here is a summary:
14574 @cindex break in overloaded functions
14575 @item @r{breakpoint menus}
14576 When you want a breakpoint in a function whose name is overloaded,
14577 @value{GDBN} has the capability to display a menu of possible breakpoint
14578 locations to help you specify which function definition you want.
14579 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
14581 @cindex overloading in C@t{++}
14582 @item rbreak @var{regex}
14583 Setting breakpoints using regular expressions is helpful for setting
14584 breakpoints on overloaded functions that are not members of any special
14586 @xref{Set Breaks, ,Setting Breakpoints}.
14588 @cindex C@t{++} exception handling
14590 @itemx catch rethrow
14592 Debug C@t{++} exception handling using these commands. @xref{Set
14593 Catchpoints, , Setting Catchpoints}.
14595 @cindex inheritance
14596 @item ptype @var{typename}
14597 Print inheritance relationships as well as other information for type
14599 @xref{Symbols, ,Examining the Symbol Table}.
14601 @item info vtbl @var{expression}.
14602 The @code{info vtbl} command can be used to display the virtual
14603 method tables of the object computed by @var{expression}. This shows
14604 one entry per virtual table; there may be multiple virtual tables when
14605 multiple inheritance is in use.
14607 @cindex C@t{++} demangling
14608 @item demangle @var{name}
14609 Demangle @var{name}.
14610 @xref{Symbols}, for a more complete description of the @code{demangle} command.
14612 @cindex C@t{++} symbol display
14613 @item set print demangle
14614 @itemx show print demangle
14615 @itemx set print asm-demangle
14616 @itemx show print asm-demangle
14617 Control whether C@t{++} symbols display in their source form, both when
14618 displaying code as C@t{++} source and when displaying disassemblies.
14619 @xref{Print Settings, ,Print Settings}.
14621 @item set print object
14622 @itemx show print object
14623 Choose whether to print derived (actual) or declared types of objects.
14624 @xref{Print Settings, ,Print Settings}.
14626 @item set print vtbl
14627 @itemx show print vtbl
14628 Control the format for printing virtual function tables.
14629 @xref{Print Settings, ,Print Settings}.
14630 (The @code{vtbl} commands do not work on programs compiled with the HP
14631 ANSI C@t{++} compiler (@code{aCC}).)
14633 @kindex set overload-resolution
14634 @cindex overloaded functions, overload resolution
14635 @item set overload-resolution on
14636 Enable overload resolution for C@t{++} expression evaluation. The default
14637 is on. For overloaded functions, @value{GDBN} evaluates the arguments
14638 and searches for a function whose signature matches the argument types,
14639 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
14640 Expressions, ,C@t{++} Expressions}, for details).
14641 If it cannot find a match, it emits a message.
14643 @item set overload-resolution off
14644 Disable overload resolution for C@t{++} expression evaluation. For
14645 overloaded functions that are not class member functions, @value{GDBN}
14646 chooses the first function of the specified name that it finds in the
14647 symbol table, whether or not its arguments are of the correct type. For
14648 overloaded functions that are class member functions, @value{GDBN}
14649 searches for a function whose signature @emph{exactly} matches the
14652 @kindex show overload-resolution
14653 @item show overload-resolution
14654 Show the current setting of overload resolution.
14656 @item @r{Overloaded symbol names}
14657 You can specify a particular definition of an overloaded symbol, using
14658 the same notation that is used to declare such symbols in C@t{++}: type
14659 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
14660 also use the @value{GDBN} command-line word completion facilities to list the
14661 available choices, or to finish the type list for you.
14662 @xref{Completion,, Command Completion}, for details on how to do this.
14665 @node Decimal Floating Point
14666 @subsubsection Decimal Floating Point format
14667 @cindex decimal floating point format
14669 @value{GDBN} can examine, set and perform computations with numbers in
14670 decimal floating point format, which in the C language correspond to the
14671 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
14672 specified by the extension to support decimal floating-point arithmetic.
14674 There are two encodings in use, depending on the architecture: BID (Binary
14675 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
14676 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
14679 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
14680 to manipulate decimal floating point numbers, it is not possible to convert
14681 (using a cast, for example) integers wider than 32-bit to decimal float.
14683 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
14684 point computations, error checking in decimal float operations ignores
14685 underflow, overflow and divide by zero exceptions.
14687 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
14688 to inspect @code{_Decimal128} values stored in floating point registers.
14689 See @ref{PowerPC,,PowerPC} for more details.
14695 @value{GDBN} can be used to debug programs written in D and compiled with
14696 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
14697 specific feature --- dynamic arrays.
14702 @cindex Go (programming language)
14703 @value{GDBN} can be used to debug programs written in Go and compiled with
14704 @file{gccgo} or @file{6g} compilers.
14706 Here is a summary of the Go-specific features and restrictions:
14709 @cindex current Go package
14710 @item The current Go package
14711 The name of the current package does not need to be specified when
14712 specifying global variables and functions.
14714 For example, given the program:
14718 var myglob = "Shall we?"
14724 When stopped inside @code{main} either of these work:
14728 (gdb) p main.myglob
14731 @cindex builtin Go types
14732 @item Builtin Go types
14733 The @code{string} type is recognized by @value{GDBN} and is printed
14736 @cindex builtin Go functions
14737 @item Builtin Go functions
14738 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
14739 function and handles it internally.
14741 @cindex restrictions on Go expressions
14742 @item Restrictions on Go expressions
14743 All Go operators are supported except @code{&^}.
14744 The Go @code{_} ``blank identifier'' is not supported.
14745 Automatic dereferencing of pointers is not supported.
14749 @subsection Objective-C
14751 @cindex Objective-C
14752 This section provides information about some commands and command
14753 options that are useful for debugging Objective-C code. See also
14754 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
14755 few more commands specific to Objective-C support.
14758 * Method Names in Commands::
14759 * The Print Command with Objective-C::
14762 @node Method Names in Commands
14763 @subsubsection Method Names in Commands
14765 The following commands have been extended to accept Objective-C method
14766 names as line specifications:
14768 @kindex clear@r{, and Objective-C}
14769 @kindex break@r{, and Objective-C}
14770 @kindex info line@r{, and Objective-C}
14771 @kindex jump@r{, and Objective-C}
14772 @kindex list@r{, and Objective-C}
14776 @item @code{info line}
14781 A fully qualified Objective-C method name is specified as
14784 -[@var{Class} @var{methodName}]
14787 where the minus sign is used to indicate an instance method and a
14788 plus sign (not shown) is used to indicate a class method. The class
14789 name @var{Class} and method name @var{methodName} are enclosed in
14790 brackets, similar to the way messages are specified in Objective-C
14791 source code. For example, to set a breakpoint at the @code{create}
14792 instance method of class @code{Fruit} in the program currently being
14796 break -[Fruit create]
14799 To list ten program lines around the @code{initialize} class method,
14803 list +[NSText initialize]
14806 In the current version of @value{GDBN}, the plus or minus sign is
14807 required. In future versions of @value{GDBN}, the plus or minus
14808 sign will be optional, but you can use it to narrow the search. It
14809 is also possible to specify just a method name:
14815 You must specify the complete method name, including any colons. If
14816 your program's source files contain more than one @code{create} method,
14817 you'll be presented with a numbered list of classes that implement that
14818 method. Indicate your choice by number, or type @samp{0} to exit if
14821 As another example, to clear a breakpoint established at the
14822 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
14825 clear -[NSWindow makeKeyAndOrderFront:]
14828 @node The Print Command with Objective-C
14829 @subsubsection The Print Command With Objective-C
14830 @cindex Objective-C, print objects
14831 @kindex print-object
14832 @kindex po @r{(@code{print-object})}
14834 The print command has also been extended to accept methods. For example:
14837 print -[@var{object} hash]
14840 @cindex print an Objective-C object description
14841 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
14843 will tell @value{GDBN} to send the @code{hash} message to @var{object}
14844 and print the result. Also, an additional command has been added,
14845 @code{print-object} or @code{po} for short, which is meant to print
14846 the description of an object. However, this command may only work
14847 with certain Objective-C libraries that have a particular hook
14848 function, @code{_NSPrintForDebugger}, defined.
14851 @subsection OpenCL C
14854 This section provides information about @value{GDBN}s OpenCL C support.
14857 * OpenCL C Datatypes::
14858 * OpenCL C Expressions::
14859 * OpenCL C Operators::
14862 @node OpenCL C Datatypes
14863 @subsubsection OpenCL C Datatypes
14865 @cindex OpenCL C Datatypes
14866 @value{GDBN} supports the builtin scalar and vector datatypes specified
14867 by OpenCL 1.1. In addition the half- and double-precision floating point
14868 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
14869 extensions are also known to @value{GDBN}.
14871 @node OpenCL C Expressions
14872 @subsubsection OpenCL C Expressions
14874 @cindex OpenCL C Expressions
14875 @value{GDBN} supports accesses to vector components including the access as
14876 lvalue where possible. Since OpenCL C is based on C99 most C expressions
14877 supported by @value{GDBN} can be used as well.
14879 @node OpenCL C Operators
14880 @subsubsection OpenCL C Operators
14882 @cindex OpenCL C Operators
14883 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
14887 @subsection Fortran
14888 @cindex Fortran-specific support in @value{GDBN}
14890 @value{GDBN} can be used to debug programs written in Fortran, but it
14891 currently supports only the features of Fortran 77 language.
14893 @cindex trailing underscore, in Fortran symbols
14894 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
14895 among them) append an underscore to the names of variables and
14896 functions. When you debug programs compiled by those compilers, you
14897 will need to refer to variables and functions with a trailing
14901 * Fortran Operators:: Fortran operators and expressions
14902 * Fortran Defaults:: Default settings for Fortran
14903 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
14906 @node Fortran Operators
14907 @subsubsection Fortran Operators and Expressions
14909 @cindex Fortran operators and expressions
14911 Operators must be defined on values of specific types. For instance,
14912 @code{+} is defined on numbers, but not on characters or other non-
14913 arithmetic types. Operators are often defined on groups of types.
14917 The exponentiation operator. It raises the first operand to the power
14921 The range operator. Normally used in the form of array(low:high) to
14922 represent a section of array.
14925 The access component operator. Normally used to access elements in derived
14926 types. Also suitable for unions. As unions aren't part of regular Fortran,
14927 this can only happen when accessing a register that uses a gdbarch-defined
14931 @node Fortran Defaults
14932 @subsubsection Fortran Defaults
14934 @cindex Fortran Defaults
14936 Fortran symbols are usually case-insensitive, so @value{GDBN} by
14937 default uses case-insensitive matches for Fortran symbols. You can
14938 change that with the @samp{set case-insensitive} command, see
14939 @ref{Symbols}, for the details.
14941 @node Special Fortran Commands
14942 @subsubsection Special Fortran Commands
14944 @cindex Special Fortran commands
14946 @value{GDBN} has some commands to support Fortran-specific features,
14947 such as displaying common blocks.
14950 @cindex @code{COMMON} blocks, Fortran
14951 @kindex info common
14952 @item info common @r{[}@var{common-name}@r{]}
14953 This command prints the values contained in the Fortran @code{COMMON}
14954 block whose name is @var{common-name}. With no argument, the names of
14955 all @code{COMMON} blocks visible at the current program location are
14962 @cindex Pascal support in @value{GDBN}, limitations
14963 Debugging Pascal programs which use sets, subranges, file variables, or
14964 nested functions does not currently work. @value{GDBN} does not support
14965 entering expressions, printing values, or similar features using Pascal
14968 The Pascal-specific command @code{set print pascal_static-members}
14969 controls whether static members of Pascal objects are displayed.
14970 @xref{Print Settings, pascal_static-members}.
14973 @subsection Modula-2
14975 @cindex Modula-2, @value{GDBN} support
14977 The extensions made to @value{GDBN} to support Modula-2 only support
14978 output from the @sc{gnu} Modula-2 compiler (which is currently being
14979 developed). Other Modula-2 compilers are not currently supported, and
14980 attempting to debug executables produced by them is most likely
14981 to give an error as @value{GDBN} reads in the executable's symbol
14984 @cindex expressions in Modula-2
14986 * M2 Operators:: Built-in operators
14987 * Built-In Func/Proc:: Built-in functions and procedures
14988 * M2 Constants:: Modula-2 constants
14989 * M2 Types:: Modula-2 types
14990 * M2 Defaults:: Default settings for Modula-2
14991 * Deviations:: Deviations from standard Modula-2
14992 * M2 Checks:: Modula-2 type and range checks
14993 * M2 Scope:: The scope operators @code{::} and @code{.}
14994 * GDB/M2:: @value{GDBN} and Modula-2
14998 @subsubsection Operators
14999 @cindex Modula-2 operators
15001 Operators must be defined on values of specific types. For instance,
15002 @code{+} is defined on numbers, but not on structures. Operators are
15003 often defined on groups of types. For the purposes of Modula-2, the
15004 following definitions hold:
15009 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
15013 @emph{Character types} consist of @code{CHAR} and its subranges.
15016 @emph{Floating-point types} consist of @code{REAL}.
15019 @emph{Pointer types} consist of anything declared as @code{POINTER TO
15023 @emph{Scalar types} consist of all of the above.
15026 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
15029 @emph{Boolean types} consist of @code{BOOLEAN}.
15033 The following operators are supported, and appear in order of
15034 increasing precedence:
15038 Function argument or array index separator.
15041 Assignment. The value of @var{var} @code{:=} @var{value} is
15045 Less than, greater than on integral, floating-point, or enumerated
15049 Less than or equal to, greater than or equal to
15050 on integral, floating-point and enumerated types, or set inclusion on
15051 set types. Same precedence as @code{<}.
15053 @item =@r{, }<>@r{, }#
15054 Equality and two ways of expressing inequality, valid on scalar types.
15055 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
15056 available for inequality, since @code{#} conflicts with the script
15060 Set membership. Defined on set types and the types of their members.
15061 Same precedence as @code{<}.
15064 Boolean disjunction. Defined on boolean types.
15067 Boolean conjunction. Defined on boolean types.
15070 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
15073 Addition and subtraction on integral and floating-point types, or union
15074 and difference on set types.
15077 Multiplication on integral and floating-point types, or set intersection
15081 Division on floating-point types, or symmetric set difference on set
15082 types. Same precedence as @code{*}.
15085 Integer division and remainder. Defined on integral types. Same
15086 precedence as @code{*}.
15089 Negative. Defined on @code{INTEGER} and @code{REAL} data.
15092 Pointer dereferencing. Defined on pointer types.
15095 Boolean negation. Defined on boolean types. Same precedence as
15099 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
15100 precedence as @code{^}.
15103 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
15106 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
15110 @value{GDBN} and Modula-2 scope operators.
15114 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
15115 treats the use of the operator @code{IN}, or the use of operators
15116 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
15117 @code{<=}, and @code{>=} on sets as an error.
15121 @node Built-In Func/Proc
15122 @subsubsection Built-in Functions and Procedures
15123 @cindex Modula-2 built-ins
15125 Modula-2 also makes available several built-in procedures and functions.
15126 In describing these, the following metavariables are used:
15131 represents an @code{ARRAY} variable.
15134 represents a @code{CHAR} constant or variable.
15137 represents a variable or constant of integral type.
15140 represents an identifier that belongs to a set. Generally used in the
15141 same function with the metavariable @var{s}. The type of @var{s} should
15142 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
15145 represents a variable or constant of integral or floating-point type.
15148 represents a variable or constant of floating-point type.
15154 represents a variable.
15157 represents a variable or constant of one of many types. See the
15158 explanation of the function for details.
15161 All Modula-2 built-in procedures also return a result, described below.
15165 Returns the absolute value of @var{n}.
15168 If @var{c} is a lower case letter, it returns its upper case
15169 equivalent, otherwise it returns its argument.
15172 Returns the character whose ordinal value is @var{i}.
15175 Decrements the value in the variable @var{v} by one. Returns the new value.
15177 @item DEC(@var{v},@var{i})
15178 Decrements the value in the variable @var{v} by @var{i}. Returns the
15181 @item EXCL(@var{m},@var{s})
15182 Removes the element @var{m} from the set @var{s}. Returns the new
15185 @item FLOAT(@var{i})
15186 Returns the floating point equivalent of the integer @var{i}.
15188 @item HIGH(@var{a})
15189 Returns the index of the last member of @var{a}.
15192 Increments the value in the variable @var{v} by one. Returns the new value.
15194 @item INC(@var{v},@var{i})
15195 Increments the value in the variable @var{v} by @var{i}. Returns the
15198 @item INCL(@var{m},@var{s})
15199 Adds the element @var{m} to the set @var{s} if it is not already
15200 there. Returns the new set.
15203 Returns the maximum value of the type @var{t}.
15206 Returns the minimum value of the type @var{t}.
15209 Returns boolean TRUE if @var{i} is an odd number.
15212 Returns the ordinal value of its argument. For example, the ordinal
15213 value of a character is its @sc{ascii} value (on machines supporting
15214 the @sc{ascii} character set). The argument @var{x} must be of an
15215 ordered type, which include integral, character and enumerated types.
15217 @item SIZE(@var{x})
15218 Returns the size of its argument. The argument @var{x} can be a
15219 variable or a type.
15221 @item TRUNC(@var{r})
15222 Returns the integral part of @var{r}.
15224 @item TSIZE(@var{x})
15225 Returns the size of its argument. The argument @var{x} can be a
15226 variable or a type.
15228 @item VAL(@var{t},@var{i})
15229 Returns the member of the type @var{t} whose ordinal value is @var{i}.
15233 @emph{Warning:} Sets and their operations are not yet supported, so
15234 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
15238 @cindex Modula-2 constants
15240 @subsubsection Constants
15242 @value{GDBN} allows you to express the constants of Modula-2 in the following
15248 Integer constants are simply a sequence of digits. When used in an
15249 expression, a constant is interpreted to be type-compatible with the
15250 rest of the expression. Hexadecimal integers are specified by a
15251 trailing @samp{H}, and octal integers by a trailing @samp{B}.
15254 Floating point constants appear as a sequence of digits, followed by a
15255 decimal point and another sequence of digits. An optional exponent can
15256 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
15257 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
15258 digits of the floating point constant must be valid decimal (base 10)
15262 Character constants consist of a single character enclosed by a pair of
15263 like quotes, either single (@code{'}) or double (@code{"}). They may
15264 also be expressed by their ordinal value (their @sc{ascii} value, usually)
15265 followed by a @samp{C}.
15268 String constants consist of a sequence of characters enclosed by a
15269 pair of like quotes, either single (@code{'}) or double (@code{"}).
15270 Escape sequences in the style of C are also allowed. @xref{C
15271 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
15275 Enumerated constants consist of an enumerated identifier.
15278 Boolean constants consist of the identifiers @code{TRUE} and
15282 Pointer constants consist of integral values only.
15285 Set constants are not yet supported.
15289 @subsubsection Modula-2 Types
15290 @cindex Modula-2 types
15292 Currently @value{GDBN} can print the following data types in Modula-2
15293 syntax: array types, record types, set types, pointer types, procedure
15294 types, enumerated types, subrange types and base types. You can also
15295 print the contents of variables declared using these type.
15296 This section gives a number of simple source code examples together with
15297 sample @value{GDBN} sessions.
15299 The first example contains the following section of code:
15308 and you can request @value{GDBN} to interrogate the type and value of
15309 @code{r} and @code{s}.
15312 (@value{GDBP}) print s
15314 (@value{GDBP}) ptype s
15316 (@value{GDBP}) print r
15318 (@value{GDBP}) ptype r
15323 Likewise if your source code declares @code{s} as:
15327 s: SET ['A'..'Z'] ;
15331 then you may query the type of @code{s} by:
15334 (@value{GDBP}) ptype s
15335 type = SET ['A'..'Z']
15339 Note that at present you cannot interactively manipulate set
15340 expressions using the debugger.
15342 The following example shows how you might declare an array in Modula-2
15343 and how you can interact with @value{GDBN} to print its type and contents:
15347 s: ARRAY [-10..10] OF CHAR ;
15351 (@value{GDBP}) ptype s
15352 ARRAY [-10..10] OF CHAR
15355 Note that the array handling is not yet complete and although the type
15356 is printed correctly, expression handling still assumes that all
15357 arrays have a lower bound of zero and not @code{-10} as in the example
15360 Here are some more type related Modula-2 examples:
15364 colour = (blue, red, yellow, green) ;
15365 t = [blue..yellow] ;
15373 The @value{GDBN} interaction shows how you can query the data type
15374 and value of a variable.
15377 (@value{GDBP}) print s
15379 (@value{GDBP}) ptype t
15380 type = [blue..yellow]
15384 In this example a Modula-2 array is declared and its contents
15385 displayed. Observe that the contents are written in the same way as
15386 their @code{C} counterparts.
15390 s: ARRAY [1..5] OF CARDINAL ;
15396 (@value{GDBP}) print s
15397 $1 = @{1, 0, 0, 0, 0@}
15398 (@value{GDBP}) ptype s
15399 type = ARRAY [1..5] OF CARDINAL
15402 The Modula-2 language interface to @value{GDBN} also understands
15403 pointer types as shown in this example:
15407 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
15414 and you can request that @value{GDBN} describes the type of @code{s}.
15417 (@value{GDBP}) ptype s
15418 type = POINTER TO ARRAY [1..5] OF CARDINAL
15421 @value{GDBN} handles compound types as we can see in this example.
15422 Here we combine array types, record types, pointer types and subrange
15433 myarray = ARRAY myrange OF CARDINAL ;
15434 myrange = [-2..2] ;
15436 s: POINTER TO ARRAY myrange OF foo ;
15440 and you can ask @value{GDBN} to describe the type of @code{s} as shown
15444 (@value{GDBP}) ptype s
15445 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
15448 f3 : ARRAY [-2..2] OF CARDINAL;
15453 @subsubsection Modula-2 Defaults
15454 @cindex Modula-2 defaults
15456 If type and range checking are set automatically by @value{GDBN}, they
15457 both default to @code{on} whenever the working language changes to
15458 Modula-2. This happens regardless of whether you or @value{GDBN}
15459 selected the working language.
15461 If you allow @value{GDBN} to set the language automatically, then entering
15462 code compiled from a file whose name ends with @file{.mod} sets the
15463 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
15464 Infer the Source Language}, for further details.
15467 @subsubsection Deviations from Standard Modula-2
15468 @cindex Modula-2, deviations from
15470 A few changes have been made to make Modula-2 programs easier to debug.
15471 This is done primarily via loosening its type strictness:
15475 Unlike in standard Modula-2, pointer constants can be formed by
15476 integers. This allows you to modify pointer variables during
15477 debugging. (In standard Modula-2, the actual address contained in a
15478 pointer variable is hidden from you; it can only be modified
15479 through direct assignment to another pointer variable or expression that
15480 returned a pointer.)
15483 C escape sequences can be used in strings and characters to represent
15484 non-printable characters. @value{GDBN} prints out strings with these
15485 escape sequences embedded. Single non-printable characters are
15486 printed using the @samp{CHR(@var{nnn})} format.
15489 The assignment operator (@code{:=}) returns the value of its right-hand
15493 All built-in procedures both modify @emph{and} return their argument.
15497 @subsubsection Modula-2 Type and Range Checks
15498 @cindex Modula-2 checks
15501 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
15504 @c FIXME remove warning when type/range checks added
15506 @value{GDBN} considers two Modula-2 variables type equivalent if:
15510 They are of types that have been declared equivalent via a @code{TYPE
15511 @var{t1} = @var{t2}} statement
15514 They have been declared on the same line. (Note: This is true of the
15515 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
15518 As long as type checking is enabled, any attempt to combine variables
15519 whose types are not equivalent is an error.
15521 Range checking is done on all mathematical operations, assignment, array
15522 index bounds, and all built-in functions and procedures.
15525 @subsubsection The Scope Operators @code{::} and @code{.}
15527 @cindex @code{.}, Modula-2 scope operator
15528 @cindex colon, doubled as scope operator
15530 @vindex colon-colon@r{, in Modula-2}
15531 @c Info cannot handle :: but TeX can.
15534 @vindex ::@r{, in Modula-2}
15537 There are a few subtle differences between the Modula-2 scope operator
15538 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
15543 @var{module} . @var{id}
15544 @var{scope} :: @var{id}
15548 where @var{scope} is the name of a module or a procedure,
15549 @var{module} the name of a module, and @var{id} is any declared
15550 identifier within your program, except another module.
15552 Using the @code{::} operator makes @value{GDBN} search the scope
15553 specified by @var{scope} for the identifier @var{id}. If it is not
15554 found in the specified scope, then @value{GDBN} searches all scopes
15555 enclosing the one specified by @var{scope}.
15557 Using the @code{.} operator makes @value{GDBN} search the current scope for
15558 the identifier specified by @var{id} that was imported from the
15559 definition module specified by @var{module}. With this operator, it is
15560 an error if the identifier @var{id} was not imported from definition
15561 module @var{module}, or if @var{id} is not an identifier in
15565 @subsubsection @value{GDBN} and Modula-2
15567 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
15568 Five subcommands of @code{set print} and @code{show print} apply
15569 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
15570 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
15571 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
15572 analogue in Modula-2.
15574 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
15575 with any language, is not useful with Modula-2. Its
15576 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
15577 created in Modula-2 as they can in C or C@t{++}. However, because an
15578 address can be specified by an integral constant, the construct
15579 @samp{@{@var{type}@}@var{adrexp}} is still useful.
15581 @cindex @code{#} in Modula-2
15582 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
15583 interpreted as the beginning of a comment. Use @code{<>} instead.
15589 The extensions made to @value{GDBN} for Ada only support
15590 output from the @sc{gnu} Ada (GNAT) compiler.
15591 Other Ada compilers are not currently supported, and
15592 attempting to debug executables produced by them is most likely
15596 @cindex expressions in Ada
15598 * Ada Mode Intro:: General remarks on the Ada syntax
15599 and semantics supported by Ada mode
15601 * Omissions from Ada:: Restrictions on the Ada expression syntax.
15602 * Additions to Ada:: Extensions of the Ada expression syntax.
15603 * Stopping Before Main Program:: Debugging the program during elaboration.
15604 * Ada Exceptions:: Ada Exceptions
15605 * Ada Tasks:: Listing and setting breakpoints in tasks.
15606 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
15607 * Ravenscar Profile:: Tasking Support when using the Ravenscar
15609 * Ada Glitches:: Known peculiarities of Ada mode.
15612 @node Ada Mode Intro
15613 @subsubsection Introduction
15614 @cindex Ada mode, general
15616 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
15617 syntax, with some extensions.
15618 The philosophy behind the design of this subset is
15622 That @value{GDBN} should provide basic literals and access to operations for
15623 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
15624 leaving more sophisticated computations to subprograms written into the
15625 program (which therefore may be called from @value{GDBN}).
15628 That type safety and strict adherence to Ada language restrictions
15629 are not particularly important to the @value{GDBN} user.
15632 That brevity is important to the @value{GDBN} user.
15635 Thus, for brevity, the debugger acts as if all names declared in
15636 user-written packages are directly visible, even if they are not visible
15637 according to Ada rules, thus making it unnecessary to fully qualify most
15638 names with their packages, regardless of context. Where this causes
15639 ambiguity, @value{GDBN} asks the user's intent.
15641 The debugger will start in Ada mode if it detects an Ada main program.
15642 As for other languages, it will enter Ada mode when stopped in a program that
15643 was translated from an Ada source file.
15645 While in Ada mode, you may use `@t{--}' for comments. This is useful
15646 mostly for documenting command files. The standard @value{GDBN} comment
15647 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
15648 middle (to allow based literals).
15650 The debugger supports limited overloading. Given a subprogram call in which
15651 the function symbol has multiple definitions, it will use the number of
15652 actual parameters and some information about their types to attempt to narrow
15653 the set of definitions. It also makes very limited use of context, preferring
15654 procedures to functions in the context of the @code{call} command, and
15655 functions to procedures elsewhere.
15657 @node Omissions from Ada
15658 @subsubsection Omissions from Ada
15659 @cindex Ada, omissions from
15661 Here are the notable omissions from the subset:
15665 Only a subset of the attributes are supported:
15669 @t{'First}, @t{'Last}, and @t{'Length}
15670 on array objects (not on types and subtypes).
15673 @t{'Min} and @t{'Max}.
15676 @t{'Pos} and @t{'Val}.
15682 @t{'Range} on array objects (not subtypes), but only as the right
15683 operand of the membership (@code{in}) operator.
15686 @t{'Access}, @t{'Unchecked_Access}, and
15687 @t{'Unrestricted_Access} (a GNAT extension).
15695 @code{Characters.Latin_1} are not available and
15696 concatenation is not implemented. Thus, escape characters in strings are
15697 not currently available.
15700 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
15701 equality of representations. They will generally work correctly
15702 for strings and arrays whose elements have integer or enumeration types.
15703 They may not work correctly for arrays whose element
15704 types have user-defined equality, for arrays of real values
15705 (in particular, IEEE-conformant floating point, because of negative
15706 zeroes and NaNs), and for arrays whose elements contain unused bits with
15707 indeterminate values.
15710 The other component-by-component array operations (@code{and}, @code{or},
15711 @code{xor}, @code{not}, and relational tests other than equality)
15712 are not implemented.
15715 @cindex array aggregates (Ada)
15716 @cindex record aggregates (Ada)
15717 @cindex aggregates (Ada)
15718 There is limited support for array and record aggregates. They are
15719 permitted only on the right sides of assignments, as in these examples:
15722 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
15723 (@value{GDBP}) set An_Array := (1, others => 0)
15724 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
15725 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
15726 (@value{GDBP}) set A_Record := (1, "Peter", True);
15727 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
15731 discriminant's value by assigning an aggregate has an
15732 undefined effect if that discriminant is used within the record.
15733 However, you can first modify discriminants by directly assigning to
15734 them (which normally would not be allowed in Ada), and then performing an
15735 aggregate assignment. For example, given a variable @code{A_Rec}
15736 declared to have a type such as:
15739 type Rec (Len : Small_Integer := 0) is record
15741 Vals : IntArray (1 .. Len);
15745 you can assign a value with a different size of @code{Vals} with two
15749 (@value{GDBP}) set A_Rec.Len := 4
15750 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
15753 As this example also illustrates, @value{GDBN} is very loose about the usual
15754 rules concerning aggregates. You may leave out some of the
15755 components of an array or record aggregate (such as the @code{Len}
15756 component in the assignment to @code{A_Rec} above); they will retain their
15757 original values upon assignment. You may freely use dynamic values as
15758 indices in component associations. You may even use overlapping or
15759 redundant component associations, although which component values are
15760 assigned in such cases is not defined.
15763 Calls to dispatching subprograms are not implemented.
15766 The overloading algorithm is much more limited (i.e., less selective)
15767 than that of real Ada. It makes only limited use of the context in
15768 which a subexpression appears to resolve its meaning, and it is much
15769 looser in its rules for allowing type matches. As a result, some
15770 function calls will be ambiguous, and the user will be asked to choose
15771 the proper resolution.
15774 The @code{new} operator is not implemented.
15777 Entry calls are not implemented.
15780 Aside from printing, arithmetic operations on the native VAX floating-point
15781 formats are not supported.
15784 It is not possible to slice a packed array.
15787 The names @code{True} and @code{False}, when not part of a qualified name,
15788 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
15790 Should your program
15791 redefine these names in a package or procedure (at best a dubious practice),
15792 you will have to use fully qualified names to access their new definitions.
15795 @node Additions to Ada
15796 @subsubsection Additions to Ada
15797 @cindex Ada, deviations from
15799 As it does for other languages, @value{GDBN} makes certain generic
15800 extensions to Ada (@pxref{Expressions}):
15804 If the expression @var{E} is a variable residing in memory (typically
15805 a local variable or array element) and @var{N} is a positive integer,
15806 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
15807 @var{N}-1 adjacent variables following it in memory as an array. In
15808 Ada, this operator is generally not necessary, since its prime use is
15809 in displaying parts of an array, and slicing will usually do this in
15810 Ada. However, there are occasional uses when debugging programs in
15811 which certain debugging information has been optimized away.
15814 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
15815 appears in function or file @var{B}.'' When @var{B} is a file name,
15816 you must typically surround it in single quotes.
15819 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
15820 @var{type} that appears at address @var{addr}.''
15823 A name starting with @samp{$} is a convenience variable
15824 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
15827 In addition, @value{GDBN} provides a few other shortcuts and outright
15828 additions specific to Ada:
15832 The assignment statement is allowed as an expression, returning
15833 its right-hand operand as its value. Thus, you may enter
15836 (@value{GDBP}) set x := y + 3
15837 (@value{GDBP}) print A(tmp := y + 1)
15841 The semicolon is allowed as an ``operator,'' returning as its value
15842 the value of its right-hand operand.
15843 This allows, for example,
15844 complex conditional breaks:
15847 (@value{GDBP}) break f
15848 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
15852 Rather than use catenation and symbolic character names to introduce special
15853 characters into strings, one may instead use a special bracket notation,
15854 which is also used to print strings. A sequence of characters of the form
15855 @samp{["@var{XX}"]} within a string or character literal denotes the
15856 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
15857 sequence of characters @samp{["""]} also denotes a single quotation mark
15858 in strings. For example,
15860 "One line.["0a"]Next line.["0a"]"
15863 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
15867 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
15868 @t{'Max} is optional (and is ignored in any case). For example, it is valid
15872 (@value{GDBP}) print 'max(x, y)
15876 When printing arrays, @value{GDBN} uses positional notation when the
15877 array has a lower bound of 1, and uses a modified named notation otherwise.
15878 For example, a one-dimensional array of three integers with a lower bound
15879 of 3 might print as
15886 That is, in contrast to valid Ada, only the first component has a @code{=>}
15890 You may abbreviate attributes in expressions with any unique,
15891 multi-character subsequence of
15892 their names (an exact match gets preference).
15893 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
15894 in place of @t{a'length}.
15897 @cindex quoting Ada internal identifiers
15898 Since Ada is case-insensitive, the debugger normally maps identifiers you type
15899 to lower case. The GNAT compiler uses upper-case characters for
15900 some of its internal identifiers, which are normally of no interest to users.
15901 For the rare occasions when you actually have to look at them,
15902 enclose them in angle brackets to avoid the lower-case mapping.
15905 (@value{GDBP}) print <JMPBUF_SAVE>[0]
15909 Printing an object of class-wide type or dereferencing an
15910 access-to-class-wide value will display all the components of the object's
15911 specific type (as indicated by its run-time tag). Likewise, component
15912 selection on such a value will operate on the specific type of the
15917 @node Stopping Before Main Program
15918 @subsubsection Stopping at the Very Beginning
15920 @cindex breakpointing Ada elaboration code
15921 It is sometimes necessary to debug the program during elaboration, and
15922 before reaching the main procedure.
15923 As defined in the Ada Reference
15924 Manual, the elaboration code is invoked from a procedure called
15925 @code{adainit}. To run your program up to the beginning of
15926 elaboration, simply use the following two commands:
15927 @code{tbreak adainit} and @code{run}.
15929 @node Ada Exceptions
15930 @subsubsection Ada Exceptions
15932 A command is provided to list all Ada exceptions:
15935 @kindex info exceptions
15936 @item info exceptions
15937 @itemx info exceptions @var{regexp}
15938 The @code{info exceptions} command allows you to list all Ada exceptions
15939 defined within the program being debugged, as well as their addresses.
15940 With a regular expression, @var{regexp}, as argument, only those exceptions
15941 whose names match @var{regexp} are listed.
15944 Below is a small example, showing how the command can be used, first
15945 without argument, and next with a regular expression passed as an
15949 (@value{GDBP}) info exceptions
15950 All defined Ada exceptions:
15951 constraint_error: 0x613da0
15952 program_error: 0x613d20
15953 storage_error: 0x613ce0
15954 tasking_error: 0x613ca0
15955 const.aint_global_e: 0x613b00
15956 (@value{GDBP}) info exceptions const.aint
15957 All Ada exceptions matching regular expression "const.aint":
15958 constraint_error: 0x613da0
15959 const.aint_global_e: 0x613b00
15962 It is also possible to ask @value{GDBN} to stop your program's execution
15963 when an exception is raised. For more details, see @ref{Set Catchpoints}.
15966 @subsubsection Extensions for Ada Tasks
15967 @cindex Ada, tasking
15969 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
15970 @value{GDBN} provides the following task-related commands:
15975 This command shows a list of current Ada tasks, as in the following example:
15982 (@value{GDBP}) info tasks
15983 ID TID P-ID Pri State Name
15984 1 8088000 0 15 Child Activation Wait main_task
15985 2 80a4000 1 15 Accept Statement b
15986 3 809a800 1 15 Child Activation Wait a
15987 * 4 80ae800 3 15 Runnable c
15992 In this listing, the asterisk before the last task indicates it to be the
15993 task currently being inspected.
15997 Represents @value{GDBN}'s internal task number.
16003 The parent's task ID (@value{GDBN}'s internal task number).
16006 The base priority of the task.
16009 Current state of the task.
16013 The task has been created but has not been activated. It cannot be
16017 The task is not blocked for any reason known to Ada. (It may be waiting
16018 for a mutex, though.) It is conceptually "executing" in normal mode.
16021 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
16022 that were waiting on terminate alternatives have been awakened and have
16023 terminated themselves.
16025 @item Child Activation Wait
16026 The task is waiting for created tasks to complete activation.
16028 @item Accept Statement
16029 The task is waiting on an accept or selective wait statement.
16031 @item Waiting on entry call
16032 The task is waiting on an entry call.
16034 @item Async Select Wait
16035 The task is waiting to start the abortable part of an asynchronous
16039 The task is waiting on a select statement with only a delay
16042 @item Child Termination Wait
16043 The task is sleeping having completed a master within itself, and is
16044 waiting for the tasks dependent on that master to become terminated or
16045 waiting on a terminate Phase.
16047 @item Wait Child in Term Alt
16048 The task is sleeping waiting for tasks on terminate alternatives to
16049 finish terminating.
16051 @item Accepting RV with @var{taskno}
16052 The task is accepting a rendez-vous with the task @var{taskno}.
16056 Name of the task in the program.
16060 @kindex info task @var{taskno}
16061 @item info task @var{taskno}
16062 This command shows detailled informations on the specified task, as in
16063 the following example:
16068 (@value{GDBP}) info tasks
16069 ID TID P-ID Pri State Name
16070 1 8077880 0 15 Child Activation Wait main_task
16071 * 2 807c468 1 15 Runnable task_1
16072 (@value{GDBP}) info task 2
16073 Ada Task: 0x807c468
16076 Parent: 1 (main_task)
16082 @kindex task@r{ (Ada)}
16083 @cindex current Ada task ID
16084 This command prints the ID of the current task.
16090 (@value{GDBP}) info tasks
16091 ID TID P-ID Pri State Name
16092 1 8077870 0 15 Child Activation Wait main_task
16093 * 2 807c458 1 15 Runnable t
16094 (@value{GDBP}) task
16095 [Current task is 2]
16098 @item task @var{taskno}
16099 @cindex Ada task switching
16100 This command is like the @code{thread @var{threadno}}
16101 command (@pxref{Threads}). It switches the context of debugging
16102 from the current task to the given task.
16108 (@value{GDBP}) info tasks
16109 ID TID P-ID Pri State Name
16110 1 8077870 0 15 Child Activation Wait main_task
16111 * 2 807c458 1 15 Runnable t
16112 (@value{GDBP}) task 1
16113 [Switching to task 1]
16114 #0 0x8067726 in pthread_cond_wait ()
16116 #0 0x8067726 in pthread_cond_wait ()
16117 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
16118 #2 0x805cb63 in system.task_primitives.operations.sleep ()
16119 #3 0x806153e in system.tasking.stages.activate_tasks ()
16120 #4 0x804aacc in un () at un.adb:5
16123 @item break @var{location} task @var{taskno}
16124 @itemx break @var{location} task @var{taskno} if @dots{}
16125 @cindex breakpoints and tasks, in Ada
16126 @cindex task breakpoints, in Ada
16127 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
16128 These commands are like the @code{break @dots{} thread @dots{}}
16129 command (@pxref{Thread Stops}). The
16130 @var{location} argument specifies source lines, as described
16131 in @ref{Specify Location}.
16133 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
16134 to specify that you only want @value{GDBN} to stop the program when a
16135 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
16136 numeric task identifiers assigned by @value{GDBN}, shown in the first
16137 column of the @samp{info tasks} display.
16139 If you do not specify @samp{task @var{taskno}} when you set a
16140 breakpoint, the breakpoint applies to @emph{all} tasks of your
16143 You can use the @code{task} qualifier on conditional breakpoints as
16144 well; in this case, place @samp{task @var{taskno}} before the
16145 breakpoint condition (before the @code{if}).
16153 (@value{GDBP}) info tasks
16154 ID TID P-ID Pri State Name
16155 1 140022020 0 15 Child Activation Wait main_task
16156 2 140045060 1 15 Accept/Select Wait t2
16157 3 140044840 1 15 Runnable t1
16158 * 4 140056040 1 15 Runnable t3
16159 (@value{GDBP}) b 15 task 2
16160 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
16161 (@value{GDBP}) cont
16166 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
16168 (@value{GDBP}) info tasks
16169 ID TID P-ID Pri State Name
16170 1 140022020 0 15 Child Activation Wait main_task
16171 * 2 140045060 1 15 Runnable t2
16172 3 140044840 1 15 Runnable t1
16173 4 140056040 1 15 Delay Sleep t3
16177 @node Ada Tasks and Core Files
16178 @subsubsection Tasking Support when Debugging Core Files
16179 @cindex Ada tasking and core file debugging
16181 When inspecting a core file, as opposed to debugging a live program,
16182 tasking support may be limited or even unavailable, depending on
16183 the platform being used.
16184 For instance, on x86-linux, the list of tasks is available, but task
16185 switching is not supported.
16187 On certain platforms, the debugger needs to perform some
16188 memory writes in order to provide Ada tasking support. When inspecting
16189 a core file, this means that the core file must be opened with read-write
16190 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
16191 Under these circumstances, you should make a backup copy of the core
16192 file before inspecting it with @value{GDBN}.
16194 @node Ravenscar Profile
16195 @subsubsection Tasking Support when using the Ravenscar Profile
16196 @cindex Ravenscar Profile
16198 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
16199 specifically designed for systems with safety-critical real-time
16203 @kindex set ravenscar task-switching on
16204 @cindex task switching with program using Ravenscar Profile
16205 @item set ravenscar task-switching on
16206 Allows task switching when debugging a program that uses the Ravenscar
16207 Profile. This is the default.
16209 @kindex set ravenscar task-switching off
16210 @item set ravenscar task-switching off
16211 Turn off task switching when debugging a program that uses the Ravenscar
16212 Profile. This is mostly intended to disable the code that adds support
16213 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
16214 the Ravenscar runtime is preventing @value{GDBN} from working properly.
16215 To be effective, this command should be run before the program is started.
16217 @kindex show ravenscar task-switching
16218 @item show ravenscar task-switching
16219 Show whether it is possible to switch from task to task in a program
16220 using the Ravenscar Profile.
16225 @subsubsection Known Peculiarities of Ada Mode
16226 @cindex Ada, problems
16228 Besides the omissions listed previously (@pxref{Omissions from Ada}),
16229 we know of several problems with and limitations of Ada mode in
16231 some of which will be fixed with planned future releases of the debugger
16232 and the GNU Ada compiler.
16236 Static constants that the compiler chooses not to materialize as objects in
16237 storage are invisible to the debugger.
16240 Named parameter associations in function argument lists are ignored (the
16241 argument lists are treated as positional).
16244 Many useful library packages are currently invisible to the debugger.
16247 Fixed-point arithmetic, conversions, input, and output is carried out using
16248 floating-point arithmetic, and may give results that only approximate those on
16252 The GNAT compiler never generates the prefix @code{Standard} for any of
16253 the standard symbols defined by the Ada language. @value{GDBN} knows about
16254 this: it will strip the prefix from names when you use it, and will never
16255 look for a name you have so qualified among local symbols, nor match against
16256 symbols in other packages or subprograms. If you have
16257 defined entities anywhere in your program other than parameters and
16258 local variables whose simple names match names in @code{Standard},
16259 GNAT's lack of qualification here can cause confusion. When this happens,
16260 you can usually resolve the confusion
16261 by qualifying the problematic names with package
16262 @code{Standard} explicitly.
16265 Older versions of the compiler sometimes generate erroneous debugging
16266 information, resulting in the debugger incorrectly printing the value
16267 of affected entities. In some cases, the debugger is able to work
16268 around an issue automatically. In other cases, the debugger is able
16269 to work around the issue, but the work-around has to be specifically
16272 @kindex set ada trust-PAD-over-XVS
16273 @kindex show ada trust-PAD-over-XVS
16276 @item set ada trust-PAD-over-XVS on
16277 Configure GDB to strictly follow the GNAT encoding when computing the
16278 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
16279 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
16280 a complete description of the encoding used by the GNAT compiler).
16281 This is the default.
16283 @item set ada trust-PAD-over-XVS off
16284 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
16285 sometimes prints the wrong value for certain entities, changing @code{ada
16286 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
16287 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
16288 @code{off}, but this incurs a slight performance penalty, so it is
16289 recommended to leave this setting to @code{on} unless necessary.
16293 @cindex GNAT descriptive types
16294 @cindex GNAT encoding
16295 Internally, the debugger also relies on the compiler following a number
16296 of conventions known as the @samp{GNAT Encoding}, all documented in
16297 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
16298 how the debugging information should be generated for certain types.
16299 In particular, this convention makes use of @dfn{descriptive types},
16300 which are artificial types generated purely to help the debugger.
16302 These encodings were defined at a time when the debugging information
16303 format used was not powerful enough to describe some of the more complex
16304 types available in Ada. Since DWARF allows us to express nearly all
16305 Ada features, the long-term goal is to slowly replace these descriptive
16306 types by their pure DWARF equivalent. To facilitate that transition,
16307 a new maintenance option is available to force the debugger to ignore
16308 those descriptive types. It allows the user to quickly evaluate how
16309 well @value{GDBN} works without them.
16313 @kindex maint ada set ignore-descriptive-types
16314 @item maintenance ada set ignore-descriptive-types [on|off]
16315 Control whether the debugger should ignore descriptive types.
16316 The default is not to ignore descriptives types (@code{off}).
16318 @kindex maint ada show ignore-descriptive-types
16319 @item maintenance ada show ignore-descriptive-types
16320 Show if descriptive types are ignored by @value{GDBN}.
16324 @node Unsupported Languages
16325 @section Unsupported Languages
16327 @cindex unsupported languages
16328 @cindex minimal language
16329 In addition to the other fully-supported programming languages,
16330 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
16331 It does not represent a real programming language, but provides a set
16332 of capabilities close to what the C or assembly languages provide.
16333 This should allow most simple operations to be performed while debugging
16334 an application that uses a language currently not supported by @value{GDBN}.
16336 If the language is set to @code{auto}, @value{GDBN} will automatically
16337 select this language if the current frame corresponds to an unsupported
16341 @chapter Examining the Symbol Table
16343 The commands described in this chapter allow you to inquire about the
16344 symbols (names of variables, functions and types) defined in your
16345 program. This information is inherent in the text of your program and
16346 does not change as your program executes. @value{GDBN} finds it in your
16347 program's symbol table, in the file indicated when you started @value{GDBN}
16348 (@pxref{File Options, ,Choosing Files}), or by one of the
16349 file-management commands (@pxref{Files, ,Commands to Specify Files}).
16351 @cindex symbol names
16352 @cindex names of symbols
16353 @cindex quoting names
16354 Occasionally, you may need to refer to symbols that contain unusual
16355 characters, which @value{GDBN} ordinarily treats as word delimiters. The
16356 most frequent case is in referring to static variables in other
16357 source files (@pxref{Variables,,Program Variables}). File names
16358 are recorded in object files as debugging symbols, but @value{GDBN} would
16359 ordinarily parse a typical file name, like @file{foo.c}, as the three words
16360 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
16361 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
16368 looks up the value of @code{x} in the scope of the file @file{foo.c}.
16371 @cindex case-insensitive symbol names
16372 @cindex case sensitivity in symbol names
16373 @kindex set case-sensitive
16374 @item set case-sensitive on
16375 @itemx set case-sensitive off
16376 @itemx set case-sensitive auto
16377 Normally, when @value{GDBN} looks up symbols, it matches their names
16378 with case sensitivity determined by the current source language.
16379 Occasionally, you may wish to control that. The command @code{set
16380 case-sensitive} lets you do that by specifying @code{on} for
16381 case-sensitive matches or @code{off} for case-insensitive ones. If
16382 you specify @code{auto}, case sensitivity is reset to the default
16383 suitable for the source language. The default is case-sensitive
16384 matches for all languages except for Fortran, for which the default is
16385 case-insensitive matches.
16387 @kindex show case-sensitive
16388 @item show case-sensitive
16389 This command shows the current setting of case sensitivity for symbols
16392 @kindex set print type methods
16393 @item set print type methods
16394 @itemx set print type methods on
16395 @itemx set print type methods off
16396 Normally, when @value{GDBN} prints a class, it displays any methods
16397 declared in that class. You can control this behavior either by
16398 passing the appropriate flag to @code{ptype}, or using @command{set
16399 print type methods}. Specifying @code{on} will cause @value{GDBN} to
16400 display the methods; this is the default. Specifying @code{off} will
16401 cause @value{GDBN} to omit the methods.
16403 @kindex show print type methods
16404 @item show print type methods
16405 This command shows the current setting of method display when printing
16408 @kindex set print type typedefs
16409 @item set print type typedefs
16410 @itemx set print type typedefs on
16411 @itemx set print type typedefs off
16413 Normally, when @value{GDBN} prints a class, it displays any typedefs
16414 defined in that class. You can control this behavior either by
16415 passing the appropriate flag to @code{ptype}, or using @command{set
16416 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
16417 display the typedef definitions; this is the default. Specifying
16418 @code{off} will cause @value{GDBN} to omit the typedef definitions.
16419 Note that this controls whether the typedef definition itself is
16420 printed, not whether typedef names are substituted when printing other
16423 @kindex show print type typedefs
16424 @item show print type typedefs
16425 This command shows the current setting of typedef display when
16428 @kindex info address
16429 @cindex address of a symbol
16430 @item info address @var{symbol}
16431 Describe where the data for @var{symbol} is stored. For a register
16432 variable, this says which register it is kept in. For a non-register
16433 local variable, this prints the stack-frame offset at which the variable
16436 Note the contrast with @samp{print &@var{symbol}}, which does not work
16437 at all for a register variable, and for a stack local variable prints
16438 the exact address of the current instantiation of the variable.
16440 @kindex info symbol
16441 @cindex symbol from address
16442 @cindex closest symbol and offset for an address
16443 @item info symbol @var{addr}
16444 Print the name of a symbol which is stored at the address @var{addr}.
16445 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
16446 nearest symbol and an offset from it:
16449 (@value{GDBP}) info symbol 0x54320
16450 _initialize_vx + 396 in section .text
16454 This is the opposite of the @code{info address} command. You can use
16455 it to find out the name of a variable or a function given its address.
16457 For dynamically linked executables, the name of executable or shared
16458 library containing the symbol is also printed:
16461 (@value{GDBP}) info symbol 0x400225
16462 _start + 5 in section .text of /tmp/a.out
16463 (@value{GDBP}) info symbol 0x2aaaac2811cf
16464 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
16469 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
16470 Demangle @var{name}.
16471 If @var{language} is provided it is the name of the language to demangle
16472 @var{name} in. Otherwise @var{name} is demangled in the current language.
16474 The @samp{--} option specifies the end of options,
16475 and is useful when @var{name} begins with a dash.
16477 The parameter @code{demangle-style} specifies how to interpret the kind
16478 of mangling used. @xref{Print Settings}.
16481 @item whatis[/@var{flags}] [@var{arg}]
16482 Print the data type of @var{arg}, which can be either an expression
16483 or a name of a data type. With no argument, print the data type of
16484 @code{$}, the last value in the value history.
16486 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
16487 is not actually evaluated, and any side-effecting operations (such as
16488 assignments or function calls) inside it do not take place.
16490 If @var{arg} is a variable or an expression, @code{whatis} prints its
16491 literal type as it is used in the source code. If the type was
16492 defined using a @code{typedef}, @code{whatis} will @emph{not} print
16493 the data type underlying the @code{typedef}. If the type of the
16494 variable or the expression is a compound data type, such as
16495 @code{struct} or @code{class}, @code{whatis} never prints their
16496 fields or methods. It just prints the @code{struct}/@code{class}
16497 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
16498 such a compound data type, use @code{ptype}.
16500 If @var{arg} is a type name that was defined using @code{typedef},
16501 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
16502 Unrolling means that @code{whatis} will show the underlying type used
16503 in the @code{typedef} declaration of @var{arg}. However, if that
16504 underlying type is also a @code{typedef}, @code{whatis} will not
16507 For C code, the type names may also have the form @samp{class
16508 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
16509 @var{union-tag}} or @samp{enum @var{enum-tag}}.
16511 @var{flags} can be used to modify how the type is displayed.
16512 Available flags are:
16516 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
16517 parameters and typedefs defined in a class when printing the class'
16518 members. The @code{/r} flag disables this.
16521 Do not print methods defined in the class.
16524 Print methods defined in the class. This is the default, but the flag
16525 exists in case you change the default with @command{set print type methods}.
16528 Do not print typedefs defined in the class. Note that this controls
16529 whether the typedef definition itself is printed, not whether typedef
16530 names are substituted when printing other types.
16533 Print typedefs defined in the class. This is the default, but the flag
16534 exists in case you change the default with @command{set print type typedefs}.
16538 @item ptype[/@var{flags}] [@var{arg}]
16539 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
16540 detailed description of the type, instead of just the name of the type.
16541 @xref{Expressions, ,Expressions}.
16543 Contrary to @code{whatis}, @code{ptype} always unrolls any
16544 @code{typedef}s in its argument declaration, whether the argument is
16545 a variable, expression, or a data type. This means that @code{ptype}
16546 of a variable or an expression will not print literally its type as
16547 present in the source code---use @code{whatis} for that. @code{typedef}s at
16548 the pointer or reference targets are also unrolled. Only @code{typedef}s of
16549 fields, methods and inner @code{class typedef}s of @code{struct}s,
16550 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
16552 For example, for this variable declaration:
16555 typedef double real_t;
16556 struct complex @{ real_t real; double imag; @};
16557 typedef struct complex complex_t;
16559 real_t *real_pointer_var;
16563 the two commands give this output:
16567 (@value{GDBP}) whatis var
16569 (@value{GDBP}) ptype var
16570 type = struct complex @{
16574 (@value{GDBP}) whatis complex_t
16575 type = struct complex
16576 (@value{GDBP}) whatis struct complex
16577 type = struct complex
16578 (@value{GDBP}) ptype struct complex
16579 type = struct complex @{
16583 (@value{GDBP}) whatis real_pointer_var
16585 (@value{GDBP}) ptype real_pointer_var
16591 As with @code{whatis}, using @code{ptype} without an argument refers to
16592 the type of @code{$}, the last value in the value history.
16594 @cindex incomplete type
16595 Sometimes, programs use opaque data types or incomplete specifications
16596 of complex data structure. If the debug information included in the
16597 program does not allow @value{GDBN} to display a full declaration of
16598 the data type, it will say @samp{<incomplete type>}. For example,
16599 given these declarations:
16603 struct foo *fooptr;
16607 but no definition for @code{struct foo} itself, @value{GDBN} will say:
16610 (@value{GDBP}) ptype foo
16611 $1 = <incomplete type>
16615 ``Incomplete type'' is C terminology for data types that are not
16616 completely specified.
16619 @item info types @var{regexp}
16621 Print a brief description of all types whose names match the regular
16622 expression @var{regexp} (or all types in your program, if you supply
16623 no argument). Each complete typename is matched as though it were a
16624 complete line; thus, @samp{i type value} gives information on all
16625 types in your program whose names include the string @code{value}, but
16626 @samp{i type ^value$} gives information only on types whose complete
16627 name is @code{value}.
16629 This command differs from @code{ptype} in two ways: first, like
16630 @code{whatis}, it does not print a detailed description; second, it
16631 lists all source files where a type is defined.
16633 @kindex info type-printers
16634 @item info type-printers
16635 Versions of @value{GDBN} that ship with Python scripting enabled may
16636 have ``type printers'' available. When using @command{ptype} or
16637 @command{whatis}, these printers are consulted when the name of a type
16638 is needed. @xref{Type Printing API}, for more information on writing
16641 @code{info type-printers} displays all the available type printers.
16643 @kindex enable type-printer
16644 @kindex disable type-printer
16645 @item enable type-printer @var{name}@dots{}
16646 @item disable type-printer @var{name}@dots{}
16647 These commands can be used to enable or disable type printers.
16650 @cindex local variables
16651 @item info scope @var{location}
16652 List all the variables local to a particular scope. This command
16653 accepts a @var{location} argument---a function name, a source line, or
16654 an address preceded by a @samp{*}, and prints all the variables local
16655 to the scope defined by that location. (@xref{Specify Location}, for
16656 details about supported forms of @var{location}.) For example:
16659 (@value{GDBP}) @b{info scope command_line_handler}
16660 Scope for command_line_handler:
16661 Symbol rl is an argument at stack/frame offset 8, length 4.
16662 Symbol linebuffer is in static storage at address 0x150a18, length 4.
16663 Symbol linelength is in static storage at address 0x150a1c, length 4.
16664 Symbol p is a local variable in register $esi, length 4.
16665 Symbol p1 is a local variable in register $ebx, length 4.
16666 Symbol nline is a local variable in register $edx, length 4.
16667 Symbol repeat is a local variable at frame offset -8, length 4.
16671 This command is especially useful for determining what data to collect
16672 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
16675 @kindex info source
16677 Show information about the current source file---that is, the source file for
16678 the function containing the current point of execution:
16681 the name of the source file, and the directory containing it,
16683 the directory it was compiled in,
16685 its length, in lines,
16687 which programming language it is written in,
16689 if the debug information provides it, the program that compiled the file
16690 (which may include, e.g., the compiler version and command line arguments),
16692 whether the executable includes debugging information for that file, and
16693 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
16695 whether the debugging information includes information about
16696 preprocessor macros.
16700 @kindex info sources
16702 Print the names of all source files in your program for which there is
16703 debugging information, organized into two lists: files whose symbols
16704 have already been read, and files whose symbols will be read when needed.
16706 @kindex info functions
16707 @item info functions
16708 Print the names and data types of all defined functions.
16710 @item info functions @var{regexp}
16711 Print the names and data types of all defined functions
16712 whose names contain a match for regular expression @var{regexp}.
16713 Thus, @samp{info fun step} finds all functions whose names
16714 include @code{step}; @samp{info fun ^step} finds those whose names
16715 start with @code{step}. If a function name contains characters
16716 that conflict with the regular expression language (e.g.@:
16717 @samp{operator*()}), they may be quoted with a backslash.
16719 @kindex info variables
16720 @item info variables
16721 Print the names and data types of all variables that are defined
16722 outside of functions (i.e.@: excluding local variables).
16724 @item info variables @var{regexp}
16725 Print the names and data types of all variables (except for local
16726 variables) whose names contain a match for regular expression
16729 @kindex info classes
16730 @cindex Objective-C, classes and selectors
16732 @itemx info classes @var{regexp}
16733 Display all Objective-C classes in your program, or
16734 (with the @var{regexp} argument) all those matching a particular regular
16737 @kindex info selectors
16738 @item info selectors
16739 @itemx info selectors @var{regexp}
16740 Display all Objective-C selectors in your program, or
16741 (with the @var{regexp} argument) all those matching a particular regular
16745 This was never implemented.
16746 @kindex info methods
16748 @itemx info methods @var{regexp}
16749 The @code{info methods} command permits the user to examine all defined
16750 methods within C@t{++} program, or (with the @var{regexp} argument) a
16751 specific set of methods found in the various C@t{++} classes. Many
16752 C@t{++} classes provide a large number of methods. Thus, the output
16753 from the @code{ptype} command can be overwhelming and hard to use. The
16754 @code{info-methods} command filters the methods, printing only those
16755 which match the regular-expression @var{regexp}.
16758 @cindex opaque data types
16759 @kindex set opaque-type-resolution
16760 @item set opaque-type-resolution on
16761 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
16762 declared as a pointer to a @code{struct}, @code{class}, or
16763 @code{union}---for example, @code{struct MyType *}---that is used in one
16764 source file although the full declaration of @code{struct MyType} is in
16765 another source file. The default is on.
16767 A change in the setting of this subcommand will not take effect until
16768 the next time symbols for a file are loaded.
16770 @item set opaque-type-resolution off
16771 Tell @value{GDBN} not to resolve opaque types. In this case, the type
16772 is printed as follows:
16774 @{<no data fields>@}
16777 @kindex show opaque-type-resolution
16778 @item show opaque-type-resolution
16779 Show whether opaque types are resolved or not.
16781 @kindex set print symbol-loading
16782 @cindex print messages when symbols are loaded
16783 @item set print symbol-loading
16784 @itemx set print symbol-loading full
16785 @itemx set print symbol-loading brief
16786 @itemx set print symbol-loading off
16787 The @code{set print symbol-loading} command allows you to control the
16788 printing of messages when @value{GDBN} loads symbol information.
16789 By default a message is printed for the executable and one for each
16790 shared library, and normally this is what you want. However, when
16791 debugging apps with large numbers of shared libraries these messages
16793 When set to @code{brief} a message is printed for each executable,
16794 and when @value{GDBN} loads a collection of shared libraries at once
16795 it will only print one message regardless of the number of shared
16796 libraries. When set to @code{off} no messages are printed.
16798 @kindex show print symbol-loading
16799 @item show print symbol-loading
16800 Show whether messages will be printed when a @value{GDBN} command
16801 entered from the keyboard causes symbol information to be loaded.
16803 @kindex maint print symbols
16804 @cindex symbol dump
16805 @kindex maint print psymbols
16806 @cindex partial symbol dump
16807 @kindex maint print msymbols
16808 @cindex minimal symbol dump
16809 @item maint print symbols @var{filename}
16810 @itemx maint print psymbols @var{filename}
16811 @itemx maint print msymbols @var{filename}
16812 Write a dump of debugging symbol data into the file @var{filename}.
16813 These commands are used to debug the @value{GDBN} symbol-reading code. Only
16814 symbols with debugging data are included. If you use @samp{maint print
16815 symbols}, @value{GDBN} includes all the symbols for which it has already
16816 collected full details: that is, @var{filename} reflects symbols for
16817 only those files whose symbols @value{GDBN} has read. You can use the
16818 command @code{info sources} to find out which files these are. If you
16819 use @samp{maint print psymbols} instead, the dump shows information about
16820 symbols that @value{GDBN} only knows partially---that is, symbols defined in
16821 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
16822 @samp{maint print msymbols} dumps just the minimal symbol information
16823 required for each object file from which @value{GDBN} has read some symbols.
16824 @xref{Files, ,Commands to Specify Files}, for a discussion of how
16825 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
16827 @kindex maint info symtabs
16828 @kindex maint info psymtabs
16829 @cindex listing @value{GDBN}'s internal symbol tables
16830 @cindex symbol tables, listing @value{GDBN}'s internal
16831 @cindex full symbol tables, listing @value{GDBN}'s internal
16832 @cindex partial symbol tables, listing @value{GDBN}'s internal
16833 @item maint info symtabs @r{[} @var{regexp} @r{]}
16834 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
16836 List the @code{struct symtab} or @code{struct partial_symtab}
16837 structures whose names match @var{regexp}. If @var{regexp} is not
16838 given, list them all. The output includes expressions which you can
16839 copy into a @value{GDBN} debugging this one to examine a particular
16840 structure in more detail. For example:
16843 (@value{GDBP}) maint info psymtabs dwarf2read
16844 @{ objfile /home/gnu/build/gdb/gdb
16845 ((struct objfile *) 0x82e69d0)
16846 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
16847 ((struct partial_symtab *) 0x8474b10)
16850 text addresses 0x814d3c8 -- 0x8158074
16851 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
16852 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
16853 dependencies (none)
16856 (@value{GDBP}) maint info symtabs
16860 We see that there is one partial symbol table whose filename contains
16861 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
16862 and we see that @value{GDBN} has not read in any symtabs yet at all.
16863 If we set a breakpoint on a function, that will cause @value{GDBN} to
16864 read the symtab for the compilation unit containing that function:
16867 (@value{GDBP}) break dwarf2_psymtab_to_symtab
16868 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
16870 (@value{GDBP}) maint info symtabs
16871 @{ objfile /home/gnu/build/gdb/gdb
16872 ((struct objfile *) 0x82e69d0)
16873 @{ symtab /home/gnu/src/gdb/dwarf2read.c
16874 ((struct symtab *) 0x86c1f38)
16877 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
16878 linetable ((struct linetable *) 0x8370fa0)
16879 debugformat DWARF 2
16885 @kindex maint set symbol-cache-size
16886 @cindex symbol cache size
16887 @item maint set symbol-cache-size @var{size}
16888 Set the size of the symbol cache to @var{size}.
16889 The default size is intended to be good enough for debugging
16890 most applications. This option exists to allow for experimenting
16891 with different sizes.
16893 @kindex maint show symbol-cache-size
16894 @item maint show symbol-cache-size
16895 Show the size of the symbol cache.
16897 @kindex maint print symbol-cache
16898 @cindex symbol cache, printing its contents
16899 @item maint print symbol-cache
16900 Print the contents of the symbol cache.
16901 This is useful when debugging symbol cache issues.
16903 @kindex maint print symbol-cache-statistics
16904 @cindex symbol cache, printing usage statistics
16905 @item maint print symbol-cache-statistics
16906 Print symbol cache usage statistics.
16907 This helps determine how well the cache is being utilized.
16909 @kindex maint flush-symbol-cache
16910 @cindex symbol cache, flushing
16911 @item maint flush-symbol-cache
16912 Flush the contents of the symbol cache, all entries are removed.
16913 This command is useful when debugging the symbol cache.
16914 It is also useful when collecting performance data.
16919 @chapter Altering Execution
16921 Once you think you have found an error in your program, you might want to
16922 find out for certain whether correcting the apparent error would lead to
16923 correct results in the rest of the run. You can find the answer by
16924 experiment, using the @value{GDBN} features for altering execution of the
16927 For example, you can store new values into variables or memory
16928 locations, give your program a signal, restart it at a different
16929 address, or even return prematurely from a function.
16932 * Assignment:: Assignment to variables
16933 * Jumping:: Continuing at a different address
16934 * Signaling:: Giving your program a signal
16935 * Returning:: Returning from a function
16936 * Calling:: Calling your program's functions
16937 * Patching:: Patching your program
16938 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
16942 @section Assignment to Variables
16945 @cindex setting variables
16946 To alter the value of a variable, evaluate an assignment expression.
16947 @xref{Expressions, ,Expressions}. For example,
16954 stores the value 4 into the variable @code{x}, and then prints the
16955 value of the assignment expression (which is 4).
16956 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
16957 information on operators in supported languages.
16959 @kindex set variable
16960 @cindex variables, setting
16961 If you are not interested in seeing the value of the assignment, use the
16962 @code{set} command instead of the @code{print} command. @code{set} is
16963 really the same as @code{print} except that the expression's value is
16964 not printed and is not put in the value history (@pxref{Value History,
16965 ,Value History}). The expression is evaluated only for its effects.
16967 If the beginning of the argument string of the @code{set} command
16968 appears identical to a @code{set} subcommand, use the @code{set
16969 variable} command instead of just @code{set}. This command is identical
16970 to @code{set} except for its lack of subcommands. For example, if your
16971 program has a variable @code{width}, you get an error if you try to set
16972 a new value with just @samp{set width=13}, because @value{GDBN} has the
16973 command @code{set width}:
16976 (@value{GDBP}) whatis width
16978 (@value{GDBP}) p width
16980 (@value{GDBP}) set width=47
16981 Invalid syntax in expression.
16985 The invalid expression, of course, is @samp{=47}. In
16986 order to actually set the program's variable @code{width}, use
16989 (@value{GDBP}) set var width=47
16992 Because the @code{set} command has many subcommands that can conflict
16993 with the names of program variables, it is a good idea to use the
16994 @code{set variable} command instead of just @code{set}. For example, if
16995 your program has a variable @code{g}, you run into problems if you try
16996 to set a new value with just @samp{set g=4}, because @value{GDBN} has
16997 the command @code{set gnutarget}, abbreviated @code{set g}:
17001 (@value{GDBP}) whatis g
17005 (@value{GDBP}) set g=4
17009 The program being debugged has been started already.
17010 Start it from the beginning? (y or n) y
17011 Starting program: /home/smith/cc_progs/a.out
17012 "/home/smith/cc_progs/a.out": can't open to read symbols:
17013 Invalid bfd target.
17014 (@value{GDBP}) show g
17015 The current BFD target is "=4".
17020 The program variable @code{g} did not change, and you silently set the
17021 @code{gnutarget} to an invalid value. In order to set the variable
17025 (@value{GDBP}) set var g=4
17028 @value{GDBN} allows more implicit conversions in assignments than C; you can
17029 freely store an integer value into a pointer variable or vice versa,
17030 and you can convert any structure to any other structure that is the
17031 same length or shorter.
17032 @comment FIXME: how do structs align/pad in these conversions?
17033 @comment /doc@cygnus.com 18dec1990
17035 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
17036 construct to generate a value of specified type at a specified address
17037 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
17038 to memory location @code{0x83040} as an integer (which implies a certain size
17039 and representation in memory), and
17042 set @{int@}0x83040 = 4
17046 stores the value 4 into that memory location.
17049 @section Continuing at a Different Address
17051 Ordinarily, when you continue your program, you do so at the place where
17052 it stopped, with the @code{continue} command. You can instead continue at
17053 an address of your own choosing, with the following commands:
17057 @kindex j @r{(@code{jump})}
17058 @item jump @var{location}
17059 @itemx j @var{location}
17060 Resume execution at @var{location}. Execution stops again immediately
17061 if there is a breakpoint there. @xref{Specify Location}, for a description
17062 of the different forms of @var{location}. It is common
17063 practice to use the @code{tbreak} command in conjunction with
17064 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
17066 The @code{jump} command does not change the current stack frame, or
17067 the stack pointer, or the contents of any memory location or any
17068 register other than the program counter. If @var{location} is in
17069 a different function from the one currently executing, the results may
17070 be bizarre if the two functions expect different patterns of arguments or
17071 of local variables. For this reason, the @code{jump} command requests
17072 confirmation if the specified line is not in the function currently
17073 executing. However, even bizarre results are predictable if you are
17074 well acquainted with the machine-language code of your program.
17077 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
17078 On many systems, you can get much the same effect as the @code{jump}
17079 command by storing a new value into the register @code{$pc}. The
17080 difference is that this does not start your program running; it only
17081 changes the address of where it @emph{will} run when you continue. For
17089 makes the next @code{continue} command or stepping command execute at
17090 address @code{0x485}, rather than at the address where your program stopped.
17091 @xref{Continuing and Stepping, ,Continuing and Stepping}.
17093 The most common occasion to use the @code{jump} command is to back
17094 up---perhaps with more breakpoints set---over a portion of a program
17095 that has already executed, in order to examine its execution in more
17100 @section Giving your Program a Signal
17101 @cindex deliver a signal to a program
17105 @item signal @var{signal}
17106 Resume execution where your program is stopped, but immediately give it the
17107 signal @var{signal}. The @var{signal} can be the name or the number of a
17108 signal. For example, on many systems @code{signal 2} and @code{signal
17109 SIGINT} are both ways of sending an interrupt signal.
17111 Alternatively, if @var{signal} is zero, continue execution without
17112 giving a signal. This is useful when your program stopped on account of
17113 a signal and would ordinarily see the signal when resumed with the
17114 @code{continue} command; @samp{signal 0} causes it to resume without a
17117 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
17118 delivered to the currently selected thread, not the thread that last
17119 reported a stop. This includes the situation where a thread was
17120 stopped due to a signal. So if you want to continue execution
17121 suppressing the signal that stopped a thread, you should select that
17122 same thread before issuing the @samp{signal 0} command. If you issue
17123 the @samp{signal 0} command with another thread as the selected one,
17124 @value{GDBN} detects that and asks for confirmation.
17126 Invoking the @code{signal} command is not the same as invoking the
17127 @code{kill} utility from the shell. Sending a signal with @code{kill}
17128 causes @value{GDBN} to decide what to do with the signal depending on
17129 the signal handling tables (@pxref{Signals}). The @code{signal} command
17130 passes the signal directly to your program.
17132 @code{signal} does not repeat when you press @key{RET} a second time
17133 after executing the command.
17135 @kindex queue-signal
17136 @item queue-signal @var{signal}
17137 Queue @var{signal} to be delivered immediately to the current thread
17138 when execution of the thread resumes. The @var{signal} can be the name or
17139 the number of a signal. For example, on many systems @code{signal 2} and
17140 @code{signal SIGINT} are both ways of sending an interrupt signal.
17141 The handling of the signal must be set to pass the signal to the program,
17142 otherwise @value{GDBN} will report an error.
17143 You can control the handling of signals from @value{GDBN} with the
17144 @code{handle} command (@pxref{Signals}).
17146 Alternatively, if @var{signal} is zero, any currently queued signal
17147 for the current thread is discarded and when execution resumes no signal
17148 will be delivered. This is useful when your program stopped on account
17149 of a signal and would ordinarily see the signal when resumed with the
17150 @code{continue} command.
17152 This command differs from the @code{signal} command in that the signal
17153 is just queued, execution is not resumed. And @code{queue-signal} cannot
17154 be used to pass a signal whose handling state has been set to @code{nopass}
17159 @xref{stepping into signal handlers}, for information on how stepping
17160 commands behave when the thread has a signal queued.
17163 @section Returning from a Function
17166 @cindex returning from a function
17169 @itemx return @var{expression}
17170 You can cancel execution of a function call with the @code{return}
17171 command. If you give an
17172 @var{expression} argument, its value is used as the function's return
17176 When you use @code{return}, @value{GDBN} discards the selected stack frame
17177 (and all frames within it). You can think of this as making the
17178 discarded frame return prematurely. If you wish to specify a value to
17179 be returned, give that value as the argument to @code{return}.
17181 This pops the selected stack frame (@pxref{Selection, ,Selecting a
17182 Frame}), and any other frames inside of it, leaving its caller as the
17183 innermost remaining frame. That frame becomes selected. The
17184 specified value is stored in the registers used for returning values
17187 The @code{return} command does not resume execution; it leaves the
17188 program stopped in the state that would exist if the function had just
17189 returned. In contrast, the @code{finish} command (@pxref{Continuing
17190 and Stepping, ,Continuing and Stepping}) resumes execution until the
17191 selected stack frame returns naturally.
17193 @value{GDBN} needs to know how the @var{expression} argument should be set for
17194 the inferior. The concrete registers assignment depends on the OS ABI and the
17195 type being returned by the selected stack frame. For example it is common for
17196 OS ABI to return floating point values in FPU registers while integer values in
17197 CPU registers. Still some ABIs return even floating point values in CPU
17198 registers. Larger integer widths (such as @code{long long int}) also have
17199 specific placement rules. @value{GDBN} already knows the OS ABI from its
17200 current target so it needs to find out also the type being returned to make the
17201 assignment into the right register(s).
17203 Normally, the selected stack frame has debug info. @value{GDBN} will always
17204 use the debug info instead of the implicit type of @var{expression} when the
17205 debug info is available. For example, if you type @kbd{return -1}, and the
17206 function in the current stack frame is declared to return a @code{long long
17207 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
17208 into a @code{long long int}:
17211 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
17213 (@value{GDBP}) return -1
17214 Make func return now? (y or n) y
17215 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
17216 43 printf ("result=%lld\n", func ());
17220 However, if the selected stack frame does not have a debug info, e.g., if the
17221 function was compiled without debug info, @value{GDBN} has to find out the type
17222 to return from user. Specifying a different type by mistake may set the value
17223 in different inferior registers than the caller code expects. For example,
17224 typing @kbd{return -1} with its implicit type @code{int} would set only a part
17225 of a @code{long long int} result for a debug info less function (on 32-bit
17226 architectures). Therefore the user is required to specify the return type by
17227 an appropriate cast explicitly:
17230 Breakpoint 2, 0x0040050b in func ()
17231 (@value{GDBP}) return -1
17232 Return value type not available for selected stack frame.
17233 Please use an explicit cast of the value to return.
17234 (@value{GDBP}) return (long long int) -1
17235 Make selected stack frame return now? (y or n) y
17236 #0 0x00400526 in main ()
17241 @section Calling Program Functions
17244 @cindex calling functions
17245 @cindex inferior functions, calling
17246 @item print @var{expr}
17247 Evaluate the expression @var{expr} and display the resulting value.
17248 The expression may include calls to functions in the program being
17252 @item call @var{expr}
17253 Evaluate the expression @var{expr} without displaying @code{void}
17256 You can use this variant of the @code{print} command if you want to
17257 execute a function from your program that does not return anything
17258 (a.k.a.@: @dfn{a void function}), but without cluttering the output
17259 with @code{void} returned values that @value{GDBN} will otherwise
17260 print. If the result is not void, it is printed and saved in the
17264 It is possible for the function you call via the @code{print} or
17265 @code{call} command to generate a signal (e.g., if there's a bug in
17266 the function, or if you passed it incorrect arguments). What happens
17267 in that case is controlled by the @code{set unwindonsignal} command.
17269 Similarly, with a C@t{++} program it is possible for the function you
17270 call via the @code{print} or @code{call} command to generate an
17271 exception that is not handled due to the constraints of the dummy
17272 frame. In this case, any exception that is raised in the frame, but has
17273 an out-of-frame exception handler will not be found. GDB builds a
17274 dummy-frame for the inferior function call, and the unwinder cannot
17275 seek for exception handlers outside of this dummy-frame. What happens
17276 in that case is controlled by the
17277 @code{set unwind-on-terminating-exception} command.
17280 @item set unwindonsignal
17281 @kindex set unwindonsignal
17282 @cindex unwind stack in called functions
17283 @cindex call dummy stack unwinding
17284 Set unwinding of the stack if a signal is received while in a function
17285 that @value{GDBN} called in the program being debugged. If set to on,
17286 @value{GDBN} unwinds the stack it created for the call and restores
17287 the context to what it was before the call. If set to off (the
17288 default), @value{GDBN} stops in the frame where the signal was
17291 @item show unwindonsignal
17292 @kindex show unwindonsignal
17293 Show the current setting of stack unwinding in the functions called by
17296 @item set unwind-on-terminating-exception
17297 @kindex set unwind-on-terminating-exception
17298 @cindex unwind stack in called functions with unhandled exceptions
17299 @cindex call dummy stack unwinding on unhandled exception.
17300 Set unwinding of the stack if a C@t{++} exception is raised, but left
17301 unhandled while in a function that @value{GDBN} called in the program being
17302 debugged. If set to on (the default), @value{GDBN} unwinds the stack
17303 it created for the call and restores the context to what it was before
17304 the call. If set to off, @value{GDBN} the exception is delivered to
17305 the default C@t{++} exception handler and the inferior terminated.
17307 @item show unwind-on-terminating-exception
17308 @kindex show unwind-on-terminating-exception
17309 Show the current setting of stack unwinding in the functions called by
17314 @cindex weak alias functions
17315 Sometimes, a function you wish to call is actually a @dfn{weak alias}
17316 for another function. In such case, @value{GDBN} might not pick up
17317 the type information, including the types of the function arguments,
17318 which causes @value{GDBN} to call the inferior function incorrectly.
17319 As a result, the called function will function erroneously and may
17320 even crash. A solution to that is to use the name of the aliased
17324 @section Patching Programs
17326 @cindex patching binaries
17327 @cindex writing into executables
17328 @cindex writing into corefiles
17330 By default, @value{GDBN} opens the file containing your program's
17331 executable code (or the corefile) read-only. This prevents accidental
17332 alterations to machine code; but it also prevents you from intentionally
17333 patching your program's binary.
17335 If you'd like to be able to patch the binary, you can specify that
17336 explicitly with the @code{set write} command. For example, you might
17337 want to turn on internal debugging flags, or even to make emergency
17343 @itemx set write off
17344 If you specify @samp{set write on}, @value{GDBN} opens executable and
17345 core files for both reading and writing; if you specify @kbd{set write
17346 off} (the default), @value{GDBN} opens them read-only.
17348 If you have already loaded a file, you must load it again (using the
17349 @code{exec-file} or @code{core-file} command) after changing @code{set
17350 write}, for your new setting to take effect.
17354 Display whether executable files and core files are opened for writing
17355 as well as reading.
17358 @node Compiling and Injecting Code
17359 @section Compiling and injecting code in @value{GDBN}
17360 @cindex injecting code
17361 @cindex writing into executables
17362 @cindex compiling code
17364 @value{GDBN} supports on-demand compilation and code injection into
17365 programs running under @value{GDBN}. GCC 5.0 or higher built with
17366 @file{libcc1.so} must be installed for this functionality to be enabled.
17367 This functionality is implemented with the following commands.
17370 @kindex compile code
17371 @item compile code @var{source-code}
17372 @itemx compile code -raw @var{--} @var{source-code}
17373 Compile @var{source-code} with the compiler language found as the current
17374 language in @value{GDBN} (@pxref{Languages}). If compilation and
17375 injection is not supported with the current language specified in
17376 @value{GDBN}, or the compiler does not support this feature, an error
17377 message will be printed. If @var{source-code} compiles and links
17378 successfully, @value{GDBN} will load the object-code emitted,
17379 and execute it within the context of the currently selected inferior.
17380 It is important to note that the compiled code is executed immediately.
17381 After execution, the compiled code is removed from @value{GDBN} and any
17382 new types or variables you have defined will be deleted.
17384 The command allows you to specify @var{source-code} in two ways.
17385 The simplest method is to provide a single line of code to the command.
17389 compile code printf ("hello world\n");
17392 If you specify options on the command line as well as source code, they
17393 may conflict. The @samp{--} delimiter can be used to separate options
17394 from actual source code. E.g.:
17397 compile code -r -- printf ("hello world\n");
17400 Alternatively you can enter source code as multiple lines of text. To
17401 enter this mode, invoke the @samp{compile code} command without any text
17402 following the command. This will start the multiple-line editor and
17403 allow you to type as many lines of source code as required. When you
17404 have completed typing, enter @samp{end} on its own line to exit the
17409 >printf ("hello\n");
17410 >printf ("world\n");
17414 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
17415 provided @var{source-code} in a callable scope. In this case, you must
17416 specify the entry point of the code by defining a function named
17417 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
17418 inferior. Using @samp{-raw} option may be needed for example when
17419 @var{source-code} requires @samp{#include} lines which may conflict with
17420 inferior symbols otherwise.
17422 @kindex compile file
17423 @item compile file @var{filename}
17424 @itemx compile file -raw @var{filename}
17425 Like @code{compile code}, but take the source code from @var{filename}.
17428 compile file /home/user/example.c
17433 @item compile print @var{expr}
17434 @itemx compile print /@var{f} @var{expr}
17435 Compile and execute @var{expr} with the compiler language found as the
17436 current language in @value{GDBN} (@pxref{Languages}). By default the
17437 value of @var{expr} is printed in a format appropriate to its data type;
17438 you can choose a different format by specifying @samp{/@var{f}}, where
17439 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
17442 @item compile print
17443 @itemx compile print /@var{f}
17444 @cindex reprint the last value
17445 Alternatively you can enter the expression (source code producing it) as
17446 multiple lines of text. To enter this mode, invoke the @samp{compile print}
17447 command without any text following the command. This will start the
17448 multiple-line editor.
17452 The process of compiling and injecting the code can be inspected using:
17455 @anchor{set debug compile}
17456 @item set debug compile
17457 @cindex compile command debugging info
17458 Turns on or off display of @value{GDBN} process of compiling and
17459 injecting the code. The default is off.
17461 @item show debug compile
17462 Displays the current state of displaying @value{GDBN} process of
17463 compiling and injecting the code.
17466 @subsection Compilation options for the @code{compile} command
17468 @value{GDBN} needs to specify the right compilation options for the code
17469 to be injected, in part to make its ABI compatible with the inferior
17470 and in part to make the injected code compatible with @value{GDBN}'s
17474 The options used, in increasing precedence:
17477 @item target architecture and OS options (@code{gdbarch})
17478 These options depend on target processor type and target operating
17479 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
17480 (@code{-m64}) compilation option.
17482 @item compilation options recorded in the target
17483 @value{NGCC} (since version 4.7) stores the options used for compilation
17484 into @code{DW_AT_producer} part of DWARF debugging information according
17485 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
17486 explicitly specify @code{-g} during inferior compilation otherwise
17487 @value{NGCC} produces no DWARF. This feature is only relevant for
17488 platforms where @code{-g} produces DWARF by default, otherwise one may
17489 try to enforce DWARF by using @code{-gdwarf-4}.
17491 @item compilation options set by @code{set compile-args}
17495 You can override compilation options using the following command:
17498 @item set compile-args
17499 @cindex compile command options override
17500 Set compilation options used for compiling and injecting code with the
17501 @code{compile} commands. These options override any conflicting ones
17502 from the target architecture and/or options stored during inferior
17505 @item show compile-args
17506 Displays the current state of compilation options override.
17507 This does not show all the options actually used during compilation,
17508 use @ref{set debug compile} for that.
17511 @subsection Caveats when using the @code{compile} command
17513 There are a few caveats to keep in mind when using the @code{compile}
17514 command. As the caveats are different per language, the table below
17515 highlights specific issues on a per language basis.
17518 @item C code examples and caveats
17519 When the language in @value{GDBN} is set to @samp{C}, the compiler will
17520 attempt to compile the source code with a @samp{C} compiler. The source
17521 code provided to the @code{compile} command will have much the same
17522 access to variables and types as it normally would if it were part of
17523 the program currently being debugged in @value{GDBN}.
17525 Below is a sample program that forms the basis of the examples that
17526 follow. This program has been compiled and loaded into @value{GDBN},
17527 much like any other normal debugging session.
17530 void function1 (void)
17533 printf ("function 1\n");
17536 void function2 (void)
17551 For the purposes of the examples in this section, the program above has
17552 been compiled, loaded into @value{GDBN}, stopped at the function
17553 @code{main}, and @value{GDBN} is awaiting input from the user.
17555 To access variables and types for any program in @value{GDBN}, the
17556 program must be compiled and packaged with debug information. The
17557 @code{compile} command is not an exception to this rule. Without debug
17558 information, you can still use the @code{compile} command, but you will
17559 be very limited in what variables and types you can access.
17561 So with that in mind, the example above has been compiled with debug
17562 information enabled. The @code{compile} command will have access to
17563 all variables and types (except those that may have been optimized
17564 out). Currently, as @value{GDBN} has stopped the program in the
17565 @code{main} function, the @code{compile} command would have access to
17566 the variable @code{k}. You could invoke the @code{compile} command
17567 and type some source code to set the value of @code{k}. You can also
17568 read it, or do anything with that variable you would normally do in
17569 @code{C}. Be aware that changes to inferior variables in the
17570 @code{compile} command are persistent. In the following example:
17573 compile code k = 3;
17577 the variable @code{k} is now 3. It will retain that value until
17578 something else in the example program changes it, or another
17579 @code{compile} command changes it.
17581 Normal scope and access rules apply to source code compiled and
17582 injected by the @code{compile} command. In the example, the variables
17583 @code{j} and @code{k} are not accessible yet, because the program is
17584 currently stopped in the @code{main} function, where these variables
17585 are not in scope. Therefore, the following command
17588 compile code j = 3;
17592 will result in a compilation error message.
17594 Once the program is continued, execution will bring these variables in
17595 scope, and they will become accessible; then the code you specify via
17596 the @code{compile} command will be able to access them.
17598 You can create variables and types with the @code{compile} command as
17599 part of your source code. Variables and types that are created as part
17600 of the @code{compile} command are not visible to the rest of the program for
17601 the duration of its run. This example is valid:
17604 compile code int ff = 5; printf ("ff is %d\n", ff);
17607 However, if you were to type the following into @value{GDBN} after that
17608 command has completed:
17611 compile code printf ("ff is %d\n'', ff);
17615 a compiler error would be raised as the variable @code{ff} no longer
17616 exists. Object code generated and injected by the @code{compile}
17617 command is removed when its execution ends. Caution is advised
17618 when assigning to program variables values of variables created by the
17619 code submitted to the @code{compile} command. This example is valid:
17622 compile code int ff = 5; k = ff;
17625 The value of the variable @code{ff} is assigned to @code{k}. The variable
17626 @code{k} does not require the existence of @code{ff} to maintain the value
17627 it has been assigned. However, pointers require particular care in
17628 assignment. If the source code compiled with the @code{compile} command
17629 changed the address of a pointer in the example program, perhaps to a
17630 variable created in the @code{compile} command, that pointer would point
17631 to an invalid location when the command exits. The following example
17632 would likely cause issues with your debugged program:
17635 compile code int ff = 5; p = &ff;
17638 In this example, @code{p} would point to @code{ff} when the
17639 @code{compile} command is executing the source code provided to it.
17640 However, as variables in the (example) program persist with their
17641 assigned values, the variable @code{p} would point to an invalid
17642 location when the command exists. A general rule should be followed
17643 in that you should either assign @code{NULL} to any assigned pointers,
17644 or restore a valid location to the pointer before the command exits.
17646 Similar caution must be exercised with any structs, unions, and typedefs
17647 defined in @code{compile} command. Types defined in the @code{compile}
17648 command will no longer be available in the next @code{compile} command.
17649 Therefore, if you cast a variable to a type defined in the
17650 @code{compile} command, care must be taken to ensure that any future
17651 need to resolve the type can be achieved.
17654 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
17655 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
17656 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
17657 Compilation failed.
17658 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
17662 Variables that have been optimized away by the compiler are not
17663 accessible to the code submitted to the @code{compile} command.
17664 Access to those variables will generate a compiler error which @value{GDBN}
17665 will print to the console.
17668 @subsection Compiler search for the @code{compile} command
17670 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged which
17671 may not be obvious for remote targets of different architecture than where
17672 @value{GDBN} is running. Environment variable @code{PATH} (@code{PATH} from
17673 shell that executed @value{GDBN}, not the one set by @value{GDBN}
17674 command @code{set environment}). @xref{Environment}. @code{PATH} on
17675 @value{GDBN} host is searched for @value{NGCC} binary matching the
17676 target architecture and operating system.
17678 Specifically @code{PATH} is searched for binaries matching regular expression
17679 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
17680 debugged. @var{arch} is processor name --- multiarch is supported, so for
17681 example both @code{i386} and @code{x86_64} targets look for pattern
17682 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
17683 for pattern @code{s390x?}. @var{os} is currently supported only for
17684 pattern @code{linux(-gnu)?}.
17687 @chapter @value{GDBN} Files
17689 @value{GDBN} needs to know the file name of the program to be debugged,
17690 both in order to read its symbol table and in order to start your
17691 program. To debug a core dump of a previous run, you must also tell
17692 @value{GDBN} the name of the core dump file.
17695 * Files:: Commands to specify files
17696 * Separate Debug Files:: Debugging information in separate files
17697 * MiniDebugInfo:: Debugging information in a special section
17698 * Index Files:: Index files speed up GDB
17699 * Symbol Errors:: Errors reading symbol files
17700 * Data Files:: GDB data files
17704 @section Commands to Specify Files
17706 @cindex symbol table
17707 @cindex core dump file
17709 You may want to specify executable and core dump file names. The usual
17710 way to do this is at start-up time, using the arguments to
17711 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
17712 Out of @value{GDBN}}).
17714 Occasionally it is necessary to change to a different file during a
17715 @value{GDBN} session. Or you may run @value{GDBN} and forget to
17716 specify a file you want to use. Or you are debugging a remote target
17717 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
17718 Program}). In these situations the @value{GDBN} commands to specify
17719 new files are useful.
17722 @cindex executable file
17724 @item file @var{filename}
17725 Use @var{filename} as the program to be debugged. It is read for its
17726 symbols and for the contents of pure memory. It is also the program
17727 executed when you use the @code{run} command. If you do not specify a
17728 directory and the file is not found in the @value{GDBN} working directory,
17729 @value{GDBN} uses the environment variable @code{PATH} as a list of
17730 directories to search, just as the shell does when looking for a program
17731 to run. You can change the value of this variable, for both @value{GDBN}
17732 and your program, using the @code{path} command.
17734 @cindex unlinked object files
17735 @cindex patching object files
17736 You can load unlinked object @file{.o} files into @value{GDBN} using
17737 the @code{file} command. You will not be able to ``run'' an object
17738 file, but you can disassemble functions and inspect variables. Also,
17739 if the underlying BFD functionality supports it, you could use
17740 @kbd{gdb -write} to patch object files using this technique. Note
17741 that @value{GDBN} can neither interpret nor modify relocations in this
17742 case, so branches and some initialized variables will appear to go to
17743 the wrong place. But this feature is still handy from time to time.
17746 @code{file} with no argument makes @value{GDBN} discard any information it
17747 has on both executable file and the symbol table.
17750 @item exec-file @r{[} @var{filename} @r{]}
17751 Specify that the program to be run (but not the symbol table) is found
17752 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
17753 if necessary to locate your program. Omitting @var{filename} means to
17754 discard information on the executable file.
17756 @kindex symbol-file
17757 @item symbol-file @r{[} @var{filename} @r{]}
17758 Read symbol table information from file @var{filename}. @code{PATH} is
17759 searched when necessary. Use the @code{file} command to get both symbol
17760 table and program to run from the same file.
17762 @code{symbol-file} with no argument clears out @value{GDBN} information on your
17763 program's symbol table.
17765 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
17766 some breakpoints and auto-display expressions. This is because they may
17767 contain pointers to the internal data recording symbols and data types,
17768 which are part of the old symbol table data being discarded inside
17771 @code{symbol-file} does not repeat if you press @key{RET} again after
17774 When @value{GDBN} is configured for a particular environment, it
17775 understands debugging information in whatever format is the standard
17776 generated for that environment; you may use either a @sc{gnu} compiler, or
17777 other compilers that adhere to the local conventions.
17778 Best results are usually obtained from @sc{gnu} compilers; for example,
17779 using @code{@value{NGCC}} you can generate debugging information for
17782 For most kinds of object files, with the exception of old SVR3 systems
17783 using COFF, the @code{symbol-file} command does not normally read the
17784 symbol table in full right away. Instead, it scans the symbol table
17785 quickly to find which source files and which symbols are present. The
17786 details are read later, one source file at a time, as they are needed.
17788 The purpose of this two-stage reading strategy is to make @value{GDBN}
17789 start up faster. For the most part, it is invisible except for
17790 occasional pauses while the symbol table details for a particular source
17791 file are being read. (The @code{set verbose} command can turn these
17792 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
17793 Warnings and Messages}.)
17795 We have not implemented the two-stage strategy for COFF yet. When the
17796 symbol table is stored in COFF format, @code{symbol-file} reads the
17797 symbol table data in full right away. Note that ``stabs-in-COFF''
17798 still does the two-stage strategy, since the debug info is actually
17802 @cindex reading symbols immediately
17803 @cindex symbols, reading immediately
17804 @item symbol-file @r{[} -readnow @r{]} @var{filename}
17805 @itemx file @r{[} -readnow @r{]} @var{filename}
17806 You can override the @value{GDBN} two-stage strategy for reading symbol
17807 tables by using the @samp{-readnow} option with any of the commands that
17808 load symbol table information, if you want to be sure @value{GDBN} has the
17809 entire symbol table available.
17811 @c FIXME: for now no mention of directories, since this seems to be in
17812 @c flux. 13mar1992 status is that in theory GDB would look either in
17813 @c current dir or in same dir as myprog; but issues like competing
17814 @c GDB's, or clutter in system dirs, mean that in practice right now
17815 @c only current dir is used. FFish says maybe a special GDB hierarchy
17816 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
17820 @item core-file @r{[}@var{filename}@r{]}
17822 Specify the whereabouts of a core dump file to be used as the ``contents
17823 of memory''. Traditionally, core files contain only some parts of the
17824 address space of the process that generated them; @value{GDBN} can access the
17825 executable file itself for other parts.
17827 @code{core-file} with no argument specifies that no core file is
17830 Note that the core file is ignored when your program is actually running
17831 under @value{GDBN}. So, if you have been running your program and you
17832 wish to debug a core file instead, you must kill the subprocess in which
17833 the program is running. To do this, use the @code{kill} command
17834 (@pxref{Kill Process, ,Killing the Child Process}).
17836 @kindex add-symbol-file
17837 @cindex dynamic linking
17838 @item add-symbol-file @var{filename} @var{address}
17839 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
17840 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
17841 The @code{add-symbol-file} command reads additional symbol table
17842 information from the file @var{filename}. You would use this command
17843 when @var{filename} has been dynamically loaded (by some other means)
17844 into the program that is running. The @var{address} should give the memory
17845 address at which the file has been loaded; @value{GDBN} cannot figure
17846 this out for itself. You can additionally specify an arbitrary number
17847 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
17848 section name and base address for that section. You can specify any
17849 @var{address} as an expression.
17851 The symbol table of the file @var{filename} is added to the symbol table
17852 originally read with the @code{symbol-file} command. You can use the
17853 @code{add-symbol-file} command any number of times; the new symbol data
17854 thus read is kept in addition to the old.
17856 Changes can be reverted using the command @code{remove-symbol-file}.
17858 @cindex relocatable object files, reading symbols from
17859 @cindex object files, relocatable, reading symbols from
17860 @cindex reading symbols from relocatable object files
17861 @cindex symbols, reading from relocatable object files
17862 @cindex @file{.o} files, reading symbols from
17863 Although @var{filename} is typically a shared library file, an
17864 executable file, or some other object file which has been fully
17865 relocated for loading into a process, you can also load symbolic
17866 information from relocatable @file{.o} files, as long as:
17870 the file's symbolic information refers only to linker symbols defined in
17871 that file, not to symbols defined by other object files,
17873 every section the file's symbolic information refers to has actually
17874 been loaded into the inferior, as it appears in the file, and
17876 you can determine the address at which every section was loaded, and
17877 provide these to the @code{add-symbol-file} command.
17881 Some embedded operating systems, like Sun Chorus and VxWorks, can load
17882 relocatable files into an already running program; such systems
17883 typically make the requirements above easy to meet. However, it's
17884 important to recognize that many native systems use complex link
17885 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
17886 assembly, for example) that make the requirements difficult to meet. In
17887 general, one cannot assume that using @code{add-symbol-file} to read a
17888 relocatable object file's symbolic information will have the same effect
17889 as linking the relocatable object file into the program in the normal
17892 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
17894 @kindex remove-symbol-file
17895 @item remove-symbol-file @var{filename}
17896 @item remove-symbol-file -a @var{address}
17897 Remove a symbol file added via the @code{add-symbol-file} command. The
17898 file to remove can be identified by its @var{filename} or by an @var{address}
17899 that lies within the boundaries of this symbol file in memory. Example:
17902 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
17903 add symbol table from file "/home/user/gdb/mylib.so" at
17904 .text_addr = 0x7ffff7ff9480
17906 Reading symbols from /home/user/gdb/mylib.so...done.
17907 (gdb) remove-symbol-file -a 0x7ffff7ff9480
17908 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
17913 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
17915 @kindex add-symbol-file-from-memory
17916 @cindex @code{syscall DSO}
17917 @cindex load symbols from memory
17918 @item add-symbol-file-from-memory @var{address}
17919 Load symbols from the given @var{address} in a dynamically loaded
17920 object file whose image is mapped directly into the inferior's memory.
17921 For example, the Linux kernel maps a @code{syscall DSO} into each
17922 process's address space; this DSO provides kernel-specific code for
17923 some system calls. The argument can be any expression whose
17924 evaluation yields the address of the file's shared object file header.
17925 For this command to work, you must have used @code{symbol-file} or
17926 @code{exec-file} commands in advance.
17929 @item section @var{section} @var{addr}
17930 The @code{section} command changes the base address of the named
17931 @var{section} of the exec file to @var{addr}. This can be used if the
17932 exec file does not contain section addresses, (such as in the
17933 @code{a.out} format), or when the addresses specified in the file
17934 itself are wrong. Each section must be changed separately. The
17935 @code{info files} command, described below, lists all the sections and
17939 @kindex info target
17942 @code{info files} and @code{info target} are synonymous; both print the
17943 current target (@pxref{Targets, ,Specifying a Debugging Target}),
17944 including the names of the executable and core dump files currently in
17945 use by @value{GDBN}, and the files from which symbols were loaded. The
17946 command @code{help target} lists all possible targets rather than
17949 @kindex maint info sections
17950 @item maint info sections
17951 Another command that can give you extra information about program sections
17952 is @code{maint info sections}. In addition to the section information
17953 displayed by @code{info files}, this command displays the flags and file
17954 offset of each section in the executable and core dump files. In addition,
17955 @code{maint info sections} provides the following command options (which
17956 may be arbitrarily combined):
17960 Display sections for all loaded object files, including shared libraries.
17961 @item @var{sections}
17962 Display info only for named @var{sections}.
17963 @item @var{section-flags}
17964 Display info only for sections for which @var{section-flags} are true.
17965 The section flags that @value{GDBN} currently knows about are:
17968 Section will have space allocated in the process when loaded.
17969 Set for all sections except those containing debug information.
17971 Section will be loaded from the file into the child process memory.
17972 Set for pre-initialized code and data, clear for @code{.bss} sections.
17974 Section needs to be relocated before loading.
17976 Section cannot be modified by the child process.
17978 Section contains executable code only.
17980 Section contains data only (no executable code).
17982 Section will reside in ROM.
17984 Section contains data for constructor/destructor lists.
17986 Section is not empty.
17988 An instruction to the linker to not output the section.
17989 @item COFF_SHARED_LIBRARY
17990 A notification to the linker that the section contains
17991 COFF shared library information.
17993 Section contains common symbols.
17996 @kindex set trust-readonly-sections
17997 @cindex read-only sections
17998 @item set trust-readonly-sections on
17999 Tell @value{GDBN} that readonly sections in your object file
18000 really are read-only (i.e.@: that their contents will not change).
18001 In that case, @value{GDBN} can fetch values from these sections
18002 out of the object file, rather than from the target program.
18003 For some targets (notably embedded ones), this can be a significant
18004 enhancement to debugging performance.
18006 The default is off.
18008 @item set trust-readonly-sections off
18009 Tell @value{GDBN} not to trust readonly sections. This means that
18010 the contents of the section might change while the program is running,
18011 and must therefore be fetched from the target when needed.
18013 @item show trust-readonly-sections
18014 Show the current setting of trusting readonly sections.
18017 All file-specifying commands allow both absolute and relative file names
18018 as arguments. @value{GDBN} always converts the file name to an absolute file
18019 name and remembers it that way.
18021 @cindex shared libraries
18022 @anchor{Shared Libraries}
18023 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
18024 and IBM RS/6000 AIX shared libraries.
18026 On MS-Windows @value{GDBN} must be linked with the Expat library to support
18027 shared libraries. @xref{Expat}.
18029 @value{GDBN} automatically loads symbol definitions from shared libraries
18030 when you use the @code{run} command, or when you examine a core file.
18031 (Before you issue the @code{run} command, @value{GDBN} does not understand
18032 references to a function in a shared library, however---unless you are
18033 debugging a core file).
18035 On HP-UX, if the program loads a library explicitly, @value{GDBN}
18036 automatically loads the symbols at the time of the @code{shl_load} call.
18038 @c FIXME: some @value{GDBN} release may permit some refs to undef
18039 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
18040 @c FIXME...lib; check this from time to time when updating manual
18042 There are times, however, when you may wish to not automatically load
18043 symbol definitions from shared libraries, such as when they are
18044 particularly large or there are many of them.
18046 To control the automatic loading of shared library symbols, use the
18050 @kindex set auto-solib-add
18051 @item set auto-solib-add @var{mode}
18052 If @var{mode} is @code{on}, symbols from all shared object libraries
18053 will be loaded automatically when the inferior begins execution, you
18054 attach to an independently started inferior, or when the dynamic linker
18055 informs @value{GDBN} that a new library has been loaded. If @var{mode}
18056 is @code{off}, symbols must be loaded manually, using the
18057 @code{sharedlibrary} command. The default value is @code{on}.
18059 @cindex memory used for symbol tables
18060 If your program uses lots of shared libraries with debug info that
18061 takes large amounts of memory, you can decrease the @value{GDBN}
18062 memory footprint by preventing it from automatically loading the
18063 symbols from shared libraries. To that end, type @kbd{set
18064 auto-solib-add off} before running the inferior, then load each
18065 library whose debug symbols you do need with @kbd{sharedlibrary
18066 @var{regexp}}, where @var{regexp} is a regular expression that matches
18067 the libraries whose symbols you want to be loaded.
18069 @kindex show auto-solib-add
18070 @item show auto-solib-add
18071 Display the current autoloading mode.
18074 @cindex load shared library
18075 To explicitly load shared library symbols, use the @code{sharedlibrary}
18079 @kindex info sharedlibrary
18081 @item info share @var{regex}
18082 @itemx info sharedlibrary @var{regex}
18083 Print the names of the shared libraries which are currently loaded
18084 that match @var{regex}. If @var{regex} is omitted then print
18085 all shared libraries that are loaded.
18088 @item info dll @var{regex}
18089 This is an alias of @code{info sharedlibrary}.
18091 @kindex sharedlibrary
18093 @item sharedlibrary @var{regex}
18094 @itemx share @var{regex}
18095 Load shared object library symbols for files matching a
18096 Unix regular expression.
18097 As with files loaded automatically, it only loads shared libraries
18098 required by your program for a core file or after typing @code{run}. If
18099 @var{regex} is omitted all shared libraries required by your program are
18102 @item nosharedlibrary
18103 @kindex nosharedlibrary
18104 @cindex unload symbols from shared libraries
18105 Unload all shared object library symbols. This discards all symbols
18106 that have been loaded from all shared libraries. Symbols from shared
18107 libraries that were loaded by explicit user requests are not
18111 Sometimes you may wish that @value{GDBN} stops and gives you control
18112 when any of shared library events happen. The best way to do this is
18113 to use @code{catch load} and @code{catch unload} (@pxref{Set
18116 @value{GDBN} also supports the the @code{set stop-on-solib-events}
18117 command for this. This command exists for historical reasons. It is
18118 less useful than setting a catchpoint, because it does not allow for
18119 conditions or commands as a catchpoint does.
18122 @item set stop-on-solib-events
18123 @kindex set stop-on-solib-events
18124 This command controls whether @value{GDBN} should give you control
18125 when the dynamic linker notifies it about some shared library event.
18126 The most common event of interest is loading or unloading of a new
18129 @item show stop-on-solib-events
18130 @kindex show stop-on-solib-events
18131 Show whether @value{GDBN} stops and gives you control when shared
18132 library events happen.
18135 Shared libraries are also supported in many cross or remote debugging
18136 configurations. @value{GDBN} needs to have access to the target's libraries;
18137 this can be accomplished either by providing copies of the libraries
18138 on the host system, or by asking @value{GDBN} to automatically retrieve the
18139 libraries from the target. If copies of the target libraries are
18140 provided, they need to be the same as the target libraries, although the
18141 copies on the target can be stripped as long as the copies on the host are
18144 @cindex where to look for shared libraries
18145 For remote debugging, you need to tell @value{GDBN} where the target
18146 libraries are, so that it can load the correct copies---otherwise, it
18147 may try to load the host's libraries. @value{GDBN} has two variables
18148 to specify the search directories for target libraries.
18151 @cindex prefix for executable and shared library file names
18152 @cindex system root, alternate
18153 @kindex set solib-absolute-prefix
18154 @kindex set sysroot
18155 @item set sysroot @var{path}
18156 Use @var{path} as the system root for the program being debugged. Any
18157 absolute shared library paths will be prefixed with @var{path}; many
18158 runtime loaders store the absolute paths to the shared library in the
18159 target program's memory. When starting processes remotely, and when
18160 attaching to already-running processes (local or remote), their
18161 executable filenames will be prefixed with @var{path} if reported to
18162 @value{GDBN} as absolute by the operating system. If you use
18163 @code{set sysroot} to find executables and shared libraries, they need
18164 to be laid out in the same way that they are on the target, with
18165 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
18168 If @var{path} starts with the sequence @file{target:} and the target
18169 system is remote then @value{GDBN} will retrieve the target binaries
18170 from the remote system. This is only supported when using a remote
18171 target that supports the @code{remote get} command (@pxref{File
18172 Transfer,,Sending files to a remote system}). The part of @var{path}
18173 following the initial @file{target:} (if present) is used as system
18174 root prefix on the remote file system. If @var{path} starts with the
18175 sequence @file{remote:} this is converted to the sequence
18176 @file{target:} by @code{set sysroot}@footnote{Historically the
18177 functionality to retrieve binaries from the remote system was
18178 provided by prefixing @var{path} with @file{remote:}}. If you want
18179 to specify a local system root using a directory that happens to be
18180 named @file{target:} or @file{remote:}, you need to use some
18181 equivalent variant of the name like @file{./target:}.
18183 For targets with an MS-DOS based filesystem, such as MS-Windows and
18184 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
18185 absolute file name with @var{path}. But first, on Unix hosts,
18186 @value{GDBN} converts all backslash directory separators into forward
18187 slashes, because the backslash is not a directory separator on Unix:
18190 c:\foo\bar.dll @result{} c:/foo/bar.dll
18193 Then, @value{GDBN} attempts prefixing the target file name with
18194 @var{path}, and looks for the resulting file name in the host file
18198 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
18201 If that does not find the binary, @value{GDBN} tries removing
18202 the @samp{:} character from the drive spec, both for convenience, and,
18203 for the case of the host file system not supporting file names with
18207 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
18210 This makes it possible to have a system root that mirrors a target
18211 with more than one drive. E.g., you may want to setup your local
18212 copies of the target system shared libraries like so (note @samp{c} vs
18216 @file{/path/to/sysroot/c/sys/bin/foo.dll}
18217 @file{/path/to/sysroot/c/sys/bin/bar.dll}
18218 @file{/path/to/sysroot/z/sys/bin/bar.dll}
18222 and point the system root at @file{/path/to/sysroot}, so that
18223 @value{GDBN} can find the correct copies of both
18224 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
18226 If that still does not find the binary, @value{GDBN} tries
18227 removing the whole drive spec from the target file name:
18230 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
18233 This last lookup makes it possible to not care about the drive name,
18234 if you don't want or need to.
18236 The @code{set solib-absolute-prefix} command is an alias for @code{set
18239 @cindex default system root
18240 @cindex @samp{--with-sysroot}
18241 You can set the default system root by using the configure-time
18242 @samp{--with-sysroot} option. If the system root is inside
18243 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
18244 @samp{--exec-prefix}), then the default system root will be updated
18245 automatically if the installed @value{GDBN} is moved to a new
18248 @kindex show sysroot
18250 Display the current executable and shared library prefix.
18252 @kindex set solib-search-path
18253 @item set solib-search-path @var{path}
18254 If this variable is set, @var{path} is a colon-separated list of
18255 directories to search for shared libraries. @samp{solib-search-path}
18256 is used after @samp{sysroot} fails to locate the library, or if the
18257 path to the library is relative instead of absolute. If you want to
18258 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
18259 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
18260 finding your host's libraries. @samp{sysroot} is preferred; setting
18261 it to a nonexistent directory may interfere with automatic loading
18262 of shared library symbols.
18264 @kindex show solib-search-path
18265 @item show solib-search-path
18266 Display the current shared library search path.
18268 @cindex DOS file-name semantics of file names.
18269 @kindex set target-file-system-kind (unix|dos-based|auto)
18270 @kindex show target-file-system-kind
18271 @item set target-file-system-kind @var{kind}
18272 Set assumed file system kind for target reported file names.
18274 Shared library file names as reported by the target system may not
18275 make sense as is on the system @value{GDBN} is running on. For
18276 example, when remote debugging a target that has MS-DOS based file
18277 system semantics, from a Unix host, the target may be reporting to
18278 @value{GDBN} a list of loaded shared libraries with file names such as
18279 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
18280 drive letters, so the @samp{c:\} prefix is not normally understood as
18281 indicating an absolute file name, and neither is the backslash
18282 normally considered a directory separator character. In that case,
18283 the native file system would interpret this whole absolute file name
18284 as a relative file name with no directory components. This would make
18285 it impossible to point @value{GDBN} at a copy of the remote target's
18286 shared libraries on the host using @code{set sysroot}, and impractical
18287 with @code{set solib-search-path}. Setting
18288 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
18289 to interpret such file names similarly to how the target would, and to
18290 map them to file names valid on @value{GDBN}'s native file system
18291 semantics. The value of @var{kind} can be @code{"auto"}, in addition
18292 to one of the supported file system kinds. In that case, @value{GDBN}
18293 tries to determine the appropriate file system variant based on the
18294 current target's operating system (@pxref{ABI, ,Configuring the
18295 Current ABI}). The supported file system settings are:
18299 Instruct @value{GDBN} to assume the target file system is of Unix
18300 kind. Only file names starting the forward slash (@samp{/}) character
18301 are considered absolute, and the directory separator character is also
18305 Instruct @value{GDBN} to assume the target file system is DOS based.
18306 File names starting with either a forward slash, or a drive letter
18307 followed by a colon (e.g., @samp{c:}), are considered absolute, and
18308 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
18309 considered directory separators.
18312 Instruct @value{GDBN} to use the file system kind associated with the
18313 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
18314 This is the default.
18318 @cindex file name canonicalization
18319 @cindex base name differences
18320 When processing file names provided by the user, @value{GDBN}
18321 frequently needs to compare them to the file names recorded in the
18322 program's debug info. Normally, @value{GDBN} compares just the
18323 @dfn{base names} of the files as strings, which is reasonably fast
18324 even for very large programs. (The base name of a file is the last
18325 portion of its name, after stripping all the leading directories.)
18326 This shortcut in comparison is based upon the assumption that files
18327 cannot have more than one base name. This is usually true, but
18328 references to files that use symlinks or similar filesystem
18329 facilities violate that assumption. If your program records files
18330 using such facilities, or if you provide file names to @value{GDBN}
18331 using symlinks etc., you can set @code{basenames-may-differ} to
18332 @code{true} to instruct @value{GDBN} to completely canonicalize each
18333 pair of file names it needs to compare. This will make file-name
18334 comparisons accurate, but at a price of a significant slowdown.
18337 @item set basenames-may-differ
18338 @kindex set basenames-may-differ
18339 Set whether a source file may have multiple base names.
18341 @item show basenames-may-differ
18342 @kindex show basenames-may-differ
18343 Show whether a source file may have multiple base names.
18347 @section File Caching
18348 @cindex caching of opened files
18349 @cindex caching of bfd objects
18351 To speed up file loading, and reduce memory usage, @value{GDBN} will
18352 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
18353 BFD, bfd, The Binary File Descriptor Library}. The following commands
18354 allow visibility and control of the caching behavior.
18357 @kindex maint info bfds
18358 @item maint info bfds
18359 This prints information about each @code{bfd} object that is known to
18362 @kindex maint set bfd-sharing
18363 @kindex maint show bfd-sharing
18364 @kindex bfd caching
18365 @item maint set bfd-sharing
18366 @item maint show bfd-sharing
18367 Control whether @code{bfd} objects can be shared. When sharing is
18368 enabled @value{GDBN} reuses already open @code{bfd} objects rather
18369 than reopening the same file. Turning sharing off does not cause
18370 already shared @code{bfd} objects to be unshared, but all future files
18371 that are opened will create a new @code{bfd} object. Similarly,
18372 re-enabling sharing does not cause multiple existing @code{bfd}
18373 objects to be collapsed into a single shared @code{bfd} object.
18376 @node Separate Debug Files
18377 @section Debugging Information in Separate Files
18378 @cindex separate debugging information files
18379 @cindex debugging information in separate files
18380 @cindex @file{.debug} subdirectories
18381 @cindex debugging information directory, global
18382 @cindex global debugging information directories
18383 @cindex build ID, and separate debugging files
18384 @cindex @file{.build-id} directory
18386 @value{GDBN} allows you to put a program's debugging information in a
18387 file separate from the executable itself, in a way that allows
18388 @value{GDBN} to find and load the debugging information automatically.
18389 Since debugging information can be very large---sometimes larger
18390 than the executable code itself---some systems distribute debugging
18391 information for their executables in separate files, which users can
18392 install only when they need to debug a problem.
18394 @value{GDBN} supports two ways of specifying the separate debug info
18399 The executable contains a @dfn{debug link} that specifies the name of
18400 the separate debug info file. The separate debug file's name is
18401 usually @file{@var{executable}.debug}, where @var{executable} is the
18402 name of the corresponding executable file without leading directories
18403 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
18404 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
18405 checksum for the debug file, which @value{GDBN} uses to validate that
18406 the executable and the debug file came from the same build.
18409 The executable contains a @dfn{build ID}, a unique bit string that is
18410 also present in the corresponding debug info file. (This is supported
18411 only on some operating systems, when using the ELF or PE file formats
18412 for binary files and the @sc{gnu} Binutils.) For more details about
18413 this feature, see the description of the @option{--build-id}
18414 command-line option in @ref{Options, , Command Line Options, ld.info,
18415 The GNU Linker}. The debug info file's name is not specified
18416 explicitly by the build ID, but can be computed from the build ID, see
18420 Depending on the way the debug info file is specified, @value{GDBN}
18421 uses two different methods of looking for the debug file:
18425 For the ``debug link'' method, @value{GDBN} looks up the named file in
18426 the directory of the executable file, then in a subdirectory of that
18427 directory named @file{.debug}, and finally under each one of the global debug
18428 directories, in a subdirectory whose name is identical to the leading
18429 directories of the executable's absolute file name.
18432 For the ``build ID'' method, @value{GDBN} looks in the
18433 @file{.build-id} subdirectory of each one of the global debug directories for
18434 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
18435 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
18436 are the rest of the bit string. (Real build ID strings are 32 or more
18437 hex characters, not 10.)
18440 So, for example, suppose you ask @value{GDBN} to debug
18441 @file{/usr/bin/ls}, which has a debug link that specifies the
18442 file @file{ls.debug}, and a build ID whose value in hex is
18443 @code{abcdef1234}. If the list of the global debug directories includes
18444 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
18445 debug information files, in the indicated order:
18449 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
18451 @file{/usr/bin/ls.debug}
18453 @file{/usr/bin/.debug/ls.debug}
18455 @file{/usr/lib/debug/usr/bin/ls.debug}.
18458 @anchor{debug-file-directory}
18459 Global debugging info directories default to what is set by @value{GDBN}
18460 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
18461 you can also set the global debugging info directories, and view the list
18462 @value{GDBN} is currently using.
18466 @kindex set debug-file-directory
18467 @item set debug-file-directory @var{directories}
18468 Set the directories which @value{GDBN} searches for separate debugging
18469 information files to @var{directory}. Multiple path components can be set
18470 concatenating them by a path separator.
18472 @kindex show debug-file-directory
18473 @item show debug-file-directory
18474 Show the directories @value{GDBN} searches for separate debugging
18479 @cindex @code{.gnu_debuglink} sections
18480 @cindex debug link sections
18481 A debug link is a special section of the executable file named
18482 @code{.gnu_debuglink}. The section must contain:
18486 A filename, with any leading directory components removed, followed by
18489 zero to three bytes of padding, as needed to reach the next four-byte
18490 boundary within the section, and
18492 a four-byte CRC checksum, stored in the same endianness used for the
18493 executable file itself. The checksum is computed on the debugging
18494 information file's full contents by the function given below, passing
18495 zero as the @var{crc} argument.
18498 Any executable file format can carry a debug link, as long as it can
18499 contain a section named @code{.gnu_debuglink} with the contents
18502 @cindex @code{.note.gnu.build-id} sections
18503 @cindex build ID sections
18504 The build ID is a special section in the executable file (and in other
18505 ELF binary files that @value{GDBN} may consider). This section is
18506 often named @code{.note.gnu.build-id}, but that name is not mandatory.
18507 It contains unique identification for the built files---the ID remains
18508 the same across multiple builds of the same build tree. The default
18509 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
18510 content for the build ID string. The same section with an identical
18511 value is present in the original built binary with symbols, in its
18512 stripped variant, and in the separate debugging information file.
18514 The debugging information file itself should be an ordinary
18515 executable, containing a full set of linker symbols, sections, and
18516 debugging information. The sections of the debugging information file
18517 should have the same names, addresses, and sizes as the original file,
18518 but they need not contain any data---much like a @code{.bss} section
18519 in an ordinary executable.
18521 The @sc{gnu} binary utilities (Binutils) package includes the
18522 @samp{objcopy} utility that can produce
18523 the separated executable / debugging information file pairs using the
18524 following commands:
18527 @kbd{objcopy --only-keep-debug foo foo.debug}
18532 These commands remove the debugging
18533 information from the executable file @file{foo} and place it in the file
18534 @file{foo.debug}. You can use the first, second or both methods to link the
18539 The debug link method needs the following additional command to also leave
18540 behind a debug link in @file{foo}:
18543 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
18546 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
18547 a version of the @code{strip} command such that the command @kbd{strip foo -f
18548 foo.debug} has the same functionality as the two @code{objcopy} commands and
18549 the @code{ln -s} command above, together.
18552 Build ID gets embedded into the main executable using @code{ld --build-id} or
18553 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
18554 compatibility fixes for debug files separation are present in @sc{gnu} binary
18555 utilities (Binutils) package since version 2.18.
18560 @cindex CRC algorithm definition
18561 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
18562 IEEE 802.3 using the polynomial:
18564 @c TexInfo requires naked braces for multi-digit exponents for Tex
18565 @c output, but this causes HTML output to barf. HTML has to be set using
18566 @c raw commands. So we end up having to specify this equation in 2
18571 <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>
18572 + <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
18578 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
18579 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
18583 The function is computed byte at a time, taking the least
18584 significant bit of each byte first. The initial pattern
18585 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
18586 the final result is inverted to ensure trailing zeros also affect the
18589 @emph{Note:} This is the same CRC polynomial as used in handling the
18590 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
18591 However in the case of the Remote Serial Protocol, the CRC is computed
18592 @emph{most} significant bit first, and the result is not inverted, so
18593 trailing zeros have no effect on the CRC value.
18595 To complete the description, we show below the code of the function
18596 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
18597 initially supplied @code{crc} argument means that an initial call to
18598 this function passing in zero will start computing the CRC using
18601 @kindex gnu_debuglink_crc32
18604 gnu_debuglink_crc32 (unsigned long crc,
18605 unsigned char *buf, size_t len)
18607 static const unsigned long crc32_table[256] =
18609 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
18610 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
18611 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
18612 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
18613 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
18614 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
18615 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
18616 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
18617 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
18618 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
18619 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
18620 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
18621 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
18622 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
18623 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
18624 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
18625 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
18626 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
18627 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
18628 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
18629 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
18630 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
18631 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
18632 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
18633 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
18634 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
18635 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
18636 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
18637 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
18638 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
18639 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
18640 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
18641 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
18642 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
18643 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
18644 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
18645 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
18646 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
18647 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
18648 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
18649 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
18650 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
18651 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
18652 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
18653 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
18654 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
18655 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
18656 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
18657 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
18658 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
18659 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
18662 unsigned char *end;
18664 crc = ~crc & 0xffffffff;
18665 for (end = buf + len; buf < end; ++buf)
18666 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
18667 return ~crc & 0xffffffff;
18672 This computation does not apply to the ``build ID'' method.
18674 @node MiniDebugInfo
18675 @section Debugging information in a special section
18676 @cindex separate debug sections
18677 @cindex @samp{.gnu_debugdata} section
18679 Some systems ship pre-built executables and libraries that have a
18680 special @samp{.gnu_debugdata} section. This feature is called
18681 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
18682 is used to supply extra symbols for backtraces.
18684 The intent of this section is to provide extra minimal debugging
18685 information for use in simple backtraces. It is not intended to be a
18686 replacement for full separate debugging information (@pxref{Separate
18687 Debug Files}). The example below shows the intended use; however,
18688 @value{GDBN} does not currently put restrictions on what sort of
18689 debugging information might be included in the section.
18691 @value{GDBN} has support for this extension. If the section exists,
18692 then it is used provided that no other source of debugging information
18693 can be found, and that @value{GDBN} was configured with LZMA support.
18695 This section can be easily created using @command{objcopy} and other
18696 standard utilities:
18699 # Extract the dynamic symbols from the main binary, there is no need
18700 # to also have these in the normal symbol table.
18701 nm -D @var{binary} --format=posix --defined-only \
18702 | awk '@{ print $1 @}' | sort > dynsyms
18704 # Extract all the text (i.e. function) symbols from the debuginfo.
18705 # (Note that we actually also accept "D" symbols, for the benefit
18706 # of platforms like PowerPC64 that use function descriptors.)
18707 nm @var{binary} --format=posix --defined-only \
18708 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
18711 # Keep all the function symbols not already in the dynamic symbol
18713 comm -13 dynsyms funcsyms > keep_symbols
18715 # Separate full debug info into debug binary.
18716 objcopy --only-keep-debug @var{binary} debug
18718 # Copy the full debuginfo, keeping only a minimal set of symbols and
18719 # removing some unnecessary sections.
18720 objcopy -S --remove-section .gdb_index --remove-section .comment \
18721 --keep-symbols=keep_symbols debug mini_debuginfo
18723 # Drop the full debug info from the original binary.
18724 strip --strip-all -R .comment @var{binary}
18726 # Inject the compressed data into the .gnu_debugdata section of the
18729 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
18733 @section Index Files Speed Up @value{GDBN}
18734 @cindex index files
18735 @cindex @samp{.gdb_index} section
18737 When @value{GDBN} finds a symbol file, it scans the symbols in the
18738 file in order to construct an internal symbol table. This lets most
18739 @value{GDBN} operations work quickly---at the cost of a delay early
18740 on. For large programs, this delay can be quite lengthy, so
18741 @value{GDBN} provides a way to build an index, which speeds up
18744 The index is stored as a section in the symbol file. @value{GDBN} can
18745 write the index to a file, then you can put it into the symbol file
18746 using @command{objcopy}.
18748 To create an index file, use the @code{save gdb-index} command:
18751 @item save gdb-index @var{directory}
18752 @kindex save gdb-index
18753 Create an index file for each symbol file currently known by
18754 @value{GDBN}. Each file is named after its corresponding symbol file,
18755 with @samp{.gdb-index} appended, and is written into the given
18759 Once you have created an index file you can merge it into your symbol
18760 file, here named @file{symfile}, using @command{objcopy}:
18763 $ objcopy --add-section .gdb_index=symfile.gdb-index \
18764 --set-section-flags .gdb_index=readonly symfile symfile
18767 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
18768 sections that have been deprecated. Usually they are deprecated because
18769 they are missing a new feature or have performance issues.
18770 To tell @value{GDBN} to use a deprecated index section anyway
18771 specify @code{set use-deprecated-index-sections on}.
18772 The default is @code{off}.
18773 This can speed up startup, but may result in some functionality being lost.
18774 @xref{Index Section Format}.
18776 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
18777 must be done before gdb reads the file. The following will not work:
18780 $ gdb -ex "set use-deprecated-index-sections on" <program>
18783 Instead you must do, for example,
18786 $ gdb -iex "set use-deprecated-index-sections on" <program>
18789 There are currently some limitation on indices. They only work when
18790 for DWARF debugging information, not stabs. And, they do not
18791 currently work for programs using Ada.
18793 @node Symbol Errors
18794 @section Errors Reading Symbol Files
18796 While reading a symbol file, @value{GDBN} occasionally encounters problems,
18797 such as symbol types it does not recognize, or known bugs in compiler
18798 output. By default, @value{GDBN} does not notify you of such problems, since
18799 they are relatively common and primarily of interest to people
18800 debugging compilers. If you are interested in seeing information
18801 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
18802 only one message about each such type of problem, no matter how many
18803 times the problem occurs; or you can ask @value{GDBN} to print more messages,
18804 to see how many times the problems occur, with the @code{set
18805 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
18808 The messages currently printed, and their meanings, include:
18811 @item inner block not inside outer block in @var{symbol}
18813 The symbol information shows where symbol scopes begin and end
18814 (such as at the start of a function or a block of statements). This
18815 error indicates that an inner scope block is not fully contained
18816 in its outer scope blocks.
18818 @value{GDBN} circumvents the problem by treating the inner block as if it had
18819 the same scope as the outer block. In the error message, @var{symbol}
18820 may be shown as ``@code{(don't know)}'' if the outer block is not a
18823 @item block at @var{address} out of order
18825 The symbol information for symbol scope blocks should occur in
18826 order of increasing addresses. This error indicates that it does not
18829 @value{GDBN} does not circumvent this problem, and has trouble
18830 locating symbols in the source file whose symbols it is reading. (You
18831 can often determine what source file is affected by specifying
18832 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
18835 @item bad block start address patched
18837 The symbol information for a symbol scope block has a start address
18838 smaller than the address of the preceding source line. This is known
18839 to occur in the SunOS 4.1.1 (and earlier) C compiler.
18841 @value{GDBN} circumvents the problem by treating the symbol scope block as
18842 starting on the previous source line.
18844 @item bad string table offset in symbol @var{n}
18847 Symbol number @var{n} contains a pointer into the string table which is
18848 larger than the size of the string table.
18850 @value{GDBN} circumvents the problem by considering the symbol to have the
18851 name @code{foo}, which may cause other problems if many symbols end up
18854 @item unknown symbol type @code{0x@var{nn}}
18856 The symbol information contains new data types that @value{GDBN} does
18857 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
18858 uncomprehended information, in hexadecimal.
18860 @value{GDBN} circumvents the error by ignoring this symbol information.
18861 This usually allows you to debug your program, though certain symbols
18862 are not accessible. If you encounter such a problem and feel like
18863 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
18864 on @code{complain}, then go up to the function @code{read_dbx_symtab}
18865 and examine @code{*bufp} to see the symbol.
18867 @item stub type has NULL name
18869 @value{GDBN} could not find the full definition for a struct or class.
18871 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
18872 The symbol information for a C@t{++} member function is missing some
18873 information that recent versions of the compiler should have output for
18876 @item info mismatch between compiler and debugger
18878 @value{GDBN} could not parse a type specification output by the compiler.
18883 @section GDB Data Files
18885 @cindex prefix for data files
18886 @value{GDBN} will sometimes read an auxiliary data file. These files
18887 are kept in a directory known as the @dfn{data directory}.
18889 You can set the data directory's name, and view the name @value{GDBN}
18890 is currently using.
18893 @kindex set data-directory
18894 @item set data-directory @var{directory}
18895 Set the directory which @value{GDBN} searches for auxiliary data files
18896 to @var{directory}.
18898 @kindex show data-directory
18899 @item show data-directory
18900 Show the directory @value{GDBN} searches for auxiliary data files.
18903 @cindex default data directory
18904 @cindex @samp{--with-gdb-datadir}
18905 You can set the default data directory by using the configure-time
18906 @samp{--with-gdb-datadir} option. If the data directory is inside
18907 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
18908 @samp{--exec-prefix}), then the default data directory will be updated
18909 automatically if the installed @value{GDBN} is moved to a new
18912 The data directory may also be specified with the
18913 @code{--data-directory} command line option.
18914 @xref{Mode Options}.
18917 @chapter Specifying a Debugging Target
18919 @cindex debugging target
18920 A @dfn{target} is the execution environment occupied by your program.
18922 Often, @value{GDBN} runs in the same host environment as your program;
18923 in that case, the debugging target is specified as a side effect when
18924 you use the @code{file} or @code{core} commands. When you need more
18925 flexibility---for example, running @value{GDBN} on a physically separate
18926 host, or controlling a standalone system over a serial port or a
18927 realtime system over a TCP/IP connection---you can use the @code{target}
18928 command to specify one of the target types configured for @value{GDBN}
18929 (@pxref{Target Commands, ,Commands for Managing Targets}).
18931 @cindex target architecture
18932 It is possible to build @value{GDBN} for several different @dfn{target
18933 architectures}. When @value{GDBN} is built like that, you can choose
18934 one of the available architectures with the @kbd{set architecture}
18938 @kindex set architecture
18939 @kindex show architecture
18940 @item set architecture @var{arch}
18941 This command sets the current target architecture to @var{arch}. The
18942 value of @var{arch} can be @code{"auto"}, in addition to one of the
18943 supported architectures.
18945 @item show architecture
18946 Show the current target architecture.
18948 @item set processor
18950 @kindex set processor
18951 @kindex show processor
18952 These are alias commands for, respectively, @code{set architecture}
18953 and @code{show architecture}.
18957 * Active Targets:: Active targets
18958 * Target Commands:: Commands for managing targets
18959 * Byte Order:: Choosing target byte order
18962 @node Active Targets
18963 @section Active Targets
18965 @cindex stacking targets
18966 @cindex active targets
18967 @cindex multiple targets
18969 There are multiple classes of targets such as: processes, executable files or
18970 recording sessions. Core files belong to the process class, making core file
18971 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
18972 on multiple active targets, one in each class. This allows you to (for
18973 example) start a process and inspect its activity, while still having access to
18974 the executable file after the process finishes. Or if you start process
18975 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
18976 presented a virtual layer of the recording target, while the process target
18977 remains stopped at the chronologically last point of the process execution.
18979 Use the @code{core-file} and @code{exec-file} commands to select a new core
18980 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
18981 specify as a target a process that is already running, use the @code{attach}
18982 command (@pxref{Attach, ,Debugging an Already-running Process}).
18984 @node Target Commands
18985 @section Commands for Managing Targets
18988 @item target @var{type} @var{parameters}
18989 Connects the @value{GDBN} host environment to a target machine or
18990 process. A target is typically a protocol for talking to debugging
18991 facilities. You use the argument @var{type} to specify the type or
18992 protocol of the target machine.
18994 Further @var{parameters} are interpreted by the target protocol, but
18995 typically include things like device names or host names to connect
18996 with, process numbers, and baud rates.
18998 The @code{target} command does not repeat if you press @key{RET} again
18999 after executing the command.
19001 @kindex help target
19003 Displays the names of all targets available. To display targets
19004 currently selected, use either @code{info target} or @code{info files}
19005 (@pxref{Files, ,Commands to Specify Files}).
19007 @item help target @var{name}
19008 Describe a particular target, including any parameters necessary to
19011 @kindex set gnutarget
19012 @item set gnutarget @var{args}
19013 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
19014 knows whether it is reading an @dfn{executable},
19015 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
19016 with the @code{set gnutarget} command. Unlike most @code{target} commands,
19017 with @code{gnutarget} the @code{target} refers to a program, not a machine.
19020 @emph{Warning:} To specify a file format with @code{set gnutarget},
19021 you must know the actual BFD name.
19025 @xref{Files, , Commands to Specify Files}.
19027 @kindex show gnutarget
19028 @item show gnutarget
19029 Use the @code{show gnutarget} command to display what file format
19030 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
19031 @value{GDBN} will determine the file format for each file automatically,
19032 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
19035 @cindex common targets
19036 Here are some common targets (available, or not, depending on the GDB
19041 @item target exec @var{program}
19042 @cindex executable file target
19043 An executable file. @samp{target exec @var{program}} is the same as
19044 @samp{exec-file @var{program}}.
19046 @item target core @var{filename}
19047 @cindex core dump file target
19048 A core dump file. @samp{target core @var{filename}} is the same as
19049 @samp{core-file @var{filename}}.
19051 @item target remote @var{medium}
19052 @cindex remote target
19053 A remote system connected to @value{GDBN} via a serial line or network
19054 connection. This command tells @value{GDBN} to use its own remote
19055 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
19057 For example, if you have a board connected to @file{/dev/ttya} on the
19058 machine running @value{GDBN}, you could say:
19061 target remote /dev/ttya
19064 @code{target remote} supports the @code{load} command. This is only
19065 useful if you have some other way of getting the stub to the target
19066 system, and you can put it somewhere in memory where it won't get
19067 clobbered by the download.
19069 @item target sim @r{[}@var{simargs}@r{]} @dots{}
19070 @cindex built-in simulator target
19071 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
19079 works; however, you cannot assume that a specific memory map, device
19080 drivers, or even basic I/O is available, although some simulators do
19081 provide these. For info about any processor-specific simulator details,
19082 see the appropriate section in @ref{Embedded Processors, ,Embedded
19085 @item target native
19086 @cindex native target
19087 Setup for local/native process debugging. Useful to make the
19088 @code{run} command spawn native processes (likewise @code{attach},
19089 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
19090 (@pxref{set auto-connect-native-target}).
19094 Different targets are available on different configurations of @value{GDBN};
19095 your configuration may have more or fewer targets.
19097 Many remote targets require you to download the executable's code once
19098 you've successfully established a connection. You may wish to control
19099 various aspects of this process.
19104 @kindex set hash@r{, for remote monitors}
19105 @cindex hash mark while downloading
19106 This command controls whether a hash mark @samp{#} is displayed while
19107 downloading a file to the remote monitor. If on, a hash mark is
19108 displayed after each S-record is successfully downloaded to the
19112 @kindex show hash@r{, for remote monitors}
19113 Show the current status of displaying the hash mark.
19115 @item set debug monitor
19116 @kindex set debug monitor
19117 @cindex display remote monitor communications
19118 Enable or disable display of communications messages between
19119 @value{GDBN} and the remote monitor.
19121 @item show debug monitor
19122 @kindex show debug monitor
19123 Show the current status of displaying communications between
19124 @value{GDBN} and the remote monitor.
19129 @kindex load @var{filename}
19130 @item load @var{filename}
19132 Depending on what remote debugging facilities are configured into
19133 @value{GDBN}, the @code{load} command may be available. Where it exists, it
19134 is meant to make @var{filename} (an executable) available for debugging
19135 on the remote system---by downloading, or dynamic linking, for example.
19136 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
19137 the @code{add-symbol-file} command.
19139 If your @value{GDBN} does not have a @code{load} command, attempting to
19140 execute it gets the error message ``@code{You can't do that when your
19141 target is @dots{}}''
19143 The file is loaded at whatever address is specified in the executable.
19144 For some object file formats, you can specify the load address when you
19145 link the program; for other formats, like a.out, the object file format
19146 specifies a fixed address.
19147 @c FIXME! This would be a good place for an xref to the GNU linker doc.
19149 Depending on the remote side capabilities, @value{GDBN} may be able to
19150 load programs into flash memory.
19152 @code{load} does not repeat if you press @key{RET} again after using it.
19156 @section Choosing Target Byte Order
19158 @cindex choosing target byte order
19159 @cindex target byte order
19161 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
19162 offer the ability to run either big-endian or little-endian byte
19163 orders. Usually the executable or symbol will include a bit to
19164 designate the endian-ness, and you will not need to worry about
19165 which to use. However, you may still find it useful to adjust
19166 @value{GDBN}'s idea of processor endian-ness manually.
19170 @item set endian big
19171 Instruct @value{GDBN} to assume the target is big-endian.
19173 @item set endian little
19174 Instruct @value{GDBN} to assume the target is little-endian.
19176 @item set endian auto
19177 Instruct @value{GDBN} to use the byte order associated with the
19181 Display @value{GDBN}'s current idea of the target byte order.
19185 Note that these commands merely adjust interpretation of symbolic
19186 data on the host, and that they have absolutely no effect on the
19190 @node Remote Debugging
19191 @chapter Debugging Remote Programs
19192 @cindex remote debugging
19194 If you are trying to debug a program running on a machine that cannot run
19195 @value{GDBN} in the usual way, it is often useful to use remote debugging.
19196 For example, you might use remote debugging on an operating system kernel,
19197 or on a small system which does not have a general purpose operating system
19198 powerful enough to run a full-featured debugger.
19200 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
19201 to make this work with particular debugging targets. In addition,
19202 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
19203 but not specific to any particular target system) which you can use if you
19204 write the remote stubs---the code that runs on the remote system to
19205 communicate with @value{GDBN}.
19207 Other remote targets may be available in your
19208 configuration of @value{GDBN}; use @code{help target} to list them.
19211 * Connecting:: Connecting to a remote target
19212 * File Transfer:: Sending files to a remote system
19213 * Server:: Using the gdbserver program
19214 * Remote Configuration:: Remote configuration
19215 * Remote Stub:: Implementing a remote stub
19219 @section Connecting to a Remote Target
19221 @value{GDBN} needs an unstripped copy of your program to access symbol
19222 and debugging information. Some remote targets (@pxref{qXfer
19223 executable filename read}, and @pxref{Host I/O Packets}) allow
19224 @value{GDBN} to access program files over the same connection used to
19225 communicate with @value{GDBN}. With such a target, if the remote
19226 program is unstripped, the only command you need is @code{target
19227 remote}. Otherwise, start up @value{GDBN} using the name of the local
19228 unstripped copy of your program as the first argument, or use the
19229 @code{file} command.
19231 @cindex @code{target remote}
19232 @value{GDBN} can communicate with the target over a serial line, or
19233 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
19234 each case, @value{GDBN} uses the same protocol for debugging your
19235 program; only the medium carrying the debugging packets varies. The
19236 @code{target remote} command establishes a connection to the target.
19237 Its arguments indicate which medium to use:
19241 @item target remote @var{serial-device}
19242 @cindex serial line, @code{target remote}
19243 Use @var{serial-device} to communicate with the target. For example,
19244 to use a serial line connected to the device named @file{/dev/ttyb}:
19247 target remote /dev/ttyb
19250 If you're using a serial line, you may want to give @value{GDBN} the
19251 @samp{--baud} option, or use the @code{set serial baud} command
19252 (@pxref{Remote Configuration, set serial baud}) before the
19253 @code{target} command.
19255 @item target remote @code{@var{host}:@var{port}}
19256 @itemx target remote @code{tcp:@var{host}:@var{port}}
19257 @cindex @acronym{TCP} port, @code{target remote}
19258 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
19259 The @var{host} may be either a host name or a numeric @acronym{IP}
19260 address; @var{port} must be a decimal number. The @var{host} could be
19261 the target machine itself, if it is directly connected to the net, or
19262 it might be a terminal server which in turn has a serial line to the
19265 For example, to connect to port 2828 on a terminal server named
19269 target remote manyfarms:2828
19272 If your remote target is actually running on the same machine as your
19273 debugger session (e.g.@: a simulator for your target running on the
19274 same host), you can omit the hostname. For example, to connect to
19275 port 1234 on your local machine:
19278 target remote :1234
19282 Note that the colon is still required here.
19284 @item target remote @code{udp:@var{host}:@var{port}}
19285 @cindex @acronym{UDP} port, @code{target remote}
19286 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
19287 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
19290 target remote udp:manyfarms:2828
19293 When using a @acronym{UDP} connection for remote debugging, you should
19294 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
19295 can silently drop packets on busy or unreliable networks, which will
19296 cause havoc with your debugging session.
19298 @item target remote | @var{command}
19299 @cindex pipe, @code{target remote} to
19300 Run @var{command} in the background and communicate with it using a
19301 pipe. The @var{command} is a shell command, to be parsed and expanded
19302 by the system's command shell, @code{/bin/sh}; it should expect remote
19303 protocol packets on its standard input, and send replies on its
19304 standard output. You could use this to run a stand-alone simulator
19305 that speaks the remote debugging protocol, to make net connections
19306 using programs like @code{ssh}, or for other similar tricks.
19308 If @var{command} closes its standard output (perhaps by exiting),
19309 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
19310 program has already exited, this will have no effect.)
19314 Once the connection has been established, you can use all the usual
19315 commands to examine and change data. The remote program is already
19316 running; you can use @kbd{step} and @kbd{continue}, and you do not
19317 need to use @kbd{run}.
19319 @cindex interrupting remote programs
19320 @cindex remote programs, interrupting
19321 Whenever @value{GDBN} is waiting for the remote program, if you type the
19322 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
19323 program. This may or may not succeed, depending in part on the hardware
19324 and the serial drivers the remote system uses. If you type the
19325 interrupt character once again, @value{GDBN} displays this prompt:
19328 Interrupted while waiting for the program.
19329 Give up (and stop debugging it)? (y or n)
19332 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
19333 (If you decide you want to try again later, you can use @samp{target
19334 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
19335 goes back to waiting.
19338 @kindex detach (remote)
19340 When you have finished debugging the remote program, you can use the
19341 @code{detach} command to release it from @value{GDBN} control.
19342 Detaching from the target normally resumes its execution, but the results
19343 will depend on your particular remote stub. After the @code{detach}
19344 command, @value{GDBN} is free to connect to another target.
19348 The @code{disconnect} command behaves like @code{detach}, except that
19349 the target is generally not resumed. It will wait for @value{GDBN}
19350 (this instance or another one) to connect and continue debugging. After
19351 the @code{disconnect} command, @value{GDBN} is again free to connect to
19354 @cindex send command to remote monitor
19355 @cindex extend @value{GDBN} for remote targets
19356 @cindex add new commands for external monitor
19358 @item monitor @var{cmd}
19359 This command allows you to send arbitrary commands directly to the
19360 remote monitor. Since @value{GDBN} doesn't care about the commands it
19361 sends like this, this command is the way to extend @value{GDBN}---you
19362 can add new commands that only the external monitor will understand
19366 @node File Transfer
19367 @section Sending files to a remote system
19368 @cindex remote target, file transfer
19369 @cindex file transfer
19370 @cindex sending files to remote systems
19372 Some remote targets offer the ability to transfer files over the same
19373 connection used to communicate with @value{GDBN}. This is convenient
19374 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
19375 running @code{gdbserver} over a network interface. For other targets,
19376 e.g.@: embedded devices with only a single serial port, this may be
19377 the only way to upload or download files.
19379 Not all remote targets support these commands.
19383 @item remote put @var{hostfile} @var{targetfile}
19384 Copy file @var{hostfile} from the host system (the machine running
19385 @value{GDBN}) to @var{targetfile} on the target system.
19388 @item remote get @var{targetfile} @var{hostfile}
19389 Copy file @var{targetfile} from the target system to @var{hostfile}
19390 on the host system.
19392 @kindex remote delete
19393 @item remote delete @var{targetfile}
19394 Delete @var{targetfile} from the target system.
19399 @section Using the @code{gdbserver} Program
19402 @cindex remote connection without stubs
19403 @code{gdbserver} is a control program for Unix-like systems, which
19404 allows you to connect your program with a remote @value{GDBN} via
19405 @code{target remote}---but without linking in the usual debugging stub.
19407 @code{gdbserver} is not a complete replacement for the debugging stubs,
19408 because it requires essentially the same operating-system facilities
19409 that @value{GDBN} itself does. In fact, a system that can run
19410 @code{gdbserver} to connect to a remote @value{GDBN} could also run
19411 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
19412 because it is a much smaller program than @value{GDBN} itself. It is
19413 also easier to port than all of @value{GDBN}, so you may be able to get
19414 started more quickly on a new system by using @code{gdbserver}.
19415 Finally, if you develop code for real-time systems, you may find that
19416 the tradeoffs involved in real-time operation make it more convenient to
19417 do as much development work as possible on another system, for example
19418 by cross-compiling. You can use @code{gdbserver} to make a similar
19419 choice for debugging.
19421 @value{GDBN} and @code{gdbserver} communicate via either a serial line
19422 or a TCP connection, using the standard @value{GDBN} remote serial
19426 @emph{Warning:} @code{gdbserver} does not have any built-in security.
19427 Do not run @code{gdbserver} connected to any public network; a
19428 @value{GDBN} connection to @code{gdbserver} provides access to the
19429 target system with the same privileges as the user running
19433 @subsection Running @code{gdbserver}
19434 @cindex arguments, to @code{gdbserver}
19435 @cindex @code{gdbserver}, command-line arguments
19437 Run @code{gdbserver} on the target system. You need a copy of the
19438 program you want to debug, including any libraries it requires.
19439 @code{gdbserver} does not need your program's symbol table, so you can
19440 strip the program if necessary to save space. @value{GDBN} on the host
19441 system does all the symbol handling.
19443 To use the server, you must tell it how to communicate with @value{GDBN};
19444 the name of your program; and the arguments for your program. The usual
19448 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
19451 @var{comm} is either a device name (to use a serial line), or a TCP
19452 hostname and portnumber, or @code{-} or @code{stdio} to use
19453 stdin/stdout of @code{gdbserver}.
19454 For example, to debug Emacs with the argument
19455 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
19459 target> gdbserver /dev/com1 emacs foo.txt
19462 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
19465 To use a TCP connection instead of a serial line:
19468 target> gdbserver host:2345 emacs foo.txt
19471 The only difference from the previous example is the first argument,
19472 specifying that you are communicating with the host @value{GDBN} via
19473 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
19474 expect a TCP connection from machine @samp{host} to local TCP port 2345.
19475 (Currently, the @samp{host} part is ignored.) You can choose any number
19476 you want for the port number as long as it does not conflict with any
19477 TCP ports already in use on the target system (for example, @code{23} is
19478 reserved for @code{telnet}).@footnote{If you choose a port number that
19479 conflicts with another service, @code{gdbserver} prints an error message
19480 and exits.} You must use the same port number with the host @value{GDBN}
19481 @code{target remote} command.
19483 The @code{stdio} connection is useful when starting @code{gdbserver}
19487 (gdb) target remote | ssh -T hostname gdbserver - hello
19490 The @samp{-T} option to ssh is provided because we don't need a remote pty,
19491 and we don't want escape-character handling. Ssh does this by default when
19492 a command is provided, the flag is provided to make it explicit.
19493 You could elide it if you want to.
19495 Programs started with stdio-connected gdbserver have @file{/dev/null} for
19496 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
19497 display through a pipe connected to gdbserver.
19498 Both @code{stdout} and @code{stderr} use the same pipe.
19500 @subsubsection Attaching to a Running Program
19501 @cindex attach to a program, @code{gdbserver}
19502 @cindex @option{--attach}, @code{gdbserver} option
19504 On some targets, @code{gdbserver} can also attach to running programs.
19505 This is accomplished via the @code{--attach} argument. The syntax is:
19508 target> gdbserver --attach @var{comm} @var{pid}
19511 @var{pid} is the process ID of a currently running process. It isn't necessary
19512 to point @code{gdbserver} at a binary for the running process.
19515 You can debug processes by name instead of process ID if your target has the
19516 @code{pidof} utility:
19519 target> gdbserver --attach @var{comm} `pidof @var{program}`
19522 In case more than one copy of @var{program} is running, or @var{program}
19523 has multiple threads, most versions of @code{pidof} support the
19524 @code{-s} option to only return the first process ID.
19526 @subsubsection Multi-Process Mode for @code{gdbserver}
19527 @cindex @code{gdbserver}, multiple processes
19528 @cindex multiple processes with @code{gdbserver}
19530 When you connect to @code{gdbserver} using @code{target remote},
19531 @code{gdbserver} debugs the specified program only once. When the
19532 program exits, or you detach from it, @value{GDBN} closes the connection
19533 and @code{gdbserver} exits.
19535 If you connect using @kbd{target extended-remote}, @code{gdbserver}
19536 enters multi-process mode. When the debugged program exits, or you
19537 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
19538 though no program is running. The @code{run} and @code{attach}
19539 commands instruct @code{gdbserver} to run or attach to a new program.
19540 The @code{run} command uses @code{set remote exec-file} (@pxref{set
19541 remote exec-file}) to select the program to run. Command line
19542 arguments are supported, except for wildcard expansion and I/O
19543 redirection (@pxref{Arguments}).
19545 @cindex @option{--multi}, @code{gdbserver} option
19546 To start @code{gdbserver} without supplying an initial command to run
19547 or process ID to attach, use the @option{--multi} command line option.
19548 Then you can connect using @kbd{target extended-remote} and start
19549 the program you want to debug.
19551 In multi-process mode @code{gdbserver} does not automatically exit unless you
19552 use the option @option{--once}. You can terminate it by using
19553 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
19554 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
19555 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
19556 @option{--multi} option to @code{gdbserver} has no influence on that.
19558 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
19560 This section applies only when @code{gdbserver} is run to listen on a TCP port.
19562 @code{gdbserver} normally terminates after all of its debugged processes have
19563 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
19564 extended-remote}, @code{gdbserver} stays running even with no processes left.
19565 @value{GDBN} normally terminates the spawned debugged process on its exit,
19566 which normally also terminates @code{gdbserver} in the @kbd{target remote}
19567 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
19568 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
19569 stays running even in the @kbd{target remote} mode.
19571 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
19572 Such reconnecting is useful for features like @ref{disconnected tracing}. For
19573 completeness, at most one @value{GDBN} can be connected at a time.
19575 @cindex @option{--once}, @code{gdbserver} option
19576 By default, @code{gdbserver} keeps the listening TCP port open, so that
19577 subsequent connections are possible. However, if you start @code{gdbserver}
19578 with the @option{--once} option, it will stop listening for any further
19579 connection attempts after connecting to the first @value{GDBN} session. This
19580 means no further connections to @code{gdbserver} will be possible after the
19581 first one. It also means @code{gdbserver} will terminate after the first
19582 connection with remote @value{GDBN} has closed, even for unexpectedly closed
19583 connections and even in the @kbd{target extended-remote} mode. The
19584 @option{--once} option allows reusing the same port number for connecting to
19585 multiple instances of @code{gdbserver} running on the same host, since each
19586 instance closes its port after the first connection.
19588 @anchor{Other Command-Line Arguments for gdbserver}
19589 @subsubsection Other Command-Line Arguments for @code{gdbserver}
19591 @cindex @option{--debug}, @code{gdbserver} option
19592 The @option{--debug} option tells @code{gdbserver} to display extra
19593 status information about the debugging process.
19594 @cindex @option{--remote-debug}, @code{gdbserver} option
19595 The @option{--remote-debug} option tells @code{gdbserver} to display
19596 remote protocol debug output. These options are intended for
19597 @code{gdbserver} development and for bug reports to the developers.
19599 @cindex @option{--debug-format}, @code{gdbserver} option
19600 The @option{--debug-format=option1[,option2,...]} option tells
19601 @code{gdbserver} to include additional information in each output.
19602 Possible options are:
19606 Turn off all extra information in debugging output.
19608 Turn on all extra information in debugging output.
19610 Include a timestamp in each line of debugging output.
19613 Options are processed in order. Thus, for example, if @option{none}
19614 appears last then no additional information is added to debugging output.
19616 @cindex @option{--wrapper}, @code{gdbserver} option
19617 The @option{--wrapper} option specifies a wrapper to launch programs
19618 for debugging. The option should be followed by the name of the
19619 wrapper, then any command-line arguments to pass to the wrapper, then
19620 @kbd{--} indicating the end of the wrapper arguments.
19622 @code{gdbserver} runs the specified wrapper program with a combined
19623 command line including the wrapper arguments, then the name of the
19624 program to debug, then any arguments to the program. The wrapper
19625 runs until it executes your program, and then @value{GDBN} gains control.
19627 You can use any program that eventually calls @code{execve} with
19628 its arguments as a wrapper. Several standard Unix utilities do
19629 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
19630 with @code{exec "$@@"} will also work.
19632 For example, you can use @code{env} to pass an environment variable to
19633 the debugged program, without setting the variable in @code{gdbserver}'s
19637 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
19640 @subsection Connecting to @code{gdbserver}
19642 Run @value{GDBN} on the host system.
19644 First make sure you have the necessary symbol files. Load symbols for
19645 your application using the @code{file} command before you connect. Use
19646 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
19647 was compiled with the correct sysroot using @code{--with-sysroot}).
19649 The symbol file and target libraries must exactly match the executable
19650 and libraries on the target, with one exception: the files on the host
19651 system should not be stripped, even if the files on the target system
19652 are. Mismatched or missing files will lead to confusing results
19653 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
19654 files may also prevent @code{gdbserver} from debugging multi-threaded
19657 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
19658 For TCP connections, you must start up @code{gdbserver} prior to using
19659 the @code{target remote} command. Otherwise you may get an error whose
19660 text depends on the host system, but which usually looks something like
19661 @samp{Connection refused}. Don't use the @code{load}
19662 command in @value{GDBN} when using @code{gdbserver}, since the program is
19663 already on the target.
19665 @subsection Monitor Commands for @code{gdbserver}
19666 @cindex monitor commands, for @code{gdbserver}
19667 @anchor{Monitor Commands for gdbserver}
19669 During a @value{GDBN} session using @code{gdbserver}, you can use the
19670 @code{monitor} command to send special requests to @code{gdbserver}.
19671 Here are the available commands.
19675 List the available monitor commands.
19677 @item monitor set debug 0
19678 @itemx monitor set debug 1
19679 Disable or enable general debugging messages.
19681 @item monitor set remote-debug 0
19682 @itemx monitor set remote-debug 1
19683 Disable or enable specific debugging messages associated with the remote
19684 protocol (@pxref{Remote Protocol}).
19686 @item monitor set debug-format option1@r{[},option2,...@r{]}
19687 Specify additional text to add to debugging messages.
19688 Possible options are:
19692 Turn off all extra information in debugging output.
19694 Turn on all extra information in debugging output.
19696 Include a timestamp in each line of debugging output.
19699 Options are processed in order. Thus, for example, if @option{none}
19700 appears last then no additional information is added to debugging output.
19702 @item monitor set libthread-db-search-path [PATH]
19703 @cindex gdbserver, search path for @code{libthread_db}
19704 When this command is issued, @var{path} is a colon-separated list of
19705 directories to search for @code{libthread_db} (@pxref{Threads,,set
19706 libthread-db-search-path}). If you omit @var{path},
19707 @samp{libthread-db-search-path} will be reset to its default value.
19709 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
19710 not supported in @code{gdbserver}.
19713 Tell gdbserver to exit immediately. This command should be followed by
19714 @code{disconnect} to close the debugging session. @code{gdbserver} will
19715 detach from any attached processes and kill any processes it created.
19716 Use @code{monitor exit} to terminate @code{gdbserver} at the end
19717 of a multi-process mode debug session.
19721 @subsection Tracepoints support in @code{gdbserver}
19722 @cindex tracepoints support in @code{gdbserver}
19724 On some targets, @code{gdbserver} supports tracepoints, fast
19725 tracepoints and static tracepoints.
19727 For fast or static tracepoints to work, a special library called the
19728 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
19729 This library is built and distributed as an integral part of
19730 @code{gdbserver}. In addition, support for static tracepoints
19731 requires building the in-process agent library with static tracepoints
19732 support. At present, the UST (LTTng Userspace Tracer,
19733 @url{http://lttng.org/ust}) tracing engine is supported. This support
19734 is automatically available if UST development headers are found in the
19735 standard include path when @code{gdbserver} is built, or if
19736 @code{gdbserver} was explicitly configured using @option{--with-ust}
19737 to point at such headers. You can explicitly disable the support
19738 using @option{--with-ust=no}.
19740 There are several ways to load the in-process agent in your program:
19743 @item Specifying it as dependency at link time
19745 You can link your program dynamically with the in-process agent
19746 library. On most systems, this is accomplished by adding
19747 @code{-linproctrace} to the link command.
19749 @item Using the system's preloading mechanisms
19751 You can force loading the in-process agent at startup time by using
19752 your system's support for preloading shared libraries. Many Unixes
19753 support the concept of preloading user defined libraries. In most
19754 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
19755 in the environment. See also the description of @code{gdbserver}'s
19756 @option{--wrapper} command line option.
19758 @item Using @value{GDBN} to force loading the agent at run time
19760 On some systems, you can force the inferior to load a shared library,
19761 by calling a dynamic loader function in the inferior that takes care
19762 of dynamically looking up and loading a shared library. On most Unix
19763 systems, the function is @code{dlopen}. You'll use the @code{call}
19764 command for that. For example:
19767 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
19770 Note that on most Unix systems, for the @code{dlopen} function to be
19771 available, the program needs to be linked with @code{-ldl}.
19774 On systems that have a userspace dynamic loader, like most Unix
19775 systems, when you connect to @code{gdbserver} using @code{target
19776 remote}, you'll find that the program is stopped at the dynamic
19777 loader's entry point, and no shared library has been loaded in the
19778 program's address space yet, including the in-process agent. In that
19779 case, before being able to use any of the fast or static tracepoints
19780 features, you need to let the loader run and load the shared
19781 libraries. The simplest way to do that is to run the program to the
19782 main procedure. E.g., if debugging a C or C@t{++} program, start
19783 @code{gdbserver} like so:
19786 $ gdbserver :9999 myprogram
19789 Start GDB and connect to @code{gdbserver} like so, and run to main:
19793 (@value{GDBP}) target remote myhost:9999
19794 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
19795 (@value{GDBP}) b main
19796 (@value{GDBP}) continue
19799 The in-process tracing agent library should now be loaded into the
19800 process; you can confirm it with the @code{info sharedlibrary}
19801 command, which will list @file{libinproctrace.so} as loaded in the
19802 process. You are now ready to install fast tracepoints, list static
19803 tracepoint markers, probe static tracepoints markers, and start
19806 @node Remote Configuration
19807 @section Remote Configuration
19810 @kindex show remote
19811 This section documents the configuration options available when
19812 debugging remote programs. For the options related to the File I/O
19813 extensions of the remote protocol, see @ref{system,
19814 system-call-allowed}.
19817 @item set remoteaddresssize @var{bits}
19818 @cindex address size for remote targets
19819 @cindex bits in remote address
19820 Set the maximum size of address in a memory packet to the specified
19821 number of bits. @value{GDBN} will mask off the address bits above
19822 that number, when it passes addresses to the remote target. The
19823 default value is the number of bits in the target's address.
19825 @item show remoteaddresssize
19826 Show the current value of remote address size in bits.
19828 @item set serial baud @var{n}
19829 @cindex baud rate for remote targets
19830 Set the baud rate for the remote serial I/O to @var{n} baud. The
19831 value is used to set the speed of the serial port used for debugging
19834 @item show serial baud
19835 Show the current speed of the remote connection.
19837 @item set serial parity @var{parity}
19838 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
19839 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
19841 @item show serial parity
19842 Show the current parity of the serial port.
19844 @item set remotebreak
19845 @cindex interrupt remote programs
19846 @cindex BREAK signal instead of Ctrl-C
19847 @anchor{set remotebreak}
19848 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
19849 when you type @kbd{Ctrl-c} to interrupt the program running
19850 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
19851 character instead. The default is off, since most remote systems
19852 expect to see @samp{Ctrl-C} as the interrupt signal.
19854 @item show remotebreak
19855 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
19856 interrupt the remote program.
19858 @item set remoteflow on
19859 @itemx set remoteflow off
19860 @kindex set remoteflow
19861 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
19862 on the serial port used to communicate to the remote target.
19864 @item show remoteflow
19865 @kindex show remoteflow
19866 Show the current setting of hardware flow control.
19868 @item set remotelogbase @var{base}
19869 Set the base (a.k.a.@: radix) of logging serial protocol
19870 communications to @var{base}. Supported values of @var{base} are:
19871 @code{ascii}, @code{octal}, and @code{hex}. The default is
19874 @item show remotelogbase
19875 Show the current setting of the radix for logging remote serial
19878 @item set remotelogfile @var{file}
19879 @cindex record serial communications on file
19880 Record remote serial communications on the named @var{file}. The
19881 default is not to record at all.
19883 @item show remotelogfile.
19884 Show the current setting of the file name on which to record the
19885 serial communications.
19887 @item set remotetimeout @var{num}
19888 @cindex timeout for serial communications
19889 @cindex remote timeout
19890 Set the timeout limit to wait for the remote target to respond to
19891 @var{num} seconds. The default is 2 seconds.
19893 @item show remotetimeout
19894 Show the current number of seconds to wait for the remote target
19897 @cindex limit hardware breakpoints and watchpoints
19898 @cindex remote target, limit break- and watchpoints
19899 @anchor{set remote hardware-watchpoint-limit}
19900 @anchor{set remote hardware-breakpoint-limit}
19901 @item set remote hardware-watchpoint-limit @var{limit}
19902 @itemx set remote hardware-breakpoint-limit @var{limit}
19903 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
19904 watchpoints. A limit of -1, the default, is treated as unlimited.
19906 @cindex limit hardware watchpoints length
19907 @cindex remote target, limit watchpoints length
19908 @anchor{set remote hardware-watchpoint-length-limit}
19909 @item set remote hardware-watchpoint-length-limit @var{limit}
19910 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
19911 a remote hardware watchpoint. A limit of -1, the default, is treated
19914 @item show remote hardware-watchpoint-length-limit
19915 Show the current limit (in bytes) of the maximum length of
19916 a remote hardware watchpoint.
19918 @item set remote exec-file @var{filename}
19919 @itemx show remote exec-file
19920 @anchor{set remote exec-file}
19921 @cindex executable file, for remote target
19922 Select the file used for @code{run} with @code{target
19923 extended-remote}. This should be set to a filename valid on the
19924 target system. If it is not set, the target will use a default
19925 filename (e.g.@: the last program run).
19927 @item set remote interrupt-sequence
19928 @cindex interrupt remote programs
19929 @cindex select Ctrl-C, BREAK or BREAK-g
19930 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
19931 @samp{BREAK-g} as the
19932 sequence to the remote target in order to interrupt the execution.
19933 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
19934 is high level of serial line for some certain time.
19935 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
19936 It is @code{BREAK} signal followed by character @code{g}.
19938 @item show interrupt-sequence
19939 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
19940 is sent by @value{GDBN} to interrupt the remote program.
19941 @code{BREAK-g} is BREAK signal followed by @code{g} and
19942 also known as Magic SysRq g.
19944 @item set remote interrupt-on-connect
19945 @cindex send interrupt-sequence on start
19946 Specify whether interrupt-sequence is sent to remote target when
19947 @value{GDBN} connects to it. This is mostly needed when you debug
19948 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
19949 which is known as Magic SysRq g in order to connect @value{GDBN}.
19951 @item show interrupt-on-connect
19952 Show whether interrupt-sequence is sent
19953 to remote target when @value{GDBN} connects to it.
19957 @item set tcp auto-retry on
19958 @cindex auto-retry, for remote TCP target
19959 Enable auto-retry for remote TCP connections. This is useful if the remote
19960 debugging agent is launched in parallel with @value{GDBN}; there is a race
19961 condition because the agent may not become ready to accept the connection
19962 before @value{GDBN} attempts to connect. When auto-retry is
19963 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
19964 to establish the connection using the timeout specified by
19965 @code{set tcp connect-timeout}.
19967 @item set tcp auto-retry off
19968 Do not auto-retry failed TCP connections.
19970 @item show tcp auto-retry
19971 Show the current auto-retry setting.
19973 @item set tcp connect-timeout @var{seconds}
19974 @itemx set tcp connect-timeout unlimited
19975 @cindex connection timeout, for remote TCP target
19976 @cindex timeout, for remote target connection
19977 Set the timeout for establishing a TCP connection to the remote target to
19978 @var{seconds}. The timeout affects both polling to retry failed connections
19979 (enabled by @code{set tcp auto-retry on}) and waiting for connections
19980 that are merely slow to complete, and represents an approximate cumulative
19981 value. If @var{seconds} is @code{unlimited}, there is no timeout and
19982 @value{GDBN} will keep attempting to establish a connection forever,
19983 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
19985 @item show tcp connect-timeout
19986 Show the current connection timeout setting.
19989 @cindex remote packets, enabling and disabling
19990 The @value{GDBN} remote protocol autodetects the packets supported by
19991 your debugging stub. If you need to override the autodetection, you
19992 can use these commands to enable or disable individual packets. Each
19993 packet can be set to @samp{on} (the remote target supports this
19994 packet), @samp{off} (the remote target does not support this packet),
19995 or @samp{auto} (detect remote target support for this packet). They
19996 all default to @samp{auto}. For more information about each packet,
19997 see @ref{Remote Protocol}.
19999 During normal use, you should not have to use any of these commands.
20000 If you do, that may be a bug in your remote debugging stub, or a bug
20001 in @value{GDBN}. You may want to report the problem to the
20002 @value{GDBN} developers.
20004 For each packet @var{name}, the command to enable or disable the
20005 packet is @code{set remote @var{name}-packet}. The available settings
20008 @multitable @columnfractions 0.28 0.32 0.25
20011 @tab Related Features
20013 @item @code{fetch-register}
20015 @tab @code{info registers}
20017 @item @code{set-register}
20021 @item @code{binary-download}
20023 @tab @code{load}, @code{set}
20025 @item @code{read-aux-vector}
20026 @tab @code{qXfer:auxv:read}
20027 @tab @code{info auxv}
20029 @item @code{symbol-lookup}
20030 @tab @code{qSymbol}
20031 @tab Detecting multiple threads
20033 @item @code{attach}
20034 @tab @code{vAttach}
20037 @item @code{verbose-resume}
20039 @tab Stepping or resuming multiple threads
20045 @item @code{software-breakpoint}
20049 @item @code{hardware-breakpoint}
20053 @item @code{write-watchpoint}
20057 @item @code{read-watchpoint}
20061 @item @code{access-watchpoint}
20065 @item @code{pid-to-exec-file}
20066 @tab @code{qXfer:exec-file:read}
20067 @tab @code{attach}, @code{run}
20069 @item @code{target-features}
20070 @tab @code{qXfer:features:read}
20071 @tab @code{set architecture}
20073 @item @code{library-info}
20074 @tab @code{qXfer:libraries:read}
20075 @tab @code{info sharedlibrary}
20077 @item @code{memory-map}
20078 @tab @code{qXfer:memory-map:read}
20079 @tab @code{info mem}
20081 @item @code{read-sdata-object}
20082 @tab @code{qXfer:sdata:read}
20083 @tab @code{print $_sdata}
20085 @item @code{read-spu-object}
20086 @tab @code{qXfer:spu:read}
20087 @tab @code{info spu}
20089 @item @code{write-spu-object}
20090 @tab @code{qXfer:spu:write}
20091 @tab @code{info spu}
20093 @item @code{read-siginfo-object}
20094 @tab @code{qXfer:siginfo:read}
20095 @tab @code{print $_siginfo}
20097 @item @code{write-siginfo-object}
20098 @tab @code{qXfer:siginfo:write}
20099 @tab @code{set $_siginfo}
20101 @item @code{threads}
20102 @tab @code{qXfer:threads:read}
20103 @tab @code{info threads}
20105 @item @code{get-thread-local-@*storage-address}
20106 @tab @code{qGetTLSAddr}
20107 @tab Displaying @code{__thread} variables
20109 @item @code{get-thread-information-block-address}
20110 @tab @code{qGetTIBAddr}
20111 @tab Display MS-Windows Thread Information Block.
20113 @item @code{search-memory}
20114 @tab @code{qSearch:memory}
20117 @item @code{supported-packets}
20118 @tab @code{qSupported}
20119 @tab Remote communications parameters
20121 @item @code{pass-signals}
20122 @tab @code{QPassSignals}
20123 @tab @code{handle @var{signal}}
20125 @item @code{program-signals}
20126 @tab @code{QProgramSignals}
20127 @tab @code{handle @var{signal}}
20129 @item @code{hostio-close-packet}
20130 @tab @code{vFile:close}
20131 @tab @code{remote get}, @code{remote put}
20133 @item @code{hostio-open-packet}
20134 @tab @code{vFile:open}
20135 @tab @code{remote get}, @code{remote put}
20137 @item @code{hostio-pread-packet}
20138 @tab @code{vFile:pread}
20139 @tab @code{remote get}, @code{remote put}
20141 @item @code{hostio-pwrite-packet}
20142 @tab @code{vFile:pwrite}
20143 @tab @code{remote get}, @code{remote put}
20145 @item @code{hostio-unlink-packet}
20146 @tab @code{vFile:unlink}
20147 @tab @code{remote delete}
20149 @item @code{hostio-readlink-packet}
20150 @tab @code{vFile:readlink}
20153 @item @code{hostio-fstat-packet}
20154 @tab @code{vFile:fstat}
20157 @item @code{hostio-setfs-packet}
20158 @tab @code{vFile:setfs}
20161 @item @code{noack-packet}
20162 @tab @code{QStartNoAckMode}
20163 @tab Packet acknowledgment
20165 @item @code{osdata}
20166 @tab @code{qXfer:osdata:read}
20167 @tab @code{info os}
20169 @item @code{query-attached}
20170 @tab @code{qAttached}
20171 @tab Querying remote process attach state.
20173 @item @code{trace-buffer-size}
20174 @tab @code{QTBuffer:size}
20175 @tab @code{set trace-buffer-size}
20177 @item @code{trace-status}
20178 @tab @code{qTStatus}
20179 @tab @code{tstatus}
20181 @item @code{traceframe-info}
20182 @tab @code{qXfer:traceframe-info:read}
20183 @tab Traceframe info
20185 @item @code{install-in-trace}
20186 @tab @code{InstallInTrace}
20187 @tab Install tracepoint in tracing
20189 @item @code{disable-randomization}
20190 @tab @code{QDisableRandomization}
20191 @tab @code{set disable-randomization}
20193 @item @code{conditional-breakpoints-packet}
20194 @tab @code{Z0 and Z1}
20195 @tab @code{Support for target-side breakpoint condition evaluation}
20197 @item @code{swbreak-feature}
20198 @tab @code{swbreak stop reason}
20201 @item @code{hwbreak-feature}
20202 @tab @code{hwbreak stop reason}
20205 @item @code{fork-event-feature}
20206 @tab @code{fork stop reason}
20209 @item @code{vfork-event-feature}
20210 @tab @code{vfork stop reason}
20216 @section Implementing a Remote Stub
20218 @cindex debugging stub, example
20219 @cindex remote stub, example
20220 @cindex stub example, remote debugging
20221 The stub files provided with @value{GDBN} implement the target side of the
20222 communication protocol, and the @value{GDBN} side is implemented in the
20223 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
20224 these subroutines to communicate, and ignore the details. (If you're
20225 implementing your own stub file, you can still ignore the details: start
20226 with one of the existing stub files. @file{sparc-stub.c} is the best
20227 organized, and therefore the easiest to read.)
20229 @cindex remote serial debugging, overview
20230 To debug a program running on another machine (the debugging
20231 @dfn{target} machine), you must first arrange for all the usual
20232 prerequisites for the program to run by itself. For example, for a C
20237 A startup routine to set up the C runtime environment; these usually
20238 have a name like @file{crt0}. The startup routine may be supplied by
20239 your hardware supplier, or you may have to write your own.
20242 A C subroutine library to support your program's
20243 subroutine calls, notably managing input and output.
20246 A way of getting your program to the other machine---for example, a
20247 download program. These are often supplied by the hardware
20248 manufacturer, but you may have to write your own from hardware
20252 The next step is to arrange for your program to use a serial port to
20253 communicate with the machine where @value{GDBN} is running (the @dfn{host}
20254 machine). In general terms, the scheme looks like this:
20258 @value{GDBN} already understands how to use this protocol; when everything
20259 else is set up, you can simply use the @samp{target remote} command
20260 (@pxref{Targets,,Specifying a Debugging Target}).
20262 @item On the target,
20263 you must link with your program a few special-purpose subroutines that
20264 implement the @value{GDBN} remote serial protocol. The file containing these
20265 subroutines is called a @dfn{debugging stub}.
20267 On certain remote targets, you can use an auxiliary program
20268 @code{gdbserver} instead of linking a stub into your program.
20269 @xref{Server,,Using the @code{gdbserver} Program}, for details.
20272 The debugging stub is specific to the architecture of the remote
20273 machine; for example, use @file{sparc-stub.c} to debug programs on
20276 @cindex remote serial stub list
20277 These working remote stubs are distributed with @value{GDBN}:
20282 @cindex @file{i386-stub.c}
20285 For Intel 386 and compatible architectures.
20288 @cindex @file{m68k-stub.c}
20289 @cindex Motorola 680x0
20291 For Motorola 680x0 architectures.
20294 @cindex @file{sh-stub.c}
20297 For Renesas SH architectures.
20300 @cindex @file{sparc-stub.c}
20302 For @sc{sparc} architectures.
20304 @item sparcl-stub.c
20305 @cindex @file{sparcl-stub.c}
20308 For Fujitsu @sc{sparclite} architectures.
20312 The @file{README} file in the @value{GDBN} distribution may list other
20313 recently added stubs.
20316 * Stub Contents:: What the stub can do for you
20317 * Bootstrapping:: What you must do for the stub
20318 * Debug Session:: Putting it all together
20321 @node Stub Contents
20322 @subsection What the Stub Can Do for You
20324 @cindex remote serial stub
20325 The debugging stub for your architecture supplies these three
20329 @item set_debug_traps
20330 @findex set_debug_traps
20331 @cindex remote serial stub, initialization
20332 This routine arranges for @code{handle_exception} to run when your
20333 program stops. You must call this subroutine explicitly in your
20334 program's startup code.
20336 @item handle_exception
20337 @findex handle_exception
20338 @cindex remote serial stub, main routine
20339 This is the central workhorse, but your program never calls it
20340 explicitly---the setup code arranges for @code{handle_exception} to
20341 run when a trap is triggered.
20343 @code{handle_exception} takes control when your program stops during
20344 execution (for example, on a breakpoint), and mediates communications
20345 with @value{GDBN} on the host machine. This is where the communications
20346 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
20347 representative on the target machine. It begins by sending summary
20348 information on the state of your program, then continues to execute,
20349 retrieving and transmitting any information @value{GDBN} needs, until you
20350 execute a @value{GDBN} command that makes your program resume; at that point,
20351 @code{handle_exception} returns control to your own code on the target
20355 @cindex @code{breakpoint} subroutine, remote
20356 Use this auxiliary subroutine to make your program contain a
20357 breakpoint. Depending on the particular situation, this may be the only
20358 way for @value{GDBN} to get control. For instance, if your target
20359 machine has some sort of interrupt button, you won't need to call this;
20360 pressing the interrupt button transfers control to
20361 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
20362 simply receiving characters on the serial port may also trigger a trap;
20363 again, in that situation, you don't need to call @code{breakpoint} from
20364 your own program---simply running @samp{target remote} from the host
20365 @value{GDBN} session gets control.
20367 Call @code{breakpoint} if none of these is true, or if you simply want
20368 to make certain your program stops at a predetermined point for the
20369 start of your debugging session.
20372 @node Bootstrapping
20373 @subsection What You Must Do for the Stub
20375 @cindex remote stub, support routines
20376 The debugging stubs that come with @value{GDBN} are set up for a particular
20377 chip architecture, but they have no information about the rest of your
20378 debugging target machine.
20380 First of all you need to tell the stub how to communicate with the
20384 @item int getDebugChar()
20385 @findex getDebugChar
20386 Write this subroutine to read a single character from the serial port.
20387 It may be identical to @code{getchar} for your target system; a
20388 different name is used to allow you to distinguish the two if you wish.
20390 @item void putDebugChar(int)
20391 @findex putDebugChar
20392 Write this subroutine to write a single character to the serial port.
20393 It may be identical to @code{putchar} for your target system; a
20394 different name is used to allow you to distinguish the two if you wish.
20397 @cindex control C, and remote debugging
20398 @cindex interrupting remote targets
20399 If you want @value{GDBN} to be able to stop your program while it is
20400 running, you need to use an interrupt-driven serial driver, and arrange
20401 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
20402 character). That is the character which @value{GDBN} uses to tell the
20403 remote system to stop.
20405 Getting the debugging target to return the proper status to @value{GDBN}
20406 probably requires changes to the standard stub; one quick and dirty way
20407 is to just execute a breakpoint instruction (the ``dirty'' part is that
20408 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
20410 Other routines you need to supply are:
20413 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
20414 @findex exceptionHandler
20415 Write this function to install @var{exception_address} in the exception
20416 handling tables. You need to do this because the stub does not have any
20417 way of knowing what the exception handling tables on your target system
20418 are like (for example, the processor's table might be in @sc{rom},
20419 containing entries which point to a table in @sc{ram}).
20420 The @var{exception_number} specifies the exception which should be changed;
20421 its meaning is architecture-dependent (for example, different numbers
20422 might represent divide by zero, misaligned access, etc). When this
20423 exception occurs, control should be transferred directly to
20424 @var{exception_address}, and the processor state (stack, registers,
20425 and so on) should be just as it is when a processor exception occurs. So if
20426 you want to use a jump instruction to reach @var{exception_address}, it
20427 should be a simple jump, not a jump to subroutine.
20429 For the 386, @var{exception_address} should be installed as an interrupt
20430 gate so that interrupts are masked while the handler runs. The gate
20431 should be at privilege level 0 (the most privileged level). The
20432 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
20433 help from @code{exceptionHandler}.
20435 @item void flush_i_cache()
20436 @findex flush_i_cache
20437 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
20438 instruction cache, if any, on your target machine. If there is no
20439 instruction cache, this subroutine may be a no-op.
20441 On target machines that have instruction caches, @value{GDBN} requires this
20442 function to make certain that the state of your program is stable.
20446 You must also make sure this library routine is available:
20449 @item void *memset(void *, int, int)
20451 This is the standard library function @code{memset} that sets an area of
20452 memory to a known value. If you have one of the free versions of
20453 @code{libc.a}, @code{memset} can be found there; otherwise, you must
20454 either obtain it from your hardware manufacturer, or write your own.
20457 If you do not use the GNU C compiler, you may need other standard
20458 library subroutines as well; this varies from one stub to another,
20459 but in general the stubs are likely to use any of the common library
20460 subroutines which @code{@value{NGCC}} generates as inline code.
20463 @node Debug Session
20464 @subsection Putting it All Together
20466 @cindex remote serial debugging summary
20467 In summary, when your program is ready to debug, you must follow these
20472 Make sure you have defined the supporting low-level routines
20473 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
20475 @code{getDebugChar}, @code{putDebugChar},
20476 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
20480 Insert these lines in your program's startup code, before the main
20481 procedure is called:
20488 On some machines, when a breakpoint trap is raised, the hardware
20489 automatically makes the PC point to the instruction after the
20490 breakpoint. If your machine doesn't do that, you may need to adjust
20491 @code{handle_exception} to arrange for it to return to the instruction
20492 after the breakpoint on this first invocation, so that your program
20493 doesn't keep hitting the initial breakpoint instead of making
20497 For the 680x0 stub only, you need to provide a variable called
20498 @code{exceptionHook}. Normally you just use:
20501 void (*exceptionHook)() = 0;
20505 but if before calling @code{set_debug_traps}, you set it to point to a
20506 function in your program, that function is called when
20507 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
20508 error). The function indicated by @code{exceptionHook} is called with
20509 one parameter: an @code{int} which is the exception number.
20512 Compile and link together: your program, the @value{GDBN} debugging stub for
20513 your target architecture, and the supporting subroutines.
20516 Make sure you have a serial connection between your target machine and
20517 the @value{GDBN} host, and identify the serial port on the host.
20520 @c The "remote" target now provides a `load' command, so we should
20521 @c document that. FIXME.
20522 Download your program to your target machine (or get it there by
20523 whatever means the manufacturer provides), and start it.
20526 Start @value{GDBN} on the host, and connect to the target
20527 (@pxref{Connecting,,Connecting to a Remote Target}).
20531 @node Configurations
20532 @chapter Configuration-Specific Information
20534 While nearly all @value{GDBN} commands are available for all native and
20535 cross versions of the debugger, there are some exceptions. This chapter
20536 describes things that are only available in certain configurations.
20538 There are three major categories of configurations: native
20539 configurations, where the host and target are the same, embedded
20540 operating system configurations, which are usually the same for several
20541 different processor architectures, and bare embedded processors, which
20542 are quite different from each other.
20547 * Embedded Processors::
20554 This section describes details specific to particular native
20559 * BSD libkvm Interface:: Debugging BSD kernel memory images
20560 * SVR4 Process Information:: SVR4 process information
20561 * DJGPP Native:: Features specific to the DJGPP port
20562 * Cygwin Native:: Features specific to the Cygwin port
20563 * Hurd Native:: Features specific to @sc{gnu} Hurd
20564 * Darwin:: Features specific to Darwin
20570 On HP-UX systems, if you refer to a function or variable name that
20571 begins with a dollar sign, @value{GDBN} searches for a user or system
20572 name first, before it searches for a convenience variable.
20575 @node BSD libkvm Interface
20576 @subsection BSD libkvm Interface
20579 @cindex kernel memory image
20580 @cindex kernel crash dump
20582 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
20583 interface that provides a uniform interface for accessing kernel virtual
20584 memory images, including live systems and crash dumps. @value{GDBN}
20585 uses this interface to allow you to debug live kernels and kernel crash
20586 dumps on many native BSD configurations. This is implemented as a
20587 special @code{kvm} debugging target. For debugging a live system, load
20588 the currently running kernel into @value{GDBN} and connect to the
20592 (@value{GDBP}) @b{target kvm}
20595 For debugging crash dumps, provide the file name of the crash dump as an
20599 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
20602 Once connected to the @code{kvm} target, the following commands are
20608 Set current context from the @dfn{Process Control Block} (PCB) address.
20611 Set current context from proc address. This command isn't available on
20612 modern FreeBSD systems.
20615 @node SVR4 Process Information
20616 @subsection SVR4 Process Information
20618 @cindex examine process image
20619 @cindex process info via @file{/proc}
20621 Many versions of SVR4 and compatible systems provide a facility called
20622 @samp{/proc} that can be used to examine the image of a running
20623 process using file-system subroutines.
20625 If @value{GDBN} is configured for an operating system with this
20626 facility, the command @code{info proc} is available to report
20627 information about the process running your program, or about any
20628 process running on your system. This includes, as of this writing,
20629 @sc{gnu}/Linux and Solaris, but not HP-UX, for example.
20631 This command may also work on core files that were created on a system
20632 that has the @samp{/proc} facility.
20638 @itemx info proc @var{process-id}
20639 Summarize available information about any running process. If a
20640 process ID is specified by @var{process-id}, display information about
20641 that process; otherwise display information about the program being
20642 debugged. The summary includes the debugged process ID, the command
20643 line used to invoke it, its current working directory, and its
20644 executable file's absolute file name.
20646 On some systems, @var{process-id} can be of the form
20647 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
20648 within a process. If the optional @var{pid} part is missing, it means
20649 a thread from the process being debugged (the leading @samp{/} still
20650 needs to be present, or else @value{GDBN} will interpret the number as
20651 a process ID rather than a thread ID).
20653 @item info proc cmdline
20654 @cindex info proc cmdline
20655 Show the original command line of the process. This command is
20656 specific to @sc{gnu}/Linux.
20658 @item info proc cwd
20659 @cindex info proc cwd
20660 Show the current working directory of the process. This command is
20661 specific to @sc{gnu}/Linux.
20663 @item info proc exe
20664 @cindex info proc exe
20665 Show the name of executable of the process. This command is specific
20668 @item info proc mappings
20669 @cindex memory address space mappings
20670 Report the memory address space ranges accessible in the program, with
20671 information on whether the process has read, write, or execute access
20672 rights to each range. On @sc{gnu}/Linux systems, each memory range
20673 includes the object file which is mapped to that range, instead of the
20674 memory access rights to that range.
20676 @item info proc stat
20677 @itemx info proc status
20678 @cindex process detailed status information
20679 These subcommands are specific to @sc{gnu}/Linux systems. They show
20680 the process-related information, including the user ID and group ID;
20681 how many threads are there in the process; its virtual memory usage;
20682 the signals that are pending, blocked, and ignored; its TTY; its
20683 consumption of system and user time; its stack size; its @samp{nice}
20684 value; etc. For more information, see the @samp{proc} man page
20685 (type @kbd{man 5 proc} from your shell prompt).
20687 @item info proc all
20688 Show all the information about the process described under all of the
20689 above @code{info proc} subcommands.
20692 @comment These sub-options of 'info proc' were not included when
20693 @comment procfs.c was re-written. Keep their descriptions around
20694 @comment against the day when someone finds the time to put them back in.
20695 @kindex info proc times
20696 @item info proc times
20697 Starting time, user CPU time, and system CPU time for your program and
20700 @kindex info proc id
20702 Report on the process IDs related to your program: its own process ID,
20703 the ID of its parent, the process group ID, and the session ID.
20706 @item set procfs-trace
20707 @kindex set procfs-trace
20708 @cindex @code{procfs} API calls
20709 This command enables and disables tracing of @code{procfs} API calls.
20711 @item show procfs-trace
20712 @kindex show procfs-trace
20713 Show the current state of @code{procfs} API call tracing.
20715 @item set procfs-file @var{file}
20716 @kindex set procfs-file
20717 Tell @value{GDBN} to write @code{procfs} API trace to the named
20718 @var{file}. @value{GDBN} appends the trace info to the previous
20719 contents of the file. The default is to display the trace on the
20722 @item show procfs-file
20723 @kindex show procfs-file
20724 Show the file to which @code{procfs} API trace is written.
20726 @item proc-trace-entry
20727 @itemx proc-trace-exit
20728 @itemx proc-untrace-entry
20729 @itemx proc-untrace-exit
20730 @kindex proc-trace-entry
20731 @kindex proc-trace-exit
20732 @kindex proc-untrace-entry
20733 @kindex proc-untrace-exit
20734 These commands enable and disable tracing of entries into and exits
20735 from the @code{syscall} interface.
20738 @kindex info pidlist
20739 @cindex process list, QNX Neutrino
20740 For QNX Neutrino only, this command displays the list of all the
20741 processes and all the threads within each process.
20744 @kindex info meminfo
20745 @cindex mapinfo list, QNX Neutrino
20746 For QNX Neutrino only, this command displays the list of all mapinfos.
20750 @subsection Features for Debugging @sc{djgpp} Programs
20751 @cindex @sc{djgpp} debugging
20752 @cindex native @sc{djgpp} debugging
20753 @cindex MS-DOS-specific commands
20756 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
20757 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
20758 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
20759 top of real-mode DOS systems and their emulations.
20761 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
20762 defines a few commands specific to the @sc{djgpp} port. This
20763 subsection describes those commands.
20768 This is a prefix of @sc{djgpp}-specific commands which print
20769 information about the target system and important OS structures.
20772 @cindex MS-DOS system info
20773 @cindex free memory information (MS-DOS)
20774 @item info dos sysinfo
20775 This command displays assorted information about the underlying
20776 platform: the CPU type and features, the OS version and flavor, the
20777 DPMI version, and the available conventional and DPMI memory.
20782 @cindex segment descriptor tables
20783 @cindex descriptor tables display
20785 @itemx info dos ldt
20786 @itemx info dos idt
20787 These 3 commands display entries from, respectively, Global, Local,
20788 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
20789 tables are data structures which store a descriptor for each segment
20790 that is currently in use. The segment's selector is an index into a
20791 descriptor table; the table entry for that index holds the
20792 descriptor's base address and limit, and its attributes and access
20795 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
20796 segment (used for both data and the stack), and a DOS segment (which
20797 allows access to DOS/BIOS data structures and absolute addresses in
20798 conventional memory). However, the DPMI host will usually define
20799 additional segments in order to support the DPMI environment.
20801 @cindex garbled pointers
20802 These commands allow to display entries from the descriptor tables.
20803 Without an argument, all entries from the specified table are
20804 displayed. An argument, which should be an integer expression, means
20805 display a single entry whose index is given by the argument. For
20806 example, here's a convenient way to display information about the
20807 debugged program's data segment:
20810 @exdent @code{(@value{GDBP}) info dos ldt $ds}
20811 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
20815 This comes in handy when you want to see whether a pointer is outside
20816 the data segment's limit (i.e.@: @dfn{garbled}).
20818 @cindex page tables display (MS-DOS)
20820 @itemx info dos pte
20821 These two commands display entries from, respectively, the Page
20822 Directory and the Page Tables. Page Directories and Page Tables are
20823 data structures which control how virtual memory addresses are mapped
20824 into physical addresses. A Page Table includes an entry for every
20825 page of memory that is mapped into the program's address space; there
20826 may be several Page Tables, each one holding up to 4096 entries. A
20827 Page Directory has up to 4096 entries, one each for every Page Table
20828 that is currently in use.
20830 Without an argument, @kbd{info dos pde} displays the entire Page
20831 Directory, and @kbd{info dos pte} displays all the entries in all of
20832 the Page Tables. An argument, an integer expression, given to the
20833 @kbd{info dos pde} command means display only that entry from the Page
20834 Directory table. An argument given to the @kbd{info dos pte} command
20835 means display entries from a single Page Table, the one pointed to by
20836 the specified entry in the Page Directory.
20838 @cindex direct memory access (DMA) on MS-DOS
20839 These commands are useful when your program uses @dfn{DMA} (Direct
20840 Memory Access), which needs physical addresses to program the DMA
20843 These commands are supported only with some DPMI servers.
20845 @cindex physical address from linear address
20846 @item info dos address-pte @var{addr}
20847 This command displays the Page Table entry for a specified linear
20848 address. The argument @var{addr} is a linear address which should
20849 already have the appropriate segment's base address added to it,
20850 because this command accepts addresses which may belong to @emph{any}
20851 segment. For example, here's how to display the Page Table entry for
20852 the page where a variable @code{i} is stored:
20855 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
20856 @exdent @code{Page Table entry for address 0x11a00d30:}
20857 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
20861 This says that @code{i} is stored at offset @code{0xd30} from the page
20862 whose physical base address is @code{0x02698000}, and shows all the
20863 attributes of that page.
20865 Note that you must cast the addresses of variables to a @code{char *},
20866 since otherwise the value of @code{__djgpp_base_address}, the base
20867 address of all variables and functions in a @sc{djgpp} program, will
20868 be added using the rules of C pointer arithmetics: if @code{i} is
20869 declared an @code{int}, @value{GDBN} will add 4 times the value of
20870 @code{__djgpp_base_address} to the address of @code{i}.
20872 Here's another example, it displays the Page Table entry for the
20876 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
20877 @exdent @code{Page Table entry for address 0x29110:}
20878 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
20882 (The @code{+ 3} offset is because the transfer buffer's address is the
20883 3rd member of the @code{_go32_info_block} structure.) The output
20884 clearly shows that this DPMI server maps the addresses in conventional
20885 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
20886 linear (@code{0x29110}) addresses are identical.
20888 This command is supported only with some DPMI servers.
20891 @cindex DOS serial data link, remote debugging
20892 In addition to native debugging, the DJGPP port supports remote
20893 debugging via a serial data link. The following commands are specific
20894 to remote serial debugging in the DJGPP port of @value{GDBN}.
20897 @kindex set com1base
20898 @kindex set com1irq
20899 @kindex set com2base
20900 @kindex set com2irq
20901 @kindex set com3base
20902 @kindex set com3irq
20903 @kindex set com4base
20904 @kindex set com4irq
20905 @item set com1base @var{addr}
20906 This command sets the base I/O port address of the @file{COM1} serial
20909 @item set com1irq @var{irq}
20910 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
20911 for the @file{COM1} serial port.
20913 There are similar commands @samp{set com2base}, @samp{set com3irq},
20914 etc.@: for setting the port address and the @code{IRQ} lines for the
20917 @kindex show com1base
20918 @kindex show com1irq
20919 @kindex show com2base
20920 @kindex show com2irq
20921 @kindex show com3base
20922 @kindex show com3irq
20923 @kindex show com4base
20924 @kindex show com4irq
20925 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
20926 display the current settings of the base address and the @code{IRQ}
20927 lines used by the COM ports.
20930 @kindex info serial
20931 @cindex DOS serial port status
20932 This command prints the status of the 4 DOS serial ports. For each
20933 port, it prints whether it's active or not, its I/O base address and
20934 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
20935 counts of various errors encountered so far.
20939 @node Cygwin Native
20940 @subsection Features for Debugging MS Windows PE Executables
20941 @cindex MS Windows debugging
20942 @cindex native Cygwin debugging
20943 @cindex Cygwin-specific commands
20945 @value{GDBN} supports native debugging of MS Windows programs, including
20946 DLLs with and without symbolic debugging information.
20948 @cindex Ctrl-BREAK, MS-Windows
20949 @cindex interrupt debuggee on MS-Windows
20950 MS-Windows programs that call @code{SetConsoleMode} to switch off the
20951 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
20952 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
20953 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
20954 sequence, which can be used to interrupt the debuggee even if it
20957 There are various additional Cygwin-specific commands, described in
20958 this section. Working with DLLs that have no debugging symbols is
20959 described in @ref{Non-debug DLL Symbols}.
20964 This is a prefix of MS Windows-specific commands which print
20965 information about the target system and important OS structures.
20967 @item info w32 selector
20968 This command displays information returned by
20969 the Win32 API @code{GetThreadSelectorEntry} function.
20970 It takes an optional argument that is evaluated to
20971 a long value to give the information about this given selector.
20972 Without argument, this command displays information
20973 about the six segment registers.
20975 @item info w32 thread-information-block
20976 This command displays thread specific information stored in the
20977 Thread Information Block (readable on the X86 CPU family using @code{$fs}
20978 selector for 32-bit programs and @code{$gs} for 64-bit programs).
20980 @kindex set cygwin-exceptions
20981 @cindex debugging the Cygwin DLL
20982 @cindex Cygwin DLL, debugging
20983 @item set cygwin-exceptions @var{mode}
20984 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
20985 happen inside the Cygwin DLL. If @var{mode} is @code{off},
20986 @value{GDBN} will delay recognition of exceptions, and may ignore some
20987 exceptions which seem to be caused by internal Cygwin DLL
20988 ``bookkeeping''. This option is meant primarily for debugging the
20989 Cygwin DLL itself; the default value is @code{off} to avoid annoying
20990 @value{GDBN} users with false @code{SIGSEGV} signals.
20992 @kindex show cygwin-exceptions
20993 @item show cygwin-exceptions
20994 Displays whether @value{GDBN} will break on exceptions that happen
20995 inside the Cygwin DLL itself.
20997 @kindex set new-console
20998 @item set new-console @var{mode}
20999 If @var{mode} is @code{on} the debuggee will
21000 be started in a new console on next start.
21001 If @var{mode} is @code{off}, the debuggee will
21002 be started in the same console as the debugger.
21004 @kindex show new-console
21005 @item show new-console
21006 Displays whether a new console is used
21007 when the debuggee is started.
21009 @kindex set new-group
21010 @item set new-group @var{mode}
21011 This boolean value controls whether the debuggee should
21012 start a new group or stay in the same group as the debugger.
21013 This affects the way the Windows OS handles
21016 @kindex show new-group
21017 @item show new-group
21018 Displays current value of new-group boolean.
21020 @kindex set debugevents
21021 @item set debugevents
21022 This boolean value adds debug output concerning kernel events related
21023 to the debuggee seen by the debugger. This includes events that
21024 signal thread and process creation and exit, DLL loading and
21025 unloading, console interrupts, and debugging messages produced by the
21026 Windows @code{OutputDebugString} API call.
21028 @kindex set debugexec
21029 @item set debugexec
21030 This boolean value adds debug output concerning execute events
21031 (such as resume thread) seen by the debugger.
21033 @kindex set debugexceptions
21034 @item set debugexceptions
21035 This boolean value adds debug output concerning exceptions in the
21036 debuggee seen by the debugger.
21038 @kindex set debugmemory
21039 @item set debugmemory
21040 This boolean value adds debug output concerning debuggee memory reads
21041 and writes by the debugger.
21045 This boolean values specifies whether the debuggee is called
21046 via a shell or directly (default value is on).
21050 Displays if the debuggee will be started with a shell.
21055 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
21058 @node Non-debug DLL Symbols
21059 @subsubsection Support for DLLs without Debugging Symbols
21060 @cindex DLLs with no debugging symbols
21061 @cindex Minimal symbols and DLLs
21063 Very often on windows, some of the DLLs that your program relies on do
21064 not include symbolic debugging information (for example,
21065 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
21066 symbols in a DLL, it relies on the minimal amount of symbolic
21067 information contained in the DLL's export table. This section
21068 describes working with such symbols, known internally to @value{GDBN} as
21069 ``minimal symbols''.
21071 Note that before the debugged program has started execution, no DLLs
21072 will have been loaded. The easiest way around this problem is simply to
21073 start the program --- either by setting a breakpoint or letting the
21074 program run once to completion.
21076 @subsubsection DLL Name Prefixes
21078 In keeping with the naming conventions used by the Microsoft debugging
21079 tools, DLL export symbols are made available with a prefix based on the
21080 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
21081 also entered into the symbol table, so @code{CreateFileA} is often
21082 sufficient. In some cases there will be name clashes within a program
21083 (particularly if the executable itself includes full debugging symbols)
21084 necessitating the use of the fully qualified name when referring to the
21085 contents of the DLL. Use single-quotes around the name to avoid the
21086 exclamation mark (``!'') being interpreted as a language operator.
21088 Note that the internal name of the DLL may be all upper-case, even
21089 though the file name of the DLL is lower-case, or vice-versa. Since
21090 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
21091 some confusion. If in doubt, try the @code{info functions} and
21092 @code{info variables} commands or even @code{maint print msymbols}
21093 (@pxref{Symbols}). Here's an example:
21096 (@value{GDBP}) info function CreateFileA
21097 All functions matching regular expression "CreateFileA":
21099 Non-debugging symbols:
21100 0x77e885f4 CreateFileA
21101 0x77e885f4 KERNEL32!CreateFileA
21105 (@value{GDBP}) info function !
21106 All functions matching regular expression "!":
21108 Non-debugging symbols:
21109 0x6100114c cygwin1!__assert
21110 0x61004034 cygwin1!_dll_crt0@@0
21111 0x61004240 cygwin1!dll_crt0(per_process *)
21115 @subsubsection Working with Minimal Symbols
21117 Symbols extracted from a DLL's export table do not contain very much
21118 type information. All that @value{GDBN} can do is guess whether a symbol
21119 refers to a function or variable depending on the linker section that
21120 contains the symbol. Also note that the actual contents of the memory
21121 contained in a DLL are not available unless the program is running. This
21122 means that you cannot examine the contents of a variable or disassemble
21123 a function within a DLL without a running program.
21125 Variables are generally treated as pointers and dereferenced
21126 automatically. For this reason, it is often necessary to prefix a
21127 variable name with the address-of operator (``&'') and provide explicit
21128 type information in the command. Here's an example of the type of
21132 (@value{GDBP}) print 'cygwin1!__argv'
21137 (@value{GDBP}) x 'cygwin1!__argv'
21138 0x10021610: "\230y\""
21141 And two possible solutions:
21144 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
21145 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
21149 (@value{GDBP}) x/2x &'cygwin1!__argv'
21150 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
21151 (@value{GDBP}) x/x 0x10021608
21152 0x10021608: 0x0022fd98
21153 (@value{GDBP}) x/s 0x0022fd98
21154 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
21157 Setting a break point within a DLL is possible even before the program
21158 starts execution. However, under these circumstances, @value{GDBN} can't
21159 examine the initial instructions of the function in order to skip the
21160 function's frame set-up code. You can work around this by using ``*&''
21161 to set the breakpoint at a raw memory address:
21164 (@value{GDBP}) break *&'python22!PyOS_Readline'
21165 Breakpoint 1 at 0x1e04eff0
21168 The author of these extensions is not entirely convinced that setting a
21169 break point within a shared DLL like @file{kernel32.dll} is completely
21173 @subsection Commands Specific to @sc{gnu} Hurd Systems
21174 @cindex @sc{gnu} Hurd debugging
21176 This subsection describes @value{GDBN} commands specific to the
21177 @sc{gnu} Hurd native debugging.
21182 @kindex set signals@r{, Hurd command}
21183 @kindex set sigs@r{, Hurd command}
21184 This command toggles the state of inferior signal interception by
21185 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
21186 affected by this command. @code{sigs} is a shorthand alias for
21191 @kindex show signals@r{, Hurd command}
21192 @kindex show sigs@r{, Hurd command}
21193 Show the current state of intercepting inferior's signals.
21195 @item set signal-thread
21196 @itemx set sigthread
21197 @kindex set signal-thread
21198 @kindex set sigthread
21199 This command tells @value{GDBN} which thread is the @code{libc} signal
21200 thread. That thread is run when a signal is delivered to a running
21201 process. @code{set sigthread} is the shorthand alias of @code{set
21204 @item show signal-thread
21205 @itemx show sigthread
21206 @kindex show signal-thread
21207 @kindex show sigthread
21208 These two commands show which thread will run when the inferior is
21209 delivered a signal.
21212 @kindex set stopped@r{, Hurd command}
21213 This commands tells @value{GDBN} that the inferior process is stopped,
21214 as with the @code{SIGSTOP} signal. The stopped process can be
21215 continued by delivering a signal to it.
21218 @kindex show stopped@r{, Hurd command}
21219 This command shows whether @value{GDBN} thinks the debuggee is
21222 @item set exceptions
21223 @kindex set exceptions@r{, Hurd command}
21224 Use this command to turn off trapping of exceptions in the inferior.
21225 When exception trapping is off, neither breakpoints nor
21226 single-stepping will work. To restore the default, set exception
21229 @item show exceptions
21230 @kindex show exceptions@r{, Hurd command}
21231 Show the current state of trapping exceptions in the inferior.
21233 @item set task pause
21234 @kindex set task@r{, Hurd commands}
21235 @cindex task attributes (@sc{gnu} Hurd)
21236 @cindex pause current task (@sc{gnu} Hurd)
21237 This command toggles task suspension when @value{GDBN} has control.
21238 Setting it to on takes effect immediately, and the task is suspended
21239 whenever @value{GDBN} gets control. Setting it to off will take
21240 effect the next time the inferior is continued. If this option is set
21241 to off, you can use @code{set thread default pause on} or @code{set
21242 thread pause on} (see below) to pause individual threads.
21244 @item show task pause
21245 @kindex show task@r{, Hurd commands}
21246 Show the current state of task suspension.
21248 @item set task detach-suspend-count
21249 @cindex task suspend count
21250 @cindex detach from task, @sc{gnu} Hurd
21251 This command sets the suspend count the task will be left with when
21252 @value{GDBN} detaches from it.
21254 @item show task detach-suspend-count
21255 Show the suspend count the task will be left with when detaching.
21257 @item set task exception-port
21258 @itemx set task excp
21259 @cindex task exception port, @sc{gnu} Hurd
21260 This command sets the task exception port to which @value{GDBN} will
21261 forward exceptions. The argument should be the value of the @dfn{send
21262 rights} of the task. @code{set task excp} is a shorthand alias.
21264 @item set noninvasive
21265 @cindex noninvasive task options
21266 This command switches @value{GDBN} to a mode that is the least
21267 invasive as far as interfering with the inferior is concerned. This
21268 is the same as using @code{set task pause}, @code{set exceptions}, and
21269 @code{set signals} to values opposite to the defaults.
21271 @item info send-rights
21272 @itemx info receive-rights
21273 @itemx info port-rights
21274 @itemx info port-sets
21275 @itemx info dead-names
21278 @cindex send rights, @sc{gnu} Hurd
21279 @cindex receive rights, @sc{gnu} Hurd
21280 @cindex port rights, @sc{gnu} Hurd
21281 @cindex port sets, @sc{gnu} Hurd
21282 @cindex dead names, @sc{gnu} Hurd
21283 These commands display information about, respectively, send rights,
21284 receive rights, port rights, port sets, and dead names of a task.
21285 There are also shorthand aliases: @code{info ports} for @code{info
21286 port-rights} and @code{info psets} for @code{info port-sets}.
21288 @item set thread pause
21289 @kindex set thread@r{, Hurd command}
21290 @cindex thread properties, @sc{gnu} Hurd
21291 @cindex pause current thread (@sc{gnu} Hurd)
21292 This command toggles current thread suspension when @value{GDBN} has
21293 control. Setting it to on takes effect immediately, and the current
21294 thread is suspended whenever @value{GDBN} gets control. Setting it to
21295 off will take effect the next time the inferior is continued.
21296 Normally, this command has no effect, since when @value{GDBN} has
21297 control, the whole task is suspended. However, if you used @code{set
21298 task pause off} (see above), this command comes in handy to suspend
21299 only the current thread.
21301 @item show thread pause
21302 @kindex show thread@r{, Hurd command}
21303 This command shows the state of current thread suspension.
21305 @item set thread run
21306 This command sets whether the current thread is allowed to run.
21308 @item show thread run
21309 Show whether the current thread is allowed to run.
21311 @item set thread detach-suspend-count
21312 @cindex thread suspend count, @sc{gnu} Hurd
21313 @cindex detach from thread, @sc{gnu} Hurd
21314 This command sets the suspend count @value{GDBN} will leave on a
21315 thread when detaching. This number is relative to the suspend count
21316 found by @value{GDBN} when it notices the thread; use @code{set thread
21317 takeover-suspend-count} to force it to an absolute value.
21319 @item show thread detach-suspend-count
21320 Show the suspend count @value{GDBN} will leave on the thread when
21323 @item set thread exception-port
21324 @itemx set thread excp
21325 Set the thread exception port to which to forward exceptions. This
21326 overrides the port set by @code{set task exception-port} (see above).
21327 @code{set thread excp} is the shorthand alias.
21329 @item set thread takeover-suspend-count
21330 Normally, @value{GDBN}'s thread suspend counts are relative to the
21331 value @value{GDBN} finds when it notices each thread. This command
21332 changes the suspend counts to be absolute instead.
21334 @item set thread default
21335 @itemx show thread default
21336 @cindex thread default settings, @sc{gnu} Hurd
21337 Each of the above @code{set thread} commands has a @code{set thread
21338 default} counterpart (e.g., @code{set thread default pause}, @code{set
21339 thread default exception-port}, etc.). The @code{thread default}
21340 variety of commands sets the default thread properties for all
21341 threads; you can then change the properties of individual threads with
21342 the non-default commands.
21349 @value{GDBN} provides the following commands specific to the Darwin target:
21352 @item set debug darwin @var{num}
21353 @kindex set debug darwin
21354 When set to a non zero value, enables debugging messages specific to
21355 the Darwin support. Higher values produce more verbose output.
21357 @item show debug darwin
21358 @kindex show debug darwin
21359 Show the current state of Darwin messages.
21361 @item set debug mach-o @var{num}
21362 @kindex set debug mach-o
21363 When set to a non zero value, enables debugging messages while
21364 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
21365 file format used on Darwin for object and executable files.) Higher
21366 values produce more verbose output. This is a command to diagnose
21367 problems internal to @value{GDBN} and should not be needed in normal
21370 @item show debug mach-o
21371 @kindex show debug mach-o
21372 Show the current state of Mach-O file messages.
21374 @item set mach-exceptions on
21375 @itemx set mach-exceptions off
21376 @kindex set mach-exceptions
21377 On Darwin, faults are first reported as a Mach exception and are then
21378 mapped to a Posix signal. Use this command to turn on trapping of
21379 Mach exceptions in the inferior. This might be sometimes useful to
21380 better understand the cause of a fault. The default is off.
21382 @item show mach-exceptions
21383 @kindex show mach-exceptions
21384 Show the current state of exceptions trapping.
21389 @section Embedded Operating Systems
21391 This section describes configurations involving the debugging of
21392 embedded operating systems that are available for several different
21395 @value{GDBN} includes the ability to debug programs running on
21396 various real-time operating systems.
21398 @node Embedded Processors
21399 @section Embedded Processors
21401 This section goes into details specific to particular embedded
21404 @cindex send command to simulator
21405 Whenever a specific embedded processor has a simulator, @value{GDBN}
21406 allows to send an arbitrary command to the simulator.
21409 @item sim @var{command}
21410 @kindex sim@r{, a command}
21411 Send an arbitrary @var{command} string to the simulator. Consult the
21412 documentation for the specific simulator in use for information about
21413 acceptable commands.
21419 * M32R/D:: Renesas M32R/D
21420 * M68K:: Motorola M68K
21421 * MicroBlaze:: Xilinx MicroBlaze
21422 * MIPS Embedded:: MIPS Embedded
21423 * PowerPC Embedded:: PowerPC Embedded
21424 * PA:: HP PA Embedded
21425 * Sparclet:: Tsqware Sparclet
21426 * Sparclite:: Fujitsu Sparclite
21427 * Z8000:: Zilog Z8000
21430 * Super-H:: Renesas Super-H
21439 @item target rdi @var{dev}
21440 ARM Angel monitor, via RDI library interface to ADP protocol. You may
21441 use this target to communicate with both boards running the Angel
21442 monitor, or with the EmbeddedICE JTAG debug device.
21445 @item target rdp @var{dev}
21450 @value{GDBN} provides the following ARM-specific commands:
21453 @item set arm disassembler
21455 This commands selects from a list of disassembly styles. The
21456 @code{"std"} style is the standard style.
21458 @item show arm disassembler
21460 Show the current disassembly style.
21462 @item set arm apcs32
21463 @cindex ARM 32-bit mode
21464 This command toggles ARM operation mode between 32-bit and 26-bit.
21466 @item show arm apcs32
21467 Display the current usage of the ARM 32-bit mode.
21469 @item set arm fpu @var{fputype}
21470 This command sets the ARM floating-point unit (FPU) type. The
21471 argument @var{fputype} can be one of these:
21475 Determine the FPU type by querying the OS ABI.
21477 Software FPU, with mixed-endian doubles on little-endian ARM
21480 GCC-compiled FPA co-processor.
21482 Software FPU with pure-endian doubles.
21488 Show the current type of the FPU.
21491 This command forces @value{GDBN} to use the specified ABI.
21494 Show the currently used ABI.
21496 @item set arm fallback-mode (arm|thumb|auto)
21497 @value{GDBN} uses the symbol table, when available, to determine
21498 whether instructions are ARM or Thumb. This command controls
21499 @value{GDBN}'s default behavior when the symbol table is not
21500 available. The default is @samp{auto}, which causes @value{GDBN} to
21501 use the current execution mode (from the @code{T} bit in the @code{CPSR}
21504 @item show arm fallback-mode
21505 Show the current fallback instruction mode.
21507 @item set arm force-mode (arm|thumb|auto)
21508 This command overrides use of the symbol table to determine whether
21509 instructions are ARM or Thumb. The default is @samp{auto}, which
21510 causes @value{GDBN} to use the symbol table and then the setting
21511 of @samp{set arm fallback-mode}.
21513 @item show arm force-mode
21514 Show the current forced instruction mode.
21516 @item set debug arm
21517 Toggle whether to display ARM-specific debugging messages from the ARM
21518 target support subsystem.
21520 @item show debug arm
21521 Show whether ARM-specific debugging messages are enabled.
21524 The following commands are available when an ARM target is debugged
21525 using the RDI interface:
21528 @item rdilogfile @r{[}@var{file}@r{]}
21530 @cindex ADP (Angel Debugger Protocol) logging
21531 Set the filename for the ADP (Angel Debugger Protocol) packet log.
21532 With an argument, sets the log file to the specified @var{file}. With
21533 no argument, show the current log file name. The default log file is
21536 @item rdilogenable @r{[}@var{arg}@r{]}
21537 @kindex rdilogenable
21538 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
21539 enables logging, with an argument 0 or @code{"no"} disables it. With
21540 no arguments displays the current setting. When logging is enabled,
21541 ADP packets exchanged between @value{GDBN} and the RDI target device
21542 are logged to a file.
21544 @item set rdiromatzero
21545 @kindex set rdiromatzero
21546 @cindex ROM at zero address, RDI
21547 Tell @value{GDBN} whether the target has ROM at address 0. If on,
21548 vector catching is disabled, so that zero address can be used. If off
21549 (the default), vector catching is enabled. For this command to take
21550 effect, it needs to be invoked prior to the @code{target rdi} command.
21552 @item show rdiromatzero
21553 @kindex show rdiromatzero
21554 Show the current setting of ROM at zero address.
21556 @item set rdiheartbeat
21557 @kindex set rdiheartbeat
21558 @cindex RDI heartbeat
21559 Enable or disable RDI heartbeat packets. It is not recommended to
21560 turn on this option, since it confuses ARM and EPI JTAG interface, as
21561 well as the Angel monitor.
21563 @item show rdiheartbeat
21564 @kindex show rdiheartbeat
21565 Show the setting of RDI heartbeat packets.
21569 @item target sim @r{[}@var{simargs}@r{]} @dots{}
21570 The @value{GDBN} ARM simulator accepts the following optional arguments.
21573 @item --swi-support=@var{type}
21574 Tell the simulator which SWI interfaces to support. The argument
21575 @var{type} may be a comma separated list of the following values.
21576 The default value is @code{all}.
21589 @subsection Renesas M32R/D and M32R/SDI
21592 @kindex target m32r
21593 @item target m32r @var{dev}
21594 Renesas M32R/D ROM monitor.
21596 @kindex target m32rsdi
21597 @item target m32rsdi @var{dev}
21598 Renesas M32R SDI server, connected via parallel port to the board.
21601 The following @value{GDBN} commands are specific to the M32R monitor:
21604 @item set download-path @var{path}
21605 @kindex set download-path
21606 @cindex find downloadable @sc{srec} files (M32R)
21607 Set the default path for finding downloadable @sc{srec} files.
21609 @item show download-path
21610 @kindex show download-path
21611 Show the default path for downloadable @sc{srec} files.
21613 @item set board-address @var{addr}
21614 @kindex set board-address
21615 @cindex M32-EVA target board address
21616 Set the IP address for the M32R-EVA target board.
21618 @item show board-address
21619 @kindex show board-address
21620 Show the current IP address of the target board.
21622 @item set server-address @var{addr}
21623 @kindex set server-address
21624 @cindex download server address (M32R)
21625 Set the IP address for the download server, which is the @value{GDBN}'s
21628 @item show server-address
21629 @kindex show server-address
21630 Display the IP address of the download server.
21632 @item upload @r{[}@var{file}@r{]}
21633 @kindex upload@r{, M32R}
21634 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
21635 upload capability. If no @var{file} argument is given, the current
21636 executable file is uploaded.
21638 @item tload @r{[}@var{file}@r{]}
21639 @kindex tload@r{, M32R}
21640 Test the @code{upload} command.
21643 The following commands are available for M32R/SDI:
21648 @cindex reset SDI connection, M32R
21649 This command resets the SDI connection.
21653 This command shows the SDI connection status.
21656 @kindex debug_chaos
21657 @cindex M32R/Chaos debugging
21658 Instructs the remote that M32R/Chaos debugging is to be used.
21660 @item use_debug_dma
21661 @kindex use_debug_dma
21662 Instructs the remote to use the DEBUG_DMA method of accessing memory.
21665 @kindex use_mon_code
21666 Instructs the remote to use the MON_CODE method of accessing memory.
21669 @kindex use_ib_break
21670 Instructs the remote to set breakpoints by IB break.
21672 @item use_dbt_break
21673 @kindex use_dbt_break
21674 Instructs the remote to set breakpoints by DBT.
21680 The Motorola m68k configuration includes ColdFire support, and a
21681 target command for the following ROM monitor.
21685 @kindex target dbug
21686 @item target dbug @var{dev}
21687 dBUG ROM monitor for Motorola ColdFire.
21692 @subsection MicroBlaze
21693 @cindex Xilinx MicroBlaze
21694 @cindex XMD, Xilinx Microprocessor Debugger
21696 The MicroBlaze is a soft-core processor supported on various Xilinx
21697 FPGAs, such as Spartan or Virtex series. Boards with these processors
21698 usually have JTAG ports which connect to a host system running the Xilinx
21699 Embedded Development Kit (EDK) or Software Development Kit (SDK).
21700 This host system is used to download the configuration bitstream to
21701 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
21702 communicates with the target board using the JTAG interface and
21703 presents a @code{gdbserver} interface to the board. By default
21704 @code{xmd} uses port @code{1234}. (While it is possible to change
21705 this default port, it requires the use of undocumented @code{xmd}
21706 commands. Contact Xilinx support if you need to do this.)
21708 Use these GDB commands to connect to the MicroBlaze target processor.
21711 @item target remote :1234
21712 Use this command to connect to the target if you are running @value{GDBN}
21713 on the same system as @code{xmd}.
21715 @item target remote @var{xmd-host}:1234
21716 Use this command to connect to the target if it is connected to @code{xmd}
21717 running on a different system named @var{xmd-host}.
21720 Use this command to download a program to the MicroBlaze target.
21722 @item set debug microblaze @var{n}
21723 Enable MicroBlaze-specific debugging messages if non-zero.
21725 @item show debug microblaze @var{n}
21726 Show MicroBlaze-specific debugging level.
21729 @node MIPS Embedded
21730 @subsection @acronym{MIPS} Embedded
21732 @cindex @acronym{MIPS} boards
21733 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
21734 @acronym{MIPS} board attached to a serial line. This is available when
21735 you configure @value{GDBN} with @samp{--target=mips-elf}.
21738 Use these @value{GDBN} commands to specify the connection to your target board:
21741 @item target mips @var{port}
21742 @kindex target mips @var{port}
21743 To run a program on the board, start up @code{@value{GDBP}} with the
21744 name of your program as the argument. To connect to the board, use the
21745 command @samp{target mips @var{port}}, where @var{port} is the name of
21746 the serial port connected to the board. If the program has not already
21747 been downloaded to the board, you may use the @code{load} command to
21748 download it. You can then use all the usual @value{GDBN} commands.
21750 For example, this sequence connects to the target board through a serial
21751 port, and loads and runs a program called @var{prog} through the
21755 host$ @value{GDBP} @var{prog}
21756 @value{GDBN} is free software and @dots{}
21757 (@value{GDBP}) target mips /dev/ttyb
21758 (@value{GDBP}) load @var{prog}
21762 @item target mips @var{hostname}:@var{portnumber}
21763 On some @value{GDBN} host configurations, you can specify a TCP
21764 connection (for instance, to a serial line managed by a terminal
21765 concentrator) instead of a serial port, using the syntax
21766 @samp{@var{hostname}:@var{portnumber}}.
21768 @item target pmon @var{port}
21769 @kindex target pmon @var{port}
21772 @item target ddb @var{port}
21773 @kindex target ddb @var{port}
21774 NEC's DDB variant of PMON for Vr4300.
21776 @item target lsi @var{port}
21777 @kindex target lsi @var{port}
21778 LSI variant of PMON.
21780 @kindex target r3900
21781 @item target r3900 @var{dev}
21782 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
21784 @kindex target array
21785 @item target array @var{dev}
21786 Array Tech LSI33K RAID controller board.
21792 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
21795 @item set mipsfpu double
21796 @itemx set mipsfpu single
21797 @itemx set mipsfpu none
21798 @itemx set mipsfpu auto
21799 @itemx show mipsfpu
21800 @kindex set mipsfpu
21801 @kindex show mipsfpu
21802 @cindex @acronym{MIPS} remote floating point
21803 @cindex floating point, @acronym{MIPS} remote
21804 If your target board does not support the @acronym{MIPS} floating point
21805 coprocessor, you should use the command @samp{set mipsfpu none} (if you
21806 need this, you may wish to put the command in your @value{GDBN} init
21807 file). This tells @value{GDBN} how to find the return value of
21808 functions which return floating point values. It also allows
21809 @value{GDBN} to avoid saving the floating point registers when calling
21810 functions on the board. If you are using a floating point coprocessor
21811 with only single precision floating point support, as on the @sc{r4650}
21812 processor, use the command @samp{set mipsfpu single}. The default
21813 double precision floating point coprocessor may be selected using
21814 @samp{set mipsfpu double}.
21816 In previous versions the only choices were double precision or no
21817 floating point, so @samp{set mipsfpu on} will select double precision
21818 and @samp{set mipsfpu off} will select no floating point.
21820 As usual, you can inquire about the @code{mipsfpu} variable with
21821 @samp{show mipsfpu}.
21823 @item set timeout @var{seconds}
21824 @itemx set retransmit-timeout @var{seconds}
21825 @itemx show timeout
21826 @itemx show retransmit-timeout
21827 @cindex @code{timeout}, @acronym{MIPS} protocol
21828 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
21829 @kindex set timeout
21830 @kindex show timeout
21831 @kindex set retransmit-timeout
21832 @kindex show retransmit-timeout
21833 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
21834 remote protocol, with the @code{set timeout @var{seconds}} command. The
21835 default is 5 seconds. Similarly, you can control the timeout used while
21836 waiting for an acknowledgment of a packet with the @code{set
21837 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
21838 You can inspect both values with @code{show timeout} and @code{show
21839 retransmit-timeout}. (These commands are @emph{only} available when
21840 @value{GDBN} is configured for @samp{--target=mips-elf}.)
21842 The timeout set by @code{set timeout} does not apply when @value{GDBN}
21843 is waiting for your program to stop. In that case, @value{GDBN} waits
21844 forever because it has no way of knowing how long the program is going
21845 to run before stopping.
21847 @item set syn-garbage-limit @var{num}
21848 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
21849 @cindex synchronize with remote @acronym{MIPS} target
21850 Limit the maximum number of characters @value{GDBN} should ignore when
21851 it tries to synchronize with the remote target. The default is 10
21852 characters. Setting the limit to -1 means there's no limit.
21854 @item show syn-garbage-limit
21855 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
21856 Show the current limit on the number of characters to ignore when
21857 trying to synchronize with the remote system.
21859 @item set monitor-prompt @var{prompt}
21860 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
21861 @cindex remote monitor prompt
21862 Tell @value{GDBN} to expect the specified @var{prompt} string from the
21863 remote monitor. The default depends on the target:
21873 @item show monitor-prompt
21874 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
21875 Show the current strings @value{GDBN} expects as the prompt from the
21878 @item set monitor-warnings
21879 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
21880 Enable or disable monitor warnings about hardware breakpoints. This
21881 has effect only for the @code{lsi} target. When on, @value{GDBN} will
21882 display warning messages whose codes are returned by the @code{lsi}
21883 PMON monitor for breakpoint commands.
21885 @item show monitor-warnings
21886 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
21887 Show the current setting of printing monitor warnings.
21889 @item pmon @var{command}
21890 @kindex pmon@r{, @acronym{MIPS} remote}
21891 @cindex send PMON command
21892 This command allows sending an arbitrary @var{command} string to the
21893 monitor. The monitor must be in debug mode for this to work.
21896 @node PowerPC Embedded
21897 @subsection PowerPC Embedded
21899 @cindex DVC register
21900 @value{GDBN} supports using the DVC (Data Value Compare) register to
21901 implement in hardware simple hardware watchpoint conditions of the form:
21904 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
21905 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
21908 The DVC register will be automatically used when @value{GDBN} detects
21909 such pattern in a condition expression, and the created watchpoint uses one
21910 debug register (either the @code{exact-watchpoints} option is on and the
21911 variable is scalar, or the variable has a length of one byte). This feature
21912 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
21915 When running on PowerPC embedded processors, @value{GDBN} automatically uses
21916 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
21917 in which case watchpoints using only one debug register are created when
21918 watching variables of scalar types.
21920 You can create an artificial array to watch an arbitrary memory
21921 region using one of the following commands (@pxref{Expressions}):
21924 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
21925 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
21928 PowerPC embedded processors support masked watchpoints. See the discussion
21929 about the @code{mask} argument in @ref{Set Watchpoints}.
21931 @cindex ranged breakpoint
21932 PowerPC embedded processors support hardware accelerated
21933 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
21934 the inferior whenever it executes an instruction at any address within
21935 the range it specifies. To set a ranged breakpoint in @value{GDBN},
21936 use the @code{break-range} command.
21938 @value{GDBN} provides the following PowerPC-specific commands:
21941 @kindex break-range
21942 @item break-range @var{start-location}, @var{end-location}
21943 Set a breakpoint for an address range given by
21944 @var{start-location} and @var{end-location}, which can specify a function name,
21945 a line number, an offset of lines from the current line or from the start
21946 location, or an address of an instruction (see @ref{Specify Location},
21947 for a list of all the possible ways to specify a @var{location}.)
21948 The breakpoint will stop execution of the inferior whenever it
21949 executes an instruction at any address within the specified range,
21950 (including @var{start-location} and @var{end-location}.)
21952 @kindex set powerpc
21953 @item set powerpc soft-float
21954 @itemx show powerpc soft-float
21955 Force @value{GDBN} to use (or not use) a software floating point calling
21956 convention. By default, @value{GDBN} selects the calling convention based
21957 on the selected architecture and the provided executable file.
21959 @item set powerpc vector-abi
21960 @itemx show powerpc vector-abi
21961 Force @value{GDBN} to use the specified calling convention for vector
21962 arguments and return values. The valid options are @samp{auto};
21963 @samp{generic}, to avoid vector registers even if they are present;
21964 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
21965 registers. By default, @value{GDBN} selects the calling convention
21966 based on the selected architecture and the provided executable file.
21968 @item set powerpc exact-watchpoints
21969 @itemx show powerpc exact-watchpoints
21970 Allow @value{GDBN} to use only one debug register when watching a variable
21971 of scalar type, thus assuming that the variable is accessed through the
21972 address of its first byte.
21974 @kindex target dink32
21975 @item target dink32 @var{dev}
21976 DINK32 ROM monitor.
21978 @kindex target ppcbug
21979 @item target ppcbug @var{dev}
21980 @kindex target ppcbug1
21981 @item target ppcbug1 @var{dev}
21982 PPCBUG ROM monitor for PowerPC.
21985 @item target sds @var{dev}
21986 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
21989 @cindex SDS protocol
21990 The following commands specific to the SDS protocol are supported
21994 @item set sdstimeout @var{nsec}
21995 @kindex set sdstimeout
21996 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
21997 default is 2 seconds.
21999 @item show sdstimeout
22000 @kindex show sdstimeout
22001 Show the current value of the SDS timeout.
22003 @item sds @var{command}
22004 @kindex sds@r{, a command}
22005 Send the specified @var{command} string to the SDS monitor.
22010 @subsection HP PA Embedded
22014 @kindex target op50n
22015 @item target op50n @var{dev}
22016 OP50N monitor, running on an OKI HPPA board.
22018 @kindex target w89k
22019 @item target w89k @var{dev}
22020 W89K monitor, running on a Winbond HPPA board.
22025 @subsection Tsqware Sparclet
22029 @value{GDBN} enables developers to debug tasks running on
22030 Sparclet targets from a Unix host.
22031 @value{GDBN} uses code that runs on
22032 both the Unix host and on the Sparclet target. The program
22033 @code{@value{GDBP}} is installed and executed on the Unix host.
22036 @item remotetimeout @var{args}
22037 @kindex remotetimeout
22038 @value{GDBN} supports the option @code{remotetimeout}.
22039 This option is set by the user, and @var{args} represents the number of
22040 seconds @value{GDBN} waits for responses.
22043 @cindex compiling, on Sparclet
22044 When compiling for debugging, include the options @samp{-g} to get debug
22045 information and @samp{-Ttext} to relocate the program to where you wish to
22046 load it on the target. You may also want to add the options @samp{-n} or
22047 @samp{-N} in order to reduce the size of the sections. Example:
22050 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
22053 You can use @code{objdump} to verify that the addresses are what you intended:
22056 sparclet-aout-objdump --headers --syms prog
22059 @cindex running, on Sparclet
22061 your Unix execution search path to find @value{GDBN}, you are ready to
22062 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
22063 (or @code{sparclet-aout-gdb}, depending on your installation).
22065 @value{GDBN} comes up showing the prompt:
22072 * Sparclet File:: Setting the file to debug
22073 * Sparclet Connection:: Connecting to Sparclet
22074 * Sparclet Download:: Sparclet download
22075 * Sparclet Execution:: Running and debugging
22078 @node Sparclet File
22079 @subsubsection Setting File to Debug
22081 The @value{GDBN} command @code{file} lets you choose with program to debug.
22084 (gdbslet) file prog
22088 @value{GDBN} then attempts to read the symbol table of @file{prog}.
22089 @value{GDBN} locates
22090 the file by searching the directories listed in the command search
22092 If the file was compiled with debug information (option @samp{-g}), source
22093 files will be searched as well.
22094 @value{GDBN} locates
22095 the source files by searching the directories listed in the directory search
22096 path (@pxref{Environment, ,Your Program's Environment}).
22098 to find a file, it displays a message such as:
22101 prog: No such file or directory.
22104 When this happens, add the appropriate directories to the search paths with
22105 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
22106 @code{target} command again.
22108 @node Sparclet Connection
22109 @subsubsection Connecting to Sparclet
22111 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
22112 To connect to a target on serial port ``@code{ttya}'', type:
22115 (gdbslet) target sparclet /dev/ttya
22116 Remote target sparclet connected to /dev/ttya
22117 main () at ../prog.c:3
22121 @value{GDBN} displays messages like these:
22127 @node Sparclet Download
22128 @subsubsection Sparclet Download
22130 @cindex download to Sparclet
22131 Once connected to the Sparclet target,
22132 you can use the @value{GDBN}
22133 @code{load} command to download the file from the host to the target.
22134 The file name and load offset should be given as arguments to the @code{load}
22136 Since the file format is aout, the program must be loaded to the starting
22137 address. You can use @code{objdump} to find out what this value is. The load
22138 offset is an offset which is added to the VMA (virtual memory address)
22139 of each of the file's sections.
22140 For instance, if the program
22141 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
22142 and bss at 0x12010170, in @value{GDBN}, type:
22145 (gdbslet) load prog 0x12010000
22146 Loading section .text, size 0xdb0 vma 0x12010000
22149 If the code is loaded at a different address then what the program was linked
22150 to, you may need to use the @code{section} and @code{add-symbol-file} commands
22151 to tell @value{GDBN} where to map the symbol table.
22153 @node Sparclet Execution
22154 @subsubsection Running and Debugging
22156 @cindex running and debugging Sparclet programs
22157 You can now begin debugging the task using @value{GDBN}'s execution control
22158 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
22159 manual for the list of commands.
22163 Breakpoint 1 at 0x12010000: file prog.c, line 3.
22165 Starting program: prog
22166 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
22167 3 char *symarg = 0;
22169 4 char *execarg = "hello!";
22174 @subsection Fujitsu Sparclite
22178 @kindex target sparclite
22179 @item target sparclite @var{dev}
22180 Fujitsu sparclite boards, used only for the purpose of loading.
22181 You must use an additional command to debug the program.
22182 For example: target remote @var{dev} using @value{GDBN} standard
22188 @subsection Zilog Z8000
22191 @cindex simulator, Z8000
22192 @cindex Zilog Z8000 simulator
22194 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
22197 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
22198 unsegmented variant of the Z8000 architecture) or the Z8001 (the
22199 segmented variant). The simulator recognizes which architecture is
22200 appropriate by inspecting the object code.
22203 @item target sim @var{args}
22205 @kindex target sim@r{, with Z8000}
22206 Debug programs on a simulated CPU. If the simulator supports setup
22207 options, specify them via @var{args}.
22211 After specifying this target, you can debug programs for the simulated
22212 CPU in the same style as programs for your host computer; use the
22213 @code{file} command to load a new program image, the @code{run} command
22214 to run your program, and so on.
22216 As well as making available all the usual machine registers
22217 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
22218 additional items of information as specially named registers:
22223 Counts clock-ticks in the simulator.
22226 Counts instructions run in the simulator.
22229 Execution time in 60ths of a second.
22233 You can refer to these values in @value{GDBN} expressions with the usual
22234 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
22235 conditional breakpoint that suspends only after at least 5000
22236 simulated clock ticks.
22239 @subsection Atmel AVR
22242 When configured for debugging the Atmel AVR, @value{GDBN} supports the
22243 following AVR-specific commands:
22246 @item info io_registers
22247 @kindex info io_registers@r{, AVR}
22248 @cindex I/O registers (Atmel AVR)
22249 This command displays information about the AVR I/O registers. For
22250 each register, @value{GDBN} prints its number and value.
22257 When configured for debugging CRIS, @value{GDBN} provides the
22258 following CRIS-specific commands:
22261 @item set cris-version @var{ver}
22262 @cindex CRIS version
22263 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
22264 The CRIS version affects register names and sizes. This command is useful in
22265 case autodetection of the CRIS version fails.
22267 @item show cris-version
22268 Show the current CRIS version.
22270 @item set cris-dwarf2-cfi
22271 @cindex DWARF-2 CFI and CRIS
22272 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
22273 Change to @samp{off} when using @code{gcc-cris} whose version is below
22276 @item show cris-dwarf2-cfi
22277 Show the current state of using DWARF-2 CFI.
22279 @item set cris-mode @var{mode}
22281 Set the current CRIS mode to @var{mode}. It should only be changed when
22282 debugging in guru mode, in which case it should be set to
22283 @samp{guru} (the default is @samp{normal}).
22285 @item show cris-mode
22286 Show the current CRIS mode.
22290 @subsection Renesas Super-H
22293 For the Renesas Super-H processor, @value{GDBN} provides these
22297 @item set sh calling-convention @var{convention}
22298 @kindex set sh calling-convention
22299 Set the calling-convention used when calling functions from @value{GDBN}.
22300 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
22301 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
22302 convention. If the DWARF-2 information of the called function specifies
22303 that the function follows the Renesas calling convention, the function
22304 is called using the Renesas calling convention. If the calling convention
22305 is set to @samp{renesas}, the Renesas calling convention is always used,
22306 regardless of the DWARF-2 information. This can be used to override the
22307 default of @samp{gcc} if debug information is missing, or the compiler
22308 does not emit the DWARF-2 calling convention entry for a function.
22310 @item show sh calling-convention
22311 @kindex show sh calling-convention
22312 Show the current calling convention setting.
22317 @node Architectures
22318 @section Architectures
22320 This section describes characteristics of architectures that affect
22321 all uses of @value{GDBN} with the architecture, both native and cross.
22328 * HPPA:: HP PA architecture
22329 * SPU:: Cell Broadband Engine SPU architecture
22335 @subsection AArch64
22336 @cindex AArch64 support
22338 When @value{GDBN} is debugging the AArch64 architecture, it provides the
22339 following special commands:
22342 @item set debug aarch64
22343 @kindex set debug aarch64
22344 This command determines whether AArch64 architecture-specific debugging
22345 messages are to be displayed.
22347 @item show debug aarch64
22348 Show whether AArch64 debugging messages are displayed.
22353 @subsection x86 Architecture-specific Issues
22356 @item set struct-convention @var{mode}
22357 @kindex set struct-convention
22358 @cindex struct return convention
22359 @cindex struct/union returned in registers
22360 Set the convention used by the inferior to return @code{struct}s and
22361 @code{union}s from functions to @var{mode}. Possible values of
22362 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
22363 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
22364 are returned on the stack, while @code{"reg"} means that a
22365 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
22366 be returned in a register.
22368 @item show struct-convention
22369 @kindex show struct-convention
22370 Show the current setting of the convention to return @code{struct}s
22375 @subsubsection Intel(R) @dfn{Memory Protection Extensions} (MPX).
22376 @cindex Intel(R) Memory Protection Extensions (MPX).
22378 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
22379 @footnote{The register named with capital letters represent the architecture
22380 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
22381 which are the lower bound and upper bound. Bounds are effective addresses or
22382 memory locations. The upper bounds are architecturally represented in 1's
22383 complement form. A bound having lower bound = 0, and upper bound = 0
22384 (1's complement of all bits set) will allow access to the entire address space.
22386 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
22387 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
22388 display the upper bound performing the complement of one operation on the
22389 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
22390 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
22391 can also be noted that the upper bounds are inclusive.
22393 As an example, assume that the register BND0 holds bounds for a pointer having
22394 access allowed for the range between 0x32 and 0x71. The values present on
22395 bnd0raw and bnd registers are presented as follows:
22398 bnd0raw = @{0x32, 0xffffffff8e@}
22399 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
22402 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
22403 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
22404 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
22405 Python, the display includes the memory size, in bits, accessible to
22408 Bounds can also be stored in bounds tables, which are stored in
22409 application memory. These tables store bounds for pointers by specifying
22410 the bounds pointer's value along with its bounds. Evaluating and changing
22411 bounds located in bound tables is therefore interesting while investigating
22412 bugs on MPX context. @value{GDBN} provides commands for this purpose:
22415 @item show mpx bound @var{pointer}
22416 @kindex show mpx bound
22417 Display bounds of the given @var{pointer}.
22419 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
22420 @kindex set mpx bound
22421 Set the bounds of a pointer in the bound table.
22422 This command takes three parameters: @var{pointer} is the pointers
22423 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
22424 for lower and upper bounds respectively.
22430 See the following section.
22433 @subsection @acronym{MIPS}
22435 @cindex stack on Alpha
22436 @cindex stack on @acronym{MIPS}
22437 @cindex Alpha stack
22438 @cindex @acronym{MIPS} stack
22439 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
22440 sometimes requires @value{GDBN} to search backward in the object code to
22441 find the beginning of a function.
22443 @cindex response time, @acronym{MIPS} debugging
22444 To improve response time (especially for embedded applications, where
22445 @value{GDBN} may be restricted to a slow serial line for this search)
22446 you may want to limit the size of this search, using one of these
22450 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
22451 @item set heuristic-fence-post @var{limit}
22452 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
22453 search for the beginning of a function. A value of @var{0} (the
22454 default) means there is no limit. However, except for @var{0}, the
22455 larger the limit the more bytes @code{heuristic-fence-post} must search
22456 and therefore the longer it takes to run. You should only need to use
22457 this command when debugging a stripped executable.
22459 @item show heuristic-fence-post
22460 Display the current limit.
22464 These commands are available @emph{only} when @value{GDBN} is configured
22465 for debugging programs on Alpha or @acronym{MIPS} processors.
22467 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
22471 @item set mips abi @var{arg}
22472 @kindex set mips abi
22473 @cindex set ABI for @acronym{MIPS}
22474 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
22475 values of @var{arg} are:
22479 The default ABI associated with the current binary (this is the
22489 @item show mips abi
22490 @kindex show mips abi
22491 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
22493 @item set mips compression @var{arg}
22494 @kindex set mips compression
22495 @cindex code compression, @acronym{MIPS}
22496 Tell @value{GDBN} which @acronym{MIPS} compressed
22497 @acronym{ISA, Instruction Set Architecture} encoding is used by the
22498 inferior. @value{GDBN} uses this for code disassembly and other
22499 internal interpretation purposes. This setting is only referred to
22500 when no executable has been associated with the debugging session or
22501 the executable does not provide information about the encoding it uses.
22502 Otherwise this setting is automatically updated from information
22503 provided by the executable.
22505 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
22506 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
22507 executables containing @acronym{MIPS16} code frequently are not
22508 identified as such.
22510 This setting is ``sticky''; that is, it retains its value across
22511 debugging sessions until reset either explicitly with this command or
22512 implicitly from an executable.
22514 The compiler and/or assembler typically add symbol table annotations to
22515 identify functions compiled for the @acronym{MIPS16} or
22516 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
22517 are present, @value{GDBN} uses them in preference to the global
22518 compressed @acronym{ISA} encoding setting.
22520 @item show mips compression
22521 @kindex show mips compression
22522 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
22523 @value{GDBN} to debug the inferior.
22526 @itemx show mipsfpu
22527 @xref{MIPS Embedded, set mipsfpu}.
22529 @item set mips mask-address @var{arg}
22530 @kindex set mips mask-address
22531 @cindex @acronym{MIPS} addresses, masking
22532 This command determines whether the most-significant 32 bits of 64-bit
22533 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
22534 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
22535 setting, which lets @value{GDBN} determine the correct value.
22537 @item show mips mask-address
22538 @kindex show mips mask-address
22539 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
22542 @item set remote-mips64-transfers-32bit-regs
22543 @kindex set remote-mips64-transfers-32bit-regs
22544 This command controls compatibility with 64-bit @acronym{MIPS} targets that
22545 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
22546 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
22547 and 64 bits for other registers, set this option to @samp{on}.
22549 @item show remote-mips64-transfers-32bit-regs
22550 @kindex show remote-mips64-transfers-32bit-regs
22551 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
22553 @item set debug mips
22554 @kindex set debug mips
22555 This command turns on and off debugging messages for the @acronym{MIPS}-specific
22556 target code in @value{GDBN}.
22558 @item show debug mips
22559 @kindex show debug mips
22560 Show the current setting of @acronym{MIPS} debugging messages.
22566 @cindex HPPA support
22568 When @value{GDBN} is debugging the HP PA architecture, it provides the
22569 following special commands:
22572 @item set debug hppa
22573 @kindex set debug hppa
22574 This command determines whether HPPA architecture-specific debugging
22575 messages are to be displayed.
22577 @item show debug hppa
22578 Show whether HPPA debugging messages are displayed.
22580 @item maint print unwind @var{address}
22581 @kindex maint print unwind@r{, HPPA}
22582 This command displays the contents of the unwind table entry at the
22583 given @var{address}.
22589 @subsection Cell Broadband Engine SPU architecture
22590 @cindex Cell Broadband Engine
22593 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
22594 it provides the following special commands:
22597 @item info spu event
22599 Display SPU event facility status. Shows current event mask
22600 and pending event status.
22602 @item info spu signal
22603 Display SPU signal notification facility status. Shows pending
22604 signal-control word and signal notification mode of both signal
22605 notification channels.
22607 @item info spu mailbox
22608 Display SPU mailbox facility status. Shows all pending entries,
22609 in order of processing, in each of the SPU Write Outbound,
22610 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
22613 Display MFC DMA status. Shows all pending commands in the MFC
22614 DMA queue. For each entry, opcode, tag, class IDs, effective
22615 and local store addresses and transfer size are shown.
22617 @item info spu proxydma
22618 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
22619 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
22620 and local store addresses and transfer size are shown.
22624 When @value{GDBN} is debugging a combined PowerPC/SPU application
22625 on the Cell Broadband Engine, it provides in addition the following
22629 @item set spu stop-on-load @var{arg}
22631 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
22632 will give control to the user when a new SPE thread enters its @code{main}
22633 function. The default is @code{off}.
22635 @item show spu stop-on-load
22637 Show whether to stop for new SPE threads.
22639 @item set spu auto-flush-cache @var{arg}
22640 Set whether to automatically flush the software-managed cache. When set to
22641 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
22642 cache to be flushed whenever SPE execution stops. This provides a consistent
22643 view of PowerPC memory that is accessed via the cache. If an application
22644 does not use the software-managed cache, this option has no effect.
22646 @item show spu auto-flush-cache
22647 Show whether to automatically flush the software-managed cache.
22652 @subsection PowerPC
22653 @cindex PowerPC architecture
22655 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
22656 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
22657 numbers stored in the floating point registers. These values must be stored
22658 in two consecutive registers, always starting at an even register like
22659 @code{f0} or @code{f2}.
22661 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
22662 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
22663 @code{f2} and @code{f3} for @code{$dl1} and so on.
22665 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
22666 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
22669 @subsection Nios II
22670 @cindex Nios II architecture
22672 When @value{GDBN} is debugging the Nios II architecture,
22673 it provides the following special commands:
22677 @item set debug nios2
22678 @kindex set debug nios2
22679 This command turns on and off debugging messages for the Nios II
22680 target code in @value{GDBN}.
22682 @item show debug nios2
22683 @kindex show debug nios2
22684 Show the current setting of Nios II debugging messages.
22687 @node Controlling GDB
22688 @chapter Controlling @value{GDBN}
22690 You can alter the way @value{GDBN} interacts with you by using the
22691 @code{set} command. For commands controlling how @value{GDBN} displays
22692 data, see @ref{Print Settings, ,Print Settings}. Other settings are
22697 * Editing:: Command editing
22698 * Command History:: Command history
22699 * Screen Size:: Screen size
22700 * Numbers:: Numbers
22701 * ABI:: Configuring the current ABI
22702 * Auto-loading:: Automatically loading associated files
22703 * Messages/Warnings:: Optional warnings and messages
22704 * Debugging Output:: Optional messages about internal happenings
22705 * Other Misc Settings:: Other Miscellaneous Settings
22713 @value{GDBN} indicates its readiness to read a command by printing a string
22714 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
22715 can change the prompt string with the @code{set prompt} command. For
22716 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
22717 the prompt in one of the @value{GDBN} sessions so that you can always tell
22718 which one you are talking to.
22720 @emph{Note:} @code{set prompt} does not add a space for you after the
22721 prompt you set. This allows you to set a prompt which ends in a space
22722 or a prompt that does not.
22726 @item set prompt @var{newprompt}
22727 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
22729 @kindex show prompt
22731 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
22734 Versions of @value{GDBN} that ship with Python scripting enabled have
22735 prompt extensions. The commands for interacting with these extensions
22739 @kindex set extended-prompt
22740 @item set extended-prompt @var{prompt}
22741 Set an extended prompt that allows for substitutions.
22742 @xref{gdb.prompt}, for a list of escape sequences that can be used for
22743 substitution. Any escape sequences specified as part of the prompt
22744 string are replaced with the corresponding strings each time the prompt
22750 set extended-prompt Current working directory: \w (gdb)
22753 Note that when an extended-prompt is set, it takes control of the
22754 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
22756 @kindex show extended-prompt
22757 @item show extended-prompt
22758 Prints the extended prompt. Any escape sequences specified as part of
22759 the prompt string with @code{set extended-prompt}, are replaced with the
22760 corresponding strings each time the prompt is displayed.
22764 @section Command Editing
22766 @cindex command line editing
22768 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
22769 @sc{gnu} library provides consistent behavior for programs which provide a
22770 command line interface to the user. Advantages are @sc{gnu} Emacs-style
22771 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
22772 substitution, and a storage and recall of command history across
22773 debugging sessions.
22775 You may control the behavior of command line editing in @value{GDBN} with the
22776 command @code{set}.
22779 @kindex set editing
22782 @itemx set editing on
22783 Enable command line editing (enabled by default).
22785 @item set editing off
22786 Disable command line editing.
22788 @kindex show editing
22790 Show whether command line editing is enabled.
22793 @ifset SYSTEM_READLINE
22794 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
22796 @ifclear SYSTEM_READLINE
22797 @xref{Command Line Editing},
22799 for more details about the Readline
22800 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
22801 encouraged to read that chapter.
22803 @node Command History
22804 @section Command History
22805 @cindex command history
22807 @value{GDBN} can keep track of the commands you type during your
22808 debugging sessions, so that you can be certain of precisely what
22809 happened. Use these commands to manage the @value{GDBN} command
22812 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
22813 package, to provide the history facility.
22814 @ifset SYSTEM_READLINE
22815 @xref{Using History Interactively, , , history, GNU History Library},
22817 @ifclear SYSTEM_READLINE
22818 @xref{Using History Interactively},
22820 for the detailed description of the History library.
22822 To issue a command to @value{GDBN} without affecting certain aspects of
22823 the state which is seen by users, prefix it with @samp{server }
22824 (@pxref{Server Prefix}). This
22825 means that this command will not affect the command history, nor will it
22826 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
22827 pressed on a line by itself.
22829 @cindex @code{server}, command prefix
22830 The server prefix does not affect the recording of values into the value
22831 history; to print a value without recording it into the value history,
22832 use the @code{output} command instead of the @code{print} command.
22834 Here is the description of @value{GDBN} commands related to command
22838 @cindex history substitution
22839 @cindex history file
22840 @kindex set history filename
22841 @cindex @env{GDBHISTFILE}, environment variable
22842 @item set history filename @var{fname}
22843 Set the name of the @value{GDBN} command history file to @var{fname}.
22844 This is the file where @value{GDBN} reads an initial command history
22845 list, and where it writes the command history from this session when it
22846 exits. You can access this list through history expansion or through
22847 the history command editing characters listed below. This file defaults
22848 to the value of the environment variable @code{GDBHISTFILE}, or to
22849 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
22852 @cindex save command history
22853 @kindex set history save
22854 @item set history save
22855 @itemx set history save on
22856 Record command history in a file, whose name may be specified with the
22857 @code{set history filename} command. By default, this option is disabled.
22859 @item set history save off
22860 Stop recording command history in a file.
22862 @cindex history size
22863 @kindex set history size
22864 @cindex @env{GDBHISTSIZE}, environment variable
22865 @item set history size @var{size}
22866 @itemx set history size unlimited
22867 Set the number of commands which @value{GDBN} keeps in its history list.
22868 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
22869 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
22870 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
22871 either a negative number or the empty string, then the number of commands
22872 @value{GDBN} keeps in the history list is unlimited.
22874 @cindex remove duplicate history
22875 @kindex set history remove-duplicates
22876 @item set history remove-duplicates @var{count}
22877 @itemx set history remove-duplicates unlimited
22878 Control the removal of duplicate history entries in the command history list.
22879 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
22880 history entries and remove the first entry that is a duplicate of the current
22881 entry being added to the command history list. If @var{count} is
22882 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
22883 removal of duplicate history entries is disabled.
22885 Only history entries added during the current session are considered for
22886 removal. This option is set to 0 by default.
22890 History expansion assigns special meaning to the character @kbd{!}.
22891 @ifset SYSTEM_READLINE
22892 @xref{Event Designators, , , history, GNU History Library},
22894 @ifclear SYSTEM_READLINE
22895 @xref{Event Designators},
22899 @cindex history expansion, turn on/off
22900 Since @kbd{!} is also the logical not operator in C, history expansion
22901 is off by default. If you decide to enable history expansion with the
22902 @code{set history expansion on} command, you may sometimes need to
22903 follow @kbd{!} (when it is used as logical not, in an expression) with
22904 a space or a tab to prevent it from being expanded. The readline
22905 history facilities do not attempt substitution on the strings
22906 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
22908 The commands to control history expansion are:
22911 @item set history expansion on
22912 @itemx set history expansion
22913 @kindex set history expansion
22914 Enable history expansion. History expansion is off by default.
22916 @item set history expansion off
22917 Disable history expansion.
22920 @kindex show history
22922 @itemx show history filename
22923 @itemx show history save
22924 @itemx show history size
22925 @itemx show history expansion
22926 These commands display the state of the @value{GDBN} history parameters.
22927 @code{show history} by itself displays all four states.
22932 @kindex show commands
22933 @cindex show last commands
22934 @cindex display command history
22935 @item show commands
22936 Display the last ten commands in the command history.
22938 @item show commands @var{n}
22939 Print ten commands centered on command number @var{n}.
22941 @item show commands +
22942 Print ten commands just after the commands last printed.
22946 @section Screen Size
22947 @cindex size of screen
22948 @cindex screen size
22951 @cindex pauses in output
22953 Certain commands to @value{GDBN} may produce large amounts of
22954 information output to the screen. To help you read all of it,
22955 @value{GDBN} pauses and asks you for input at the end of each page of
22956 output. Type @key{RET} when you want to continue the output, or @kbd{q}
22957 to discard the remaining output. Also, the screen width setting
22958 determines when to wrap lines of output. Depending on what is being
22959 printed, @value{GDBN} tries to break the line at a readable place,
22960 rather than simply letting it overflow onto the following line.
22962 Normally @value{GDBN} knows the size of the screen from the terminal
22963 driver software. For example, on Unix @value{GDBN} uses the termcap data base
22964 together with the value of the @code{TERM} environment variable and the
22965 @code{stty rows} and @code{stty cols} settings. If this is not correct,
22966 you can override it with the @code{set height} and @code{set
22973 @kindex show height
22974 @item set height @var{lpp}
22975 @itemx set height unlimited
22977 @itemx set width @var{cpl}
22978 @itemx set width unlimited
22980 These @code{set} commands specify a screen height of @var{lpp} lines and
22981 a screen width of @var{cpl} characters. The associated @code{show}
22982 commands display the current settings.
22984 If you specify a height of either @code{unlimited} or zero lines,
22985 @value{GDBN} does not pause during output no matter how long the
22986 output is. This is useful if output is to a file or to an editor
22989 Likewise, you can specify @samp{set width unlimited} or @samp{set
22990 width 0} to prevent @value{GDBN} from wrapping its output.
22992 @item set pagination on
22993 @itemx set pagination off
22994 @kindex set pagination
22995 Turn the output pagination on or off; the default is on. Turning
22996 pagination off is the alternative to @code{set height unlimited}. Note that
22997 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
22998 Options, -batch}) also automatically disables pagination.
23000 @item show pagination
23001 @kindex show pagination
23002 Show the current pagination mode.
23007 @cindex number representation
23008 @cindex entering numbers
23010 You can always enter numbers in octal, decimal, or hexadecimal in
23011 @value{GDBN} by the usual conventions: octal numbers begin with
23012 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
23013 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
23014 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
23015 10; likewise, the default display for numbers---when no particular
23016 format is specified---is base 10. You can change the default base for
23017 both input and output with the commands described below.
23020 @kindex set input-radix
23021 @item set input-radix @var{base}
23022 Set the default base for numeric input. Supported choices
23023 for @var{base} are decimal 8, 10, or 16. The base must itself be
23024 specified either unambiguously or using the current input radix; for
23028 set input-radix 012
23029 set input-radix 10.
23030 set input-radix 0xa
23034 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
23035 leaves the input radix unchanged, no matter what it was, since
23036 @samp{10}, being without any leading or trailing signs of its base, is
23037 interpreted in the current radix. Thus, if the current radix is 16,
23038 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
23041 @kindex set output-radix
23042 @item set output-radix @var{base}
23043 Set the default base for numeric display. Supported choices
23044 for @var{base} are decimal 8, 10, or 16. The base must itself be
23045 specified either unambiguously or using the current input radix.
23047 @kindex show input-radix
23048 @item show input-radix
23049 Display the current default base for numeric input.
23051 @kindex show output-radix
23052 @item show output-radix
23053 Display the current default base for numeric display.
23055 @item set radix @r{[}@var{base}@r{]}
23059 These commands set and show the default base for both input and output
23060 of numbers. @code{set radix} sets the radix of input and output to
23061 the same base; without an argument, it resets the radix back to its
23062 default value of 10.
23067 @section Configuring the Current ABI
23069 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
23070 application automatically. However, sometimes you need to override its
23071 conclusions. Use these commands to manage @value{GDBN}'s view of the
23077 @cindex Newlib OS ABI and its influence on the longjmp handling
23079 One @value{GDBN} configuration can debug binaries for multiple operating
23080 system targets, either via remote debugging or native emulation.
23081 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
23082 but you can override its conclusion using the @code{set osabi} command.
23083 One example where this is useful is in debugging of binaries which use
23084 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
23085 not have the same identifying marks that the standard C library for your
23088 When @value{GDBN} is debugging the AArch64 architecture, it provides a
23089 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
23090 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
23091 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
23095 Show the OS ABI currently in use.
23098 With no argument, show the list of registered available OS ABI's.
23100 @item set osabi @var{abi}
23101 Set the current OS ABI to @var{abi}.
23104 @cindex float promotion
23106 Generally, the way that an argument of type @code{float} is passed to a
23107 function depends on whether the function is prototyped. For a prototyped
23108 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
23109 according to the architecture's convention for @code{float}. For unprototyped
23110 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
23111 @code{double} and then passed.
23113 Unfortunately, some forms of debug information do not reliably indicate whether
23114 a function is prototyped. If @value{GDBN} calls a function that is not marked
23115 as prototyped, it consults @kbd{set coerce-float-to-double}.
23118 @kindex set coerce-float-to-double
23119 @item set coerce-float-to-double
23120 @itemx set coerce-float-to-double on
23121 Arguments of type @code{float} will be promoted to @code{double} when passed
23122 to an unprototyped function. This is the default setting.
23124 @item set coerce-float-to-double off
23125 Arguments of type @code{float} will be passed directly to unprototyped
23128 @kindex show coerce-float-to-double
23129 @item show coerce-float-to-double
23130 Show the current setting of promoting @code{float} to @code{double}.
23134 @kindex show cp-abi
23135 @value{GDBN} needs to know the ABI used for your program's C@t{++}
23136 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
23137 used to build your application. @value{GDBN} only fully supports
23138 programs with a single C@t{++} ABI; if your program contains code using
23139 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
23140 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
23141 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
23142 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
23143 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
23144 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
23149 Show the C@t{++} ABI currently in use.
23152 With no argument, show the list of supported C@t{++} ABI's.
23154 @item set cp-abi @var{abi}
23155 @itemx set cp-abi auto
23156 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
23160 @section Automatically loading associated files
23161 @cindex auto-loading
23163 @value{GDBN} sometimes reads files with commands and settings automatically,
23164 without being explicitly told so by the user. We call this feature
23165 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
23166 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
23167 results or introduce security risks (e.g., if the file comes from untrusted
23171 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
23172 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
23174 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
23175 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
23178 There are various kinds of files @value{GDBN} can automatically load.
23179 In addition to these files, @value{GDBN} supports auto-loading code written
23180 in various extension languages. @xref{Auto-loading extensions}.
23182 Note that loading of these associated files (including the local @file{.gdbinit}
23183 file) requires accordingly configured @code{auto-load safe-path}
23184 (@pxref{Auto-loading safe path}).
23186 For these reasons, @value{GDBN} includes commands and options to let you
23187 control when to auto-load files and which files should be auto-loaded.
23190 @anchor{set auto-load off}
23191 @kindex set auto-load off
23192 @item set auto-load off
23193 Globally disable loading of all auto-loaded files.
23194 You may want to use this command with the @samp{-iex} option
23195 (@pxref{Option -init-eval-command}) such as:
23197 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
23200 Be aware that system init file (@pxref{System-wide configuration})
23201 and init files from your home directory (@pxref{Home Directory Init File})
23202 still get read (as they come from generally trusted directories).
23203 To prevent @value{GDBN} from auto-loading even those init files, use the
23204 @option{-nx} option (@pxref{Mode Options}), in addition to
23205 @code{set auto-load no}.
23207 @anchor{show auto-load}
23208 @kindex show auto-load
23209 @item show auto-load
23210 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
23214 (gdb) show auto-load
23215 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
23216 libthread-db: Auto-loading of inferior specific libthread_db is on.
23217 local-gdbinit: Auto-loading of .gdbinit script from current directory
23219 python-scripts: Auto-loading of Python scripts is on.
23220 safe-path: List of directories from which it is safe to auto-load files
23221 is $debugdir:$datadir/auto-load.
23222 scripts-directory: List of directories from which to load auto-loaded scripts
23223 is $debugdir:$datadir/auto-load.
23226 @anchor{info auto-load}
23227 @kindex info auto-load
23228 @item info auto-load
23229 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
23233 (gdb) info auto-load
23236 Yes /home/user/gdb/gdb-gdb.gdb
23237 libthread-db: No auto-loaded libthread-db.
23238 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
23242 Yes /home/user/gdb/gdb-gdb.py
23246 These are @value{GDBN} control commands for the auto-loading:
23248 @multitable @columnfractions .5 .5
23249 @item @xref{set auto-load off}.
23250 @tab Disable auto-loading globally.
23251 @item @xref{show auto-load}.
23252 @tab Show setting of all kinds of files.
23253 @item @xref{info auto-load}.
23254 @tab Show state of all kinds of files.
23255 @item @xref{set auto-load gdb-scripts}.
23256 @tab Control for @value{GDBN} command scripts.
23257 @item @xref{show auto-load gdb-scripts}.
23258 @tab Show setting of @value{GDBN} command scripts.
23259 @item @xref{info auto-load gdb-scripts}.
23260 @tab Show state of @value{GDBN} command scripts.
23261 @item @xref{set auto-load python-scripts}.
23262 @tab Control for @value{GDBN} Python scripts.
23263 @item @xref{show auto-load python-scripts}.
23264 @tab Show setting of @value{GDBN} Python scripts.
23265 @item @xref{info auto-load python-scripts}.
23266 @tab Show state of @value{GDBN} Python scripts.
23267 @item @xref{set auto-load guile-scripts}.
23268 @tab Control for @value{GDBN} Guile scripts.
23269 @item @xref{show auto-load guile-scripts}.
23270 @tab Show setting of @value{GDBN} Guile scripts.
23271 @item @xref{info auto-load guile-scripts}.
23272 @tab Show state of @value{GDBN} Guile scripts.
23273 @item @xref{set auto-load scripts-directory}.
23274 @tab Control for @value{GDBN} auto-loaded scripts location.
23275 @item @xref{show auto-load scripts-directory}.
23276 @tab Show @value{GDBN} auto-loaded scripts location.
23277 @item @xref{add-auto-load-scripts-directory}.
23278 @tab Add directory for auto-loaded scripts location list.
23279 @item @xref{set auto-load local-gdbinit}.
23280 @tab Control for init file in the current directory.
23281 @item @xref{show auto-load local-gdbinit}.
23282 @tab Show setting of init file in the current directory.
23283 @item @xref{info auto-load local-gdbinit}.
23284 @tab Show state of init file in the current directory.
23285 @item @xref{set auto-load libthread-db}.
23286 @tab Control for thread debugging library.
23287 @item @xref{show auto-load libthread-db}.
23288 @tab Show setting of thread debugging library.
23289 @item @xref{info auto-load libthread-db}.
23290 @tab Show state of thread debugging library.
23291 @item @xref{set auto-load safe-path}.
23292 @tab Control directories trusted for automatic loading.
23293 @item @xref{show auto-load safe-path}.
23294 @tab Show directories trusted for automatic loading.
23295 @item @xref{add-auto-load-safe-path}.
23296 @tab Add directory trusted for automatic loading.
23299 @node Init File in the Current Directory
23300 @subsection Automatically loading init file in the current directory
23301 @cindex auto-loading init file in the current directory
23303 By default, @value{GDBN} reads and executes the canned sequences of commands
23304 from init file (if any) in the current working directory,
23305 see @ref{Init File in the Current Directory during Startup}.
23307 Note that loading of this local @file{.gdbinit} file also requires accordingly
23308 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23311 @anchor{set auto-load local-gdbinit}
23312 @kindex set auto-load local-gdbinit
23313 @item set auto-load local-gdbinit [on|off]
23314 Enable or disable the auto-loading of canned sequences of commands
23315 (@pxref{Sequences}) found in init file in the current directory.
23317 @anchor{show auto-load local-gdbinit}
23318 @kindex show auto-load local-gdbinit
23319 @item show auto-load local-gdbinit
23320 Show whether auto-loading of canned sequences of commands from init file in the
23321 current directory is enabled or disabled.
23323 @anchor{info auto-load local-gdbinit}
23324 @kindex info auto-load local-gdbinit
23325 @item info auto-load local-gdbinit
23326 Print whether canned sequences of commands from init file in the
23327 current directory have been auto-loaded.
23330 @node libthread_db.so.1 file
23331 @subsection Automatically loading thread debugging library
23332 @cindex auto-loading libthread_db.so.1
23334 This feature is currently present only on @sc{gnu}/Linux native hosts.
23336 @value{GDBN} reads in some cases thread debugging library from places specific
23337 to the inferior (@pxref{set libthread-db-search-path}).
23339 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
23340 without checking this @samp{set auto-load libthread-db} switch as system
23341 libraries have to be trusted in general. In all other cases of
23342 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
23343 auto-load libthread-db} is enabled before trying to open such thread debugging
23346 Note that loading of this debugging library also requires accordingly configured
23347 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23350 @anchor{set auto-load libthread-db}
23351 @kindex set auto-load libthread-db
23352 @item set auto-load libthread-db [on|off]
23353 Enable or disable the auto-loading of inferior specific thread debugging library.
23355 @anchor{show auto-load libthread-db}
23356 @kindex show auto-load libthread-db
23357 @item show auto-load libthread-db
23358 Show whether auto-loading of inferior specific thread debugging library is
23359 enabled or disabled.
23361 @anchor{info auto-load libthread-db}
23362 @kindex info auto-load libthread-db
23363 @item info auto-load libthread-db
23364 Print the list of all loaded inferior specific thread debugging libraries and
23365 for each such library print list of inferior @var{pid}s using it.
23368 @node Auto-loading safe path
23369 @subsection Security restriction for auto-loading
23370 @cindex auto-loading safe-path
23372 As the files of inferior can come from untrusted source (such as submitted by
23373 an application user) @value{GDBN} does not always load any files automatically.
23374 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
23375 directories trusted for loading files not explicitly requested by user.
23376 Each directory can also be a shell wildcard pattern.
23378 If the path is not set properly you will see a warning and the file will not
23383 Reading symbols from /home/user/gdb/gdb...done.
23384 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
23385 declined by your `auto-load safe-path' set
23386 to "$debugdir:$datadir/auto-load".
23387 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
23388 declined by your `auto-load safe-path' set
23389 to "$debugdir:$datadir/auto-load".
23393 To instruct @value{GDBN} to go ahead and use the init files anyway,
23394 invoke @value{GDBN} like this:
23397 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
23400 The list of trusted directories is controlled by the following commands:
23403 @anchor{set auto-load safe-path}
23404 @kindex set auto-load safe-path
23405 @item set auto-load safe-path @r{[}@var{directories}@r{]}
23406 Set the list of directories (and their subdirectories) trusted for automatic
23407 loading and execution of scripts. You can also enter a specific trusted file.
23408 Each directory can also be a shell wildcard pattern; wildcards do not match
23409 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
23410 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
23411 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
23412 its default value as specified during @value{GDBN} compilation.
23414 The list of directories uses path separator (@samp{:} on GNU and Unix
23415 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
23416 to the @env{PATH} environment variable.
23418 @anchor{show auto-load safe-path}
23419 @kindex show auto-load safe-path
23420 @item show auto-load safe-path
23421 Show the list of directories trusted for automatic loading and execution of
23424 @anchor{add-auto-load-safe-path}
23425 @kindex add-auto-load-safe-path
23426 @item add-auto-load-safe-path
23427 Add an entry (or list of entries) to the list of directories trusted for
23428 automatic loading and execution of scripts. Multiple entries may be delimited
23429 by the host platform path separator in use.
23432 This variable defaults to what @code{--with-auto-load-dir} has been configured
23433 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
23434 substitution applies the same as for @ref{set auto-load scripts-directory}.
23435 The default @code{set auto-load safe-path} value can be also overriden by
23436 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
23438 Setting this variable to @file{/} disables this security protection,
23439 corresponding @value{GDBN} configuration option is
23440 @option{--without-auto-load-safe-path}.
23441 This variable is supposed to be set to the system directories writable by the
23442 system superuser only. Users can add their source directories in init files in
23443 their home directories (@pxref{Home Directory Init File}). See also deprecated
23444 init file in the current directory
23445 (@pxref{Init File in the Current Directory during Startup}).
23447 To force @value{GDBN} to load the files it declined to load in the previous
23448 example, you could use one of the following ways:
23451 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
23452 Specify this trusted directory (or a file) as additional component of the list.
23453 You have to specify also any existing directories displayed by
23454 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
23456 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
23457 Specify this directory as in the previous case but just for a single
23458 @value{GDBN} session.
23460 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
23461 Disable auto-loading safety for a single @value{GDBN} session.
23462 This assumes all the files you debug during this @value{GDBN} session will come
23463 from trusted sources.
23465 @item @kbd{./configure --without-auto-load-safe-path}
23466 During compilation of @value{GDBN} you may disable any auto-loading safety.
23467 This assumes all the files you will ever debug with this @value{GDBN} come from
23471 On the other hand you can also explicitly forbid automatic files loading which
23472 also suppresses any such warning messages:
23475 @item @kbd{gdb -iex "set auto-load no" @dots{}}
23476 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
23478 @item @file{~/.gdbinit}: @samp{set auto-load no}
23479 Disable auto-loading globally for the user
23480 (@pxref{Home Directory Init File}). While it is improbable, you could also
23481 use system init file instead (@pxref{System-wide configuration}).
23484 This setting applies to the file names as entered by user. If no entry matches
23485 @value{GDBN} tries as a last resort to also resolve all the file names into
23486 their canonical form (typically resolving symbolic links) and compare the
23487 entries again. @value{GDBN} already canonicalizes most of the filenames on its
23488 own before starting the comparison so a canonical form of directories is
23489 recommended to be entered.
23491 @node Auto-loading verbose mode
23492 @subsection Displaying files tried for auto-load
23493 @cindex auto-loading verbose mode
23495 For better visibility of all the file locations where you can place scripts to
23496 be auto-loaded with inferior --- or to protect yourself against accidental
23497 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
23498 all the files attempted to be loaded. Both existing and non-existing files may
23501 For example the list of directories from which it is safe to auto-load files
23502 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
23503 may not be too obvious while setting it up.
23506 (gdb) set debug auto-load on
23507 (gdb) file ~/src/t/true
23508 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
23509 for objfile "/tmp/true".
23510 auto-load: Updating directories of "/usr:/opt".
23511 auto-load: Using directory "/usr".
23512 auto-load: Using directory "/opt".
23513 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
23514 by your `auto-load safe-path' set to "/usr:/opt".
23518 @anchor{set debug auto-load}
23519 @kindex set debug auto-load
23520 @item set debug auto-load [on|off]
23521 Set whether to print the filenames attempted to be auto-loaded.
23523 @anchor{show debug auto-load}
23524 @kindex show debug auto-load
23525 @item show debug auto-load
23526 Show whether printing of the filenames attempted to be auto-loaded is turned
23530 @node Messages/Warnings
23531 @section Optional Warnings and Messages
23533 @cindex verbose operation
23534 @cindex optional warnings
23535 By default, @value{GDBN} is silent about its inner workings. If you are
23536 running on a slow machine, you may want to use the @code{set verbose}
23537 command. This makes @value{GDBN} tell you when it does a lengthy
23538 internal operation, so you will not think it has crashed.
23540 Currently, the messages controlled by @code{set verbose} are those
23541 which announce that the symbol table for a source file is being read;
23542 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
23545 @kindex set verbose
23546 @item set verbose on
23547 Enables @value{GDBN} output of certain informational messages.
23549 @item set verbose off
23550 Disables @value{GDBN} output of certain informational messages.
23552 @kindex show verbose
23554 Displays whether @code{set verbose} is on or off.
23557 By default, if @value{GDBN} encounters bugs in the symbol table of an
23558 object file, it is silent; but if you are debugging a compiler, you may
23559 find this information useful (@pxref{Symbol Errors, ,Errors Reading
23564 @kindex set complaints
23565 @item set complaints @var{limit}
23566 Permits @value{GDBN} to output @var{limit} complaints about each type of
23567 unusual symbols before becoming silent about the problem. Set
23568 @var{limit} to zero to suppress all complaints; set it to a large number
23569 to prevent complaints from being suppressed.
23571 @kindex show complaints
23572 @item show complaints
23573 Displays how many symbol complaints @value{GDBN} is permitted to produce.
23577 @anchor{confirmation requests}
23578 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
23579 lot of stupid questions to confirm certain commands. For example, if
23580 you try to run a program which is already running:
23584 The program being debugged has been started already.
23585 Start it from the beginning? (y or n)
23588 If you are willing to unflinchingly face the consequences of your own
23589 commands, you can disable this ``feature'':
23593 @kindex set confirm
23595 @cindex confirmation
23596 @cindex stupid questions
23597 @item set confirm off
23598 Disables confirmation requests. Note that running @value{GDBN} with
23599 the @option{--batch} option (@pxref{Mode Options, -batch}) also
23600 automatically disables confirmation requests.
23602 @item set confirm on
23603 Enables confirmation requests (the default).
23605 @kindex show confirm
23607 Displays state of confirmation requests.
23611 @cindex command tracing
23612 If you need to debug user-defined commands or sourced files you may find it
23613 useful to enable @dfn{command tracing}. In this mode each command will be
23614 printed as it is executed, prefixed with one or more @samp{+} symbols, the
23615 quantity denoting the call depth of each command.
23618 @kindex set trace-commands
23619 @cindex command scripts, debugging
23620 @item set trace-commands on
23621 Enable command tracing.
23622 @item set trace-commands off
23623 Disable command tracing.
23624 @item show trace-commands
23625 Display the current state of command tracing.
23628 @node Debugging Output
23629 @section Optional Messages about Internal Happenings
23630 @cindex optional debugging messages
23632 @value{GDBN} has commands that enable optional debugging messages from
23633 various @value{GDBN} subsystems; normally these commands are of
23634 interest to @value{GDBN} maintainers, or when reporting a bug. This
23635 section documents those commands.
23638 @kindex set exec-done-display
23639 @item set exec-done-display
23640 Turns on or off the notification of asynchronous commands'
23641 completion. When on, @value{GDBN} will print a message when an
23642 asynchronous command finishes its execution. The default is off.
23643 @kindex show exec-done-display
23644 @item show exec-done-display
23645 Displays the current setting of asynchronous command completion
23648 @cindex ARM AArch64
23649 @item set debug aarch64
23650 Turns on or off display of debugging messages related to ARM AArch64.
23651 The default is off.
23653 @item show debug aarch64
23654 Displays the current state of displaying debugging messages related to
23656 @cindex gdbarch debugging info
23657 @cindex architecture debugging info
23658 @item set debug arch
23659 Turns on or off display of gdbarch debugging info. The default is off
23660 @item show debug arch
23661 Displays the current state of displaying gdbarch debugging info.
23662 @item set debug aix-solib
23663 @cindex AIX shared library debugging
23664 Control display of debugging messages from the AIX shared library
23665 support module. The default is off.
23666 @item show debug aix-thread
23667 Show the current state of displaying AIX shared library debugging messages.
23668 @item set debug aix-thread
23669 @cindex AIX threads
23670 Display debugging messages about inner workings of the AIX thread
23672 @item show debug aix-thread
23673 Show the current state of AIX thread debugging info display.
23674 @item set debug check-physname
23676 Check the results of the ``physname'' computation. When reading DWARF
23677 debugging information for C@t{++}, @value{GDBN} attempts to compute
23678 each entity's name. @value{GDBN} can do this computation in two
23679 different ways, depending on exactly what information is present.
23680 When enabled, this setting causes @value{GDBN} to compute the names
23681 both ways and display any discrepancies.
23682 @item show debug check-physname
23683 Show the current state of ``physname'' checking.
23684 @item set debug coff-pe-read
23685 @cindex COFF/PE exported symbols
23686 Control display of debugging messages related to reading of COFF/PE
23687 exported symbols. The default is off.
23688 @item show debug coff-pe-read
23689 Displays the current state of displaying debugging messages related to
23690 reading of COFF/PE exported symbols.
23691 @item set debug dwarf-die
23693 Dump DWARF DIEs after they are read in.
23694 The value is the number of nesting levels to print.
23695 A value of zero turns off the display.
23696 @item show debug dwarf-die
23697 Show the current state of DWARF DIE debugging.
23698 @item set debug dwarf-line
23699 @cindex DWARF Line Tables
23700 Turns on or off display of debugging messages related to reading
23701 DWARF line tables. The default is 0 (off).
23702 A value of 1 provides basic information.
23703 A value greater than 1 provides more verbose information.
23704 @item show debug dwarf-line
23705 Show the current state of DWARF line table debugging.
23706 @item set debug dwarf-read
23707 @cindex DWARF Reading
23708 Turns on or off display of debugging messages related to reading
23709 DWARF debug info. The default is 0 (off).
23710 A value of 1 provides basic information.
23711 A value greater than 1 provides more verbose information.
23712 @item show debug dwarf-read
23713 Show the current state of DWARF reader debugging.
23714 @item set debug displaced
23715 @cindex displaced stepping debugging info
23716 Turns on or off display of @value{GDBN} debugging info for the
23717 displaced stepping support. The default is off.
23718 @item show debug displaced
23719 Displays the current state of displaying @value{GDBN} debugging info
23720 related to displaced stepping.
23721 @item set debug event
23722 @cindex event debugging info
23723 Turns on or off display of @value{GDBN} event debugging info. The
23725 @item show debug event
23726 Displays the current state of displaying @value{GDBN} event debugging
23728 @item set debug expression
23729 @cindex expression debugging info
23730 Turns on or off display of debugging info about @value{GDBN}
23731 expression parsing. The default is off.
23732 @item show debug expression
23733 Displays the current state of displaying debugging info about
23734 @value{GDBN} expression parsing.
23735 @item set debug frame
23736 @cindex frame debugging info
23737 Turns on or off display of @value{GDBN} frame debugging info. The
23739 @item show debug frame
23740 Displays the current state of displaying @value{GDBN} frame debugging
23742 @item set debug gnu-nat
23743 @cindex @sc{gnu}/Hurd debug messages
23744 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
23745 @item show debug gnu-nat
23746 Show the current state of @sc{gnu}/Hurd debugging messages.
23747 @item set debug infrun
23748 @cindex inferior debugging info
23749 Turns on or off display of @value{GDBN} debugging info for running the inferior.
23750 The default is off. @file{infrun.c} contains GDB's runtime state machine used
23751 for implementing operations such as single-stepping the inferior.
23752 @item show debug infrun
23753 Displays the current state of @value{GDBN} inferior debugging.
23754 @item set debug jit
23755 @cindex just-in-time compilation, debugging messages
23756 Turns on or off debugging messages from JIT debug support.
23757 @item show debug jit
23758 Displays the current state of @value{GDBN} JIT debugging.
23759 @item set debug lin-lwp
23760 @cindex @sc{gnu}/Linux LWP debug messages
23761 @cindex Linux lightweight processes
23762 Turns on or off debugging messages from the Linux LWP debug support.
23763 @item show debug lin-lwp
23764 Show the current state of Linux LWP debugging messages.
23765 @item set debug linux-namespaces
23766 @cindex @sc{gnu}/Linux namespaces debug messages
23767 Turns on or off debugging messages from the Linux namespaces debug support.
23768 @item show debug linux-namespaces
23769 Show the current state of Linux namespaces debugging messages.
23770 @item set debug mach-o
23771 @cindex Mach-O symbols processing
23772 Control display of debugging messages related to Mach-O symbols
23773 processing. The default is off.
23774 @item show debug mach-o
23775 Displays the current state of displaying debugging messages related to
23776 reading of COFF/PE exported symbols.
23777 @item set debug notification
23778 @cindex remote async notification debugging info
23779 Turns on or off debugging messages about remote async notification.
23780 The default is off.
23781 @item show debug notification
23782 Displays the current state of remote async notification debugging messages.
23783 @item set debug observer
23784 @cindex observer debugging info
23785 Turns on or off display of @value{GDBN} observer debugging. This
23786 includes info such as the notification of observable events.
23787 @item show debug observer
23788 Displays the current state of observer debugging.
23789 @item set debug overload
23790 @cindex C@t{++} overload debugging info
23791 Turns on or off display of @value{GDBN} C@t{++} overload debugging
23792 info. This includes info such as ranking of functions, etc. The default
23794 @item show debug overload
23795 Displays the current state of displaying @value{GDBN} C@t{++} overload
23797 @cindex expression parser, debugging info
23798 @cindex debug expression parser
23799 @item set debug parser
23800 Turns on or off the display of expression parser debugging output.
23801 Internally, this sets the @code{yydebug} variable in the expression
23802 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
23803 details. The default is off.
23804 @item show debug parser
23805 Show the current state of expression parser debugging.
23806 @cindex packets, reporting on stdout
23807 @cindex serial connections, debugging
23808 @cindex debug remote protocol
23809 @cindex remote protocol debugging
23810 @cindex display remote packets
23811 @item set debug remote
23812 Turns on or off display of reports on all packets sent back and forth across
23813 the serial line to the remote machine. The info is printed on the
23814 @value{GDBN} standard output stream. The default is off.
23815 @item show debug remote
23816 Displays the state of display of remote packets.
23817 @item set debug serial
23818 Turns on or off display of @value{GDBN} serial debugging info. The
23820 @item show debug serial
23821 Displays the current state of displaying @value{GDBN} serial debugging
23823 @item set debug solib-frv
23824 @cindex FR-V shared-library debugging
23825 Turns on or off debugging messages for FR-V shared-library code.
23826 @item show debug solib-frv
23827 Display the current state of FR-V shared-library code debugging
23829 @item set debug symbol-lookup
23830 @cindex symbol lookup
23831 Turns on or off display of debugging messages related to symbol lookup.
23832 The default is 0 (off).
23833 A value of 1 provides basic information.
23834 A value greater than 1 provides more verbose information.
23835 @item show debug symbol-lookup
23836 Show the current state of symbol lookup debugging messages.
23837 @item set debug symfile
23838 @cindex symbol file functions
23839 Turns on or off display of debugging messages related to symbol file functions.
23840 The default is off. @xref{Files}.
23841 @item show debug symfile
23842 Show the current state of symbol file debugging messages.
23843 @item set debug symtab-create
23844 @cindex symbol table creation
23845 Turns on or off display of debugging messages related to symbol table creation.
23846 The default is 0 (off).
23847 A value of 1 provides basic information.
23848 A value greater than 1 provides more verbose information.
23849 @item show debug symtab-create
23850 Show the current state of symbol table creation debugging.
23851 @item set debug target
23852 @cindex target debugging info
23853 Turns on or off display of @value{GDBN} target debugging info. This info
23854 includes what is going on at the target level of GDB, as it happens. The
23855 default is 0. Set it to 1 to track events, and to 2 to also track the
23856 value of large memory transfers.
23857 @item show debug target
23858 Displays the current state of displaying @value{GDBN} target debugging
23860 @item set debug timestamp
23861 @cindex timestampping debugging info
23862 Turns on or off display of timestamps with @value{GDBN} debugging info.
23863 When enabled, seconds and microseconds are displayed before each debugging
23865 @item show debug timestamp
23866 Displays the current state of displaying timestamps with @value{GDBN}
23868 @item set debug varobj
23869 @cindex variable object debugging info
23870 Turns on or off display of @value{GDBN} variable object debugging
23871 info. The default is off.
23872 @item show debug varobj
23873 Displays the current state of displaying @value{GDBN} variable object
23875 @item set debug xml
23876 @cindex XML parser debugging
23877 Turns on or off debugging messages for built-in XML parsers.
23878 @item show debug xml
23879 Displays the current state of XML debugging messages.
23882 @node Other Misc Settings
23883 @section Other Miscellaneous Settings
23884 @cindex miscellaneous settings
23887 @kindex set interactive-mode
23888 @item set interactive-mode
23889 If @code{on}, forces @value{GDBN} to assume that GDB was started
23890 in a terminal. In practice, this means that @value{GDBN} should wait
23891 for the user to answer queries generated by commands entered at
23892 the command prompt. If @code{off}, forces @value{GDBN} to operate
23893 in the opposite mode, and it uses the default answers to all queries.
23894 If @code{auto} (the default), @value{GDBN} tries to determine whether
23895 its standard input is a terminal, and works in interactive-mode if it
23896 is, non-interactively otherwise.
23898 In the vast majority of cases, the debugger should be able to guess
23899 correctly which mode should be used. But this setting can be useful
23900 in certain specific cases, such as running a MinGW @value{GDBN}
23901 inside a cygwin window.
23903 @kindex show interactive-mode
23904 @item show interactive-mode
23905 Displays whether the debugger is operating in interactive mode or not.
23908 @node Extending GDB
23909 @chapter Extending @value{GDBN}
23910 @cindex extending GDB
23912 @value{GDBN} provides several mechanisms for extension.
23913 @value{GDBN} also provides the ability to automatically load
23914 extensions when it reads a file for debugging. This allows the
23915 user to automatically customize @value{GDBN} for the program
23919 * Sequences:: Canned Sequences of @value{GDBN} Commands
23920 * Python:: Extending @value{GDBN} using Python
23921 * Guile:: Extending @value{GDBN} using Guile
23922 * Auto-loading extensions:: Automatically loading extensions
23923 * Multiple Extension Languages:: Working with multiple extension languages
23924 * Aliases:: Creating new spellings of existing commands
23927 To facilitate the use of extension languages, @value{GDBN} is capable
23928 of evaluating the contents of a file. When doing so, @value{GDBN}
23929 can recognize which extension language is being used by looking at
23930 the filename extension. Files with an unrecognized filename extension
23931 are always treated as a @value{GDBN} Command Files.
23932 @xref{Command Files,, Command files}.
23934 You can control how @value{GDBN} evaluates these files with the following
23938 @kindex set script-extension
23939 @kindex show script-extension
23940 @item set script-extension off
23941 All scripts are always evaluated as @value{GDBN} Command Files.
23943 @item set script-extension soft
23944 The debugger determines the scripting language based on filename
23945 extension. If this scripting language is supported, @value{GDBN}
23946 evaluates the script using that language. Otherwise, it evaluates
23947 the file as a @value{GDBN} Command File.
23949 @item set script-extension strict
23950 The debugger determines the scripting language based on filename
23951 extension, and evaluates the script using that language. If the
23952 language is not supported, then the evaluation fails.
23954 @item show script-extension
23955 Display the current value of the @code{script-extension} option.
23960 @section Canned Sequences of Commands
23962 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
23963 Command Lists}), @value{GDBN} provides two ways to store sequences of
23964 commands for execution as a unit: user-defined commands and command
23968 * Define:: How to define your own commands
23969 * Hooks:: Hooks for user-defined commands
23970 * Command Files:: How to write scripts of commands to be stored in a file
23971 * Output:: Commands for controlled output
23972 * Auto-loading sequences:: Controlling auto-loaded command files
23976 @subsection User-defined Commands
23978 @cindex user-defined command
23979 @cindex arguments, to user-defined commands
23980 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
23981 which you assign a new name as a command. This is done with the
23982 @code{define} command. User commands may accept up to 10 arguments
23983 separated by whitespace. Arguments are accessed within the user command
23984 via @code{$arg0@dots{}$arg9}. A trivial example:
23988 print $arg0 + $arg1 + $arg2
23993 To execute the command use:
24000 This defines the command @code{adder}, which prints the sum of
24001 its three arguments. Note the arguments are text substitutions, so they may
24002 reference variables, use complex expressions, or even perform inferior
24005 @cindex argument count in user-defined commands
24006 @cindex how many arguments (user-defined commands)
24007 In addition, @code{$argc} may be used to find out how many arguments have
24008 been passed. This expands to a number in the range 0@dots{}10.
24013 print $arg0 + $arg1
24016 print $arg0 + $arg1 + $arg2
24024 @item define @var{commandname}
24025 Define a command named @var{commandname}. If there is already a command
24026 by that name, you are asked to confirm that you want to redefine it.
24027 The argument @var{commandname} may be a bare command name consisting of letters,
24028 numbers, dashes, and underscores. It may also start with any predefined
24029 prefix command. For example, @samp{define target my-target} creates
24030 a user-defined @samp{target my-target} command.
24032 The definition of the command is made up of other @value{GDBN} command lines,
24033 which are given following the @code{define} command. The end of these
24034 commands is marked by a line containing @code{end}.
24037 @kindex end@r{ (user-defined commands)}
24038 @item document @var{commandname}
24039 Document the user-defined command @var{commandname}, so that it can be
24040 accessed by @code{help}. The command @var{commandname} must already be
24041 defined. This command reads lines of documentation just as @code{define}
24042 reads the lines of the command definition, ending with @code{end}.
24043 After the @code{document} command is finished, @code{help} on command
24044 @var{commandname} displays the documentation you have written.
24046 You may use the @code{document} command again to change the
24047 documentation of a command. Redefining the command with @code{define}
24048 does not change the documentation.
24050 @kindex dont-repeat
24051 @cindex don't repeat command
24053 Used inside a user-defined command, this tells @value{GDBN} that this
24054 command should not be repeated when the user hits @key{RET}
24055 (@pxref{Command Syntax, repeat last command}).
24057 @kindex help user-defined
24058 @item help user-defined
24059 List all user-defined commands and all python commands defined in class
24060 COMAND_USER. The first line of the documentation or docstring is
24065 @itemx show user @var{commandname}
24066 Display the @value{GDBN} commands used to define @var{commandname} (but
24067 not its documentation). If no @var{commandname} is given, display the
24068 definitions for all user-defined commands.
24069 This does not work for user-defined python commands.
24071 @cindex infinite recursion in user-defined commands
24072 @kindex show max-user-call-depth
24073 @kindex set max-user-call-depth
24074 @item show max-user-call-depth
24075 @itemx set max-user-call-depth
24076 The value of @code{max-user-call-depth} controls how many recursion
24077 levels are allowed in user-defined commands before @value{GDBN} suspects an
24078 infinite recursion and aborts the command.
24079 This does not apply to user-defined python commands.
24082 In addition to the above commands, user-defined commands frequently
24083 use control flow commands, described in @ref{Command Files}.
24085 When user-defined commands are executed, the
24086 commands of the definition are not printed. An error in any command
24087 stops execution of the user-defined command.
24089 If used interactively, commands that would ask for confirmation proceed
24090 without asking when used inside a user-defined command. Many @value{GDBN}
24091 commands that normally print messages to say what they are doing omit the
24092 messages when used in a user-defined command.
24095 @subsection User-defined Command Hooks
24096 @cindex command hooks
24097 @cindex hooks, for commands
24098 @cindex hooks, pre-command
24101 You may define @dfn{hooks}, which are a special kind of user-defined
24102 command. Whenever you run the command @samp{foo}, if the user-defined
24103 command @samp{hook-foo} exists, it is executed (with no arguments)
24104 before that command.
24106 @cindex hooks, post-command
24108 A hook may also be defined which is run after the command you executed.
24109 Whenever you run the command @samp{foo}, if the user-defined command
24110 @samp{hookpost-foo} exists, it is executed (with no arguments) after
24111 that command. Post-execution hooks may exist simultaneously with
24112 pre-execution hooks, for the same command.
24114 It is valid for a hook to call the command which it hooks. If this
24115 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
24117 @c It would be nice if hookpost could be passed a parameter indicating
24118 @c if the command it hooks executed properly or not. FIXME!
24120 @kindex stop@r{, a pseudo-command}
24121 In addition, a pseudo-command, @samp{stop} exists. Defining
24122 (@samp{hook-stop}) makes the associated commands execute every time
24123 execution stops in your program: before breakpoint commands are run,
24124 displays are printed, or the stack frame is printed.
24126 For example, to ignore @code{SIGALRM} signals while
24127 single-stepping, but treat them normally during normal execution,
24132 handle SIGALRM nopass
24136 handle SIGALRM pass
24139 define hook-continue
24140 handle SIGALRM pass
24144 As a further example, to hook at the beginning and end of the @code{echo}
24145 command, and to add extra text to the beginning and end of the message,
24153 define hookpost-echo
24157 (@value{GDBP}) echo Hello World
24158 <<<---Hello World--->>>
24163 You can define a hook for any single-word command in @value{GDBN}, but
24164 not for command aliases; you should define a hook for the basic command
24165 name, e.g.@: @code{backtrace} rather than @code{bt}.
24166 @c FIXME! So how does Joe User discover whether a command is an alias
24168 You can hook a multi-word command by adding @code{hook-} or
24169 @code{hookpost-} to the last word of the command, e.g.@:
24170 @samp{define target hook-remote} to add a hook to @samp{target remote}.
24172 If an error occurs during the execution of your hook, execution of
24173 @value{GDBN} commands stops and @value{GDBN} issues a prompt
24174 (before the command that you actually typed had a chance to run).
24176 If you try to define a hook which does not match any known command, you
24177 get a warning from the @code{define} command.
24179 @node Command Files
24180 @subsection Command Files
24182 @cindex command files
24183 @cindex scripting commands
24184 A command file for @value{GDBN} is a text file made of lines that are
24185 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
24186 also be included. An empty line in a command file does nothing; it
24187 does not mean to repeat the last command, as it would from the
24190 You can request the execution of a command file with the @code{source}
24191 command. Note that the @code{source} command is also used to evaluate
24192 scripts that are not Command Files. The exact behavior can be configured
24193 using the @code{script-extension} setting.
24194 @xref{Extending GDB,, Extending GDB}.
24198 @cindex execute commands from a file
24199 @item source [-s] [-v] @var{filename}
24200 Execute the command file @var{filename}.
24203 The lines in a command file are generally executed sequentially,
24204 unless the order of execution is changed by one of the
24205 @emph{flow-control commands} described below. The commands are not
24206 printed as they are executed. An error in any command terminates
24207 execution of the command file and control is returned to the console.
24209 @value{GDBN} first searches for @var{filename} in the current directory.
24210 If the file is not found there, and @var{filename} does not specify a
24211 directory, then @value{GDBN} also looks for the file on the source search path
24212 (specified with the @samp{directory} command);
24213 except that @file{$cdir} is not searched because the compilation directory
24214 is not relevant to scripts.
24216 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
24217 on the search path even if @var{filename} specifies a directory.
24218 The search is done by appending @var{filename} to each element of the
24219 search path. So, for example, if @var{filename} is @file{mylib/myscript}
24220 and the search path contains @file{/home/user} then @value{GDBN} will
24221 look for the script @file{/home/user/mylib/myscript}.
24222 The search is also done if @var{filename} is an absolute path.
24223 For example, if @var{filename} is @file{/tmp/myscript} and
24224 the search path contains @file{/home/user} then @value{GDBN} will
24225 look for the script @file{/home/user/tmp/myscript}.
24226 For DOS-like systems, if @var{filename} contains a drive specification,
24227 it is stripped before concatenation. For example, if @var{filename} is
24228 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
24229 will look for the script @file{c:/tmp/myscript}.
24231 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
24232 each command as it is executed. The option must be given before
24233 @var{filename}, and is interpreted as part of the filename anywhere else.
24235 Commands that would ask for confirmation if used interactively proceed
24236 without asking when used in a command file. Many @value{GDBN} commands that
24237 normally print messages to say what they are doing omit the messages
24238 when called from command files.
24240 @value{GDBN} also accepts command input from standard input. In this
24241 mode, normal output goes to standard output and error output goes to
24242 standard error. Errors in a command file supplied on standard input do
24243 not terminate execution of the command file---execution continues with
24247 gdb < cmds > log 2>&1
24250 (The syntax above will vary depending on the shell used.) This example
24251 will execute commands from the file @file{cmds}. All output and errors
24252 would be directed to @file{log}.
24254 Since commands stored on command files tend to be more general than
24255 commands typed interactively, they frequently need to deal with
24256 complicated situations, such as different or unexpected values of
24257 variables and symbols, changes in how the program being debugged is
24258 built, etc. @value{GDBN} provides a set of flow-control commands to
24259 deal with these complexities. Using these commands, you can write
24260 complex scripts that loop over data structures, execute commands
24261 conditionally, etc.
24268 This command allows to include in your script conditionally executed
24269 commands. The @code{if} command takes a single argument, which is an
24270 expression to evaluate. It is followed by a series of commands that
24271 are executed only if the expression is true (its value is nonzero).
24272 There can then optionally be an @code{else} line, followed by a series
24273 of commands that are only executed if the expression was false. The
24274 end of the list is marked by a line containing @code{end}.
24278 This command allows to write loops. Its syntax is similar to
24279 @code{if}: the command takes a single argument, which is an expression
24280 to evaluate, and must be followed by the commands to execute, one per
24281 line, terminated by an @code{end}. These commands are called the
24282 @dfn{body} of the loop. The commands in the body of @code{while} are
24283 executed repeatedly as long as the expression evaluates to true.
24287 This command exits the @code{while} loop in whose body it is included.
24288 Execution of the script continues after that @code{while}s @code{end}
24291 @kindex loop_continue
24292 @item loop_continue
24293 This command skips the execution of the rest of the body of commands
24294 in the @code{while} loop in whose body it is included. Execution
24295 branches to the beginning of the @code{while} loop, where it evaluates
24296 the controlling expression.
24298 @kindex end@r{ (if/else/while commands)}
24300 Terminate the block of commands that are the body of @code{if},
24301 @code{else}, or @code{while} flow-control commands.
24306 @subsection Commands for Controlled Output
24308 During the execution of a command file or a user-defined command, normal
24309 @value{GDBN} output is suppressed; the only output that appears is what is
24310 explicitly printed by the commands in the definition. This section
24311 describes three commands useful for generating exactly the output you
24316 @item echo @var{text}
24317 @c I do not consider backslash-space a standard C escape sequence
24318 @c because it is not in ANSI.
24319 Print @var{text}. Nonprinting characters can be included in
24320 @var{text} using C escape sequences, such as @samp{\n} to print a
24321 newline. @strong{No newline is printed unless you specify one.}
24322 In addition to the standard C escape sequences, a backslash followed
24323 by a space stands for a space. This is useful for displaying a
24324 string with spaces at the beginning or the end, since leading and
24325 trailing spaces are otherwise trimmed from all arguments.
24326 To print @samp{@w{ }and foo =@w{ }}, use the command
24327 @samp{echo \@w{ }and foo = \@w{ }}.
24329 A backslash at the end of @var{text} can be used, as in C, to continue
24330 the command onto subsequent lines. For example,
24333 echo This is some text\n\
24334 which is continued\n\
24335 onto several lines.\n
24338 produces the same output as
24341 echo This is some text\n
24342 echo which is continued\n
24343 echo onto several lines.\n
24347 @item output @var{expression}
24348 Print the value of @var{expression} and nothing but that value: no
24349 newlines, no @samp{$@var{nn} = }. The value is not entered in the
24350 value history either. @xref{Expressions, ,Expressions}, for more information
24353 @item output/@var{fmt} @var{expression}
24354 Print the value of @var{expression} in format @var{fmt}. You can use
24355 the same formats as for @code{print}. @xref{Output Formats,,Output
24356 Formats}, for more information.
24359 @item printf @var{template}, @var{expressions}@dots{}
24360 Print the values of one or more @var{expressions} under the control of
24361 the string @var{template}. To print several values, make
24362 @var{expressions} be a comma-separated list of individual expressions,
24363 which may be either numbers or pointers. Their values are printed as
24364 specified by @var{template}, exactly as a C program would do by
24365 executing the code below:
24368 printf (@var{template}, @var{expressions}@dots{});
24371 As in @code{C} @code{printf}, ordinary characters in @var{template}
24372 are printed verbatim, while @dfn{conversion specification} introduced
24373 by the @samp{%} character cause subsequent @var{expressions} to be
24374 evaluated, their values converted and formatted according to type and
24375 style information encoded in the conversion specifications, and then
24378 For example, you can print two values in hex like this:
24381 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
24384 @code{printf} supports all the standard @code{C} conversion
24385 specifications, including the flags and modifiers between the @samp{%}
24386 character and the conversion letter, with the following exceptions:
24390 The argument-ordering modifiers, such as @samp{2$}, are not supported.
24393 The modifier @samp{*} is not supported for specifying precision or
24397 The @samp{'} flag (for separation of digits into groups according to
24398 @code{LC_NUMERIC'}) is not supported.
24401 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
24405 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
24408 The conversion letters @samp{a} and @samp{A} are not supported.
24412 Note that the @samp{ll} type modifier is supported only if the
24413 underlying @code{C} implementation used to build @value{GDBN} supports
24414 the @code{long long int} type, and the @samp{L} type modifier is
24415 supported only if @code{long double} type is available.
24417 As in @code{C}, @code{printf} supports simple backslash-escape
24418 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
24419 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
24420 single character. Octal and hexadecimal escape sequences are not
24423 Additionally, @code{printf} supports conversion specifications for DFP
24424 (@dfn{Decimal Floating Point}) types using the following length modifiers
24425 together with a floating point specifier.
24430 @samp{H} for printing @code{Decimal32} types.
24433 @samp{D} for printing @code{Decimal64} types.
24436 @samp{DD} for printing @code{Decimal128} types.
24439 If the underlying @code{C} implementation used to build @value{GDBN} has
24440 support for the three length modifiers for DFP types, other modifiers
24441 such as width and precision will also be available for @value{GDBN} to use.
24443 In case there is no such @code{C} support, no additional modifiers will be
24444 available and the value will be printed in the standard way.
24446 Here's an example of printing DFP types using the above conversion letters:
24448 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
24452 @item eval @var{template}, @var{expressions}@dots{}
24453 Convert the values of one or more @var{expressions} under the control of
24454 the string @var{template} to a command line, and call it.
24458 @node Auto-loading sequences
24459 @subsection Controlling auto-loading native @value{GDBN} scripts
24460 @cindex native script auto-loading
24462 When a new object file is read (for example, due to the @code{file}
24463 command, or because the inferior has loaded a shared library),
24464 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
24465 @xref{Auto-loading extensions}.
24467 Auto-loading can be enabled or disabled,
24468 and the list of auto-loaded scripts can be printed.
24471 @anchor{set auto-load gdb-scripts}
24472 @kindex set auto-load gdb-scripts
24473 @item set auto-load gdb-scripts [on|off]
24474 Enable or disable the auto-loading of canned sequences of commands scripts.
24476 @anchor{show auto-load gdb-scripts}
24477 @kindex show auto-load gdb-scripts
24478 @item show auto-load gdb-scripts
24479 Show whether auto-loading of canned sequences of commands scripts is enabled or
24482 @anchor{info auto-load gdb-scripts}
24483 @kindex info auto-load gdb-scripts
24484 @cindex print list of auto-loaded canned sequences of commands scripts
24485 @item info auto-load gdb-scripts [@var{regexp}]
24486 Print the list of all canned sequences of commands scripts that @value{GDBN}
24490 If @var{regexp} is supplied only canned sequences of commands scripts with
24491 matching names are printed.
24493 @c Python docs live in a separate file.
24494 @include python.texi
24496 @c Guile docs live in a separate file.
24497 @include guile.texi
24499 @node Auto-loading extensions
24500 @section Auto-loading extensions
24501 @cindex auto-loading extensions
24503 @value{GDBN} provides two mechanisms for automatically loading extensions
24504 when a new object file is read (for example, due to the @code{file}
24505 command, or because the inferior has loaded a shared library):
24506 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
24507 section of modern file formats like ELF.
24510 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
24511 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
24512 * Which flavor to choose?::
24515 The auto-loading feature is useful for supplying application-specific
24516 debugging commands and features.
24518 Auto-loading can be enabled or disabled,
24519 and the list of auto-loaded scripts can be printed.
24520 See the @samp{auto-loading} section of each extension language
24521 for more information.
24522 For @value{GDBN} command files see @ref{Auto-loading sequences}.
24523 For Python files see @ref{Python Auto-loading}.
24525 Note that loading of this script file also requires accordingly configured
24526 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24528 @node objfile-gdbdotext file
24529 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
24530 @cindex @file{@var{objfile}-gdb.gdb}
24531 @cindex @file{@var{objfile}-gdb.py}
24532 @cindex @file{@var{objfile}-gdb.scm}
24534 When a new object file is read, @value{GDBN} looks for a file named
24535 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
24536 where @var{objfile} is the object file's name and
24537 where @var{ext} is the file extension for the extension language:
24540 @item @file{@var{objfile}-gdb.gdb}
24541 GDB's own command language
24542 @item @file{@var{objfile}-gdb.py}
24544 @item @file{@var{objfile}-gdb.scm}
24548 @var{script-name} is formed by ensuring that the file name of @var{objfile}
24549 is absolute, following all symlinks, and resolving @code{.} and @code{..}
24550 components, and appending the @file{-gdb.@var{ext}} suffix.
24551 If this file exists and is readable, @value{GDBN} will evaluate it as a
24552 script in the specified extension language.
24554 If this file does not exist, then @value{GDBN} will look for
24555 @var{script-name} file in all of the directories as specified below.
24557 Note that loading of these files requires an accordingly configured
24558 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24560 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
24561 scripts normally according to its @file{.exe} filename. But if no scripts are
24562 found @value{GDBN} also tries script filenames matching the object file without
24563 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
24564 is attempted on any platform. This makes the script filenames compatible
24565 between Unix and MS-Windows hosts.
24568 @anchor{set auto-load scripts-directory}
24569 @kindex set auto-load scripts-directory
24570 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
24571 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
24572 may be delimited by the host platform path separator in use
24573 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
24575 Each entry here needs to be covered also by the security setting
24576 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
24578 @anchor{with-auto-load-dir}
24579 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
24580 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
24581 configuration option @option{--with-auto-load-dir}.
24583 Any reference to @file{$debugdir} will get replaced by
24584 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
24585 reference to @file{$datadir} will get replaced by @var{data-directory} which is
24586 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
24587 @file{$datadir} must be placed as a directory component --- either alone or
24588 delimited by @file{/} or @file{\} directory separators, depending on the host
24591 The list of directories uses path separator (@samp{:} on GNU and Unix
24592 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
24593 to the @env{PATH} environment variable.
24595 @anchor{show auto-load scripts-directory}
24596 @kindex show auto-load scripts-directory
24597 @item show auto-load scripts-directory
24598 Show @value{GDBN} auto-loaded scripts location.
24600 @anchor{add-auto-load-scripts-directory}
24601 @kindex add-auto-load-scripts-directory
24602 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
24603 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
24604 Multiple entries may be delimited by the host platform path separator in use.
24607 @value{GDBN} does not track which files it has already auto-loaded this way.
24608 @value{GDBN} will load the associated script every time the corresponding
24609 @var{objfile} is opened.
24610 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
24611 is evaluated more than once.
24613 @node dotdebug_gdb_scripts section
24614 @subsection The @code{.debug_gdb_scripts} section
24615 @cindex @code{.debug_gdb_scripts} section
24617 For systems using file formats like ELF and COFF,
24618 when @value{GDBN} loads a new object file
24619 it will look for a special section named @code{.debug_gdb_scripts}.
24620 If this section exists, its contents is a list of null-terminated entries
24621 specifying scripts to load. Each entry begins with a non-null prefix byte that
24622 specifies the kind of entry, typically the extension language and whether the
24623 script is in a file or inlined in @code{.debug_gdb_scripts}.
24625 The following entries are supported:
24628 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
24629 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
24630 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
24631 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
24634 @subsubsection Script File Entries
24636 If the entry specifies a file, @value{GDBN} will look for the file first
24637 in the current directory and then along the source search path
24638 (@pxref{Source Path, ,Specifying Source Directories}),
24639 except that @file{$cdir} is not searched, since the compilation
24640 directory is not relevant to scripts.
24642 File entries can be placed in section @code{.debug_gdb_scripts} with,
24643 for example, this GCC macro for Python scripts.
24646 /* Note: The "MS" section flags are to remove duplicates. */
24647 #define DEFINE_GDB_PY_SCRIPT(script_name) \
24649 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
24650 .byte 1 /* Python */\n\
24651 .asciz \"" script_name "\"\n\
24657 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
24658 Then one can reference the macro in a header or source file like this:
24661 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
24664 The script name may include directories if desired.
24666 Note that loading of this script file also requires accordingly configured
24667 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24669 If the macro invocation is put in a header, any application or library
24670 using this header will get a reference to the specified script,
24671 and with the use of @code{"MS"} attributes on the section, the linker
24672 will remove duplicates.
24674 @subsubsection Script Text Entries
24676 Script text entries allow to put the executable script in the entry
24677 itself instead of loading it from a file.
24678 The first line of the entry, everything after the prefix byte and up to
24679 the first newline (@code{0xa}) character, is the script name, and must not
24680 contain any kind of space character, e.g., spaces or tabs.
24681 The rest of the entry, up to the trailing null byte, is the script to
24682 execute in the specified language. The name needs to be unique among
24683 all script names, as @value{GDBN} executes each script only once based
24686 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
24690 #include "symcat.h"
24691 #include "gdb/section-scripts.h"
24693 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
24694 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
24695 ".ascii \"gdb.inlined-script\\n\"\n"
24696 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
24697 ".ascii \" def __init__ (self):\\n\"\n"
24698 ".ascii \" super (test_cmd, self).__init__ ("
24699 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
24700 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
24701 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
24702 ".ascii \"test_cmd ()\\n\"\n"
24708 Loading of inlined scripts requires a properly configured
24709 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24710 The path to specify in @code{auto-load safe-path} is the path of the file
24711 containing the @code{.debug_gdb_scripts} section.
24713 @node Which flavor to choose?
24714 @subsection Which flavor to choose?
24716 Given the multiple ways of auto-loading extensions, it might not always
24717 be clear which one to choose. This section provides some guidance.
24720 Benefits of the @file{-gdb.@var{ext}} way:
24724 Can be used with file formats that don't support multiple sections.
24727 Ease of finding scripts for public libraries.
24729 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
24730 in the source search path.
24731 For publicly installed libraries, e.g., @file{libstdc++}, there typically
24732 isn't a source directory in which to find the script.
24735 Doesn't require source code additions.
24739 Benefits of the @code{.debug_gdb_scripts} way:
24743 Works with static linking.
24745 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
24746 trigger their loading. When an application is statically linked the only
24747 objfile available is the executable, and it is cumbersome to attach all the
24748 scripts from all the input libraries to the executable's
24749 @file{-gdb.@var{ext}} script.
24752 Works with classes that are entirely inlined.
24754 Some classes can be entirely inlined, and thus there may not be an associated
24755 shared library to attach a @file{-gdb.@var{ext}} script to.
24758 Scripts needn't be copied out of the source tree.
24760 In some circumstances, apps can be built out of large collections of internal
24761 libraries, and the build infrastructure necessary to install the
24762 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
24763 cumbersome. It may be easier to specify the scripts in the
24764 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
24765 top of the source tree to the source search path.
24768 @node Multiple Extension Languages
24769 @section Multiple Extension Languages
24771 The Guile and Python extension languages do not share any state,
24772 and generally do not interfere with each other.
24773 There are some things to be aware of, however.
24775 @subsection Python comes first
24777 Python was @value{GDBN}'s first extension language, and to avoid breaking
24778 existing behaviour Python comes first. This is generally solved by the
24779 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
24780 extension languages, and when it makes a call to an extension language,
24781 (say to pretty-print a value), it tries each in turn until an extension
24782 language indicates it has performed the request (e.g., has returned the
24783 pretty-printed form of a value).
24784 This extends to errors while performing such requests: If an error happens
24785 while, for example, trying to pretty-print an object then the error is
24786 reported and any following extension languages are not tried.
24789 @section Creating new spellings of existing commands
24790 @cindex aliases for commands
24792 It is often useful to define alternate spellings of existing commands.
24793 For example, if a new @value{GDBN} command defined in Python has
24794 a long name to type, it is handy to have an abbreviated version of it
24795 that involves less typing.
24797 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
24798 of the @samp{step} command even though it is otherwise an ambiguous
24799 abbreviation of other commands like @samp{set} and @samp{show}.
24801 Aliases are also used to provide shortened or more common versions
24802 of multi-word commands. For example, @value{GDBN} provides the
24803 @samp{tty} alias of the @samp{set inferior-tty} command.
24805 You can define a new alias with the @samp{alias} command.
24810 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
24814 @var{ALIAS} specifies the name of the new alias.
24815 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
24818 @var{COMMAND} specifies the name of an existing command
24819 that is being aliased.
24821 The @samp{-a} option specifies that the new alias is an abbreviation
24822 of the command. Abbreviations are not shown in command
24823 lists displayed by the @samp{help} command.
24825 The @samp{--} option specifies the end of options,
24826 and is useful when @var{ALIAS} begins with a dash.
24828 Here is a simple example showing how to make an abbreviation
24829 of a command so that there is less to type.
24830 Suppose you were tired of typing @samp{disas}, the current
24831 shortest unambiguous abbreviation of the @samp{disassemble} command
24832 and you wanted an even shorter version named @samp{di}.
24833 The following will accomplish this.
24836 (gdb) alias -a di = disas
24839 Note that aliases are different from user-defined commands.
24840 With a user-defined command, you also need to write documentation
24841 for it with the @samp{document} command.
24842 An alias automatically picks up the documentation of the existing command.
24844 Here is an example where we make @samp{elms} an abbreviation of
24845 @samp{elements} in the @samp{set print elements} command.
24846 This is to show that you can make an abbreviation of any part
24850 (gdb) alias -a set print elms = set print elements
24851 (gdb) alias -a show print elms = show print elements
24852 (gdb) set p elms 20
24854 Limit on string chars or array elements to print is 200.
24857 Note that if you are defining an alias of a @samp{set} command,
24858 and you want to have an alias for the corresponding @samp{show}
24859 command, then you need to define the latter separately.
24861 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
24862 @var{ALIAS}, just as they are normally.
24865 (gdb) alias -a set pr elms = set p ele
24868 Finally, here is an example showing the creation of a one word
24869 alias for a more complex command.
24870 This creates alias @samp{spe} of the command @samp{set print elements}.
24873 (gdb) alias spe = set print elements
24878 @chapter Command Interpreters
24879 @cindex command interpreters
24881 @value{GDBN} supports multiple command interpreters, and some command
24882 infrastructure to allow users or user interface writers to switch
24883 between interpreters or run commands in other interpreters.
24885 @value{GDBN} currently supports two command interpreters, the console
24886 interpreter (sometimes called the command-line interpreter or @sc{cli})
24887 and the machine interface interpreter (or @sc{gdb/mi}). This manual
24888 describes both of these interfaces in great detail.
24890 By default, @value{GDBN} will start with the console interpreter.
24891 However, the user may choose to start @value{GDBN} with another
24892 interpreter by specifying the @option{-i} or @option{--interpreter}
24893 startup options. Defined interpreters include:
24897 @cindex console interpreter
24898 The traditional console or command-line interpreter. This is the most often
24899 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
24900 @value{GDBN} will use this interpreter.
24903 @cindex mi interpreter
24904 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
24905 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
24906 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
24910 @cindex mi2 interpreter
24911 The current @sc{gdb/mi} interface.
24914 @cindex mi1 interpreter
24915 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
24919 @cindex invoke another interpreter
24920 The interpreter being used by @value{GDBN} may not be dynamically
24921 switched at runtime. Although possible, this could lead to a very
24922 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
24923 enters the command "interpreter-set console" in a console view,
24924 @value{GDBN} would switch to using the console interpreter, rendering
24925 the IDE inoperable!
24927 @kindex interpreter-exec
24928 Although you may only choose a single interpreter at startup, you may execute
24929 commands in any interpreter from the current interpreter using the appropriate
24930 command. If you are running the console interpreter, simply use the
24931 @code{interpreter-exec} command:
24934 interpreter-exec mi "-data-list-register-names"
24937 @sc{gdb/mi} has a similar command, although it is only available in versions of
24938 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
24941 @chapter @value{GDBN} Text User Interface
24943 @cindex Text User Interface
24946 * TUI Overview:: TUI overview
24947 * TUI Keys:: TUI key bindings
24948 * TUI Single Key Mode:: TUI single key mode
24949 * TUI Commands:: TUI-specific commands
24950 * TUI Configuration:: TUI configuration variables
24953 The @value{GDBN} Text User Interface (TUI) is a terminal
24954 interface which uses the @code{curses} library to show the source
24955 file, the assembly output, the program registers and @value{GDBN}
24956 commands in separate text windows. The TUI mode is supported only
24957 on platforms where a suitable version of the @code{curses} library
24960 The TUI mode is enabled by default when you invoke @value{GDBN} as
24961 @samp{@value{GDBP} -tui}.
24962 You can also switch in and out of TUI mode while @value{GDBN} runs by
24963 using various TUI commands and key bindings, such as @command{tui
24964 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
24965 @ref{TUI Keys, ,TUI Key Bindings}.
24968 @section TUI Overview
24970 In TUI mode, @value{GDBN} can display several text windows:
24974 This window is the @value{GDBN} command window with the @value{GDBN}
24975 prompt and the @value{GDBN} output. The @value{GDBN} input is still
24976 managed using readline.
24979 The source window shows the source file of the program. The current
24980 line and active breakpoints are displayed in this window.
24983 The assembly window shows the disassembly output of the program.
24986 This window shows the processor registers. Registers are highlighted
24987 when their values change.
24990 The source and assembly windows show the current program position
24991 by highlighting the current line and marking it with a @samp{>} marker.
24992 Breakpoints are indicated with two markers. The first marker
24993 indicates the breakpoint type:
24997 Breakpoint which was hit at least once.
25000 Breakpoint which was never hit.
25003 Hardware breakpoint which was hit at least once.
25006 Hardware breakpoint which was never hit.
25009 The second marker indicates whether the breakpoint is enabled or not:
25013 Breakpoint is enabled.
25016 Breakpoint is disabled.
25019 The source, assembly and register windows are updated when the current
25020 thread changes, when the frame changes, or when the program counter
25023 These windows are not all visible at the same time. The command
25024 window is always visible. The others can be arranged in several
25035 source and assembly,
25038 source and registers, or
25041 assembly and registers.
25044 A status line above the command window shows the following information:
25048 Indicates the current @value{GDBN} target.
25049 (@pxref{Targets, ,Specifying a Debugging Target}).
25052 Gives the current process or thread number.
25053 When no process is being debugged, this field is set to @code{No process}.
25056 Gives the current function name for the selected frame.
25057 The name is demangled if demangling is turned on (@pxref{Print Settings}).
25058 When there is no symbol corresponding to the current program counter,
25059 the string @code{??} is displayed.
25062 Indicates the current line number for the selected frame.
25063 When the current line number is not known, the string @code{??} is displayed.
25066 Indicates the current program counter address.
25070 @section TUI Key Bindings
25071 @cindex TUI key bindings
25073 The TUI installs several key bindings in the readline keymaps
25074 @ifset SYSTEM_READLINE
25075 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
25077 @ifclear SYSTEM_READLINE
25078 (@pxref{Command Line Editing}).
25080 The following key bindings are installed for both TUI mode and the
25081 @value{GDBN} standard mode.
25090 Enter or leave the TUI mode. When leaving the TUI mode,
25091 the curses window management stops and @value{GDBN} operates using
25092 its standard mode, writing on the terminal directly. When reentering
25093 the TUI mode, control is given back to the curses windows.
25094 The screen is then refreshed.
25098 Use a TUI layout with only one window. The layout will
25099 either be @samp{source} or @samp{assembly}. When the TUI mode
25100 is not active, it will switch to the TUI mode.
25102 Think of this key binding as the Emacs @kbd{C-x 1} binding.
25106 Use a TUI layout with at least two windows. When the current
25107 layout already has two windows, the next layout with two windows is used.
25108 When a new layout is chosen, one window will always be common to the
25109 previous layout and the new one.
25111 Think of it as the Emacs @kbd{C-x 2} binding.
25115 Change the active window. The TUI associates several key bindings
25116 (like scrolling and arrow keys) with the active window. This command
25117 gives the focus to the next TUI window.
25119 Think of it as the Emacs @kbd{C-x o} binding.
25123 Switch in and out of the TUI SingleKey mode that binds single
25124 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
25127 The following key bindings only work in the TUI mode:
25132 Scroll the active window one page up.
25136 Scroll the active window one page down.
25140 Scroll the active window one line up.
25144 Scroll the active window one line down.
25148 Scroll the active window one column left.
25152 Scroll the active window one column right.
25156 Refresh the screen.
25159 Because the arrow keys scroll the active window in the TUI mode, they
25160 are not available for their normal use by readline unless the command
25161 window has the focus. When another window is active, you must use
25162 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
25163 and @kbd{C-f} to control the command window.
25165 @node TUI Single Key Mode
25166 @section TUI Single Key Mode
25167 @cindex TUI single key mode
25169 The TUI also provides a @dfn{SingleKey} mode, which binds several
25170 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
25171 switch into this mode, where the following key bindings are used:
25174 @kindex c @r{(SingleKey TUI key)}
25178 @kindex d @r{(SingleKey TUI key)}
25182 @kindex f @r{(SingleKey TUI key)}
25186 @kindex n @r{(SingleKey TUI key)}
25190 @kindex q @r{(SingleKey TUI key)}
25192 exit the SingleKey mode.
25194 @kindex r @r{(SingleKey TUI key)}
25198 @kindex s @r{(SingleKey TUI key)}
25202 @kindex u @r{(SingleKey TUI key)}
25206 @kindex v @r{(SingleKey TUI key)}
25210 @kindex w @r{(SingleKey TUI key)}
25215 Other keys temporarily switch to the @value{GDBN} command prompt.
25216 The key that was pressed is inserted in the editing buffer so that
25217 it is possible to type most @value{GDBN} commands without interaction
25218 with the TUI SingleKey mode. Once the command is entered the TUI
25219 SingleKey mode is restored. The only way to permanently leave
25220 this mode is by typing @kbd{q} or @kbd{C-x s}.
25224 @section TUI-specific Commands
25225 @cindex TUI commands
25227 The TUI has specific commands to control the text windows.
25228 These commands are always available, even when @value{GDBN} is not in
25229 the TUI mode. When @value{GDBN} is in the standard mode, most
25230 of these commands will automatically switch to the TUI mode.
25232 Note that if @value{GDBN}'s @code{stdout} is not connected to a
25233 terminal, or @value{GDBN} has been started with the machine interface
25234 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
25235 these commands will fail with an error, because it would not be
25236 possible or desirable to enable curses window management.
25241 Activate TUI mode. The last active TUI window layout will be used if
25242 TUI mode has prevsiouly been used in the current debugging session,
25243 otherwise a default layout is used.
25246 @kindex tui disable
25247 Disable TUI mode, returning to the console interpreter.
25251 List and give the size of all displayed windows.
25253 @item layout @var{name}
25255 Changes which TUI windows are displayed. In each layout the command
25256 window is always displayed, the @var{name} parameter controls which
25257 additional windows are displayed, and can be any of the following:
25261 Display the next layout.
25264 Display the previous layout.
25267 Display the source and command windows.
25270 Display the assembly and command windows.
25273 Display the source, assembly, and command windows.
25276 When in @code{src} layout display the register, source, and command
25277 windows. When in @code{asm} or @code{split} layout display the
25278 register, assembler, and command windows.
25281 @item focus @var{name}
25283 Changes which TUI window is currently active for scrolling. The
25284 @var{name} parameter can be any of the following:
25288 Make the next window active for scrolling.
25291 Make the previous window active for scrolling.
25294 Make the source window active for scrolling.
25297 Make the assembly window active for scrolling.
25300 Make the register window active for scrolling.
25303 Make the command window active for scrolling.
25308 Refresh the screen. This is similar to typing @kbd{C-L}.
25310 @item tui reg @var{group}
25312 Changes the register group displayed in the tui register window to
25313 @var{group}. If the register window is not currently displayed this
25314 command will cause the register window to be displayed. The list of
25315 register groups, as well as their order is target specific. The
25316 following groups are available on most targets:
25319 Repeatedly selecting this group will cause the display to cycle
25320 through all of the available register groups.
25323 Repeatedly selecting this group will cause the display to cycle
25324 through all of the available register groups in the reverse order to
25328 Display the general registers.
25330 Display the floating point registers.
25332 Display the system registers.
25334 Display the vector registers.
25336 Display all registers.
25341 Update the source window and the current execution point.
25343 @item winheight @var{name} +@var{count}
25344 @itemx winheight @var{name} -@var{count}
25346 Change the height of the window @var{name} by @var{count}
25347 lines. Positive counts increase the height, while negative counts
25348 decrease it. The @var{name} parameter can be one of @code{src} (the
25349 source window), @code{cmd} (the command window), @code{asm} (the
25350 disassembly window), or @code{regs} (the register display window).
25352 @item tabset @var{nchars}
25354 Set the width of tab stops to be @var{nchars} characters. This
25355 setting affects the display of TAB characters in the source and
25359 @node TUI Configuration
25360 @section TUI Configuration Variables
25361 @cindex TUI configuration variables
25363 Several configuration variables control the appearance of TUI windows.
25366 @item set tui border-kind @var{kind}
25367 @kindex set tui border-kind
25368 Select the border appearance for the source, assembly and register windows.
25369 The possible values are the following:
25372 Use a space character to draw the border.
25375 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
25378 Use the Alternate Character Set to draw the border. The border is
25379 drawn using character line graphics if the terminal supports them.
25382 @item set tui border-mode @var{mode}
25383 @kindex set tui border-mode
25384 @itemx set tui active-border-mode @var{mode}
25385 @kindex set tui active-border-mode
25386 Select the display attributes for the borders of the inactive windows
25387 or the active window. The @var{mode} can be one of the following:
25390 Use normal attributes to display the border.
25396 Use reverse video mode.
25399 Use half bright mode.
25401 @item half-standout
25402 Use half bright and standout mode.
25405 Use extra bright or bold mode.
25407 @item bold-standout
25408 Use extra bright or bold and standout mode.
25413 @chapter Using @value{GDBN} under @sc{gnu} Emacs
25416 @cindex @sc{gnu} Emacs
25417 A special interface allows you to use @sc{gnu} Emacs to view (and
25418 edit) the source files for the program you are debugging with
25421 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
25422 executable file you want to debug as an argument. This command starts
25423 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
25424 created Emacs buffer.
25425 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
25427 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
25432 All ``terminal'' input and output goes through an Emacs buffer, called
25435 This applies both to @value{GDBN} commands and their output, and to the input
25436 and output done by the program you are debugging.
25438 This is useful because it means that you can copy the text of previous
25439 commands and input them again; you can even use parts of the output
25442 All the facilities of Emacs' Shell mode are available for interacting
25443 with your program. In particular, you can send signals the usual
25444 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
25448 @value{GDBN} displays source code through Emacs.
25450 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
25451 source file for that frame and puts an arrow (@samp{=>}) at the
25452 left margin of the current line. Emacs uses a separate buffer for
25453 source display, and splits the screen to show both your @value{GDBN} session
25456 Explicit @value{GDBN} @code{list} or search commands still produce output as
25457 usual, but you probably have no reason to use them from Emacs.
25460 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
25461 a graphical mode, enabled by default, which provides further buffers
25462 that can control the execution and describe the state of your program.
25463 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
25465 If you specify an absolute file name when prompted for the @kbd{M-x
25466 gdb} argument, then Emacs sets your current working directory to where
25467 your program resides. If you only specify the file name, then Emacs
25468 sets your current working directory to the directory associated
25469 with the previous buffer. In this case, @value{GDBN} may find your
25470 program by searching your environment's @code{PATH} variable, but on
25471 some operating systems it might not find the source. So, although the
25472 @value{GDBN} input and output session proceeds normally, the auxiliary
25473 buffer does not display the current source and line of execution.
25475 The initial working directory of @value{GDBN} is printed on the top
25476 line of the GUD buffer and this serves as a default for the commands
25477 that specify files for @value{GDBN} to operate on. @xref{Files,
25478 ,Commands to Specify Files}.
25480 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
25481 need to call @value{GDBN} by a different name (for example, if you
25482 keep several configurations around, with different names) you can
25483 customize the Emacs variable @code{gud-gdb-command-name} to run the
25486 In the GUD buffer, you can use these special Emacs commands in
25487 addition to the standard Shell mode commands:
25491 Describe the features of Emacs' GUD Mode.
25494 Execute to another source line, like the @value{GDBN} @code{step} command; also
25495 update the display window to show the current file and location.
25498 Execute to next source line in this function, skipping all function
25499 calls, like the @value{GDBN} @code{next} command. Then update the display window
25500 to show the current file and location.
25503 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
25504 display window accordingly.
25507 Execute until exit from the selected stack frame, like the @value{GDBN}
25508 @code{finish} command.
25511 Continue execution of your program, like the @value{GDBN} @code{continue}
25515 Go up the number of frames indicated by the numeric argument
25516 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
25517 like the @value{GDBN} @code{up} command.
25520 Go down the number of frames indicated by the numeric argument, like the
25521 @value{GDBN} @code{down} command.
25524 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
25525 tells @value{GDBN} to set a breakpoint on the source line point is on.
25527 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
25528 separate frame which shows a backtrace when the GUD buffer is current.
25529 Move point to any frame in the stack and type @key{RET} to make it
25530 become the current frame and display the associated source in the
25531 source buffer. Alternatively, click @kbd{Mouse-2} to make the
25532 selected frame become the current one. In graphical mode, the
25533 speedbar displays watch expressions.
25535 If you accidentally delete the source-display buffer, an easy way to get
25536 it back is to type the command @code{f} in the @value{GDBN} buffer, to
25537 request a frame display; when you run under Emacs, this recreates
25538 the source buffer if necessary to show you the context of the current
25541 The source files displayed in Emacs are in ordinary Emacs buffers
25542 which are visiting the source files in the usual way. You can edit
25543 the files with these buffers if you wish; but keep in mind that @value{GDBN}
25544 communicates with Emacs in terms of line numbers. If you add or
25545 delete lines from the text, the line numbers that @value{GDBN} knows cease
25546 to correspond properly with the code.
25548 A more detailed description of Emacs' interaction with @value{GDBN} is
25549 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
25553 @chapter The @sc{gdb/mi} Interface
25555 @unnumberedsec Function and Purpose
25557 @cindex @sc{gdb/mi}, its purpose
25558 @sc{gdb/mi} is a line based machine oriented text interface to
25559 @value{GDBN} and is activated by specifying using the
25560 @option{--interpreter} command line option (@pxref{Mode Options}). It
25561 is specifically intended to support the development of systems which
25562 use the debugger as just one small component of a larger system.
25564 This chapter is a specification of the @sc{gdb/mi} interface. It is written
25565 in the form of a reference manual.
25567 Note that @sc{gdb/mi} is still under construction, so some of the
25568 features described below are incomplete and subject to change
25569 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
25571 @unnumberedsec Notation and Terminology
25573 @cindex notational conventions, for @sc{gdb/mi}
25574 This chapter uses the following notation:
25578 @code{|} separates two alternatives.
25581 @code{[ @var{something} ]} indicates that @var{something} is optional:
25582 it may or may not be given.
25585 @code{( @var{group} )*} means that @var{group} inside the parentheses
25586 may repeat zero or more times.
25589 @code{( @var{group} )+} means that @var{group} inside the parentheses
25590 may repeat one or more times.
25593 @code{"@var{string}"} means a literal @var{string}.
25597 @heading Dependencies
25601 * GDB/MI General Design::
25602 * GDB/MI Command Syntax::
25603 * GDB/MI Compatibility with CLI::
25604 * GDB/MI Development and Front Ends::
25605 * GDB/MI Output Records::
25606 * GDB/MI Simple Examples::
25607 * GDB/MI Command Description Format::
25608 * GDB/MI Breakpoint Commands::
25609 * GDB/MI Catchpoint Commands::
25610 * GDB/MI Program Context::
25611 * GDB/MI Thread Commands::
25612 * GDB/MI Ada Tasking Commands::
25613 * GDB/MI Program Execution::
25614 * GDB/MI Stack Manipulation::
25615 * GDB/MI Variable Objects::
25616 * GDB/MI Data Manipulation::
25617 * GDB/MI Tracepoint Commands::
25618 * GDB/MI Symbol Query::
25619 * GDB/MI File Commands::
25621 * GDB/MI Kod Commands::
25622 * GDB/MI Memory Overlay Commands::
25623 * GDB/MI Signal Handling Commands::
25625 * GDB/MI Target Manipulation::
25626 * GDB/MI File Transfer Commands::
25627 * GDB/MI Ada Exceptions Commands::
25628 * GDB/MI Support Commands::
25629 * GDB/MI Miscellaneous Commands::
25632 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25633 @node GDB/MI General Design
25634 @section @sc{gdb/mi} General Design
25635 @cindex GDB/MI General Design
25637 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
25638 parts---commands sent to @value{GDBN}, responses to those commands
25639 and notifications. Each command results in exactly one response,
25640 indicating either successful completion of the command, or an error.
25641 For the commands that do not resume the target, the response contains the
25642 requested information. For the commands that resume the target, the
25643 response only indicates whether the target was successfully resumed.
25644 Notifications is the mechanism for reporting changes in the state of the
25645 target, or in @value{GDBN} state, that cannot conveniently be associated with
25646 a command and reported as part of that command response.
25648 The important examples of notifications are:
25652 Exec notifications. These are used to report changes in
25653 target state---when a target is resumed, or stopped. It would not
25654 be feasible to include this information in response of resuming
25655 commands, because one resume commands can result in multiple events in
25656 different threads. Also, quite some time may pass before any event
25657 happens in the target, while a frontend needs to know whether the resuming
25658 command itself was successfully executed.
25661 Console output, and status notifications. Console output
25662 notifications are used to report output of CLI commands, as well as
25663 diagnostics for other commands. Status notifications are used to
25664 report the progress of a long-running operation. Naturally, including
25665 this information in command response would mean no output is produced
25666 until the command is finished, which is undesirable.
25669 General notifications. Commands may have various side effects on
25670 the @value{GDBN} or target state beyond their official purpose. For example,
25671 a command may change the selected thread. Although such changes can
25672 be included in command response, using notification allows for more
25673 orthogonal frontend design.
25677 There's no guarantee that whenever an MI command reports an error,
25678 @value{GDBN} or the target are in any specific state, and especially,
25679 the state is not reverted to the state before the MI command was
25680 processed. Therefore, whenever an MI command results in an error,
25681 we recommend that the frontend refreshes all the information shown in
25682 the user interface.
25686 * Context management::
25687 * Asynchronous and non-stop modes::
25691 @node Context management
25692 @subsection Context management
25694 @subsubsection Threads and Frames
25696 In most cases when @value{GDBN} accesses the target, this access is
25697 done in context of a specific thread and frame (@pxref{Frames}).
25698 Often, even when accessing global data, the target requires that a thread
25699 be specified. The CLI interface maintains the selected thread and frame,
25700 and supplies them to target on each command. This is convenient,
25701 because a command line user would not want to specify that information
25702 explicitly on each command, and because user interacts with
25703 @value{GDBN} via a single terminal, so no confusion is possible as
25704 to what thread and frame are the current ones.
25706 In the case of MI, the concept of selected thread and frame is less
25707 useful. First, a frontend can easily remember this information
25708 itself. Second, a graphical frontend can have more than one window,
25709 each one used for debugging a different thread, and the frontend might
25710 want to access additional threads for internal purposes. This
25711 increases the risk that by relying on implicitly selected thread, the
25712 frontend may be operating on a wrong one. Therefore, each MI command
25713 should explicitly specify which thread and frame to operate on. To
25714 make it possible, each MI command accepts the @samp{--thread} and
25715 @samp{--frame} options, the value to each is @value{GDBN} identifier
25716 for thread and frame to operate on.
25718 Usually, each top-level window in a frontend allows the user to select
25719 a thread and a frame, and remembers the user selection for further
25720 operations. However, in some cases @value{GDBN} may suggest that the
25721 current thread be changed. For example, when stopping on a breakpoint
25722 it is reasonable to switch to the thread where breakpoint is hit. For
25723 another example, if the user issues the CLI @samp{thread} command via
25724 the frontend, it is desirable to change the frontend's selected thread to the
25725 one specified by user. @value{GDBN} communicates the suggestion to
25726 change current thread using the @samp{=thread-selected} notification.
25727 No such notification is available for the selected frame at the moment.
25729 Note that historically, MI shares the selected thread with CLI, so
25730 frontends used the @code{-thread-select} to execute commands in the
25731 right context. However, getting this to work right is cumbersome. The
25732 simplest way is for frontend to emit @code{-thread-select} command
25733 before every command. This doubles the number of commands that need
25734 to be sent. The alternative approach is to suppress @code{-thread-select}
25735 if the selected thread in @value{GDBN} is supposed to be identical to the
25736 thread the frontend wants to operate on. However, getting this
25737 optimization right can be tricky. In particular, if the frontend
25738 sends several commands to @value{GDBN}, and one of the commands changes the
25739 selected thread, then the behaviour of subsequent commands will
25740 change. So, a frontend should either wait for response from such
25741 problematic commands, or explicitly add @code{-thread-select} for
25742 all subsequent commands. No frontend is known to do this exactly
25743 right, so it is suggested to just always pass the @samp{--thread} and
25744 @samp{--frame} options.
25746 @subsubsection Language
25748 The execution of several commands depends on which language is selected.
25749 By default, the current language (@pxref{show language}) is used.
25750 But for commands known to be language-sensitive, it is recommended
25751 to use the @samp{--language} option. This option takes one argument,
25752 which is the name of the language to use while executing the command.
25756 -data-evaluate-expression --language c "sizeof (void*)"
25761 The valid language names are the same names accepted by the
25762 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
25763 @samp{local} or @samp{unknown}.
25765 @node Asynchronous and non-stop modes
25766 @subsection Asynchronous command execution and non-stop mode
25768 On some targets, @value{GDBN} is capable of processing MI commands
25769 even while the target is running. This is called @dfn{asynchronous
25770 command execution} (@pxref{Background Execution}). The frontend may
25771 specify a preferrence for asynchronous execution using the
25772 @code{-gdb-set mi-async 1} command, which should be emitted before
25773 either running the executable or attaching to the target. After the
25774 frontend has started the executable or attached to the target, it can
25775 find if asynchronous execution is enabled using the
25776 @code{-list-target-features} command.
25779 @item -gdb-set mi-async on
25780 @item -gdb-set mi-async off
25781 Set whether MI is in asynchronous mode.
25783 When @code{off}, which is the default, MI execution commands (e.g.,
25784 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
25785 for the program to stop before processing further commands.
25787 When @code{on}, MI execution commands are background execution
25788 commands (e.g., @code{-exec-continue} becomes the equivalent of the
25789 @code{c&} CLI command), and so @value{GDBN} is capable of processing
25790 MI commands even while the target is running.
25792 @item -gdb-show mi-async
25793 Show whether MI asynchronous mode is enabled.
25796 Note: In @value{GDBN} version 7.7 and earlier, this option was called
25797 @code{target-async} instead of @code{mi-async}, and it had the effect
25798 of both putting MI in asynchronous mode and making CLI background
25799 commands possible. CLI background commands are now always possible
25800 ``out of the box'' if the target supports them. The old spelling is
25801 kept as a deprecated alias for backwards compatibility.
25803 Even if @value{GDBN} can accept a command while target is running,
25804 many commands that access the target do not work when the target is
25805 running. Therefore, asynchronous command execution is most useful
25806 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
25807 it is possible to examine the state of one thread, while other threads
25810 When a given thread is running, MI commands that try to access the
25811 target in the context of that thread may not work, or may work only on
25812 some targets. In particular, commands that try to operate on thread's
25813 stack will not work, on any target. Commands that read memory, or
25814 modify breakpoints, may work or not work, depending on the target. Note
25815 that even commands that operate on global state, such as @code{print},
25816 @code{set}, and breakpoint commands, still access the target in the
25817 context of a specific thread, so frontend should try to find a
25818 stopped thread and perform the operation on that thread (using the
25819 @samp{--thread} option).
25821 Which commands will work in the context of a running thread is
25822 highly target dependent. However, the two commands
25823 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
25824 to find the state of a thread, will always work.
25826 @node Thread groups
25827 @subsection Thread groups
25828 @value{GDBN} may be used to debug several processes at the same time.
25829 On some platfroms, @value{GDBN} may support debugging of several
25830 hardware systems, each one having several cores with several different
25831 processes running on each core. This section describes the MI
25832 mechanism to support such debugging scenarios.
25834 The key observation is that regardless of the structure of the
25835 target, MI can have a global list of threads, because most commands that
25836 accept the @samp{--thread} option do not need to know what process that
25837 thread belongs to. Therefore, it is not necessary to introduce
25838 neither additional @samp{--process} option, nor an notion of the
25839 current process in the MI interface. The only strictly new feature
25840 that is required is the ability to find how the threads are grouped
25843 To allow the user to discover such grouping, and to support arbitrary
25844 hierarchy of machines/cores/processes, MI introduces the concept of a
25845 @dfn{thread group}. Thread group is a collection of threads and other
25846 thread groups. A thread group always has a string identifier, a type,
25847 and may have additional attributes specific to the type. A new
25848 command, @code{-list-thread-groups}, returns the list of top-level
25849 thread groups, which correspond to processes that @value{GDBN} is
25850 debugging at the moment. By passing an identifier of a thread group
25851 to the @code{-list-thread-groups} command, it is possible to obtain
25852 the members of specific thread group.
25854 To allow the user to easily discover processes, and other objects, he
25855 wishes to debug, a concept of @dfn{available thread group} is
25856 introduced. Available thread group is an thread group that
25857 @value{GDBN} is not debugging, but that can be attached to, using the
25858 @code{-target-attach} command. The list of available top-level thread
25859 groups can be obtained using @samp{-list-thread-groups --available}.
25860 In general, the content of a thread group may be only retrieved only
25861 after attaching to that thread group.
25863 Thread groups are related to inferiors (@pxref{Inferiors and
25864 Programs}). Each inferior corresponds to a thread group of a special
25865 type @samp{process}, and some additional operations are permitted on
25866 such thread groups.
25868 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25869 @node GDB/MI Command Syntax
25870 @section @sc{gdb/mi} Command Syntax
25873 * GDB/MI Input Syntax::
25874 * GDB/MI Output Syntax::
25877 @node GDB/MI Input Syntax
25878 @subsection @sc{gdb/mi} Input Syntax
25880 @cindex input syntax for @sc{gdb/mi}
25881 @cindex @sc{gdb/mi}, input syntax
25883 @item @var{command} @expansion{}
25884 @code{@var{cli-command} | @var{mi-command}}
25886 @item @var{cli-command} @expansion{}
25887 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
25888 @var{cli-command} is any existing @value{GDBN} CLI command.
25890 @item @var{mi-command} @expansion{}
25891 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
25892 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
25894 @item @var{token} @expansion{}
25895 "any sequence of digits"
25897 @item @var{option} @expansion{}
25898 @code{"-" @var{parameter} [ " " @var{parameter} ]}
25900 @item @var{parameter} @expansion{}
25901 @code{@var{non-blank-sequence} | @var{c-string}}
25903 @item @var{operation} @expansion{}
25904 @emph{any of the operations described in this chapter}
25906 @item @var{non-blank-sequence} @expansion{}
25907 @emph{anything, provided it doesn't contain special characters such as
25908 "-", @var{nl}, """ and of course " "}
25910 @item @var{c-string} @expansion{}
25911 @code{""" @var{seven-bit-iso-c-string-content} """}
25913 @item @var{nl} @expansion{}
25922 The CLI commands are still handled by the @sc{mi} interpreter; their
25923 output is described below.
25926 The @code{@var{token}}, when present, is passed back when the command
25930 Some @sc{mi} commands accept optional arguments as part of the parameter
25931 list. Each option is identified by a leading @samp{-} (dash) and may be
25932 followed by an optional argument parameter. Options occur first in the
25933 parameter list and can be delimited from normal parameters using
25934 @samp{--} (this is useful when some parameters begin with a dash).
25941 We want easy access to the existing CLI syntax (for debugging).
25944 We want it to be easy to spot a @sc{mi} operation.
25947 @node GDB/MI Output Syntax
25948 @subsection @sc{gdb/mi} Output Syntax
25950 @cindex output syntax of @sc{gdb/mi}
25951 @cindex @sc{gdb/mi}, output syntax
25952 The output from @sc{gdb/mi} consists of zero or more out-of-band records
25953 followed, optionally, by a single result record. This result record
25954 is for the most recent command. The sequence of output records is
25955 terminated by @samp{(gdb)}.
25957 If an input command was prefixed with a @code{@var{token}} then the
25958 corresponding output for that command will also be prefixed by that same
25962 @item @var{output} @expansion{}
25963 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
25965 @item @var{result-record} @expansion{}
25966 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
25968 @item @var{out-of-band-record} @expansion{}
25969 @code{@var{async-record} | @var{stream-record}}
25971 @item @var{async-record} @expansion{}
25972 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
25974 @item @var{exec-async-output} @expansion{}
25975 @code{[ @var{token} ] "*" @var{async-output nl}}
25977 @item @var{status-async-output} @expansion{}
25978 @code{[ @var{token} ] "+" @var{async-output nl}}
25980 @item @var{notify-async-output} @expansion{}
25981 @code{[ @var{token} ] "=" @var{async-output nl}}
25983 @item @var{async-output} @expansion{}
25984 @code{@var{async-class} ( "," @var{result} )*}
25986 @item @var{result-class} @expansion{}
25987 @code{"done" | "running" | "connected" | "error" | "exit"}
25989 @item @var{async-class} @expansion{}
25990 @code{"stopped" | @var{others}} (where @var{others} will be added
25991 depending on the needs---this is still in development).
25993 @item @var{result} @expansion{}
25994 @code{ @var{variable} "=" @var{value}}
25996 @item @var{variable} @expansion{}
25997 @code{ @var{string} }
25999 @item @var{value} @expansion{}
26000 @code{ @var{const} | @var{tuple} | @var{list} }
26002 @item @var{const} @expansion{}
26003 @code{@var{c-string}}
26005 @item @var{tuple} @expansion{}
26006 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
26008 @item @var{list} @expansion{}
26009 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
26010 @var{result} ( "," @var{result} )* "]" }
26012 @item @var{stream-record} @expansion{}
26013 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
26015 @item @var{console-stream-output} @expansion{}
26016 @code{"~" @var{c-string nl}}
26018 @item @var{target-stream-output} @expansion{}
26019 @code{"@@" @var{c-string nl}}
26021 @item @var{log-stream-output} @expansion{}
26022 @code{"&" @var{c-string nl}}
26024 @item @var{nl} @expansion{}
26027 @item @var{token} @expansion{}
26028 @emph{any sequence of digits}.
26036 All output sequences end in a single line containing a period.
26039 The @code{@var{token}} is from the corresponding request. Note that
26040 for all async output, while the token is allowed by the grammar and
26041 may be output by future versions of @value{GDBN} for select async
26042 output messages, it is generally omitted. Frontends should treat
26043 all async output as reporting general changes in the state of the
26044 target and there should be no need to associate async output to any
26048 @cindex status output in @sc{gdb/mi}
26049 @var{status-async-output} contains on-going status information about the
26050 progress of a slow operation. It can be discarded. All status output is
26051 prefixed by @samp{+}.
26054 @cindex async output in @sc{gdb/mi}
26055 @var{exec-async-output} contains asynchronous state change on the target
26056 (stopped, started, disappeared). All async output is prefixed by
26060 @cindex notify output in @sc{gdb/mi}
26061 @var{notify-async-output} contains supplementary information that the
26062 client should handle (e.g., a new breakpoint information). All notify
26063 output is prefixed by @samp{=}.
26066 @cindex console output in @sc{gdb/mi}
26067 @var{console-stream-output} is output that should be displayed as is in the
26068 console. It is the textual response to a CLI command. All the console
26069 output is prefixed by @samp{~}.
26072 @cindex target output in @sc{gdb/mi}
26073 @var{target-stream-output} is the output produced by the target program.
26074 All the target output is prefixed by @samp{@@}.
26077 @cindex log output in @sc{gdb/mi}
26078 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
26079 instance messages that should be displayed as part of an error log. All
26080 the log output is prefixed by @samp{&}.
26083 @cindex list output in @sc{gdb/mi}
26084 New @sc{gdb/mi} commands should only output @var{lists} containing
26090 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
26091 details about the various output records.
26093 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26094 @node GDB/MI Compatibility with CLI
26095 @section @sc{gdb/mi} Compatibility with CLI
26097 @cindex compatibility, @sc{gdb/mi} and CLI
26098 @cindex @sc{gdb/mi}, compatibility with CLI
26100 For the developers convenience CLI commands can be entered directly,
26101 but there may be some unexpected behaviour. For example, commands
26102 that query the user will behave as if the user replied yes, breakpoint
26103 command lists are not executed and some CLI commands, such as
26104 @code{if}, @code{when} and @code{define}, prompt for further input with
26105 @samp{>}, which is not valid MI output.
26107 This feature may be removed at some stage in the future and it is
26108 recommended that front ends use the @code{-interpreter-exec} command
26109 (@pxref{-interpreter-exec}).
26111 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26112 @node GDB/MI Development and Front Ends
26113 @section @sc{gdb/mi} Development and Front Ends
26114 @cindex @sc{gdb/mi} development
26116 The application which takes the MI output and presents the state of the
26117 program being debugged to the user is called a @dfn{front end}.
26119 Although @sc{gdb/mi} is still incomplete, it is currently being used
26120 by a variety of front ends to @value{GDBN}. This makes it difficult
26121 to introduce new functionality without breaking existing usage. This
26122 section tries to minimize the problems by describing how the protocol
26125 Some changes in MI need not break a carefully designed front end, and
26126 for these the MI version will remain unchanged. The following is a
26127 list of changes that may occur within one level, so front ends should
26128 parse MI output in a way that can handle them:
26132 New MI commands may be added.
26135 New fields may be added to the output of any MI command.
26138 The range of values for fields with specified values, e.g.,
26139 @code{in_scope} (@pxref{-var-update}) may be extended.
26141 @c The format of field's content e.g type prefix, may change so parse it
26142 @c at your own risk. Yes, in general?
26144 @c The order of fields may change? Shouldn't really matter but it might
26145 @c resolve inconsistencies.
26148 If the changes are likely to break front ends, the MI version level
26149 will be increased by one. This will allow the front end to parse the
26150 output according to the MI version. Apart from mi0, new versions of
26151 @value{GDBN} will not support old versions of MI and it will be the
26152 responsibility of the front end to work with the new one.
26154 @c Starting with mi3, add a new command -mi-version that prints the MI
26157 The best way to avoid unexpected changes in MI that might break your front
26158 end is to make your project known to @value{GDBN} developers and
26159 follow development on @email{gdb@@sourceware.org} and
26160 @email{gdb-patches@@sourceware.org}.
26161 @cindex mailing lists
26163 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26164 @node GDB/MI Output Records
26165 @section @sc{gdb/mi} Output Records
26168 * GDB/MI Result Records::
26169 * GDB/MI Stream Records::
26170 * GDB/MI Async Records::
26171 * GDB/MI Breakpoint Information::
26172 * GDB/MI Frame Information::
26173 * GDB/MI Thread Information::
26174 * GDB/MI Ada Exception Information::
26177 @node GDB/MI Result Records
26178 @subsection @sc{gdb/mi} Result Records
26180 @cindex result records in @sc{gdb/mi}
26181 @cindex @sc{gdb/mi}, result records
26182 In addition to a number of out-of-band notifications, the response to a
26183 @sc{gdb/mi} command includes one of the following result indications:
26187 @item "^done" [ "," @var{results} ]
26188 The synchronous operation was successful, @code{@var{results}} are the return
26193 This result record is equivalent to @samp{^done}. Historically, it
26194 was output instead of @samp{^done} if the command has resumed the
26195 target. This behaviour is maintained for backward compatibility, but
26196 all frontends should treat @samp{^done} and @samp{^running}
26197 identically and rely on the @samp{*running} output record to determine
26198 which threads are resumed.
26202 @value{GDBN} has connected to a remote target.
26204 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
26206 The operation failed. The @code{msg=@var{c-string}} variable contains
26207 the corresponding error message.
26209 If present, the @code{code=@var{c-string}} variable provides an error
26210 code on which consumers can rely on to detect the corresponding
26211 error condition. At present, only one error code is defined:
26214 @item "undefined-command"
26215 Indicates that the command causing the error does not exist.
26220 @value{GDBN} has terminated.
26224 @node GDB/MI Stream Records
26225 @subsection @sc{gdb/mi} Stream Records
26227 @cindex @sc{gdb/mi}, stream records
26228 @cindex stream records in @sc{gdb/mi}
26229 @value{GDBN} internally maintains a number of output streams: the console, the
26230 target, and the log. The output intended for each of these streams is
26231 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
26233 Each stream record begins with a unique @dfn{prefix character} which
26234 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
26235 Syntax}). In addition to the prefix, each stream record contains a
26236 @code{@var{string-output}}. This is either raw text (with an implicit new
26237 line) or a quoted C string (which does not contain an implicit newline).
26240 @item "~" @var{string-output}
26241 The console output stream contains text that should be displayed in the
26242 CLI console window. It contains the textual responses to CLI commands.
26244 @item "@@" @var{string-output}
26245 The target output stream contains any textual output from the running
26246 target. This is only present when GDB's event loop is truly
26247 asynchronous, which is currently only the case for remote targets.
26249 @item "&" @var{string-output}
26250 The log stream contains debugging messages being produced by @value{GDBN}'s
26254 @node GDB/MI Async Records
26255 @subsection @sc{gdb/mi} Async Records
26257 @cindex async records in @sc{gdb/mi}
26258 @cindex @sc{gdb/mi}, async records
26259 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
26260 additional changes that have occurred. Those changes can either be a
26261 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
26262 target activity (e.g., target stopped).
26264 The following is the list of possible async records:
26268 @item *running,thread-id="@var{thread}"
26269 The target is now running. The @var{thread} field tells which
26270 specific thread is now running, and can be @samp{all} if all threads
26271 are running. The frontend should assume that no interaction with a
26272 running thread is possible after this notification is produced.
26273 The frontend should not assume that this notification is output
26274 only once for any command. @value{GDBN} may emit this notification
26275 several times, either for different threads, because it cannot resume
26276 all threads together, or even for a single thread, if the thread must
26277 be stepped though some code before letting it run freely.
26279 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
26280 The target has stopped. The @var{reason} field can have one of the
26284 @item breakpoint-hit
26285 A breakpoint was reached.
26286 @item watchpoint-trigger
26287 A watchpoint was triggered.
26288 @item read-watchpoint-trigger
26289 A read watchpoint was triggered.
26290 @item access-watchpoint-trigger
26291 An access watchpoint was triggered.
26292 @item function-finished
26293 An -exec-finish or similar CLI command was accomplished.
26294 @item location-reached
26295 An -exec-until or similar CLI command was accomplished.
26296 @item watchpoint-scope
26297 A watchpoint has gone out of scope.
26298 @item end-stepping-range
26299 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
26300 similar CLI command was accomplished.
26301 @item exited-signalled
26302 The inferior exited because of a signal.
26304 The inferior exited.
26305 @item exited-normally
26306 The inferior exited normally.
26307 @item signal-received
26308 A signal was received by the inferior.
26310 The inferior has stopped due to a library being loaded or unloaded.
26311 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
26312 set or when a @code{catch load} or @code{catch unload} catchpoint is
26313 in use (@pxref{Set Catchpoints}).
26315 The inferior has forked. This is reported when @code{catch fork}
26316 (@pxref{Set Catchpoints}) has been used.
26318 The inferior has vforked. This is reported in when @code{catch vfork}
26319 (@pxref{Set Catchpoints}) has been used.
26320 @item syscall-entry
26321 The inferior entered a system call. This is reported when @code{catch
26322 syscall} (@pxref{Set Catchpoints}) has been used.
26323 @item syscall-return
26324 The inferior returned from a system call. This is reported when
26325 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
26327 The inferior called @code{exec}. This is reported when @code{catch exec}
26328 (@pxref{Set Catchpoints}) has been used.
26331 The @var{id} field identifies the thread that directly caused the stop
26332 -- for example by hitting a breakpoint. Depending on whether all-stop
26333 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
26334 stop all threads, or only the thread that directly triggered the stop.
26335 If all threads are stopped, the @var{stopped} field will have the
26336 value of @code{"all"}. Otherwise, the value of the @var{stopped}
26337 field will be a list of thread identifiers. Presently, this list will
26338 always include a single thread, but frontend should be prepared to see
26339 several threads in the list. The @var{core} field reports the
26340 processor core on which the stop event has happened. This field may be absent
26341 if such information is not available.
26343 @item =thread-group-added,id="@var{id}"
26344 @itemx =thread-group-removed,id="@var{id}"
26345 A thread group was either added or removed. The @var{id} field
26346 contains the @value{GDBN} identifier of the thread group. When a thread
26347 group is added, it generally might not be associated with a running
26348 process. When a thread group is removed, its id becomes invalid and
26349 cannot be used in any way.
26351 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
26352 A thread group became associated with a running program,
26353 either because the program was just started or the thread group
26354 was attached to a program. The @var{id} field contains the
26355 @value{GDBN} identifier of the thread group. The @var{pid} field
26356 contains process identifier, specific to the operating system.
26358 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
26359 A thread group is no longer associated with a running program,
26360 either because the program has exited, or because it was detached
26361 from. The @var{id} field contains the @value{GDBN} identifier of the
26362 thread group. The @var{code} field is the exit code of the inferior; it exists
26363 only when the inferior exited with some code.
26365 @item =thread-created,id="@var{id}",group-id="@var{gid}"
26366 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
26367 A thread either was created, or has exited. The @var{id} field
26368 contains the @value{GDBN} identifier of the thread. The @var{gid}
26369 field identifies the thread group this thread belongs to.
26371 @item =thread-selected,id="@var{id}"
26372 Informs that the selected thread was changed as result of the last
26373 command. This notification is not emitted as result of @code{-thread-select}
26374 command but is emitted whenever an MI command that is not documented
26375 to change the selected thread actually changes it. In particular,
26376 invoking, directly or indirectly (via user-defined command), the CLI
26377 @code{thread} command, will generate this notification.
26379 We suggest that in response to this notification, front ends
26380 highlight the selected thread and cause subsequent commands to apply to
26383 @item =library-loaded,...
26384 Reports that a new library file was loaded by the program. This
26385 notification has 4 fields---@var{id}, @var{target-name},
26386 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
26387 opaque identifier of the library. For remote debugging case,
26388 @var{target-name} and @var{host-name} fields give the name of the
26389 library file on the target, and on the host respectively. For native
26390 debugging, both those fields have the same value. The
26391 @var{symbols-loaded} field is emitted only for backward compatibility
26392 and should not be relied on to convey any useful information. The
26393 @var{thread-group} field, if present, specifies the id of the thread
26394 group in whose context the library was loaded. If the field is
26395 absent, it means the library was loaded in the context of all present
26398 @item =library-unloaded,...
26399 Reports that a library was unloaded by the program. This notification
26400 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
26401 the same meaning as for the @code{=library-loaded} notification.
26402 The @var{thread-group} field, if present, specifies the id of the
26403 thread group in whose context the library was unloaded. If the field is
26404 absent, it means the library was unloaded in the context of all present
26407 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
26408 @itemx =traceframe-changed,end
26409 Reports that the trace frame was changed and its new number is
26410 @var{tfnum}. The number of the tracepoint associated with this trace
26411 frame is @var{tpnum}.
26413 @item =tsv-created,name=@var{name},initial=@var{initial}
26414 Reports that the new trace state variable @var{name} is created with
26415 initial value @var{initial}.
26417 @item =tsv-deleted,name=@var{name}
26418 @itemx =tsv-deleted
26419 Reports that the trace state variable @var{name} is deleted or all
26420 trace state variables are deleted.
26422 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
26423 Reports that the trace state variable @var{name} is modified with
26424 the initial value @var{initial}. The current value @var{current} of
26425 trace state variable is optional and is reported if the current
26426 value of trace state variable is known.
26428 @item =breakpoint-created,bkpt=@{...@}
26429 @itemx =breakpoint-modified,bkpt=@{...@}
26430 @itemx =breakpoint-deleted,id=@var{number}
26431 Reports that a breakpoint was created, modified, or deleted,
26432 respectively. Only user-visible breakpoints are reported to the MI
26435 The @var{bkpt} argument is of the same form as returned by the various
26436 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
26437 @var{number} is the ordinal number of the breakpoint.
26439 Note that if a breakpoint is emitted in the result record of a
26440 command, then it will not also be emitted in an async record.
26442 @item =record-started,thread-group="@var{id}"
26443 @itemx =record-stopped,thread-group="@var{id}"
26444 Execution log recording was either started or stopped on an
26445 inferior. The @var{id} is the @value{GDBN} identifier of the thread
26446 group corresponding to the affected inferior.
26448 @item =cmd-param-changed,param=@var{param},value=@var{value}
26449 Reports that a parameter of the command @code{set @var{param}} is
26450 changed to @var{value}. In the multi-word @code{set} command,
26451 the @var{param} is the whole parameter list to @code{set} command.
26452 For example, In command @code{set check type on}, @var{param}
26453 is @code{check type} and @var{value} is @code{on}.
26455 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
26456 Reports that bytes from @var{addr} to @var{data} + @var{len} were
26457 written in an inferior. The @var{id} is the identifier of the
26458 thread group corresponding to the affected inferior. The optional
26459 @code{type="code"} part is reported if the memory written to holds
26463 @node GDB/MI Breakpoint Information
26464 @subsection @sc{gdb/mi} Breakpoint Information
26466 When @value{GDBN} reports information about a breakpoint, a
26467 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
26472 The breakpoint number. For a breakpoint that represents one location
26473 of a multi-location breakpoint, this will be a dotted pair, like
26477 The type of the breakpoint. For ordinary breakpoints this will be
26478 @samp{breakpoint}, but many values are possible.
26481 If the type of the breakpoint is @samp{catchpoint}, then this
26482 indicates the exact type of catchpoint.
26485 This is the breakpoint disposition---either @samp{del}, meaning that
26486 the breakpoint will be deleted at the next stop, or @samp{keep},
26487 meaning that the breakpoint will not be deleted.
26490 This indicates whether the breakpoint is enabled, in which case the
26491 value is @samp{y}, or disabled, in which case the value is @samp{n}.
26492 Note that this is not the same as the field @code{enable}.
26495 The address of the breakpoint. This may be a hexidecimal number,
26496 giving the address; or the string @samp{<PENDING>}, for a pending
26497 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
26498 multiple locations. This field will not be present if no address can
26499 be determined. For example, a watchpoint does not have an address.
26502 If known, the function in which the breakpoint appears.
26503 If not known, this field is not present.
26506 The name of the source file which contains this function, if known.
26507 If not known, this field is not present.
26510 The full file name of the source file which contains this function, if
26511 known. If not known, this field is not present.
26514 The line number at which this breakpoint appears, if known.
26515 If not known, this field is not present.
26518 If the source file is not known, this field may be provided. If
26519 provided, this holds the address of the breakpoint, possibly followed
26523 If this breakpoint is pending, this field is present and holds the
26524 text used to set the breakpoint, as entered by the user.
26527 Where this breakpoint's condition is evaluated, either @samp{host} or
26531 If this is a thread-specific breakpoint, then this identifies the
26532 thread in which the breakpoint can trigger.
26535 If this breakpoint is restricted to a particular Ada task, then this
26536 field will hold the task identifier.
26539 If the breakpoint is conditional, this is the condition expression.
26542 The ignore count of the breakpoint.
26545 The enable count of the breakpoint.
26547 @item traceframe-usage
26550 @item static-tracepoint-marker-string-id
26551 For a static tracepoint, the name of the static tracepoint marker.
26554 For a masked watchpoint, this is the mask.
26557 A tracepoint's pass count.
26559 @item original-location
26560 The location of the breakpoint as originally specified by the user.
26561 This field is optional.
26564 The number of times the breakpoint has been hit.
26567 This field is only given for tracepoints. This is either @samp{y},
26568 meaning that the tracepoint is installed, or @samp{n}, meaning that it
26572 Some extra data, the exact contents of which are type-dependent.
26576 For example, here is what the output of @code{-break-insert}
26577 (@pxref{GDB/MI Breakpoint Commands}) might be:
26580 -> -break-insert main
26581 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26582 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26583 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
26588 @node GDB/MI Frame Information
26589 @subsection @sc{gdb/mi} Frame Information
26591 Response from many MI commands includes an information about stack
26592 frame. This information is a tuple that may have the following
26597 The level of the stack frame. The innermost frame has the level of
26598 zero. This field is always present.
26601 The name of the function corresponding to the frame. This field may
26602 be absent if @value{GDBN} is unable to determine the function name.
26605 The code address for the frame. This field is always present.
26608 The name of the source files that correspond to the frame's code
26609 address. This field may be absent.
26612 The source line corresponding to the frames' code address. This field
26616 The name of the binary file (either executable or shared library) the
26617 corresponds to the frame's code address. This field may be absent.
26621 @node GDB/MI Thread Information
26622 @subsection @sc{gdb/mi} Thread Information
26624 Whenever @value{GDBN} has to report an information about a thread, it
26625 uses a tuple with the following fields:
26629 The numeric id assigned to the thread by @value{GDBN}. This field is
26633 Target-specific string identifying the thread. This field is always present.
26636 Additional information about the thread provided by the target.
26637 It is supposed to be human-readable and not interpreted by the
26638 frontend. This field is optional.
26641 Either @samp{stopped} or @samp{running}, depending on whether the
26642 thread is presently running. This field is always present.
26645 The value of this field is an integer number of the processor core the
26646 thread was last seen on. This field is optional.
26649 @node GDB/MI Ada Exception Information
26650 @subsection @sc{gdb/mi} Ada Exception Information
26652 Whenever a @code{*stopped} record is emitted because the program
26653 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
26654 @value{GDBN} provides the name of the exception that was raised via
26655 the @code{exception-name} field.
26657 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26658 @node GDB/MI Simple Examples
26659 @section Simple Examples of @sc{gdb/mi} Interaction
26660 @cindex @sc{gdb/mi}, simple examples
26662 This subsection presents several simple examples of interaction using
26663 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
26664 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
26665 the output received from @sc{gdb/mi}.
26667 Note the line breaks shown in the examples are here only for
26668 readability, they don't appear in the real output.
26670 @subheading Setting a Breakpoint
26672 Setting a breakpoint generates synchronous output which contains detailed
26673 information of the breakpoint.
26676 -> -break-insert main
26677 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26678 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26679 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
26684 @subheading Program Execution
26686 Program execution generates asynchronous records and MI gives the
26687 reason that execution stopped.
26693 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
26694 frame=@{addr="0x08048564",func="main",
26695 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
26696 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
26701 <- *stopped,reason="exited-normally"
26705 @subheading Quitting @value{GDBN}
26707 Quitting @value{GDBN} just prints the result class @samp{^exit}.
26715 Please note that @samp{^exit} is printed immediately, but it might
26716 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
26717 performs necessary cleanups, including killing programs being debugged
26718 or disconnecting from debug hardware, so the frontend should wait till
26719 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
26720 fails to exit in reasonable time.
26722 @subheading A Bad Command
26724 Here's what happens if you pass a non-existent command:
26728 <- ^error,msg="Undefined MI command: rubbish"
26733 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26734 @node GDB/MI Command Description Format
26735 @section @sc{gdb/mi} Command Description Format
26737 The remaining sections describe blocks of commands. Each block of
26738 commands is laid out in a fashion similar to this section.
26740 @subheading Motivation
26742 The motivation for this collection of commands.
26744 @subheading Introduction
26746 A brief introduction to this collection of commands as a whole.
26748 @subheading Commands
26750 For each command in the block, the following is described:
26752 @subsubheading Synopsis
26755 -command @var{args}@dots{}
26758 @subsubheading Result
26760 @subsubheading @value{GDBN} Command
26762 The corresponding @value{GDBN} CLI command(s), if any.
26764 @subsubheading Example
26766 Example(s) formatted for readability. Some of the described commands have
26767 not been implemented yet and these are labeled N.A.@: (not available).
26770 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26771 @node GDB/MI Breakpoint Commands
26772 @section @sc{gdb/mi} Breakpoint Commands
26774 @cindex breakpoint commands for @sc{gdb/mi}
26775 @cindex @sc{gdb/mi}, breakpoint commands
26776 This section documents @sc{gdb/mi} commands for manipulating
26779 @subheading The @code{-break-after} Command
26780 @findex -break-after
26782 @subsubheading Synopsis
26785 -break-after @var{number} @var{count}
26788 The breakpoint number @var{number} is not in effect until it has been
26789 hit @var{count} times. To see how this is reflected in the output of
26790 the @samp{-break-list} command, see the description of the
26791 @samp{-break-list} command below.
26793 @subsubheading @value{GDBN} Command
26795 The corresponding @value{GDBN} command is @samp{ignore}.
26797 @subsubheading Example
26802 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26803 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26804 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
26812 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26813 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26814 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26815 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26816 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26817 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26818 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26819 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26820 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26821 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
26826 @subheading The @code{-break-catch} Command
26827 @findex -break-catch
26830 @subheading The @code{-break-commands} Command
26831 @findex -break-commands
26833 @subsubheading Synopsis
26836 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
26839 Specifies the CLI commands that should be executed when breakpoint
26840 @var{number} is hit. The parameters @var{command1} to @var{commandN}
26841 are the commands. If no command is specified, any previously-set
26842 commands are cleared. @xref{Break Commands}. Typical use of this
26843 functionality is tracing a program, that is, printing of values of
26844 some variables whenever breakpoint is hit and then continuing.
26846 @subsubheading @value{GDBN} Command
26848 The corresponding @value{GDBN} command is @samp{commands}.
26850 @subsubheading Example
26855 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26856 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26857 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
26860 -break-commands 1 "print v" "continue"
26865 @subheading The @code{-break-condition} Command
26866 @findex -break-condition
26868 @subsubheading Synopsis
26871 -break-condition @var{number} @var{expr}
26874 Breakpoint @var{number} will stop the program only if the condition in
26875 @var{expr} is true. The condition becomes part of the
26876 @samp{-break-list} output (see the description of the @samp{-break-list}
26879 @subsubheading @value{GDBN} Command
26881 The corresponding @value{GDBN} command is @samp{condition}.
26883 @subsubheading Example
26887 -break-condition 1 1
26891 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26892 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26893 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26894 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26895 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26896 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26897 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26898 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26899 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26900 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
26904 @subheading The @code{-break-delete} Command
26905 @findex -break-delete
26907 @subsubheading Synopsis
26910 -break-delete ( @var{breakpoint} )+
26913 Delete the breakpoint(s) whose number(s) are specified in the argument
26914 list. This is obviously reflected in the breakpoint list.
26916 @subsubheading @value{GDBN} Command
26918 The corresponding @value{GDBN} command is @samp{delete}.
26920 @subsubheading Example
26928 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26929 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26930 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26931 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26932 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26933 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26934 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26939 @subheading The @code{-break-disable} Command
26940 @findex -break-disable
26942 @subsubheading Synopsis
26945 -break-disable ( @var{breakpoint} )+
26948 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
26949 break list is now set to @samp{n} for the named @var{breakpoint}(s).
26951 @subsubheading @value{GDBN} Command
26953 The corresponding @value{GDBN} command is @samp{disable}.
26955 @subsubheading Example
26963 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26964 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26965 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26966 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26967 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26968 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26969 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26970 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
26971 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26972 line="5",thread-groups=["i1"],times="0"@}]@}
26976 @subheading The @code{-break-enable} Command
26977 @findex -break-enable
26979 @subsubheading Synopsis
26982 -break-enable ( @var{breakpoint} )+
26985 Enable (previously disabled) @var{breakpoint}(s).
26987 @subsubheading @value{GDBN} Command
26989 The corresponding @value{GDBN} command is @samp{enable}.
26991 @subsubheading Example
26999 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27000 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27001 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27002 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27003 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27004 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27005 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27006 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27007 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27008 line="5",thread-groups=["i1"],times="0"@}]@}
27012 @subheading The @code{-break-info} Command
27013 @findex -break-info
27015 @subsubheading Synopsis
27018 -break-info @var{breakpoint}
27022 Get information about a single breakpoint.
27024 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
27025 Information}, for details on the format of each breakpoint in the
27028 @subsubheading @value{GDBN} Command
27030 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
27032 @subsubheading Example
27035 @subheading The @code{-break-insert} Command
27036 @findex -break-insert
27037 @anchor{-break-insert}
27039 @subsubheading Synopsis
27042 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
27043 [ -c @var{condition} ] [ -i @var{ignore-count} ]
27044 [ -p @var{thread-id} ] [ @var{location} ]
27048 If specified, @var{location}, can be one of:
27051 @item linespec location
27052 A linespec location. @xref{Linespec Locations}.
27054 @item explicit location
27055 An explicit location. @sc{gdb/mi} explicit locations are
27056 analogous to the CLI's explicit locations using the option names
27057 listed below. @xref{Explicit Locations}.
27060 @item --source @var{filename}
27061 The source file name of the location. This option requires the use
27062 of either @samp{--function} or @samp{--line}.
27064 @item --function @var{function}
27065 The name of a function or method.
27067 @item --label @var{label}
27068 The name of a label.
27070 @item --line @var{lineoffset}
27071 An absolute or relative line offset from the start of the location.
27074 @item address location
27075 An address location, *@var{address}. @xref{Address Locations}.
27079 The possible optional parameters of this command are:
27083 Insert a temporary breakpoint.
27085 Insert a hardware breakpoint.
27087 If @var{location} cannot be parsed (for example if it
27088 refers to unknown files or functions), create a pending
27089 breakpoint. Without this flag, @value{GDBN} will report
27090 an error, and won't create a breakpoint, if @var{location}
27093 Create a disabled breakpoint.
27095 Create a tracepoint. @xref{Tracepoints}. When this parameter
27096 is used together with @samp{-h}, a fast tracepoint is created.
27097 @item -c @var{condition}
27098 Make the breakpoint conditional on @var{condition}.
27099 @item -i @var{ignore-count}
27100 Initialize the @var{ignore-count}.
27101 @item -p @var{thread-id}
27102 Restrict the breakpoint to the specified @var{thread-id}.
27105 @subsubheading Result
27107 @xref{GDB/MI Breakpoint Information}, for details on the format of the
27108 resulting breakpoint.
27110 Note: this format is open to change.
27111 @c An out-of-band breakpoint instead of part of the result?
27113 @subsubheading @value{GDBN} Command
27115 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
27116 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
27118 @subsubheading Example
27123 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
27124 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
27127 -break-insert -t foo
27128 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
27129 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
27133 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27134 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27135 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27136 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27137 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27138 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27139 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27140 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27141 addr="0x0001072c", func="main",file="recursive2.c",
27142 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
27144 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
27145 addr="0x00010774",func="foo",file="recursive2.c",
27146 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
27149 @c -break-insert -r foo.*
27150 @c ~int foo(int, int);
27151 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
27152 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
27157 @subheading The @code{-dprintf-insert} Command
27158 @findex -dprintf-insert
27160 @subsubheading Synopsis
27163 -dprintf-insert [ -t ] [ -f ] [ -d ]
27164 [ -c @var{condition} ] [ -i @var{ignore-count} ]
27165 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
27170 If supplied, @var{location} may be specified the same way as for
27171 the @code{-break-insert} command. @xref{-break-insert}.
27173 The possible optional parameters of this command are:
27177 Insert a temporary breakpoint.
27179 If @var{location} cannot be parsed (for example, if it
27180 refers to unknown files or functions), create a pending
27181 breakpoint. Without this flag, @value{GDBN} will report
27182 an error, and won't create a breakpoint, if @var{location}
27185 Create a disabled breakpoint.
27186 @item -c @var{condition}
27187 Make the breakpoint conditional on @var{condition}.
27188 @item -i @var{ignore-count}
27189 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
27190 to @var{ignore-count}.
27191 @item -p @var{thread-id}
27192 Restrict the breakpoint to the specified @var{thread-id}.
27195 @subsubheading Result
27197 @xref{GDB/MI Breakpoint Information}, for details on the format of the
27198 resulting breakpoint.
27200 @c An out-of-band breakpoint instead of part of the result?
27202 @subsubheading @value{GDBN} Command
27204 The corresponding @value{GDBN} command is @samp{dprintf}.
27206 @subsubheading Example
27210 4-dprintf-insert foo "At foo entry\n"
27211 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
27212 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
27213 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
27214 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
27215 original-location="foo"@}
27217 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
27218 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
27219 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
27220 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
27221 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
27222 original-location="mi-dprintf.c:26"@}
27226 @subheading The @code{-break-list} Command
27227 @findex -break-list
27229 @subsubheading Synopsis
27235 Displays the list of inserted breakpoints, showing the following fields:
27239 number of the breakpoint
27241 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
27243 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
27246 is the breakpoint enabled or no: @samp{y} or @samp{n}
27248 memory location at which the breakpoint is set
27250 logical location of the breakpoint, expressed by function name, file
27252 @item Thread-groups
27253 list of thread groups to which this breakpoint applies
27255 number of times the breakpoint has been hit
27258 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
27259 @code{body} field is an empty list.
27261 @subsubheading @value{GDBN} Command
27263 The corresponding @value{GDBN} command is @samp{info break}.
27265 @subsubheading Example
27270 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27271 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27272 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27273 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27274 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27275 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27276 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27277 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27278 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
27280 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27281 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
27282 line="13",thread-groups=["i1"],times="0"@}]@}
27286 Here's an example of the result when there are no breakpoints:
27291 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27292 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27293 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27294 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27295 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27296 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27297 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27302 @subheading The @code{-break-passcount} Command
27303 @findex -break-passcount
27305 @subsubheading Synopsis
27308 -break-passcount @var{tracepoint-number} @var{passcount}
27311 Set the passcount for tracepoint @var{tracepoint-number} to
27312 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
27313 is not a tracepoint, error is emitted. This corresponds to CLI
27314 command @samp{passcount}.
27316 @subheading The @code{-break-watch} Command
27317 @findex -break-watch
27319 @subsubheading Synopsis
27322 -break-watch [ -a | -r ]
27325 Create a watchpoint. With the @samp{-a} option it will create an
27326 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
27327 read from or on a write to the memory location. With the @samp{-r}
27328 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
27329 trigger only when the memory location is accessed for reading. Without
27330 either of the options, the watchpoint created is a regular watchpoint,
27331 i.e., it will trigger when the memory location is accessed for writing.
27332 @xref{Set Watchpoints, , Setting Watchpoints}.
27334 Note that @samp{-break-list} will report a single list of watchpoints and
27335 breakpoints inserted.
27337 @subsubheading @value{GDBN} Command
27339 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
27342 @subsubheading Example
27344 Setting a watchpoint on a variable in the @code{main} function:
27349 ^done,wpt=@{number="2",exp="x"@}
27354 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
27355 value=@{old="-268439212",new="55"@},
27356 frame=@{func="main",args=[],file="recursive2.c",
27357 fullname="/home/foo/bar/recursive2.c",line="5"@}
27361 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
27362 the program execution twice: first for the variable changing value, then
27363 for the watchpoint going out of scope.
27368 ^done,wpt=@{number="5",exp="C"@}
27373 *stopped,reason="watchpoint-trigger",
27374 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
27375 frame=@{func="callee4",args=[],
27376 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27377 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27382 *stopped,reason="watchpoint-scope",wpnum="5",
27383 frame=@{func="callee3",args=[@{name="strarg",
27384 value="0x11940 \"A string argument.\""@}],
27385 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27386 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27390 Listing breakpoints and watchpoints, at different points in the program
27391 execution. Note that once the watchpoint goes out of scope, it is
27397 ^done,wpt=@{number="2",exp="C"@}
27400 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27401 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27402 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27403 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27404 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27405 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27406 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27407 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27408 addr="0x00010734",func="callee4",
27409 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27410 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
27412 bkpt=@{number="2",type="watchpoint",disp="keep",
27413 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
27418 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
27419 value=@{old="-276895068",new="3"@},
27420 frame=@{func="callee4",args=[],
27421 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27422 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27425 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27426 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27427 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27428 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27429 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27430 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27431 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27432 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27433 addr="0x00010734",func="callee4",
27434 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27435 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
27437 bkpt=@{number="2",type="watchpoint",disp="keep",
27438 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
27442 ^done,reason="watchpoint-scope",wpnum="2",
27443 frame=@{func="callee3",args=[@{name="strarg",
27444 value="0x11940 \"A string argument.\""@}],
27445 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27446 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27449 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27450 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27451 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27452 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27453 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27454 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27455 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27456 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27457 addr="0x00010734",func="callee4",
27458 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27459 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
27460 thread-groups=["i1"],times="1"@}]@}
27465 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27466 @node GDB/MI Catchpoint Commands
27467 @section @sc{gdb/mi} Catchpoint Commands
27469 This section documents @sc{gdb/mi} commands for manipulating
27473 * Shared Library GDB/MI Catchpoint Commands::
27474 * Ada Exception GDB/MI Catchpoint Commands::
27477 @node Shared Library GDB/MI Catchpoint Commands
27478 @subsection Shared Library @sc{gdb/mi} Catchpoints
27480 @subheading The @code{-catch-load} Command
27481 @findex -catch-load
27483 @subsubheading Synopsis
27486 -catch-load [ -t ] [ -d ] @var{regexp}
27489 Add a catchpoint for library load events. If the @samp{-t} option is used,
27490 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
27491 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
27492 in a disabled state. The @samp{regexp} argument is a regular
27493 expression used to match the name of the loaded library.
27496 @subsubheading @value{GDBN} Command
27498 The corresponding @value{GDBN} command is @samp{catch load}.
27500 @subsubheading Example
27503 -catch-load -t foo.so
27504 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
27505 what="load of library matching foo.so",catch-type="load",times="0"@}
27510 @subheading The @code{-catch-unload} Command
27511 @findex -catch-unload
27513 @subsubheading Synopsis
27516 -catch-unload [ -t ] [ -d ] @var{regexp}
27519 Add a catchpoint for library unload events. If the @samp{-t} option is
27520 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
27521 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
27522 created in a disabled state. The @samp{regexp} argument is a regular
27523 expression used to match the name of the unloaded library.
27525 @subsubheading @value{GDBN} Command
27527 The corresponding @value{GDBN} command is @samp{catch unload}.
27529 @subsubheading Example
27532 -catch-unload -d bar.so
27533 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
27534 what="load of library matching bar.so",catch-type="unload",times="0"@}
27538 @node Ada Exception GDB/MI Catchpoint Commands
27539 @subsection Ada Exception @sc{gdb/mi} Catchpoints
27541 The following @sc{gdb/mi} commands can be used to create catchpoints
27542 that stop the execution when Ada exceptions are being raised.
27544 @subheading The @code{-catch-assert} Command
27545 @findex -catch-assert
27547 @subsubheading Synopsis
27550 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
27553 Add a catchpoint for failed Ada assertions.
27555 The possible optional parameters for this command are:
27558 @item -c @var{condition}
27559 Make the catchpoint conditional on @var{condition}.
27561 Create a disabled catchpoint.
27563 Create a temporary catchpoint.
27566 @subsubheading @value{GDBN} Command
27568 The corresponding @value{GDBN} command is @samp{catch assert}.
27570 @subsubheading Example
27574 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
27575 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
27576 thread-groups=["i1"],times="0",
27577 original-location="__gnat_debug_raise_assert_failure"@}
27581 @subheading The @code{-catch-exception} Command
27582 @findex -catch-exception
27584 @subsubheading Synopsis
27587 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
27591 Add a catchpoint stopping when Ada exceptions are raised.
27592 By default, the command stops the program when any Ada exception
27593 gets raised. But it is also possible, by using some of the
27594 optional parameters described below, to create more selective
27597 The possible optional parameters for this command are:
27600 @item -c @var{condition}
27601 Make the catchpoint conditional on @var{condition}.
27603 Create a disabled catchpoint.
27604 @item -e @var{exception-name}
27605 Only stop when @var{exception-name} is raised. This option cannot
27606 be used combined with @samp{-u}.
27608 Create a temporary catchpoint.
27610 Stop only when an unhandled exception gets raised. This option
27611 cannot be used combined with @samp{-e}.
27614 @subsubheading @value{GDBN} Command
27616 The corresponding @value{GDBN} commands are @samp{catch exception}
27617 and @samp{catch exception unhandled}.
27619 @subsubheading Example
27622 -catch-exception -e Program_Error
27623 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
27624 enabled="y",addr="0x0000000000404874",
27625 what="`Program_Error' Ada exception", thread-groups=["i1"],
27626 times="0",original-location="__gnat_debug_raise_exception"@}
27630 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27631 @node GDB/MI Program Context
27632 @section @sc{gdb/mi} Program Context
27634 @subheading The @code{-exec-arguments} Command
27635 @findex -exec-arguments
27638 @subsubheading Synopsis
27641 -exec-arguments @var{args}
27644 Set the inferior program arguments, to be used in the next
27647 @subsubheading @value{GDBN} Command
27649 The corresponding @value{GDBN} command is @samp{set args}.
27651 @subsubheading Example
27655 -exec-arguments -v word
27662 @subheading The @code{-exec-show-arguments} Command
27663 @findex -exec-show-arguments
27665 @subsubheading Synopsis
27668 -exec-show-arguments
27671 Print the arguments of the program.
27673 @subsubheading @value{GDBN} Command
27675 The corresponding @value{GDBN} command is @samp{show args}.
27677 @subsubheading Example
27682 @subheading The @code{-environment-cd} Command
27683 @findex -environment-cd
27685 @subsubheading Synopsis
27688 -environment-cd @var{pathdir}
27691 Set @value{GDBN}'s working directory.
27693 @subsubheading @value{GDBN} Command
27695 The corresponding @value{GDBN} command is @samp{cd}.
27697 @subsubheading Example
27701 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27707 @subheading The @code{-environment-directory} Command
27708 @findex -environment-directory
27710 @subsubheading Synopsis
27713 -environment-directory [ -r ] [ @var{pathdir} ]+
27716 Add directories @var{pathdir} to beginning of search path for source files.
27717 If the @samp{-r} option is used, the search path is reset to the default
27718 search path. If directories @var{pathdir} are supplied in addition to the
27719 @samp{-r} option, the search path is first reset and then addition
27721 Multiple directories may be specified, separated by blanks. Specifying
27722 multiple directories in a single command
27723 results in the directories added to the beginning of the
27724 search path in the same order they were presented in the command.
27725 If blanks are needed as
27726 part of a directory name, double-quotes should be used around
27727 the name. In the command output, the path will show up separated
27728 by the system directory-separator character. The directory-separator
27729 character must not be used
27730 in any directory name.
27731 If no directories are specified, the current search path is displayed.
27733 @subsubheading @value{GDBN} Command
27735 The corresponding @value{GDBN} command is @samp{dir}.
27737 @subsubheading Example
27741 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27742 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27744 -environment-directory ""
27745 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27747 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
27748 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
27750 -environment-directory -r
27751 ^done,source-path="$cdir:$cwd"
27756 @subheading The @code{-environment-path} Command
27757 @findex -environment-path
27759 @subsubheading Synopsis
27762 -environment-path [ -r ] [ @var{pathdir} ]+
27765 Add directories @var{pathdir} to beginning of search path for object files.
27766 If the @samp{-r} option is used, the search path is reset to the original
27767 search path that existed at gdb start-up. If directories @var{pathdir} are
27768 supplied in addition to the
27769 @samp{-r} option, the search path is first reset and then addition
27771 Multiple directories may be specified, separated by blanks. Specifying
27772 multiple directories in a single command
27773 results in the directories added to the beginning of the
27774 search path in the same order they were presented in the command.
27775 If blanks are needed as
27776 part of a directory name, double-quotes should be used around
27777 the name. In the command output, the path will show up separated
27778 by the system directory-separator character. The directory-separator
27779 character must not be used
27780 in any directory name.
27781 If no directories are specified, the current path is displayed.
27784 @subsubheading @value{GDBN} Command
27786 The corresponding @value{GDBN} command is @samp{path}.
27788 @subsubheading Example
27793 ^done,path="/usr/bin"
27795 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
27796 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
27798 -environment-path -r /usr/local/bin
27799 ^done,path="/usr/local/bin:/usr/bin"
27804 @subheading The @code{-environment-pwd} Command
27805 @findex -environment-pwd
27807 @subsubheading Synopsis
27813 Show the current working directory.
27815 @subsubheading @value{GDBN} Command
27817 The corresponding @value{GDBN} command is @samp{pwd}.
27819 @subsubheading Example
27824 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
27828 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27829 @node GDB/MI Thread Commands
27830 @section @sc{gdb/mi} Thread Commands
27833 @subheading The @code{-thread-info} Command
27834 @findex -thread-info
27836 @subsubheading Synopsis
27839 -thread-info [ @var{thread-id} ]
27842 Reports information about either a specific thread, if
27843 the @var{thread-id} parameter is present, or about all
27844 threads. When printing information about all threads,
27845 also reports the current thread.
27847 @subsubheading @value{GDBN} Command
27849 The @samp{info thread} command prints the same information
27852 @subsubheading Result
27854 The result is a list of threads. The following attributes are
27855 defined for a given thread:
27859 This field exists only for the current thread. It has the value @samp{*}.
27862 The identifier that @value{GDBN} uses to refer to the thread.
27865 The identifier that the target uses to refer to the thread.
27868 Extra information about the thread, in a target-specific format. This
27872 The name of the thread. If the user specified a name using the
27873 @code{thread name} command, then this name is given. Otherwise, if
27874 @value{GDBN} can extract the thread name from the target, then that
27875 name is given. If @value{GDBN} cannot find the thread name, then this
27879 The stack frame currently executing in the thread.
27882 The thread's state. The @samp{state} field may have the following
27887 The thread is stopped. Frame information is available for stopped
27891 The thread is running. There's no frame information for running
27897 If @value{GDBN} can find the CPU core on which this thread is running,
27898 then this field is the core identifier. This field is optional.
27902 @subsubheading Example
27907 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
27908 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
27909 args=[]@},state="running"@},
27910 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
27911 frame=@{level="0",addr="0x0804891f",func="foo",
27912 args=[@{name="i",value="10"@}],
27913 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
27914 state="running"@}],
27915 current-thread-id="1"
27919 @subheading The @code{-thread-list-ids} Command
27920 @findex -thread-list-ids
27922 @subsubheading Synopsis
27928 Produces a list of the currently known @value{GDBN} thread ids. At the
27929 end of the list it also prints the total number of such threads.
27931 This command is retained for historical reasons, the
27932 @code{-thread-info} command should be used instead.
27934 @subsubheading @value{GDBN} Command
27936 Part of @samp{info threads} supplies the same information.
27938 @subsubheading Example
27943 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27944 current-thread-id="1",number-of-threads="3"
27949 @subheading The @code{-thread-select} Command
27950 @findex -thread-select
27952 @subsubheading Synopsis
27955 -thread-select @var{threadnum}
27958 Make @var{threadnum} the current thread. It prints the number of the new
27959 current thread, and the topmost frame for that thread.
27961 This command is deprecated in favor of explicitly using the
27962 @samp{--thread} option to each command.
27964 @subsubheading @value{GDBN} Command
27966 The corresponding @value{GDBN} command is @samp{thread}.
27968 @subsubheading Example
27975 *stopped,reason="end-stepping-range",thread-id="2",line="187",
27976 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
27980 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27981 number-of-threads="3"
27984 ^done,new-thread-id="3",
27985 frame=@{level="0",func="vprintf",
27986 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
27987 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
27991 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27992 @node GDB/MI Ada Tasking Commands
27993 @section @sc{gdb/mi} Ada Tasking Commands
27995 @subheading The @code{-ada-task-info} Command
27996 @findex -ada-task-info
27998 @subsubheading Synopsis
28001 -ada-task-info [ @var{task-id} ]
28004 Reports information about either a specific Ada task, if the
28005 @var{task-id} parameter is present, or about all Ada tasks.
28007 @subsubheading @value{GDBN} Command
28009 The @samp{info tasks} command prints the same information
28010 about all Ada tasks (@pxref{Ada Tasks}).
28012 @subsubheading Result
28014 The result is a table of Ada tasks. The following columns are
28015 defined for each Ada task:
28019 This field exists only for the current thread. It has the value @samp{*}.
28022 The identifier that @value{GDBN} uses to refer to the Ada task.
28025 The identifier that the target uses to refer to the Ada task.
28028 The identifier of the thread corresponding to the Ada task.
28030 This field should always exist, as Ada tasks are always implemented
28031 on top of a thread. But if @value{GDBN} cannot find this corresponding
28032 thread for any reason, the field is omitted.
28035 This field exists only when the task was created by another task.
28036 In this case, it provides the ID of the parent task.
28039 The base priority of the task.
28042 The current state of the task. For a detailed description of the
28043 possible states, see @ref{Ada Tasks}.
28046 The name of the task.
28050 @subsubheading Example
28054 ^done,tasks=@{nr_rows="3",nr_cols="8",
28055 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
28056 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
28057 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
28058 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
28059 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
28060 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
28061 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
28062 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
28063 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
28064 state="Child Termination Wait",name="main_task"@}]@}
28068 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28069 @node GDB/MI Program Execution
28070 @section @sc{gdb/mi} Program Execution
28072 These are the asynchronous commands which generate the out-of-band
28073 record @samp{*stopped}. Currently @value{GDBN} only really executes
28074 asynchronously with remote targets and this interaction is mimicked in
28077 @subheading The @code{-exec-continue} Command
28078 @findex -exec-continue
28080 @subsubheading Synopsis
28083 -exec-continue [--reverse] [--all|--thread-group N]
28086 Resumes the execution of the inferior program, which will continue
28087 to execute until it reaches a debugger stop event. If the
28088 @samp{--reverse} option is specified, execution resumes in reverse until
28089 it reaches a stop event. Stop events may include
28092 breakpoints or watchpoints
28094 signals or exceptions
28096 the end of the process (or its beginning under @samp{--reverse})
28098 the end or beginning of a replay log if one is being used.
28100 In all-stop mode (@pxref{All-Stop
28101 Mode}), may resume only one thread, or all threads, depending on the
28102 value of the @samp{scheduler-locking} variable. If @samp{--all} is
28103 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
28104 ignored in all-stop mode. If the @samp{--thread-group} options is
28105 specified, then all threads in that thread group are resumed.
28107 @subsubheading @value{GDBN} Command
28109 The corresponding @value{GDBN} corresponding is @samp{continue}.
28111 @subsubheading Example
28118 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
28119 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
28125 @subheading The @code{-exec-finish} Command
28126 @findex -exec-finish
28128 @subsubheading Synopsis
28131 -exec-finish [--reverse]
28134 Resumes the execution of the inferior program until the current
28135 function is exited. Displays the results returned by the function.
28136 If the @samp{--reverse} option is specified, resumes the reverse
28137 execution of the inferior program until the point where current
28138 function was called.
28140 @subsubheading @value{GDBN} Command
28142 The corresponding @value{GDBN} command is @samp{finish}.
28144 @subsubheading Example
28146 Function returning @code{void}.
28153 *stopped,reason="function-finished",frame=@{func="main",args=[],
28154 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
28158 Function returning other than @code{void}. The name of the internal
28159 @value{GDBN} variable storing the result is printed, together with the
28166 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
28167 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
28168 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28169 gdb-result-var="$1",return-value="0"
28174 @subheading The @code{-exec-interrupt} Command
28175 @findex -exec-interrupt
28177 @subsubheading Synopsis
28180 -exec-interrupt [--all|--thread-group N]
28183 Interrupts the background execution of the target. Note how the token
28184 associated with the stop message is the one for the execution command
28185 that has been interrupted. The token for the interrupt itself only
28186 appears in the @samp{^done} output. If the user is trying to
28187 interrupt a non-running program, an error message will be printed.
28189 Note that when asynchronous execution is enabled, this command is
28190 asynchronous just like other execution commands. That is, first the
28191 @samp{^done} response will be printed, and the target stop will be
28192 reported after that using the @samp{*stopped} notification.
28194 In non-stop mode, only the context thread is interrupted by default.
28195 All threads (in all inferiors) will be interrupted if the
28196 @samp{--all} option is specified. If the @samp{--thread-group}
28197 option is specified, all threads in that group will be interrupted.
28199 @subsubheading @value{GDBN} Command
28201 The corresponding @value{GDBN} command is @samp{interrupt}.
28203 @subsubheading Example
28214 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
28215 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
28216 fullname="/home/foo/bar/try.c",line="13"@}
28221 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
28225 @subheading The @code{-exec-jump} Command
28228 @subsubheading Synopsis
28231 -exec-jump @var{location}
28234 Resumes execution of the inferior program at the location specified by
28235 parameter. @xref{Specify Location}, for a description of the
28236 different forms of @var{location}.
28238 @subsubheading @value{GDBN} Command
28240 The corresponding @value{GDBN} command is @samp{jump}.
28242 @subsubheading Example
28245 -exec-jump foo.c:10
28246 *running,thread-id="all"
28251 @subheading The @code{-exec-next} Command
28254 @subsubheading Synopsis
28257 -exec-next [--reverse]
28260 Resumes execution of the inferior program, stopping when the beginning
28261 of the next source line is reached.
28263 If the @samp{--reverse} option is specified, resumes reverse execution
28264 of the inferior program, stopping at the beginning of the previous
28265 source line. If you issue this command on the first line of a
28266 function, it will take you back to the caller of that function, to the
28267 source line where the function was called.
28270 @subsubheading @value{GDBN} Command
28272 The corresponding @value{GDBN} command is @samp{next}.
28274 @subsubheading Example
28280 *stopped,reason="end-stepping-range",line="8",file="hello.c"
28285 @subheading The @code{-exec-next-instruction} Command
28286 @findex -exec-next-instruction
28288 @subsubheading Synopsis
28291 -exec-next-instruction [--reverse]
28294 Executes one machine instruction. If the instruction is a function
28295 call, continues until the function returns. If the program stops at an
28296 instruction in the middle of a source line, the address will be
28299 If the @samp{--reverse} option is specified, resumes reverse execution
28300 of the inferior program, stopping at the previous instruction. If the
28301 previously executed instruction was a return from another function,
28302 it will continue to execute in reverse until the call to that function
28303 (from the current stack frame) is reached.
28305 @subsubheading @value{GDBN} Command
28307 The corresponding @value{GDBN} command is @samp{nexti}.
28309 @subsubheading Example
28313 -exec-next-instruction
28317 *stopped,reason="end-stepping-range",
28318 addr="0x000100d4",line="5",file="hello.c"
28323 @subheading The @code{-exec-return} Command
28324 @findex -exec-return
28326 @subsubheading Synopsis
28332 Makes current function return immediately. Doesn't execute the inferior.
28333 Displays the new current frame.
28335 @subsubheading @value{GDBN} Command
28337 The corresponding @value{GDBN} command is @samp{return}.
28339 @subsubheading Example
28343 200-break-insert callee4
28344 200^done,bkpt=@{number="1",addr="0x00010734",
28345 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28350 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28351 frame=@{func="callee4",args=[],
28352 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28353 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28359 111^done,frame=@{level="0",func="callee3",
28360 args=[@{name="strarg",
28361 value="0x11940 \"A string argument.\""@}],
28362 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28363 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28368 @subheading The @code{-exec-run} Command
28371 @subsubheading Synopsis
28374 -exec-run [ --all | --thread-group N ] [ --start ]
28377 Starts execution of the inferior from the beginning. The inferior
28378 executes until either a breakpoint is encountered or the program
28379 exits. In the latter case the output will include an exit code, if
28380 the program has exited exceptionally.
28382 When neither the @samp{--all} nor the @samp{--thread-group} option
28383 is specified, the current inferior is started. If the
28384 @samp{--thread-group} option is specified, it should refer to a thread
28385 group of type @samp{process}, and that thread group will be started.
28386 If the @samp{--all} option is specified, then all inferiors will be started.
28388 Using the @samp{--start} option instructs the debugger to stop
28389 the execution at the start of the inferior's main subprogram,
28390 following the same behavior as the @code{start} command
28391 (@pxref{Starting}).
28393 @subsubheading @value{GDBN} Command
28395 The corresponding @value{GDBN} command is @samp{run}.
28397 @subsubheading Examples
28402 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
28407 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28408 frame=@{func="main",args=[],file="recursive2.c",
28409 fullname="/home/foo/bar/recursive2.c",line="4"@}
28414 Program exited normally:
28422 *stopped,reason="exited-normally"
28427 Program exited exceptionally:
28435 *stopped,reason="exited",exit-code="01"
28439 Another way the program can terminate is if it receives a signal such as
28440 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
28444 *stopped,reason="exited-signalled",signal-name="SIGINT",
28445 signal-meaning="Interrupt"
28449 @c @subheading -exec-signal
28452 @subheading The @code{-exec-step} Command
28455 @subsubheading Synopsis
28458 -exec-step [--reverse]
28461 Resumes execution of the inferior program, stopping when the beginning
28462 of the next source line is reached, if the next source line is not a
28463 function call. If it is, stop at the first instruction of the called
28464 function. If the @samp{--reverse} option is specified, resumes reverse
28465 execution of the inferior program, stopping at the beginning of the
28466 previously executed source line.
28468 @subsubheading @value{GDBN} Command
28470 The corresponding @value{GDBN} command is @samp{step}.
28472 @subsubheading Example
28474 Stepping into a function:
28480 *stopped,reason="end-stepping-range",
28481 frame=@{func="foo",args=[@{name="a",value="10"@},
28482 @{name="b",value="0"@}],file="recursive2.c",
28483 fullname="/home/foo/bar/recursive2.c",line="11"@}
28493 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
28498 @subheading The @code{-exec-step-instruction} Command
28499 @findex -exec-step-instruction
28501 @subsubheading Synopsis
28504 -exec-step-instruction [--reverse]
28507 Resumes the inferior which executes one machine instruction. If the
28508 @samp{--reverse} option is specified, resumes reverse execution of the
28509 inferior program, stopping at the previously executed instruction.
28510 The output, once @value{GDBN} has stopped, will vary depending on
28511 whether we have stopped in the middle of a source line or not. In the
28512 former case, the address at which the program stopped will be printed
28515 @subsubheading @value{GDBN} Command
28517 The corresponding @value{GDBN} command is @samp{stepi}.
28519 @subsubheading Example
28523 -exec-step-instruction
28527 *stopped,reason="end-stepping-range",
28528 frame=@{func="foo",args=[],file="try.c",
28529 fullname="/home/foo/bar/try.c",line="10"@}
28531 -exec-step-instruction
28535 *stopped,reason="end-stepping-range",
28536 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
28537 fullname="/home/foo/bar/try.c",line="10"@}
28542 @subheading The @code{-exec-until} Command
28543 @findex -exec-until
28545 @subsubheading Synopsis
28548 -exec-until [ @var{location} ]
28551 Executes the inferior until the @var{location} specified in the
28552 argument is reached. If there is no argument, the inferior executes
28553 until a source line greater than the current one is reached. The
28554 reason for stopping in this case will be @samp{location-reached}.
28556 @subsubheading @value{GDBN} Command
28558 The corresponding @value{GDBN} command is @samp{until}.
28560 @subsubheading Example
28564 -exec-until recursive2.c:6
28568 *stopped,reason="location-reached",frame=@{func="main",args=[],
28569 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
28574 @subheading -file-clear
28575 Is this going away????
28578 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28579 @node GDB/MI Stack Manipulation
28580 @section @sc{gdb/mi} Stack Manipulation Commands
28582 @subheading The @code{-enable-frame-filters} Command
28583 @findex -enable-frame-filters
28586 -enable-frame-filters
28589 @value{GDBN} allows Python-based frame filters to affect the output of
28590 the MI commands relating to stack traces. As there is no way to
28591 implement this in a fully backward-compatible way, a front end must
28592 request that this functionality be enabled.
28594 Once enabled, this feature cannot be disabled.
28596 Note that if Python support has not been compiled into @value{GDBN},
28597 this command will still succeed (and do nothing).
28599 @subheading The @code{-stack-info-frame} Command
28600 @findex -stack-info-frame
28602 @subsubheading Synopsis
28608 Get info on the selected frame.
28610 @subsubheading @value{GDBN} Command
28612 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
28613 (without arguments).
28615 @subsubheading Example
28620 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
28621 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28622 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
28626 @subheading The @code{-stack-info-depth} Command
28627 @findex -stack-info-depth
28629 @subsubheading Synopsis
28632 -stack-info-depth [ @var{max-depth} ]
28635 Return the depth of the stack. If the integer argument @var{max-depth}
28636 is specified, do not count beyond @var{max-depth} frames.
28638 @subsubheading @value{GDBN} Command
28640 There's no equivalent @value{GDBN} command.
28642 @subsubheading Example
28644 For a stack with frame levels 0 through 11:
28651 -stack-info-depth 4
28654 -stack-info-depth 12
28657 -stack-info-depth 11
28660 -stack-info-depth 13
28665 @anchor{-stack-list-arguments}
28666 @subheading The @code{-stack-list-arguments} Command
28667 @findex -stack-list-arguments
28669 @subsubheading Synopsis
28672 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28673 [ @var{low-frame} @var{high-frame} ]
28676 Display a list of the arguments for the frames between @var{low-frame}
28677 and @var{high-frame} (inclusive). If @var{low-frame} and
28678 @var{high-frame} are not provided, list the arguments for the whole
28679 call stack. If the two arguments are equal, show the single frame
28680 at the corresponding level. It is an error if @var{low-frame} is
28681 larger than the actual number of frames. On the other hand,
28682 @var{high-frame} may be larger than the actual number of frames, in
28683 which case only existing frames will be returned.
28685 If @var{print-values} is 0 or @code{--no-values}, print only the names of
28686 the variables; if it is 1 or @code{--all-values}, print also their
28687 values; and if it is 2 or @code{--simple-values}, print the name,
28688 type and value for simple data types, and the name and type for arrays,
28689 structures and unions. If the option @code{--no-frame-filters} is
28690 supplied, then Python frame filters will not be executed.
28692 If the @code{--skip-unavailable} option is specified, arguments that
28693 are not available are not listed. Partially available arguments
28694 are still displayed, however.
28696 Use of this command to obtain arguments in a single frame is
28697 deprecated in favor of the @samp{-stack-list-variables} command.
28699 @subsubheading @value{GDBN} Command
28701 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
28702 @samp{gdb_get_args} command which partially overlaps with the
28703 functionality of @samp{-stack-list-arguments}.
28705 @subsubheading Example
28712 frame=@{level="0",addr="0x00010734",func="callee4",
28713 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28714 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
28715 frame=@{level="1",addr="0x0001076c",func="callee3",
28716 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28717 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
28718 frame=@{level="2",addr="0x0001078c",func="callee2",
28719 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28720 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
28721 frame=@{level="3",addr="0x000107b4",func="callee1",
28722 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28723 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
28724 frame=@{level="4",addr="0x000107e0",func="main",
28725 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28726 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
28728 -stack-list-arguments 0
28731 frame=@{level="0",args=[]@},
28732 frame=@{level="1",args=[name="strarg"]@},
28733 frame=@{level="2",args=[name="intarg",name="strarg"]@},
28734 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
28735 frame=@{level="4",args=[]@}]
28737 -stack-list-arguments 1
28740 frame=@{level="0",args=[]@},
28742 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28743 frame=@{level="2",args=[
28744 @{name="intarg",value="2"@},
28745 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28746 @{frame=@{level="3",args=[
28747 @{name="intarg",value="2"@},
28748 @{name="strarg",value="0x11940 \"A string argument.\""@},
28749 @{name="fltarg",value="3.5"@}]@},
28750 frame=@{level="4",args=[]@}]
28752 -stack-list-arguments 0 2 2
28753 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
28755 -stack-list-arguments 1 2 2
28756 ^done,stack-args=[frame=@{level="2",
28757 args=[@{name="intarg",value="2"@},
28758 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
28762 @c @subheading -stack-list-exception-handlers
28765 @anchor{-stack-list-frames}
28766 @subheading The @code{-stack-list-frames} Command
28767 @findex -stack-list-frames
28769 @subsubheading Synopsis
28772 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
28775 List the frames currently on the stack. For each frame it displays the
28780 The frame number, 0 being the topmost frame, i.e., the innermost function.
28782 The @code{$pc} value for that frame.
28786 File name of the source file where the function lives.
28787 @item @var{fullname}
28788 The full file name of the source file where the function lives.
28790 Line number corresponding to the @code{$pc}.
28792 The shared library where this function is defined. This is only given
28793 if the frame's function is not known.
28796 If invoked without arguments, this command prints a backtrace for the
28797 whole stack. If given two integer arguments, it shows the frames whose
28798 levels are between the two arguments (inclusive). If the two arguments
28799 are equal, it shows the single frame at the corresponding level. It is
28800 an error if @var{low-frame} is larger than the actual number of
28801 frames. On the other hand, @var{high-frame} may be larger than the
28802 actual number of frames, in which case only existing frames will be
28803 returned. If the option @code{--no-frame-filters} is supplied, then
28804 Python frame filters will not be executed.
28806 @subsubheading @value{GDBN} Command
28808 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
28810 @subsubheading Example
28812 Full stack backtrace:
28818 [frame=@{level="0",addr="0x0001076c",func="foo",
28819 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
28820 frame=@{level="1",addr="0x000107a4",func="foo",
28821 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28822 frame=@{level="2",addr="0x000107a4",func="foo",
28823 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28824 frame=@{level="3",addr="0x000107a4",func="foo",
28825 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28826 frame=@{level="4",addr="0x000107a4",func="foo",
28827 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28828 frame=@{level="5",addr="0x000107a4",func="foo",
28829 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28830 frame=@{level="6",addr="0x000107a4",func="foo",
28831 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28832 frame=@{level="7",addr="0x000107a4",func="foo",
28833 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28834 frame=@{level="8",addr="0x000107a4",func="foo",
28835 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28836 frame=@{level="9",addr="0x000107a4",func="foo",
28837 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28838 frame=@{level="10",addr="0x000107a4",func="foo",
28839 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28840 frame=@{level="11",addr="0x00010738",func="main",
28841 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
28845 Show frames between @var{low_frame} and @var{high_frame}:
28849 -stack-list-frames 3 5
28851 [frame=@{level="3",addr="0x000107a4",func="foo",
28852 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28853 frame=@{level="4",addr="0x000107a4",func="foo",
28854 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28855 frame=@{level="5",addr="0x000107a4",func="foo",
28856 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28860 Show a single frame:
28864 -stack-list-frames 3 3
28866 [frame=@{level="3",addr="0x000107a4",func="foo",
28867 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28872 @subheading The @code{-stack-list-locals} Command
28873 @findex -stack-list-locals
28874 @anchor{-stack-list-locals}
28876 @subsubheading Synopsis
28879 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28882 Display the local variable names for the selected frame. If
28883 @var{print-values} is 0 or @code{--no-values}, print only the names of
28884 the variables; if it is 1 or @code{--all-values}, print also their
28885 values; and if it is 2 or @code{--simple-values}, print the name,
28886 type and value for simple data types, and the name and type for arrays,
28887 structures and unions. In this last case, a frontend can immediately
28888 display the value of simple data types and create variable objects for
28889 other data types when the user wishes to explore their values in
28890 more detail. If the option @code{--no-frame-filters} is supplied, then
28891 Python frame filters will not be executed.
28893 If the @code{--skip-unavailable} option is specified, local variables
28894 that are not available are not listed. Partially available local
28895 variables are still displayed, however.
28897 This command is deprecated in favor of the
28898 @samp{-stack-list-variables} command.
28900 @subsubheading @value{GDBN} Command
28902 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
28904 @subsubheading Example
28908 -stack-list-locals 0
28909 ^done,locals=[name="A",name="B",name="C"]
28911 -stack-list-locals --all-values
28912 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
28913 @{name="C",value="@{1, 2, 3@}"@}]
28914 -stack-list-locals --simple-values
28915 ^done,locals=[@{name="A",type="int",value="1"@},
28916 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
28920 @anchor{-stack-list-variables}
28921 @subheading The @code{-stack-list-variables} Command
28922 @findex -stack-list-variables
28924 @subsubheading Synopsis
28927 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28930 Display the names of local variables and function arguments for the selected frame. If
28931 @var{print-values} is 0 or @code{--no-values}, print only the names of
28932 the variables; if it is 1 or @code{--all-values}, print also their
28933 values; and if it is 2 or @code{--simple-values}, print the name,
28934 type and value for simple data types, and the name and type for arrays,
28935 structures and unions. If the option @code{--no-frame-filters} is
28936 supplied, then Python frame filters will not be executed.
28938 If the @code{--skip-unavailable} option is specified, local variables
28939 and arguments that are not available are not listed. Partially
28940 available arguments and local variables are still displayed, however.
28942 @subsubheading Example
28946 -stack-list-variables --thread 1 --frame 0 --all-values
28947 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
28952 @subheading The @code{-stack-select-frame} Command
28953 @findex -stack-select-frame
28955 @subsubheading Synopsis
28958 -stack-select-frame @var{framenum}
28961 Change the selected frame. Select a different frame @var{framenum} on
28964 This command in deprecated in favor of passing the @samp{--frame}
28965 option to every command.
28967 @subsubheading @value{GDBN} Command
28969 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
28970 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
28972 @subsubheading Example
28976 -stack-select-frame 2
28981 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28982 @node GDB/MI Variable Objects
28983 @section @sc{gdb/mi} Variable Objects
28987 @subheading Motivation for Variable Objects in @sc{gdb/mi}
28989 For the implementation of a variable debugger window (locals, watched
28990 expressions, etc.), we are proposing the adaptation of the existing code
28991 used by @code{Insight}.
28993 The two main reasons for that are:
28997 It has been proven in practice (it is already on its second generation).
29000 It will shorten development time (needless to say how important it is
29004 The original interface was designed to be used by Tcl code, so it was
29005 slightly changed so it could be used through @sc{gdb/mi}. This section
29006 describes the @sc{gdb/mi} operations that will be available and gives some
29007 hints about their use.
29009 @emph{Note}: In addition to the set of operations described here, we
29010 expect the @sc{gui} implementation of a variable window to require, at
29011 least, the following operations:
29014 @item @code{-gdb-show} @code{output-radix}
29015 @item @code{-stack-list-arguments}
29016 @item @code{-stack-list-locals}
29017 @item @code{-stack-select-frame}
29022 @subheading Introduction to Variable Objects
29024 @cindex variable objects in @sc{gdb/mi}
29026 Variable objects are "object-oriented" MI interface for examining and
29027 changing values of expressions. Unlike some other MI interfaces that
29028 work with expressions, variable objects are specifically designed for
29029 simple and efficient presentation in the frontend. A variable object
29030 is identified by string name. When a variable object is created, the
29031 frontend specifies the expression for that variable object. The
29032 expression can be a simple variable, or it can be an arbitrary complex
29033 expression, and can even involve CPU registers. After creating a
29034 variable object, the frontend can invoke other variable object
29035 operations---for example to obtain or change the value of a variable
29036 object, or to change display format.
29038 Variable objects have hierarchical tree structure. Any variable object
29039 that corresponds to a composite type, such as structure in C, has
29040 a number of child variable objects, for example corresponding to each
29041 element of a structure. A child variable object can itself have
29042 children, recursively. Recursion ends when we reach
29043 leaf variable objects, which always have built-in types. Child variable
29044 objects are created only by explicit request, so if a frontend
29045 is not interested in the children of a particular variable object, no
29046 child will be created.
29048 For a leaf variable object it is possible to obtain its value as a
29049 string, or set the value from a string. String value can be also
29050 obtained for a non-leaf variable object, but it's generally a string
29051 that only indicates the type of the object, and does not list its
29052 contents. Assignment to a non-leaf variable object is not allowed.
29054 A frontend does not need to read the values of all variable objects each time
29055 the program stops. Instead, MI provides an update command that lists all
29056 variable objects whose values has changed since the last update
29057 operation. This considerably reduces the amount of data that must
29058 be transferred to the frontend. As noted above, children variable
29059 objects are created on demand, and only leaf variable objects have a
29060 real value. As result, gdb will read target memory only for leaf
29061 variables that frontend has created.
29063 The automatic update is not always desirable. For example, a frontend
29064 might want to keep a value of some expression for future reference,
29065 and never update it. For another example, fetching memory is
29066 relatively slow for embedded targets, so a frontend might want
29067 to disable automatic update for the variables that are either not
29068 visible on the screen, or ``closed''. This is possible using so
29069 called ``frozen variable objects''. Such variable objects are never
29070 implicitly updated.
29072 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
29073 fixed variable object, the expression is parsed when the variable
29074 object is created, including associating identifiers to specific
29075 variables. The meaning of expression never changes. For a floating
29076 variable object the values of variables whose names appear in the
29077 expressions are re-evaluated every time in the context of the current
29078 frame. Consider this example:
29083 struct work_state state;
29090 If a fixed variable object for the @code{state} variable is created in
29091 this function, and we enter the recursive call, the variable
29092 object will report the value of @code{state} in the top-level
29093 @code{do_work} invocation. On the other hand, a floating variable
29094 object will report the value of @code{state} in the current frame.
29096 If an expression specified when creating a fixed variable object
29097 refers to a local variable, the variable object becomes bound to the
29098 thread and frame in which the variable object is created. When such
29099 variable object is updated, @value{GDBN} makes sure that the
29100 thread/frame combination the variable object is bound to still exists,
29101 and re-evaluates the variable object in context of that thread/frame.
29103 The following is the complete set of @sc{gdb/mi} operations defined to
29104 access this functionality:
29106 @multitable @columnfractions .4 .6
29107 @item @strong{Operation}
29108 @tab @strong{Description}
29110 @item @code{-enable-pretty-printing}
29111 @tab enable Python-based pretty-printing
29112 @item @code{-var-create}
29113 @tab create a variable object
29114 @item @code{-var-delete}
29115 @tab delete the variable object and/or its children
29116 @item @code{-var-set-format}
29117 @tab set the display format of this variable
29118 @item @code{-var-show-format}
29119 @tab show the display format of this variable
29120 @item @code{-var-info-num-children}
29121 @tab tells how many children this object has
29122 @item @code{-var-list-children}
29123 @tab return a list of the object's children
29124 @item @code{-var-info-type}
29125 @tab show the type of this variable object
29126 @item @code{-var-info-expression}
29127 @tab print parent-relative expression that this variable object represents
29128 @item @code{-var-info-path-expression}
29129 @tab print full expression that this variable object represents
29130 @item @code{-var-show-attributes}
29131 @tab is this variable editable? does it exist here?
29132 @item @code{-var-evaluate-expression}
29133 @tab get the value of this variable
29134 @item @code{-var-assign}
29135 @tab set the value of this variable
29136 @item @code{-var-update}
29137 @tab update the variable and its children
29138 @item @code{-var-set-frozen}
29139 @tab set frozeness attribute
29140 @item @code{-var-set-update-range}
29141 @tab set range of children to display on update
29144 In the next subsection we describe each operation in detail and suggest
29145 how it can be used.
29147 @subheading Description And Use of Operations on Variable Objects
29149 @subheading The @code{-enable-pretty-printing} Command
29150 @findex -enable-pretty-printing
29153 -enable-pretty-printing
29156 @value{GDBN} allows Python-based visualizers to affect the output of the
29157 MI variable object commands. However, because there was no way to
29158 implement this in a fully backward-compatible way, a front end must
29159 request that this functionality be enabled.
29161 Once enabled, this feature cannot be disabled.
29163 Note that if Python support has not been compiled into @value{GDBN},
29164 this command will still succeed (and do nothing).
29166 This feature is currently (as of @value{GDBN} 7.0) experimental, and
29167 may work differently in future versions of @value{GDBN}.
29169 @subheading The @code{-var-create} Command
29170 @findex -var-create
29172 @subsubheading Synopsis
29175 -var-create @{@var{name} | "-"@}
29176 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
29179 This operation creates a variable object, which allows the monitoring of
29180 a variable, the result of an expression, a memory cell or a CPU
29183 The @var{name} parameter is the string by which the object can be
29184 referenced. It must be unique. If @samp{-} is specified, the varobj
29185 system will generate a string ``varNNNNNN'' automatically. It will be
29186 unique provided that one does not specify @var{name} of that format.
29187 The command fails if a duplicate name is found.
29189 The frame under which the expression should be evaluated can be
29190 specified by @var{frame-addr}. A @samp{*} indicates that the current
29191 frame should be used. A @samp{@@} indicates that a floating variable
29192 object must be created.
29194 @var{expression} is any expression valid on the current language set (must not
29195 begin with a @samp{*}), or one of the following:
29199 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
29202 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
29205 @samp{$@var{regname}} --- a CPU register name
29208 @cindex dynamic varobj
29209 A varobj's contents may be provided by a Python-based pretty-printer. In this
29210 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
29211 have slightly different semantics in some cases. If the
29212 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
29213 will never create a dynamic varobj. This ensures backward
29214 compatibility for existing clients.
29216 @subsubheading Result
29218 This operation returns attributes of the newly-created varobj. These
29223 The name of the varobj.
29226 The number of children of the varobj. This number is not necessarily
29227 reliable for a dynamic varobj. Instead, you must examine the
29228 @samp{has_more} attribute.
29231 The varobj's scalar value. For a varobj whose type is some sort of
29232 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
29233 will not be interesting.
29236 The varobj's type. This is a string representation of the type, as
29237 would be printed by the @value{GDBN} CLI. If @samp{print object}
29238 (@pxref{Print Settings, set print object}) is set to @code{on}, the
29239 @emph{actual} (derived) type of the object is shown rather than the
29240 @emph{declared} one.
29243 If a variable object is bound to a specific thread, then this is the
29244 thread's identifier.
29247 For a dynamic varobj, this indicates whether there appear to be any
29248 children available. For a non-dynamic varobj, this will be 0.
29251 This attribute will be present and have the value @samp{1} if the
29252 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29253 then this attribute will not be present.
29256 A dynamic varobj can supply a display hint to the front end. The
29257 value comes directly from the Python pretty-printer object's
29258 @code{display_hint} method. @xref{Pretty Printing API}.
29261 Typical output will look like this:
29264 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
29265 has_more="@var{has_more}"
29269 @subheading The @code{-var-delete} Command
29270 @findex -var-delete
29272 @subsubheading Synopsis
29275 -var-delete [ -c ] @var{name}
29278 Deletes a previously created variable object and all of its children.
29279 With the @samp{-c} option, just deletes the children.
29281 Returns an error if the object @var{name} is not found.
29284 @subheading The @code{-var-set-format} Command
29285 @findex -var-set-format
29287 @subsubheading Synopsis
29290 -var-set-format @var{name} @var{format-spec}
29293 Sets the output format for the value of the object @var{name} to be
29296 @anchor{-var-set-format}
29297 The syntax for the @var{format-spec} is as follows:
29300 @var{format-spec} @expansion{}
29301 @{binary | decimal | hexadecimal | octal | natural@}
29304 The natural format is the default format choosen automatically
29305 based on the variable type (like decimal for an @code{int}, hex
29306 for pointers, etc.).
29308 For a variable with children, the format is set only on the
29309 variable itself, and the children are not affected.
29311 @subheading The @code{-var-show-format} Command
29312 @findex -var-show-format
29314 @subsubheading Synopsis
29317 -var-show-format @var{name}
29320 Returns the format used to display the value of the object @var{name}.
29323 @var{format} @expansion{}
29328 @subheading The @code{-var-info-num-children} Command
29329 @findex -var-info-num-children
29331 @subsubheading Synopsis
29334 -var-info-num-children @var{name}
29337 Returns the number of children of a variable object @var{name}:
29343 Note that this number is not completely reliable for a dynamic varobj.
29344 It will return the current number of children, but more children may
29348 @subheading The @code{-var-list-children} Command
29349 @findex -var-list-children
29351 @subsubheading Synopsis
29354 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
29356 @anchor{-var-list-children}
29358 Return a list of the children of the specified variable object and
29359 create variable objects for them, if they do not already exist. With
29360 a single argument or if @var{print-values} has a value of 0 or
29361 @code{--no-values}, print only the names of the variables; if
29362 @var{print-values} is 1 or @code{--all-values}, also print their
29363 values; and if it is 2 or @code{--simple-values} print the name and
29364 value for simple data types and just the name for arrays, structures
29367 @var{from} and @var{to}, if specified, indicate the range of children
29368 to report. If @var{from} or @var{to} is less than zero, the range is
29369 reset and all children will be reported. Otherwise, children starting
29370 at @var{from} (zero-based) and up to and excluding @var{to} will be
29373 If a child range is requested, it will only affect the current call to
29374 @code{-var-list-children}, but not future calls to @code{-var-update}.
29375 For this, you must instead use @code{-var-set-update-range}. The
29376 intent of this approach is to enable a front end to implement any
29377 update approach it likes; for example, scrolling a view may cause the
29378 front end to request more children with @code{-var-list-children}, and
29379 then the front end could call @code{-var-set-update-range} with a
29380 different range to ensure that future updates are restricted to just
29383 For each child the following results are returned:
29388 Name of the variable object created for this child.
29391 The expression to be shown to the user by the front end to designate this child.
29392 For example this may be the name of a structure member.
29394 For a dynamic varobj, this value cannot be used to form an
29395 expression. There is no way to do this at all with a dynamic varobj.
29397 For C/C@t{++} structures there are several pseudo children returned to
29398 designate access qualifiers. For these pseudo children @var{exp} is
29399 @samp{public}, @samp{private}, or @samp{protected}. In this case the
29400 type and value are not present.
29402 A dynamic varobj will not report the access qualifying
29403 pseudo-children, regardless of the language. This information is not
29404 available at all with a dynamic varobj.
29407 Number of children this child has. For a dynamic varobj, this will be
29411 The type of the child. If @samp{print object}
29412 (@pxref{Print Settings, set print object}) is set to @code{on}, the
29413 @emph{actual} (derived) type of the object is shown rather than the
29414 @emph{declared} one.
29417 If values were requested, this is the value.
29420 If this variable object is associated with a thread, this is the thread id.
29421 Otherwise this result is not present.
29424 If the variable object is frozen, this variable will be present with a value of 1.
29427 A dynamic varobj can supply a display hint to the front end. The
29428 value comes directly from the Python pretty-printer object's
29429 @code{display_hint} method. @xref{Pretty Printing API}.
29432 This attribute will be present and have the value @samp{1} if the
29433 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29434 then this attribute will not be present.
29438 The result may have its own attributes:
29442 A dynamic varobj can supply a display hint to the front end. The
29443 value comes directly from the Python pretty-printer object's
29444 @code{display_hint} method. @xref{Pretty Printing API}.
29447 This is an integer attribute which is nonzero if there are children
29448 remaining after the end of the selected range.
29451 @subsubheading Example
29455 -var-list-children n
29456 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29457 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
29459 -var-list-children --all-values n
29460 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29461 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
29465 @subheading The @code{-var-info-type} Command
29466 @findex -var-info-type
29468 @subsubheading Synopsis
29471 -var-info-type @var{name}
29474 Returns the type of the specified variable @var{name}. The type is
29475 returned as a string in the same format as it is output by the
29479 type=@var{typename}
29483 @subheading The @code{-var-info-expression} Command
29484 @findex -var-info-expression
29486 @subsubheading Synopsis
29489 -var-info-expression @var{name}
29492 Returns a string that is suitable for presenting this
29493 variable object in user interface. The string is generally
29494 not valid expression in the current language, and cannot be evaluated.
29496 For example, if @code{a} is an array, and variable object
29497 @code{A} was created for @code{a}, then we'll get this output:
29500 (gdb) -var-info-expression A.1
29501 ^done,lang="C",exp="1"
29505 Here, the value of @code{lang} is the language name, which can be
29506 found in @ref{Supported Languages}.
29508 Note that the output of the @code{-var-list-children} command also
29509 includes those expressions, so the @code{-var-info-expression} command
29512 @subheading The @code{-var-info-path-expression} Command
29513 @findex -var-info-path-expression
29515 @subsubheading Synopsis
29518 -var-info-path-expression @var{name}
29521 Returns an expression that can be evaluated in the current
29522 context and will yield the same value that a variable object has.
29523 Compare this with the @code{-var-info-expression} command, which
29524 result can be used only for UI presentation. Typical use of
29525 the @code{-var-info-path-expression} command is creating a
29526 watchpoint from a variable object.
29528 This command is currently not valid for children of a dynamic varobj,
29529 and will give an error when invoked on one.
29531 For example, suppose @code{C} is a C@t{++} class, derived from class
29532 @code{Base}, and that the @code{Base} class has a member called
29533 @code{m_size}. Assume a variable @code{c} is has the type of
29534 @code{C} and a variable object @code{C} was created for variable
29535 @code{c}. Then, we'll get this output:
29537 (gdb) -var-info-path-expression C.Base.public.m_size
29538 ^done,path_expr=((Base)c).m_size)
29541 @subheading The @code{-var-show-attributes} Command
29542 @findex -var-show-attributes
29544 @subsubheading Synopsis
29547 -var-show-attributes @var{name}
29550 List attributes of the specified variable object @var{name}:
29553 status=@var{attr} [ ( ,@var{attr} )* ]
29557 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
29559 @subheading The @code{-var-evaluate-expression} Command
29560 @findex -var-evaluate-expression
29562 @subsubheading Synopsis
29565 -var-evaluate-expression [-f @var{format-spec}] @var{name}
29568 Evaluates the expression that is represented by the specified variable
29569 object and returns its value as a string. The format of the string
29570 can be specified with the @samp{-f} option. The possible values of
29571 this option are the same as for @code{-var-set-format}
29572 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
29573 the current display format will be used. The current display format
29574 can be changed using the @code{-var-set-format} command.
29580 Note that one must invoke @code{-var-list-children} for a variable
29581 before the value of a child variable can be evaluated.
29583 @subheading The @code{-var-assign} Command
29584 @findex -var-assign
29586 @subsubheading Synopsis
29589 -var-assign @var{name} @var{expression}
29592 Assigns the value of @var{expression} to the variable object specified
29593 by @var{name}. The object must be @samp{editable}. If the variable's
29594 value is altered by the assign, the variable will show up in any
29595 subsequent @code{-var-update} list.
29597 @subsubheading Example
29605 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
29609 @subheading The @code{-var-update} Command
29610 @findex -var-update
29612 @subsubheading Synopsis
29615 -var-update [@var{print-values}] @{@var{name} | "*"@}
29618 Reevaluate the expressions corresponding to the variable object
29619 @var{name} and all its direct and indirect children, and return the
29620 list of variable objects whose values have changed; @var{name} must
29621 be a root variable object. Here, ``changed'' means that the result of
29622 @code{-var-evaluate-expression} before and after the
29623 @code{-var-update} is different. If @samp{*} is used as the variable
29624 object names, all existing variable objects are updated, except
29625 for frozen ones (@pxref{-var-set-frozen}). The option
29626 @var{print-values} determines whether both names and values, or just
29627 names are printed. The possible values of this option are the same
29628 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
29629 recommended to use the @samp{--all-values} option, to reduce the
29630 number of MI commands needed on each program stop.
29632 With the @samp{*} parameter, if a variable object is bound to a
29633 currently running thread, it will not be updated, without any
29636 If @code{-var-set-update-range} was previously used on a varobj, then
29637 only the selected range of children will be reported.
29639 @code{-var-update} reports all the changed varobjs in a tuple named
29642 Each item in the change list is itself a tuple holding:
29646 The name of the varobj.
29649 If values were requested for this update, then this field will be
29650 present and will hold the value of the varobj.
29653 @anchor{-var-update}
29654 This field is a string which may take one of three values:
29658 The variable object's current value is valid.
29661 The variable object does not currently hold a valid value but it may
29662 hold one in the future if its associated expression comes back into
29666 The variable object no longer holds a valid value.
29667 This can occur when the executable file being debugged has changed,
29668 either through recompilation or by using the @value{GDBN} @code{file}
29669 command. The front end should normally choose to delete these variable
29673 In the future new values may be added to this list so the front should
29674 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
29677 This is only present if the varobj is still valid. If the type
29678 changed, then this will be the string @samp{true}; otherwise it will
29681 When a varobj's type changes, its children are also likely to have
29682 become incorrect. Therefore, the varobj's children are automatically
29683 deleted when this attribute is @samp{true}. Also, the varobj's update
29684 range, when set using the @code{-var-set-update-range} command, is
29688 If the varobj's type changed, then this field will be present and will
29691 @item new_num_children
29692 For a dynamic varobj, if the number of children changed, or if the
29693 type changed, this will be the new number of children.
29695 The @samp{numchild} field in other varobj responses is generally not
29696 valid for a dynamic varobj -- it will show the number of children that
29697 @value{GDBN} knows about, but because dynamic varobjs lazily
29698 instantiate their children, this will not reflect the number of
29699 children which may be available.
29701 The @samp{new_num_children} attribute only reports changes to the
29702 number of children known by @value{GDBN}. This is the only way to
29703 detect whether an update has removed children (which necessarily can
29704 only happen at the end of the update range).
29707 The display hint, if any.
29710 This is an integer value, which will be 1 if there are more children
29711 available outside the varobj's update range.
29714 This attribute will be present and have the value @samp{1} if the
29715 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29716 then this attribute will not be present.
29719 If new children were added to a dynamic varobj within the selected
29720 update range (as set by @code{-var-set-update-range}), then they will
29721 be listed in this attribute.
29724 @subsubheading Example
29731 -var-update --all-values var1
29732 ^done,changelist=[@{name="var1",value="3",in_scope="true",
29733 type_changed="false"@}]
29737 @subheading The @code{-var-set-frozen} Command
29738 @findex -var-set-frozen
29739 @anchor{-var-set-frozen}
29741 @subsubheading Synopsis
29744 -var-set-frozen @var{name} @var{flag}
29747 Set the frozenness flag on the variable object @var{name}. The
29748 @var{flag} parameter should be either @samp{1} to make the variable
29749 frozen or @samp{0} to make it unfrozen. If a variable object is
29750 frozen, then neither itself, nor any of its children, are
29751 implicitly updated by @code{-var-update} of
29752 a parent variable or by @code{-var-update *}. Only
29753 @code{-var-update} of the variable itself will update its value and
29754 values of its children. After a variable object is unfrozen, it is
29755 implicitly updated by all subsequent @code{-var-update} operations.
29756 Unfreezing a variable does not update it, only subsequent
29757 @code{-var-update} does.
29759 @subsubheading Example
29763 -var-set-frozen V 1
29768 @subheading The @code{-var-set-update-range} command
29769 @findex -var-set-update-range
29770 @anchor{-var-set-update-range}
29772 @subsubheading Synopsis
29775 -var-set-update-range @var{name} @var{from} @var{to}
29778 Set the range of children to be returned by future invocations of
29779 @code{-var-update}.
29781 @var{from} and @var{to} indicate the range of children to report. If
29782 @var{from} or @var{to} is less than zero, the range is reset and all
29783 children will be reported. Otherwise, children starting at @var{from}
29784 (zero-based) and up to and excluding @var{to} will be reported.
29786 @subsubheading Example
29790 -var-set-update-range V 1 2
29794 @subheading The @code{-var-set-visualizer} command
29795 @findex -var-set-visualizer
29796 @anchor{-var-set-visualizer}
29798 @subsubheading Synopsis
29801 -var-set-visualizer @var{name} @var{visualizer}
29804 Set a visualizer for the variable object @var{name}.
29806 @var{visualizer} is the visualizer to use. The special value
29807 @samp{None} means to disable any visualizer in use.
29809 If not @samp{None}, @var{visualizer} must be a Python expression.
29810 This expression must evaluate to a callable object which accepts a
29811 single argument. @value{GDBN} will call this object with the value of
29812 the varobj @var{name} as an argument (this is done so that the same
29813 Python pretty-printing code can be used for both the CLI and MI).
29814 When called, this object must return an object which conforms to the
29815 pretty-printing interface (@pxref{Pretty Printing API}).
29817 The pre-defined function @code{gdb.default_visualizer} may be used to
29818 select a visualizer by following the built-in process
29819 (@pxref{Selecting Pretty-Printers}). This is done automatically when
29820 a varobj is created, and so ordinarily is not needed.
29822 This feature is only available if Python support is enabled. The MI
29823 command @code{-list-features} (@pxref{GDB/MI Support Commands})
29824 can be used to check this.
29826 @subsubheading Example
29828 Resetting the visualizer:
29832 -var-set-visualizer V None
29836 Reselecting the default (type-based) visualizer:
29840 -var-set-visualizer V gdb.default_visualizer
29844 Suppose @code{SomeClass} is a visualizer class. A lambda expression
29845 can be used to instantiate this class for a varobj:
29849 -var-set-visualizer V "lambda val: SomeClass()"
29853 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29854 @node GDB/MI Data Manipulation
29855 @section @sc{gdb/mi} Data Manipulation
29857 @cindex data manipulation, in @sc{gdb/mi}
29858 @cindex @sc{gdb/mi}, data manipulation
29859 This section describes the @sc{gdb/mi} commands that manipulate data:
29860 examine memory and registers, evaluate expressions, etc.
29862 For details about what an addressable memory unit is,
29863 @pxref{addressable memory unit}.
29865 @c REMOVED FROM THE INTERFACE.
29866 @c @subheading -data-assign
29867 @c Change the value of a program variable. Plenty of side effects.
29868 @c @subsubheading GDB Command
29870 @c @subsubheading Example
29873 @subheading The @code{-data-disassemble} Command
29874 @findex -data-disassemble
29876 @subsubheading Synopsis
29880 [ -s @var{start-addr} -e @var{end-addr} ]
29881 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
29889 @item @var{start-addr}
29890 is the beginning address (or @code{$pc})
29891 @item @var{end-addr}
29893 @item @var{filename}
29894 is the name of the file to disassemble
29895 @item @var{linenum}
29896 is the line number to disassemble around
29898 is the number of disassembly lines to be produced. If it is -1,
29899 the whole function will be disassembled, in case no @var{end-addr} is
29900 specified. If @var{end-addr} is specified as a non-zero value, and
29901 @var{lines} is lower than the number of disassembly lines between
29902 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
29903 displayed; if @var{lines} is higher than the number of lines between
29904 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
29909 @item 0 disassembly only
29910 @item 1 mixed source and disassembly (deprecated)
29911 @item 2 disassembly with raw opcodes
29912 @item 3 mixed source and disassembly with raw opcodes (deprecated)
29913 @item 4 mixed source and disassembly
29914 @item 5 mixed source and disassembly with raw opcodes
29917 Modes 1 and 3 are deprecated. The output is ``source centric''
29918 which hasn't proved useful in practice.
29919 @xref{Machine Code}, for a discussion of the difference between
29920 @code{/m} and @code{/s} output of the @code{disassemble} command.
29923 @subsubheading Result
29925 The result of the @code{-data-disassemble} command will be a list named
29926 @samp{asm_insns}, the contents of this list depend on the @var{mode}
29927 used with the @code{-data-disassemble} command.
29929 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
29934 The address at which this instruction was disassembled.
29937 The name of the function this instruction is within.
29940 The decimal offset in bytes from the start of @samp{func-name}.
29943 The text disassembly for this @samp{address}.
29946 This field is only present for modes 2, 3 and 5. This contains the raw opcode
29947 bytes for the @samp{inst} field.
29951 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
29952 @samp{src_and_asm_line}, each of which has the following fields:
29956 The line number within @samp{file}.
29959 The file name from the compilation unit. This might be an absolute
29960 file name or a relative file name depending on the compile command
29964 Absolute file name of @samp{file}. It is converted to a canonical form
29965 using the source file search path
29966 (@pxref{Source Path, ,Specifying Source Directories})
29967 and after resolving all the symbolic links.
29969 If the source file is not found this field will contain the path as
29970 present in the debug information.
29972 @item line_asm_insn
29973 This is a list of tuples containing the disassembly for @samp{line} in
29974 @samp{file}. The fields of each tuple are the same as for
29975 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
29976 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
29981 Note that whatever included in the @samp{inst} field, is not
29982 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
29985 @subsubheading @value{GDBN} Command
29987 The corresponding @value{GDBN} command is @samp{disassemble}.
29989 @subsubheading Example
29991 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
29995 -data-disassemble -s $pc -e "$pc + 20" -- 0
29998 @{address="0x000107c0",func-name="main",offset="4",
29999 inst="mov 2, %o0"@},
30000 @{address="0x000107c4",func-name="main",offset="8",
30001 inst="sethi %hi(0x11800), %o2"@},
30002 @{address="0x000107c8",func-name="main",offset="12",
30003 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
30004 @{address="0x000107cc",func-name="main",offset="16",
30005 inst="sethi %hi(0x11800), %o2"@},
30006 @{address="0x000107d0",func-name="main",offset="20",
30007 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
30011 Disassemble the whole @code{main} function. Line 32 is part of
30015 -data-disassemble -f basics.c -l 32 -- 0
30017 @{address="0x000107bc",func-name="main",offset="0",
30018 inst="save %sp, -112, %sp"@},
30019 @{address="0x000107c0",func-name="main",offset="4",
30020 inst="mov 2, %o0"@},
30021 @{address="0x000107c4",func-name="main",offset="8",
30022 inst="sethi %hi(0x11800), %o2"@},
30024 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
30025 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
30029 Disassemble 3 instructions from the start of @code{main}:
30033 -data-disassemble -f basics.c -l 32 -n 3 -- 0
30035 @{address="0x000107bc",func-name="main",offset="0",
30036 inst="save %sp, -112, %sp"@},
30037 @{address="0x000107c0",func-name="main",offset="4",
30038 inst="mov 2, %o0"@},
30039 @{address="0x000107c4",func-name="main",offset="8",
30040 inst="sethi %hi(0x11800), %o2"@}]
30044 Disassemble 3 instructions from the start of @code{main} in mixed mode:
30048 -data-disassemble -f basics.c -l 32 -n 3 -- 1
30050 src_and_asm_line=@{line="31",
30051 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
30052 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
30053 line_asm_insn=[@{address="0x000107bc",
30054 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
30055 src_and_asm_line=@{line="32",
30056 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
30057 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
30058 line_asm_insn=[@{address="0x000107c0",
30059 func-name="main",offset="4",inst="mov 2, %o0"@},
30060 @{address="0x000107c4",func-name="main",offset="8",
30061 inst="sethi %hi(0x11800), %o2"@}]@}]
30066 @subheading The @code{-data-evaluate-expression} Command
30067 @findex -data-evaluate-expression
30069 @subsubheading Synopsis
30072 -data-evaluate-expression @var{expr}
30075 Evaluate @var{expr} as an expression. The expression could contain an
30076 inferior function call. The function call will execute synchronously.
30077 If the expression contains spaces, it must be enclosed in double quotes.
30079 @subsubheading @value{GDBN} Command
30081 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
30082 @samp{call}. In @code{gdbtk} only, there's a corresponding
30083 @samp{gdb_eval} command.
30085 @subsubheading Example
30087 In the following example, the numbers that precede the commands are the
30088 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
30089 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
30093 211-data-evaluate-expression A
30096 311-data-evaluate-expression &A
30097 311^done,value="0xefffeb7c"
30099 411-data-evaluate-expression A+3
30102 511-data-evaluate-expression "A + 3"
30108 @subheading The @code{-data-list-changed-registers} Command
30109 @findex -data-list-changed-registers
30111 @subsubheading Synopsis
30114 -data-list-changed-registers
30117 Display a list of the registers that have changed.
30119 @subsubheading @value{GDBN} Command
30121 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
30122 has the corresponding command @samp{gdb_changed_register_list}.
30124 @subsubheading Example
30126 On a PPC MBX board:
30134 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
30135 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
30138 -data-list-changed-registers
30139 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
30140 "10","11","13","14","15","16","17","18","19","20","21","22","23",
30141 "24","25","26","27","28","30","31","64","65","66","67","69"]
30146 @subheading The @code{-data-list-register-names} Command
30147 @findex -data-list-register-names
30149 @subsubheading Synopsis
30152 -data-list-register-names [ ( @var{regno} )+ ]
30155 Show a list of register names for the current target. If no arguments
30156 are given, it shows a list of the names of all the registers. If
30157 integer numbers are given as arguments, it will print a list of the
30158 names of the registers corresponding to the arguments. To ensure
30159 consistency between a register name and its number, the output list may
30160 include empty register names.
30162 @subsubheading @value{GDBN} Command
30164 @value{GDBN} does not have a command which corresponds to
30165 @samp{-data-list-register-names}. In @code{gdbtk} there is a
30166 corresponding command @samp{gdb_regnames}.
30168 @subsubheading Example
30170 For the PPC MBX board:
30173 -data-list-register-names
30174 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
30175 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
30176 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
30177 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
30178 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
30179 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
30180 "", "pc","ps","cr","lr","ctr","xer"]
30182 -data-list-register-names 1 2 3
30183 ^done,register-names=["r1","r2","r3"]
30187 @subheading The @code{-data-list-register-values} Command
30188 @findex -data-list-register-values
30190 @subsubheading Synopsis
30193 -data-list-register-values
30194 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
30197 Display the registers' contents. The format according to which the
30198 registers' contents are to be returned is given by @var{fmt}, followed
30199 by an optional list of numbers specifying the registers to display. A
30200 missing list of numbers indicates that the contents of all the
30201 registers must be returned. The @code{--skip-unavailable} option
30202 indicates that only the available registers are to be returned.
30204 Allowed formats for @var{fmt} are:
30221 @subsubheading @value{GDBN} Command
30223 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
30224 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
30226 @subsubheading Example
30228 For a PPC MBX board (note: line breaks are for readability only, they
30229 don't appear in the actual output):
30233 -data-list-register-values r 64 65
30234 ^done,register-values=[@{number="64",value="0xfe00a300"@},
30235 @{number="65",value="0x00029002"@}]
30237 -data-list-register-values x
30238 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
30239 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
30240 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
30241 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
30242 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
30243 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
30244 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
30245 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
30246 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
30247 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
30248 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
30249 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
30250 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
30251 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
30252 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
30253 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
30254 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
30255 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
30256 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
30257 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
30258 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
30259 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
30260 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
30261 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
30262 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
30263 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
30264 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
30265 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
30266 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
30267 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
30268 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
30269 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
30270 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
30271 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
30272 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
30273 @{number="69",value="0x20002b03"@}]
30278 @subheading The @code{-data-read-memory} Command
30279 @findex -data-read-memory
30281 This command is deprecated, use @code{-data-read-memory-bytes} instead.
30283 @subsubheading Synopsis
30286 -data-read-memory [ -o @var{byte-offset} ]
30287 @var{address} @var{word-format} @var{word-size}
30288 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
30295 @item @var{address}
30296 An expression specifying the address of the first memory word to be
30297 read. Complex expressions containing embedded white space should be
30298 quoted using the C convention.
30300 @item @var{word-format}
30301 The format to be used to print the memory words. The notation is the
30302 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
30305 @item @var{word-size}
30306 The size of each memory word in bytes.
30308 @item @var{nr-rows}
30309 The number of rows in the output table.
30311 @item @var{nr-cols}
30312 The number of columns in the output table.
30315 If present, indicates that each row should include an @sc{ascii} dump. The
30316 value of @var{aschar} is used as a padding character when a byte is not a
30317 member of the printable @sc{ascii} character set (printable @sc{ascii}
30318 characters are those whose code is between 32 and 126, inclusively).
30320 @item @var{byte-offset}
30321 An offset to add to the @var{address} before fetching memory.
30324 This command displays memory contents as a table of @var{nr-rows} by
30325 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
30326 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
30327 (returned as @samp{total-bytes}). Should less than the requested number
30328 of bytes be returned by the target, the missing words are identified
30329 using @samp{N/A}. The number of bytes read from the target is returned
30330 in @samp{nr-bytes} and the starting address used to read memory in
30333 The address of the next/previous row or page is available in
30334 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
30337 @subsubheading @value{GDBN} Command
30339 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
30340 @samp{gdb_get_mem} memory read command.
30342 @subsubheading Example
30344 Read six bytes of memory starting at @code{bytes+6} but then offset by
30345 @code{-6} bytes. Format as three rows of two columns. One byte per
30346 word. Display each word in hex.
30350 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
30351 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
30352 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
30353 prev-page="0x0000138a",memory=[
30354 @{addr="0x00001390",data=["0x00","0x01"]@},
30355 @{addr="0x00001392",data=["0x02","0x03"]@},
30356 @{addr="0x00001394",data=["0x04","0x05"]@}]
30360 Read two bytes of memory starting at address @code{shorts + 64} and
30361 display as a single word formatted in decimal.
30365 5-data-read-memory shorts+64 d 2 1 1
30366 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
30367 next-row="0x00001512",prev-row="0x0000150e",
30368 next-page="0x00001512",prev-page="0x0000150e",memory=[
30369 @{addr="0x00001510",data=["128"]@}]
30373 Read thirty two bytes of memory starting at @code{bytes+16} and format
30374 as eight rows of four columns. Include a string encoding with @samp{x}
30375 used as the non-printable character.
30379 4-data-read-memory bytes+16 x 1 8 4 x
30380 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
30381 next-row="0x000013c0",prev-row="0x0000139c",
30382 next-page="0x000013c0",prev-page="0x00001380",memory=[
30383 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
30384 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
30385 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
30386 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
30387 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
30388 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
30389 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
30390 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
30394 @subheading The @code{-data-read-memory-bytes} Command
30395 @findex -data-read-memory-bytes
30397 @subsubheading Synopsis
30400 -data-read-memory-bytes [ -o @var{offset} ]
30401 @var{address} @var{count}
30408 @item @var{address}
30409 An expression specifying the address of the first addressable memory unit
30410 to be read. Complex expressions containing embedded white space should be
30411 quoted using the C convention.
30414 The number of addressable memory units to read. This should be an integer
30418 The offset relative to @var{address} at which to start reading. This
30419 should be an integer literal. This option is provided so that a frontend
30420 is not required to first evaluate address and then perform address
30421 arithmetics itself.
30425 This command attempts to read all accessible memory regions in the
30426 specified range. First, all regions marked as unreadable in the memory
30427 map (if one is defined) will be skipped. @xref{Memory Region
30428 Attributes}. Second, @value{GDBN} will attempt to read the remaining
30429 regions. For each one, if reading full region results in an errors,
30430 @value{GDBN} will try to read a subset of the region.
30432 In general, every single memory unit in the region may be readable or not,
30433 and the only way to read every readable unit is to try a read at
30434 every address, which is not practical. Therefore, @value{GDBN} will
30435 attempt to read all accessible memory units at either beginning or the end
30436 of the region, using a binary division scheme. This heuristic works
30437 well for reading accross a memory map boundary. Note that if a region
30438 has a readable range that is neither at the beginning or the end,
30439 @value{GDBN} will not read it.
30441 The result record (@pxref{GDB/MI Result Records}) that is output of
30442 the command includes a field named @samp{memory} whose content is a
30443 list of tuples. Each tuple represent a successfully read memory block
30444 and has the following fields:
30448 The start address of the memory block, as hexadecimal literal.
30451 The end address of the memory block, as hexadecimal literal.
30454 The offset of the memory block, as hexadecimal literal, relative to
30455 the start address passed to @code{-data-read-memory-bytes}.
30458 The contents of the memory block, in hex.
30464 @subsubheading @value{GDBN} Command
30466 The corresponding @value{GDBN} command is @samp{x}.
30468 @subsubheading Example
30472 -data-read-memory-bytes &a 10
30473 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
30475 contents="01000000020000000300"@}]
30480 @subheading The @code{-data-write-memory-bytes} Command
30481 @findex -data-write-memory-bytes
30483 @subsubheading Synopsis
30486 -data-write-memory-bytes @var{address} @var{contents}
30487 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
30494 @item @var{address}
30495 An expression specifying the address of the first addressable memory unit
30496 to be written. Complex expressions containing embedded white space should
30497 be quoted using the C convention.
30499 @item @var{contents}
30500 The hex-encoded data to write. It is an error if @var{contents} does
30501 not represent an integral number of addressable memory units.
30504 Optional argument indicating the number of addressable memory units to be
30505 written. If @var{count} is greater than @var{contents}' length,
30506 @value{GDBN} will repeatedly write @var{contents} until it fills
30507 @var{count} memory units.
30511 @subsubheading @value{GDBN} Command
30513 There's no corresponding @value{GDBN} command.
30515 @subsubheading Example
30519 -data-write-memory-bytes &a "aabbccdd"
30526 -data-write-memory-bytes &a "aabbccdd" 16e
30531 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30532 @node GDB/MI Tracepoint Commands
30533 @section @sc{gdb/mi} Tracepoint Commands
30535 The commands defined in this section implement MI support for
30536 tracepoints. For detailed introduction, see @ref{Tracepoints}.
30538 @subheading The @code{-trace-find} Command
30539 @findex -trace-find
30541 @subsubheading Synopsis
30544 -trace-find @var{mode} [@var{parameters}@dots{}]
30547 Find a trace frame using criteria defined by @var{mode} and
30548 @var{parameters}. The following table lists permissible
30549 modes and their parameters. For details of operation, see @ref{tfind}.
30554 No parameters are required. Stops examining trace frames.
30557 An integer is required as parameter. Selects tracepoint frame with
30560 @item tracepoint-number
30561 An integer is required as parameter. Finds next
30562 trace frame that corresponds to tracepoint with the specified number.
30565 An address is required as parameter. Finds
30566 next trace frame that corresponds to any tracepoint at the specified
30569 @item pc-inside-range
30570 Two addresses are required as parameters. Finds next trace
30571 frame that corresponds to a tracepoint at an address inside the
30572 specified range. Both bounds are considered to be inside the range.
30574 @item pc-outside-range
30575 Two addresses are required as parameters. Finds
30576 next trace frame that corresponds to a tracepoint at an address outside
30577 the specified range. Both bounds are considered to be inside the range.
30580 Line specification is required as parameter. @xref{Specify Location}.
30581 Finds next trace frame that corresponds to a tracepoint at
30582 the specified location.
30586 If @samp{none} was passed as @var{mode}, the response does not
30587 have fields. Otherwise, the response may have the following fields:
30591 This field has either @samp{0} or @samp{1} as the value, depending
30592 on whether a matching tracepoint was found.
30595 The index of the found traceframe. This field is present iff
30596 the @samp{found} field has value of @samp{1}.
30599 The index of the found tracepoint. This field is present iff
30600 the @samp{found} field has value of @samp{1}.
30603 The information about the frame corresponding to the found trace
30604 frame. This field is present only if a trace frame was found.
30605 @xref{GDB/MI Frame Information}, for description of this field.
30609 @subsubheading @value{GDBN} Command
30611 The corresponding @value{GDBN} command is @samp{tfind}.
30613 @subheading -trace-define-variable
30614 @findex -trace-define-variable
30616 @subsubheading Synopsis
30619 -trace-define-variable @var{name} [ @var{value} ]
30622 Create trace variable @var{name} if it does not exist. If
30623 @var{value} is specified, sets the initial value of the specified
30624 trace variable to that value. Note that the @var{name} should start
30625 with the @samp{$} character.
30627 @subsubheading @value{GDBN} Command
30629 The corresponding @value{GDBN} command is @samp{tvariable}.
30631 @subheading The @code{-trace-frame-collected} Command
30632 @findex -trace-frame-collected
30634 @subsubheading Synopsis
30637 -trace-frame-collected
30638 [--var-print-values @var{var_pval}]
30639 [--comp-print-values @var{comp_pval}]
30640 [--registers-format @var{regformat}]
30641 [--memory-contents]
30644 This command returns the set of collected objects, register names,
30645 trace state variable names, memory ranges and computed expressions
30646 that have been collected at a particular trace frame. The optional
30647 parameters to the command affect the output format in different ways.
30648 See the output description table below for more details.
30650 The reported names can be used in the normal manner to create
30651 varobjs and inspect the objects themselves. The items returned by
30652 this command are categorized so that it is clear which is a variable,
30653 which is a register, which is a trace state variable, which is a
30654 memory range and which is a computed expression.
30656 For instance, if the actions were
30658 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
30659 collect *(int*)0xaf02bef0@@40
30663 the object collected in its entirety would be @code{myVar}. The
30664 object @code{myArray} would be partially collected, because only the
30665 element at index @code{myIndex} would be collected. The remaining
30666 objects would be computed expressions.
30668 An example output would be:
30672 -trace-frame-collected
30674 explicit-variables=[@{name="myVar",value="1"@}],
30675 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
30676 @{name="myObj.field",value="0"@},
30677 @{name="myPtr->field",value="1"@},
30678 @{name="myCount + 2",value="3"@},
30679 @{name="$tvar1 + 1",value="43970027"@}],
30680 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
30681 @{number="1",value="0x0"@},
30682 @{number="2",value="0x4"@},
30684 @{number="125",value="0x0"@}],
30685 tvars=[@{name="$tvar1",current="43970026"@}],
30686 memory=[@{address="0x0000000000602264",length="4"@},
30687 @{address="0x0000000000615bc0",length="4"@}]
30694 @item explicit-variables
30695 The set of objects that have been collected in their entirety (as
30696 opposed to collecting just a few elements of an array or a few struct
30697 members). For each object, its name and value are printed.
30698 The @code{--var-print-values} option affects how or whether the value
30699 field is output. If @var{var_pval} is 0, then print only the names;
30700 if it is 1, print also their values; and if it is 2, print the name,
30701 type and value for simple data types, and the name and type for
30702 arrays, structures and unions.
30704 @item computed-expressions
30705 The set of computed expressions that have been collected at the
30706 current trace frame. The @code{--comp-print-values} option affects
30707 this set like the @code{--var-print-values} option affects the
30708 @code{explicit-variables} set. See above.
30711 The registers that have been collected at the current trace frame.
30712 For each register collected, the name and current value are returned.
30713 The value is formatted according to the @code{--registers-format}
30714 option. See the @command{-data-list-register-values} command for a
30715 list of the allowed formats. The default is @samp{x}.
30718 The trace state variables that have been collected at the current
30719 trace frame. For each trace state variable collected, the name and
30720 current value are returned.
30723 The set of memory ranges that have been collected at the current trace
30724 frame. Its content is a list of tuples. Each tuple represents a
30725 collected memory range and has the following fields:
30729 The start address of the memory range, as hexadecimal literal.
30732 The length of the memory range, as decimal literal.
30735 The contents of the memory block, in hex. This field is only present
30736 if the @code{--memory-contents} option is specified.
30742 @subsubheading @value{GDBN} Command
30744 There is no corresponding @value{GDBN} command.
30746 @subsubheading Example
30748 @subheading -trace-list-variables
30749 @findex -trace-list-variables
30751 @subsubheading Synopsis
30754 -trace-list-variables
30757 Return a table of all defined trace variables. Each element of the
30758 table has the following fields:
30762 The name of the trace variable. This field is always present.
30765 The initial value. This is a 64-bit signed integer. This
30766 field is always present.
30769 The value the trace variable has at the moment. This is a 64-bit
30770 signed integer. This field is absent iff current value is
30771 not defined, for example if the trace was never run, or is
30776 @subsubheading @value{GDBN} Command
30778 The corresponding @value{GDBN} command is @samp{tvariables}.
30780 @subsubheading Example
30784 -trace-list-variables
30785 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
30786 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
30787 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
30788 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
30789 body=[variable=@{name="$trace_timestamp",initial="0"@}
30790 variable=@{name="$foo",initial="10",current="15"@}]@}
30794 @subheading -trace-save
30795 @findex -trace-save
30797 @subsubheading Synopsis
30800 -trace-save [-r ] @var{filename}
30803 Saves the collected trace data to @var{filename}. Without the
30804 @samp{-r} option, the data is downloaded from the target and saved
30805 in a local file. With the @samp{-r} option the target is asked
30806 to perform the save.
30808 @subsubheading @value{GDBN} Command
30810 The corresponding @value{GDBN} command is @samp{tsave}.
30813 @subheading -trace-start
30814 @findex -trace-start
30816 @subsubheading Synopsis
30822 Starts a tracing experiments. The result of this command does not
30825 @subsubheading @value{GDBN} Command
30827 The corresponding @value{GDBN} command is @samp{tstart}.
30829 @subheading -trace-status
30830 @findex -trace-status
30832 @subsubheading Synopsis
30838 Obtains the status of a tracing experiment. The result may include
30839 the following fields:
30844 May have a value of either @samp{0}, when no tracing operations are
30845 supported, @samp{1}, when all tracing operations are supported, or
30846 @samp{file} when examining trace file. In the latter case, examining
30847 of trace frame is possible but new tracing experiement cannot be
30848 started. This field is always present.
30851 May have a value of either @samp{0} or @samp{1} depending on whether
30852 tracing experiement is in progress on target. This field is present
30853 if @samp{supported} field is not @samp{0}.
30856 Report the reason why the tracing was stopped last time. This field
30857 may be absent iff tracing was never stopped on target yet. The
30858 value of @samp{request} means the tracing was stopped as result of
30859 the @code{-trace-stop} command. The value of @samp{overflow} means
30860 the tracing buffer is full. The value of @samp{disconnection} means
30861 tracing was automatically stopped when @value{GDBN} has disconnected.
30862 The value of @samp{passcount} means tracing was stopped when a
30863 tracepoint was passed a maximal number of times for that tracepoint.
30864 This field is present if @samp{supported} field is not @samp{0}.
30866 @item stopping-tracepoint
30867 The number of tracepoint whose passcount as exceeded. This field is
30868 present iff the @samp{stop-reason} field has the value of
30872 @itemx frames-created
30873 The @samp{frames} field is a count of the total number of trace frames
30874 in the trace buffer, while @samp{frames-created} is the total created
30875 during the run, including ones that were discarded, such as when a
30876 circular trace buffer filled up. Both fields are optional.
30880 These fields tell the current size of the tracing buffer and the
30881 remaining space. These fields are optional.
30884 The value of the circular trace buffer flag. @code{1} means that the
30885 trace buffer is circular and old trace frames will be discarded if
30886 necessary to make room, @code{0} means that the trace buffer is linear
30890 The value of the disconnected tracing flag. @code{1} means that
30891 tracing will continue after @value{GDBN} disconnects, @code{0} means
30892 that the trace run will stop.
30895 The filename of the trace file being examined. This field is
30896 optional, and only present when examining a trace file.
30900 @subsubheading @value{GDBN} Command
30902 The corresponding @value{GDBN} command is @samp{tstatus}.
30904 @subheading -trace-stop
30905 @findex -trace-stop
30907 @subsubheading Synopsis
30913 Stops a tracing experiment. The result of this command has the same
30914 fields as @code{-trace-status}, except that the @samp{supported} and
30915 @samp{running} fields are not output.
30917 @subsubheading @value{GDBN} Command
30919 The corresponding @value{GDBN} command is @samp{tstop}.
30922 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30923 @node GDB/MI Symbol Query
30924 @section @sc{gdb/mi} Symbol Query Commands
30928 @subheading The @code{-symbol-info-address} Command
30929 @findex -symbol-info-address
30931 @subsubheading Synopsis
30934 -symbol-info-address @var{symbol}
30937 Describe where @var{symbol} is stored.
30939 @subsubheading @value{GDBN} Command
30941 The corresponding @value{GDBN} command is @samp{info address}.
30943 @subsubheading Example
30947 @subheading The @code{-symbol-info-file} Command
30948 @findex -symbol-info-file
30950 @subsubheading Synopsis
30956 Show the file for the symbol.
30958 @subsubheading @value{GDBN} Command
30960 There's no equivalent @value{GDBN} command. @code{gdbtk} has
30961 @samp{gdb_find_file}.
30963 @subsubheading Example
30967 @subheading The @code{-symbol-info-function} Command
30968 @findex -symbol-info-function
30970 @subsubheading Synopsis
30973 -symbol-info-function
30976 Show which function the symbol lives in.
30978 @subsubheading @value{GDBN} Command
30980 @samp{gdb_get_function} in @code{gdbtk}.
30982 @subsubheading Example
30986 @subheading The @code{-symbol-info-line} Command
30987 @findex -symbol-info-line
30989 @subsubheading Synopsis
30995 Show the core addresses of the code for a source line.
30997 @subsubheading @value{GDBN} Command
30999 The corresponding @value{GDBN} command is @samp{info line}.
31000 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
31002 @subsubheading Example
31006 @subheading The @code{-symbol-info-symbol} Command
31007 @findex -symbol-info-symbol
31009 @subsubheading Synopsis
31012 -symbol-info-symbol @var{addr}
31015 Describe what symbol is at location @var{addr}.
31017 @subsubheading @value{GDBN} Command
31019 The corresponding @value{GDBN} command is @samp{info symbol}.
31021 @subsubheading Example
31025 @subheading The @code{-symbol-list-functions} Command
31026 @findex -symbol-list-functions
31028 @subsubheading Synopsis
31031 -symbol-list-functions
31034 List the functions in the executable.
31036 @subsubheading @value{GDBN} Command
31038 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
31039 @samp{gdb_search} in @code{gdbtk}.
31041 @subsubheading Example
31046 @subheading The @code{-symbol-list-lines} Command
31047 @findex -symbol-list-lines
31049 @subsubheading Synopsis
31052 -symbol-list-lines @var{filename}
31055 Print the list of lines that contain code and their associated program
31056 addresses for the given source filename. The entries are sorted in
31057 ascending PC order.
31059 @subsubheading @value{GDBN} Command
31061 There is no corresponding @value{GDBN} command.
31063 @subsubheading Example
31066 -symbol-list-lines basics.c
31067 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
31073 @subheading The @code{-symbol-list-types} Command
31074 @findex -symbol-list-types
31076 @subsubheading Synopsis
31082 List all the type names.
31084 @subsubheading @value{GDBN} Command
31086 The corresponding commands are @samp{info types} in @value{GDBN},
31087 @samp{gdb_search} in @code{gdbtk}.
31089 @subsubheading Example
31093 @subheading The @code{-symbol-list-variables} Command
31094 @findex -symbol-list-variables
31096 @subsubheading Synopsis
31099 -symbol-list-variables
31102 List all the global and static variable names.
31104 @subsubheading @value{GDBN} Command
31106 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
31108 @subsubheading Example
31112 @subheading The @code{-symbol-locate} Command
31113 @findex -symbol-locate
31115 @subsubheading Synopsis
31121 @subsubheading @value{GDBN} Command
31123 @samp{gdb_loc} in @code{gdbtk}.
31125 @subsubheading Example
31129 @subheading The @code{-symbol-type} Command
31130 @findex -symbol-type
31132 @subsubheading Synopsis
31135 -symbol-type @var{variable}
31138 Show type of @var{variable}.
31140 @subsubheading @value{GDBN} Command
31142 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
31143 @samp{gdb_obj_variable}.
31145 @subsubheading Example
31150 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31151 @node GDB/MI File Commands
31152 @section @sc{gdb/mi} File Commands
31154 This section describes the GDB/MI commands to specify executable file names
31155 and to read in and obtain symbol table information.
31157 @subheading The @code{-file-exec-and-symbols} Command
31158 @findex -file-exec-and-symbols
31160 @subsubheading Synopsis
31163 -file-exec-and-symbols @var{file}
31166 Specify the executable file to be debugged. This file is the one from
31167 which the symbol table is also read. If no file is specified, the
31168 command clears the executable and symbol information. If breakpoints
31169 are set when using this command with no arguments, @value{GDBN} will produce
31170 error messages. Otherwise, no output is produced, except a completion
31173 @subsubheading @value{GDBN} Command
31175 The corresponding @value{GDBN} command is @samp{file}.
31177 @subsubheading Example
31181 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31187 @subheading The @code{-file-exec-file} Command
31188 @findex -file-exec-file
31190 @subsubheading Synopsis
31193 -file-exec-file @var{file}
31196 Specify the executable file to be debugged. Unlike
31197 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
31198 from this file. If used without argument, @value{GDBN} clears the information
31199 about the executable file. No output is produced, except a completion
31202 @subsubheading @value{GDBN} Command
31204 The corresponding @value{GDBN} command is @samp{exec-file}.
31206 @subsubheading Example
31210 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31217 @subheading The @code{-file-list-exec-sections} Command
31218 @findex -file-list-exec-sections
31220 @subsubheading Synopsis
31223 -file-list-exec-sections
31226 List the sections of the current executable file.
31228 @subsubheading @value{GDBN} Command
31230 The @value{GDBN} command @samp{info file} shows, among the rest, the same
31231 information as this command. @code{gdbtk} has a corresponding command
31232 @samp{gdb_load_info}.
31234 @subsubheading Example
31239 @subheading The @code{-file-list-exec-source-file} Command
31240 @findex -file-list-exec-source-file
31242 @subsubheading Synopsis
31245 -file-list-exec-source-file
31248 List the line number, the current source file, and the absolute path
31249 to the current source file for the current executable. The macro
31250 information field has a value of @samp{1} or @samp{0} depending on
31251 whether or not the file includes preprocessor macro information.
31253 @subsubheading @value{GDBN} Command
31255 The @value{GDBN} equivalent is @samp{info source}
31257 @subsubheading Example
31261 123-file-list-exec-source-file
31262 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
31267 @subheading The @code{-file-list-exec-source-files} Command
31268 @findex -file-list-exec-source-files
31270 @subsubheading Synopsis
31273 -file-list-exec-source-files
31276 List the source files for the current executable.
31278 It will always output both the filename and fullname (absolute file
31279 name) of a source file.
31281 @subsubheading @value{GDBN} Command
31283 The @value{GDBN} equivalent is @samp{info sources}.
31284 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
31286 @subsubheading Example
31289 -file-list-exec-source-files
31291 @{file=foo.c,fullname=/home/foo.c@},
31292 @{file=/home/bar.c,fullname=/home/bar.c@},
31293 @{file=gdb_could_not_find_fullpath.c@}]
31298 @subheading The @code{-file-list-shared-libraries} Command
31299 @findex -file-list-shared-libraries
31301 @subsubheading Synopsis
31304 -file-list-shared-libraries
31307 List the shared libraries in the program.
31309 @subsubheading @value{GDBN} Command
31311 The corresponding @value{GDBN} command is @samp{info shared}.
31313 @subsubheading Example
31317 @subheading The @code{-file-list-symbol-files} Command
31318 @findex -file-list-symbol-files
31320 @subsubheading Synopsis
31323 -file-list-symbol-files
31328 @subsubheading @value{GDBN} Command
31330 The corresponding @value{GDBN} command is @samp{info file} (part of it).
31332 @subsubheading Example
31337 @subheading The @code{-file-symbol-file} Command
31338 @findex -file-symbol-file
31340 @subsubheading Synopsis
31343 -file-symbol-file @var{file}
31346 Read symbol table info from the specified @var{file} argument. When
31347 used without arguments, clears @value{GDBN}'s symbol table info. No output is
31348 produced, except for a completion notification.
31350 @subsubheading @value{GDBN} Command
31352 The corresponding @value{GDBN} command is @samp{symbol-file}.
31354 @subsubheading Example
31358 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31364 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31365 @node GDB/MI Memory Overlay Commands
31366 @section @sc{gdb/mi} Memory Overlay Commands
31368 The memory overlay commands are not implemented.
31370 @c @subheading -overlay-auto
31372 @c @subheading -overlay-list-mapping-state
31374 @c @subheading -overlay-list-overlays
31376 @c @subheading -overlay-map
31378 @c @subheading -overlay-off
31380 @c @subheading -overlay-on
31382 @c @subheading -overlay-unmap
31384 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31385 @node GDB/MI Signal Handling Commands
31386 @section @sc{gdb/mi} Signal Handling Commands
31388 Signal handling commands are not implemented.
31390 @c @subheading -signal-handle
31392 @c @subheading -signal-list-handle-actions
31394 @c @subheading -signal-list-signal-types
31398 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31399 @node GDB/MI Target Manipulation
31400 @section @sc{gdb/mi} Target Manipulation Commands
31403 @subheading The @code{-target-attach} Command
31404 @findex -target-attach
31406 @subsubheading Synopsis
31409 -target-attach @var{pid} | @var{gid} | @var{file}
31412 Attach to a process @var{pid} or a file @var{file} outside of
31413 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
31414 group, the id previously returned by
31415 @samp{-list-thread-groups --available} must be used.
31417 @subsubheading @value{GDBN} Command
31419 The corresponding @value{GDBN} command is @samp{attach}.
31421 @subsubheading Example
31425 =thread-created,id="1"
31426 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
31432 @subheading The @code{-target-compare-sections} Command
31433 @findex -target-compare-sections
31435 @subsubheading Synopsis
31438 -target-compare-sections [ @var{section} ]
31441 Compare data of section @var{section} on target to the exec file.
31442 Without the argument, all sections are compared.
31444 @subsubheading @value{GDBN} Command
31446 The @value{GDBN} equivalent is @samp{compare-sections}.
31448 @subsubheading Example
31453 @subheading The @code{-target-detach} Command
31454 @findex -target-detach
31456 @subsubheading Synopsis
31459 -target-detach [ @var{pid} | @var{gid} ]
31462 Detach from the remote target which normally resumes its execution.
31463 If either @var{pid} or @var{gid} is specified, detaches from either
31464 the specified process, or specified thread group. There's no output.
31466 @subsubheading @value{GDBN} Command
31468 The corresponding @value{GDBN} command is @samp{detach}.
31470 @subsubheading Example
31480 @subheading The @code{-target-disconnect} Command
31481 @findex -target-disconnect
31483 @subsubheading Synopsis
31489 Disconnect from the remote target. There's no output and the target is
31490 generally not resumed.
31492 @subsubheading @value{GDBN} Command
31494 The corresponding @value{GDBN} command is @samp{disconnect}.
31496 @subsubheading Example
31506 @subheading The @code{-target-download} Command
31507 @findex -target-download
31509 @subsubheading Synopsis
31515 Loads the executable onto the remote target.
31516 It prints out an update message every half second, which includes the fields:
31520 The name of the section.
31522 The size of what has been sent so far for that section.
31524 The size of the section.
31526 The total size of what was sent so far (the current and the previous sections).
31528 The size of the overall executable to download.
31532 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
31533 @sc{gdb/mi} Output Syntax}).
31535 In addition, it prints the name and size of the sections, as they are
31536 downloaded. These messages include the following fields:
31540 The name of the section.
31542 The size of the section.
31544 The size of the overall executable to download.
31548 At the end, a summary is printed.
31550 @subsubheading @value{GDBN} Command
31552 The corresponding @value{GDBN} command is @samp{load}.
31554 @subsubheading Example
31556 Note: each status message appears on a single line. Here the messages
31557 have been broken down so that they can fit onto a page.
31562 +download,@{section=".text",section-size="6668",total-size="9880"@}
31563 +download,@{section=".text",section-sent="512",section-size="6668",
31564 total-sent="512",total-size="9880"@}
31565 +download,@{section=".text",section-sent="1024",section-size="6668",
31566 total-sent="1024",total-size="9880"@}
31567 +download,@{section=".text",section-sent="1536",section-size="6668",
31568 total-sent="1536",total-size="9880"@}
31569 +download,@{section=".text",section-sent="2048",section-size="6668",
31570 total-sent="2048",total-size="9880"@}
31571 +download,@{section=".text",section-sent="2560",section-size="6668",
31572 total-sent="2560",total-size="9880"@}
31573 +download,@{section=".text",section-sent="3072",section-size="6668",
31574 total-sent="3072",total-size="9880"@}
31575 +download,@{section=".text",section-sent="3584",section-size="6668",
31576 total-sent="3584",total-size="9880"@}
31577 +download,@{section=".text",section-sent="4096",section-size="6668",
31578 total-sent="4096",total-size="9880"@}
31579 +download,@{section=".text",section-sent="4608",section-size="6668",
31580 total-sent="4608",total-size="9880"@}
31581 +download,@{section=".text",section-sent="5120",section-size="6668",
31582 total-sent="5120",total-size="9880"@}
31583 +download,@{section=".text",section-sent="5632",section-size="6668",
31584 total-sent="5632",total-size="9880"@}
31585 +download,@{section=".text",section-sent="6144",section-size="6668",
31586 total-sent="6144",total-size="9880"@}
31587 +download,@{section=".text",section-sent="6656",section-size="6668",
31588 total-sent="6656",total-size="9880"@}
31589 +download,@{section=".init",section-size="28",total-size="9880"@}
31590 +download,@{section=".fini",section-size="28",total-size="9880"@}
31591 +download,@{section=".data",section-size="3156",total-size="9880"@}
31592 +download,@{section=".data",section-sent="512",section-size="3156",
31593 total-sent="7236",total-size="9880"@}
31594 +download,@{section=".data",section-sent="1024",section-size="3156",
31595 total-sent="7748",total-size="9880"@}
31596 +download,@{section=".data",section-sent="1536",section-size="3156",
31597 total-sent="8260",total-size="9880"@}
31598 +download,@{section=".data",section-sent="2048",section-size="3156",
31599 total-sent="8772",total-size="9880"@}
31600 +download,@{section=".data",section-sent="2560",section-size="3156",
31601 total-sent="9284",total-size="9880"@}
31602 +download,@{section=".data",section-sent="3072",section-size="3156",
31603 total-sent="9796",total-size="9880"@}
31604 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
31611 @subheading The @code{-target-exec-status} Command
31612 @findex -target-exec-status
31614 @subsubheading Synopsis
31617 -target-exec-status
31620 Provide information on the state of the target (whether it is running or
31621 not, for instance).
31623 @subsubheading @value{GDBN} Command
31625 There's no equivalent @value{GDBN} command.
31627 @subsubheading Example
31631 @subheading The @code{-target-list-available-targets} Command
31632 @findex -target-list-available-targets
31634 @subsubheading Synopsis
31637 -target-list-available-targets
31640 List the possible targets to connect to.
31642 @subsubheading @value{GDBN} Command
31644 The corresponding @value{GDBN} command is @samp{help target}.
31646 @subsubheading Example
31650 @subheading The @code{-target-list-current-targets} Command
31651 @findex -target-list-current-targets
31653 @subsubheading Synopsis
31656 -target-list-current-targets
31659 Describe the current target.
31661 @subsubheading @value{GDBN} Command
31663 The corresponding information is printed by @samp{info file} (among
31666 @subsubheading Example
31670 @subheading The @code{-target-list-parameters} Command
31671 @findex -target-list-parameters
31673 @subsubheading Synopsis
31676 -target-list-parameters
31682 @subsubheading @value{GDBN} Command
31686 @subsubheading Example
31690 @subheading The @code{-target-select} Command
31691 @findex -target-select
31693 @subsubheading Synopsis
31696 -target-select @var{type} @var{parameters @dots{}}
31699 Connect @value{GDBN} to the remote target. This command takes two args:
31703 The type of target, for instance @samp{remote}, etc.
31704 @item @var{parameters}
31705 Device names, host names and the like. @xref{Target Commands, ,
31706 Commands for Managing Targets}, for more details.
31709 The output is a connection notification, followed by the address at
31710 which the target program is, in the following form:
31713 ^connected,addr="@var{address}",func="@var{function name}",
31714 args=[@var{arg list}]
31717 @subsubheading @value{GDBN} Command
31719 The corresponding @value{GDBN} command is @samp{target}.
31721 @subsubheading Example
31725 -target-select remote /dev/ttya
31726 ^connected,addr="0xfe00a300",func="??",args=[]
31730 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31731 @node GDB/MI File Transfer Commands
31732 @section @sc{gdb/mi} File Transfer Commands
31735 @subheading The @code{-target-file-put} Command
31736 @findex -target-file-put
31738 @subsubheading Synopsis
31741 -target-file-put @var{hostfile} @var{targetfile}
31744 Copy file @var{hostfile} from the host system (the machine running
31745 @value{GDBN}) to @var{targetfile} on the target system.
31747 @subsubheading @value{GDBN} Command
31749 The corresponding @value{GDBN} command is @samp{remote put}.
31751 @subsubheading Example
31755 -target-file-put localfile remotefile
31761 @subheading The @code{-target-file-get} Command
31762 @findex -target-file-get
31764 @subsubheading Synopsis
31767 -target-file-get @var{targetfile} @var{hostfile}
31770 Copy file @var{targetfile} from the target system to @var{hostfile}
31771 on the host system.
31773 @subsubheading @value{GDBN} Command
31775 The corresponding @value{GDBN} command is @samp{remote get}.
31777 @subsubheading Example
31781 -target-file-get remotefile localfile
31787 @subheading The @code{-target-file-delete} Command
31788 @findex -target-file-delete
31790 @subsubheading Synopsis
31793 -target-file-delete @var{targetfile}
31796 Delete @var{targetfile} from the target system.
31798 @subsubheading @value{GDBN} Command
31800 The corresponding @value{GDBN} command is @samp{remote delete}.
31802 @subsubheading Example
31806 -target-file-delete remotefile
31812 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31813 @node GDB/MI Ada Exceptions Commands
31814 @section Ada Exceptions @sc{gdb/mi} Commands
31816 @subheading The @code{-info-ada-exceptions} Command
31817 @findex -info-ada-exceptions
31819 @subsubheading Synopsis
31822 -info-ada-exceptions [ @var{regexp}]
31825 List all Ada exceptions defined within the program being debugged.
31826 With a regular expression @var{regexp}, only those exceptions whose
31827 names match @var{regexp} are listed.
31829 @subsubheading @value{GDBN} Command
31831 The corresponding @value{GDBN} command is @samp{info exceptions}.
31833 @subsubheading Result
31835 The result is a table of Ada exceptions. The following columns are
31836 defined for each exception:
31840 The name of the exception.
31843 The address of the exception.
31847 @subsubheading Example
31850 -info-ada-exceptions aint
31851 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
31852 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
31853 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
31854 body=[@{name="constraint_error",address="0x0000000000613da0"@},
31855 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
31858 @subheading Catching Ada Exceptions
31860 The commands describing how to ask @value{GDBN} to stop when a program
31861 raises an exception are described at @ref{Ada Exception GDB/MI
31862 Catchpoint Commands}.
31865 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31866 @node GDB/MI Support Commands
31867 @section @sc{gdb/mi} Support Commands
31869 Since new commands and features get regularly added to @sc{gdb/mi},
31870 some commands are available to help front-ends query the debugger
31871 about support for these capabilities. Similarly, it is also possible
31872 to query @value{GDBN} about target support of certain features.
31874 @subheading The @code{-info-gdb-mi-command} Command
31875 @cindex @code{-info-gdb-mi-command}
31876 @findex -info-gdb-mi-command
31878 @subsubheading Synopsis
31881 -info-gdb-mi-command @var{cmd_name}
31884 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
31886 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
31887 is technically not part of the command name (@pxref{GDB/MI Input
31888 Syntax}), and thus should be omitted in @var{cmd_name}. However,
31889 for ease of use, this command also accepts the form with the leading
31892 @subsubheading @value{GDBN} Command
31894 There is no corresponding @value{GDBN} command.
31896 @subsubheading Result
31898 The result is a tuple. There is currently only one field:
31902 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
31903 @code{"false"} otherwise.
31907 @subsubheading Example
31909 Here is an example where the @sc{gdb/mi} command does not exist:
31912 -info-gdb-mi-command unsupported-command
31913 ^done,command=@{exists="false"@}
31917 And here is an example where the @sc{gdb/mi} command is known
31921 -info-gdb-mi-command symbol-list-lines
31922 ^done,command=@{exists="true"@}
31925 @subheading The @code{-list-features} Command
31926 @findex -list-features
31927 @cindex supported @sc{gdb/mi} features, list
31929 Returns a list of particular features of the MI protocol that
31930 this version of gdb implements. A feature can be a command,
31931 or a new field in an output of some command, or even an
31932 important bugfix. While a frontend can sometimes detect presence
31933 of a feature at runtime, it is easier to perform detection at debugger
31936 The command returns a list of strings, with each string naming an
31937 available feature. Each returned string is just a name, it does not
31938 have any internal structure. The list of possible feature names
31944 (gdb) -list-features
31945 ^done,result=["feature1","feature2"]
31948 The current list of features is:
31951 @item frozen-varobjs
31952 Indicates support for the @code{-var-set-frozen} command, as well
31953 as possible presense of the @code{frozen} field in the output
31954 of @code{-varobj-create}.
31955 @item pending-breakpoints
31956 Indicates support for the @option{-f} option to the @code{-break-insert}
31959 Indicates Python scripting support, Python-based
31960 pretty-printing commands, and possible presence of the
31961 @samp{display_hint} field in the output of @code{-var-list-children}
31963 Indicates support for the @code{-thread-info} command.
31964 @item data-read-memory-bytes
31965 Indicates support for the @code{-data-read-memory-bytes} and the
31966 @code{-data-write-memory-bytes} commands.
31967 @item breakpoint-notifications
31968 Indicates that changes to breakpoints and breakpoints created via the
31969 CLI will be announced via async records.
31970 @item ada-task-info
31971 Indicates support for the @code{-ada-task-info} command.
31972 @item language-option
31973 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
31974 option (@pxref{Context management}).
31975 @item info-gdb-mi-command
31976 Indicates support for the @code{-info-gdb-mi-command} command.
31977 @item undefined-command-error-code
31978 Indicates support for the "undefined-command" error code in error result
31979 records, produced when trying to execute an undefined @sc{gdb/mi} command
31980 (@pxref{GDB/MI Result Records}).
31981 @item exec-run-start-option
31982 Indicates that the @code{-exec-run} command supports the @option{--start}
31983 option (@pxref{GDB/MI Program Execution}).
31986 @subheading The @code{-list-target-features} Command
31987 @findex -list-target-features
31989 Returns a list of particular features that are supported by the
31990 target. Those features affect the permitted MI commands, but
31991 unlike the features reported by the @code{-list-features} command, the
31992 features depend on which target GDB is using at the moment. Whenever
31993 a target can change, due to commands such as @code{-target-select},
31994 @code{-target-attach} or @code{-exec-run}, the list of target features
31995 may change, and the frontend should obtain it again.
31999 (gdb) -list-target-features
32000 ^done,result=["async"]
32003 The current list of features is:
32007 Indicates that the target is capable of asynchronous command
32008 execution, which means that @value{GDBN} will accept further commands
32009 while the target is running.
32012 Indicates that the target is capable of reverse execution.
32013 @xref{Reverse Execution}, for more information.
32017 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32018 @node GDB/MI Miscellaneous Commands
32019 @section Miscellaneous @sc{gdb/mi} Commands
32021 @c @subheading -gdb-complete
32023 @subheading The @code{-gdb-exit} Command
32026 @subsubheading Synopsis
32032 Exit @value{GDBN} immediately.
32034 @subsubheading @value{GDBN} Command
32036 Approximately corresponds to @samp{quit}.
32038 @subsubheading Example
32048 @subheading The @code{-exec-abort} Command
32049 @findex -exec-abort
32051 @subsubheading Synopsis
32057 Kill the inferior running program.
32059 @subsubheading @value{GDBN} Command
32061 The corresponding @value{GDBN} command is @samp{kill}.
32063 @subsubheading Example
32068 @subheading The @code{-gdb-set} Command
32071 @subsubheading Synopsis
32077 Set an internal @value{GDBN} variable.
32078 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
32080 @subsubheading @value{GDBN} Command
32082 The corresponding @value{GDBN} command is @samp{set}.
32084 @subsubheading Example
32094 @subheading The @code{-gdb-show} Command
32097 @subsubheading Synopsis
32103 Show the current value of a @value{GDBN} variable.
32105 @subsubheading @value{GDBN} Command
32107 The corresponding @value{GDBN} command is @samp{show}.
32109 @subsubheading Example
32118 @c @subheading -gdb-source
32121 @subheading The @code{-gdb-version} Command
32122 @findex -gdb-version
32124 @subsubheading Synopsis
32130 Show version information for @value{GDBN}. Used mostly in testing.
32132 @subsubheading @value{GDBN} Command
32134 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
32135 default shows this information when you start an interactive session.
32137 @subsubheading Example
32139 @c This example modifies the actual output from GDB to avoid overfull
32145 ~Copyright 2000 Free Software Foundation, Inc.
32146 ~GDB is free software, covered by the GNU General Public License, and
32147 ~you are welcome to change it and/or distribute copies of it under
32148 ~ certain conditions.
32149 ~Type "show copying" to see the conditions.
32150 ~There is absolutely no warranty for GDB. Type "show warranty" for
32152 ~This GDB was configured as
32153 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
32158 @subheading The @code{-list-thread-groups} Command
32159 @findex -list-thread-groups
32161 @subheading Synopsis
32164 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
32167 Lists thread groups (@pxref{Thread groups}). When a single thread
32168 group is passed as the argument, lists the children of that group.
32169 When several thread group are passed, lists information about those
32170 thread groups. Without any parameters, lists information about all
32171 top-level thread groups.
32173 Normally, thread groups that are being debugged are reported.
32174 With the @samp{--available} option, @value{GDBN} reports thread groups
32175 available on the target.
32177 The output of this command may have either a @samp{threads} result or
32178 a @samp{groups} result. The @samp{thread} result has a list of tuples
32179 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
32180 Information}). The @samp{groups} result has a list of tuples as value,
32181 each tuple describing a thread group. If top-level groups are
32182 requested (that is, no parameter is passed), or when several groups
32183 are passed, the output always has a @samp{groups} result. The format
32184 of the @samp{group} result is described below.
32186 To reduce the number of roundtrips it's possible to list thread groups
32187 together with their children, by passing the @samp{--recurse} option
32188 and the recursion depth. Presently, only recursion depth of 1 is
32189 permitted. If this option is present, then every reported thread group
32190 will also include its children, either as @samp{group} or
32191 @samp{threads} field.
32193 In general, any combination of option and parameters is permitted, with
32194 the following caveats:
32198 When a single thread group is passed, the output will typically
32199 be the @samp{threads} result. Because threads may not contain
32200 anything, the @samp{recurse} option will be ignored.
32203 When the @samp{--available} option is passed, limited information may
32204 be available. In particular, the list of threads of a process might
32205 be inaccessible. Further, specifying specific thread groups might
32206 not give any performance advantage over listing all thread groups.
32207 The frontend should assume that @samp{-list-thread-groups --available}
32208 is always an expensive operation and cache the results.
32212 The @samp{groups} result is a list of tuples, where each tuple may
32213 have the following fields:
32217 Identifier of the thread group. This field is always present.
32218 The identifier is an opaque string; frontends should not try to
32219 convert it to an integer, even though it might look like one.
32222 The type of the thread group. At present, only @samp{process} is a
32226 The target-specific process identifier. This field is only present
32227 for thread groups of type @samp{process} and only if the process exists.
32230 The exit code of this group's last exited thread, formatted in octal.
32231 This field is only present for thread groups of type @samp{process} and
32232 only if the process is not running.
32235 The number of children this thread group has. This field may be
32236 absent for an available thread group.
32239 This field has a list of tuples as value, each tuple describing a
32240 thread. It may be present if the @samp{--recurse} option is
32241 specified, and it's actually possible to obtain the threads.
32244 This field is a list of integers, each identifying a core that one
32245 thread of the group is running on. This field may be absent if
32246 such information is not available.
32249 The name of the executable file that corresponds to this thread group.
32250 The field is only present for thread groups of type @samp{process},
32251 and only if there is a corresponding executable file.
32255 @subheading Example
32259 -list-thread-groups
32260 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
32261 -list-thread-groups 17
32262 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
32263 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
32264 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
32265 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
32266 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
32267 -list-thread-groups --available
32268 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
32269 -list-thread-groups --available --recurse 1
32270 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
32271 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
32272 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
32273 -list-thread-groups --available --recurse 1 17 18
32274 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
32275 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
32276 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
32279 @subheading The @code{-info-os} Command
32282 @subsubheading Synopsis
32285 -info-os [ @var{type} ]
32288 If no argument is supplied, the command returns a table of available
32289 operating-system-specific information types. If one of these types is
32290 supplied as an argument @var{type}, then the command returns a table
32291 of data of that type.
32293 The types of information available depend on the target operating
32296 @subsubheading @value{GDBN} Command
32298 The corresponding @value{GDBN} command is @samp{info os}.
32300 @subsubheading Example
32302 When run on a @sc{gnu}/Linux system, the output will look something
32308 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
32309 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
32310 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
32311 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
32312 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
32314 item=@{col0="files",col1="Listing of all file descriptors",
32315 col2="File descriptors"@},
32316 item=@{col0="modules",col1="Listing of all loaded kernel modules",
32317 col2="Kernel modules"@},
32318 item=@{col0="msg",col1="Listing of all message queues",
32319 col2="Message queues"@},
32320 item=@{col0="processes",col1="Listing of all processes",
32321 col2="Processes"@},
32322 item=@{col0="procgroups",col1="Listing of all process groups",
32323 col2="Process groups"@},
32324 item=@{col0="semaphores",col1="Listing of all semaphores",
32325 col2="Semaphores"@},
32326 item=@{col0="shm",col1="Listing of all shared-memory regions",
32327 col2="Shared-memory regions"@},
32328 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
32330 item=@{col0="threads",col1="Listing of all threads",
32334 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
32335 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
32336 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
32337 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
32338 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
32339 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
32340 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
32341 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
32343 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
32344 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
32348 (Note that the MI output here includes a @code{"Title"} column that
32349 does not appear in command-line @code{info os}; this column is useful
32350 for MI clients that want to enumerate the types of data, such as in a
32351 popup menu, but is needless clutter on the command line, and
32352 @code{info os} omits it.)
32354 @subheading The @code{-add-inferior} Command
32355 @findex -add-inferior
32357 @subheading Synopsis
32363 Creates a new inferior (@pxref{Inferiors and Programs}). The created
32364 inferior is not associated with any executable. Such association may
32365 be established with the @samp{-file-exec-and-symbols} command
32366 (@pxref{GDB/MI File Commands}). The command response has a single
32367 field, @samp{inferior}, whose value is the identifier of the
32368 thread group corresponding to the new inferior.
32370 @subheading Example
32375 ^done,inferior="i3"
32378 @subheading The @code{-interpreter-exec} Command
32379 @findex -interpreter-exec
32381 @subheading Synopsis
32384 -interpreter-exec @var{interpreter} @var{command}
32386 @anchor{-interpreter-exec}
32388 Execute the specified @var{command} in the given @var{interpreter}.
32390 @subheading @value{GDBN} Command
32392 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
32394 @subheading Example
32398 -interpreter-exec console "break main"
32399 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
32400 &"During symbol reading, bad structure-type format.\n"
32401 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
32406 @subheading The @code{-inferior-tty-set} Command
32407 @findex -inferior-tty-set
32409 @subheading Synopsis
32412 -inferior-tty-set /dev/pts/1
32415 Set terminal for future runs of the program being debugged.
32417 @subheading @value{GDBN} Command
32419 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
32421 @subheading Example
32425 -inferior-tty-set /dev/pts/1
32430 @subheading The @code{-inferior-tty-show} Command
32431 @findex -inferior-tty-show
32433 @subheading Synopsis
32439 Show terminal for future runs of program being debugged.
32441 @subheading @value{GDBN} Command
32443 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
32445 @subheading Example
32449 -inferior-tty-set /dev/pts/1
32453 ^done,inferior_tty_terminal="/dev/pts/1"
32457 @subheading The @code{-enable-timings} Command
32458 @findex -enable-timings
32460 @subheading Synopsis
32463 -enable-timings [yes | no]
32466 Toggle the printing of the wallclock, user and system times for an MI
32467 command as a field in its output. This command is to help frontend
32468 developers optimize the performance of their code. No argument is
32469 equivalent to @samp{yes}.
32471 @subheading @value{GDBN} Command
32475 @subheading Example
32483 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
32484 addr="0x080484ed",func="main",file="myprog.c",
32485 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
32487 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
32495 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
32496 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
32497 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
32498 fullname="/home/nickrob/myprog.c",line="73"@}
32503 @chapter @value{GDBN} Annotations
32505 This chapter describes annotations in @value{GDBN}. Annotations were
32506 designed to interface @value{GDBN} to graphical user interfaces or other
32507 similar programs which want to interact with @value{GDBN} at a
32508 relatively high level.
32510 The annotation mechanism has largely been superseded by @sc{gdb/mi}
32514 This is Edition @value{EDITION}, @value{DATE}.
32518 * Annotations Overview:: What annotations are; the general syntax.
32519 * Server Prefix:: Issuing a command without affecting user state.
32520 * Prompting:: Annotations marking @value{GDBN}'s need for input.
32521 * Errors:: Annotations for error messages.
32522 * Invalidation:: Some annotations describe things now invalid.
32523 * Annotations for Running::
32524 Whether the program is running, how it stopped, etc.
32525 * Source Annotations:: Annotations describing source code.
32528 @node Annotations Overview
32529 @section What is an Annotation?
32530 @cindex annotations
32532 Annotations start with a newline character, two @samp{control-z}
32533 characters, and the name of the annotation. If there is no additional
32534 information associated with this annotation, the name of the annotation
32535 is followed immediately by a newline. If there is additional
32536 information, the name of the annotation is followed by a space, the
32537 additional information, and a newline. The additional information
32538 cannot contain newline characters.
32540 Any output not beginning with a newline and two @samp{control-z}
32541 characters denotes literal output from @value{GDBN}. Currently there is
32542 no need for @value{GDBN} to output a newline followed by two
32543 @samp{control-z} characters, but if there was such a need, the
32544 annotations could be extended with an @samp{escape} annotation which
32545 means those three characters as output.
32547 The annotation @var{level}, which is specified using the
32548 @option{--annotate} command line option (@pxref{Mode Options}), controls
32549 how much information @value{GDBN} prints together with its prompt,
32550 values of expressions, source lines, and other types of output. Level 0
32551 is for no annotations, level 1 is for use when @value{GDBN} is run as a
32552 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
32553 for programs that control @value{GDBN}, and level 2 annotations have
32554 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
32555 Interface, annotate, GDB's Obsolete Annotations}).
32558 @kindex set annotate
32559 @item set annotate @var{level}
32560 The @value{GDBN} command @code{set annotate} sets the level of
32561 annotations to the specified @var{level}.
32563 @item show annotate
32564 @kindex show annotate
32565 Show the current annotation level.
32568 This chapter describes level 3 annotations.
32570 A simple example of starting up @value{GDBN} with annotations is:
32573 $ @kbd{gdb --annotate=3}
32575 Copyright 2003 Free Software Foundation, Inc.
32576 GDB is free software, covered by the GNU General Public License,
32577 and you are welcome to change it and/or distribute copies of it
32578 under certain conditions.
32579 Type "show copying" to see the conditions.
32580 There is absolutely no warranty for GDB. Type "show warranty"
32582 This GDB was configured as "i386-pc-linux-gnu"
32593 Here @samp{quit} is input to @value{GDBN}; the rest is output from
32594 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
32595 denotes a @samp{control-z} character) are annotations; the rest is
32596 output from @value{GDBN}.
32598 @node Server Prefix
32599 @section The Server Prefix
32600 @cindex server prefix
32602 If you prefix a command with @samp{server } then it will not affect
32603 the command history, nor will it affect @value{GDBN}'s notion of which
32604 command to repeat if @key{RET} is pressed on a line by itself. This
32605 means that commands can be run behind a user's back by a front-end in
32606 a transparent manner.
32608 The @code{server } prefix does not affect the recording of values into
32609 the value history; to print a value without recording it into the
32610 value history, use the @code{output} command instead of the
32611 @code{print} command.
32613 Using this prefix also disables confirmation requests
32614 (@pxref{confirmation requests}).
32617 @section Annotation for @value{GDBN} Input
32619 @cindex annotations for prompts
32620 When @value{GDBN} prompts for input, it annotates this fact so it is possible
32621 to know when to send output, when the output from a given command is
32624 Different kinds of input each have a different @dfn{input type}. Each
32625 input type has three annotations: a @code{pre-} annotation, which
32626 denotes the beginning of any prompt which is being output, a plain
32627 annotation, which denotes the end of the prompt, and then a @code{post-}
32628 annotation which denotes the end of any echo which may (or may not) be
32629 associated with the input. For example, the @code{prompt} input type
32630 features the following annotations:
32638 The input types are
32641 @findex pre-prompt annotation
32642 @findex prompt annotation
32643 @findex post-prompt annotation
32645 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
32647 @findex pre-commands annotation
32648 @findex commands annotation
32649 @findex post-commands annotation
32651 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
32652 command. The annotations are repeated for each command which is input.
32654 @findex pre-overload-choice annotation
32655 @findex overload-choice annotation
32656 @findex post-overload-choice annotation
32657 @item overload-choice
32658 When @value{GDBN} wants the user to select between various overloaded functions.
32660 @findex pre-query annotation
32661 @findex query annotation
32662 @findex post-query annotation
32664 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
32666 @findex pre-prompt-for-continue annotation
32667 @findex prompt-for-continue annotation
32668 @findex post-prompt-for-continue annotation
32669 @item prompt-for-continue
32670 When @value{GDBN} is asking the user to press return to continue. Note: Don't
32671 expect this to work well; instead use @code{set height 0} to disable
32672 prompting. This is because the counting of lines is buggy in the
32673 presence of annotations.
32678 @cindex annotations for errors, warnings and interrupts
32680 @findex quit annotation
32685 This annotation occurs right before @value{GDBN} responds to an interrupt.
32687 @findex error annotation
32692 This annotation occurs right before @value{GDBN} responds to an error.
32694 Quit and error annotations indicate that any annotations which @value{GDBN} was
32695 in the middle of may end abruptly. For example, if a
32696 @code{value-history-begin} annotation is followed by a @code{error}, one
32697 cannot expect to receive the matching @code{value-history-end}. One
32698 cannot expect not to receive it either, however; an error annotation
32699 does not necessarily mean that @value{GDBN} is immediately returning all the way
32702 @findex error-begin annotation
32703 A quit or error annotation may be preceded by
32709 Any output between that and the quit or error annotation is the error
32712 Warning messages are not yet annotated.
32713 @c If we want to change that, need to fix warning(), type_error(),
32714 @c range_error(), and possibly other places.
32717 @section Invalidation Notices
32719 @cindex annotations for invalidation messages
32720 The following annotations say that certain pieces of state may have
32724 @findex frames-invalid annotation
32725 @item ^Z^Zframes-invalid
32727 The frames (for example, output from the @code{backtrace} command) may
32730 @findex breakpoints-invalid annotation
32731 @item ^Z^Zbreakpoints-invalid
32733 The breakpoints may have changed. For example, the user just added or
32734 deleted a breakpoint.
32737 @node Annotations for Running
32738 @section Running the Program
32739 @cindex annotations for running programs
32741 @findex starting annotation
32742 @findex stopping annotation
32743 When the program starts executing due to a @value{GDBN} command such as
32744 @code{step} or @code{continue},
32750 is output. When the program stops,
32756 is output. Before the @code{stopped} annotation, a variety of
32757 annotations describe how the program stopped.
32760 @findex exited annotation
32761 @item ^Z^Zexited @var{exit-status}
32762 The program exited, and @var{exit-status} is the exit status (zero for
32763 successful exit, otherwise nonzero).
32765 @findex signalled annotation
32766 @findex signal-name annotation
32767 @findex signal-name-end annotation
32768 @findex signal-string annotation
32769 @findex signal-string-end annotation
32770 @item ^Z^Zsignalled
32771 The program exited with a signal. After the @code{^Z^Zsignalled}, the
32772 annotation continues:
32778 ^Z^Zsignal-name-end
32782 ^Z^Zsignal-string-end
32787 where @var{name} is the name of the signal, such as @code{SIGILL} or
32788 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
32789 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
32790 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
32791 user's benefit and have no particular format.
32793 @findex signal annotation
32795 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
32796 just saying that the program received the signal, not that it was
32797 terminated with it.
32799 @findex breakpoint annotation
32800 @item ^Z^Zbreakpoint @var{number}
32801 The program hit breakpoint number @var{number}.
32803 @findex watchpoint annotation
32804 @item ^Z^Zwatchpoint @var{number}
32805 The program hit watchpoint number @var{number}.
32808 @node Source Annotations
32809 @section Displaying Source
32810 @cindex annotations for source display
32812 @findex source annotation
32813 The following annotation is used instead of displaying source code:
32816 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
32819 where @var{filename} is an absolute file name indicating which source
32820 file, @var{line} is the line number within that file (where 1 is the
32821 first line in the file), @var{character} is the character position
32822 within the file (where 0 is the first character in the file) (for most
32823 debug formats this will necessarily point to the beginning of a line),
32824 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
32825 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
32826 @var{addr} is the address in the target program associated with the
32827 source which is being displayed. The @var{addr} is in the form @samp{0x}
32828 followed by one or more lowercase hex digits (note that this does not
32829 depend on the language).
32831 @node JIT Interface
32832 @chapter JIT Compilation Interface
32833 @cindex just-in-time compilation
32834 @cindex JIT compilation interface
32836 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
32837 interface. A JIT compiler is a program or library that generates native
32838 executable code at runtime and executes it, usually in order to achieve good
32839 performance while maintaining platform independence.
32841 Programs that use JIT compilation are normally difficult to debug because
32842 portions of their code are generated at runtime, instead of being loaded from
32843 object files, which is where @value{GDBN} normally finds the program's symbols
32844 and debug information. In order to debug programs that use JIT compilation,
32845 @value{GDBN} has an interface that allows the program to register in-memory
32846 symbol files with @value{GDBN} at runtime.
32848 If you are using @value{GDBN} to debug a program that uses this interface, then
32849 it should work transparently so long as you have not stripped the binary. If
32850 you are developing a JIT compiler, then the interface is documented in the rest
32851 of this chapter. At this time, the only known client of this interface is the
32854 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
32855 JIT compiler communicates with @value{GDBN} by writing data into a global
32856 variable and calling a fuction at a well-known symbol. When @value{GDBN}
32857 attaches, it reads a linked list of symbol files from the global variable to
32858 find existing code, and puts a breakpoint in the function so that it can find
32859 out about additional code.
32862 * Declarations:: Relevant C struct declarations
32863 * Registering Code:: Steps to register code
32864 * Unregistering Code:: Steps to unregister code
32865 * Custom Debug Info:: Emit debug information in a custom format
32869 @section JIT Declarations
32871 These are the relevant struct declarations that a C program should include to
32872 implement the interface:
32882 struct jit_code_entry
32884 struct jit_code_entry *next_entry;
32885 struct jit_code_entry *prev_entry;
32886 const char *symfile_addr;
32887 uint64_t symfile_size;
32890 struct jit_descriptor
32893 /* This type should be jit_actions_t, but we use uint32_t
32894 to be explicit about the bitwidth. */
32895 uint32_t action_flag;
32896 struct jit_code_entry *relevant_entry;
32897 struct jit_code_entry *first_entry;
32900 /* GDB puts a breakpoint in this function. */
32901 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
32903 /* Make sure to specify the version statically, because the
32904 debugger may check the version before we can set it. */
32905 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
32908 If the JIT is multi-threaded, then it is important that the JIT synchronize any
32909 modifications to this global data properly, which can easily be done by putting
32910 a global mutex around modifications to these structures.
32912 @node Registering Code
32913 @section Registering Code
32915 To register code with @value{GDBN}, the JIT should follow this protocol:
32919 Generate an object file in memory with symbols and other desired debug
32920 information. The file must include the virtual addresses of the sections.
32923 Create a code entry for the file, which gives the start and size of the symbol
32927 Add it to the linked list in the JIT descriptor.
32930 Point the relevant_entry field of the descriptor at the entry.
32933 Set @code{action_flag} to @code{JIT_REGISTER} and call
32934 @code{__jit_debug_register_code}.
32937 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
32938 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
32939 new code. However, the linked list must still be maintained in order to allow
32940 @value{GDBN} to attach to a running process and still find the symbol files.
32942 @node Unregistering Code
32943 @section Unregistering Code
32945 If code is freed, then the JIT should use the following protocol:
32949 Remove the code entry corresponding to the code from the linked list.
32952 Point the @code{relevant_entry} field of the descriptor at the code entry.
32955 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
32956 @code{__jit_debug_register_code}.
32959 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
32960 and the JIT will leak the memory used for the associated symbol files.
32962 @node Custom Debug Info
32963 @section Custom Debug Info
32964 @cindex custom JIT debug info
32965 @cindex JIT debug info reader
32967 Generating debug information in platform-native file formats (like ELF
32968 or COFF) may be an overkill for JIT compilers; especially if all the
32969 debug info is used for is displaying a meaningful backtrace. The
32970 issue can be resolved by having the JIT writers decide on a debug info
32971 format and also provide a reader that parses the debug info generated
32972 by the JIT compiler. This section gives a brief overview on writing
32973 such a parser. More specific details can be found in the source file
32974 @file{gdb/jit-reader.in}, which is also installed as a header at
32975 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
32977 The reader is implemented as a shared object (so this functionality is
32978 not available on platforms which don't allow loading shared objects at
32979 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
32980 @code{jit-reader-unload} are provided, to be used to load and unload
32981 the readers from a preconfigured directory. Once loaded, the shared
32982 object is used the parse the debug information emitted by the JIT
32986 * Using JIT Debug Info Readers:: How to use supplied readers correctly
32987 * Writing JIT Debug Info Readers:: Creating a debug-info reader
32990 @node Using JIT Debug Info Readers
32991 @subsection Using JIT Debug Info Readers
32992 @kindex jit-reader-load
32993 @kindex jit-reader-unload
32995 Readers can be loaded and unloaded using the @code{jit-reader-load}
32996 and @code{jit-reader-unload} commands.
32999 @item jit-reader-load @var{reader}
33000 Load the JIT reader named @var{reader}, which is a shared
33001 object specified as either an absolute or a relative file name. In
33002 the latter case, @value{GDBN} will try to load the reader from a
33003 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
33004 system (here @var{libdir} is the system library directory, often
33005 @file{/usr/local/lib}).
33007 Only one reader can be active at a time; trying to load a second
33008 reader when one is already loaded will result in @value{GDBN}
33009 reporting an error. A new JIT reader can be loaded by first unloading
33010 the current one using @code{jit-reader-unload} and then invoking
33011 @code{jit-reader-load}.
33013 @item jit-reader-unload
33014 Unload the currently loaded JIT reader.
33018 @node Writing JIT Debug Info Readers
33019 @subsection Writing JIT Debug Info Readers
33020 @cindex writing JIT debug info readers
33022 As mentioned, a reader is essentially a shared object conforming to a
33023 certain ABI. This ABI is described in @file{jit-reader.h}.
33025 @file{jit-reader.h} defines the structures, macros and functions
33026 required to write a reader. It is installed (along with
33027 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
33028 the system include directory.
33030 Readers need to be released under a GPL compatible license. A reader
33031 can be declared as released under such a license by placing the macro
33032 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
33034 The entry point for readers is the symbol @code{gdb_init_reader},
33035 which is expected to be a function with the prototype
33037 @findex gdb_init_reader
33039 extern struct gdb_reader_funcs *gdb_init_reader (void);
33042 @cindex @code{struct gdb_reader_funcs}
33044 @code{struct gdb_reader_funcs} contains a set of pointers to callback
33045 functions. These functions are executed to read the debug info
33046 generated by the JIT compiler (@code{read}), to unwind stack frames
33047 (@code{unwind}) and to create canonical frame IDs
33048 (@code{get_Frame_id}). It also has a callback that is called when the
33049 reader is being unloaded (@code{destroy}). The struct looks like this
33052 struct gdb_reader_funcs
33054 /* Must be set to GDB_READER_INTERFACE_VERSION. */
33055 int reader_version;
33057 /* For use by the reader. */
33060 gdb_read_debug_info *read;
33061 gdb_unwind_frame *unwind;
33062 gdb_get_frame_id *get_frame_id;
33063 gdb_destroy_reader *destroy;
33067 @cindex @code{struct gdb_symbol_callbacks}
33068 @cindex @code{struct gdb_unwind_callbacks}
33070 The callbacks are provided with another set of callbacks by
33071 @value{GDBN} to do their job. For @code{read}, these callbacks are
33072 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
33073 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
33074 @code{struct gdb_symbol_callbacks} has callbacks to create new object
33075 files and new symbol tables inside those object files. @code{struct
33076 gdb_unwind_callbacks} has callbacks to read registers off the current
33077 frame and to write out the values of the registers in the previous
33078 frame. Both have a callback (@code{target_read}) to read bytes off the
33079 target's address space.
33081 @node In-Process Agent
33082 @chapter In-Process Agent
33083 @cindex debugging agent
33084 The traditional debugging model is conceptually low-speed, but works fine,
33085 because most bugs can be reproduced in debugging-mode execution. However,
33086 as multi-core or many-core processors are becoming mainstream, and
33087 multi-threaded programs become more and more popular, there should be more
33088 and more bugs that only manifest themselves at normal-mode execution, for
33089 example, thread races, because debugger's interference with the program's
33090 timing may conceal the bugs. On the other hand, in some applications,
33091 it is not feasible for the debugger to interrupt the program's execution
33092 long enough for the developer to learn anything helpful about its behavior.
33093 If the program's correctness depends on its real-time behavior, delays
33094 introduced by a debugger might cause the program to fail, even when the
33095 code itself is correct. It is useful to be able to observe the program's
33096 behavior without interrupting it.
33098 Therefore, traditional debugging model is too intrusive to reproduce
33099 some bugs. In order to reduce the interference with the program, we can
33100 reduce the number of operations performed by debugger. The
33101 @dfn{In-Process Agent}, a shared library, is running within the same
33102 process with inferior, and is able to perform some debugging operations
33103 itself. As a result, debugger is only involved when necessary, and
33104 performance of debugging can be improved accordingly. Note that
33105 interference with program can be reduced but can't be removed completely,
33106 because the in-process agent will still stop or slow down the program.
33108 The in-process agent can interpret and execute Agent Expressions
33109 (@pxref{Agent Expressions}) during performing debugging operations. The
33110 agent expressions can be used for different purposes, such as collecting
33111 data in tracepoints, and condition evaluation in breakpoints.
33113 @anchor{Control Agent}
33114 You can control whether the in-process agent is used as an aid for
33115 debugging with the following commands:
33118 @kindex set agent on
33120 Causes the in-process agent to perform some operations on behalf of the
33121 debugger. Just which operations requested by the user will be done
33122 by the in-process agent depends on the its capabilities. For example,
33123 if you request to evaluate breakpoint conditions in the in-process agent,
33124 and the in-process agent has such capability as well, then breakpoint
33125 conditions will be evaluated in the in-process agent.
33127 @kindex set agent off
33128 @item set agent off
33129 Disables execution of debugging operations by the in-process agent. All
33130 of the operations will be performed by @value{GDBN}.
33134 Display the current setting of execution of debugging operations by
33135 the in-process agent.
33139 * In-Process Agent Protocol::
33142 @node In-Process Agent Protocol
33143 @section In-Process Agent Protocol
33144 @cindex in-process agent protocol
33146 The in-process agent is able to communicate with both @value{GDBN} and
33147 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
33148 used for communications between @value{GDBN} or GDBserver and the IPA.
33149 In general, @value{GDBN} or GDBserver sends commands
33150 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
33151 in-process agent replies back with the return result of the command, or
33152 some other information. The data sent to in-process agent is composed
33153 of primitive data types, such as 4-byte or 8-byte type, and composite
33154 types, which are called objects (@pxref{IPA Protocol Objects}).
33157 * IPA Protocol Objects::
33158 * IPA Protocol Commands::
33161 @node IPA Protocol Objects
33162 @subsection IPA Protocol Objects
33163 @cindex ipa protocol objects
33165 The commands sent to and results received from agent may contain some
33166 complex data types called @dfn{objects}.
33168 The in-process agent is running on the same machine with @value{GDBN}
33169 or GDBserver, so it doesn't have to handle as much differences between
33170 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
33171 However, there are still some differences of two ends in two processes:
33175 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
33176 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
33178 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
33179 GDBserver is compiled with one, and in-process agent is compiled with
33183 Here are the IPA Protocol Objects:
33187 agent expression object. It represents an agent expression
33188 (@pxref{Agent Expressions}).
33189 @anchor{agent expression object}
33191 tracepoint action object. It represents a tracepoint action
33192 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
33193 memory, static trace data and to evaluate expression.
33194 @anchor{tracepoint action object}
33196 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
33197 @anchor{tracepoint object}
33201 The following table describes important attributes of each IPA protocol
33204 @multitable @columnfractions .30 .20 .50
33205 @headitem Name @tab Size @tab Description
33206 @item @emph{agent expression object} @tab @tab
33207 @item length @tab 4 @tab length of bytes code
33208 @item byte code @tab @var{length} @tab contents of byte code
33209 @item @emph{tracepoint action for collecting memory} @tab @tab
33210 @item 'M' @tab 1 @tab type of tracepoint action
33211 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
33212 address of the lowest byte to collect, otherwise @var{addr} is the offset
33213 of @var{basereg} for memory collecting.
33214 @item len @tab 8 @tab length of memory for collecting
33215 @item basereg @tab 4 @tab the register number containing the starting
33216 memory address for collecting.
33217 @item @emph{tracepoint action for collecting registers} @tab @tab
33218 @item 'R' @tab 1 @tab type of tracepoint action
33219 @item @emph{tracepoint action for collecting static trace data} @tab @tab
33220 @item 'L' @tab 1 @tab type of tracepoint action
33221 @item @emph{tracepoint action for expression evaluation} @tab @tab
33222 @item 'X' @tab 1 @tab type of tracepoint action
33223 @item agent expression @tab length of @tab @ref{agent expression object}
33224 @item @emph{tracepoint object} @tab @tab
33225 @item number @tab 4 @tab number of tracepoint
33226 @item address @tab 8 @tab address of tracepoint inserted on
33227 @item type @tab 4 @tab type of tracepoint
33228 @item enabled @tab 1 @tab enable or disable of tracepoint
33229 @item step_count @tab 8 @tab step
33230 @item pass_count @tab 8 @tab pass
33231 @item numactions @tab 4 @tab number of tracepoint actions
33232 @item hit count @tab 8 @tab hit count
33233 @item trace frame usage @tab 8 @tab trace frame usage
33234 @item compiled_cond @tab 8 @tab compiled condition
33235 @item orig_size @tab 8 @tab orig size
33236 @item condition @tab 4 if condition is NULL otherwise length of
33237 @ref{agent expression object}
33238 @tab zero if condition is NULL, otherwise is
33239 @ref{agent expression object}
33240 @item actions @tab variable
33241 @tab numactions number of @ref{tracepoint action object}
33244 @node IPA Protocol Commands
33245 @subsection IPA Protocol Commands
33246 @cindex ipa protocol commands
33248 The spaces in each command are delimiters to ease reading this commands
33249 specification. They don't exist in real commands.
33253 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
33254 Installs a new fast tracepoint described by @var{tracepoint_object}
33255 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
33256 head of @dfn{jumppad}, which is used to jump to data collection routine
33261 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
33262 @var{target_address} is address of tracepoint in the inferior.
33263 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
33264 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
33265 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
33266 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
33273 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
33274 is about to kill inferiors.
33282 @item probe_marker_at:@var{address}
33283 Asks in-process agent to probe the marker at @var{address}.
33290 @item unprobe_marker_at:@var{address}
33291 Asks in-process agent to unprobe the marker at @var{address}.
33295 @chapter Reporting Bugs in @value{GDBN}
33296 @cindex bugs in @value{GDBN}
33297 @cindex reporting bugs in @value{GDBN}
33299 Your bug reports play an essential role in making @value{GDBN} reliable.
33301 Reporting a bug may help you by bringing a solution to your problem, or it
33302 may not. But in any case the principal function of a bug report is to help
33303 the entire community by making the next version of @value{GDBN} work better. Bug
33304 reports are your contribution to the maintenance of @value{GDBN}.
33306 In order for a bug report to serve its purpose, you must include the
33307 information that enables us to fix the bug.
33310 * Bug Criteria:: Have you found a bug?
33311 * Bug Reporting:: How to report bugs
33315 @section Have You Found a Bug?
33316 @cindex bug criteria
33318 If you are not sure whether you have found a bug, here are some guidelines:
33321 @cindex fatal signal
33322 @cindex debugger crash
33323 @cindex crash of debugger
33325 If the debugger gets a fatal signal, for any input whatever, that is a
33326 @value{GDBN} bug. Reliable debuggers never crash.
33328 @cindex error on valid input
33330 If @value{GDBN} produces an error message for valid input, that is a
33331 bug. (Note that if you're cross debugging, the problem may also be
33332 somewhere in the connection to the target.)
33334 @cindex invalid input
33336 If @value{GDBN} does not produce an error message for invalid input,
33337 that is a bug. However, you should note that your idea of
33338 ``invalid input'' might be our idea of ``an extension'' or ``support
33339 for traditional practice''.
33342 If you are an experienced user of debugging tools, your suggestions
33343 for improvement of @value{GDBN} are welcome in any case.
33346 @node Bug Reporting
33347 @section How to Report Bugs
33348 @cindex bug reports
33349 @cindex @value{GDBN} bugs, reporting
33351 A number of companies and individuals offer support for @sc{gnu} products.
33352 If you obtained @value{GDBN} from a support organization, we recommend you
33353 contact that organization first.
33355 You can find contact information for many support companies and
33356 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
33358 @c should add a web page ref...
33361 @ifset BUGURL_DEFAULT
33362 In any event, we also recommend that you submit bug reports for
33363 @value{GDBN}. The preferred method is to submit them directly using
33364 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
33365 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
33368 @strong{Do not send bug reports to @samp{info-gdb}, or to
33369 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
33370 not want to receive bug reports. Those that do have arranged to receive
33373 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
33374 serves as a repeater. The mailing list and the newsgroup carry exactly
33375 the same messages. Often people think of posting bug reports to the
33376 newsgroup instead of mailing them. This appears to work, but it has one
33377 problem which can be crucial: a newsgroup posting often lacks a mail
33378 path back to the sender. Thus, if we need to ask for more information,
33379 we may be unable to reach you. For this reason, it is better to send
33380 bug reports to the mailing list.
33382 @ifclear BUGURL_DEFAULT
33383 In any event, we also recommend that you submit bug reports for
33384 @value{GDBN} to @value{BUGURL}.
33388 The fundamental principle of reporting bugs usefully is this:
33389 @strong{report all the facts}. If you are not sure whether to state a
33390 fact or leave it out, state it!
33392 Often people omit facts because they think they know what causes the
33393 problem and assume that some details do not matter. Thus, you might
33394 assume that the name of the variable you use in an example does not matter.
33395 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
33396 stray memory reference which happens to fetch from the location where that
33397 name is stored in memory; perhaps, if the name were different, the contents
33398 of that location would fool the debugger into doing the right thing despite
33399 the bug. Play it safe and give a specific, complete example. That is the
33400 easiest thing for you to do, and the most helpful.
33402 Keep in mind that the purpose of a bug report is to enable us to fix the
33403 bug. It may be that the bug has been reported previously, but neither
33404 you nor we can know that unless your bug report is complete and
33407 Sometimes people give a few sketchy facts and ask, ``Does this ring a
33408 bell?'' Those bug reports are useless, and we urge everyone to
33409 @emph{refuse to respond to them} except to chide the sender to report
33412 To enable us to fix the bug, you should include all these things:
33416 The version of @value{GDBN}. @value{GDBN} announces it if you start
33417 with no arguments; you can also print it at any time using @code{show
33420 Without this, we will not know whether there is any point in looking for
33421 the bug in the current version of @value{GDBN}.
33424 The type of machine you are using, and the operating system name and
33428 The details of the @value{GDBN} build-time configuration.
33429 @value{GDBN} shows these details if you invoke it with the
33430 @option{--configuration} command-line option, or if you type
33431 @code{show configuration} at @value{GDBN}'s prompt.
33434 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
33435 ``@value{GCC}--2.8.1''.
33438 What compiler (and its version) was used to compile the program you are
33439 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
33440 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
33441 to get this information; for other compilers, see the documentation for
33445 The command arguments you gave the compiler to compile your example and
33446 observe the bug. For example, did you use @samp{-O}? To guarantee
33447 you will not omit something important, list them all. A copy of the
33448 Makefile (or the output from make) is sufficient.
33450 If we were to try to guess the arguments, we would probably guess wrong
33451 and then we might not encounter the bug.
33454 A complete input script, and all necessary source files, that will
33458 A description of what behavior you observe that you believe is
33459 incorrect. For example, ``It gets a fatal signal.''
33461 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
33462 will certainly notice it. But if the bug is incorrect output, we might
33463 not notice unless it is glaringly wrong. You might as well not give us
33464 a chance to make a mistake.
33466 Even if the problem you experience is a fatal signal, you should still
33467 say so explicitly. Suppose something strange is going on, such as, your
33468 copy of @value{GDBN} is out of synch, or you have encountered a bug in
33469 the C library on your system. (This has happened!) Your copy might
33470 crash and ours would not. If you told us to expect a crash, then when
33471 ours fails to crash, we would know that the bug was not happening for
33472 us. If you had not told us to expect a crash, then we would not be able
33473 to draw any conclusion from our observations.
33476 @cindex recording a session script
33477 To collect all this information, you can use a session recording program
33478 such as @command{script}, which is available on many Unix systems.
33479 Just run your @value{GDBN} session inside @command{script} and then
33480 include the @file{typescript} file with your bug report.
33482 Another way to record a @value{GDBN} session is to run @value{GDBN}
33483 inside Emacs and then save the entire buffer to a file.
33486 If you wish to suggest changes to the @value{GDBN} source, send us context
33487 diffs. If you even discuss something in the @value{GDBN} source, refer to
33488 it by context, not by line number.
33490 The line numbers in our development sources will not match those in your
33491 sources. Your line numbers would convey no useful information to us.
33495 Here are some things that are not necessary:
33499 A description of the envelope of the bug.
33501 Often people who encounter a bug spend a lot of time investigating
33502 which changes to the input file will make the bug go away and which
33503 changes will not affect it.
33505 This is often time consuming and not very useful, because the way we
33506 will find the bug is by running a single example under the debugger
33507 with breakpoints, not by pure deduction from a series of examples.
33508 We recommend that you save your time for something else.
33510 Of course, if you can find a simpler example to report @emph{instead}
33511 of the original one, that is a convenience for us. Errors in the
33512 output will be easier to spot, running under the debugger will take
33513 less time, and so on.
33515 However, simplification is not vital; if you do not want to do this,
33516 report the bug anyway and send us the entire test case you used.
33519 A patch for the bug.
33521 A patch for the bug does help us if it is a good one. But do not omit
33522 the necessary information, such as the test case, on the assumption that
33523 a patch is all we need. We might see problems with your patch and decide
33524 to fix the problem another way, or we might not understand it at all.
33526 Sometimes with a program as complicated as @value{GDBN} it is very hard to
33527 construct an example that will make the program follow a certain path
33528 through the code. If you do not send us the example, we will not be able
33529 to construct one, so we will not be able to verify that the bug is fixed.
33531 And if we cannot understand what bug you are trying to fix, or why your
33532 patch should be an improvement, we will not install it. A test case will
33533 help us to understand.
33536 A guess about what the bug is or what it depends on.
33538 Such guesses are usually wrong. Even we cannot guess right about such
33539 things without first using the debugger to find the facts.
33542 @c The readline documentation is distributed with the readline code
33543 @c and consists of the two following files:
33546 @c Use -I with makeinfo to point to the appropriate directory,
33547 @c environment var TEXINPUTS with TeX.
33548 @ifclear SYSTEM_READLINE
33549 @include rluser.texi
33550 @include hsuser.texi
33554 @appendix In Memoriam
33556 The @value{GDBN} project mourns the loss of the following long-time
33561 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
33562 to Free Software in general. Outside of @value{GDBN}, he was known in
33563 the Amiga world for his series of Fish Disks, and the GeekGadget project.
33565 @item Michael Snyder
33566 Michael was one of the Global Maintainers of the @value{GDBN} project,
33567 with contributions recorded as early as 1996, until 2011. In addition
33568 to his day to day participation, he was a large driving force behind
33569 adding Reverse Debugging to @value{GDBN}.
33572 Beyond their technical contributions to the project, they were also
33573 enjoyable members of the Free Software Community. We will miss them.
33575 @node Formatting Documentation
33576 @appendix Formatting Documentation
33578 @cindex @value{GDBN} reference card
33579 @cindex reference card
33580 The @value{GDBN} 4 release includes an already-formatted reference card, ready
33581 for printing with PostScript or Ghostscript, in the @file{gdb}
33582 subdirectory of the main source directory@footnote{In
33583 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
33584 release.}. If you can use PostScript or Ghostscript with your printer,
33585 you can print the reference card immediately with @file{refcard.ps}.
33587 The release also includes the source for the reference card. You
33588 can format it, using @TeX{}, by typing:
33594 The @value{GDBN} reference card is designed to print in @dfn{landscape}
33595 mode on US ``letter'' size paper;
33596 that is, on a sheet 11 inches wide by 8.5 inches
33597 high. You will need to specify this form of printing as an option to
33598 your @sc{dvi} output program.
33600 @cindex documentation
33602 All the documentation for @value{GDBN} comes as part of the machine-readable
33603 distribution. The documentation is written in Texinfo format, which is
33604 a documentation system that uses a single source file to produce both
33605 on-line information and a printed manual. You can use one of the Info
33606 formatting commands to create the on-line version of the documentation
33607 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
33609 @value{GDBN} includes an already formatted copy of the on-line Info
33610 version of this manual in the @file{gdb} subdirectory. The main Info
33611 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
33612 subordinate files matching @samp{gdb.info*} in the same directory. If
33613 necessary, you can print out these files, or read them with any editor;
33614 but they are easier to read using the @code{info} subsystem in @sc{gnu}
33615 Emacs or the standalone @code{info} program, available as part of the
33616 @sc{gnu} Texinfo distribution.
33618 If you want to format these Info files yourself, you need one of the
33619 Info formatting programs, such as @code{texinfo-format-buffer} or
33622 If you have @code{makeinfo} installed, and are in the top level
33623 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
33624 version @value{GDBVN}), you can make the Info file by typing:
33631 If you want to typeset and print copies of this manual, you need @TeX{},
33632 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
33633 Texinfo definitions file.
33635 @TeX{} is a typesetting program; it does not print files directly, but
33636 produces output files called @sc{dvi} files. To print a typeset
33637 document, you need a program to print @sc{dvi} files. If your system
33638 has @TeX{} installed, chances are it has such a program. The precise
33639 command to use depends on your system; @kbd{lpr -d} is common; another
33640 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
33641 require a file name without any extension or a @samp{.dvi} extension.
33643 @TeX{} also requires a macro definitions file called
33644 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
33645 written in Texinfo format. On its own, @TeX{} cannot either read or
33646 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
33647 and is located in the @file{gdb-@var{version-number}/texinfo}
33650 If you have @TeX{} and a @sc{dvi} printer program installed, you can
33651 typeset and print this manual. First switch to the @file{gdb}
33652 subdirectory of the main source directory (for example, to
33653 @file{gdb-@value{GDBVN}/gdb}) and type:
33659 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
33661 @node Installing GDB
33662 @appendix Installing @value{GDBN}
33663 @cindex installation
33666 * Requirements:: Requirements for building @value{GDBN}
33667 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
33668 * Separate Objdir:: Compiling @value{GDBN} in another directory
33669 * Config Names:: Specifying names for hosts and targets
33670 * Configure Options:: Summary of options for configure
33671 * System-wide configuration:: Having a system-wide init file
33675 @section Requirements for Building @value{GDBN}
33676 @cindex building @value{GDBN}, requirements for
33678 Building @value{GDBN} requires various tools and packages to be available.
33679 Other packages will be used only if they are found.
33681 @heading Tools/Packages Necessary for Building @value{GDBN}
33683 @item ISO C90 compiler
33684 @value{GDBN} is written in ISO C90. It should be buildable with any
33685 working C90 compiler, e.g.@: GCC.
33689 @heading Tools/Packages Optional for Building @value{GDBN}
33693 @value{GDBN} can use the Expat XML parsing library. This library may be
33694 included with your operating system distribution; if it is not, you
33695 can get the latest version from @url{http://expat.sourceforge.net}.
33696 The @file{configure} script will search for this library in several
33697 standard locations; if it is installed in an unusual path, you can
33698 use the @option{--with-libexpat-prefix} option to specify its location.
33704 Remote protocol memory maps (@pxref{Memory Map Format})
33706 Target descriptions (@pxref{Target Descriptions})
33708 Remote shared library lists (@xref{Library List Format},
33709 or alternatively @pxref{Library List Format for SVR4 Targets})
33711 MS-Windows shared libraries (@pxref{Shared Libraries})
33713 Traceframe info (@pxref{Traceframe Info Format})
33715 Branch trace (@pxref{Branch Trace Format},
33716 @pxref{Branch Trace Configuration Format})
33720 @cindex compressed debug sections
33721 @value{GDBN} will use the @samp{zlib} library, if available, to read
33722 compressed debug sections. Some linkers, such as GNU gold, are capable
33723 of producing binaries with compressed debug sections. If @value{GDBN}
33724 is compiled with @samp{zlib}, it will be able to read the debug
33725 information in such binaries.
33727 The @samp{zlib} library is likely included with your operating system
33728 distribution; if it is not, you can get the latest version from
33729 @url{http://zlib.net}.
33732 @value{GDBN}'s features related to character sets (@pxref{Character
33733 Sets}) require a functioning @code{iconv} implementation. If you are
33734 on a GNU system, then this is provided by the GNU C Library. Some
33735 other systems also provide a working @code{iconv}.
33737 If @value{GDBN} is using the @code{iconv} program which is installed
33738 in a non-standard place, you will need to tell @value{GDBN} where to find it.
33739 This is done with @option{--with-iconv-bin} which specifies the
33740 directory that contains the @code{iconv} program.
33742 On systems without @code{iconv}, you can install GNU Libiconv. If you
33743 have previously installed Libiconv, you can use the
33744 @option{--with-libiconv-prefix} option to configure.
33746 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
33747 arrange to build Libiconv if a directory named @file{libiconv} appears
33748 in the top-most source directory. If Libiconv is built this way, and
33749 if the operating system does not provide a suitable @code{iconv}
33750 implementation, then the just-built library will automatically be used
33751 by @value{GDBN}. One easy way to set this up is to download GNU
33752 Libiconv, unpack it, and then rename the directory holding the
33753 Libiconv source code to @samp{libiconv}.
33756 @node Running Configure
33757 @section Invoking the @value{GDBN} @file{configure} Script
33758 @cindex configuring @value{GDBN}
33759 @value{GDBN} comes with a @file{configure} script that automates the process
33760 of preparing @value{GDBN} for installation; you can then use @code{make} to
33761 build the @code{gdb} program.
33763 @c irrelevant in info file; it's as current as the code it lives with.
33764 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
33765 look at the @file{README} file in the sources; we may have improved the
33766 installation procedures since publishing this manual.}
33769 The @value{GDBN} distribution includes all the source code you need for
33770 @value{GDBN} in a single directory, whose name is usually composed by
33771 appending the version number to @samp{gdb}.
33773 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
33774 @file{gdb-@value{GDBVN}} directory. That directory contains:
33777 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
33778 script for configuring @value{GDBN} and all its supporting libraries
33780 @item gdb-@value{GDBVN}/gdb
33781 the source specific to @value{GDBN} itself
33783 @item gdb-@value{GDBVN}/bfd
33784 source for the Binary File Descriptor library
33786 @item gdb-@value{GDBVN}/include
33787 @sc{gnu} include files
33789 @item gdb-@value{GDBVN}/libiberty
33790 source for the @samp{-liberty} free software library
33792 @item gdb-@value{GDBVN}/opcodes
33793 source for the library of opcode tables and disassemblers
33795 @item gdb-@value{GDBVN}/readline
33796 source for the @sc{gnu} command-line interface
33798 @item gdb-@value{GDBVN}/glob
33799 source for the @sc{gnu} filename pattern-matching subroutine
33801 @item gdb-@value{GDBVN}/mmalloc
33802 source for the @sc{gnu} memory-mapped malloc package
33805 The simplest way to configure and build @value{GDBN} is to run @file{configure}
33806 from the @file{gdb-@var{version-number}} source directory, which in
33807 this example is the @file{gdb-@value{GDBVN}} directory.
33809 First switch to the @file{gdb-@var{version-number}} source directory
33810 if you are not already in it; then run @file{configure}. Pass the
33811 identifier for the platform on which @value{GDBN} will run as an
33817 cd gdb-@value{GDBVN}
33818 ./configure @var{host}
33823 where @var{host} is an identifier such as @samp{sun4} or
33824 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
33825 (You can often leave off @var{host}; @file{configure} tries to guess the
33826 correct value by examining your system.)
33828 Running @samp{configure @var{host}} and then running @code{make} builds the
33829 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
33830 libraries, then @code{gdb} itself. The configured source files, and the
33831 binaries, are left in the corresponding source directories.
33834 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
33835 system does not recognize this automatically when you run a different
33836 shell, you may need to run @code{sh} on it explicitly:
33839 sh configure @var{host}
33842 If you run @file{configure} from a directory that contains source
33843 directories for multiple libraries or programs, such as the
33844 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
33846 creates configuration files for every directory level underneath (unless
33847 you tell it not to, with the @samp{--norecursion} option).
33849 You should run the @file{configure} script from the top directory in the
33850 source tree, the @file{gdb-@var{version-number}} directory. If you run
33851 @file{configure} from one of the subdirectories, you will configure only
33852 that subdirectory. That is usually not what you want. In particular,
33853 if you run the first @file{configure} from the @file{gdb} subdirectory
33854 of the @file{gdb-@var{version-number}} directory, you will omit the
33855 configuration of @file{bfd}, @file{readline}, and other sibling
33856 directories of the @file{gdb} subdirectory. This leads to build errors
33857 about missing include files such as @file{bfd/bfd.h}.
33859 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
33860 However, you should make sure that the shell on your path (named by
33861 the @samp{SHELL} environment variable) is publicly readable. Remember
33862 that @value{GDBN} uses the shell to start your program---some systems refuse to
33863 let @value{GDBN} debug child processes whose programs are not readable.
33865 @node Separate Objdir
33866 @section Compiling @value{GDBN} in Another Directory
33868 If you want to run @value{GDBN} versions for several host or target machines,
33869 you need a different @code{gdb} compiled for each combination of
33870 host and target. @file{configure} is designed to make this easy by
33871 allowing you to generate each configuration in a separate subdirectory,
33872 rather than in the source directory. If your @code{make} program
33873 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
33874 @code{make} in each of these directories builds the @code{gdb}
33875 program specified there.
33877 To build @code{gdb} in a separate directory, run @file{configure}
33878 with the @samp{--srcdir} option to specify where to find the source.
33879 (You also need to specify a path to find @file{configure}
33880 itself from your working directory. If the path to @file{configure}
33881 would be the same as the argument to @samp{--srcdir}, you can leave out
33882 the @samp{--srcdir} option; it is assumed.)
33884 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
33885 separate directory for a Sun 4 like this:
33889 cd gdb-@value{GDBVN}
33892 ../gdb-@value{GDBVN}/configure sun4
33897 When @file{configure} builds a configuration using a remote source
33898 directory, it creates a tree for the binaries with the same structure
33899 (and using the same names) as the tree under the source directory. In
33900 the example, you'd find the Sun 4 library @file{libiberty.a} in the
33901 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
33902 @file{gdb-sun4/gdb}.
33904 Make sure that your path to the @file{configure} script has just one
33905 instance of @file{gdb} in it. If your path to @file{configure} looks
33906 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
33907 one subdirectory of @value{GDBN}, not the whole package. This leads to
33908 build errors about missing include files such as @file{bfd/bfd.h}.
33910 One popular reason to build several @value{GDBN} configurations in separate
33911 directories is to configure @value{GDBN} for cross-compiling (where
33912 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
33913 programs that run on another machine---the @dfn{target}).
33914 You specify a cross-debugging target by
33915 giving the @samp{--target=@var{target}} option to @file{configure}.
33917 When you run @code{make} to build a program or library, you must run
33918 it in a configured directory---whatever directory you were in when you
33919 called @file{configure} (or one of its subdirectories).
33921 The @code{Makefile} that @file{configure} generates in each source
33922 directory also runs recursively. If you type @code{make} in a source
33923 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
33924 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
33925 will build all the required libraries, and then build GDB.
33927 When you have multiple hosts or targets configured in separate
33928 directories, you can run @code{make} on them in parallel (for example,
33929 if they are NFS-mounted on each of the hosts); they will not interfere
33933 @section Specifying Names for Hosts and Targets
33935 The specifications used for hosts and targets in the @file{configure}
33936 script are based on a three-part naming scheme, but some short predefined
33937 aliases are also supported. The full naming scheme encodes three pieces
33938 of information in the following pattern:
33941 @var{architecture}-@var{vendor}-@var{os}
33944 For example, you can use the alias @code{sun4} as a @var{host} argument,
33945 or as the value for @var{target} in a @code{--target=@var{target}}
33946 option. The equivalent full name is @samp{sparc-sun-sunos4}.
33948 The @file{configure} script accompanying @value{GDBN} does not provide
33949 any query facility to list all supported host and target names or
33950 aliases. @file{configure} calls the Bourne shell script
33951 @code{config.sub} to map abbreviations to full names; you can read the
33952 script, if you wish, or you can use it to test your guesses on
33953 abbreviations---for example:
33956 % sh config.sub i386-linux
33958 % sh config.sub alpha-linux
33959 alpha-unknown-linux-gnu
33960 % sh config.sub hp9k700
33962 % sh config.sub sun4
33963 sparc-sun-sunos4.1.1
33964 % sh config.sub sun3
33965 m68k-sun-sunos4.1.1
33966 % sh config.sub i986v
33967 Invalid configuration `i986v': machine `i986v' not recognized
33971 @code{config.sub} is also distributed in the @value{GDBN} source
33972 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
33974 @node Configure Options
33975 @section @file{configure} Options
33977 Here is a summary of the @file{configure} options and arguments that
33978 are most often useful for building @value{GDBN}. @file{configure} also has
33979 several other options not listed here. @inforef{What Configure
33980 Does,,configure.info}, for a full explanation of @file{configure}.
33983 configure @r{[}--help@r{]}
33984 @r{[}--prefix=@var{dir}@r{]}
33985 @r{[}--exec-prefix=@var{dir}@r{]}
33986 @r{[}--srcdir=@var{dirname}@r{]}
33987 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
33988 @r{[}--target=@var{target}@r{]}
33993 You may introduce options with a single @samp{-} rather than
33994 @samp{--} if you prefer; but you may abbreviate option names if you use
33999 Display a quick summary of how to invoke @file{configure}.
34001 @item --prefix=@var{dir}
34002 Configure the source to install programs and files under directory
34005 @item --exec-prefix=@var{dir}
34006 Configure the source to install programs under directory
34009 @c avoid splitting the warning from the explanation:
34011 @item --srcdir=@var{dirname}
34012 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
34013 @code{make} that implements the @code{VPATH} feature.}@*
34014 Use this option to make configurations in directories separate from the
34015 @value{GDBN} source directories. Among other things, you can use this to
34016 build (or maintain) several configurations simultaneously, in separate
34017 directories. @file{configure} writes configuration-specific files in
34018 the current directory, but arranges for them to use the source in the
34019 directory @var{dirname}. @file{configure} creates directories under
34020 the working directory in parallel to the source directories below
34023 @item --norecursion
34024 Configure only the directory level where @file{configure} is executed; do not
34025 propagate configuration to subdirectories.
34027 @item --target=@var{target}
34028 Configure @value{GDBN} for cross-debugging programs running on the specified
34029 @var{target}. Without this option, @value{GDBN} is configured to debug
34030 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
34032 There is no convenient way to generate a list of all available targets.
34034 @item @var{host} @dots{}
34035 Configure @value{GDBN} to run on the specified @var{host}.
34037 There is no convenient way to generate a list of all available hosts.
34040 There are many other options available as well, but they are generally
34041 needed for special purposes only.
34043 @node System-wide configuration
34044 @section System-wide configuration and settings
34045 @cindex system-wide init file
34047 @value{GDBN} can be configured to have a system-wide init file;
34048 this file will be read and executed at startup (@pxref{Startup, , What
34049 @value{GDBN} does during startup}).
34051 Here is the corresponding configure option:
34054 @item --with-system-gdbinit=@var{file}
34055 Specify that the default location of the system-wide init file is
34059 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
34060 it may be subject to relocation. Two possible cases:
34064 If the default location of this init file contains @file{$prefix},
34065 it will be subject to relocation. Suppose that the configure options
34066 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
34067 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
34068 init file is looked for as @file{$install/etc/gdbinit} instead of
34069 @file{$prefix/etc/gdbinit}.
34072 By contrast, if the default location does not contain the prefix,
34073 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
34074 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
34075 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
34076 wherever @value{GDBN} is installed.
34079 If the configured location of the system-wide init file (as given by the
34080 @option{--with-system-gdbinit} option at configure time) is in the
34081 data-directory (as specified by @option{--with-gdb-datadir} at configure
34082 time) or in one of its subdirectories, then @value{GDBN} will look for the
34083 system-wide init file in the directory specified by the
34084 @option{--data-directory} command-line option.
34085 Note that the system-wide init file is only read once, during @value{GDBN}
34086 initialization. If the data-directory is changed after @value{GDBN} has
34087 started with the @code{set data-directory} command, the file will not be
34091 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
34094 @node System-wide Configuration Scripts
34095 @subsection Installed System-wide Configuration Scripts
34096 @cindex system-wide configuration scripts
34098 The @file{system-gdbinit} directory, located inside the data-directory
34099 (as specified by @option{--with-gdb-datadir} at configure time) contains
34100 a number of scripts which can be used as system-wide init files. To
34101 automatically source those scripts at startup, @value{GDBN} should be
34102 configured with @option{--with-system-gdbinit}. Otherwise, any user
34103 should be able to source them by hand as needed.
34105 The following scripts are currently available:
34108 @item @file{elinos.py}
34110 @cindex ELinOS system-wide configuration script
34111 This script is useful when debugging a program on an ELinOS target.
34112 It takes advantage of the environment variables defined in a standard
34113 ELinOS environment in order to determine the location of the system
34114 shared libraries, and then sets the @samp{solib-absolute-prefix}
34115 and @samp{solib-search-path} variables appropriately.
34117 @item @file{wrs-linux.py}
34118 @pindex wrs-linux.py
34119 @cindex Wind River Linux system-wide configuration script
34120 This script is useful when debugging a program on a target running
34121 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
34122 the host-side sysroot used by the target system.
34126 @node Maintenance Commands
34127 @appendix Maintenance Commands
34128 @cindex maintenance commands
34129 @cindex internal commands
34131 In addition to commands intended for @value{GDBN} users, @value{GDBN}
34132 includes a number of commands intended for @value{GDBN} developers,
34133 that are not documented elsewhere in this manual. These commands are
34134 provided here for reference. (For commands that turn on debugging
34135 messages, see @ref{Debugging Output}.)
34138 @kindex maint agent
34139 @kindex maint agent-eval
34140 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
34141 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
34142 Translate the given @var{expression} into remote agent bytecodes.
34143 This command is useful for debugging the Agent Expression mechanism
34144 (@pxref{Agent Expressions}). The @samp{agent} version produces an
34145 expression useful for data collection, such as by tracepoints, while
34146 @samp{maint agent-eval} produces an expression that evaluates directly
34147 to a result. For instance, a collection expression for @code{globa +
34148 globb} will include bytecodes to record four bytes of memory at each
34149 of the addresses of @code{globa} and @code{globb}, while discarding
34150 the result of the addition, while an evaluation expression will do the
34151 addition and return the sum.
34152 If @code{-at} is given, generate remote agent bytecode for @var{location}.
34153 If not, generate remote agent bytecode for current frame PC address.
34155 @kindex maint agent-printf
34156 @item maint agent-printf @var{format},@var{expr},...
34157 Translate the given format string and list of argument expressions
34158 into remote agent bytecodes and display them as a disassembled list.
34159 This command is useful for debugging the agent version of dynamic
34160 printf (@pxref{Dynamic Printf}).
34162 @kindex maint info breakpoints
34163 @item @anchor{maint info breakpoints}maint info breakpoints
34164 Using the same format as @samp{info breakpoints}, display both the
34165 breakpoints you've set explicitly, and those @value{GDBN} is using for
34166 internal purposes. Internal breakpoints are shown with negative
34167 breakpoint numbers. The type column identifies what kind of breakpoint
34172 Normal, explicitly set breakpoint.
34175 Normal, explicitly set watchpoint.
34178 Internal breakpoint, used to handle correctly stepping through
34179 @code{longjmp} calls.
34181 @item longjmp resume
34182 Internal breakpoint at the target of a @code{longjmp}.
34185 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
34188 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
34191 Shared library events.
34195 @kindex maint info btrace
34196 @item maint info btrace
34197 Pint information about raw branch tracing data.
34199 @kindex maint btrace packet-history
34200 @item maint btrace packet-history
34201 Print the raw branch trace packets that are used to compute the
34202 execution history for the @samp{record btrace} command. Both the
34203 information and the format in which it is printed depend on the btrace
34208 For the BTS recording format, print a list of blocks of sequential
34209 code. For each block, the following information is printed:
34213 Newer blocks have higher numbers. The oldest block has number zero.
34214 @item Lowest @samp{PC}
34215 @item Highest @samp{PC}
34219 For the Intel(R) Processor Trace recording format, print a list of
34220 Intel(R) Processor Trace packets. For each packet, the following
34221 information is printed:
34224 @item Packet number
34225 Newer packets have higher numbers. The oldest packet has number zero.
34227 The packet's offset in the trace stream.
34228 @item Packet opcode and payload
34232 @kindex maint btrace clear-packet-history
34233 @item maint btrace clear-packet-history
34234 Discards the cached packet history printed by the @samp{maint btrace
34235 packet-history} command. The history will be computed again when
34238 @kindex maint btrace clear
34239 @item maint btrace clear
34240 Discard the branch trace data. The data will be fetched anew and the
34241 branch trace will be recomputed when needed.
34243 This implicitly truncates the branch trace to a single branch trace
34244 buffer. When updating branch trace incrementally, the branch trace
34245 available to @value{GDBN} may be bigger than a single branch trace
34248 @kindex maint set btrace pt skip-pad
34249 @item maint set btrace pt skip-pad
34250 @kindex maint show btrace pt skip-pad
34251 @item maint show btrace pt skip-pad
34252 Control whether @value{GDBN} will skip PAD packets when computing the
34255 @kindex set displaced-stepping
34256 @kindex show displaced-stepping
34257 @cindex displaced stepping support
34258 @cindex out-of-line single-stepping
34259 @item set displaced-stepping
34260 @itemx show displaced-stepping
34261 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
34262 if the target supports it. Displaced stepping is a way to single-step
34263 over breakpoints without removing them from the inferior, by executing
34264 an out-of-line copy of the instruction that was originally at the
34265 breakpoint location. It is also known as out-of-line single-stepping.
34268 @item set displaced-stepping on
34269 If the target architecture supports it, @value{GDBN} will use
34270 displaced stepping to step over breakpoints.
34272 @item set displaced-stepping off
34273 @value{GDBN} will not use displaced stepping to step over breakpoints,
34274 even if such is supported by the target architecture.
34276 @cindex non-stop mode, and @samp{set displaced-stepping}
34277 @item set displaced-stepping auto
34278 This is the default mode. @value{GDBN} will use displaced stepping
34279 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
34280 architecture supports displaced stepping.
34283 @kindex maint check-psymtabs
34284 @item maint check-psymtabs
34285 Check the consistency of currently expanded psymtabs versus symtabs.
34286 Use this to check, for example, whether a symbol is in one but not the other.
34288 @kindex maint check-symtabs
34289 @item maint check-symtabs
34290 Check the consistency of currently expanded symtabs.
34292 @kindex maint expand-symtabs
34293 @item maint expand-symtabs [@var{regexp}]
34294 Expand symbol tables.
34295 If @var{regexp} is specified, only expand symbol tables for file
34296 names matching @var{regexp}.
34298 @kindex maint set catch-demangler-crashes
34299 @kindex maint show catch-demangler-crashes
34300 @cindex demangler crashes
34301 @item maint set catch-demangler-crashes [on|off]
34302 @itemx maint show catch-demangler-crashes
34303 Control whether @value{GDBN} should attempt to catch crashes in the
34304 symbol name demangler. The default is to attempt to catch crashes.
34305 If enabled, the first time a crash is caught, a core file is created,
34306 the offending symbol is displayed and the user is presented with the
34307 option to terminate the current session.
34309 @kindex maint cplus first_component
34310 @item maint cplus first_component @var{name}
34311 Print the first C@t{++} class/namespace component of @var{name}.
34313 @kindex maint cplus namespace
34314 @item maint cplus namespace
34315 Print the list of possible C@t{++} namespaces.
34317 @kindex maint deprecate
34318 @kindex maint undeprecate
34319 @cindex deprecated commands
34320 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
34321 @itemx maint undeprecate @var{command}
34322 Deprecate or undeprecate the named @var{command}. Deprecated commands
34323 cause @value{GDBN} to issue a warning when you use them. The optional
34324 argument @var{replacement} says which newer command should be used in
34325 favor of the deprecated one; if it is given, @value{GDBN} will mention
34326 the replacement as part of the warning.
34328 @kindex maint dump-me
34329 @item maint dump-me
34330 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
34331 Cause a fatal signal in the debugger and force it to dump its core.
34332 This is supported only on systems which support aborting a program
34333 with the @code{SIGQUIT} signal.
34335 @kindex maint internal-error
34336 @kindex maint internal-warning
34337 @kindex maint demangler-warning
34338 @cindex demangler crashes
34339 @item maint internal-error @r{[}@var{message-text}@r{]}
34340 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
34341 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
34343 Cause @value{GDBN} to call the internal function @code{internal_error},
34344 @code{internal_warning} or @code{demangler_warning} and hence behave
34345 as though an internal problem has been detected. In addition to
34346 reporting the internal problem, these functions give the user the
34347 opportunity to either quit @value{GDBN} or (for @code{internal_error}
34348 and @code{internal_warning}) create a core file of the current
34349 @value{GDBN} session.
34351 These commands take an optional parameter @var{message-text} that is
34352 used as the text of the error or warning message.
34354 Here's an example of using @code{internal-error}:
34357 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
34358 @dots{}/maint.c:121: internal-error: testing, 1, 2
34359 A problem internal to GDB has been detected. Further
34360 debugging may prove unreliable.
34361 Quit this debugging session? (y or n) @kbd{n}
34362 Create a core file? (y or n) @kbd{n}
34366 @cindex @value{GDBN} internal error
34367 @cindex internal errors, control of @value{GDBN} behavior
34368 @cindex demangler crashes
34370 @kindex maint set internal-error
34371 @kindex maint show internal-error
34372 @kindex maint set internal-warning
34373 @kindex maint show internal-warning
34374 @kindex maint set demangler-warning
34375 @kindex maint show demangler-warning
34376 @item maint set internal-error @var{action} [ask|yes|no]
34377 @itemx maint show internal-error @var{action}
34378 @itemx maint set internal-warning @var{action} [ask|yes|no]
34379 @itemx maint show internal-warning @var{action}
34380 @itemx maint set demangler-warning @var{action} [ask|yes|no]
34381 @itemx maint show demangler-warning @var{action}
34382 When @value{GDBN} reports an internal problem (error or warning) it
34383 gives the user the opportunity to both quit @value{GDBN} and create a
34384 core file of the current @value{GDBN} session. These commands let you
34385 override the default behaviour for each particular @var{action},
34386 described in the table below.
34390 You can specify that @value{GDBN} should always (yes) or never (no)
34391 quit. The default is to ask the user what to do.
34394 You can specify that @value{GDBN} should always (yes) or never (no)
34395 create a core file. The default is to ask the user what to do. Note
34396 that there is no @code{corefile} option for @code{demangler-warning}:
34397 demangler warnings always create a core file and this cannot be
34401 @kindex maint packet
34402 @item maint packet @var{text}
34403 If @value{GDBN} is talking to an inferior via the serial protocol,
34404 then this command sends the string @var{text} to the inferior, and
34405 displays the response packet. @value{GDBN} supplies the initial
34406 @samp{$} character, the terminating @samp{#} character, and the
34409 @kindex maint print architecture
34410 @item maint print architecture @r{[}@var{file}@r{]}
34411 Print the entire architecture configuration. The optional argument
34412 @var{file} names the file where the output goes.
34414 @kindex maint print c-tdesc
34415 @item maint print c-tdesc
34416 Print the current target description (@pxref{Target Descriptions}) as
34417 a C source file. The created source file can be used in @value{GDBN}
34418 when an XML parser is not available to parse the description.
34420 @kindex maint print dummy-frames
34421 @item maint print dummy-frames
34422 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
34425 (@value{GDBP}) @kbd{b add}
34427 (@value{GDBP}) @kbd{print add(2,3)}
34428 Breakpoint 2, add (a=2, b=3) at @dots{}
34430 The program being debugged stopped while in a function called from GDB.
34432 (@value{GDBP}) @kbd{maint print dummy-frames}
34433 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
34437 Takes an optional file parameter.
34439 @kindex maint print registers
34440 @kindex maint print raw-registers
34441 @kindex maint print cooked-registers
34442 @kindex maint print register-groups
34443 @kindex maint print remote-registers
34444 @item maint print registers @r{[}@var{file}@r{]}
34445 @itemx maint print raw-registers @r{[}@var{file}@r{]}
34446 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
34447 @itemx maint print register-groups @r{[}@var{file}@r{]}
34448 @itemx maint print remote-registers @r{[}@var{file}@r{]}
34449 Print @value{GDBN}'s internal register data structures.
34451 The command @code{maint print raw-registers} includes the contents of
34452 the raw register cache; the command @code{maint print
34453 cooked-registers} includes the (cooked) value of all registers,
34454 including registers which aren't available on the target nor visible
34455 to user; the command @code{maint print register-groups} includes the
34456 groups that each register is a member of; and the command @code{maint
34457 print remote-registers} includes the remote target's register numbers
34458 and offsets in the `G' packets.
34460 These commands take an optional parameter, a file name to which to
34461 write the information.
34463 @kindex maint print reggroups
34464 @item maint print reggroups @r{[}@var{file}@r{]}
34465 Print @value{GDBN}'s internal register group data structures. The
34466 optional argument @var{file} tells to what file to write the
34469 The register groups info looks like this:
34472 (@value{GDBP}) @kbd{maint print reggroups}
34485 This command forces @value{GDBN} to flush its internal register cache.
34487 @kindex maint print objfiles
34488 @cindex info for known object files
34489 @item maint print objfiles @r{[}@var{regexp}@r{]}
34490 Print a dump of all known object files.
34491 If @var{regexp} is specified, only print object files whose names
34492 match @var{regexp}. For each object file, this command prints its name,
34493 address in memory, and all of its psymtabs and symtabs.
34495 @kindex maint print user-registers
34496 @cindex user registers
34497 @item maint print user-registers
34498 List all currently available @dfn{user registers}. User registers
34499 typically provide alternate names for actual hardware registers. They
34500 include the four ``standard'' registers @code{$fp}, @code{$pc},
34501 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
34502 registers can be used in expressions in the same way as the canonical
34503 register names, but only the latter are listed by the @code{info
34504 registers} and @code{maint print registers} commands.
34506 @kindex maint print section-scripts
34507 @cindex info for known .debug_gdb_scripts-loaded scripts
34508 @item maint print section-scripts [@var{regexp}]
34509 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
34510 If @var{regexp} is specified, only print scripts loaded by object files
34511 matching @var{regexp}.
34512 For each script, this command prints its name as specified in the objfile,
34513 and the full path if known.
34514 @xref{dotdebug_gdb_scripts section}.
34516 @kindex maint print statistics
34517 @cindex bcache statistics
34518 @item maint print statistics
34519 This command prints, for each object file in the program, various data
34520 about that object file followed by the byte cache (@dfn{bcache})
34521 statistics for the object file. The objfile data includes the number
34522 of minimal, partial, full, and stabs symbols, the number of types
34523 defined by the objfile, the number of as yet unexpanded psym tables,
34524 the number of line tables and string tables, and the amount of memory
34525 used by the various tables. The bcache statistics include the counts,
34526 sizes, and counts of duplicates of all and unique objects, max,
34527 average, and median entry size, total memory used and its overhead and
34528 savings, and various measures of the hash table size and chain
34531 @kindex maint print target-stack
34532 @cindex target stack description
34533 @item maint print target-stack
34534 A @dfn{target} is an interface between the debugger and a particular
34535 kind of file or process. Targets can be stacked in @dfn{strata},
34536 so that more than one target can potentially respond to a request.
34537 In particular, memory accesses will walk down the stack of targets
34538 until they find a target that is interested in handling that particular
34541 This command prints a short description of each layer that was pushed on
34542 the @dfn{target stack}, starting from the top layer down to the bottom one.
34544 @kindex maint print type
34545 @cindex type chain of a data type
34546 @item maint print type @var{expr}
34547 Print the type chain for a type specified by @var{expr}. The argument
34548 can be either a type name or a symbol. If it is a symbol, the type of
34549 that symbol is described. The type chain produced by this command is
34550 a recursive definition of the data type as stored in @value{GDBN}'s
34551 data structures, including its flags and contained types.
34553 @kindex maint set dwarf always-disassemble
34554 @kindex maint show dwarf always-disassemble
34555 @item maint set dwarf always-disassemble
34556 @item maint show dwarf always-disassemble
34557 Control the behavior of @code{info address} when using DWARF debugging
34560 The default is @code{off}, which means that @value{GDBN} should try to
34561 describe a variable's location in an easily readable format. When
34562 @code{on}, @value{GDBN} will instead display the DWARF location
34563 expression in an assembly-like format. Note that some locations are
34564 too complex for @value{GDBN} to describe simply; in this case you will
34565 always see the disassembly form.
34567 Here is an example of the resulting disassembly:
34570 (gdb) info addr argc
34571 Symbol "argc" is a complex DWARF expression:
34575 For more information on these expressions, see
34576 @uref{http://www.dwarfstd.org/, the DWARF standard}.
34578 @kindex maint set dwarf max-cache-age
34579 @kindex maint show dwarf max-cache-age
34580 @item maint set dwarf max-cache-age
34581 @itemx maint show dwarf max-cache-age
34582 Control the DWARF compilation unit cache.
34584 @cindex DWARF compilation units cache
34585 In object files with inter-compilation-unit references, such as those
34586 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
34587 reader needs to frequently refer to previously read compilation units.
34588 This setting controls how long a compilation unit will remain in the
34589 cache if it is not referenced. A higher limit means that cached
34590 compilation units will be stored in memory longer, and more total
34591 memory will be used. Setting it to zero disables caching, which will
34592 slow down @value{GDBN} startup, but reduce memory consumption.
34594 @kindex maint set profile
34595 @kindex maint show profile
34596 @cindex profiling GDB
34597 @item maint set profile
34598 @itemx maint show profile
34599 Control profiling of @value{GDBN}.
34601 Profiling will be disabled until you use the @samp{maint set profile}
34602 command to enable it. When you enable profiling, the system will begin
34603 collecting timing and execution count data; when you disable profiling or
34604 exit @value{GDBN}, the results will be written to a log file. Remember that
34605 if you use profiling, @value{GDBN} will overwrite the profiling log file
34606 (often called @file{gmon.out}). If you have a record of important profiling
34607 data in a @file{gmon.out} file, be sure to move it to a safe location.
34609 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
34610 compiled with the @samp{-pg} compiler option.
34612 @kindex maint set show-debug-regs
34613 @kindex maint show show-debug-regs
34614 @cindex hardware debug registers
34615 @item maint set show-debug-regs
34616 @itemx maint show show-debug-regs
34617 Control whether to show variables that mirror the hardware debug
34618 registers. Use @code{on} to enable, @code{off} to disable. If
34619 enabled, the debug registers values are shown when @value{GDBN} inserts or
34620 removes a hardware breakpoint or watchpoint, and when the inferior
34621 triggers a hardware-assisted breakpoint or watchpoint.
34623 @kindex maint set show-all-tib
34624 @kindex maint show show-all-tib
34625 @item maint set show-all-tib
34626 @itemx maint show show-all-tib
34627 Control whether to show all non zero areas within a 1k block starting
34628 at thread local base, when using the @samp{info w32 thread-information-block}
34631 @kindex maint set target-async
34632 @kindex maint show target-async
34633 @item maint set target-async
34634 @itemx maint show target-async
34635 This controls whether @value{GDBN} targets operate in synchronous or
34636 asynchronous mode (@pxref{Background Execution}). Normally the
34637 default is asynchronous, if it is available; but this can be changed
34638 to more easily debug problems occurring only in synchronous mode.
34640 @kindex maint set target-non-stop @var{mode} [on|off|auto]
34641 @kindex maint show target-non-stop
34642 @item maint set target-non-stop
34643 @itemx maint show target-non-stop
34645 This controls whether @value{GDBN} targets always operate in non-stop
34646 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
34647 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
34648 if supported by the target.
34651 @item maint set target-non-stop auto
34652 This is the default mode. @value{GDBN} controls the target in
34653 non-stop mode if the target supports it.
34655 @item maint set target-non-stop on
34656 @value{GDBN} controls the target in non-stop mode even if the target
34657 does not indicate support.
34659 @item maint set target-non-stop off
34660 @value{GDBN} does not control the target in non-stop mode even if the
34661 target supports it.
34664 @kindex maint set per-command
34665 @kindex maint show per-command
34666 @item maint set per-command
34667 @itemx maint show per-command
34668 @cindex resources used by commands
34670 @value{GDBN} can display the resources used by each command.
34671 This is useful in debugging performance problems.
34674 @item maint set per-command space [on|off]
34675 @itemx maint show per-command space
34676 Enable or disable the printing of the memory used by GDB for each command.
34677 If enabled, @value{GDBN} will display how much memory each command
34678 took, following the command's own output.
34679 This can also be requested by invoking @value{GDBN} with the
34680 @option{--statistics} command-line switch (@pxref{Mode Options}).
34682 @item maint set per-command time [on|off]
34683 @itemx maint show per-command time
34684 Enable or disable the printing of the execution time of @value{GDBN}
34686 If enabled, @value{GDBN} will display how much time it
34687 took to execute each command, following the command's own output.
34688 Both CPU time and wallclock time are printed.
34689 Printing both is useful when trying to determine whether the cost is
34690 CPU or, e.g., disk/network latency.
34691 Note that the CPU time printed is for @value{GDBN} only, it does not include
34692 the execution time of the inferior because there's no mechanism currently
34693 to compute how much time was spent by @value{GDBN} and how much time was
34694 spent by the program been debugged.
34695 This can also be requested by invoking @value{GDBN} with the
34696 @option{--statistics} command-line switch (@pxref{Mode Options}).
34698 @item maint set per-command symtab [on|off]
34699 @itemx maint show per-command symtab
34700 Enable or disable the printing of basic symbol table statistics
34702 If enabled, @value{GDBN} will display the following information:
34706 number of symbol tables
34708 number of primary symbol tables
34710 number of blocks in the blockvector
34714 @kindex maint space
34715 @cindex memory used by commands
34716 @item maint space @var{value}
34717 An alias for @code{maint set per-command space}.
34718 A non-zero value enables it, zero disables it.
34721 @cindex time of command execution
34722 @item maint time @var{value}
34723 An alias for @code{maint set per-command time}.
34724 A non-zero value enables it, zero disables it.
34726 @kindex maint translate-address
34727 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
34728 Find the symbol stored at the location specified by the address
34729 @var{addr} and an optional section name @var{section}. If found,
34730 @value{GDBN} prints the name of the closest symbol and an offset from
34731 the symbol's location to the specified address. This is similar to
34732 the @code{info address} command (@pxref{Symbols}), except that this
34733 command also allows to find symbols in other sections.
34735 If section was not specified, the section in which the symbol was found
34736 is also printed. For dynamically linked executables, the name of
34737 executable or shared library containing the symbol is printed as well.
34741 The following command is useful for non-interactive invocations of
34742 @value{GDBN}, such as in the test suite.
34745 @item set watchdog @var{nsec}
34746 @kindex set watchdog
34747 @cindex watchdog timer
34748 @cindex timeout for commands
34749 Set the maximum number of seconds @value{GDBN} will wait for the
34750 target operation to finish. If this time expires, @value{GDBN}
34751 reports and error and the command is aborted.
34753 @item show watchdog
34754 Show the current setting of the target wait timeout.
34757 @node Remote Protocol
34758 @appendix @value{GDBN} Remote Serial Protocol
34763 * Stop Reply Packets::
34764 * General Query Packets::
34765 * Architecture-Specific Protocol Details::
34766 * Tracepoint Packets::
34767 * Host I/O Packets::
34769 * Notification Packets::
34770 * Remote Non-Stop::
34771 * Packet Acknowledgment::
34773 * File-I/O Remote Protocol Extension::
34774 * Library List Format::
34775 * Library List Format for SVR4 Targets::
34776 * Memory Map Format::
34777 * Thread List Format::
34778 * Traceframe Info Format::
34779 * Branch Trace Format::
34780 * Branch Trace Configuration Format::
34786 There may be occasions when you need to know something about the
34787 protocol---for example, if there is only one serial port to your target
34788 machine, you might want your program to do something special if it
34789 recognizes a packet meant for @value{GDBN}.
34791 In the examples below, @samp{->} and @samp{<-} are used to indicate
34792 transmitted and received data, respectively.
34794 @cindex protocol, @value{GDBN} remote serial
34795 @cindex serial protocol, @value{GDBN} remote
34796 @cindex remote serial protocol
34797 All @value{GDBN} commands and responses (other than acknowledgments
34798 and notifications, see @ref{Notification Packets}) are sent as a
34799 @var{packet}. A @var{packet} is introduced with the character
34800 @samp{$}, the actual @var{packet-data}, and the terminating character
34801 @samp{#} followed by a two-digit @var{checksum}:
34804 @code{$}@var{packet-data}@code{#}@var{checksum}
34808 @cindex checksum, for @value{GDBN} remote
34810 The two-digit @var{checksum} is computed as the modulo 256 sum of all
34811 characters between the leading @samp{$} and the trailing @samp{#} (an
34812 eight bit unsigned checksum).
34814 Implementors should note that prior to @value{GDBN} 5.0 the protocol
34815 specification also included an optional two-digit @var{sequence-id}:
34818 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
34821 @cindex sequence-id, for @value{GDBN} remote
34823 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
34824 has never output @var{sequence-id}s. Stubs that handle packets added
34825 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
34827 When either the host or the target machine receives a packet, the first
34828 response expected is an acknowledgment: either @samp{+} (to indicate
34829 the package was received correctly) or @samp{-} (to request
34833 -> @code{$}@var{packet-data}@code{#}@var{checksum}
34838 The @samp{+}/@samp{-} acknowledgments can be disabled
34839 once a connection is established.
34840 @xref{Packet Acknowledgment}, for details.
34842 The host (@value{GDBN}) sends @var{command}s, and the target (the
34843 debugging stub incorporated in your program) sends a @var{response}. In
34844 the case of step and continue @var{command}s, the response is only sent
34845 when the operation has completed, and the target has again stopped all
34846 threads in all attached processes. This is the default all-stop mode
34847 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
34848 execution mode; see @ref{Remote Non-Stop}, for details.
34850 @var{packet-data} consists of a sequence of characters with the
34851 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
34854 @cindex remote protocol, field separator
34855 Fields within the packet should be separated using @samp{,} @samp{;} or
34856 @samp{:}. Except where otherwise noted all numbers are represented in
34857 @sc{hex} with leading zeros suppressed.
34859 Implementors should note that prior to @value{GDBN} 5.0, the character
34860 @samp{:} could not appear as the third character in a packet (as it
34861 would potentially conflict with the @var{sequence-id}).
34863 @cindex remote protocol, binary data
34864 @anchor{Binary Data}
34865 Binary data in most packets is encoded either as two hexadecimal
34866 digits per byte of binary data. This allowed the traditional remote
34867 protocol to work over connections which were only seven-bit clean.
34868 Some packets designed more recently assume an eight-bit clean
34869 connection, and use a more efficient encoding to send and receive
34872 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
34873 as an escape character. Any escaped byte is transmitted as the escape
34874 character followed by the original character XORed with @code{0x20}.
34875 For example, the byte @code{0x7d} would be transmitted as the two
34876 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
34877 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
34878 @samp{@}}) must always be escaped. Responses sent by the stub
34879 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
34880 is not interpreted as the start of a run-length encoded sequence
34883 Response @var{data} can be run-length encoded to save space.
34884 Run-length encoding replaces runs of identical characters with one
34885 instance of the repeated character, followed by a @samp{*} and a
34886 repeat count. The repeat count is itself sent encoded, to avoid
34887 binary characters in @var{data}: a value of @var{n} is sent as
34888 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
34889 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
34890 code 32) for a repeat count of 3. (This is because run-length
34891 encoding starts to win for counts 3 or more.) Thus, for example,
34892 @samp{0* } is a run-length encoding of ``0000'': the space character
34893 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
34896 The printable characters @samp{#} and @samp{$} or with a numeric value
34897 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
34898 seven repeats (@samp{$}) can be expanded using a repeat count of only
34899 five (@samp{"}). For example, @samp{00000000} can be encoded as
34902 The error response returned for some packets includes a two character
34903 error number. That number is not well defined.
34905 @cindex empty response, for unsupported packets
34906 For any @var{command} not supported by the stub, an empty response
34907 (@samp{$#00}) should be returned. That way it is possible to extend the
34908 protocol. A newer @value{GDBN} can tell if a packet is supported based
34911 At a minimum, a stub is required to support the @samp{g} and @samp{G}
34912 commands for register access, and the @samp{m} and @samp{M} commands
34913 for memory access. Stubs that only control single-threaded targets
34914 can implement run control with the @samp{c} (continue), and @samp{s}
34915 (step) commands. Stubs that support multi-threading targets should
34916 support the @samp{vCont} command. All other commands are optional.
34921 The following table provides a complete list of all currently defined
34922 @var{command}s and their corresponding response @var{data}.
34923 @xref{File-I/O Remote Protocol Extension}, for details about the File
34924 I/O extension of the remote protocol.
34926 Each packet's description has a template showing the packet's overall
34927 syntax, followed by an explanation of the packet's meaning. We
34928 include spaces in some of the templates for clarity; these are not
34929 part of the packet's syntax. No @value{GDBN} packet uses spaces to
34930 separate its components. For example, a template like @samp{foo
34931 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
34932 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
34933 @var{baz}. @value{GDBN} does not transmit a space character between the
34934 @samp{foo} and the @var{bar}, or between the @var{bar} and the
34937 @cindex @var{thread-id}, in remote protocol
34938 @anchor{thread-id syntax}
34939 Several packets and replies include a @var{thread-id} field to identify
34940 a thread. Normally these are positive numbers with a target-specific
34941 interpretation, formatted as big-endian hex strings. A @var{thread-id}
34942 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
34945 In addition, the remote protocol supports a multiprocess feature in
34946 which the @var{thread-id} syntax is extended to optionally include both
34947 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
34948 The @var{pid} (process) and @var{tid} (thread) components each have the
34949 format described above: a positive number with target-specific
34950 interpretation formatted as a big-endian hex string, literal @samp{-1}
34951 to indicate all processes or threads (respectively), or @samp{0} to
34952 indicate an arbitrary process or thread. Specifying just a process, as
34953 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
34954 error to specify all processes but a specific thread, such as
34955 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
34956 for those packets and replies explicitly documented to include a process
34957 ID, rather than a @var{thread-id}.
34959 The multiprocess @var{thread-id} syntax extensions are only used if both
34960 @value{GDBN} and the stub report support for the @samp{multiprocess}
34961 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
34964 Note that all packet forms beginning with an upper- or lower-case
34965 letter, other than those described here, are reserved for future use.
34967 Here are the packet descriptions.
34972 @cindex @samp{!} packet
34973 @anchor{extended mode}
34974 Enable extended mode. In extended mode, the remote server is made
34975 persistent. The @samp{R} packet is used to restart the program being
34981 The remote target both supports and has enabled extended mode.
34985 @cindex @samp{?} packet
34987 Indicate the reason the target halted. The reply is the same as for
34988 step and continue. This packet has a special interpretation when the
34989 target is in non-stop mode; see @ref{Remote Non-Stop}.
34992 @xref{Stop Reply Packets}, for the reply specifications.
34994 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
34995 @cindex @samp{A} packet
34996 Initialized @code{argv[]} array passed into program. @var{arglen}
34997 specifies the number of bytes in the hex encoded byte stream
34998 @var{arg}. See @code{gdbserver} for more details.
35003 The arguments were set.
35009 @cindex @samp{b} packet
35010 (Don't use this packet; its behavior is not well-defined.)
35011 Change the serial line speed to @var{baud}.
35013 JTC: @emph{When does the transport layer state change? When it's
35014 received, or after the ACK is transmitted. In either case, there are
35015 problems if the command or the acknowledgment packet is dropped.}
35017 Stan: @emph{If people really wanted to add something like this, and get
35018 it working for the first time, they ought to modify ser-unix.c to send
35019 some kind of out-of-band message to a specially-setup stub and have the
35020 switch happen "in between" packets, so that from remote protocol's point
35021 of view, nothing actually happened.}
35023 @item B @var{addr},@var{mode}
35024 @cindex @samp{B} packet
35025 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
35026 breakpoint at @var{addr}.
35028 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
35029 (@pxref{insert breakpoint or watchpoint packet}).
35031 @cindex @samp{bc} packet
35034 Backward continue. Execute the target system in reverse. No parameter.
35035 @xref{Reverse Execution}, for more information.
35038 @xref{Stop Reply Packets}, for the reply specifications.
35040 @cindex @samp{bs} packet
35043 Backward single step. Execute one instruction in reverse. No parameter.
35044 @xref{Reverse Execution}, for more information.
35047 @xref{Stop Reply Packets}, for the reply specifications.
35049 @item c @r{[}@var{addr}@r{]}
35050 @cindex @samp{c} packet
35051 Continue at @var{addr}, which is the address to resume. If @var{addr}
35052 is omitted, resume at current address.
35054 This packet is deprecated for multi-threading support. @xref{vCont
35058 @xref{Stop Reply Packets}, for the reply specifications.
35060 @item C @var{sig}@r{[};@var{addr}@r{]}
35061 @cindex @samp{C} packet
35062 Continue with signal @var{sig} (hex signal number). If
35063 @samp{;@var{addr}} is omitted, resume at same address.
35065 This packet is deprecated for multi-threading support. @xref{vCont
35069 @xref{Stop Reply Packets}, for the reply specifications.
35072 @cindex @samp{d} packet
35075 Don't use this packet; instead, define a general set packet
35076 (@pxref{General Query Packets}).
35080 @cindex @samp{D} packet
35081 The first form of the packet is used to detach @value{GDBN} from the
35082 remote system. It is sent to the remote target
35083 before @value{GDBN} disconnects via the @code{detach} command.
35085 The second form, including a process ID, is used when multiprocess
35086 protocol extensions are enabled (@pxref{multiprocess extensions}), to
35087 detach only a specific process. The @var{pid} is specified as a
35088 big-endian hex string.
35098 @item F @var{RC},@var{EE},@var{CF};@var{XX}
35099 @cindex @samp{F} packet
35100 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
35101 This is part of the File-I/O protocol extension. @xref{File-I/O
35102 Remote Protocol Extension}, for the specification.
35105 @anchor{read registers packet}
35106 @cindex @samp{g} packet
35107 Read general registers.
35111 @item @var{XX@dots{}}
35112 Each byte of register data is described by two hex digits. The bytes
35113 with the register are transmitted in target byte order. The size of
35114 each register and their position within the @samp{g} packet are
35115 determined by the @value{GDBN} internal gdbarch functions
35116 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
35117 specification of several standard @samp{g} packets is specified below.
35119 When reading registers from a trace frame (@pxref{Analyze Collected
35120 Data,,Using the Collected Data}), the stub may also return a string of
35121 literal @samp{x}'s in place of the register data digits, to indicate
35122 that the corresponding register has not been collected, thus its value
35123 is unavailable. For example, for an architecture with 4 registers of
35124 4 bytes each, the following reply indicates to @value{GDBN} that
35125 registers 0 and 2 have not been collected, while registers 1 and 3
35126 have been collected, and both have zero value:
35130 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
35137 @item G @var{XX@dots{}}
35138 @cindex @samp{G} packet
35139 Write general registers. @xref{read registers packet}, for a
35140 description of the @var{XX@dots{}} data.
35150 @item H @var{op} @var{thread-id}
35151 @cindex @samp{H} packet
35152 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
35153 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
35154 should be @samp{c} for step and continue operations (note that this
35155 is deprecated, supporting the @samp{vCont} command is a better
35156 option), and @samp{g} for other operations. The thread designator
35157 @var{thread-id} has the format and interpretation described in
35158 @ref{thread-id syntax}.
35169 @c 'H': How restrictive (or permissive) is the thread model. If a
35170 @c thread is selected and stopped, are other threads allowed
35171 @c to continue to execute? As I mentioned above, I think the
35172 @c semantics of each command when a thread is selected must be
35173 @c described. For example:
35175 @c 'g': If the stub supports threads and a specific thread is
35176 @c selected, returns the register block from that thread;
35177 @c otherwise returns current registers.
35179 @c 'G' If the stub supports threads and a specific thread is
35180 @c selected, sets the registers of the register block of
35181 @c that thread; otherwise sets current registers.
35183 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
35184 @anchor{cycle step packet}
35185 @cindex @samp{i} packet
35186 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
35187 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
35188 step starting at that address.
35191 @cindex @samp{I} packet
35192 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
35196 @cindex @samp{k} packet
35199 The exact effect of this packet is not specified.
35201 For a bare-metal target, it may power cycle or reset the target
35202 system. For that reason, the @samp{k} packet has no reply.
35204 For a single-process target, it may kill that process if possible.
35206 A multiple-process target may choose to kill just one process, or all
35207 that are under @value{GDBN}'s control. For more precise control, use
35208 the vKill packet (@pxref{vKill packet}).
35210 If the target system immediately closes the connection in response to
35211 @samp{k}, @value{GDBN} does not consider the lack of packet
35212 acknowledgment to be an error, and assumes the kill was successful.
35214 If connected using @kbd{target extended-remote}, and the target does
35215 not close the connection in response to a kill request, @value{GDBN}
35216 probes the target state as if a new connection was opened
35217 (@pxref{? packet}).
35219 @item m @var{addr},@var{length}
35220 @cindex @samp{m} packet
35221 Read @var{length} addressable memory units starting at address @var{addr}
35222 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
35223 any particular boundary.
35225 The stub need not use any particular size or alignment when gathering
35226 data from memory for the response; even if @var{addr} is word-aligned
35227 and @var{length} is a multiple of the word size, the stub is free to
35228 use byte accesses, or not. For this reason, this packet may not be
35229 suitable for accessing memory-mapped I/O devices.
35230 @cindex alignment of remote memory accesses
35231 @cindex size of remote memory accesses
35232 @cindex memory, alignment and size of remote accesses
35236 @item @var{XX@dots{}}
35237 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
35238 The reply may contain fewer addressable memory units than requested if the
35239 server was able to read only part of the region of memory.
35244 @item M @var{addr},@var{length}:@var{XX@dots{}}
35245 @cindex @samp{M} packet
35246 Write @var{length} addressable memory units starting at address @var{addr}
35247 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
35248 byte is transmitted as a two-digit hexadecimal number.
35255 for an error (this includes the case where only part of the data was
35260 @cindex @samp{p} packet
35261 Read the value of register @var{n}; @var{n} is in hex.
35262 @xref{read registers packet}, for a description of how the returned
35263 register value is encoded.
35267 @item @var{XX@dots{}}
35268 the register's value
35272 Indicating an unrecognized @var{query}.
35275 @item P @var{n@dots{}}=@var{r@dots{}}
35276 @anchor{write register packet}
35277 @cindex @samp{P} packet
35278 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
35279 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
35280 digits for each byte in the register (target byte order).
35290 @item q @var{name} @var{params}@dots{}
35291 @itemx Q @var{name} @var{params}@dots{}
35292 @cindex @samp{q} packet
35293 @cindex @samp{Q} packet
35294 General query (@samp{q}) and set (@samp{Q}). These packets are
35295 described fully in @ref{General Query Packets}.
35298 @cindex @samp{r} packet
35299 Reset the entire system.
35301 Don't use this packet; use the @samp{R} packet instead.
35304 @cindex @samp{R} packet
35305 Restart the program being debugged. The @var{XX}, while needed, is ignored.
35306 This packet is only available in extended mode (@pxref{extended mode}).
35308 The @samp{R} packet has no reply.
35310 @item s @r{[}@var{addr}@r{]}
35311 @cindex @samp{s} packet
35312 Single step, resuming at @var{addr}. If
35313 @var{addr} is omitted, resume at same address.
35315 This packet is deprecated for multi-threading support. @xref{vCont
35319 @xref{Stop Reply Packets}, for the reply specifications.
35321 @item S @var{sig}@r{[};@var{addr}@r{]}
35322 @anchor{step with signal packet}
35323 @cindex @samp{S} packet
35324 Step with signal. This is analogous to the @samp{C} packet, but
35325 requests a single-step, rather than a normal resumption of execution.
35327 This packet is deprecated for multi-threading support. @xref{vCont
35331 @xref{Stop Reply Packets}, for the reply specifications.
35333 @item t @var{addr}:@var{PP},@var{MM}
35334 @cindex @samp{t} packet
35335 Search backwards starting at address @var{addr} for a match with pattern
35336 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
35337 There must be at least 3 digits in @var{addr}.
35339 @item T @var{thread-id}
35340 @cindex @samp{T} packet
35341 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
35346 thread is still alive
35352 Packets starting with @samp{v} are identified by a multi-letter name,
35353 up to the first @samp{;} or @samp{?} (or the end of the packet).
35355 @item vAttach;@var{pid}
35356 @cindex @samp{vAttach} packet
35357 Attach to a new process with the specified process ID @var{pid}.
35358 The process ID is a
35359 hexadecimal integer identifying the process. In all-stop mode, all
35360 threads in the attached process are stopped; in non-stop mode, it may be
35361 attached without being stopped if that is supported by the target.
35363 @c In non-stop mode, on a successful vAttach, the stub should set the
35364 @c current thread to a thread of the newly-attached process. After
35365 @c attaching, GDB queries for the attached process's thread ID with qC.
35366 @c Also note that, from a user perspective, whether or not the
35367 @c target is stopped on attach in non-stop mode depends on whether you
35368 @c use the foreground or background version of the attach command, not
35369 @c on what vAttach does; GDB does the right thing with respect to either
35370 @c stopping or restarting threads.
35372 This packet is only available in extended mode (@pxref{extended mode}).
35378 @item @r{Any stop packet}
35379 for success in all-stop mode (@pxref{Stop Reply Packets})
35381 for success in non-stop mode (@pxref{Remote Non-Stop})
35384 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
35385 @cindex @samp{vCont} packet
35386 @anchor{vCont packet}
35387 Resume the inferior, specifying different actions for each thread.
35388 If an action is specified with no @var{thread-id}, then it is applied to any
35389 threads that don't have a specific action specified; if no default action is
35390 specified then other threads should remain stopped in all-stop mode and
35391 in their current state in non-stop mode.
35392 Specifying multiple
35393 default actions is an error; specifying no actions is also an error.
35394 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
35396 Currently supported actions are:
35402 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
35406 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
35409 @item r @var{start},@var{end}
35410 Step once, and then keep stepping as long as the thread stops at
35411 addresses between @var{start} (inclusive) and @var{end} (exclusive).
35412 The remote stub reports a stop reply when either the thread goes out
35413 of the range or is stopped due to an unrelated reason, such as hitting
35414 a breakpoint. @xref{range stepping}.
35416 If the range is empty (@var{start} == @var{end}), then the action
35417 becomes equivalent to the @samp{s} action. In other words,
35418 single-step once, and report the stop (even if the stepped instruction
35419 jumps to @var{start}).
35421 (A stop reply may be sent at any point even if the PC is still within
35422 the stepping range; for example, it is valid to implement this packet
35423 in a degenerate way as a single instruction step operation.)
35427 The optional argument @var{addr} normally associated with the
35428 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
35429 not supported in @samp{vCont}.
35431 The @samp{t} action is only relevant in non-stop mode
35432 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
35433 A stop reply should be generated for any affected thread not already stopped.
35434 When a thread is stopped by means of a @samp{t} action,
35435 the corresponding stop reply should indicate that the thread has stopped with
35436 signal @samp{0}, regardless of whether the target uses some other signal
35437 as an implementation detail.
35439 The stub must support @samp{vCont} if it reports support for
35440 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
35441 this case @samp{vCont} actions can be specified to apply to all threads
35442 in a process by using the @samp{p@var{pid}.-1} form of the
35446 @xref{Stop Reply Packets}, for the reply specifications.
35449 @cindex @samp{vCont?} packet
35450 Request a list of actions supported by the @samp{vCont} packet.
35454 @item vCont@r{[};@var{action}@dots{}@r{]}
35455 The @samp{vCont} packet is supported. Each @var{action} is a supported
35456 command in the @samp{vCont} packet.
35458 The @samp{vCont} packet is not supported.
35461 @item vFile:@var{operation}:@var{parameter}@dots{}
35462 @cindex @samp{vFile} packet
35463 Perform a file operation on the target system. For details,
35464 see @ref{Host I/O Packets}.
35466 @item vFlashErase:@var{addr},@var{length}
35467 @cindex @samp{vFlashErase} packet
35468 Direct the stub to erase @var{length} bytes of flash starting at
35469 @var{addr}. The region may enclose any number of flash blocks, but
35470 its start and end must fall on block boundaries, as indicated by the
35471 flash block size appearing in the memory map (@pxref{Memory Map
35472 Format}). @value{GDBN} groups flash memory programming operations
35473 together, and sends a @samp{vFlashDone} request after each group; the
35474 stub is allowed to delay erase operation until the @samp{vFlashDone}
35475 packet is received.
35485 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
35486 @cindex @samp{vFlashWrite} packet
35487 Direct the stub to write data to flash address @var{addr}. The data
35488 is passed in binary form using the same encoding as for the @samp{X}
35489 packet (@pxref{Binary Data}). The memory ranges specified by
35490 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
35491 not overlap, and must appear in order of increasing addresses
35492 (although @samp{vFlashErase} packets for higher addresses may already
35493 have been received; the ordering is guaranteed only between
35494 @samp{vFlashWrite} packets). If a packet writes to an address that was
35495 neither erased by a preceding @samp{vFlashErase} packet nor by some other
35496 target-specific method, the results are unpredictable.
35504 for vFlashWrite addressing non-flash memory
35510 @cindex @samp{vFlashDone} packet
35511 Indicate to the stub that flash programming operation is finished.
35512 The stub is permitted to delay or batch the effects of a group of
35513 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
35514 @samp{vFlashDone} packet is received. The contents of the affected
35515 regions of flash memory are unpredictable until the @samp{vFlashDone}
35516 request is completed.
35518 @item vKill;@var{pid}
35519 @cindex @samp{vKill} packet
35520 @anchor{vKill packet}
35521 Kill the process with the specified process ID @var{pid}, which is a
35522 hexadecimal integer identifying the process. This packet is used in
35523 preference to @samp{k} when multiprocess protocol extensions are
35524 supported; see @ref{multiprocess extensions}.
35534 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
35535 @cindex @samp{vRun} packet
35536 Run the program @var{filename}, passing it each @var{argument} on its
35537 command line. The file and arguments are hex-encoded strings. If
35538 @var{filename} is an empty string, the stub may use a default program
35539 (e.g.@: the last program run). The program is created in the stopped
35542 @c FIXME: What about non-stop mode?
35544 This packet is only available in extended mode (@pxref{extended mode}).
35550 @item @r{Any stop packet}
35551 for success (@pxref{Stop Reply Packets})
35555 @cindex @samp{vStopped} packet
35556 @xref{Notification Packets}.
35558 @item X @var{addr},@var{length}:@var{XX@dots{}}
35560 @cindex @samp{X} packet
35561 Write data to memory, where the data is transmitted in binary.
35562 Memory is specified by its address @var{addr} and number of addressable memory
35563 units @var{length} (@pxref{addressable memory unit});
35564 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
35574 @item z @var{type},@var{addr},@var{kind}
35575 @itemx Z @var{type},@var{addr},@var{kind}
35576 @anchor{insert breakpoint or watchpoint packet}
35577 @cindex @samp{z} packet
35578 @cindex @samp{Z} packets
35579 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
35580 watchpoint starting at address @var{address} of kind @var{kind}.
35582 Each breakpoint and watchpoint packet @var{type} is documented
35585 @emph{Implementation notes: A remote target shall return an empty string
35586 for an unrecognized breakpoint or watchpoint packet @var{type}. A
35587 remote target shall support either both or neither of a given
35588 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
35589 avoid potential problems with duplicate packets, the operations should
35590 be implemented in an idempotent way.}
35592 @item z0,@var{addr},@var{kind}
35593 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
35594 @cindex @samp{z0} packet
35595 @cindex @samp{Z0} packet
35596 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
35597 @var{addr} of type @var{kind}.
35599 A memory breakpoint is implemented by replacing the instruction at
35600 @var{addr} with a software breakpoint or trap instruction. The
35601 @var{kind} is target-specific and typically indicates the size of
35602 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
35603 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
35604 architectures have additional meanings for @var{kind};
35605 @var{cond_list} is an optional list of conditional expressions in bytecode
35606 form that should be evaluated on the target's side. These are the
35607 conditions that should be taken into consideration when deciding if
35608 the breakpoint trigger should be reported back to @var{GDBN}.
35610 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
35611 for how to best report a memory breakpoint event to @value{GDBN}.
35613 The @var{cond_list} parameter is comprised of a series of expressions,
35614 concatenated without separators. Each expression has the following form:
35618 @item X @var{len},@var{expr}
35619 @var{len} is the length of the bytecode expression and @var{expr} is the
35620 actual conditional expression in bytecode form.
35624 The optional @var{cmd_list} parameter introduces commands that may be
35625 run on the target, rather than being reported back to @value{GDBN}.
35626 The parameter starts with a numeric flag @var{persist}; if the flag is
35627 nonzero, then the breakpoint may remain active and the commands
35628 continue to be run even when @value{GDBN} disconnects from the target.
35629 Following this flag is a series of expressions concatenated with no
35630 separators. Each expression has the following form:
35634 @item X @var{len},@var{expr}
35635 @var{len} is the length of the bytecode expression and @var{expr} is the
35636 actual conditional expression in bytecode form.
35640 see @ref{Architecture-Specific Protocol Details}.
35642 @emph{Implementation note: It is possible for a target to copy or move
35643 code that contains memory breakpoints (e.g., when implementing
35644 overlays). The behavior of this packet, in the presence of such a
35645 target, is not defined.}
35657 @item z1,@var{addr},@var{kind}
35658 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
35659 @cindex @samp{z1} packet
35660 @cindex @samp{Z1} packet
35661 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
35662 address @var{addr}.
35664 A hardware breakpoint is implemented using a mechanism that is not
35665 dependant on being able to modify the target's memory. The @var{kind}
35666 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
35668 @emph{Implementation note: A hardware breakpoint is not affected by code
35681 @item z2,@var{addr},@var{kind}
35682 @itemx Z2,@var{addr},@var{kind}
35683 @cindex @samp{z2} packet
35684 @cindex @samp{Z2} packet
35685 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
35686 The number of bytes to watch is specified by @var{kind}.
35698 @item z3,@var{addr},@var{kind}
35699 @itemx Z3,@var{addr},@var{kind}
35700 @cindex @samp{z3} packet
35701 @cindex @samp{Z3} packet
35702 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
35703 The number of bytes to watch is specified by @var{kind}.
35715 @item z4,@var{addr},@var{kind}
35716 @itemx Z4,@var{addr},@var{kind}
35717 @cindex @samp{z4} packet
35718 @cindex @samp{Z4} packet
35719 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
35720 The number of bytes to watch is specified by @var{kind}.
35734 @node Stop Reply Packets
35735 @section Stop Reply Packets
35736 @cindex stop reply packets
35738 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
35739 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
35740 receive any of the below as a reply. Except for @samp{?}
35741 and @samp{vStopped}, that reply is only returned
35742 when the target halts. In the below the exact meaning of @dfn{signal
35743 number} is defined by the header @file{include/gdb/signals.h} in the
35744 @value{GDBN} source code.
35746 As in the description of request packets, we include spaces in the
35747 reply templates for clarity; these are not part of the reply packet's
35748 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
35754 The program received signal number @var{AA} (a two-digit hexadecimal
35755 number). This is equivalent to a @samp{T} response with no
35756 @var{n}:@var{r} pairs.
35758 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
35759 @cindex @samp{T} packet reply
35760 The program received signal number @var{AA} (a two-digit hexadecimal
35761 number). This is equivalent to an @samp{S} response, except that the
35762 @samp{@var{n}:@var{r}} pairs can carry values of important registers
35763 and other information directly in the stop reply packet, reducing
35764 round-trip latency. Single-step and breakpoint traps are reported
35765 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
35769 If @var{n} is a hexadecimal number, it is a register number, and the
35770 corresponding @var{r} gives that register's value. The data @var{r} is a
35771 series of bytes in target byte order, with each byte given by a
35772 two-digit hex number.
35775 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
35776 the stopped thread, as specified in @ref{thread-id syntax}.
35779 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
35780 the core on which the stop event was detected.
35783 If @var{n} is a recognized @dfn{stop reason}, it describes a more
35784 specific event that stopped the target. The currently defined stop
35785 reasons are listed below. The @var{aa} should be @samp{05}, the trap
35786 signal. At most one stop reason should be present.
35789 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
35790 and go on to the next; this allows us to extend the protocol in the
35794 The currently defined stop reasons are:
35800 The packet indicates a watchpoint hit, and @var{r} is the data address, in
35803 @cindex shared library events, remote reply
35805 The packet indicates that the loaded libraries have changed.
35806 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
35807 list of loaded libraries. The @var{r} part is ignored.
35809 @cindex replay log events, remote reply
35811 The packet indicates that the target cannot continue replaying
35812 logged execution events, because it has reached the end (or the
35813 beginning when executing backward) of the log. The value of @var{r}
35814 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
35815 for more information.
35818 @anchor{swbreak stop reason}
35819 The packet indicates a memory breakpoint instruction was executed,
35820 irrespective of whether it was @value{GDBN} that planted the
35821 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
35822 part must be left empty.
35824 On some architectures, such as x86, at the architecture level, when a
35825 breakpoint instruction executes the program counter points at the
35826 breakpoint address plus an offset. On such targets, the stub is
35827 responsible for adjusting the PC to point back at the breakpoint
35830 This packet should not be sent by default; older @value{GDBN} versions
35831 did not support it. @value{GDBN} requests it, by supplying an
35832 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35833 remote stub must also supply the appropriate @samp{qSupported} feature
35834 indicating support.
35836 This packet is required for correct non-stop mode operation.
35839 The packet indicates the target stopped for a hardware breakpoint.
35840 The @var{r} part must be left empty.
35842 The same remarks about @samp{qSupported} and non-stop mode above
35845 @cindex fork events, remote reply
35847 The packet indicates that @code{fork} was called, and @var{r}
35848 is the thread ID of the new child process. Refer to
35849 @ref{thread-id syntax} for the format of the @var{thread-id}
35850 field. This packet is only applicable to targets that support
35853 This packet should not be sent by default; older @value{GDBN} versions
35854 did not support it. @value{GDBN} requests it, by supplying an
35855 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35856 remote stub must also supply the appropriate @samp{qSupported} feature
35857 indicating support.
35859 @cindex vfork events, remote reply
35861 The packet indicates that @code{vfork} was called, and @var{r}
35862 is the thread ID of the new child process. Refer to
35863 @ref{thread-id syntax} for the format of the @var{thread-id}
35864 field. This packet is only applicable to targets that support
35867 This packet should not be sent by default; older @value{GDBN} versions
35868 did not support it. @value{GDBN} requests it, by supplying an
35869 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35870 remote stub must also supply the appropriate @samp{qSupported} feature
35871 indicating support.
35873 @cindex vforkdone events, remote reply
35875 The packet indicates that a child process created by a vfork
35876 has either called @code{exec} or terminated, so that the
35877 address spaces of the parent and child process are no longer
35878 shared. The @var{r} part is ignored. This packet is only
35879 applicable to targets that support vforkdone events.
35881 This packet should not be sent by default; older @value{GDBN} versions
35882 did not support it. @value{GDBN} requests it, by supplying an
35883 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35884 remote stub must also supply the appropriate @samp{qSupported} feature
35885 indicating support.
35890 @itemx W @var{AA} ; process:@var{pid}
35891 The process exited, and @var{AA} is the exit status. This is only
35892 applicable to certain targets.
35894 The second form of the response, including the process ID of the exited
35895 process, can be used only when @value{GDBN} has reported support for
35896 multiprocess protocol extensions; see @ref{multiprocess extensions}.
35897 The @var{pid} is formatted as a big-endian hex string.
35900 @itemx X @var{AA} ; process:@var{pid}
35901 The process terminated with signal @var{AA}.
35903 The second form of the response, including the process ID of the
35904 terminated process, can be used only when @value{GDBN} has reported
35905 support for multiprocess protocol extensions; see @ref{multiprocess
35906 extensions}. The @var{pid} is formatted as a big-endian hex string.
35908 @item O @var{XX}@dots{}
35909 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
35910 written as the program's console output. This can happen at any time
35911 while the program is running and the debugger should continue to wait
35912 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
35914 @item F @var{call-id},@var{parameter}@dots{}
35915 @var{call-id} is the identifier which says which host system call should
35916 be called. This is just the name of the function. Translation into the
35917 correct system call is only applicable as it's defined in @value{GDBN}.
35918 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
35921 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
35922 this very system call.
35924 The target replies with this packet when it expects @value{GDBN} to
35925 call a host system call on behalf of the target. @value{GDBN} replies
35926 with an appropriate @samp{F} packet and keeps up waiting for the next
35927 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
35928 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
35929 Protocol Extension}, for more details.
35933 @node General Query Packets
35934 @section General Query Packets
35935 @cindex remote query requests
35937 Packets starting with @samp{q} are @dfn{general query packets};
35938 packets starting with @samp{Q} are @dfn{general set packets}. General
35939 query and set packets are a semi-unified form for retrieving and
35940 sending information to and from the stub.
35942 The initial letter of a query or set packet is followed by a name
35943 indicating what sort of thing the packet applies to. For example,
35944 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
35945 definitions with the stub. These packet names follow some
35950 The name must not contain commas, colons or semicolons.
35952 Most @value{GDBN} query and set packets have a leading upper case
35955 The names of custom vendor packets should use a company prefix, in
35956 lower case, followed by a period. For example, packets designed at
35957 the Acme Corporation might begin with @samp{qacme.foo} (for querying
35958 foos) or @samp{Qacme.bar} (for setting bars).
35961 The name of a query or set packet should be separated from any
35962 parameters by a @samp{:}; the parameters themselves should be
35963 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
35964 full packet name, and check for a separator or the end of the packet,
35965 in case two packet names share a common prefix. New packets should not begin
35966 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
35967 packets predate these conventions, and have arguments without any terminator
35968 for the packet name; we suspect they are in widespread use in places that
35969 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
35970 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
35973 Like the descriptions of the other packets, each description here
35974 has a template showing the packet's overall syntax, followed by an
35975 explanation of the packet's meaning. We include spaces in some of the
35976 templates for clarity; these are not part of the packet's syntax. No
35977 @value{GDBN} packet uses spaces to separate its components.
35979 Here are the currently defined query and set packets:
35985 Turn on or off the agent as a helper to perform some debugging operations
35986 delegated from @value{GDBN} (@pxref{Control Agent}).
35988 @item QAllow:@var{op}:@var{val}@dots{}
35989 @cindex @samp{QAllow} packet
35990 Specify which operations @value{GDBN} expects to request of the
35991 target, as a semicolon-separated list of operation name and value
35992 pairs. Possible values for @var{op} include @samp{WriteReg},
35993 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
35994 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
35995 indicating that @value{GDBN} will not request the operation, or 1,
35996 indicating that it may. (The target can then use this to set up its
35997 own internals optimally, for instance if the debugger never expects to
35998 insert breakpoints, it may not need to install its own trap handler.)
36001 @cindex current thread, remote request
36002 @cindex @samp{qC} packet
36003 Return the current thread ID.
36007 @item QC @var{thread-id}
36008 Where @var{thread-id} is a thread ID as documented in
36009 @ref{thread-id syntax}.
36010 @item @r{(anything else)}
36011 Any other reply implies the old thread ID.
36014 @item qCRC:@var{addr},@var{length}
36015 @cindex CRC of memory block, remote request
36016 @cindex @samp{qCRC} packet
36017 @anchor{qCRC packet}
36018 Compute the CRC checksum of a block of memory using CRC-32 defined in
36019 IEEE 802.3. The CRC is computed byte at a time, taking the most
36020 significant bit of each byte first. The initial pattern code
36021 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
36023 @emph{Note:} This is the same CRC used in validating separate debug
36024 files (@pxref{Separate Debug Files, , Debugging Information in Separate
36025 Files}). However the algorithm is slightly different. When validating
36026 separate debug files, the CRC is computed taking the @emph{least}
36027 significant bit of each byte first, and the final result is inverted to
36028 detect trailing zeros.
36033 An error (such as memory fault)
36034 @item C @var{crc32}
36035 The specified memory region's checksum is @var{crc32}.
36038 @item QDisableRandomization:@var{value}
36039 @cindex disable address space randomization, remote request
36040 @cindex @samp{QDisableRandomization} packet
36041 Some target operating systems will randomize the virtual address space
36042 of the inferior process as a security feature, but provide a feature
36043 to disable such randomization, e.g.@: to allow for a more deterministic
36044 debugging experience. On such systems, this packet with a @var{value}
36045 of 1 directs the target to disable address space randomization for
36046 processes subsequently started via @samp{vRun} packets, while a packet
36047 with a @var{value} of 0 tells the target to enable address space
36050 This packet is only available in extended mode (@pxref{extended mode}).
36055 The request succeeded.
36058 An error occurred. The error number @var{nn} is given as hex digits.
36061 An empty reply indicates that @samp{QDisableRandomization} is not supported
36065 This packet is not probed by default; the remote stub must request it,
36066 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36067 This should only be done on targets that actually support disabling
36068 address space randomization.
36071 @itemx qsThreadInfo
36072 @cindex list active threads, remote request
36073 @cindex @samp{qfThreadInfo} packet
36074 @cindex @samp{qsThreadInfo} packet
36075 Obtain a list of all active thread IDs from the target (OS). Since there
36076 may be too many active threads to fit into one reply packet, this query
36077 works iteratively: it may require more than one query/reply sequence to
36078 obtain the entire list of threads. The first query of the sequence will
36079 be the @samp{qfThreadInfo} query; subsequent queries in the
36080 sequence will be the @samp{qsThreadInfo} query.
36082 NOTE: This packet replaces the @samp{qL} query (see below).
36086 @item m @var{thread-id}
36088 @item m @var{thread-id},@var{thread-id}@dots{}
36089 a comma-separated list of thread IDs
36091 (lower case letter @samp{L}) denotes end of list.
36094 In response to each query, the target will reply with a list of one or
36095 more thread IDs, separated by commas.
36096 @value{GDBN} will respond to each reply with a request for more thread
36097 ids (using the @samp{qs} form of the query), until the target responds
36098 with @samp{l} (lower-case ell, for @dfn{last}).
36099 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
36102 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
36103 initial connection with the remote target, and the very first thread ID
36104 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
36105 message. Therefore, the stub should ensure that the first thread ID in
36106 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
36108 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
36109 @cindex get thread-local storage address, remote request
36110 @cindex @samp{qGetTLSAddr} packet
36111 Fetch the address associated with thread local storage specified
36112 by @var{thread-id}, @var{offset}, and @var{lm}.
36114 @var{thread-id} is the thread ID associated with the
36115 thread for which to fetch the TLS address. @xref{thread-id syntax}.
36117 @var{offset} is the (big endian, hex encoded) offset associated with the
36118 thread local variable. (This offset is obtained from the debug
36119 information associated with the variable.)
36121 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
36122 load module associated with the thread local storage. For example,
36123 a @sc{gnu}/Linux system will pass the link map address of the shared
36124 object associated with the thread local storage under consideration.
36125 Other operating environments may choose to represent the load module
36126 differently, so the precise meaning of this parameter will vary.
36130 @item @var{XX}@dots{}
36131 Hex encoded (big endian) bytes representing the address of the thread
36132 local storage requested.
36135 An error occurred. The error number @var{nn} is given as hex digits.
36138 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
36141 @item qGetTIBAddr:@var{thread-id}
36142 @cindex get thread information block address
36143 @cindex @samp{qGetTIBAddr} packet
36144 Fetch address of the Windows OS specific Thread Information Block.
36146 @var{thread-id} is the thread ID associated with the thread.
36150 @item @var{XX}@dots{}
36151 Hex encoded (big endian) bytes representing the linear address of the
36152 thread information block.
36155 An error occured. This means that either the thread was not found, or the
36156 address could not be retrieved.
36159 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
36162 @item qL @var{startflag} @var{threadcount} @var{nextthread}
36163 Obtain thread information from RTOS. Where: @var{startflag} (one hex
36164 digit) is one to indicate the first query and zero to indicate a
36165 subsequent query; @var{threadcount} (two hex digits) is the maximum
36166 number of threads the response packet can contain; and @var{nextthread}
36167 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
36168 returned in the response as @var{argthread}.
36170 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
36174 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
36175 Where: @var{count} (two hex digits) is the number of threads being
36176 returned; @var{done} (one hex digit) is zero to indicate more threads
36177 and one indicates no further threads; @var{argthreadid} (eight hex
36178 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
36179 is a sequence of thread IDs, @var{threadid} (eight hex
36180 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
36184 @cindex section offsets, remote request
36185 @cindex @samp{qOffsets} packet
36186 Get section offsets that the target used when relocating the downloaded
36191 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
36192 Relocate the @code{Text} section by @var{xxx} from its original address.
36193 Relocate the @code{Data} section by @var{yyy} from its original address.
36194 If the object file format provides segment information (e.g.@: @sc{elf}
36195 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
36196 segments by the supplied offsets.
36198 @emph{Note: while a @code{Bss} offset may be included in the response,
36199 @value{GDBN} ignores this and instead applies the @code{Data} offset
36200 to the @code{Bss} section.}
36202 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
36203 Relocate the first segment of the object file, which conventionally
36204 contains program code, to a starting address of @var{xxx}. If
36205 @samp{DataSeg} is specified, relocate the second segment, which
36206 conventionally contains modifiable data, to a starting address of
36207 @var{yyy}. @value{GDBN} will report an error if the object file
36208 does not contain segment information, or does not contain at least
36209 as many segments as mentioned in the reply. Extra segments are
36210 kept at fixed offsets relative to the last relocated segment.
36213 @item qP @var{mode} @var{thread-id}
36214 @cindex thread information, remote request
36215 @cindex @samp{qP} packet
36216 Returns information on @var{thread-id}. Where: @var{mode} is a hex
36217 encoded 32 bit mode; @var{thread-id} is a thread ID
36218 (@pxref{thread-id syntax}).
36220 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
36223 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
36227 @cindex non-stop mode, remote request
36228 @cindex @samp{QNonStop} packet
36230 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
36231 @xref{Remote Non-Stop}, for more information.
36236 The request succeeded.
36239 An error occurred. The error number @var{nn} is given as hex digits.
36242 An empty reply indicates that @samp{QNonStop} is not supported by
36246 This packet is not probed by default; the remote stub must request it,
36247 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36248 Use of this packet is controlled by the @code{set non-stop} command;
36249 @pxref{Non-Stop Mode}.
36251 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
36252 @cindex pass signals to inferior, remote request
36253 @cindex @samp{QPassSignals} packet
36254 @anchor{QPassSignals}
36255 Each listed @var{signal} should be passed directly to the inferior process.
36256 Signals are numbered identically to continue packets and stop replies
36257 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
36258 strictly greater than the previous item. These signals do not need to stop
36259 the inferior, or be reported to @value{GDBN}. All other signals should be
36260 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
36261 combine; any earlier @samp{QPassSignals} list is completely replaced by the
36262 new list. This packet improves performance when using @samp{handle
36263 @var{signal} nostop noprint pass}.
36268 The request succeeded.
36271 An error occurred. The error number @var{nn} is given as hex digits.
36274 An empty reply indicates that @samp{QPassSignals} is not supported by
36278 Use of this packet is controlled by the @code{set remote pass-signals}
36279 command (@pxref{Remote Configuration, set remote pass-signals}).
36280 This packet is not probed by default; the remote stub must request it,
36281 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36283 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
36284 @cindex signals the inferior may see, remote request
36285 @cindex @samp{QProgramSignals} packet
36286 @anchor{QProgramSignals}
36287 Each listed @var{signal} may be delivered to the inferior process.
36288 Others should be silently discarded.
36290 In some cases, the remote stub may need to decide whether to deliver a
36291 signal to the program or not without @value{GDBN} involvement. One
36292 example of that is while detaching --- the program's threads may have
36293 stopped for signals that haven't yet had a chance of being reported to
36294 @value{GDBN}, and so the remote stub can use the signal list specified
36295 by this packet to know whether to deliver or ignore those pending
36298 This does not influence whether to deliver a signal as requested by a
36299 resumption packet (@pxref{vCont packet}).
36301 Signals are numbered identically to continue packets and stop replies
36302 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
36303 strictly greater than the previous item. Multiple
36304 @samp{QProgramSignals} packets do not combine; any earlier
36305 @samp{QProgramSignals} list is completely replaced by the new list.
36310 The request succeeded.
36313 An error occurred. The error number @var{nn} is given as hex digits.
36316 An empty reply indicates that @samp{QProgramSignals} is not supported
36320 Use of this packet is controlled by the @code{set remote program-signals}
36321 command (@pxref{Remote Configuration, set remote program-signals}).
36322 This packet is not probed by default; the remote stub must request it,
36323 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36325 @item qRcmd,@var{command}
36326 @cindex execute remote command, remote request
36327 @cindex @samp{qRcmd} packet
36328 @var{command} (hex encoded) is passed to the local interpreter for
36329 execution. Invalid commands should be reported using the output
36330 string. Before the final result packet, the target may also respond
36331 with a number of intermediate @samp{O@var{output}} console output
36332 packets. @emph{Implementors should note that providing access to a
36333 stubs's interpreter may have security implications}.
36338 A command response with no output.
36340 A command response with the hex encoded output string @var{OUTPUT}.
36342 Indicate a badly formed request.
36344 An empty reply indicates that @samp{qRcmd} is not recognized.
36347 (Note that the @code{qRcmd} packet's name is separated from the
36348 command by a @samp{,}, not a @samp{:}, contrary to the naming
36349 conventions above. Please don't use this packet as a model for new
36352 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
36353 @cindex searching memory, in remote debugging
36355 @cindex @samp{qSearch:memory} packet
36357 @cindex @samp{qSearch memory} packet
36358 @anchor{qSearch memory}
36359 Search @var{length} bytes at @var{address} for @var{search-pattern}.
36360 Both @var{address} and @var{length} are encoded in hex;
36361 @var{search-pattern} is a sequence of bytes, also hex encoded.
36366 The pattern was not found.
36368 The pattern was found at @var{address}.
36370 A badly formed request or an error was encountered while searching memory.
36372 An empty reply indicates that @samp{qSearch:memory} is not recognized.
36375 @item QStartNoAckMode
36376 @cindex @samp{QStartNoAckMode} packet
36377 @anchor{QStartNoAckMode}
36378 Request that the remote stub disable the normal @samp{+}/@samp{-}
36379 protocol acknowledgments (@pxref{Packet Acknowledgment}).
36384 The stub has switched to no-acknowledgment mode.
36385 @value{GDBN} acknowledges this reponse,
36386 but neither the stub nor @value{GDBN} shall send or expect further
36387 @samp{+}/@samp{-} acknowledgments in the current connection.
36389 An empty reply indicates that the stub does not support no-acknowledgment mode.
36392 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
36393 @cindex supported packets, remote query
36394 @cindex features of the remote protocol
36395 @cindex @samp{qSupported} packet
36396 @anchor{qSupported}
36397 Tell the remote stub about features supported by @value{GDBN}, and
36398 query the stub for features it supports. This packet allows
36399 @value{GDBN} and the remote stub to take advantage of each others'
36400 features. @samp{qSupported} also consolidates multiple feature probes
36401 at startup, to improve @value{GDBN} performance---a single larger
36402 packet performs better than multiple smaller probe packets on
36403 high-latency links. Some features may enable behavior which must not
36404 be on by default, e.g.@: because it would confuse older clients or
36405 stubs. Other features may describe packets which could be
36406 automatically probed for, but are not. These features must be
36407 reported before @value{GDBN} will use them. This ``default
36408 unsupported'' behavior is not appropriate for all packets, but it
36409 helps to keep the initial connection time under control with new
36410 versions of @value{GDBN} which support increasing numbers of packets.
36414 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
36415 The stub supports or does not support each returned @var{stubfeature},
36416 depending on the form of each @var{stubfeature} (see below for the
36419 An empty reply indicates that @samp{qSupported} is not recognized,
36420 or that no features needed to be reported to @value{GDBN}.
36423 The allowed forms for each feature (either a @var{gdbfeature} in the
36424 @samp{qSupported} packet, or a @var{stubfeature} in the response)
36428 @item @var{name}=@var{value}
36429 The remote protocol feature @var{name} is supported, and associated
36430 with the specified @var{value}. The format of @var{value} depends
36431 on the feature, but it must not include a semicolon.
36433 The remote protocol feature @var{name} is supported, and does not
36434 need an associated value.
36436 The remote protocol feature @var{name} is not supported.
36438 The remote protocol feature @var{name} may be supported, and
36439 @value{GDBN} should auto-detect support in some other way when it is
36440 needed. This form will not be used for @var{gdbfeature} notifications,
36441 but may be used for @var{stubfeature} responses.
36444 Whenever the stub receives a @samp{qSupported} request, the
36445 supplied set of @value{GDBN} features should override any previous
36446 request. This allows @value{GDBN} to put the stub in a known
36447 state, even if the stub had previously been communicating with
36448 a different version of @value{GDBN}.
36450 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
36455 This feature indicates whether @value{GDBN} supports multiprocess
36456 extensions to the remote protocol. @value{GDBN} does not use such
36457 extensions unless the stub also reports that it supports them by
36458 including @samp{multiprocess+} in its @samp{qSupported} reply.
36459 @xref{multiprocess extensions}, for details.
36462 This feature indicates that @value{GDBN} supports the XML target
36463 description. If the stub sees @samp{xmlRegisters=} with target
36464 specific strings separated by a comma, it will report register
36468 This feature indicates whether @value{GDBN} supports the
36469 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
36470 instruction reply packet}).
36473 This feature indicates whether @value{GDBN} supports the swbreak stop
36474 reason in stop replies. @xref{swbreak stop reason}, for details.
36477 This feature indicates whether @value{GDBN} supports the hwbreak stop
36478 reason in stop replies. @xref{swbreak stop reason}, for details.
36481 This feature indicates whether @value{GDBN} supports fork event
36482 extensions to the remote protocol. @value{GDBN} does not use such
36483 extensions unless the stub also reports that it supports them by
36484 including @samp{fork-events+} in its @samp{qSupported} reply.
36487 This feature indicates whether @value{GDBN} supports vfork event
36488 extensions to the remote protocol. @value{GDBN} does not use such
36489 extensions unless the stub also reports that it supports them by
36490 including @samp{vfork-events+} in its @samp{qSupported} reply.
36493 Stubs should ignore any unknown values for
36494 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
36495 packet supports receiving packets of unlimited length (earlier
36496 versions of @value{GDBN} may reject overly long responses). Additional values
36497 for @var{gdbfeature} may be defined in the future to let the stub take
36498 advantage of new features in @value{GDBN}, e.g.@: incompatible
36499 improvements in the remote protocol---the @samp{multiprocess} feature is
36500 an example of such a feature. The stub's reply should be independent
36501 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
36502 describes all the features it supports, and then the stub replies with
36503 all the features it supports.
36505 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
36506 responses, as long as each response uses one of the standard forms.
36508 Some features are flags. A stub which supports a flag feature
36509 should respond with a @samp{+} form response. Other features
36510 require values, and the stub should respond with an @samp{=}
36513 Each feature has a default value, which @value{GDBN} will use if
36514 @samp{qSupported} is not available or if the feature is not mentioned
36515 in the @samp{qSupported} response. The default values are fixed; a
36516 stub is free to omit any feature responses that match the defaults.
36518 Not all features can be probed, but for those which can, the probing
36519 mechanism is useful: in some cases, a stub's internal
36520 architecture may not allow the protocol layer to know some information
36521 about the underlying target in advance. This is especially common in
36522 stubs which may be configured for multiple targets.
36524 These are the currently defined stub features and their properties:
36526 @multitable @columnfractions 0.35 0.2 0.12 0.2
36527 @c NOTE: The first row should be @headitem, but we do not yet require
36528 @c a new enough version of Texinfo (4.7) to use @headitem.
36530 @tab Value Required
36534 @item @samp{PacketSize}
36539 @item @samp{qXfer:auxv:read}
36544 @item @samp{qXfer:btrace:read}
36549 @item @samp{qXfer:btrace-conf:read}
36554 @item @samp{qXfer:exec-file:read}
36559 @item @samp{qXfer:features:read}
36564 @item @samp{qXfer:libraries:read}
36569 @item @samp{qXfer:libraries-svr4:read}
36574 @item @samp{augmented-libraries-svr4-read}
36579 @item @samp{qXfer:memory-map:read}
36584 @item @samp{qXfer:sdata:read}
36589 @item @samp{qXfer:spu:read}
36594 @item @samp{qXfer:spu:write}
36599 @item @samp{qXfer:siginfo:read}
36604 @item @samp{qXfer:siginfo:write}
36609 @item @samp{qXfer:threads:read}
36614 @item @samp{qXfer:traceframe-info:read}
36619 @item @samp{qXfer:uib:read}
36624 @item @samp{qXfer:fdpic:read}
36629 @item @samp{Qbtrace:off}
36634 @item @samp{Qbtrace:bts}
36639 @item @samp{Qbtrace:pt}
36644 @item @samp{Qbtrace-conf:bts:size}
36649 @item @samp{Qbtrace-conf:pt:size}
36654 @item @samp{QNonStop}
36659 @item @samp{QPassSignals}
36664 @item @samp{QStartNoAckMode}
36669 @item @samp{multiprocess}
36674 @item @samp{ConditionalBreakpoints}
36679 @item @samp{ConditionalTracepoints}
36684 @item @samp{ReverseContinue}
36689 @item @samp{ReverseStep}
36694 @item @samp{TracepointSource}
36699 @item @samp{QAgent}
36704 @item @samp{QAllow}
36709 @item @samp{QDisableRandomization}
36714 @item @samp{EnableDisableTracepoints}
36719 @item @samp{QTBuffer:size}
36724 @item @samp{tracenz}
36729 @item @samp{BreakpointCommands}
36734 @item @samp{swbreak}
36739 @item @samp{hwbreak}
36744 @item @samp{fork-events}
36749 @item @samp{vfork-events}
36756 These are the currently defined stub features, in more detail:
36759 @cindex packet size, remote protocol
36760 @item PacketSize=@var{bytes}
36761 The remote stub can accept packets up to at least @var{bytes} in
36762 length. @value{GDBN} will send packets up to this size for bulk
36763 transfers, and will never send larger packets. This is a limit on the
36764 data characters in the packet, including the frame and checksum.
36765 There is no trailing NUL byte in a remote protocol packet; if the stub
36766 stores packets in a NUL-terminated format, it should allow an extra
36767 byte in its buffer for the NUL. If this stub feature is not supported,
36768 @value{GDBN} guesses based on the size of the @samp{g} packet response.
36770 @item qXfer:auxv:read
36771 The remote stub understands the @samp{qXfer:auxv:read} packet
36772 (@pxref{qXfer auxiliary vector read}).
36774 @item qXfer:btrace:read
36775 The remote stub understands the @samp{qXfer:btrace:read}
36776 packet (@pxref{qXfer btrace read}).
36778 @item qXfer:btrace-conf:read
36779 The remote stub understands the @samp{qXfer:btrace-conf:read}
36780 packet (@pxref{qXfer btrace-conf read}).
36782 @item qXfer:exec-file:read
36783 The remote stub understands the @samp{qXfer:exec-file:read} packet
36784 (@pxref{qXfer executable filename read}).
36786 @item qXfer:features:read
36787 The remote stub understands the @samp{qXfer:features:read} packet
36788 (@pxref{qXfer target description read}).
36790 @item qXfer:libraries:read
36791 The remote stub understands the @samp{qXfer:libraries:read} packet
36792 (@pxref{qXfer library list read}).
36794 @item qXfer:libraries-svr4:read
36795 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
36796 (@pxref{qXfer svr4 library list read}).
36798 @item augmented-libraries-svr4-read
36799 The remote stub understands the augmented form of the
36800 @samp{qXfer:libraries-svr4:read} packet
36801 (@pxref{qXfer svr4 library list read}).
36803 @item qXfer:memory-map:read
36804 The remote stub understands the @samp{qXfer:memory-map:read} packet
36805 (@pxref{qXfer memory map read}).
36807 @item qXfer:sdata:read
36808 The remote stub understands the @samp{qXfer:sdata:read} packet
36809 (@pxref{qXfer sdata read}).
36811 @item qXfer:spu:read
36812 The remote stub understands the @samp{qXfer:spu:read} packet
36813 (@pxref{qXfer spu read}).
36815 @item qXfer:spu:write
36816 The remote stub understands the @samp{qXfer:spu:write} packet
36817 (@pxref{qXfer spu write}).
36819 @item qXfer:siginfo:read
36820 The remote stub understands the @samp{qXfer:siginfo:read} packet
36821 (@pxref{qXfer siginfo read}).
36823 @item qXfer:siginfo:write
36824 The remote stub understands the @samp{qXfer:siginfo:write} packet
36825 (@pxref{qXfer siginfo write}).
36827 @item qXfer:threads:read
36828 The remote stub understands the @samp{qXfer:threads:read} packet
36829 (@pxref{qXfer threads read}).
36831 @item qXfer:traceframe-info:read
36832 The remote stub understands the @samp{qXfer:traceframe-info:read}
36833 packet (@pxref{qXfer traceframe info read}).
36835 @item qXfer:uib:read
36836 The remote stub understands the @samp{qXfer:uib:read}
36837 packet (@pxref{qXfer unwind info block}).
36839 @item qXfer:fdpic:read
36840 The remote stub understands the @samp{qXfer:fdpic:read}
36841 packet (@pxref{qXfer fdpic loadmap read}).
36844 The remote stub understands the @samp{QNonStop} packet
36845 (@pxref{QNonStop}).
36848 The remote stub understands the @samp{QPassSignals} packet
36849 (@pxref{QPassSignals}).
36851 @item QStartNoAckMode
36852 The remote stub understands the @samp{QStartNoAckMode} packet and
36853 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
36856 @anchor{multiprocess extensions}
36857 @cindex multiprocess extensions, in remote protocol
36858 The remote stub understands the multiprocess extensions to the remote
36859 protocol syntax. The multiprocess extensions affect the syntax of
36860 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
36861 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
36862 replies. Note that reporting this feature indicates support for the
36863 syntactic extensions only, not that the stub necessarily supports
36864 debugging of more than one process at a time. The stub must not use
36865 multiprocess extensions in packet replies unless @value{GDBN} has also
36866 indicated it supports them in its @samp{qSupported} request.
36868 @item qXfer:osdata:read
36869 The remote stub understands the @samp{qXfer:osdata:read} packet
36870 ((@pxref{qXfer osdata read}).
36872 @item ConditionalBreakpoints
36873 The target accepts and implements evaluation of conditional expressions
36874 defined for breakpoints. The target will only report breakpoint triggers
36875 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
36877 @item ConditionalTracepoints
36878 The remote stub accepts and implements conditional expressions defined
36879 for tracepoints (@pxref{Tracepoint Conditions}).
36881 @item ReverseContinue
36882 The remote stub accepts and implements the reverse continue packet
36886 The remote stub accepts and implements the reverse step packet
36889 @item TracepointSource
36890 The remote stub understands the @samp{QTDPsrc} packet that supplies
36891 the source form of tracepoint definitions.
36894 The remote stub understands the @samp{QAgent} packet.
36897 The remote stub understands the @samp{QAllow} packet.
36899 @item QDisableRandomization
36900 The remote stub understands the @samp{QDisableRandomization} packet.
36902 @item StaticTracepoint
36903 @cindex static tracepoints, in remote protocol
36904 The remote stub supports static tracepoints.
36906 @item InstallInTrace
36907 @anchor{install tracepoint in tracing}
36908 The remote stub supports installing tracepoint in tracing.
36910 @item EnableDisableTracepoints
36911 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
36912 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
36913 to be enabled and disabled while a trace experiment is running.
36915 @item QTBuffer:size
36916 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
36917 packet that allows to change the size of the trace buffer.
36920 @cindex string tracing, in remote protocol
36921 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
36922 See @ref{Bytecode Descriptions} for details about the bytecode.
36924 @item BreakpointCommands
36925 @cindex breakpoint commands, in remote protocol
36926 The remote stub supports running a breakpoint's command list itself,
36927 rather than reporting the hit to @value{GDBN}.
36930 The remote stub understands the @samp{Qbtrace:off} packet.
36933 The remote stub understands the @samp{Qbtrace:bts} packet.
36936 The remote stub understands the @samp{Qbtrace:pt} packet.
36938 @item Qbtrace-conf:bts:size
36939 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
36941 @item Qbtrace-conf:pt:size
36942 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
36945 The remote stub reports the @samp{swbreak} stop reason for memory
36949 The remote stub reports the @samp{hwbreak} stop reason for hardware
36953 The remote stub reports the @samp{fork} stop reason for fork events.
36956 The remote stub reports the @samp{vfork} stop reason for vfork events
36957 and vforkdone events.
36962 @cindex symbol lookup, remote request
36963 @cindex @samp{qSymbol} packet
36964 Notify the target that @value{GDBN} is prepared to serve symbol lookup
36965 requests. Accept requests from the target for the values of symbols.
36970 The target does not need to look up any (more) symbols.
36971 @item qSymbol:@var{sym_name}
36972 The target requests the value of symbol @var{sym_name} (hex encoded).
36973 @value{GDBN} may provide the value by using the
36974 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
36978 @item qSymbol:@var{sym_value}:@var{sym_name}
36979 Set the value of @var{sym_name} to @var{sym_value}.
36981 @var{sym_name} (hex encoded) is the name of a symbol whose value the
36982 target has previously requested.
36984 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
36985 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
36991 The target does not need to look up any (more) symbols.
36992 @item qSymbol:@var{sym_name}
36993 The target requests the value of a new symbol @var{sym_name} (hex
36994 encoded). @value{GDBN} will continue to supply the values of symbols
36995 (if available), until the target ceases to request them.
37000 @itemx QTDisconnected
37007 @itemx qTMinFTPILen
37009 @xref{Tracepoint Packets}.
37011 @item qThreadExtraInfo,@var{thread-id}
37012 @cindex thread attributes info, remote request
37013 @cindex @samp{qThreadExtraInfo} packet
37014 Obtain from the target OS a printable string description of thread
37015 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
37016 for the forms of @var{thread-id}. This
37017 string may contain anything that the target OS thinks is interesting
37018 for @value{GDBN} to tell the user about the thread. The string is
37019 displayed in @value{GDBN}'s @code{info threads} display. Some
37020 examples of possible thread extra info strings are @samp{Runnable}, or
37021 @samp{Blocked on Mutex}.
37025 @item @var{XX}@dots{}
37026 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
37027 comprising the printable string containing the extra information about
37028 the thread's attributes.
37031 (Note that the @code{qThreadExtraInfo} packet's name is separated from
37032 the command by a @samp{,}, not a @samp{:}, contrary to the naming
37033 conventions above. Please don't use this packet as a model for new
37052 @xref{Tracepoint Packets}.
37054 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
37055 @cindex read special object, remote request
37056 @cindex @samp{qXfer} packet
37057 @anchor{qXfer read}
37058 Read uninterpreted bytes from the target's special data area
37059 identified by the keyword @var{object}. Request @var{length} bytes
37060 starting at @var{offset} bytes into the data. The content and
37061 encoding of @var{annex} is specific to @var{object}; it can supply
37062 additional details about what data to access.
37064 Here are the specific requests of this form defined so far. All
37065 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
37066 formats, listed below.
37069 @item qXfer:auxv:read::@var{offset},@var{length}
37070 @anchor{qXfer auxiliary vector read}
37071 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
37072 auxiliary vector}. Note @var{annex} must be empty.
37074 This packet is not probed by default; the remote stub must request it,
37075 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37077 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
37078 @anchor{qXfer btrace read}
37080 Return a description of the current branch trace.
37081 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
37082 packet may have one of the following values:
37086 Returns all available branch trace.
37089 Returns all available branch trace if the branch trace changed since
37090 the last read request.
37093 Returns the new branch trace since the last read request. Adds a new
37094 block to the end of the trace that begins at zero and ends at the source
37095 location of the first branch in the trace buffer. This extra block is
37096 used to stitch traces together.
37098 If the trace buffer overflowed, returns an error indicating the overflow.
37101 This packet is not probed by default; the remote stub must request it
37102 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37104 @item qXfer:btrace-conf:read::@var{offset},@var{length}
37105 @anchor{qXfer btrace-conf read}
37107 Return a description of the current branch trace configuration.
37108 @xref{Branch Trace Configuration Format}.
37110 This packet is not probed by default; the remote stub must request it
37111 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37113 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
37114 @anchor{qXfer executable filename read}
37115 Return the full absolute name of the file that was executed to create
37116 a process running on the remote system. The annex specifies the
37117 numeric process ID of the process to query, encoded as a hexadecimal
37118 number. If the annex part is empty the remote stub should return the
37119 filename corresponding to the currently executing process.
37121 This packet is not probed by default; the remote stub must request it,
37122 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37124 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
37125 @anchor{qXfer target description read}
37126 Access the @dfn{target description}. @xref{Target Descriptions}. The
37127 annex specifies which XML document to access. The main description is
37128 always loaded from the @samp{target.xml} annex.
37130 This packet is not probed by default; the remote stub must request it,
37131 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37133 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
37134 @anchor{qXfer library list read}
37135 Access the target's list of loaded libraries. @xref{Library List Format}.
37136 The annex part of the generic @samp{qXfer} packet must be empty
37137 (@pxref{qXfer read}).
37139 Targets which maintain a list of libraries in the program's memory do
37140 not need to implement this packet; it is designed for platforms where
37141 the operating system manages the list of loaded libraries.
37143 This packet is not probed by default; the remote stub must request it,
37144 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37146 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
37147 @anchor{qXfer svr4 library list read}
37148 Access the target's list of loaded libraries when the target is an SVR4
37149 platform. @xref{Library List Format for SVR4 Targets}. The annex part
37150 of the generic @samp{qXfer} packet must be empty unless the remote
37151 stub indicated it supports the augmented form of this packet
37152 by supplying an appropriate @samp{qSupported} response
37153 (@pxref{qXfer read}, @ref{qSupported}).
37155 This packet is optional for better performance on SVR4 targets.
37156 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
37158 This packet is not probed by default; the remote stub must request it,
37159 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37161 If the remote stub indicates it supports the augmented form of this
37162 packet then the annex part of the generic @samp{qXfer} packet may
37163 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
37164 arguments. The currently supported arguments are:
37167 @item start=@var{address}
37168 A hexadecimal number specifying the address of the @samp{struct
37169 link_map} to start reading the library list from. If unset or zero
37170 then the first @samp{struct link_map} in the library list will be
37171 chosen as the starting point.
37173 @item prev=@var{address}
37174 A hexadecimal number specifying the address of the @samp{struct
37175 link_map} immediately preceding the @samp{struct link_map}
37176 specified by the @samp{start} argument. If unset or zero then
37177 the remote stub will expect that no @samp{struct link_map}
37178 exists prior to the starting point.
37182 Arguments that are not understood by the remote stub will be silently
37185 @item qXfer:memory-map:read::@var{offset},@var{length}
37186 @anchor{qXfer memory map read}
37187 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
37188 annex part of the generic @samp{qXfer} packet must be empty
37189 (@pxref{qXfer read}).
37191 This packet is not probed by default; the remote stub must request it,
37192 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37194 @item qXfer:sdata:read::@var{offset},@var{length}
37195 @anchor{qXfer sdata read}
37197 Read contents of the extra collected static tracepoint marker
37198 information. The annex part of the generic @samp{qXfer} packet must
37199 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
37202 This packet is not probed by default; the remote stub must request it,
37203 by supplying an appropriate @samp{qSupported} response
37204 (@pxref{qSupported}).
37206 @item qXfer:siginfo:read::@var{offset},@var{length}
37207 @anchor{qXfer siginfo read}
37208 Read contents of the extra signal information on the target
37209 system. The annex part of the generic @samp{qXfer} packet must be
37210 empty (@pxref{qXfer read}).
37212 This packet is not probed by default; the remote stub must request it,
37213 by supplying an appropriate @samp{qSupported} response
37214 (@pxref{qSupported}).
37216 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
37217 @anchor{qXfer spu read}
37218 Read contents of an @code{spufs} file on the target system. The
37219 annex specifies which file to read; it must be of the form
37220 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
37221 in the target process, and @var{name} identifes the @code{spufs} file
37222 in that context to be accessed.
37224 This packet is not probed by default; the remote stub must request it,
37225 by supplying an appropriate @samp{qSupported} response
37226 (@pxref{qSupported}).
37228 @item qXfer:threads:read::@var{offset},@var{length}
37229 @anchor{qXfer threads read}
37230 Access the list of threads on target. @xref{Thread List Format}. The
37231 annex part of the generic @samp{qXfer} packet must be empty
37232 (@pxref{qXfer read}).
37234 This packet is not probed by default; the remote stub must request it,
37235 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37237 @item qXfer:traceframe-info:read::@var{offset},@var{length}
37238 @anchor{qXfer traceframe info read}
37240 Return a description of the current traceframe's contents.
37241 @xref{Traceframe Info Format}. The annex part of the generic
37242 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
37244 This packet is not probed by default; the remote stub must request it,
37245 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37247 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
37248 @anchor{qXfer unwind info block}
37250 Return the unwind information block for @var{pc}. This packet is used
37251 on OpenVMS/ia64 to ask the kernel unwind information.
37253 This packet is not probed by default.
37255 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
37256 @anchor{qXfer fdpic loadmap read}
37257 Read contents of @code{loadmap}s on the target system. The
37258 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
37259 executable @code{loadmap} or interpreter @code{loadmap} to read.
37261 This packet is not probed by default; the remote stub must request it,
37262 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37264 @item qXfer:osdata:read::@var{offset},@var{length}
37265 @anchor{qXfer osdata read}
37266 Access the target's @dfn{operating system information}.
37267 @xref{Operating System Information}.
37274 Data @var{data} (@pxref{Binary Data}) has been read from the
37275 target. There may be more data at a higher address (although
37276 it is permitted to return @samp{m} even for the last valid
37277 block of data, as long as at least one byte of data was read).
37278 It is possible for @var{data} to have fewer bytes than the @var{length} in the
37282 Data @var{data} (@pxref{Binary Data}) has been read from the target.
37283 There is no more data to be read. It is possible for @var{data} to
37284 have fewer bytes than the @var{length} in the request.
37287 The @var{offset} in the request is at the end of the data.
37288 There is no more data to be read.
37291 The request was malformed, or @var{annex} was invalid.
37294 The offset was invalid, or there was an error encountered reading the data.
37295 The @var{nn} part is a hex-encoded @code{errno} value.
37298 An empty reply indicates the @var{object} string was not recognized by
37299 the stub, or that the object does not support reading.
37302 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
37303 @cindex write data into object, remote request
37304 @anchor{qXfer write}
37305 Write uninterpreted bytes into the target's special data area
37306 identified by the keyword @var{object}, starting at @var{offset} bytes
37307 into the data. The binary-encoded data (@pxref{Binary Data}) to be
37308 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
37309 is specific to @var{object}; it can supply additional details about what data
37312 Here are the specific requests of this form defined so far. All
37313 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
37314 formats, listed below.
37317 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
37318 @anchor{qXfer siginfo write}
37319 Write @var{data} to the extra signal information on the target system.
37320 The annex part of the generic @samp{qXfer} packet must be
37321 empty (@pxref{qXfer write}).
37323 This packet is not probed by default; the remote stub must request it,
37324 by supplying an appropriate @samp{qSupported} response
37325 (@pxref{qSupported}).
37327 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
37328 @anchor{qXfer spu write}
37329 Write @var{data} to an @code{spufs} file on the target system. The
37330 annex specifies which file to write; it must be of the form
37331 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
37332 in the target process, and @var{name} identifes the @code{spufs} file
37333 in that context to be accessed.
37335 This packet is not probed by default; the remote stub must request it,
37336 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37342 @var{nn} (hex encoded) is the number of bytes written.
37343 This may be fewer bytes than supplied in the request.
37346 The request was malformed, or @var{annex} was invalid.
37349 The offset was invalid, or there was an error encountered writing the data.
37350 The @var{nn} part is a hex-encoded @code{errno} value.
37353 An empty reply indicates the @var{object} string was not
37354 recognized by the stub, or that the object does not support writing.
37357 @item qXfer:@var{object}:@var{operation}:@dots{}
37358 Requests of this form may be added in the future. When a stub does
37359 not recognize the @var{object} keyword, or its support for
37360 @var{object} does not recognize the @var{operation} keyword, the stub
37361 must respond with an empty packet.
37363 @item qAttached:@var{pid}
37364 @cindex query attached, remote request
37365 @cindex @samp{qAttached} packet
37366 Return an indication of whether the remote server attached to an
37367 existing process or created a new process. When the multiprocess
37368 protocol extensions are supported (@pxref{multiprocess extensions}),
37369 @var{pid} is an integer in hexadecimal format identifying the target
37370 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
37371 the query packet will be simplified as @samp{qAttached}.
37373 This query is used, for example, to know whether the remote process
37374 should be detached or killed when a @value{GDBN} session is ended with
37375 the @code{quit} command.
37380 The remote server attached to an existing process.
37382 The remote server created a new process.
37384 A badly formed request or an error was encountered.
37388 Enable branch tracing for the current thread using Branch Trace Store.
37393 Branch tracing has been enabled.
37395 A badly formed request or an error was encountered.
37399 Enable branch tracing for the current thread using Intel(R) Processor Trace.
37404 Branch tracing has been enabled.
37406 A badly formed request or an error was encountered.
37410 Disable branch tracing for the current thread.
37415 Branch tracing has been disabled.
37417 A badly formed request or an error was encountered.
37420 @item Qbtrace-conf:bts:size=@var{value}
37421 Set the requested ring buffer size for new threads that use the
37422 btrace recording method in bts format.
37427 The ring buffer size has been set.
37429 A badly formed request or an error was encountered.
37432 @item Qbtrace-conf:pt:size=@var{value}
37433 Set the requested ring buffer size for new threads that use the
37434 btrace recording method in pt format.
37439 The ring buffer size has been set.
37441 A badly formed request or an error was encountered.
37446 @node Architecture-Specific Protocol Details
37447 @section Architecture-Specific Protocol Details
37449 This section describes how the remote protocol is applied to specific
37450 target architectures. Also see @ref{Standard Target Features}, for
37451 details of XML target descriptions for each architecture.
37454 * ARM-Specific Protocol Details::
37455 * MIPS-Specific Protocol Details::
37458 @node ARM-Specific Protocol Details
37459 @subsection @acronym{ARM}-specific Protocol Details
37462 * ARM Breakpoint Kinds::
37465 @node ARM Breakpoint Kinds
37466 @subsubsection @acronym{ARM} Breakpoint Kinds
37467 @cindex breakpoint kinds, @acronym{ARM}
37469 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
37474 16-bit Thumb mode breakpoint.
37477 32-bit Thumb mode (Thumb-2) breakpoint.
37480 32-bit @acronym{ARM} mode breakpoint.
37484 @node MIPS-Specific Protocol Details
37485 @subsection @acronym{MIPS}-specific Protocol Details
37488 * MIPS Register packet Format::
37489 * MIPS Breakpoint Kinds::
37492 @node MIPS Register packet Format
37493 @subsubsection @acronym{MIPS} Register Packet Format
37494 @cindex register packet format, @acronym{MIPS}
37496 The following @code{g}/@code{G} packets have previously been defined.
37497 In the below, some thirty-two bit registers are transferred as
37498 sixty-four bits. Those registers should be zero/sign extended (which?)
37499 to fill the space allocated. Register bytes are transferred in target
37500 byte order. The two nibbles within a register byte are transferred
37501 most-significant -- least-significant.
37506 All registers are transferred as thirty-two bit quantities in the order:
37507 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
37508 registers; fsr; fir; fp.
37511 All registers are transferred as sixty-four bit quantities (including
37512 thirty-two bit registers such as @code{sr}). The ordering is the same
37517 @node MIPS Breakpoint Kinds
37518 @subsubsection @acronym{MIPS} Breakpoint Kinds
37519 @cindex breakpoint kinds, @acronym{MIPS}
37521 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
37526 16-bit @acronym{MIPS16} mode breakpoint.
37529 16-bit @acronym{microMIPS} mode breakpoint.
37532 32-bit standard @acronym{MIPS} mode breakpoint.
37535 32-bit @acronym{microMIPS} mode breakpoint.
37539 @node Tracepoint Packets
37540 @section Tracepoint Packets
37541 @cindex tracepoint packets
37542 @cindex packets, tracepoint
37544 Here we describe the packets @value{GDBN} uses to implement
37545 tracepoints (@pxref{Tracepoints}).
37549 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
37550 @cindex @samp{QTDP} packet
37551 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
37552 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
37553 the tracepoint is disabled. The @var{step} gives the tracepoint's step
37554 count, and @var{pass} gives its pass count. If an @samp{F} is present,
37555 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
37556 the number of bytes that the target should copy elsewhere to make room
37557 for the tracepoint. If an @samp{X} is present, it introduces a
37558 tracepoint condition, which consists of a hexadecimal length, followed
37559 by a comma and hex-encoded bytes, in a manner similar to action
37560 encodings as described below. If the trailing @samp{-} is present,
37561 further @samp{QTDP} packets will follow to specify this tracepoint's
37567 The packet was understood and carried out.
37569 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
37571 The packet was not recognized.
37574 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
37575 Define actions to be taken when a tracepoint is hit. The @var{n} and
37576 @var{addr} must be the same as in the initial @samp{QTDP} packet for
37577 this tracepoint. This packet may only be sent immediately after
37578 another @samp{QTDP} packet that ended with a @samp{-}. If the
37579 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
37580 specifying more actions for this tracepoint.
37582 In the series of action packets for a given tracepoint, at most one
37583 can have an @samp{S} before its first @var{action}. If such a packet
37584 is sent, it and the following packets define ``while-stepping''
37585 actions. Any prior packets define ordinary actions --- that is, those
37586 taken when the tracepoint is first hit. If no action packet has an
37587 @samp{S}, then all the packets in the series specify ordinary
37588 tracepoint actions.
37590 The @samp{@var{action}@dots{}} portion of the packet is a series of
37591 actions, concatenated without separators. Each action has one of the
37597 Collect the registers whose bits are set in @var{mask},
37598 a hexadecimal number whose @var{i}'th bit is set if register number
37599 @var{i} should be collected. (The least significant bit is numbered
37600 zero.) Note that @var{mask} may be any number of digits long; it may
37601 not fit in a 32-bit word.
37603 @item M @var{basereg},@var{offset},@var{len}
37604 Collect @var{len} bytes of memory starting at the address in register
37605 number @var{basereg}, plus @var{offset}. If @var{basereg} is
37606 @samp{-1}, then the range has a fixed address: @var{offset} is the
37607 address of the lowest byte to collect. The @var{basereg},
37608 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
37609 values (the @samp{-1} value for @var{basereg} is a special case).
37611 @item X @var{len},@var{expr}
37612 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
37613 it directs. The agent expression @var{expr} is as described in
37614 @ref{Agent Expressions}. Each byte of the expression is encoded as a
37615 two-digit hex number in the packet; @var{len} is the number of bytes
37616 in the expression (and thus one-half the number of hex digits in the
37621 Any number of actions may be packed together in a single @samp{QTDP}
37622 packet, as long as the packet does not exceed the maximum packet
37623 length (400 bytes, for many stubs). There may be only one @samp{R}
37624 action per tracepoint, and it must precede any @samp{M} or @samp{X}
37625 actions. Any registers referred to by @samp{M} and @samp{X} actions
37626 must be collected by a preceding @samp{R} action. (The
37627 ``while-stepping'' actions are treated as if they were attached to a
37628 separate tracepoint, as far as these restrictions are concerned.)
37633 The packet was understood and carried out.
37635 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
37637 The packet was not recognized.
37640 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
37641 @cindex @samp{QTDPsrc} packet
37642 Specify a source string of tracepoint @var{n} at address @var{addr}.
37643 This is useful to get accurate reproduction of the tracepoints
37644 originally downloaded at the beginning of the trace run. The @var{type}
37645 is the name of the tracepoint part, such as @samp{cond} for the
37646 tracepoint's conditional expression (see below for a list of types), while
37647 @var{bytes} is the string, encoded in hexadecimal.
37649 @var{start} is the offset of the @var{bytes} within the overall source
37650 string, while @var{slen} is the total length of the source string.
37651 This is intended for handling source strings that are longer than will
37652 fit in a single packet.
37653 @c Add detailed example when this info is moved into a dedicated
37654 @c tracepoint descriptions section.
37656 The available string types are @samp{at} for the location,
37657 @samp{cond} for the conditional, and @samp{cmd} for an action command.
37658 @value{GDBN} sends a separate packet for each command in the action
37659 list, in the same order in which the commands are stored in the list.
37661 The target does not need to do anything with source strings except
37662 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
37665 Although this packet is optional, and @value{GDBN} will only send it
37666 if the target replies with @samp{TracepointSource} @xref{General
37667 Query Packets}, it makes both disconnected tracing and trace files
37668 much easier to use. Otherwise the user must be careful that the
37669 tracepoints in effect while looking at trace frames are identical to
37670 the ones in effect during the trace run; even a small discrepancy
37671 could cause @samp{tdump} not to work, or a particular trace frame not
37674 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
37675 @cindex define trace state variable, remote request
37676 @cindex @samp{QTDV} packet
37677 Create a new trace state variable, number @var{n}, with an initial
37678 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
37679 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
37680 the option of not using this packet for initial values of zero; the
37681 target should simply create the trace state variables as they are
37682 mentioned in expressions. The value @var{builtin} should be 1 (one)
37683 if the trace state variable is builtin and 0 (zero) if it is not builtin.
37684 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
37685 @samp{qTsV} packet had it set. The contents of @var{name} is the
37686 hex-encoded name (without the leading @samp{$}) of the trace state
37689 @item QTFrame:@var{n}
37690 @cindex @samp{QTFrame} packet
37691 Select the @var{n}'th tracepoint frame from the buffer, and use the
37692 register and memory contents recorded there to answer subsequent
37693 request packets from @value{GDBN}.
37695 A successful reply from the stub indicates that the stub has found the
37696 requested frame. The response is a series of parts, concatenated
37697 without separators, describing the frame we selected. Each part has
37698 one of the following forms:
37702 The selected frame is number @var{n} in the trace frame buffer;
37703 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
37704 was no frame matching the criteria in the request packet.
37707 The selected trace frame records a hit of tracepoint number @var{t};
37708 @var{t} is a hexadecimal number.
37712 @item QTFrame:pc:@var{addr}
37713 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37714 currently selected frame whose PC is @var{addr};
37715 @var{addr} is a hexadecimal number.
37717 @item QTFrame:tdp:@var{t}
37718 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37719 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
37720 is a hexadecimal number.
37722 @item QTFrame:range:@var{start}:@var{end}
37723 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37724 currently selected frame whose PC is between @var{start} (inclusive)
37725 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
37728 @item QTFrame:outside:@var{start}:@var{end}
37729 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
37730 frame @emph{outside} the given range of addresses (exclusive).
37733 @cindex @samp{qTMinFTPILen} packet
37734 This packet requests the minimum length of instruction at which a fast
37735 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
37736 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
37737 it depends on the target system being able to create trampolines in
37738 the first 64K of memory, which might or might not be possible for that
37739 system. So the reply to this packet will be 4 if it is able to
37746 The minimum instruction length is currently unknown.
37748 The minimum instruction length is @var{length}, where @var{length}
37749 is a hexadecimal number greater or equal to 1. A reply
37750 of 1 means that a fast tracepoint may be placed on any instruction
37751 regardless of size.
37753 An error has occurred.
37755 An empty reply indicates that the request is not supported by the stub.
37759 @cindex @samp{QTStart} packet
37760 Begin the tracepoint experiment. Begin collecting data from
37761 tracepoint hits in the trace frame buffer. This packet supports the
37762 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
37763 instruction reply packet}).
37766 @cindex @samp{QTStop} packet
37767 End the tracepoint experiment. Stop collecting trace frames.
37769 @item QTEnable:@var{n}:@var{addr}
37771 @cindex @samp{QTEnable} packet
37772 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
37773 experiment. If the tracepoint was previously disabled, then collection
37774 of data from it will resume.
37776 @item QTDisable:@var{n}:@var{addr}
37778 @cindex @samp{QTDisable} packet
37779 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
37780 experiment. No more data will be collected from the tracepoint unless
37781 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
37784 @cindex @samp{QTinit} packet
37785 Clear the table of tracepoints, and empty the trace frame buffer.
37787 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
37788 @cindex @samp{QTro} packet
37789 Establish the given ranges of memory as ``transparent''. The stub
37790 will answer requests for these ranges from memory's current contents,
37791 if they were not collected as part of the tracepoint hit.
37793 @value{GDBN} uses this to mark read-only regions of memory, like those
37794 containing program code. Since these areas never change, they should
37795 still have the same contents they did when the tracepoint was hit, so
37796 there's no reason for the stub to refuse to provide their contents.
37798 @item QTDisconnected:@var{value}
37799 @cindex @samp{QTDisconnected} packet
37800 Set the choice to what to do with the tracing run when @value{GDBN}
37801 disconnects from the target. A @var{value} of 1 directs the target to
37802 continue the tracing run, while 0 tells the target to stop tracing if
37803 @value{GDBN} is no longer in the picture.
37806 @cindex @samp{qTStatus} packet
37807 Ask the stub if there is a trace experiment running right now.
37809 The reply has the form:
37813 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
37814 @var{running} is a single digit @code{1} if the trace is presently
37815 running, or @code{0} if not. It is followed by semicolon-separated
37816 optional fields that an agent may use to report additional status.
37820 If the trace is not running, the agent may report any of several
37821 explanations as one of the optional fields:
37826 No trace has been run yet.
37828 @item tstop[:@var{text}]:0
37829 The trace was stopped by a user-originated stop command. The optional
37830 @var{text} field is a user-supplied string supplied as part of the
37831 stop command (for instance, an explanation of why the trace was
37832 stopped manually). It is hex-encoded.
37835 The trace stopped because the trace buffer filled up.
37837 @item tdisconnected:0
37838 The trace stopped because @value{GDBN} disconnected from the target.
37840 @item tpasscount:@var{tpnum}
37841 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
37843 @item terror:@var{text}:@var{tpnum}
37844 The trace stopped because tracepoint @var{tpnum} had an error. The
37845 string @var{text} is available to describe the nature of the error
37846 (for instance, a divide by zero in the condition expression); it
37850 The trace stopped for some other reason.
37854 Additional optional fields supply statistical and other information.
37855 Although not required, they are extremely useful for users monitoring
37856 the progress of a trace run. If a trace has stopped, and these
37857 numbers are reported, they must reflect the state of the just-stopped
37862 @item tframes:@var{n}
37863 The number of trace frames in the buffer.
37865 @item tcreated:@var{n}
37866 The total number of trace frames created during the run. This may
37867 be larger than the trace frame count, if the buffer is circular.
37869 @item tsize:@var{n}
37870 The total size of the trace buffer, in bytes.
37872 @item tfree:@var{n}
37873 The number of bytes still unused in the buffer.
37875 @item circular:@var{n}
37876 The value of the circular trace buffer flag. @code{1} means that the
37877 trace buffer is circular and old trace frames will be discarded if
37878 necessary to make room, @code{0} means that the trace buffer is linear
37881 @item disconn:@var{n}
37882 The value of the disconnected tracing flag. @code{1} means that
37883 tracing will continue after @value{GDBN} disconnects, @code{0} means
37884 that the trace run will stop.
37888 @item qTP:@var{tp}:@var{addr}
37889 @cindex tracepoint status, remote request
37890 @cindex @samp{qTP} packet
37891 Ask the stub for the current state of tracepoint number @var{tp} at
37892 address @var{addr}.
37896 @item V@var{hits}:@var{usage}
37897 The tracepoint has been hit @var{hits} times so far during the trace
37898 run, and accounts for @var{usage} in the trace buffer. Note that
37899 @code{while-stepping} steps are not counted as separate hits, but the
37900 steps' space consumption is added into the usage number.
37904 @item qTV:@var{var}
37905 @cindex trace state variable value, remote request
37906 @cindex @samp{qTV} packet
37907 Ask the stub for the value of the trace state variable number @var{var}.
37912 The value of the variable is @var{value}. This will be the current
37913 value of the variable if the user is examining a running target, or a
37914 saved value if the variable was collected in the trace frame that the
37915 user is looking at. Note that multiple requests may result in
37916 different reply values, such as when requesting values while the
37917 program is running.
37920 The value of the variable is unknown. This would occur, for example,
37921 if the user is examining a trace frame in which the requested variable
37926 @cindex @samp{qTfP} packet
37928 @cindex @samp{qTsP} packet
37929 These packets request data about tracepoints that are being used by
37930 the target. @value{GDBN} sends @code{qTfP} to get the first piece
37931 of data, and multiple @code{qTsP} to get additional pieces. Replies
37932 to these packets generally take the form of the @code{QTDP} packets
37933 that define tracepoints. (FIXME add detailed syntax)
37936 @cindex @samp{qTfV} packet
37938 @cindex @samp{qTsV} packet
37939 These packets request data about trace state variables that are on the
37940 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
37941 and multiple @code{qTsV} to get additional variables. Replies to
37942 these packets follow the syntax of the @code{QTDV} packets that define
37943 trace state variables.
37949 @cindex @samp{qTfSTM} packet
37950 @cindex @samp{qTsSTM} packet
37951 These packets request data about static tracepoint markers that exist
37952 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
37953 first piece of data, and multiple @code{qTsSTM} to get additional
37954 pieces. Replies to these packets take the following form:
37958 @item m @var{address}:@var{id}:@var{extra}
37960 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
37961 a comma-separated list of markers
37963 (lower case letter @samp{L}) denotes end of list.
37965 An error occurred. The error number @var{nn} is given as hex digits.
37967 An empty reply indicates that the request is not supported by the
37971 The @var{address} is encoded in hex;
37972 @var{id} and @var{extra} are strings encoded in hex.
37974 In response to each query, the target will reply with a list of one or
37975 more markers, separated by commas. @value{GDBN} will respond to each
37976 reply with a request for more markers (using the @samp{qs} form of the
37977 query), until the target responds with @samp{l} (lower-case ell, for
37980 @item qTSTMat:@var{address}
37982 @cindex @samp{qTSTMat} packet
37983 This packets requests data about static tracepoint markers in the
37984 target program at @var{address}. Replies to this packet follow the
37985 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
37986 tracepoint markers.
37988 @item QTSave:@var{filename}
37989 @cindex @samp{QTSave} packet
37990 This packet directs the target to save trace data to the file name
37991 @var{filename} in the target's filesystem. The @var{filename} is encoded
37992 as a hex string; the interpretation of the file name (relative vs
37993 absolute, wild cards, etc) is up to the target.
37995 @item qTBuffer:@var{offset},@var{len}
37996 @cindex @samp{qTBuffer} packet
37997 Return up to @var{len} bytes of the current contents of trace buffer,
37998 starting at @var{offset}. The trace buffer is treated as if it were
37999 a contiguous collection of traceframes, as per the trace file format.
38000 The reply consists as many hex-encoded bytes as the target can deliver
38001 in a packet; it is not an error to return fewer than were asked for.
38002 A reply consisting of just @code{l} indicates that no bytes are
38005 @item QTBuffer:circular:@var{value}
38006 This packet directs the target to use a circular trace buffer if
38007 @var{value} is 1, or a linear buffer if the value is 0.
38009 @item QTBuffer:size:@var{size}
38010 @anchor{QTBuffer-size}
38011 @cindex @samp{QTBuffer size} packet
38012 This packet directs the target to make the trace buffer be of size
38013 @var{size} if possible. A value of @code{-1} tells the target to
38014 use whatever size it prefers.
38016 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
38017 @cindex @samp{QTNotes} packet
38018 This packet adds optional textual notes to the trace run. Allowable
38019 types include @code{user}, @code{notes}, and @code{tstop}, the
38020 @var{text} fields are arbitrary strings, hex-encoded.
38024 @subsection Relocate instruction reply packet
38025 When installing fast tracepoints in memory, the target may need to
38026 relocate the instruction currently at the tracepoint address to a
38027 different address in memory. For most instructions, a simple copy is
38028 enough, but, for example, call instructions that implicitly push the
38029 return address on the stack, and relative branches or other
38030 PC-relative instructions require offset adjustment, so that the effect
38031 of executing the instruction at a different address is the same as if
38032 it had executed in the original location.
38034 In response to several of the tracepoint packets, the target may also
38035 respond with a number of intermediate @samp{qRelocInsn} request
38036 packets before the final result packet, to have @value{GDBN} handle
38037 this relocation operation. If a packet supports this mechanism, its
38038 documentation will explicitly say so. See for example the above
38039 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
38040 format of the request is:
38043 @item qRelocInsn:@var{from};@var{to}
38045 This requests @value{GDBN} to copy instruction at address @var{from}
38046 to address @var{to}, possibly adjusted so that executing the
38047 instruction at @var{to} has the same effect as executing it at
38048 @var{from}. @value{GDBN} writes the adjusted instruction to target
38049 memory starting at @var{to}.
38054 @item qRelocInsn:@var{adjusted_size}
38055 Informs the stub the relocation is complete. The @var{adjusted_size} is
38056 the length in bytes of resulting relocated instruction sequence.
38058 A badly formed request was detected, or an error was encountered while
38059 relocating the instruction.
38062 @node Host I/O Packets
38063 @section Host I/O Packets
38064 @cindex Host I/O, remote protocol
38065 @cindex file transfer, remote protocol
38067 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
38068 operations on the far side of a remote link. For example, Host I/O is
38069 used to upload and download files to a remote target with its own
38070 filesystem. Host I/O uses the same constant values and data structure
38071 layout as the target-initiated File-I/O protocol. However, the
38072 Host I/O packets are structured differently. The target-initiated
38073 protocol relies on target memory to store parameters and buffers.
38074 Host I/O requests are initiated by @value{GDBN}, and the
38075 target's memory is not involved. @xref{File-I/O Remote Protocol
38076 Extension}, for more details on the target-initiated protocol.
38078 The Host I/O request packets all encode a single operation along with
38079 its arguments. They have this format:
38083 @item vFile:@var{operation}: @var{parameter}@dots{}
38084 @var{operation} is the name of the particular request; the target
38085 should compare the entire packet name up to the second colon when checking
38086 for a supported operation. The format of @var{parameter} depends on
38087 the operation. Numbers are always passed in hexadecimal. Negative
38088 numbers have an explicit minus sign (i.e.@: two's complement is not
38089 used). Strings (e.g.@: filenames) are encoded as a series of
38090 hexadecimal bytes. The last argument to a system call may be a
38091 buffer of escaped binary data (@pxref{Binary Data}).
38095 The valid responses to Host I/O packets are:
38099 @item F @var{result} [, @var{errno}] [; @var{attachment}]
38100 @var{result} is the integer value returned by this operation, usually
38101 non-negative for success and -1 for errors. If an error has occured,
38102 @var{errno} will be included in the result specifying a
38103 value defined by the File-I/O protocol (@pxref{Errno Values}). For
38104 operations which return data, @var{attachment} supplies the data as a
38105 binary buffer. Binary buffers in response packets are escaped in the
38106 normal way (@pxref{Binary Data}). See the individual packet
38107 documentation for the interpretation of @var{result} and
38111 An empty response indicates that this operation is not recognized.
38115 These are the supported Host I/O operations:
38118 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
38119 Open a file at @var{filename} and return a file descriptor for it, or
38120 return -1 if an error occurs. The @var{filename} is a string,
38121 @var{flags} is an integer indicating a mask of open flags
38122 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
38123 of mode bits to use if the file is created (@pxref{mode_t Values}).
38124 @xref{open}, for details of the open flags and mode values.
38126 @item vFile:close: @var{fd}
38127 Close the open file corresponding to @var{fd} and return 0, or
38128 -1 if an error occurs.
38130 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
38131 Read data from the open file corresponding to @var{fd}. Up to
38132 @var{count} bytes will be read from the file, starting at @var{offset}
38133 relative to the start of the file. The target may read fewer bytes;
38134 common reasons include packet size limits and an end-of-file
38135 condition. The number of bytes read is returned. Zero should only be
38136 returned for a successful read at the end of the file, or if
38137 @var{count} was zero.
38139 The data read should be returned as a binary attachment on success.
38140 If zero bytes were read, the response should include an empty binary
38141 attachment (i.e.@: a trailing semicolon). The return value is the
38142 number of target bytes read; the binary attachment may be longer if
38143 some characters were escaped.
38145 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
38146 Write @var{data} (a binary buffer) to the open file corresponding
38147 to @var{fd}. Start the write at @var{offset} from the start of the
38148 file. Unlike many @code{write} system calls, there is no
38149 separate @var{count} argument; the length of @var{data} in the
38150 packet is used. @samp{vFile:write} returns the number of bytes written,
38151 which may be shorter than the length of @var{data}, or -1 if an
38154 @item vFile:fstat: @var{fd}
38155 Get information about the open file corresponding to @var{fd}.
38156 On success the information is returned as a binary attachment
38157 and the return value is the size of this attachment in bytes.
38158 If an error occurs the return value is -1. The format of the
38159 returned binary attachment is as described in @ref{struct stat}.
38161 @item vFile:unlink: @var{filename}
38162 Delete the file at @var{filename} on the target. Return 0,
38163 or -1 if an error occurs. The @var{filename} is a string.
38165 @item vFile:readlink: @var{filename}
38166 Read value of symbolic link @var{filename} on the target. Return
38167 the number of bytes read, or -1 if an error occurs.
38169 The data read should be returned as a binary attachment on success.
38170 If zero bytes were read, the response should include an empty binary
38171 attachment (i.e.@: a trailing semicolon). The return value is the
38172 number of target bytes read; the binary attachment may be longer if
38173 some characters were escaped.
38175 @item vFile:setfs: @var{pid}
38176 Select the filesystem on which @code{vFile} operations with
38177 @var{filename} arguments will operate. This is required for
38178 @value{GDBN} to be able to access files on remote targets where
38179 the remote stub does not share a common filesystem with the
38182 If @var{pid} is nonzero, select the filesystem as seen by process
38183 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
38184 the remote stub. Return 0 on success, or -1 if an error occurs.
38185 If @code{vFile:setfs:} indicates success, the selected filesystem
38186 remains selected until the next successful @code{vFile:setfs:}
38192 @section Interrupts
38193 @cindex interrupts (remote protocol)
38195 When a program on the remote target is running, @value{GDBN} may
38196 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
38197 a @code{BREAK} followed by @code{g},
38198 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
38200 The precise meaning of @code{BREAK} is defined by the transport
38201 mechanism and may, in fact, be undefined. @value{GDBN} does not
38202 currently define a @code{BREAK} mechanism for any of the network
38203 interfaces except for TCP, in which case @value{GDBN} sends the
38204 @code{telnet} BREAK sequence.
38206 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
38207 transport mechanisms. It is represented by sending the single byte
38208 @code{0x03} without any of the usual packet overhead described in
38209 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
38210 transmitted as part of a packet, it is considered to be packet data
38211 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
38212 (@pxref{X packet}), used for binary downloads, may include an unescaped
38213 @code{0x03} as part of its packet.
38215 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
38216 When Linux kernel receives this sequence from serial port,
38217 it stops execution and connects to gdb.
38219 Stubs are not required to recognize these interrupt mechanisms and the
38220 precise meaning associated with receipt of the interrupt is
38221 implementation defined. If the target supports debugging of multiple
38222 threads and/or processes, it should attempt to interrupt all
38223 currently-executing threads and processes.
38224 If the stub is successful at interrupting the
38225 running program, it should send one of the stop
38226 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
38227 of successfully stopping the program in all-stop mode, and a stop reply
38228 for each stopped thread in non-stop mode.
38229 Interrupts received while the
38230 program is stopped are discarded.
38232 @node Notification Packets
38233 @section Notification Packets
38234 @cindex notification packets
38235 @cindex packets, notification
38237 The @value{GDBN} remote serial protocol includes @dfn{notifications},
38238 packets that require no acknowledgment. Both the GDB and the stub
38239 may send notifications (although the only notifications defined at
38240 present are sent by the stub). Notifications carry information
38241 without incurring the round-trip latency of an acknowledgment, and so
38242 are useful for low-impact communications where occasional packet loss
38245 A notification packet has the form @samp{% @var{data} #
38246 @var{checksum}}, where @var{data} is the content of the notification,
38247 and @var{checksum} is a checksum of @var{data}, computed and formatted
38248 as for ordinary @value{GDBN} packets. A notification's @var{data}
38249 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
38250 receiving a notification, the recipient sends no @samp{+} or @samp{-}
38251 to acknowledge the notification's receipt or to report its corruption.
38253 Every notification's @var{data} begins with a name, which contains no
38254 colon characters, followed by a colon character.
38256 Recipients should silently ignore corrupted notifications and
38257 notifications they do not understand. Recipients should restart
38258 timeout periods on receipt of a well-formed notification, whether or
38259 not they understand it.
38261 Senders should only send the notifications described here when this
38262 protocol description specifies that they are permitted. In the
38263 future, we may extend the protocol to permit existing notifications in
38264 new contexts; this rule helps older senders avoid confusing newer
38267 (Older versions of @value{GDBN} ignore bytes received until they see
38268 the @samp{$} byte that begins an ordinary packet, so new stubs may
38269 transmit notifications without fear of confusing older clients. There
38270 are no notifications defined for @value{GDBN} to send at the moment, but we
38271 assume that most older stubs would ignore them, as well.)
38273 Each notification is comprised of three parts:
38275 @item @var{name}:@var{event}
38276 The notification packet is sent by the side that initiates the
38277 exchange (currently, only the stub does that), with @var{event}
38278 carrying the specific information about the notification, and
38279 @var{name} specifying the name of the notification.
38281 The acknowledge sent by the other side, usually @value{GDBN}, to
38282 acknowledge the exchange and request the event.
38285 The purpose of an asynchronous notification mechanism is to report to
38286 @value{GDBN} that something interesting happened in the remote stub.
38288 The remote stub may send notification @var{name}:@var{event}
38289 at any time, but @value{GDBN} acknowledges the notification when
38290 appropriate. The notification event is pending before @value{GDBN}
38291 acknowledges. Only one notification at a time may be pending; if
38292 additional events occur before @value{GDBN} has acknowledged the
38293 previous notification, they must be queued by the stub for later
38294 synchronous transmission in response to @var{ack} packets from
38295 @value{GDBN}. Because the notification mechanism is unreliable,
38296 the stub is permitted to resend a notification if it believes
38297 @value{GDBN} may not have received it.
38299 Specifically, notifications may appear when @value{GDBN} is not
38300 otherwise reading input from the stub, or when @value{GDBN} is
38301 expecting to read a normal synchronous response or a
38302 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
38303 Notification packets are distinct from any other communication from
38304 the stub so there is no ambiguity.
38306 After receiving a notification, @value{GDBN} shall acknowledge it by
38307 sending a @var{ack} packet as a regular, synchronous request to the
38308 stub. Such acknowledgment is not required to happen immediately, as
38309 @value{GDBN} is permitted to send other, unrelated packets to the
38310 stub first, which the stub should process normally.
38312 Upon receiving a @var{ack} packet, if the stub has other queued
38313 events to report to @value{GDBN}, it shall respond by sending a
38314 normal @var{event}. @value{GDBN} shall then send another @var{ack}
38315 packet to solicit further responses; again, it is permitted to send
38316 other, unrelated packets as well which the stub should process
38319 If the stub receives a @var{ack} packet and there are no additional
38320 @var{event} to report, the stub shall return an @samp{OK} response.
38321 At this point, @value{GDBN} has finished processing a notification
38322 and the stub has completed sending any queued events. @value{GDBN}
38323 won't accept any new notifications until the final @samp{OK} is
38324 received . If further notification events occur, the stub shall send
38325 a new notification, @value{GDBN} shall accept the notification, and
38326 the process shall be repeated.
38328 The process of asynchronous notification can be illustrated by the
38331 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
38334 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
38336 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
38341 The following notifications are defined:
38342 @multitable @columnfractions 0.12 0.12 0.38 0.38
38351 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
38352 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
38353 for information on how these notifications are acknowledged by
38355 @tab Report an asynchronous stop event in non-stop mode.
38359 @node Remote Non-Stop
38360 @section Remote Protocol Support for Non-Stop Mode
38362 @value{GDBN}'s remote protocol supports non-stop debugging of
38363 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
38364 supports non-stop mode, it should report that to @value{GDBN} by including
38365 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
38367 @value{GDBN} typically sends a @samp{QNonStop} packet only when
38368 establishing a new connection with the stub. Entering non-stop mode
38369 does not alter the state of any currently-running threads, but targets
38370 must stop all threads in any already-attached processes when entering
38371 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
38372 probe the target state after a mode change.
38374 In non-stop mode, when an attached process encounters an event that
38375 would otherwise be reported with a stop reply, it uses the
38376 asynchronous notification mechanism (@pxref{Notification Packets}) to
38377 inform @value{GDBN}. In contrast to all-stop mode, where all threads
38378 in all processes are stopped when a stop reply is sent, in non-stop
38379 mode only the thread reporting the stop event is stopped. That is,
38380 when reporting a @samp{S} or @samp{T} response to indicate completion
38381 of a step operation, hitting a breakpoint, or a fault, only the
38382 affected thread is stopped; any other still-running threads continue
38383 to run. When reporting a @samp{W} or @samp{X} response, all running
38384 threads belonging to other attached processes continue to run.
38386 In non-stop mode, the target shall respond to the @samp{?} packet as
38387 follows. First, any incomplete stop reply notification/@samp{vStopped}
38388 sequence in progress is abandoned. The target must begin a new
38389 sequence reporting stop events for all stopped threads, whether or not
38390 it has previously reported those events to @value{GDBN}. The first
38391 stop reply is sent as a synchronous reply to the @samp{?} packet, and
38392 subsequent stop replies are sent as responses to @samp{vStopped} packets
38393 using the mechanism described above. The target must not send
38394 asynchronous stop reply notifications until the sequence is complete.
38395 If all threads are running when the target receives the @samp{?} packet,
38396 or if the target is not attached to any process, it shall respond
38399 If the stub supports non-stop mode, it should also support the
38400 @samp{swbreak} stop reason if software breakpoints are supported, and
38401 the @samp{hwbreak} stop reason if hardware breakpoints are supported
38402 (@pxref{swbreak stop reason}). This is because given the asynchronous
38403 nature of non-stop mode, between the time a thread hits a breakpoint
38404 and the time the event is finally processed by @value{GDBN}, the
38405 breakpoint may have already been removed from the target. Due to
38406 this, @value{GDBN} needs to be able to tell whether a trap stop was
38407 caused by a delayed breakpoint event, which should be ignored, as
38408 opposed to a random trap signal, which should be reported to the user.
38409 Note the @samp{swbreak} feature implies that the target is responsible
38410 for adjusting the PC when a software breakpoint triggers, if
38411 necessary, such as on the x86 architecture.
38413 @node Packet Acknowledgment
38414 @section Packet Acknowledgment
38416 @cindex acknowledgment, for @value{GDBN} remote
38417 @cindex packet acknowledgment, for @value{GDBN} remote
38418 By default, when either the host or the target machine receives a packet,
38419 the first response expected is an acknowledgment: either @samp{+} (to indicate
38420 the package was received correctly) or @samp{-} (to request retransmission).
38421 This mechanism allows the @value{GDBN} remote protocol to operate over
38422 unreliable transport mechanisms, such as a serial line.
38424 In cases where the transport mechanism is itself reliable (such as a pipe or
38425 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
38426 It may be desirable to disable them in that case to reduce communication
38427 overhead, or for other reasons. This can be accomplished by means of the
38428 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
38430 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
38431 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
38432 and response format still includes the normal checksum, as described in
38433 @ref{Overview}, but the checksum may be ignored by the receiver.
38435 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
38436 no-acknowledgment mode, it should report that to @value{GDBN}
38437 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
38438 @pxref{qSupported}.
38439 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
38440 disabled via the @code{set remote noack-packet off} command
38441 (@pxref{Remote Configuration}),
38442 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
38443 Only then may the stub actually turn off packet acknowledgments.
38444 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
38445 response, which can be safely ignored by the stub.
38447 Note that @code{set remote noack-packet} command only affects negotiation
38448 between @value{GDBN} and the stub when subsequent connections are made;
38449 it does not affect the protocol acknowledgment state for any current
38451 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
38452 new connection is established,
38453 there is also no protocol request to re-enable the acknowledgments
38454 for the current connection, once disabled.
38459 Example sequence of a target being re-started. Notice how the restart
38460 does not get any direct output:
38465 @emph{target restarts}
38468 <- @code{T001:1234123412341234}
38472 Example sequence of a target being stepped by a single instruction:
38475 -> @code{G1445@dots{}}
38480 <- @code{T001:1234123412341234}
38484 <- @code{1455@dots{}}
38488 @node File-I/O Remote Protocol Extension
38489 @section File-I/O Remote Protocol Extension
38490 @cindex File-I/O remote protocol extension
38493 * File-I/O Overview::
38494 * Protocol Basics::
38495 * The F Request Packet::
38496 * The F Reply Packet::
38497 * The Ctrl-C Message::
38499 * List of Supported Calls::
38500 * Protocol-specific Representation of Datatypes::
38502 * File-I/O Examples::
38505 @node File-I/O Overview
38506 @subsection File-I/O Overview
38507 @cindex file-i/o overview
38509 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
38510 target to use the host's file system and console I/O to perform various
38511 system calls. System calls on the target system are translated into a
38512 remote protocol packet to the host system, which then performs the needed
38513 actions and returns a response packet to the target system.
38514 This simulates file system operations even on targets that lack file systems.
38516 The protocol is defined to be independent of both the host and target systems.
38517 It uses its own internal representation of datatypes and values. Both
38518 @value{GDBN} and the target's @value{GDBN} stub are responsible for
38519 translating the system-dependent value representations into the internal
38520 protocol representations when data is transmitted.
38522 The communication is synchronous. A system call is possible only when
38523 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
38524 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
38525 the target is stopped to allow deterministic access to the target's
38526 memory. Therefore File-I/O is not interruptible by target signals. On
38527 the other hand, it is possible to interrupt File-I/O by a user interrupt
38528 (@samp{Ctrl-C}) within @value{GDBN}.
38530 The target's request to perform a host system call does not finish
38531 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
38532 after finishing the system call, the target returns to continuing the
38533 previous activity (continue, step). No additional continue or step
38534 request from @value{GDBN} is required.
38537 (@value{GDBP}) continue
38538 <- target requests 'system call X'
38539 target is stopped, @value{GDBN} executes system call
38540 -> @value{GDBN} returns result
38541 ... target continues, @value{GDBN} returns to wait for the target
38542 <- target hits breakpoint and sends a Txx packet
38545 The protocol only supports I/O on the console and to regular files on
38546 the host file system. Character or block special devices, pipes,
38547 named pipes, sockets or any other communication method on the host
38548 system are not supported by this protocol.
38550 File I/O is not supported in non-stop mode.
38552 @node Protocol Basics
38553 @subsection Protocol Basics
38554 @cindex protocol basics, file-i/o
38556 The File-I/O protocol uses the @code{F} packet as the request as well
38557 as reply packet. Since a File-I/O system call can only occur when
38558 @value{GDBN} is waiting for a response from the continuing or stepping target,
38559 the File-I/O request is a reply that @value{GDBN} has to expect as a result
38560 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
38561 This @code{F} packet contains all information needed to allow @value{GDBN}
38562 to call the appropriate host system call:
38566 A unique identifier for the requested system call.
38569 All parameters to the system call. Pointers are given as addresses
38570 in the target memory address space. Pointers to strings are given as
38571 pointer/length pair. Numerical values are given as they are.
38572 Numerical control flags are given in a protocol-specific representation.
38576 At this point, @value{GDBN} has to perform the following actions.
38580 If the parameters include pointer values to data needed as input to a
38581 system call, @value{GDBN} requests this data from the target with a
38582 standard @code{m} packet request. This additional communication has to be
38583 expected by the target implementation and is handled as any other @code{m}
38587 @value{GDBN} translates all value from protocol representation to host
38588 representation as needed. Datatypes are coerced into the host types.
38591 @value{GDBN} calls the system call.
38594 It then coerces datatypes back to protocol representation.
38597 If the system call is expected to return data in buffer space specified
38598 by pointer parameters to the call, the data is transmitted to the
38599 target using a @code{M} or @code{X} packet. This packet has to be expected
38600 by the target implementation and is handled as any other @code{M} or @code{X}
38605 Eventually @value{GDBN} replies with another @code{F} packet which contains all
38606 necessary information for the target to continue. This at least contains
38613 @code{errno}, if has been changed by the system call.
38620 After having done the needed type and value coercion, the target continues
38621 the latest continue or step action.
38623 @node The F Request Packet
38624 @subsection The @code{F} Request Packet
38625 @cindex file-i/o request packet
38626 @cindex @code{F} request packet
38628 The @code{F} request packet has the following format:
38631 @item F@var{call-id},@var{parameter@dots{}}
38633 @var{call-id} is the identifier to indicate the host system call to be called.
38634 This is just the name of the function.
38636 @var{parameter@dots{}} are the parameters to the system call.
38637 Parameters are hexadecimal integer values, either the actual values in case
38638 of scalar datatypes, pointers to target buffer space in case of compound
38639 datatypes and unspecified memory areas, or pointer/length pairs in case
38640 of string parameters. These are appended to the @var{call-id} as a
38641 comma-delimited list. All values are transmitted in ASCII
38642 string representation, pointer/length pairs separated by a slash.
38648 @node The F Reply Packet
38649 @subsection The @code{F} Reply Packet
38650 @cindex file-i/o reply packet
38651 @cindex @code{F} reply packet
38653 The @code{F} reply packet has the following format:
38657 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
38659 @var{retcode} is the return code of the system call as hexadecimal value.
38661 @var{errno} is the @code{errno} set by the call, in protocol-specific
38663 This parameter can be omitted if the call was successful.
38665 @var{Ctrl-C flag} is only sent if the user requested a break. In this
38666 case, @var{errno} must be sent as well, even if the call was successful.
38667 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
38674 or, if the call was interrupted before the host call has been performed:
38681 assuming 4 is the protocol-specific representation of @code{EINTR}.
38686 @node The Ctrl-C Message
38687 @subsection The @samp{Ctrl-C} Message
38688 @cindex ctrl-c message, in file-i/o protocol
38690 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
38691 reply packet (@pxref{The F Reply Packet}),
38692 the target should behave as if it had
38693 gotten a break message. The meaning for the target is ``system call
38694 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
38695 (as with a break message) and return to @value{GDBN} with a @code{T02}
38698 It's important for the target to know in which
38699 state the system call was interrupted. There are two possible cases:
38703 The system call hasn't been performed on the host yet.
38706 The system call on the host has been finished.
38710 These two states can be distinguished by the target by the value of the
38711 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
38712 call hasn't been performed. This is equivalent to the @code{EINTR} handling
38713 on POSIX systems. In any other case, the target may presume that the
38714 system call has been finished --- successfully or not --- and should behave
38715 as if the break message arrived right after the system call.
38717 @value{GDBN} must behave reliably. If the system call has not been called
38718 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
38719 @code{errno} in the packet. If the system call on the host has been finished
38720 before the user requests a break, the full action must be finished by
38721 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
38722 The @code{F} packet may only be sent when either nothing has happened
38723 or the full action has been completed.
38726 @subsection Console I/O
38727 @cindex console i/o as part of file-i/o
38729 By default and if not explicitly closed by the target system, the file
38730 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
38731 on the @value{GDBN} console is handled as any other file output operation
38732 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
38733 by @value{GDBN} so that after the target read request from file descriptor
38734 0 all following typing is buffered until either one of the following
38739 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
38741 system call is treated as finished.
38744 The user presses @key{RET}. This is treated as end of input with a trailing
38748 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
38749 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
38753 If the user has typed more characters than fit in the buffer given to
38754 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
38755 either another @code{read(0, @dots{})} is requested by the target, or debugging
38756 is stopped at the user's request.
38759 @node List of Supported Calls
38760 @subsection List of Supported Calls
38761 @cindex list of supported file-i/o calls
38778 @unnumberedsubsubsec open
38779 @cindex open, file-i/o system call
38784 int open(const char *pathname, int flags);
38785 int open(const char *pathname, int flags, mode_t mode);
38789 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
38792 @var{flags} is the bitwise @code{OR} of the following values:
38796 If the file does not exist it will be created. The host
38797 rules apply as far as file ownership and time stamps
38801 When used with @code{O_CREAT}, if the file already exists it is
38802 an error and open() fails.
38805 If the file already exists and the open mode allows
38806 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
38807 truncated to zero length.
38810 The file is opened in append mode.
38813 The file is opened for reading only.
38816 The file is opened for writing only.
38819 The file is opened for reading and writing.
38823 Other bits are silently ignored.
38827 @var{mode} is the bitwise @code{OR} of the following values:
38831 User has read permission.
38834 User has write permission.
38837 Group has read permission.
38840 Group has write permission.
38843 Others have read permission.
38846 Others have write permission.
38850 Other bits are silently ignored.
38853 @item Return value:
38854 @code{open} returns the new file descriptor or -1 if an error
38861 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
38864 @var{pathname} refers to a directory.
38867 The requested access is not allowed.
38870 @var{pathname} was too long.
38873 A directory component in @var{pathname} does not exist.
38876 @var{pathname} refers to a device, pipe, named pipe or socket.
38879 @var{pathname} refers to a file on a read-only filesystem and
38880 write access was requested.
38883 @var{pathname} is an invalid pointer value.
38886 No space on device to create the file.
38889 The process already has the maximum number of files open.
38892 The limit on the total number of files open on the system
38896 The call was interrupted by the user.
38902 @unnumberedsubsubsec close
38903 @cindex close, file-i/o system call
38912 @samp{Fclose,@var{fd}}
38914 @item Return value:
38915 @code{close} returns zero on success, or -1 if an error occurred.
38921 @var{fd} isn't a valid open file descriptor.
38924 The call was interrupted by the user.
38930 @unnumberedsubsubsec read
38931 @cindex read, file-i/o system call
38936 int read(int fd, void *buf, unsigned int count);
38940 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
38942 @item Return value:
38943 On success, the number of bytes read is returned.
38944 Zero indicates end of file. If count is zero, read
38945 returns zero as well. On error, -1 is returned.
38951 @var{fd} is not a valid file descriptor or is not open for
38955 @var{bufptr} is an invalid pointer value.
38958 The call was interrupted by the user.
38964 @unnumberedsubsubsec write
38965 @cindex write, file-i/o system call
38970 int write(int fd, const void *buf, unsigned int count);
38974 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
38976 @item Return value:
38977 On success, the number of bytes written are returned.
38978 Zero indicates nothing was written. On error, -1
38985 @var{fd} is not a valid file descriptor or is not open for
38989 @var{bufptr} is an invalid pointer value.
38992 An attempt was made to write a file that exceeds the
38993 host-specific maximum file size allowed.
38996 No space on device to write the data.
38999 The call was interrupted by the user.
39005 @unnumberedsubsubsec lseek
39006 @cindex lseek, file-i/o system call
39011 long lseek (int fd, long offset, int flag);
39015 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
39017 @var{flag} is one of:
39021 The offset is set to @var{offset} bytes.
39024 The offset is set to its current location plus @var{offset}
39028 The offset is set to the size of the file plus @var{offset}
39032 @item Return value:
39033 On success, the resulting unsigned offset in bytes from
39034 the beginning of the file is returned. Otherwise, a
39035 value of -1 is returned.
39041 @var{fd} is not a valid open file descriptor.
39044 @var{fd} is associated with the @value{GDBN} console.
39047 @var{flag} is not a proper value.
39050 The call was interrupted by the user.
39056 @unnumberedsubsubsec rename
39057 @cindex rename, file-i/o system call
39062 int rename(const char *oldpath, const char *newpath);
39066 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
39068 @item Return value:
39069 On success, zero is returned. On error, -1 is returned.
39075 @var{newpath} is an existing directory, but @var{oldpath} is not a
39079 @var{newpath} is a non-empty directory.
39082 @var{oldpath} or @var{newpath} is a directory that is in use by some
39086 An attempt was made to make a directory a subdirectory
39090 A component used as a directory in @var{oldpath} or new
39091 path is not a directory. Or @var{oldpath} is a directory
39092 and @var{newpath} exists but is not a directory.
39095 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
39098 No access to the file or the path of the file.
39102 @var{oldpath} or @var{newpath} was too long.
39105 A directory component in @var{oldpath} or @var{newpath} does not exist.
39108 The file is on a read-only filesystem.
39111 The device containing the file has no room for the new
39115 The call was interrupted by the user.
39121 @unnumberedsubsubsec unlink
39122 @cindex unlink, file-i/o system call
39127 int unlink(const char *pathname);
39131 @samp{Funlink,@var{pathnameptr}/@var{len}}
39133 @item Return value:
39134 On success, zero is returned. On error, -1 is returned.
39140 No access to the file or the path of the file.
39143 The system does not allow unlinking of directories.
39146 The file @var{pathname} cannot be unlinked because it's
39147 being used by another process.
39150 @var{pathnameptr} is an invalid pointer value.
39153 @var{pathname} was too long.
39156 A directory component in @var{pathname} does not exist.
39159 A component of the path is not a directory.
39162 The file is on a read-only filesystem.
39165 The call was interrupted by the user.
39171 @unnumberedsubsubsec stat/fstat
39172 @cindex fstat, file-i/o system call
39173 @cindex stat, file-i/o system call
39178 int stat(const char *pathname, struct stat *buf);
39179 int fstat(int fd, struct stat *buf);
39183 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
39184 @samp{Ffstat,@var{fd},@var{bufptr}}
39186 @item Return value:
39187 On success, zero is returned. On error, -1 is returned.
39193 @var{fd} is not a valid open file.
39196 A directory component in @var{pathname} does not exist or the
39197 path is an empty string.
39200 A component of the path is not a directory.
39203 @var{pathnameptr} is an invalid pointer value.
39206 No access to the file or the path of the file.
39209 @var{pathname} was too long.
39212 The call was interrupted by the user.
39218 @unnumberedsubsubsec gettimeofday
39219 @cindex gettimeofday, file-i/o system call
39224 int gettimeofday(struct timeval *tv, void *tz);
39228 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
39230 @item Return value:
39231 On success, 0 is returned, -1 otherwise.
39237 @var{tz} is a non-NULL pointer.
39240 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
39246 @unnumberedsubsubsec isatty
39247 @cindex isatty, file-i/o system call
39252 int isatty(int fd);
39256 @samp{Fisatty,@var{fd}}
39258 @item Return value:
39259 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
39265 The call was interrupted by the user.
39270 Note that the @code{isatty} call is treated as a special case: it returns
39271 1 to the target if the file descriptor is attached
39272 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
39273 would require implementing @code{ioctl} and would be more complex than
39278 @unnumberedsubsubsec system
39279 @cindex system, file-i/o system call
39284 int system(const char *command);
39288 @samp{Fsystem,@var{commandptr}/@var{len}}
39290 @item Return value:
39291 If @var{len} is zero, the return value indicates whether a shell is
39292 available. A zero return value indicates a shell is not available.
39293 For non-zero @var{len}, the value returned is -1 on error and the
39294 return status of the command otherwise. Only the exit status of the
39295 command is returned, which is extracted from the host's @code{system}
39296 return value by calling @code{WEXITSTATUS(retval)}. In case
39297 @file{/bin/sh} could not be executed, 127 is returned.
39303 The call was interrupted by the user.
39308 @value{GDBN} takes over the full task of calling the necessary host calls
39309 to perform the @code{system} call. The return value of @code{system} on
39310 the host is simplified before it's returned
39311 to the target. Any termination signal information from the child process
39312 is discarded, and the return value consists
39313 entirely of the exit status of the called command.
39315 Due to security concerns, the @code{system} call is by default refused
39316 by @value{GDBN}. The user has to allow this call explicitly with the
39317 @code{set remote system-call-allowed 1} command.
39320 @item set remote system-call-allowed
39321 @kindex set remote system-call-allowed
39322 Control whether to allow the @code{system} calls in the File I/O
39323 protocol for the remote target. The default is zero (disabled).
39325 @item show remote system-call-allowed
39326 @kindex show remote system-call-allowed
39327 Show whether the @code{system} calls are allowed in the File I/O
39331 @node Protocol-specific Representation of Datatypes
39332 @subsection Protocol-specific Representation of Datatypes
39333 @cindex protocol-specific representation of datatypes, in file-i/o protocol
39336 * Integral Datatypes::
39338 * Memory Transfer::
39343 @node Integral Datatypes
39344 @unnumberedsubsubsec Integral Datatypes
39345 @cindex integral datatypes, in file-i/o protocol
39347 The integral datatypes used in the system calls are @code{int},
39348 @code{unsigned int}, @code{long}, @code{unsigned long},
39349 @code{mode_t}, and @code{time_t}.
39351 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
39352 implemented as 32 bit values in this protocol.
39354 @code{long} and @code{unsigned long} are implemented as 64 bit types.
39356 @xref{Limits}, for corresponding MIN and MAX values (similar to those
39357 in @file{limits.h}) to allow range checking on host and target.
39359 @code{time_t} datatypes are defined as seconds since the Epoch.
39361 All integral datatypes transferred as part of a memory read or write of a
39362 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
39365 @node Pointer Values
39366 @unnumberedsubsubsec Pointer Values
39367 @cindex pointer values, in file-i/o protocol
39369 Pointers to target data are transmitted as they are. An exception
39370 is made for pointers to buffers for which the length isn't
39371 transmitted as part of the function call, namely strings. Strings
39372 are transmitted as a pointer/length pair, both as hex values, e.g.@:
39379 which is a pointer to data of length 18 bytes at position 0x1aaf.
39380 The length is defined as the full string length in bytes, including
39381 the trailing null byte. For example, the string @code{"hello world"}
39382 at address 0x123456 is transmitted as
39388 @node Memory Transfer
39389 @unnumberedsubsubsec Memory Transfer
39390 @cindex memory transfer, in file-i/o protocol
39392 Structured data which is transferred using a memory read or write (for
39393 example, a @code{struct stat}) is expected to be in a protocol-specific format
39394 with all scalar multibyte datatypes being big endian. Translation to
39395 this representation needs to be done both by the target before the @code{F}
39396 packet is sent, and by @value{GDBN} before
39397 it transfers memory to the target. Transferred pointers to structured
39398 data should point to the already-coerced data at any time.
39402 @unnumberedsubsubsec struct stat
39403 @cindex struct stat, in file-i/o protocol
39405 The buffer of type @code{struct stat} used by the target and @value{GDBN}
39406 is defined as follows:
39410 unsigned int st_dev; /* device */
39411 unsigned int st_ino; /* inode */
39412 mode_t st_mode; /* protection */
39413 unsigned int st_nlink; /* number of hard links */
39414 unsigned int st_uid; /* user ID of owner */
39415 unsigned int st_gid; /* group ID of owner */
39416 unsigned int st_rdev; /* device type (if inode device) */
39417 unsigned long st_size; /* total size, in bytes */
39418 unsigned long st_blksize; /* blocksize for filesystem I/O */
39419 unsigned long st_blocks; /* number of blocks allocated */
39420 time_t st_atime; /* time of last access */
39421 time_t st_mtime; /* time of last modification */
39422 time_t st_ctime; /* time of last change */
39426 The integral datatypes conform to the definitions given in the
39427 appropriate section (see @ref{Integral Datatypes}, for details) so this
39428 structure is of size 64 bytes.
39430 The values of several fields have a restricted meaning and/or
39436 A value of 0 represents a file, 1 the console.
39439 No valid meaning for the target. Transmitted unchanged.
39442 Valid mode bits are described in @ref{Constants}. Any other
39443 bits have currently no meaning for the target.
39448 No valid meaning for the target. Transmitted unchanged.
39453 These values have a host and file system dependent
39454 accuracy. Especially on Windows hosts, the file system may not
39455 support exact timing values.
39458 The target gets a @code{struct stat} of the above representation and is
39459 responsible for coercing it to the target representation before
39462 Note that due to size differences between the host, target, and protocol
39463 representations of @code{struct stat} members, these members could eventually
39464 get truncated on the target.
39466 @node struct timeval
39467 @unnumberedsubsubsec struct timeval
39468 @cindex struct timeval, in file-i/o protocol
39470 The buffer of type @code{struct timeval} used by the File-I/O protocol
39471 is defined as follows:
39475 time_t tv_sec; /* second */
39476 long tv_usec; /* microsecond */
39480 The integral datatypes conform to the definitions given in the
39481 appropriate section (see @ref{Integral Datatypes}, for details) so this
39482 structure is of size 8 bytes.
39485 @subsection Constants
39486 @cindex constants, in file-i/o protocol
39488 The following values are used for the constants inside of the
39489 protocol. @value{GDBN} and target are responsible for translating these
39490 values before and after the call as needed.
39501 @unnumberedsubsubsec Open Flags
39502 @cindex open flags, in file-i/o protocol
39504 All values are given in hexadecimal representation.
39516 @node mode_t Values
39517 @unnumberedsubsubsec mode_t Values
39518 @cindex mode_t values, in file-i/o protocol
39520 All values are given in octal representation.
39537 @unnumberedsubsubsec Errno Values
39538 @cindex errno values, in file-i/o protocol
39540 All values are given in decimal representation.
39565 @code{EUNKNOWN} is used as a fallback error value if a host system returns
39566 any error value not in the list of supported error numbers.
39569 @unnumberedsubsubsec Lseek Flags
39570 @cindex lseek flags, in file-i/o protocol
39579 @unnumberedsubsubsec Limits
39580 @cindex limits, in file-i/o protocol
39582 All values are given in decimal representation.
39585 INT_MIN -2147483648
39587 UINT_MAX 4294967295
39588 LONG_MIN -9223372036854775808
39589 LONG_MAX 9223372036854775807
39590 ULONG_MAX 18446744073709551615
39593 @node File-I/O Examples
39594 @subsection File-I/O Examples
39595 @cindex file-i/o examples
39597 Example sequence of a write call, file descriptor 3, buffer is at target
39598 address 0x1234, 6 bytes should be written:
39601 <- @code{Fwrite,3,1234,6}
39602 @emph{request memory read from target}
39605 @emph{return "6 bytes written"}
39609 Example sequence of a read call, file descriptor 3, buffer is at target
39610 address 0x1234, 6 bytes should be read:
39613 <- @code{Fread,3,1234,6}
39614 @emph{request memory write to target}
39615 -> @code{X1234,6:XXXXXX}
39616 @emph{return "6 bytes read"}
39620 Example sequence of a read call, call fails on the host due to invalid
39621 file descriptor (@code{EBADF}):
39624 <- @code{Fread,3,1234,6}
39628 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
39632 <- @code{Fread,3,1234,6}
39637 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
39641 <- @code{Fread,3,1234,6}
39642 -> @code{X1234,6:XXXXXX}
39646 @node Library List Format
39647 @section Library List Format
39648 @cindex library list format, remote protocol
39650 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
39651 same process as your application to manage libraries. In this case,
39652 @value{GDBN} can use the loader's symbol table and normal memory
39653 operations to maintain a list of shared libraries. On other
39654 platforms, the operating system manages loaded libraries.
39655 @value{GDBN} can not retrieve the list of currently loaded libraries
39656 through memory operations, so it uses the @samp{qXfer:libraries:read}
39657 packet (@pxref{qXfer library list read}) instead. The remote stub
39658 queries the target's operating system and reports which libraries
39661 The @samp{qXfer:libraries:read} packet returns an XML document which
39662 lists loaded libraries and their offsets. Each library has an
39663 associated name and one or more segment or section base addresses,
39664 which report where the library was loaded in memory.
39666 For the common case of libraries that are fully linked binaries, the
39667 library should have a list of segments. If the target supports
39668 dynamic linking of a relocatable object file, its library XML element
39669 should instead include a list of allocated sections. The segment or
39670 section bases are start addresses, not relocation offsets; they do not
39671 depend on the library's link-time base addresses.
39673 @value{GDBN} must be linked with the Expat library to support XML
39674 library lists. @xref{Expat}.
39676 A simple memory map, with one loaded library relocated by a single
39677 offset, looks like this:
39681 <library name="/lib/libc.so.6">
39682 <segment address="0x10000000"/>
39687 Another simple memory map, with one loaded library with three
39688 allocated sections (.text, .data, .bss), looks like this:
39692 <library name="sharedlib.o">
39693 <section address="0x10000000"/>
39694 <section address="0x20000000"/>
39695 <section address="0x30000000"/>
39700 The format of a library list is described by this DTD:
39703 <!-- library-list: Root element with versioning -->
39704 <!ELEMENT library-list (library)*>
39705 <!ATTLIST library-list version CDATA #FIXED "1.0">
39706 <!ELEMENT library (segment*, section*)>
39707 <!ATTLIST library name CDATA #REQUIRED>
39708 <!ELEMENT segment EMPTY>
39709 <!ATTLIST segment address CDATA #REQUIRED>
39710 <!ELEMENT section EMPTY>
39711 <!ATTLIST section address CDATA #REQUIRED>
39714 In addition, segments and section descriptors cannot be mixed within a
39715 single library element, and you must supply at least one segment or
39716 section for each library.
39718 @node Library List Format for SVR4 Targets
39719 @section Library List Format for SVR4 Targets
39720 @cindex library list format, remote protocol
39722 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
39723 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
39724 shared libraries. Still a special library list provided by this packet is
39725 more efficient for the @value{GDBN} remote protocol.
39727 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
39728 loaded libraries and their SVR4 linker parameters. For each library on SVR4
39729 target, the following parameters are reported:
39733 @code{name}, the absolute file name from the @code{l_name} field of
39734 @code{struct link_map}.
39736 @code{lm} with address of @code{struct link_map} used for TLS
39737 (Thread Local Storage) access.
39739 @code{l_addr}, the displacement as read from the field @code{l_addr} of
39740 @code{struct link_map}. For prelinked libraries this is not an absolute
39741 memory address. It is a displacement of absolute memory address against
39742 address the file was prelinked to during the library load.
39744 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
39747 Additionally the single @code{main-lm} attribute specifies address of
39748 @code{struct link_map} used for the main executable. This parameter is used
39749 for TLS access and its presence is optional.
39751 @value{GDBN} must be linked with the Expat library to support XML
39752 SVR4 library lists. @xref{Expat}.
39754 A simple memory map, with two loaded libraries (which do not use prelink),
39758 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
39759 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
39761 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
39763 </library-list-svr>
39766 The format of an SVR4 library list is described by this DTD:
39769 <!-- library-list-svr4: Root element with versioning -->
39770 <!ELEMENT library-list-svr4 (library)*>
39771 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
39772 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
39773 <!ELEMENT library EMPTY>
39774 <!ATTLIST library name CDATA #REQUIRED>
39775 <!ATTLIST library lm CDATA #REQUIRED>
39776 <!ATTLIST library l_addr CDATA #REQUIRED>
39777 <!ATTLIST library l_ld CDATA #REQUIRED>
39780 @node Memory Map Format
39781 @section Memory Map Format
39782 @cindex memory map format
39784 To be able to write into flash memory, @value{GDBN} needs to obtain a
39785 memory map from the target. This section describes the format of the
39788 The memory map is obtained using the @samp{qXfer:memory-map:read}
39789 (@pxref{qXfer memory map read}) packet and is an XML document that
39790 lists memory regions.
39792 @value{GDBN} must be linked with the Expat library to support XML
39793 memory maps. @xref{Expat}.
39795 The top-level structure of the document is shown below:
39798 <?xml version="1.0"?>
39799 <!DOCTYPE memory-map
39800 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
39801 "http://sourceware.org/gdb/gdb-memory-map.dtd">
39807 Each region can be either:
39812 A region of RAM starting at @var{addr} and extending for @var{length}
39816 <memory type="ram" start="@var{addr}" length="@var{length}"/>
39821 A region of read-only memory:
39824 <memory type="rom" start="@var{addr}" length="@var{length}"/>
39829 A region of flash memory, with erasure blocks @var{blocksize}
39833 <memory type="flash" start="@var{addr}" length="@var{length}">
39834 <property name="blocksize">@var{blocksize}</property>
39840 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
39841 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
39842 packets to write to addresses in such ranges.
39844 The formal DTD for memory map format is given below:
39847 <!-- ................................................... -->
39848 <!-- Memory Map XML DTD ................................ -->
39849 <!-- File: memory-map.dtd .............................. -->
39850 <!-- .................................... .............. -->
39851 <!-- memory-map.dtd -->
39852 <!-- memory-map: Root element with versioning -->
39853 <!ELEMENT memory-map (memory | property)>
39854 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
39855 <!ELEMENT memory (property)>
39856 <!-- memory: Specifies a memory region,
39857 and its type, or device. -->
39858 <!ATTLIST memory type CDATA #REQUIRED
39859 start CDATA #REQUIRED
39860 length CDATA #REQUIRED
39861 device CDATA #IMPLIED>
39862 <!-- property: Generic attribute tag -->
39863 <!ELEMENT property (#PCDATA | property)*>
39864 <!ATTLIST property name CDATA #REQUIRED>
39867 @node Thread List Format
39868 @section Thread List Format
39869 @cindex thread list format
39871 To efficiently update the list of threads and their attributes,
39872 @value{GDBN} issues the @samp{qXfer:threads:read} packet
39873 (@pxref{qXfer threads read}) and obtains the XML document with
39874 the following structure:
39877 <?xml version="1.0"?>
39879 <thread id="id" core="0">
39880 ... description ...
39885 Each @samp{thread} element must have the @samp{id} attribute that
39886 identifies the thread (@pxref{thread-id syntax}). The
39887 @samp{core} attribute, if present, specifies which processor core
39888 the thread was last executing on. The content of the of @samp{thread}
39889 element is interpreted as human-readable auxilliary information.
39891 @node Traceframe Info Format
39892 @section Traceframe Info Format
39893 @cindex traceframe info format
39895 To be able to know which objects in the inferior can be examined when
39896 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
39897 memory ranges, registers and trace state variables that have been
39898 collected in a traceframe.
39900 This list is obtained using the @samp{qXfer:traceframe-info:read}
39901 (@pxref{qXfer traceframe info read}) packet and is an XML document.
39903 @value{GDBN} must be linked with the Expat library to support XML
39904 traceframe info discovery. @xref{Expat}.
39906 The top-level structure of the document is shown below:
39909 <?xml version="1.0"?>
39910 <!DOCTYPE traceframe-info
39911 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
39912 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
39918 Each traceframe block can be either:
39923 A region of collected memory starting at @var{addr} and extending for
39924 @var{length} bytes from there:
39927 <memory start="@var{addr}" length="@var{length}"/>
39931 A block indicating trace state variable numbered @var{number} has been
39935 <tvar id="@var{number}"/>
39940 The formal DTD for the traceframe info format is given below:
39943 <!ELEMENT traceframe-info (memory | tvar)* >
39944 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
39946 <!ELEMENT memory EMPTY>
39947 <!ATTLIST memory start CDATA #REQUIRED
39948 length CDATA #REQUIRED>
39950 <!ATTLIST tvar id CDATA #REQUIRED>
39953 @node Branch Trace Format
39954 @section Branch Trace Format
39955 @cindex branch trace format
39957 In order to display the branch trace of an inferior thread,
39958 @value{GDBN} needs to obtain the list of branches. This list is
39959 represented as list of sequential code blocks that are connected via
39960 branches. The code in each block has been executed sequentially.
39962 This list is obtained using the @samp{qXfer:btrace:read}
39963 (@pxref{qXfer btrace read}) packet and is an XML document.
39965 @value{GDBN} must be linked with the Expat library to support XML
39966 traceframe info discovery. @xref{Expat}.
39968 The top-level structure of the document is shown below:
39971 <?xml version="1.0"?>
39973 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
39974 "http://sourceware.org/gdb/gdb-btrace.dtd">
39983 A block of sequentially executed instructions starting at @var{begin}
39984 and ending at @var{end}:
39987 <block begin="@var{begin}" end="@var{end}"/>
39992 The formal DTD for the branch trace format is given below:
39995 <!ELEMENT btrace (block* | pt) >
39996 <!ATTLIST btrace version CDATA #FIXED "1.0">
39998 <!ELEMENT block EMPTY>
39999 <!ATTLIST block begin CDATA #REQUIRED
40000 end CDATA #REQUIRED>
40002 <!ELEMENT pt (pt-config?, raw?)>
40004 <!ELEMENT pt-config (cpu?)>
40006 <!ELEMENT cpu EMPTY>
40007 <!ATTLIST cpu vendor CDATA #REQUIRED
40008 family CDATA #REQUIRED
40009 model CDATA #REQUIRED
40010 stepping CDATA #REQUIRED>
40012 <!ELEMENT raw (#PCDATA)>
40015 @node Branch Trace Configuration Format
40016 @section Branch Trace Configuration Format
40017 @cindex branch trace configuration format
40019 For each inferior thread, @value{GDBN} can obtain the branch trace
40020 configuration using the @samp{qXfer:btrace-conf:read}
40021 (@pxref{qXfer btrace-conf read}) packet.
40023 The configuration describes the branch trace format and configuration
40024 settings for that format. The following information is described:
40028 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
40031 The size of the @acronym{BTS} ring buffer in bytes.
40034 This thread uses the @dfn{Intel(R) Processor Trace} (@acronym{Intel(R)
40038 The size of the @acronym{Intel(R) PT} ring buffer in bytes.
40042 @value{GDBN} must be linked with the Expat library to support XML
40043 branch trace configuration discovery. @xref{Expat}.
40045 The formal DTD for the branch trace configuration format is given below:
40048 <!ELEMENT btrace-conf (bts?, pt?)>
40049 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
40051 <!ELEMENT bts EMPTY>
40052 <!ATTLIST bts size CDATA #IMPLIED>
40054 <!ELEMENT pt EMPTY>
40055 <!ATTLIST pt size CDATA #IMPLIED>
40058 @include agentexpr.texi
40060 @node Target Descriptions
40061 @appendix Target Descriptions
40062 @cindex target descriptions
40064 One of the challenges of using @value{GDBN} to debug embedded systems
40065 is that there are so many minor variants of each processor
40066 architecture in use. It is common practice for vendors to start with
40067 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
40068 and then make changes to adapt it to a particular market niche. Some
40069 architectures have hundreds of variants, available from dozens of
40070 vendors. This leads to a number of problems:
40074 With so many different customized processors, it is difficult for
40075 the @value{GDBN} maintainers to keep up with the changes.
40077 Since individual variants may have short lifetimes or limited
40078 audiences, it may not be worthwhile to carry information about every
40079 variant in the @value{GDBN} source tree.
40081 When @value{GDBN} does support the architecture of the embedded system
40082 at hand, the task of finding the correct architecture name to give the
40083 @command{set architecture} command can be error-prone.
40086 To address these problems, the @value{GDBN} remote protocol allows a
40087 target system to not only identify itself to @value{GDBN}, but to
40088 actually describe its own features. This lets @value{GDBN} support
40089 processor variants it has never seen before --- to the extent that the
40090 descriptions are accurate, and that @value{GDBN} understands them.
40092 @value{GDBN} must be linked with the Expat library to support XML
40093 target descriptions. @xref{Expat}.
40096 * Retrieving Descriptions:: How descriptions are fetched from a target.
40097 * Target Description Format:: The contents of a target description.
40098 * Predefined Target Types:: Standard types available for target
40100 * Standard Target Features:: Features @value{GDBN} knows about.
40103 @node Retrieving Descriptions
40104 @section Retrieving Descriptions
40106 Target descriptions can be read from the target automatically, or
40107 specified by the user manually. The default behavior is to read the
40108 description from the target. @value{GDBN} retrieves it via the remote
40109 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
40110 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
40111 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
40112 XML document, of the form described in @ref{Target Description
40115 Alternatively, you can specify a file to read for the target description.
40116 If a file is set, the target will not be queried. The commands to
40117 specify a file are:
40120 @cindex set tdesc filename
40121 @item set tdesc filename @var{path}
40122 Read the target description from @var{path}.
40124 @cindex unset tdesc filename
40125 @item unset tdesc filename
40126 Do not read the XML target description from a file. @value{GDBN}
40127 will use the description supplied by the current target.
40129 @cindex show tdesc filename
40130 @item show tdesc filename
40131 Show the filename to read for a target description, if any.
40135 @node Target Description Format
40136 @section Target Description Format
40137 @cindex target descriptions, XML format
40139 A target description annex is an @uref{http://www.w3.org/XML/, XML}
40140 document which complies with the Document Type Definition provided in
40141 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
40142 means you can use generally available tools like @command{xmllint} to
40143 check that your feature descriptions are well-formed and valid.
40144 However, to help people unfamiliar with XML write descriptions for
40145 their targets, we also describe the grammar here.
40147 Target descriptions can identify the architecture of the remote target
40148 and (for some architectures) provide information about custom register
40149 sets. They can also identify the OS ABI of the remote target.
40150 @value{GDBN} can use this information to autoconfigure for your
40151 target, or to warn you if you connect to an unsupported target.
40153 Here is a simple target description:
40156 <target version="1.0">
40157 <architecture>i386:x86-64</architecture>
40162 This minimal description only says that the target uses
40163 the x86-64 architecture.
40165 A target description has the following overall form, with [ ] marking
40166 optional elements and @dots{} marking repeatable elements. The elements
40167 are explained further below.
40170 <?xml version="1.0"?>
40171 <!DOCTYPE target SYSTEM "gdb-target.dtd">
40172 <target version="1.0">
40173 @r{[}@var{architecture}@r{]}
40174 @r{[}@var{osabi}@r{]}
40175 @r{[}@var{compatible}@r{]}
40176 @r{[}@var{feature}@dots{}@r{]}
40181 The description is generally insensitive to whitespace and line
40182 breaks, under the usual common-sense rules. The XML version
40183 declaration and document type declaration can generally be omitted
40184 (@value{GDBN} does not require them), but specifying them may be
40185 useful for XML validation tools. The @samp{version} attribute for
40186 @samp{<target>} may also be omitted, but we recommend
40187 including it; if future versions of @value{GDBN} use an incompatible
40188 revision of @file{gdb-target.dtd}, they will detect and report
40189 the version mismatch.
40191 @subsection Inclusion
40192 @cindex target descriptions, inclusion
40195 @cindex <xi:include>
40198 It can sometimes be valuable to split a target description up into
40199 several different annexes, either for organizational purposes, or to
40200 share files between different possible target descriptions. You can
40201 divide a description into multiple files by replacing any element of
40202 the target description with an inclusion directive of the form:
40205 <xi:include href="@var{document}"/>
40209 When @value{GDBN} encounters an element of this form, it will retrieve
40210 the named XML @var{document}, and replace the inclusion directive with
40211 the contents of that document. If the current description was read
40212 using @samp{qXfer}, then so will be the included document;
40213 @var{document} will be interpreted as the name of an annex. If the
40214 current description was read from a file, @value{GDBN} will look for
40215 @var{document} as a file in the same directory where it found the
40216 original description.
40218 @subsection Architecture
40219 @cindex <architecture>
40221 An @samp{<architecture>} element has this form:
40224 <architecture>@var{arch}</architecture>
40227 @var{arch} is one of the architectures from the set accepted by
40228 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40231 @cindex @code{<osabi>}
40233 This optional field was introduced in @value{GDBN} version 7.0.
40234 Previous versions of @value{GDBN} ignore it.
40236 An @samp{<osabi>} element has this form:
40239 <osabi>@var{abi-name}</osabi>
40242 @var{abi-name} is an OS ABI name from the same selection accepted by
40243 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
40245 @subsection Compatible Architecture
40246 @cindex @code{<compatible>}
40248 This optional field was introduced in @value{GDBN} version 7.0.
40249 Previous versions of @value{GDBN} ignore it.
40251 A @samp{<compatible>} element has this form:
40254 <compatible>@var{arch}</compatible>
40257 @var{arch} is one of the architectures from the set accepted by
40258 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40260 A @samp{<compatible>} element is used to specify that the target
40261 is able to run binaries in some other than the main target architecture
40262 given by the @samp{<architecture>} element. For example, on the
40263 Cell Broadband Engine, the main architecture is @code{powerpc:common}
40264 or @code{powerpc:common64}, but the system is able to run binaries
40265 in the @code{spu} architecture as well. The way to describe this
40266 capability with @samp{<compatible>} is as follows:
40269 <architecture>powerpc:common</architecture>
40270 <compatible>spu</compatible>
40273 @subsection Features
40276 Each @samp{<feature>} describes some logical portion of the target
40277 system. Features are currently used to describe available CPU
40278 registers and the types of their contents. A @samp{<feature>} element
40282 <feature name="@var{name}">
40283 @r{[}@var{type}@dots{}@r{]}
40289 Each feature's name should be unique within the description. The name
40290 of a feature does not matter unless @value{GDBN} has some special
40291 knowledge of the contents of that feature; if it does, the feature
40292 should have its standard name. @xref{Standard Target Features}.
40296 Any register's value is a collection of bits which @value{GDBN} must
40297 interpret. The default interpretation is a two's complement integer,
40298 but other types can be requested by name in the register description.
40299 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
40300 Target Types}), and the description can define additional composite types.
40302 Each type element must have an @samp{id} attribute, which gives
40303 a unique (within the containing @samp{<feature>}) name to the type.
40304 Types must be defined before they are used.
40307 Some targets offer vector registers, which can be treated as arrays
40308 of scalar elements. These types are written as @samp{<vector>} elements,
40309 specifying the array element type, @var{type}, and the number of elements,
40313 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
40317 If a register's value is usefully viewed in multiple ways, define it
40318 with a union type containing the useful representations. The
40319 @samp{<union>} element contains one or more @samp{<field>} elements,
40320 each of which has a @var{name} and a @var{type}:
40323 <union id="@var{id}">
40324 <field name="@var{name}" type="@var{type}"/>
40330 If a register's value is composed from several separate values, define
40331 it with a structure type. There are two forms of the @samp{<struct>}
40332 element; a @samp{<struct>} element must either contain only bitfields
40333 or contain no bitfields. If the structure contains only bitfields,
40334 its total size in bytes must be specified, each bitfield must have an
40335 explicit start and end, and bitfields are automatically assigned an
40336 integer type. The field's @var{start} should be less than or
40337 equal to its @var{end}, and zero represents the least significant bit.
40340 <struct id="@var{id}" size="@var{size}">
40341 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
40346 If the structure contains no bitfields, then each field has an
40347 explicit type, and no implicit padding is added.
40350 <struct id="@var{id}">
40351 <field name="@var{name}" type="@var{type}"/>
40357 If a register's value is a series of single-bit flags, define it with
40358 a flags type. The @samp{<flags>} element has an explicit @var{size}
40359 and contains one or more @samp{<field>} elements. Each field has a
40360 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
40364 <flags id="@var{id}" size="@var{size}">
40365 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
40370 @subsection Registers
40373 Each register is represented as an element with this form:
40376 <reg name="@var{name}"
40377 bitsize="@var{size}"
40378 @r{[}regnum="@var{num}"@r{]}
40379 @r{[}save-restore="@var{save-restore}"@r{]}
40380 @r{[}type="@var{type}"@r{]}
40381 @r{[}group="@var{group}"@r{]}/>
40385 The components are as follows:
40390 The register's name; it must be unique within the target description.
40393 The register's size, in bits.
40396 The register's number. If omitted, a register's number is one greater
40397 than that of the previous register (either in the current feature or in
40398 a preceding feature); the first register in the target description
40399 defaults to zero. This register number is used to read or write
40400 the register; e.g.@: it is used in the remote @code{p} and @code{P}
40401 packets, and registers appear in the @code{g} and @code{G} packets
40402 in order of increasing register number.
40405 Whether the register should be preserved across inferior function
40406 calls; this must be either @code{yes} or @code{no}. The default is
40407 @code{yes}, which is appropriate for most registers except for
40408 some system control registers; this is not related to the target's
40412 The type of the register. It may be a predefined type, a type
40413 defined in the current feature, or one of the special types @code{int}
40414 and @code{float}. @code{int} is an integer type of the correct size
40415 for @var{bitsize}, and @code{float} is a floating point type (in the
40416 architecture's normal floating point format) of the correct size for
40417 @var{bitsize}. The default is @code{int}.
40420 The register group to which this register belongs. It must
40421 be either @code{general}, @code{float}, or @code{vector}. If no
40422 @var{group} is specified, @value{GDBN} will not display the register
40423 in @code{info registers}.
40427 @node Predefined Target Types
40428 @section Predefined Target Types
40429 @cindex target descriptions, predefined types
40431 Type definitions in the self-description can build up composite types
40432 from basic building blocks, but can not define fundamental types. Instead,
40433 standard identifiers are provided by @value{GDBN} for the fundamental
40434 types. The currently supported types are:
40443 Signed integer types holding the specified number of bits.
40450 Unsigned integer types holding the specified number of bits.
40454 Pointers to unspecified code and data. The program counter and
40455 any dedicated return address register may be marked as code
40456 pointers; printing a code pointer converts it into a symbolic
40457 address. The stack pointer and any dedicated address registers
40458 may be marked as data pointers.
40461 Single precision IEEE floating point.
40464 Double precision IEEE floating point.
40467 The 12-byte extended precision format used by ARM FPA registers.
40470 The 10-byte extended precision format used by x87 registers.
40473 32bit @sc{eflags} register used by x86.
40476 32bit @sc{mxcsr} register used by x86.
40480 @node Standard Target Features
40481 @section Standard Target Features
40482 @cindex target descriptions, standard features
40484 A target description must contain either no registers or all the
40485 target's registers. If the description contains no registers, then
40486 @value{GDBN} will assume a default register layout, selected based on
40487 the architecture. If the description contains any registers, the
40488 default layout will not be used; the standard registers must be
40489 described in the target description, in such a way that @value{GDBN}
40490 can recognize them.
40492 This is accomplished by giving specific names to feature elements
40493 which contain standard registers. @value{GDBN} will look for features
40494 with those names and verify that they contain the expected registers;
40495 if any known feature is missing required registers, or if any required
40496 feature is missing, @value{GDBN} will reject the target
40497 description. You can add additional registers to any of the
40498 standard features --- @value{GDBN} will display them just as if
40499 they were added to an unrecognized feature.
40501 This section lists the known features and their expected contents.
40502 Sample XML documents for these features are included in the
40503 @value{GDBN} source tree, in the directory @file{gdb/features}.
40505 Names recognized by @value{GDBN} should include the name of the
40506 company or organization which selected the name, and the overall
40507 architecture to which the feature applies; so e.g.@: the feature
40508 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
40510 The names of registers are not case sensitive for the purpose
40511 of recognizing standard features, but @value{GDBN} will only display
40512 registers using the capitalization used in the description.
40515 * AArch64 Features::
40518 * MicroBlaze Features::
40521 * Nios II Features::
40522 * PowerPC Features::
40523 * S/390 and System z Features::
40528 @node AArch64 Features
40529 @subsection AArch64 Features
40530 @cindex target descriptions, AArch64 features
40532 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
40533 targets. It should contain registers @samp{x0} through @samp{x30},
40534 @samp{sp}, @samp{pc}, and @samp{cpsr}.
40536 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
40537 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
40541 @subsection ARM Features
40542 @cindex target descriptions, ARM features
40544 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
40546 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
40547 @samp{lr}, @samp{pc}, and @samp{cpsr}.
40549 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
40550 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
40551 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
40554 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
40555 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
40557 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
40558 it should contain at least registers @samp{wR0} through @samp{wR15} and
40559 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
40560 @samp{wCSSF}, and @samp{wCASF} registers are optional.
40562 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
40563 should contain at least registers @samp{d0} through @samp{d15}. If
40564 they are present, @samp{d16} through @samp{d31} should also be included.
40565 @value{GDBN} will synthesize the single-precision registers from
40566 halves of the double-precision registers.
40568 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
40569 need to contain registers; it instructs @value{GDBN} to display the
40570 VFP double-precision registers as vectors and to synthesize the
40571 quad-precision registers from pairs of double-precision registers.
40572 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
40573 be present and include 32 double-precision registers.
40575 @node i386 Features
40576 @subsection i386 Features
40577 @cindex target descriptions, i386 features
40579 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
40580 targets. It should describe the following registers:
40584 @samp{eax} through @samp{edi} plus @samp{eip} for i386
40586 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
40588 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
40589 @samp{fs}, @samp{gs}
40591 @samp{st0} through @samp{st7}
40593 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
40594 @samp{foseg}, @samp{fooff} and @samp{fop}
40597 The register sets may be different, depending on the target.
40599 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
40600 describe registers:
40604 @samp{xmm0} through @samp{xmm7} for i386
40606 @samp{xmm0} through @samp{xmm15} for amd64
40611 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
40612 @samp{org.gnu.gdb.i386.sse} feature. It should
40613 describe the upper 128 bits of @sc{ymm} registers:
40617 @samp{ymm0h} through @samp{ymm7h} for i386
40619 @samp{ymm0h} through @samp{ymm15h} for amd64
40622 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel(R)
40623 Memory Protection Extension (MPX). It should describe the following registers:
40627 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
40629 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
40632 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
40633 describe a single register, @samp{orig_eax}.
40635 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
40636 @samp{org.gnu.gdb.i386.avx} feature. It should
40637 describe additional @sc{xmm} registers:
40641 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
40644 It should describe the upper 128 bits of additional @sc{ymm} registers:
40648 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
40652 describe the upper 256 bits of @sc{zmm} registers:
40656 @samp{zmm0h} through @samp{zmm7h} for i386.
40658 @samp{zmm0h} through @samp{zmm15h} for amd64.
40662 describe the additional @sc{zmm} registers:
40666 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
40669 @node MicroBlaze Features
40670 @subsection MicroBlaze Features
40671 @cindex target descriptions, MicroBlaze features
40673 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
40674 targets. It should contain registers @samp{r0} through @samp{r31},
40675 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
40676 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
40677 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
40679 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
40680 If present, it should contain registers @samp{rshr} and @samp{rslr}
40682 @node MIPS Features
40683 @subsection @acronym{MIPS} Features
40684 @cindex target descriptions, @acronym{MIPS} features
40686 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
40687 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
40688 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
40691 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
40692 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
40693 registers. They may be 32-bit or 64-bit depending on the target.
40695 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
40696 it may be optional in a future version of @value{GDBN}. It should
40697 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
40698 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
40700 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
40701 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
40702 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
40703 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
40705 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
40706 contain a single register, @samp{restart}, which is used by the
40707 Linux kernel to control restartable syscalls.
40709 @node M68K Features
40710 @subsection M68K Features
40711 @cindex target descriptions, M68K features
40714 @item @samp{org.gnu.gdb.m68k.core}
40715 @itemx @samp{org.gnu.gdb.coldfire.core}
40716 @itemx @samp{org.gnu.gdb.fido.core}
40717 One of those features must be always present.
40718 The feature that is present determines which flavor of m68k is
40719 used. The feature that is present should contain registers
40720 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
40721 @samp{sp}, @samp{ps} and @samp{pc}.
40723 @item @samp{org.gnu.gdb.coldfire.fp}
40724 This feature is optional. If present, it should contain registers
40725 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
40729 @node Nios II Features
40730 @subsection Nios II Features
40731 @cindex target descriptions, Nios II features
40733 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
40734 targets. It should contain the 32 core registers (@samp{zero},
40735 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
40736 @samp{pc}, and the 16 control registers (@samp{status} through
40739 @node PowerPC Features
40740 @subsection PowerPC Features
40741 @cindex target descriptions, PowerPC features
40743 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
40744 targets. It should contain registers @samp{r0} through @samp{r31},
40745 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
40746 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
40748 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
40749 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
40751 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
40752 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
40755 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
40756 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
40757 will combine these registers with the floating point registers
40758 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
40759 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
40760 through @samp{vs63}, the set of vector registers for POWER7.
40762 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
40763 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
40764 @samp{spefscr}. SPE targets should provide 32-bit registers in
40765 @samp{org.gnu.gdb.power.core} and provide the upper halves in
40766 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
40767 these to present registers @samp{ev0} through @samp{ev31} to the
40770 @node S/390 and System z Features
40771 @subsection S/390 and System z Features
40772 @cindex target descriptions, S/390 features
40773 @cindex target descriptions, System z features
40775 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
40776 System z targets. It should contain the PSW and the 16 general
40777 registers. In particular, System z targets should provide the 64-bit
40778 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
40779 S/390 targets should provide the 32-bit versions of these registers.
40780 A System z target that runs in 31-bit addressing mode should provide
40781 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
40782 register's upper halves @samp{r0h} through @samp{r15h}, and their
40783 lower halves @samp{r0l} through @samp{r15l}.
40785 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
40786 contain the 64-bit registers @samp{f0} through @samp{f15}, and
40789 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
40790 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
40792 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
40793 contain the register @samp{orig_r2}, which is 64-bit wide on System z
40794 targets and 32-bit otherwise. In addition, the feature may contain
40795 the @samp{last_break} register, whose width depends on the addressing
40796 mode, as well as the @samp{system_call} register, which is always
40799 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
40800 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
40801 @samp{atia}, and @samp{tr0} through @samp{tr15}.
40803 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
40804 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
40805 combined by @value{GDBN} with the floating point registers @samp{f0}
40806 through @samp{f15} to present the 128-bit wide vector registers
40807 @samp{v0} through @samp{v15}. In addition, this feature should
40808 contain the 128-bit wide vector registers @samp{v16} through
40811 @node TIC6x Features
40812 @subsection TMS320C6x Features
40813 @cindex target descriptions, TIC6x features
40814 @cindex target descriptions, TMS320C6x features
40815 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
40816 targets. It should contain registers @samp{A0} through @samp{A15},
40817 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
40819 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
40820 contain registers @samp{A16} through @samp{A31} and @samp{B16}
40821 through @samp{B31}.
40823 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
40824 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
40826 @node Operating System Information
40827 @appendix Operating System Information
40828 @cindex operating system information
40834 Users of @value{GDBN} often wish to obtain information about the state of
40835 the operating system running on the target---for example the list of
40836 processes, or the list of open files. This section describes the
40837 mechanism that makes it possible. This mechanism is similar to the
40838 target features mechanism (@pxref{Target Descriptions}), but focuses
40839 on a different aspect of target.
40841 Operating system information is retrived from the target via the
40842 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
40843 read}). The object name in the request should be @samp{osdata}, and
40844 the @var{annex} identifies the data to be fetched.
40847 @appendixsection Process list
40848 @cindex operating system information, process list
40850 When requesting the process list, the @var{annex} field in the
40851 @samp{qXfer} request should be @samp{processes}. The returned data is
40852 an XML document. The formal syntax of this document is defined in
40853 @file{gdb/features/osdata.dtd}.
40855 An example document is:
40858 <?xml version="1.0"?>
40859 <!DOCTYPE target SYSTEM "osdata.dtd">
40860 <osdata type="processes">
40862 <column name="pid">1</column>
40863 <column name="user">root</column>
40864 <column name="command">/sbin/init</column>
40865 <column name="cores">1,2,3</column>
40870 Each item should include a column whose name is @samp{pid}. The value
40871 of that column should identify the process on the target. The
40872 @samp{user} and @samp{command} columns are optional, and will be
40873 displayed by @value{GDBN}. The @samp{cores} column, if present,
40874 should contain a comma-separated list of cores that this process
40875 is running on. Target may provide additional columns,
40876 which @value{GDBN} currently ignores.
40878 @node Trace File Format
40879 @appendix Trace File Format
40880 @cindex trace file format
40882 The trace file comes in three parts: a header, a textual description
40883 section, and a trace frame section with binary data.
40885 The header has the form @code{\x7fTRACE0\n}. The first byte is
40886 @code{0x7f} so as to indicate that the file contains binary data,
40887 while the @code{0} is a version number that may have different values
40890 The description section consists of multiple lines of @sc{ascii} text
40891 separated by newline characters (@code{0xa}). The lines may include a
40892 variety of optional descriptive or context-setting information, such
40893 as tracepoint definitions or register set size. @value{GDBN} will
40894 ignore any line that it does not recognize. An empty line marks the end
40897 @c FIXME add some specific types of data
40899 The trace frame section consists of a number of consecutive frames.
40900 Each frame begins with a two-byte tracepoint number, followed by a
40901 four-byte size giving the amount of data in the frame. The data in
40902 the frame consists of a number of blocks, each introduced by a
40903 character indicating its type (at least register, memory, and trace
40904 state variable). The data in this section is raw binary, not a
40905 hexadecimal or other encoding; its endianness matches the target's
40908 @c FIXME bi-arch may require endianness/arch info in description section
40911 @item R @var{bytes}
40912 Register block. The number and ordering of bytes matches that of a
40913 @code{g} packet in the remote protocol. Note that these are the
40914 actual bytes, in target order and @value{GDBN} register order, not a
40915 hexadecimal encoding.
40917 @item M @var{address} @var{length} @var{bytes}...
40918 Memory block. This is a contiguous block of memory, at the 8-byte
40919 address @var{address}, with a 2-byte length @var{length}, followed by
40920 @var{length} bytes.
40922 @item V @var{number} @var{value}
40923 Trace state variable block. This records the 8-byte signed value
40924 @var{value} of trace state variable numbered @var{number}.
40928 Future enhancements of the trace file format may include additional types
40931 @node Index Section Format
40932 @appendix @code{.gdb_index} section format
40933 @cindex .gdb_index section format
40934 @cindex index section format
40936 This section documents the index section that is created by @code{save
40937 gdb-index} (@pxref{Index Files}). The index section is
40938 DWARF-specific; some knowledge of DWARF is assumed in this
40941 The mapped index file format is designed to be directly
40942 @code{mmap}able on any architecture. In most cases, a datum is
40943 represented using a little-endian 32-bit integer value, called an
40944 @code{offset_type}. Big endian machines must byte-swap the values
40945 before using them. Exceptions to this rule are noted. The data is
40946 laid out such that alignment is always respected.
40948 A mapped index consists of several areas, laid out in order.
40952 The file header. This is a sequence of values, of @code{offset_type}
40953 unless otherwise noted:
40957 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
40958 Version 4 uses a different hashing function from versions 5 and 6.
40959 Version 6 includes symbols for inlined functions, whereas versions 4
40960 and 5 do not. Version 7 adds attributes to the CU indices in the
40961 symbol table. Version 8 specifies that symbols from DWARF type units
40962 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
40963 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
40965 @value{GDBN} will only read version 4, 5, or 6 indices
40966 by specifying @code{set use-deprecated-index-sections on}.
40967 GDB has a workaround for potentially broken version 7 indices so it is
40968 currently not flagged as deprecated.
40971 The offset, from the start of the file, of the CU list.
40974 The offset, from the start of the file, of the types CU list. Note
40975 that this area can be empty, in which case this offset will be equal
40976 to the next offset.
40979 The offset, from the start of the file, of the address area.
40982 The offset, from the start of the file, of the symbol table.
40985 The offset, from the start of the file, of the constant pool.
40989 The CU list. This is a sequence of pairs of 64-bit little-endian
40990 values, sorted by the CU offset. The first element in each pair is
40991 the offset of a CU in the @code{.debug_info} section. The second
40992 element in each pair is the length of that CU. References to a CU
40993 elsewhere in the map are done using a CU index, which is just the
40994 0-based index into this table. Note that if there are type CUs, then
40995 conceptually CUs and type CUs form a single list for the purposes of
40999 The types CU list. This is a sequence of triplets of 64-bit
41000 little-endian values. In a triplet, the first value is the CU offset,
41001 the second value is the type offset in the CU, and the third value is
41002 the type signature. The types CU list is not sorted.
41005 The address area. The address area consists of a sequence of address
41006 entries. Each address entry has three elements:
41010 The low address. This is a 64-bit little-endian value.
41013 The high address. This is a 64-bit little-endian value. Like
41014 @code{DW_AT_high_pc}, the value is one byte beyond the end.
41017 The CU index. This is an @code{offset_type} value.
41021 The symbol table. This is an open-addressed hash table. The size of
41022 the hash table is always a power of 2.
41024 Each slot in the hash table consists of a pair of @code{offset_type}
41025 values. The first value is the offset of the symbol's name in the
41026 constant pool. The second value is the offset of the CU vector in the
41029 If both values are 0, then this slot in the hash table is empty. This
41030 is ok because while 0 is a valid constant pool index, it cannot be a
41031 valid index for both a string and a CU vector.
41033 The hash value for a table entry is computed by applying an
41034 iterative hash function to the symbol's name. Starting with an
41035 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
41036 the string is incorporated into the hash using the formula depending on the
41041 The formula is @code{r = r * 67 + c - 113}.
41043 @item Versions 5 to 7
41044 The formula is @code{r = r * 67 + tolower (c) - 113}.
41047 The terminating @samp{\0} is not incorporated into the hash.
41049 The step size used in the hash table is computed via
41050 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
41051 value, and @samp{size} is the size of the hash table. The step size
41052 is used to find the next candidate slot when handling a hash
41055 The names of C@t{++} symbols in the hash table are canonicalized. We
41056 don't currently have a simple description of the canonicalization
41057 algorithm; if you intend to create new index sections, you must read
41061 The constant pool. This is simply a bunch of bytes. It is organized
41062 so that alignment is correct: CU vectors are stored first, followed by
41065 A CU vector in the constant pool is a sequence of @code{offset_type}
41066 values. The first value is the number of CU indices in the vector.
41067 Each subsequent value is the index and symbol attributes of a CU in
41068 the CU list. This element in the hash table is used to indicate which
41069 CUs define the symbol and how the symbol is used.
41070 See below for the format of each CU index+attributes entry.
41072 A string in the constant pool is zero-terminated.
41075 Attributes were added to CU index values in @code{.gdb_index} version 7.
41076 If a symbol has multiple uses within a CU then there is one
41077 CU index+attributes value for each use.
41079 The format of each CU index+attributes entry is as follows
41085 This is the index of the CU in the CU list.
41087 These bits are reserved for future purposes and must be zero.
41089 The kind of the symbol in the CU.
41093 This value is reserved and should not be used.
41094 By reserving zero the full @code{offset_type} value is backwards compatible
41095 with previous versions of the index.
41097 The symbol is a type.
41099 The symbol is a variable or an enum value.
41101 The symbol is a function.
41103 Any other kind of symbol.
41105 These values are reserved.
41109 This bit is zero if the value is global and one if it is static.
41111 The determination of whether a symbol is global or static is complicated.
41112 The authorative reference is the file @file{dwarf2read.c} in
41113 @value{GDBN} sources.
41117 This pseudo-code describes the computation of a symbol's kind and
41118 global/static attributes in the index.
41121 is_external = get_attribute (die, DW_AT_external);
41122 language = get_attribute (cu_die, DW_AT_language);
41125 case DW_TAG_typedef:
41126 case DW_TAG_base_type:
41127 case DW_TAG_subrange_type:
41131 case DW_TAG_enumerator:
41133 is_static = (language != CPLUS && language != JAVA);
41135 case DW_TAG_subprogram:
41137 is_static = ! (is_external || language == ADA);
41139 case DW_TAG_constant:
41141 is_static = ! is_external;
41143 case DW_TAG_variable:
41145 is_static = ! is_external;
41147 case DW_TAG_namespace:
41151 case DW_TAG_class_type:
41152 case DW_TAG_interface_type:
41153 case DW_TAG_structure_type:
41154 case DW_TAG_union_type:
41155 case DW_TAG_enumeration_type:
41157 is_static = (language != CPLUS && language != JAVA);
41165 @appendix Manual pages
41169 * gdb man:: The GNU Debugger man page
41170 * gdbserver man:: Remote Server for the GNU Debugger man page
41171 * gcore man:: Generate a core file of a running program
41172 * gdbinit man:: gdbinit scripts
41178 @c man title gdb The GNU Debugger
41180 @c man begin SYNOPSIS gdb
41181 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
41182 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
41183 [@option{-b}@w{ }@var{bps}]
41184 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
41185 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
41186 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
41187 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
41188 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
41191 @c man begin DESCRIPTION gdb
41192 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
41193 going on ``inside'' another program while it executes -- or what another
41194 program was doing at the moment it crashed.
41196 @value{GDBN} can do four main kinds of things (plus other things in support of
41197 these) to help you catch bugs in the act:
41201 Start your program, specifying anything that might affect its behavior.
41204 Make your program stop on specified conditions.
41207 Examine what has happened, when your program has stopped.
41210 Change things in your program, so you can experiment with correcting the
41211 effects of one bug and go on to learn about another.
41214 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
41217 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
41218 commands from the terminal until you tell it to exit with the @value{GDBN}
41219 command @code{quit}. You can get online help from @value{GDBN} itself
41220 by using the command @code{help}.
41222 You can run @code{gdb} with no arguments or options; but the most
41223 usual way to start @value{GDBN} is with one argument or two, specifying an
41224 executable program as the argument:
41230 You can also start with both an executable program and a core file specified:
41236 You can, instead, specify a process ID as a second argument, if you want
41237 to debug a running process:
41245 would attach @value{GDBN} to process @code{1234} (unless you also have a file
41246 named @file{1234}; @value{GDBN} does check for a core file first).
41247 With option @option{-p} you can omit the @var{program} filename.
41249 Here are some of the most frequently needed @value{GDBN} commands:
41251 @c pod2man highlights the right hand side of the @item lines.
41253 @item break [@var{file}:]@var{functiop}
41254 Set a breakpoint at @var{function} (in @var{file}).
41256 @item run [@var{arglist}]
41257 Start your program (with @var{arglist}, if specified).
41260 Backtrace: display the program stack.
41262 @item print @var{expr}
41263 Display the value of an expression.
41266 Continue running your program (after stopping, e.g. at a breakpoint).
41269 Execute next program line (after stopping); step @emph{over} any
41270 function calls in the line.
41272 @item edit [@var{file}:]@var{function}
41273 look at the program line where it is presently stopped.
41275 @item list [@var{file}:]@var{function}
41276 type the text of the program in the vicinity of where it is presently stopped.
41279 Execute next program line (after stopping); step @emph{into} any
41280 function calls in the line.
41282 @item help [@var{name}]
41283 Show information about @value{GDBN} command @var{name}, or general information
41284 about using @value{GDBN}.
41287 Exit from @value{GDBN}.
41291 For full details on @value{GDBN},
41292 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41293 by Richard M. Stallman and Roland H. Pesch. The same text is available online
41294 as the @code{gdb} entry in the @code{info} program.
41298 @c man begin OPTIONS gdb
41299 Any arguments other than options specify an executable
41300 file and core file (or process ID); that is, the first argument
41301 encountered with no
41302 associated option flag is equivalent to a @option{-se} option, and the second,
41303 if any, is equivalent to a @option{-c} option if it's the name of a file.
41305 both long and short forms; both are shown here. The long forms are also
41306 recognized if you truncate them, so long as enough of the option is
41307 present to be unambiguous. (If you prefer, you can flag option
41308 arguments with @option{+} rather than @option{-}, though we illustrate the
41309 more usual convention.)
41311 All the options and command line arguments you give are processed
41312 in sequential order. The order makes a difference when the @option{-x}
41318 List all options, with brief explanations.
41320 @item -symbols=@var{file}
41321 @itemx -s @var{file}
41322 Read symbol table from file @var{file}.
41325 Enable writing into executable and core files.
41327 @item -exec=@var{file}
41328 @itemx -e @var{file}
41329 Use file @var{file} as the executable file to execute when
41330 appropriate, and for examining pure data in conjunction with a core
41333 @item -se=@var{file}
41334 Read symbol table from file @var{file} and use it as the executable
41337 @item -core=@var{file}
41338 @itemx -c @var{file}
41339 Use file @var{file} as a core dump to examine.
41341 @item -command=@var{file}
41342 @itemx -x @var{file}
41343 Execute @value{GDBN} commands from file @var{file}.
41345 @item -ex @var{command}
41346 Execute given @value{GDBN} @var{command}.
41348 @item -directory=@var{directory}
41349 @itemx -d @var{directory}
41350 Add @var{directory} to the path to search for source files.
41353 Do not execute commands from @file{~/.gdbinit}.
41357 Do not execute commands from any @file{.gdbinit} initialization files.
41361 ``Quiet''. Do not print the introductory and copyright messages. These
41362 messages are also suppressed in batch mode.
41365 Run in batch mode. Exit with status @code{0} after processing all the command
41366 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
41367 Exit with nonzero status if an error occurs in executing the @value{GDBN}
41368 commands in the command files.
41370 Batch mode may be useful for running @value{GDBN} as a filter, for example to
41371 download and run a program on another computer; in order to make this
41372 more useful, the message
41375 Program exited normally.
41379 (which is ordinarily issued whenever a program running under @value{GDBN} control
41380 terminates) is not issued when running in batch mode.
41382 @item -cd=@var{directory}
41383 Run @value{GDBN} using @var{directory} as its working directory,
41384 instead of the current directory.
41388 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
41389 @value{GDBN} to output the full file name and line number in a standard,
41390 recognizable fashion each time a stack frame is displayed (which
41391 includes each time the program stops). This recognizable format looks
41392 like two @samp{\032} characters, followed by the file name, line number
41393 and character position separated by colons, and a newline. The
41394 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
41395 characters as a signal to display the source code for the frame.
41398 Set the line speed (baud rate or bits per second) of any serial
41399 interface used by @value{GDBN} for remote debugging.
41401 @item -tty=@var{device}
41402 Run using @var{device} for your program's standard input and output.
41406 @c man begin SEEALSO gdb
41408 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41409 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41410 documentation are properly installed at your site, the command
41417 should give you access to the complete manual.
41419 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41420 Richard M. Stallman and Roland H. Pesch, July 1991.
41424 @node gdbserver man
41425 @heading gdbserver man
41427 @c man title gdbserver Remote Server for the GNU Debugger
41429 @c man begin SYNOPSIS gdbserver
41430 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
41432 gdbserver --attach @var{comm} @var{pid}
41434 gdbserver --multi @var{comm}
41438 @c man begin DESCRIPTION gdbserver
41439 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
41440 than the one which is running the program being debugged.
41443 @subheading Usage (server (target) side)
41446 Usage (server (target) side):
41449 First, you need to have a copy of the program you want to debug put onto
41450 the target system. The program can be stripped to save space if needed, as
41451 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
41452 the @value{GDBN} running on the host system.
41454 To use the server, you log on to the target system, and run the @command{gdbserver}
41455 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
41456 your program, and (c) its arguments. The general syntax is:
41459 target> gdbserver @var{comm} @var{program} [@var{args} ...]
41462 For example, using a serial port, you might say:
41466 @c @file would wrap it as F</dev/com1>.
41467 target> gdbserver /dev/com1 emacs foo.txt
41470 target> gdbserver @file{/dev/com1} emacs foo.txt
41474 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
41475 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
41476 waits patiently for the host @value{GDBN} to communicate with it.
41478 To use a TCP connection, you could say:
41481 target> gdbserver host:2345 emacs foo.txt
41484 This says pretty much the same thing as the last example, except that we are
41485 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
41486 that we are expecting to see a TCP connection from @code{host} to local TCP port
41487 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
41488 want for the port number as long as it does not conflict with any existing TCP
41489 ports on the target system. This same port number must be used in the host
41490 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
41491 you chose a port number that conflicts with another service, @command{gdbserver} will
41492 print an error message and exit.
41494 @command{gdbserver} can also attach to running programs.
41495 This is accomplished via the @option{--attach} argument. The syntax is:
41498 target> gdbserver --attach @var{comm} @var{pid}
41501 @var{pid} is the process ID of a currently running process. It isn't
41502 necessary to point @command{gdbserver} at a binary for the running process.
41504 To start @code{gdbserver} without supplying an initial command to run
41505 or process ID to attach, use the @option{--multi} command line option.
41506 In such case you should connect using @kbd{target extended-remote} to start
41507 the program you want to debug.
41510 target> gdbserver --multi @var{comm}
41514 @subheading Usage (host side)
41520 You need an unstripped copy of the target program on your host system, since
41521 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
41522 would, with the target program as the first argument. (You may need to use the
41523 @option{--baud} option if the serial line is running at anything except 9600 baud.)
41524 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
41525 new command you need to know about is @code{target remote}
41526 (or @code{target extended-remote}). Its argument is either
41527 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
41528 descriptor. For example:
41532 @c @file would wrap it as F</dev/ttyb>.
41533 (gdb) target remote /dev/ttyb
41536 (gdb) target remote @file{/dev/ttyb}
41541 communicates with the server via serial line @file{/dev/ttyb}, and:
41544 (gdb) target remote the-target:2345
41548 communicates via a TCP connection to port 2345 on host `the-target', where
41549 you previously started up @command{gdbserver} with the same port number. Note that for
41550 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
41551 command, otherwise you may get an error that looks something like
41552 `Connection refused'.
41554 @command{gdbserver} can also debug multiple inferiors at once,
41557 the @value{GDBN} manual in node @code{Inferiors and Programs}
41558 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
41561 @ref{Inferiors and Programs}.
41563 In such case use the @code{extended-remote} @value{GDBN} command variant:
41566 (gdb) target extended-remote the-target:2345
41569 The @command{gdbserver} option @option{--multi} may or may not be used in such
41573 @c man begin OPTIONS gdbserver
41574 There are three different modes for invoking @command{gdbserver}:
41579 Debug a specific program specified by its program name:
41582 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
41585 The @var{comm} parameter specifies how should the server communicate
41586 with @value{GDBN}; it is either a device name (to use a serial line),
41587 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
41588 stdin/stdout of @code{gdbserver}. Specify the name of the program to
41589 debug in @var{prog}. Any remaining arguments will be passed to the
41590 program verbatim. When the program exits, @value{GDBN} will close the
41591 connection, and @code{gdbserver} will exit.
41594 Debug a specific program by specifying the process ID of a running
41598 gdbserver --attach @var{comm} @var{pid}
41601 The @var{comm} parameter is as described above. Supply the process ID
41602 of a running program in @var{pid}; @value{GDBN} will do everything
41603 else. Like with the previous mode, when the process @var{pid} exits,
41604 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
41607 Multi-process mode -- debug more than one program/process:
41610 gdbserver --multi @var{comm}
41613 In this mode, @value{GDBN} can instruct @command{gdbserver} which
41614 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
41615 close the connection when a process being debugged exits, so you can
41616 debug several processes in the same session.
41619 In each of the modes you may specify these options:
41624 List all options, with brief explanations.
41627 This option causes @command{gdbserver} to print its version number and exit.
41630 @command{gdbserver} will attach to a running program. The syntax is:
41633 target> gdbserver --attach @var{comm} @var{pid}
41636 @var{pid} is the process ID of a currently running process. It isn't
41637 necessary to point @command{gdbserver} at a binary for the running process.
41640 To start @code{gdbserver} without supplying an initial command to run
41641 or process ID to attach, use this command line option.
41642 Then you can connect using @kbd{target extended-remote} and start
41643 the program you want to debug. The syntax is:
41646 target> gdbserver --multi @var{comm}
41650 Instruct @code{gdbserver} to display extra status information about the debugging
41652 This option is intended for @code{gdbserver} development and for bug reports to
41655 @item --remote-debug
41656 Instruct @code{gdbserver} to display remote protocol debug output.
41657 This option is intended for @code{gdbserver} development and for bug reports to
41660 @item --debug-format=option1@r{[},option2,...@r{]}
41661 Instruct @code{gdbserver} to include extra information in each line
41662 of debugging output.
41663 @xref{Other Command-Line Arguments for gdbserver}.
41666 Specify a wrapper to launch programs
41667 for debugging. The option should be followed by the name of the
41668 wrapper, then any command-line arguments to pass to the wrapper, then
41669 @kbd{--} indicating the end of the wrapper arguments.
41672 By default, @command{gdbserver} keeps the listening TCP port open, so that
41673 additional connections are possible. However, if you start @code{gdbserver}
41674 with the @option{--once} option, it will stop listening for any further
41675 connection attempts after connecting to the first @value{GDBN} session.
41677 @c --disable-packet is not documented for users.
41679 @c --disable-randomization and --no-disable-randomization are superseded by
41680 @c QDisableRandomization.
41685 @c man begin SEEALSO gdbserver
41687 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41688 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41689 documentation are properly installed at your site, the command
41695 should give you access to the complete manual.
41697 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41698 Richard M. Stallman and Roland H. Pesch, July 1991.
41705 @c man title gcore Generate a core file of a running program
41708 @c man begin SYNOPSIS gcore
41709 gcore [-o @var{filename}] @var{pid}
41713 @c man begin DESCRIPTION gcore
41714 Generate a core dump of a running program with process ID @var{pid}.
41715 Produced file is equivalent to a kernel produced core file as if the process
41716 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
41717 limit). Unlike after a crash, after @command{gcore} the program remains
41718 running without any change.
41721 @c man begin OPTIONS gcore
41723 @item -o @var{filename}
41724 The optional argument
41725 @var{filename} specifies the file name where to put the core dump.
41726 If not specified, the file name defaults to @file{core.@var{pid}},
41727 where @var{pid} is the running program process ID.
41731 @c man begin SEEALSO gcore
41733 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41734 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41735 documentation are properly installed at your site, the command
41742 should give you access to the complete manual.
41744 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41745 Richard M. Stallman and Roland H. Pesch, July 1991.
41752 @c man title gdbinit GDB initialization scripts
41755 @c man begin SYNOPSIS gdbinit
41756 @ifset SYSTEM_GDBINIT
41757 @value{SYSTEM_GDBINIT}
41766 @c man begin DESCRIPTION gdbinit
41767 These files contain @value{GDBN} commands to automatically execute during
41768 @value{GDBN} startup. The lines of contents are canned sequences of commands,
41771 the @value{GDBN} manual in node @code{Sequences}
41772 -- shell command @code{info -f gdb -n Sequences}.
41778 Please read more in
41780 the @value{GDBN} manual in node @code{Startup}
41781 -- shell command @code{info -f gdb -n Startup}.
41788 @ifset SYSTEM_GDBINIT
41789 @item @value{SYSTEM_GDBINIT}
41791 @ifclear SYSTEM_GDBINIT
41792 @item (not enabled with @code{--with-system-gdbinit} during compilation)
41794 System-wide initialization file. It is executed unless user specified
41795 @value{GDBN} option @code{-nx} or @code{-n}.
41798 the @value{GDBN} manual in node @code{System-wide configuration}
41799 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
41802 @ref{System-wide configuration}.
41806 User initialization file. It is executed unless user specified
41807 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
41810 Initialization file for current directory. It may need to be enabled with
41811 @value{GDBN} security command @code{set auto-load local-gdbinit}.
41814 the @value{GDBN} manual in node @code{Init File in the Current Directory}
41815 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
41818 @ref{Init File in the Current Directory}.
41823 @c man begin SEEALSO gdbinit
41825 gdb(1), @code{info -f gdb -n Startup}
41827 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41828 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41829 documentation are properly installed at your site, the command
41835 should give you access to the complete manual.
41837 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41838 Richard M. Stallman and Roland H. Pesch, July 1991.
41844 @node GNU Free Documentation License
41845 @appendix GNU Free Documentation License
41848 @node Concept Index
41849 @unnumbered Concept Index
41853 @node Command and Variable Index
41854 @unnumbered Command, Variable, and Function Index
41859 % I think something like @@colophon should be in texinfo. In the
41861 \long\def\colophon{\hbox to0pt{}\vfill
41862 \centerline{The body of this manual is set in}
41863 \centerline{\fontname\tenrm,}
41864 \centerline{with headings in {\bf\fontname\tenbf}}
41865 \centerline{and examples in {\tt\fontname\tentt}.}
41866 \centerline{{\it\fontname\tenit\/},}
41867 \centerline{{\bf\fontname\tenbf}, and}
41868 \centerline{{\sl\fontname\tensl\/}}
41869 \centerline{are used for emphasis.}\vfill}
41871 % Blame: doc@@cygnus.com, 1991.