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}).
1239 @c @cindex @code{--xdb}
1240 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1241 @c For information, see the file @file{xdb_trans.html}, which is usually
1242 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1245 @item -interpreter @var{interp}
1246 @cindex @code{--interpreter}
1247 Use the interpreter @var{interp} for interface with the controlling
1248 program or device. This option is meant to be set by programs which
1249 communicate with @value{GDBN} using it as a back end.
1250 @xref{Interpreters, , Command Interpreters}.
1252 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1253 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1254 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1255 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1256 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1257 @sc{gdb/mi} interfaces are no longer supported.
1260 @cindex @code{--write}
1261 Open the executable and core files for both reading and writing. This
1262 is equivalent to the @samp{set write on} command inside @value{GDBN}
1266 @cindex @code{--statistics}
1267 This option causes @value{GDBN} to print statistics about time and
1268 memory usage after it completes each command and returns to the prompt.
1271 @cindex @code{--version}
1272 This option causes @value{GDBN} to print its version number and
1273 no-warranty blurb, and exit.
1275 @item -configuration
1276 @cindex @code{--configuration}
1277 This option causes @value{GDBN} to print details about its build-time
1278 configuration parameters, and then exit. These details can be
1279 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1284 @subsection What @value{GDBN} Does During Startup
1285 @cindex @value{GDBN} startup
1287 Here's the description of what @value{GDBN} does during session startup:
1291 Sets up the command interpreter as specified by the command line
1292 (@pxref{Mode Options, interpreter}).
1296 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1297 used when building @value{GDBN}; @pxref{System-wide configuration,
1298 ,System-wide configuration and settings}) and executes all the commands in
1301 @anchor{Home Directory Init File}
1303 Reads the init file (if any) in your home directory@footnote{On
1304 DOS/Windows systems, the home directory is the one pointed to by the
1305 @code{HOME} environment variable.} and executes all the commands in
1308 @anchor{Option -init-eval-command}
1310 Executes commands and command files specified by the @samp{-iex} and
1311 @samp{-ix} options in their specified order. Usually you should use the
1312 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1313 settings before @value{GDBN} init files get executed and before inferior
1317 Processes command line options and operands.
1319 @anchor{Init File in the Current Directory during Startup}
1321 Reads and executes the commands from init file (if any) in the current
1322 working directory as long as @samp{set auto-load local-gdbinit} is set to
1323 @samp{on} (@pxref{Init File in the Current Directory}).
1324 This is only done if the current directory is
1325 different from your home directory. Thus, you can have more than one
1326 init file, one generic in your home directory, and another, specific
1327 to the program you are debugging, in the directory where you invoke
1331 If the command line specified a program to debug, or a process to
1332 attach to, or a core file, @value{GDBN} loads any auto-loaded
1333 scripts provided for the program or for its loaded shared libraries.
1334 @xref{Auto-loading}.
1336 If you wish to disable the auto-loading during startup,
1337 you must do something like the following:
1340 $ gdb -iex "set auto-load python-scripts off" myprogram
1343 Option @samp{-ex} does not work because the auto-loading is then turned
1347 Executes commands and command files specified by the @samp{-ex} and
1348 @samp{-x} options in their specified order. @xref{Command Files}, for
1349 more details about @value{GDBN} command files.
1352 Reads the command history recorded in the @dfn{history file}.
1353 @xref{Command History}, for more details about the command history and the
1354 files where @value{GDBN} records it.
1357 Init files use the same syntax as @dfn{command files} (@pxref{Command
1358 Files}) and are processed by @value{GDBN} in the same way. The init
1359 file in your home directory can set options (such as @samp{set
1360 complaints}) that affect subsequent processing of command line options
1361 and operands. Init files are not executed if you use the @samp{-nx}
1362 option (@pxref{Mode Options, ,Choosing Modes}).
1364 To display the list of init files loaded by gdb at startup, you
1365 can use @kbd{gdb --help}.
1367 @cindex init file name
1368 @cindex @file{.gdbinit}
1369 @cindex @file{gdb.ini}
1370 The @value{GDBN} init files are normally called @file{.gdbinit}.
1371 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1372 the limitations of file names imposed by DOS filesystems. The Windows
1373 port of @value{GDBN} uses the standard name, but if it finds a
1374 @file{gdb.ini} file in your home directory, it warns you about that
1375 and suggests to rename the file to the standard name.
1379 @section Quitting @value{GDBN}
1380 @cindex exiting @value{GDBN}
1381 @cindex leaving @value{GDBN}
1384 @kindex quit @r{[}@var{expression}@r{]}
1385 @kindex q @r{(@code{quit})}
1386 @item quit @r{[}@var{expression}@r{]}
1388 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1389 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1390 do not supply @var{expression}, @value{GDBN} will terminate normally;
1391 otherwise it will terminate using the result of @var{expression} as the
1396 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1397 terminates the action of any @value{GDBN} command that is in progress and
1398 returns to @value{GDBN} command level. It is safe to type the interrupt
1399 character at any time because @value{GDBN} does not allow it to take effect
1400 until a time when it is safe.
1402 If you have been using @value{GDBN} to control an attached process or
1403 device, you can release it with the @code{detach} command
1404 (@pxref{Attach, ,Debugging an Already-running Process}).
1406 @node Shell Commands
1407 @section Shell Commands
1409 If you need to execute occasional shell commands during your
1410 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1411 just use the @code{shell} command.
1416 @cindex shell escape
1417 @item shell @var{command-string}
1418 @itemx !@var{command-string}
1419 Invoke a standard shell to execute @var{command-string}.
1420 Note that no space is needed between @code{!} and @var{command-string}.
1421 If it exists, the environment variable @code{SHELL} determines which
1422 shell to run. Otherwise @value{GDBN} uses the default shell
1423 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1426 The utility @code{make} is often needed in development environments.
1427 You do not have to use the @code{shell} command for this purpose in
1432 @cindex calling make
1433 @item make @var{make-args}
1434 Execute the @code{make} program with the specified
1435 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1438 @node Logging Output
1439 @section Logging Output
1440 @cindex logging @value{GDBN} output
1441 @cindex save @value{GDBN} output to a file
1443 You may want to save the output of @value{GDBN} commands to a file.
1444 There are several commands to control @value{GDBN}'s logging.
1448 @item set logging on
1450 @item set logging off
1452 @cindex logging file name
1453 @item set logging file @var{file}
1454 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1455 @item set logging overwrite [on|off]
1456 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1457 you want @code{set logging on} to overwrite the logfile instead.
1458 @item set logging redirect [on|off]
1459 By default, @value{GDBN} output will go to both the terminal and the logfile.
1460 Set @code{redirect} if you want output to go only to the log file.
1461 @kindex show logging
1463 Show the current values of the logging settings.
1467 @chapter @value{GDBN} Commands
1469 You can abbreviate a @value{GDBN} command to the first few letters of the command
1470 name, if that abbreviation is unambiguous; and you can repeat certain
1471 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1472 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1473 show you the alternatives available, if there is more than one possibility).
1476 * Command Syntax:: How to give commands to @value{GDBN}
1477 * Completion:: Command completion
1478 * Help:: How to ask @value{GDBN} for help
1481 @node Command Syntax
1482 @section Command Syntax
1484 A @value{GDBN} command is a single line of input. There is no limit on
1485 how long it can be. It starts with a command name, which is followed by
1486 arguments whose meaning depends on the command name. For example, the
1487 command @code{step} accepts an argument which is the number of times to
1488 step, as in @samp{step 5}. You can also use the @code{step} command
1489 with no arguments. Some commands do not allow any arguments.
1491 @cindex abbreviation
1492 @value{GDBN} command names may always be truncated if that abbreviation is
1493 unambiguous. Other possible command abbreviations are listed in the
1494 documentation for individual commands. In some cases, even ambiguous
1495 abbreviations are allowed; for example, @code{s} is specially defined as
1496 equivalent to @code{step} even though there are other commands whose
1497 names start with @code{s}. You can test abbreviations by using them as
1498 arguments to the @code{help} command.
1500 @cindex repeating commands
1501 @kindex RET @r{(repeat last command)}
1502 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1503 repeat the previous command. Certain commands (for example, @code{run})
1504 will not repeat this way; these are commands whose unintentional
1505 repetition might cause trouble and which you are unlikely to want to
1506 repeat. User-defined commands can disable this feature; see
1507 @ref{Define, dont-repeat}.
1509 The @code{list} and @code{x} commands, when you repeat them with
1510 @key{RET}, construct new arguments rather than repeating
1511 exactly as typed. This permits easy scanning of source or memory.
1513 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1514 output, in a way similar to the common utility @code{more}
1515 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1516 @key{RET} too many in this situation, @value{GDBN} disables command
1517 repetition after any command that generates this sort of display.
1519 @kindex # @r{(a comment)}
1521 Any text from a @kbd{#} to the end of the line is a comment; it does
1522 nothing. This is useful mainly in command files (@pxref{Command
1523 Files,,Command Files}).
1525 @cindex repeating command sequences
1526 @kindex Ctrl-o @r{(operate-and-get-next)}
1527 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1528 commands. This command accepts the current line, like @key{RET}, and
1529 then fetches the next line relative to the current line from the history
1533 @section Command Completion
1536 @cindex word completion
1537 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1538 only one possibility; it can also show you what the valid possibilities
1539 are for the next word in a command, at any time. This works for @value{GDBN}
1540 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1542 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1543 of a word. If there is only one possibility, @value{GDBN} fills in the
1544 word, and waits for you to finish the command (or press @key{RET} to
1545 enter it). For example, if you type
1547 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1548 @c complete accuracy in these examples; space introduced for clarity.
1549 @c If texinfo enhancements make it unnecessary, it would be nice to
1550 @c replace " @key" by "@key" in the following...
1552 (@value{GDBP}) info bre @key{TAB}
1556 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1557 the only @code{info} subcommand beginning with @samp{bre}:
1560 (@value{GDBP}) info breakpoints
1564 You can either press @key{RET} at this point, to run the @code{info
1565 breakpoints} command, or backspace and enter something else, if
1566 @samp{breakpoints} does not look like the command you expected. (If you
1567 were sure you wanted @code{info breakpoints} in the first place, you
1568 might as well just type @key{RET} immediately after @samp{info bre},
1569 to exploit command abbreviations rather than command completion).
1571 If there is more than one possibility for the next word when you press
1572 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1573 characters and try again, or just press @key{TAB} a second time;
1574 @value{GDBN} displays all the possible completions for that word. For
1575 example, you might want to set a breakpoint on a subroutine whose name
1576 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1577 just sounds the bell. Typing @key{TAB} again displays all the
1578 function names in your program that begin with those characters, for
1582 (@value{GDBP}) b make_ @key{TAB}
1583 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1584 make_a_section_from_file make_environ
1585 make_abs_section make_function_type
1586 make_blockvector make_pointer_type
1587 make_cleanup make_reference_type
1588 make_command make_symbol_completion_list
1589 (@value{GDBP}) b make_
1593 After displaying the available possibilities, @value{GDBN} copies your
1594 partial input (@samp{b make_} in the example) so you can finish the
1597 If you just want to see the list of alternatives in the first place, you
1598 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1599 means @kbd{@key{META} ?}. You can type this either by holding down a
1600 key designated as the @key{META} shift on your keyboard (if there is
1601 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1603 If the number of possible completions is large, @value{GDBN} will
1604 print as much of the list as it has collected, as well as a message
1605 indicating that the list may be truncated.
1608 (@value{GDBP}) b m@key{TAB}@key{TAB}
1610 <... the rest of the possible completions ...>
1611 *** List may be truncated, max-completions reached. ***
1616 This behavior can be controlled with the following commands:
1619 @kindex set max-completions
1620 @item set max-completions @var{limit}
1621 @itemx set max-completions unlimited
1622 Set the maximum number of completion candidates. @value{GDBN} will
1623 stop looking for more completions once it collects this many candidates.
1624 This is useful when completing on things like function names as collecting
1625 all the possible candidates can be time consuming.
1626 The default value is 200. A value of zero disables tab-completion.
1627 Note that setting either no limit or a very large limit can make
1629 @kindex show max-completions
1630 @item show max-completions
1631 Show the maximum number of candidates that @value{GDBN} will collect and show
1635 @cindex quotes in commands
1636 @cindex completion of quoted strings
1637 Sometimes the string you need, while logically a ``word'', may contain
1638 parentheses or other characters that @value{GDBN} normally excludes from
1639 its notion of a word. To permit word completion to work in this
1640 situation, you may enclose words in @code{'} (single quote marks) in
1641 @value{GDBN} commands.
1643 The most likely situation where you might need this is in typing the
1644 name of a C@t{++} function. This is because C@t{++} allows function
1645 overloading (multiple definitions of the same function, distinguished
1646 by argument type). For example, when you want to set a breakpoint you
1647 may need to distinguish whether you mean the version of @code{name}
1648 that takes an @code{int} parameter, @code{name(int)}, or the version
1649 that takes a @code{float} parameter, @code{name(float)}. To use the
1650 word-completion facilities in this situation, type a single quote
1651 @code{'} at the beginning of the function name. This alerts
1652 @value{GDBN} that it may need to consider more information than usual
1653 when you press @key{TAB} or @kbd{M-?} to request word completion:
1656 (@value{GDBP}) b 'bubble( @kbd{M-?}
1657 bubble(double,double) bubble(int,int)
1658 (@value{GDBP}) b 'bubble(
1661 In some cases, @value{GDBN} can tell that completing a name requires using
1662 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1663 completing as much as it can) if you do not type the quote in the first
1667 (@value{GDBP}) b bub @key{TAB}
1668 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1669 (@value{GDBP}) b 'bubble(
1673 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1674 you have not yet started typing the argument list when you ask for
1675 completion on an overloaded symbol.
1677 For more information about overloaded functions, see @ref{C Plus Plus
1678 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1679 overload-resolution off} to disable overload resolution;
1680 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1682 @cindex completion of structure field names
1683 @cindex structure field name completion
1684 @cindex completion of union field names
1685 @cindex union field name completion
1686 When completing in an expression which looks up a field in a
1687 structure, @value{GDBN} also tries@footnote{The completer can be
1688 confused by certain kinds of invalid expressions. Also, it only
1689 examines the static type of the expression, not the dynamic type.} to
1690 limit completions to the field names available in the type of the
1694 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1695 magic to_fputs to_rewind
1696 to_data to_isatty to_write
1697 to_delete to_put to_write_async_safe
1702 This is because the @code{gdb_stdout} is a variable of the type
1703 @code{struct ui_file} that is defined in @value{GDBN} sources as
1710 ui_file_flush_ftype *to_flush;
1711 ui_file_write_ftype *to_write;
1712 ui_file_write_async_safe_ftype *to_write_async_safe;
1713 ui_file_fputs_ftype *to_fputs;
1714 ui_file_read_ftype *to_read;
1715 ui_file_delete_ftype *to_delete;
1716 ui_file_isatty_ftype *to_isatty;
1717 ui_file_rewind_ftype *to_rewind;
1718 ui_file_put_ftype *to_put;
1725 @section Getting Help
1726 @cindex online documentation
1729 You can always ask @value{GDBN} itself for information on its commands,
1730 using the command @code{help}.
1733 @kindex h @r{(@code{help})}
1736 You can use @code{help} (abbreviated @code{h}) with no arguments to
1737 display a short list of named classes of commands:
1741 List of classes of commands:
1743 aliases -- Aliases of other commands
1744 breakpoints -- Making program stop at certain points
1745 data -- Examining data
1746 files -- Specifying and examining files
1747 internals -- Maintenance commands
1748 obscure -- Obscure features
1749 running -- Running the program
1750 stack -- Examining the stack
1751 status -- Status inquiries
1752 support -- Support facilities
1753 tracepoints -- Tracing of program execution without
1754 stopping the program
1755 user-defined -- User-defined commands
1757 Type "help" followed by a class name for a list of
1758 commands in that class.
1759 Type "help" followed by command name for full
1761 Command name abbreviations are allowed if unambiguous.
1764 @c the above line break eliminates huge line overfull...
1766 @item help @var{class}
1767 Using one of the general help classes as an argument, you can get a
1768 list of the individual commands in that class. For example, here is the
1769 help display for the class @code{status}:
1772 (@value{GDBP}) help status
1777 @c Line break in "show" line falsifies real output, but needed
1778 @c to fit in smallbook page size.
1779 info -- Generic command for showing things
1780 about the program being debugged
1781 show -- Generic command for showing things
1784 Type "help" followed by command name for full
1786 Command name abbreviations are allowed if unambiguous.
1790 @item help @var{command}
1791 With a command name as @code{help} argument, @value{GDBN} displays a
1792 short paragraph on how to use that command.
1795 @item apropos @var{args}
1796 The @code{apropos} command searches through all of the @value{GDBN}
1797 commands, and their documentation, for the regular expression specified in
1798 @var{args}. It prints out all matches found. For example:
1809 alias -- Define a new command that is an alias of an existing command
1810 aliases -- Aliases of other commands
1811 d -- Delete some breakpoints or auto-display expressions
1812 del -- Delete some breakpoints or auto-display expressions
1813 delete -- Delete some breakpoints or auto-display expressions
1818 @item complete @var{args}
1819 The @code{complete @var{args}} command lists all the possible completions
1820 for the beginning of a command. Use @var{args} to specify the beginning of the
1821 command you want completed. For example:
1827 @noindent results in:
1838 @noindent This is intended for use by @sc{gnu} Emacs.
1841 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1842 and @code{show} to inquire about the state of your program, or the state
1843 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1844 manual introduces each of them in the appropriate context. The listings
1845 under @code{info} and under @code{show} in the Command, Variable, and
1846 Function Index point to all the sub-commands. @xref{Command and Variable
1852 @kindex i @r{(@code{info})}
1854 This command (abbreviated @code{i}) is for describing the state of your
1855 program. For example, you can show the arguments passed to a function
1856 with @code{info args}, list the registers currently in use with @code{info
1857 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1858 You can get a complete list of the @code{info} sub-commands with
1859 @w{@code{help info}}.
1863 You can assign the result of an expression to an environment variable with
1864 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1865 @code{set prompt $}.
1869 In contrast to @code{info}, @code{show} is for describing the state of
1870 @value{GDBN} itself.
1871 You can change most of the things you can @code{show}, by using the
1872 related command @code{set}; for example, you can control what number
1873 system is used for displays with @code{set radix}, or simply inquire
1874 which is currently in use with @code{show radix}.
1877 To display all the settable parameters and their current
1878 values, you can use @code{show} with no arguments; you may also use
1879 @code{info set}. Both commands produce the same display.
1880 @c FIXME: "info set" violates the rule that "info" is for state of
1881 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1882 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1886 Here are several miscellaneous @code{show} subcommands, all of which are
1887 exceptional in lacking corresponding @code{set} commands:
1890 @kindex show version
1891 @cindex @value{GDBN} version number
1893 Show what version of @value{GDBN} is running. You should include this
1894 information in @value{GDBN} bug-reports. If multiple versions of
1895 @value{GDBN} are in use at your site, you may need to determine which
1896 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1897 commands are introduced, and old ones may wither away. Also, many
1898 system vendors ship variant versions of @value{GDBN}, and there are
1899 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1900 The version number is the same as the one announced when you start
1903 @kindex show copying
1904 @kindex info copying
1905 @cindex display @value{GDBN} copyright
1908 Display information about permission for copying @value{GDBN}.
1910 @kindex show warranty
1911 @kindex info warranty
1913 @itemx info warranty
1914 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1915 if your version of @value{GDBN} comes with one.
1917 @kindex show configuration
1918 @item show configuration
1919 Display detailed information about the way @value{GDBN} was configured
1920 when it was built. This displays the optional arguments passed to the
1921 @file{configure} script and also configuration parameters detected
1922 automatically by @command{configure}. When reporting a @value{GDBN}
1923 bug (@pxref{GDB Bugs}), it is important to include this information in
1929 @chapter Running Programs Under @value{GDBN}
1931 When you run a program under @value{GDBN}, you must first generate
1932 debugging information when you compile it.
1934 You may start @value{GDBN} with its arguments, if any, in an environment
1935 of your choice. If you are doing native debugging, you may redirect
1936 your program's input and output, debug an already running process, or
1937 kill a child process.
1940 * Compilation:: Compiling for debugging
1941 * Starting:: Starting your program
1942 * Arguments:: Your program's arguments
1943 * Environment:: Your program's environment
1945 * Working Directory:: Your program's working directory
1946 * Input/Output:: Your program's input and output
1947 * Attach:: Debugging an already-running process
1948 * Kill Process:: Killing the child process
1950 * Inferiors and Programs:: Debugging multiple inferiors and programs
1951 * Threads:: Debugging programs with multiple threads
1952 * Forks:: Debugging forks
1953 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1957 @section Compiling for Debugging
1959 In order to debug a program effectively, you need to generate
1960 debugging information when you compile it. This debugging information
1961 is stored in the object file; it describes the data type of each
1962 variable or function and the correspondence between source line numbers
1963 and addresses in the executable code.
1965 To request debugging information, specify the @samp{-g} option when you run
1968 Programs that are to be shipped to your customers are compiled with
1969 optimizations, using the @samp{-O} compiler option. However, some
1970 compilers are unable to handle the @samp{-g} and @samp{-O} options
1971 together. Using those compilers, you cannot generate optimized
1972 executables containing debugging information.
1974 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1975 without @samp{-O}, making it possible to debug optimized code. We
1976 recommend that you @emph{always} use @samp{-g} whenever you compile a
1977 program. You may think your program is correct, but there is no sense
1978 in pushing your luck. For more information, see @ref{Optimized Code}.
1980 Older versions of the @sc{gnu} C compiler permitted a variant option
1981 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1982 format; if your @sc{gnu} C compiler has this option, do not use it.
1984 @value{GDBN} knows about preprocessor macros and can show you their
1985 expansion (@pxref{Macros}). Most compilers do not include information
1986 about preprocessor macros in the debugging information if you specify
1987 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
1988 the @sc{gnu} C compiler, provides macro information if you are using
1989 the DWARF debugging format, and specify the option @option{-g3}.
1991 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1992 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1993 information on @value{NGCC} options affecting debug information.
1995 You will have the best debugging experience if you use the latest
1996 version of the DWARF debugging format that your compiler supports.
1997 DWARF is currently the most expressive and best supported debugging
1998 format in @value{GDBN}.
2002 @section Starting your Program
2008 @kindex r @r{(@code{run})}
2011 Use the @code{run} command to start your program under @value{GDBN}.
2012 You must first specify the program name with an argument to
2013 @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
2014 @value{GDBN}}), or by using the @code{file} or @code{exec-file}
2015 command (@pxref{Files, ,Commands to Specify Files}).
2019 If you are running your program in an execution environment that
2020 supports processes, @code{run} creates an inferior process and makes
2021 that process run your program. In some environments without processes,
2022 @code{run} jumps to the start of your program. Other targets,
2023 like @samp{remote}, are always running. If you get an error
2024 message like this one:
2027 The "remote" target does not support "run".
2028 Try "help target" or "continue".
2032 then use @code{continue} to run your program. You may need @code{load}
2033 first (@pxref{load}).
2035 The execution of a program is affected by certain information it
2036 receives from its superior. @value{GDBN} provides ways to specify this
2037 information, which you must do @emph{before} starting your program. (You
2038 can change it after starting your program, but such changes only affect
2039 your program the next time you start it.) This information may be
2040 divided into four categories:
2043 @item The @emph{arguments.}
2044 Specify the arguments to give your program as the arguments of the
2045 @code{run} command. If a shell is available on your target, the shell
2046 is used to pass the arguments, so that you may use normal conventions
2047 (such as wildcard expansion or variable substitution) in describing
2049 In Unix systems, you can control which shell is used with the
2050 @code{SHELL} environment variable. If you do not define @code{SHELL},
2051 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2052 use of any shell with the @code{set startup-with-shell} command (see
2055 @item The @emph{environment.}
2056 Your program normally inherits its environment from @value{GDBN}, but you can
2057 use the @value{GDBN} commands @code{set environment} and @code{unset
2058 environment} to change parts of the environment that affect
2059 your program. @xref{Environment, ,Your Program's Environment}.
2061 @item The @emph{working directory.}
2062 Your program inherits its working directory from @value{GDBN}. You can set
2063 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
2064 @xref{Working Directory, ,Your Program's Working Directory}.
2066 @item The @emph{standard input and output.}
2067 Your program normally uses the same device for standard input and
2068 standard output as @value{GDBN} is using. You can redirect input and output
2069 in the @code{run} command line, or you can use the @code{tty} command to
2070 set a different device for your program.
2071 @xref{Input/Output, ,Your Program's Input and Output}.
2074 @emph{Warning:} While input and output redirection work, you cannot use
2075 pipes to pass the output of the program you are debugging to another
2076 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2080 When you issue the @code{run} command, your program begins to execute
2081 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2082 of how to arrange for your program to stop. Once your program has
2083 stopped, you may call functions in your program, using the @code{print}
2084 or @code{call} commands. @xref{Data, ,Examining Data}.
2086 If the modification time of your symbol file has changed since the last
2087 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2088 table, and reads it again. When it does this, @value{GDBN} tries to retain
2089 your current breakpoints.
2094 @cindex run to main procedure
2095 The name of the main procedure can vary from language to language.
2096 With C or C@t{++}, the main procedure name is always @code{main}, but
2097 other languages such as Ada do not require a specific name for their
2098 main procedure. The debugger provides a convenient way to start the
2099 execution of the program and to stop at the beginning of the main
2100 procedure, depending on the language used.
2102 The @samp{start} command does the equivalent of setting a temporary
2103 breakpoint at the beginning of the main procedure and then invoking
2104 the @samp{run} command.
2106 @cindex elaboration phase
2107 Some programs contain an @dfn{elaboration} phase where some startup code is
2108 executed before the main procedure is called. This depends on the
2109 languages used to write your program. In C@t{++}, for instance,
2110 constructors for static and global objects are executed before
2111 @code{main} is called. It is therefore possible that the debugger stops
2112 before reaching the main procedure. However, the temporary breakpoint
2113 will remain to halt execution.
2115 Specify the arguments to give to your program as arguments to the
2116 @samp{start} command. These arguments will be given verbatim to the
2117 underlying @samp{run} command. Note that the same arguments will be
2118 reused if no argument is provided during subsequent calls to
2119 @samp{start} or @samp{run}.
2121 It is sometimes necessary to debug the program during elaboration. In
2122 these cases, using the @code{start} command would stop the execution of
2123 your program too late, as the program would have already completed the
2124 elaboration phase. Under these circumstances, insert breakpoints in your
2125 elaboration code before running your program.
2127 @anchor{set exec-wrapper}
2128 @kindex set exec-wrapper
2129 @item set exec-wrapper @var{wrapper}
2130 @itemx show exec-wrapper
2131 @itemx unset exec-wrapper
2132 When @samp{exec-wrapper} is set, the specified wrapper is used to
2133 launch programs for debugging. @value{GDBN} starts your program
2134 with a shell command of the form @kbd{exec @var{wrapper}
2135 @var{program}}. Quoting is added to @var{program} and its
2136 arguments, but not to @var{wrapper}, so you should add quotes if
2137 appropriate for your shell. The wrapper runs until it executes
2138 your program, and then @value{GDBN} takes control.
2140 You can use any program that eventually calls @code{execve} with
2141 its arguments as a wrapper. Several standard Unix utilities do
2142 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2143 with @code{exec "$@@"} will also work.
2145 For example, you can use @code{env} to pass an environment variable to
2146 the debugged program, without setting the variable in your shell's
2150 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2154 This command is available when debugging locally on most targets, excluding
2155 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2157 @kindex set startup-with-shell
2158 @item set startup-with-shell
2159 @itemx set startup-with-shell on
2160 @itemx set startup-with-shell off
2161 @itemx show set startup-with-shell
2162 On Unix systems, by default, if a shell is available on your target,
2163 @value{GDBN}) uses it to start your program. Arguments of the
2164 @code{run} command are passed to the shell, which does variable
2165 substitution, expands wildcard characters and performs redirection of
2166 I/O. In some circumstances, it may be useful to disable such use of a
2167 shell, for example, when debugging the shell itself or diagnosing
2168 startup failures such as:
2172 Starting program: ./a.out
2173 During startup program terminated with signal SIGSEGV, Segmentation fault.
2177 which indicates the shell or the wrapper specified with
2178 @samp{exec-wrapper} crashed, not your program. Most often, this is
2179 caused by something odd in your shell's non-interactive mode
2180 initialization file---such as @file{.cshrc} for C-shell,
2181 $@file{.zshenv} for the Z shell, or the file specified in the
2182 @samp{BASH_ENV} environment variable for BASH.
2184 @anchor{set auto-connect-native-target}
2185 @kindex set auto-connect-native-target
2186 @item set auto-connect-native-target
2187 @itemx set auto-connect-native-target on
2188 @itemx set auto-connect-native-target off
2189 @itemx show auto-connect-native-target
2191 By default, if not connected to any target yet (e.g., with
2192 @code{target remote}), the @code{run} command starts your program as a
2193 native process under @value{GDBN}, on your local machine. If you're
2194 sure you don't want to debug programs on your local machine, you can
2195 tell @value{GDBN} to not connect to the native target automatically
2196 with the @code{set auto-connect-native-target off} command.
2198 If @code{on}, which is the default, and if @value{GDBN} is not
2199 connected to a target already, the @code{run} command automaticaly
2200 connects to the native target, if one is available.
2202 If @code{off}, and if @value{GDBN} is not connected to a target
2203 already, the @code{run} command fails with an error:
2207 Don't know how to run. Try "help target".
2210 If @value{GDBN} is already connected to a target, @value{GDBN} always
2211 uses it with the @code{run} command.
2213 In any case, you can explicitly connect to the native target with the
2214 @code{target native} command. For example,
2217 (@value{GDBP}) set auto-connect-native-target off
2219 Don't know how to run. Try "help target".
2220 (@value{GDBP}) target native
2222 Starting program: ./a.out
2223 [Inferior 1 (process 10421) exited normally]
2226 In case you connected explicitly to the @code{native} target,
2227 @value{GDBN} remains connected even if all inferiors exit, ready for
2228 the next @code{run} command. Use the @code{disconnect} command to
2231 Examples of other commands that likewise respect the
2232 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2233 proc}, @code{info os}.
2235 @kindex set disable-randomization
2236 @item set disable-randomization
2237 @itemx set disable-randomization on
2238 This option (enabled by default in @value{GDBN}) will turn off the native
2239 randomization of the virtual address space of the started program. This option
2240 is useful for multiple debugging sessions to make the execution better
2241 reproducible and memory addresses reusable across debugging sessions.
2243 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2244 On @sc{gnu}/Linux you can get the same behavior using
2247 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2250 @item set disable-randomization off
2251 Leave the behavior of the started executable unchanged. Some bugs rear their
2252 ugly heads only when the program is loaded at certain addresses. If your bug
2253 disappears when you run the program under @value{GDBN}, that might be because
2254 @value{GDBN} by default disables the address randomization on platforms, such
2255 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2256 disable-randomization off} to try to reproduce such elusive bugs.
2258 On targets where it is available, virtual address space randomization
2259 protects the programs against certain kinds of security attacks. In these
2260 cases the attacker needs to know the exact location of a concrete executable
2261 code. Randomizing its location makes it impossible to inject jumps misusing
2262 a code at its expected addresses.
2264 Prelinking shared libraries provides a startup performance advantage but it
2265 makes addresses in these libraries predictable for privileged processes by
2266 having just unprivileged access at the target system. Reading the shared
2267 library binary gives enough information for assembling the malicious code
2268 misusing it. Still even a prelinked shared library can get loaded at a new
2269 random address just requiring the regular relocation process during the
2270 startup. Shared libraries not already prelinked are always loaded at
2271 a randomly chosen address.
2273 Position independent executables (PIE) contain position independent code
2274 similar to the shared libraries and therefore such executables get loaded at
2275 a randomly chosen address upon startup. PIE executables always load even
2276 already prelinked shared libraries at a random address. You can build such
2277 executable using @command{gcc -fPIE -pie}.
2279 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2280 (as long as the randomization is enabled).
2282 @item show disable-randomization
2283 Show the current setting of the explicit disable of the native randomization of
2284 the virtual address space of the started program.
2289 @section Your Program's Arguments
2291 @cindex arguments (to your program)
2292 The arguments to your program can be specified by the arguments of the
2294 They are passed to a shell, which expands wildcard characters and
2295 performs redirection of I/O, and thence to your program. Your
2296 @code{SHELL} environment variable (if it exists) specifies what shell
2297 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2298 the default shell (@file{/bin/sh} on Unix).
2300 On non-Unix systems, the program is usually invoked directly by
2301 @value{GDBN}, which emulates I/O redirection via the appropriate system
2302 calls, and the wildcard characters are expanded by the startup code of
2303 the program, not by the shell.
2305 @code{run} with no arguments uses the same arguments used by the previous
2306 @code{run}, or those set by the @code{set args} command.
2311 Specify the arguments to be used the next time your program is run. If
2312 @code{set args} has no arguments, @code{run} executes your program
2313 with no arguments. Once you have run your program with arguments,
2314 using @code{set args} before the next @code{run} is the only way to run
2315 it again without arguments.
2319 Show the arguments to give your program when it is started.
2323 @section Your Program's Environment
2325 @cindex environment (of your program)
2326 The @dfn{environment} consists of a set of environment variables and
2327 their values. Environment variables conventionally record such things as
2328 your user name, your home directory, your terminal type, and your search
2329 path for programs to run. Usually you set up environment variables with
2330 the shell and they are inherited by all the other programs you run. When
2331 debugging, it can be useful to try running your program with a modified
2332 environment without having to start @value{GDBN} over again.
2336 @item path @var{directory}
2337 Add @var{directory} to the front of the @code{PATH} environment variable
2338 (the search path for executables) that will be passed to your program.
2339 The value of @code{PATH} used by @value{GDBN} does not change.
2340 You may specify several directory names, separated by whitespace or by a
2341 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2342 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2343 is moved to the front, so it is searched sooner.
2345 You can use the string @samp{$cwd} to refer to whatever is the current
2346 working directory at the time @value{GDBN} searches the path. If you
2347 use @samp{.} instead, it refers to the directory where you executed the
2348 @code{path} command. @value{GDBN} replaces @samp{.} in the
2349 @var{directory} argument (with the current path) before adding
2350 @var{directory} to the search path.
2351 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2352 @c document that, since repeating it would be a no-op.
2356 Display the list of search paths for executables (the @code{PATH}
2357 environment variable).
2359 @kindex show environment
2360 @item show environment @r{[}@var{varname}@r{]}
2361 Print the value of environment variable @var{varname} to be given to
2362 your program when it starts. If you do not supply @var{varname},
2363 print the names and values of all environment variables to be given to
2364 your program. You can abbreviate @code{environment} as @code{env}.
2366 @kindex set environment
2367 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2368 Set environment variable @var{varname} to @var{value}. The value
2369 changes for your program (and the shell @value{GDBN} uses to launch
2370 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2371 values of environment variables are just strings, and any
2372 interpretation is supplied by your program itself. The @var{value}
2373 parameter is optional; if it is eliminated, the variable is set to a
2375 @c "any string" here does not include leading, trailing
2376 @c blanks. Gnu asks: does anyone care?
2378 For example, this command:
2385 tells the debugged program, when subsequently run, that its user is named
2386 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2387 are not actually required.)
2389 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2390 which also inherits the environment set with @code{set environment}.
2391 If necessary, you can avoid that by using the @samp{env} program as a
2392 wrapper instead of using @code{set environment}. @xref{set
2393 exec-wrapper}, for an example doing just that.
2395 @kindex unset environment
2396 @item unset environment @var{varname}
2397 Remove variable @var{varname} from the environment to be passed to your
2398 program. This is different from @samp{set env @var{varname} =};
2399 @code{unset environment} removes the variable from the environment,
2400 rather than assigning it an empty value.
2403 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2404 the shell indicated by your @code{SHELL} environment variable if it
2405 exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
2406 names a shell that runs an initialization file when started
2407 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2408 for the Z shell, or the file specified in the @samp{BASH_ENV}
2409 environment variable for BASH---any variables you set in that file
2410 affect your program. You may wish to move setting of environment
2411 variables to files that are only run when you sign on, such as
2412 @file{.login} or @file{.profile}.
2414 @node Working Directory
2415 @section Your Program's Working Directory
2417 @cindex working directory (of your program)
2418 Each time you start your program with @code{run}, it inherits its
2419 working directory from the current working directory of @value{GDBN}.
2420 The @value{GDBN} working directory is initially whatever it inherited
2421 from its parent process (typically the shell), but you can specify a new
2422 working directory in @value{GDBN} with the @code{cd} command.
2424 The @value{GDBN} working directory also serves as a default for the commands
2425 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2430 @cindex change working directory
2431 @item cd @r{[}@var{directory}@r{]}
2432 Set the @value{GDBN} working directory to @var{directory}. If not
2433 given, @var{directory} uses @file{'~'}.
2437 Print the @value{GDBN} working directory.
2440 It is generally impossible to find the current working directory of
2441 the process being debugged (since a program can change its directory
2442 during its run). If you work on a system where @value{GDBN} is
2443 configured with the @file{/proc} support, you can use the @code{info
2444 proc} command (@pxref{SVR4 Process Information}) to find out the
2445 current working directory of the debuggee.
2448 @section Your Program's Input and Output
2453 By default, the program you run under @value{GDBN} does input and output to
2454 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2455 to its own terminal modes to interact with you, but it records the terminal
2456 modes your program was using and switches back to them when you continue
2457 running your program.
2460 @kindex info terminal
2462 Displays information recorded by @value{GDBN} about the terminal modes your
2466 You can redirect your program's input and/or output using shell
2467 redirection with the @code{run} command. For example,
2474 starts your program, diverting its output to the file @file{outfile}.
2477 @cindex controlling terminal
2478 Another way to specify where your program should do input and output is
2479 with the @code{tty} command. This command accepts a file name as
2480 argument, and causes this file to be the default for future @code{run}
2481 commands. It also resets the controlling terminal for the child
2482 process, for future @code{run} commands. For example,
2489 directs that processes started with subsequent @code{run} commands
2490 default to do input and output on the terminal @file{/dev/ttyb} and have
2491 that as their controlling terminal.
2493 An explicit redirection in @code{run} overrides the @code{tty} command's
2494 effect on the input/output device, but not its effect on the controlling
2497 When you use the @code{tty} command or redirect input in the @code{run}
2498 command, only the input @emph{for your program} is affected. The input
2499 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2500 for @code{set inferior-tty}.
2502 @cindex inferior tty
2503 @cindex set inferior controlling terminal
2504 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2505 display the name of the terminal that will be used for future runs of your
2509 @item set inferior-tty /dev/ttyb
2510 @kindex set inferior-tty
2511 Set the tty for the program being debugged to /dev/ttyb.
2513 @item show inferior-tty
2514 @kindex show inferior-tty
2515 Show the current tty for the program being debugged.
2519 @section Debugging an Already-running Process
2524 @item attach @var{process-id}
2525 This command attaches to a running process---one that was started
2526 outside @value{GDBN}. (@code{info files} shows your active
2527 targets.) The command takes as argument a process ID. The usual way to
2528 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2529 or with the @samp{jobs -l} shell command.
2531 @code{attach} does not repeat if you press @key{RET} a second time after
2532 executing the command.
2535 To use @code{attach}, your program must be running in an environment
2536 which supports processes; for example, @code{attach} does not work for
2537 programs on bare-board targets that lack an operating system. You must
2538 also have permission to send the process a signal.
2540 When you use @code{attach}, the debugger finds the program running in
2541 the process first by looking in the current working directory, then (if
2542 the program is not found) by using the source file search path
2543 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2544 the @code{file} command to load the program. @xref{Files, ,Commands to
2547 The first thing @value{GDBN} does after arranging to debug the specified
2548 process is to stop it. You can examine and modify an attached process
2549 with all the @value{GDBN} commands that are ordinarily available when
2550 you start processes with @code{run}. You can insert breakpoints; you
2551 can step and continue; you can modify storage. If you would rather the
2552 process continue running, you may use the @code{continue} command after
2553 attaching @value{GDBN} to the process.
2558 When you have finished debugging the attached process, you can use the
2559 @code{detach} command to release it from @value{GDBN} control. Detaching
2560 the process continues its execution. After the @code{detach} command,
2561 that process and @value{GDBN} become completely independent once more, and you
2562 are ready to @code{attach} another process or start one with @code{run}.
2563 @code{detach} does not repeat if you press @key{RET} again after
2564 executing the command.
2567 If you exit @value{GDBN} while you have an attached process, you detach
2568 that process. If you use the @code{run} command, you kill that process.
2569 By default, @value{GDBN} asks for confirmation if you try to do either of these
2570 things; you can control whether or not you need to confirm by using the
2571 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2575 @section Killing the Child Process
2580 Kill the child process in which your program is running under @value{GDBN}.
2583 This command is useful if you wish to debug a core dump instead of a
2584 running process. @value{GDBN} ignores any core dump file while your program
2587 On some operating systems, a program cannot be executed outside @value{GDBN}
2588 while you have breakpoints set on it inside @value{GDBN}. You can use the
2589 @code{kill} command in this situation to permit running your program
2590 outside the debugger.
2592 The @code{kill} command is also useful if you wish to recompile and
2593 relink your program, since on many systems it is impossible to modify an
2594 executable file while it is running in a process. In this case, when you
2595 next type @code{run}, @value{GDBN} notices that the file has changed, and
2596 reads the symbol table again (while trying to preserve your current
2597 breakpoint settings).
2599 @node Inferiors and Programs
2600 @section Debugging Multiple Inferiors and Programs
2602 @value{GDBN} lets you run and debug multiple programs in a single
2603 session. In addition, @value{GDBN} on some systems may let you run
2604 several programs simultaneously (otherwise you have to exit from one
2605 before starting another). In the most general case, you can have
2606 multiple threads of execution in each of multiple processes, launched
2607 from multiple executables.
2610 @value{GDBN} represents the state of each program execution with an
2611 object called an @dfn{inferior}. An inferior typically corresponds to
2612 a process, but is more general and applies also to targets that do not
2613 have processes. Inferiors may be created before a process runs, and
2614 may be retained after a process exits. Inferiors have unique
2615 identifiers that are different from process ids. Usually each
2616 inferior will also have its own distinct address space, although some
2617 embedded targets may have several inferiors running in different parts
2618 of a single address space. Each inferior may in turn have multiple
2619 threads running in it.
2621 To find out what inferiors exist at any moment, use @w{@code{info
2625 @kindex info inferiors
2626 @item info inferiors
2627 Print a list of all inferiors currently being managed by @value{GDBN}.
2629 @value{GDBN} displays for each inferior (in this order):
2633 the inferior number assigned by @value{GDBN}
2636 the target system's inferior identifier
2639 the name of the executable the inferior is running.
2644 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2645 indicates the current inferior.
2649 @c end table here to get a little more width for example
2652 (@value{GDBP}) info inferiors
2653 Num Description Executable
2654 2 process 2307 hello
2655 * 1 process 3401 goodbye
2658 To switch focus between inferiors, use the @code{inferior} command:
2661 @kindex inferior @var{infno}
2662 @item inferior @var{infno}
2663 Make inferior number @var{infno} the current inferior. The argument
2664 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2665 in the first field of the @samp{info inferiors} display.
2669 You can get multiple executables into a debugging session via the
2670 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2671 systems @value{GDBN} can add inferiors to the debug session
2672 automatically by following calls to @code{fork} and @code{exec}. To
2673 remove inferiors from the debugging session use the
2674 @w{@code{remove-inferiors}} command.
2677 @kindex add-inferior
2678 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2679 Adds @var{n} inferiors to be run using @var{executable} as the
2680 executable; @var{n} defaults to 1. If no executable is specified,
2681 the inferiors begins empty, with no program. You can still assign or
2682 change the program assigned to the inferior at any time by using the
2683 @code{file} command with the executable name as its argument.
2685 @kindex clone-inferior
2686 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2687 Adds @var{n} inferiors ready to execute the same program as inferior
2688 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
2689 number of the current inferior. This is a convenient command when you
2690 want to run another instance of the inferior you are debugging.
2693 (@value{GDBP}) info inferiors
2694 Num Description Executable
2695 * 1 process 29964 helloworld
2696 (@value{GDBP}) clone-inferior
2699 (@value{GDBP}) info inferiors
2700 Num Description Executable
2702 * 1 process 29964 helloworld
2705 You can now simply switch focus to inferior 2 and run it.
2707 @kindex remove-inferiors
2708 @item remove-inferiors @var{infno}@dots{}
2709 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2710 possible to remove an inferior that is running with this command. For
2711 those, use the @code{kill} or @code{detach} command first.
2715 To quit debugging one of the running inferiors that is not the current
2716 inferior, you can either detach from it by using the @w{@code{detach
2717 inferior}} command (allowing it to run independently), or kill it
2718 using the @w{@code{kill inferiors}} command:
2721 @kindex detach inferiors @var{infno}@dots{}
2722 @item detach inferior @var{infno}@dots{}
2723 Detach from the inferior or inferiors identified by @value{GDBN}
2724 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2725 still stays on the list of inferiors shown by @code{info inferiors},
2726 but its Description will show @samp{<null>}.
2728 @kindex kill inferiors @var{infno}@dots{}
2729 @item kill inferiors @var{infno}@dots{}
2730 Kill the inferior or inferiors identified by @value{GDBN} inferior
2731 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2732 stays on the list of inferiors shown by @code{info inferiors}, but its
2733 Description will show @samp{<null>}.
2736 After the successful completion of a command such as @code{detach},
2737 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2738 a normal process exit, the inferior is still valid and listed with
2739 @code{info inferiors}, ready to be restarted.
2742 To be notified when inferiors are started or exit under @value{GDBN}'s
2743 control use @w{@code{set print inferior-events}}:
2746 @kindex set print inferior-events
2747 @cindex print messages on inferior start and exit
2748 @item set print inferior-events
2749 @itemx set print inferior-events on
2750 @itemx set print inferior-events off
2751 The @code{set print inferior-events} command allows you to enable or
2752 disable printing of messages when @value{GDBN} notices that new
2753 inferiors have started or that inferiors have exited or have been
2754 detached. By default, these messages will not be printed.
2756 @kindex show print inferior-events
2757 @item show print inferior-events
2758 Show whether messages will be printed when @value{GDBN} detects that
2759 inferiors have started, exited or have been detached.
2762 Many commands will work the same with multiple programs as with a
2763 single program: e.g., @code{print myglobal} will simply display the
2764 value of @code{myglobal} in the current inferior.
2767 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2768 get more info about the relationship of inferiors, programs, address
2769 spaces in a debug session. You can do that with the @w{@code{maint
2770 info program-spaces}} command.
2773 @kindex maint info program-spaces
2774 @item maint info program-spaces
2775 Print a list of all program spaces currently being managed by
2778 @value{GDBN} displays for each program space (in this order):
2782 the program space number assigned by @value{GDBN}
2785 the name of the executable loaded into the program space, with e.g.,
2786 the @code{file} command.
2791 An asterisk @samp{*} preceding the @value{GDBN} program space number
2792 indicates the current program space.
2794 In addition, below each program space line, @value{GDBN} prints extra
2795 information that isn't suitable to display in tabular form. For
2796 example, the list of inferiors bound to the program space.
2799 (@value{GDBP}) maint info program-spaces
2802 Bound inferiors: ID 1 (process 21561)
2806 Here we can see that no inferior is running the program @code{hello},
2807 while @code{process 21561} is running the program @code{goodbye}. On
2808 some targets, it is possible that multiple inferiors are bound to the
2809 same program space. The most common example is that of debugging both
2810 the parent and child processes of a @code{vfork} call. For example,
2813 (@value{GDBP}) maint info program-spaces
2816 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2819 Here, both inferior 2 and inferior 1 are running in the same program
2820 space as a result of inferior 1 having executed a @code{vfork} call.
2824 @section Debugging Programs with Multiple Threads
2826 @cindex threads of execution
2827 @cindex multiple threads
2828 @cindex switching threads
2829 In some operating systems, such as HP-UX and Solaris, a single program
2830 may have more than one @dfn{thread} of execution. The precise semantics
2831 of threads differ from one operating system to another, but in general
2832 the threads of a single program are akin to multiple processes---except
2833 that they share one address space (that is, they can all examine and
2834 modify the same variables). On the other hand, each thread has its own
2835 registers and execution stack, and perhaps private memory.
2837 @value{GDBN} provides these facilities for debugging multi-thread
2841 @item automatic notification of new threads
2842 @item @samp{thread @var{threadno}}, a command to switch among threads
2843 @item @samp{info threads}, a command to inquire about existing threads
2844 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2845 a command to apply a command to a list of threads
2846 @item thread-specific breakpoints
2847 @item @samp{set print thread-events}, which controls printing of
2848 messages on thread start and exit.
2849 @item @samp{set libthread-db-search-path @var{path}}, which lets
2850 the user specify which @code{libthread_db} to use if the default choice
2851 isn't compatible with the program.
2855 @emph{Warning:} These facilities are not yet available on every
2856 @value{GDBN} configuration where the operating system supports threads.
2857 If your @value{GDBN} does not support threads, these commands have no
2858 effect. For example, a system without thread support shows no output
2859 from @samp{info threads}, and always rejects the @code{thread} command,
2863 (@value{GDBP}) info threads
2864 (@value{GDBP}) thread 1
2865 Thread ID 1 not known. Use the "info threads" command to
2866 see the IDs of currently known threads.
2868 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2869 @c doesn't support threads"?
2872 @cindex focus of debugging
2873 @cindex current thread
2874 The @value{GDBN} thread debugging facility allows you to observe all
2875 threads while your program runs---but whenever @value{GDBN} takes
2876 control, one thread in particular is always the focus of debugging.
2877 This thread is called the @dfn{current thread}. Debugging commands show
2878 program information from the perspective of the current thread.
2880 @cindex @code{New} @var{systag} message
2881 @cindex thread identifier (system)
2882 @c FIXME-implementors!! It would be more helpful if the [New...] message
2883 @c included GDB's numeric thread handle, so you could just go to that
2884 @c thread without first checking `info threads'.
2885 Whenever @value{GDBN} detects a new thread in your program, it displays
2886 the target system's identification for the thread with a message in the
2887 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
2888 whose form varies depending on the particular system. For example, on
2889 @sc{gnu}/Linux, you might see
2892 [New Thread 0x41e02940 (LWP 25582)]
2896 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2897 the @var{systag} is simply something like @samp{process 368}, with no
2900 @c FIXME!! (1) Does the [New...] message appear even for the very first
2901 @c thread of a program, or does it only appear for the
2902 @c second---i.e.@: when it becomes obvious we have a multithread
2904 @c (2) *Is* there necessarily a first thread always? Or do some
2905 @c multithread systems permit starting a program with multiple
2906 @c threads ab initio?
2908 @cindex thread number
2909 @cindex thread identifier (GDB)
2910 For debugging purposes, @value{GDBN} associates its own thread
2911 number---always a single integer---with each thread in your program.
2914 @kindex info threads
2915 @item info threads @r{[}@var{id}@dots{}@r{]}
2916 Display a summary of all threads currently in your program. Optional
2917 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2918 means to print information only about the specified thread or threads.
2919 @value{GDBN} displays for each thread (in this order):
2923 the thread number assigned by @value{GDBN}
2926 the target system's thread identifier (@var{systag})
2929 the thread's name, if one is known. A thread can either be named by
2930 the user (see @code{thread name}, below), or, in some cases, by the
2934 the current stack frame summary for that thread
2938 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2939 indicates the current thread.
2943 @c end table here to get a little more width for example
2946 (@value{GDBP}) info threads
2948 3 process 35 thread 27 0x34e5 in sigpause ()
2949 2 process 35 thread 23 0x34e5 in sigpause ()
2950 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2954 On Solaris, you can display more information about user threads with a
2955 Solaris-specific command:
2958 @item maint info sol-threads
2959 @kindex maint info sol-threads
2960 @cindex thread info (Solaris)
2961 Display info on Solaris user threads.
2965 @kindex thread @var{threadno}
2966 @item thread @var{threadno}
2967 Make thread number @var{threadno} the current thread. The command
2968 argument @var{threadno} is the internal @value{GDBN} thread number, as
2969 shown in the first field of the @samp{info threads} display.
2970 @value{GDBN} responds by displaying the system identifier of the thread
2971 you selected, and its current stack frame summary:
2974 (@value{GDBP}) thread 2
2975 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2976 #0 some_function (ignore=0x0) at example.c:8
2977 8 printf ("hello\n");
2981 As with the @samp{[New @dots{}]} message, the form of the text after
2982 @samp{Switching to} depends on your system's conventions for identifying
2985 @vindex $_thread@r{, convenience variable}
2986 The debugger convenience variable @samp{$_thread} contains the number
2987 of the current thread. You may find this useful in writing breakpoint
2988 conditional expressions, command scripts, and so forth. See
2989 @xref{Convenience Vars,, Convenience Variables}, for general
2990 information on convenience variables.
2992 @kindex thread apply
2993 @cindex apply command to several threads
2994 @item thread apply [@var{threadno} | all [-ascending]] @var{command}
2995 The @code{thread apply} command allows you to apply the named
2996 @var{command} to one or more threads. Specify the numbers of the
2997 threads that you want affected with the command argument
2998 @var{threadno}. It can be a single thread number, one of the numbers
2999 shown in the first field of the @samp{info threads} display; or it
3000 could be a range of thread numbers, as in @code{2-4}. To apply
3001 a command to all threads in descending order, type @kbd{thread apply all
3002 @var{command}}. To apply a command to all threads in ascending order,
3003 type @kbd{thread apply all -ascending @var{command}}.
3007 @cindex name a thread
3008 @item thread name [@var{name}]
3009 This command assigns a name to the current thread. If no argument is
3010 given, any existing user-specified name is removed. The thread name
3011 appears in the @samp{info threads} display.
3013 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3014 determine the name of the thread as given by the OS. On these
3015 systems, a name specified with @samp{thread name} will override the
3016 system-give name, and removing the user-specified name will cause
3017 @value{GDBN} to once again display the system-specified name.
3020 @cindex search for a thread
3021 @item thread find [@var{regexp}]
3022 Search for and display thread ids whose name or @var{systag}
3023 matches the supplied regular expression.
3025 As well as being the complement to the @samp{thread name} command,
3026 this command also allows you to identify a thread by its target
3027 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3031 (@value{GDBN}) thread find 26688
3032 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3033 (@value{GDBN}) info thread 4
3035 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3038 @kindex set print thread-events
3039 @cindex print messages on thread start and exit
3040 @item set print thread-events
3041 @itemx set print thread-events on
3042 @itemx set print thread-events off
3043 The @code{set print thread-events} command allows you to enable or
3044 disable printing of messages when @value{GDBN} notices that new threads have
3045 started or that threads have exited. By default, these messages will
3046 be printed if detection of these events is supported by the target.
3047 Note that these messages cannot be disabled on all targets.
3049 @kindex show print thread-events
3050 @item show print thread-events
3051 Show whether messages will be printed when @value{GDBN} detects that threads
3052 have started and exited.
3055 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3056 more information about how @value{GDBN} behaves when you stop and start
3057 programs with multiple threads.
3059 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3060 watchpoints in programs with multiple threads.
3062 @anchor{set libthread-db-search-path}
3064 @kindex set libthread-db-search-path
3065 @cindex search path for @code{libthread_db}
3066 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3067 If this variable is set, @var{path} is a colon-separated list of
3068 directories @value{GDBN} will use to search for @code{libthread_db}.
3069 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3070 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3071 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3074 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3075 @code{libthread_db} library to obtain information about threads in the
3076 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3077 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3078 specific thread debugging library loading is enabled
3079 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3081 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3082 refers to the default system directories that are
3083 normally searched for loading shared libraries. The @samp{$sdir} entry
3084 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3085 (@pxref{libthread_db.so.1 file}).
3087 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3088 refers to the directory from which @code{libpthread}
3089 was loaded in the inferior process.
3091 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3092 @value{GDBN} attempts to initialize it with the current inferior process.
3093 If this initialization fails (which could happen because of a version
3094 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3095 will unload @code{libthread_db}, and continue with the next directory.
3096 If none of @code{libthread_db} libraries initialize successfully,
3097 @value{GDBN} will issue a warning and thread debugging will be disabled.
3099 Setting @code{libthread-db-search-path} is currently implemented
3100 only on some platforms.
3102 @kindex show libthread-db-search-path
3103 @item show libthread-db-search-path
3104 Display current libthread_db search path.
3106 @kindex set debug libthread-db
3107 @kindex show debug libthread-db
3108 @cindex debugging @code{libthread_db}
3109 @item set debug libthread-db
3110 @itemx show debug libthread-db
3111 Turns on or off display of @code{libthread_db}-related events.
3112 Use @code{1} to enable, @code{0} to disable.
3116 @section Debugging Forks
3118 @cindex fork, debugging programs which call
3119 @cindex multiple processes
3120 @cindex processes, multiple
3121 On most systems, @value{GDBN} has no special support for debugging
3122 programs which create additional processes using the @code{fork}
3123 function. When a program forks, @value{GDBN} will continue to debug the
3124 parent process and the child process will run unimpeded. If you have
3125 set a breakpoint in any code which the child then executes, the child
3126 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3127 will cause it to terminate.
3129 However, if you want to debug the child process there is a workaround
3130 which isn't too painful. Put a call to @code{sleep} in the code which
3131 the child process executes after the fork. It may be useful to sleep
3132 only if a certain environment variable is set, or a certain file exists,
3133 so that the delay need not occur when you don't want to run @value{GDBN}
3134 on the child. While the child is sleeping, use the @code{ps} program to
3135 get its process ID. Then tell @value{GDBN} (a new invocation of
3136 @value{GDBN} if you are also debugging the parent process) to attach to
3137 the child process (@pxref{Attach}). From that point on you can debug
3138 the child process just like any other process which you attached to.
3140 On some systems, @value{GDBN} provides support for debugging programs that
3141 create additional processes using the @code{fork} or @code{vfork} functions.
3142 Currently, the only platforms with this feature are HP-UX (11.x and later
3143 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
3145 By default, when a program forks, @value{GDBN} will continue to debug
3146 the parent process and the child process will run unimpeded.
3148 If you want to follow the child process instead of the parent process,
3149 use the command @w{@code{set follow-fork-mode}}.
3152 @kindex set follow-fork-mode
3153 @item set follow-fork-mode @var{mode}
3154 Set the debugger response to a program call of @code{fork} or
3155 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3156 process. The @var{mode} argument can be:
3160 The original process is debugged after a fork. The child process runs
3161 unimpeded. This is the default.
3164 The new process is debugged after a fork. The parent process runs
3169 @kindex show follow-fork-mode
3170 @item show follow-fork-mode
3171 Display the current debugger response to a @code{fork} or @code{vfork} call.
3174 @cindex debugging multiple processes
3175 On Linux, if you want to debug both the parent and child processes, use the
3176 command @w{@code{set detach-on-fork}}.
3179 @kindex set detach-on-fork
3180 @item set detach-on-fork @var{mode}
3181 Tells gdb whether to detach one of the processes after a fork, or
3182 retain debugger control over them both.
3186 The child process (or parent process, depending on the value of
3187 @code{follow-fork-mode}) will be detached and allowed to run
3188 independently. This is the default.
3191 Both processes will be held under the control of @value{GDBN}.
3192 One process (child or parent, depending on the value of
3193 @code{follow-fork-mode}) is debugged as usual, while the other
3198 @kindex show detach-on-fork
3199 @item show detach-on-fork
3200 Show whether detach-on-fork mode is on/off.
3203 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3204 will retain control of all forked processes (including nested forks).
3205 You can list the forked processes under the control of @value{GDBN} by
3206 using the @w{@code{info inferiors}} command, and switch from one fork
3207 to another by using the @code{inferior} command (@pxref{Inferiors and
3208 Programs, ,Debugging Multiple Inferiors and Programs}).
3210 To quit debugging one of the forked processes, you can either detach
3211 from it by using the @w{@code{detach inferiors}} command (allowing it
3212 to run independently), or kill it using the @w{@code{kill inferiors}}
3213 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3216 If you ask to debug a child process and a @code{vfork} is followed by an
3217 @code{exec}, @value{GDBN} executes the new target up to the first
3218 breakpoint in the new target. If you have a breakpoint set on
3219 @code{main} in your original program, the breakpoint will also be set on
3220 the child process's @code{main}.
3222 On some systems, when a child process is spawned by @code{vfork}, you
3223 cannot debug the child or parent until an @code{exec} call completes.
3225 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3226 call executes, the new target restarts. To restart the parent
3227 process, use the @code{file} command with the parent executable name
3228 as its argument. By default, after an @code{exec} call executes,
3229 @value{GDBN} discards the symbols of the previous executable image.
3230 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3234 @kindex set follow-exec-mode
3235 @item set follow-exec-mode @var{mode}
3237 Set debugger response to a program call of @code{exec}. An
3238 @code{exec} call replaces the program image of a process.
3240 @code{follow-exec-mode} can be:
3244 @value{GDBN} creates a new inferior and rebinds the process to this
3245 new inferior. The program the process was running before the
3246 @code{exec} call can be restarted afterwards by restarting the
3252 (@value{GDBP}) info inferiors
3254 Id Description Executable
3257 process 12020 is executing new program: prog2
3258 Program exited normally.
3259 (@value{GDBP}) info inferiors
3260 Id Description Executable
3266 @value{GDBN} keeps the process bound to the same inferior. The new
3267 executable image replaces the previous executable loaded in the
3268 inferior. Restarting the inferior after the @code{exec} call, with
3269 e.g., the @code{run} command, restarts the executable the process was
3270 running after the @code{exec} call. This is the default mode.
3275 (@value{GDBP}) info inferiors
3276 Id Description Executable
3279 process 12020 is executing new program: prog2
3280 Program exited normally.
3281 (@value{GDBP}) info inferiors
3282 Id Description Executable
3289 You can use the @code{catch} command to make @value{GDBN} stop whenever
3290 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3291 Catchpoints, ,Setting Catchpoints}.
3293 @node Checkpoint/Restart
3294 @section Setting a @emph{Bookmark} to Return to Later
3299 @cindex snapshot of a process
3300 @cindex rewind program state
3302 On certain operating systems@footnote{Currently, only
3303 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3304 program's state, called a @dfn{checkpoint}, and come back to it
3307 Returning to a checkpoint effectively undoes everything that has
3308 happened in the program since the @code{checkpoint} was saved. This
3309 includes changes in memory, registers, and even (within some limits)
3310 system state. Effectively, it is like going back in time to the
3311 moment when the checkpoint was saved.
3313 Thus, if you're stepping thru a program and you think you're
3314 getting close to the point where things go wrong, you can save
3315 a checkpoint. Then, if you accidentally go too far and miss
3316 the critical statement, instead of having to restart your program
3317 from the beginning, you can just go back to the checkpoint and
3318 start again from there.
3320 This can be especially useful if it takes a lot of time or
3321 steps to reach the point where you think the bug occurs.
3323 To use the @code{checkpoint}/@code{restart} method of debugging:
3328 Save a snapshot of the debugged program's current execution state.
3329 The @code{checkpoint} command takes no arguments, but each checkpoint
3330 is assigned a small integer id, similar to a breakpoint id.
3332 @kindex info checkpoints
3333 @item info checkpoints
3334 List the checkpoints that have been saved in the current debugging
3335 session. For each checkpoint, the following information will be
3342 @item Source line, or label
3345 @kindex restart @var{checkpoint-id}
3346 @item restart @var{checkpoint-id}
3347 Restore the program state that was saved as checkpoint number
3348 @var{checkpoint-id}. All program variables, registers, stack frames
3349 etc.@: will be returned to the values that they had when the checkpoint
3350 was saved. In essence, gdb will ``wind back the clock'' to the point
3351 in time when the checkpoint was saved.
3353 Note that breakpoints, @value{GDBN} variables, command history etc.
3354 are not affected by restoring a checkpoint. In general, a checkpoint
3355 only restores things that reside in the program being debugged, not in
3358 @kindex delete checkpoint @var{checkpoint-id}
3359 @item delete checkpoint @var{checkpoint-id}
3360 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3364 Returning to a previously saved checkpoint will restore the user state
3365 of the program being debugged, plus a significant subset of the system
3366 (OS) state, including file pointers. It won't ``un-write'' data from
3367 a file, but it will rewind the file pointer to the previous location,
3368 so that the previously written data can be overwritten. For files
3369 opened in read mode, the pointer will also be restored so that the
3370 previously read data can be read again.
3372 Of course, characters that have been sent to a printer (or other
3373 external device) cannot be ``snatched back'', and characters received
3374 from eg.@: a serial device can be removed from internal program buffers,
3375 but they cannot be ``pushed back'' into the serial pipeline, ready to
3376 be received again. Similarly, the actual contents of files that have
3377 been changed cannot be restored (at this time).
3379 However, within those constraints, you actually can ``rewind'' your
3380 program to a previously saved point in time, and begin debugging it
3381 again --- and you can change the course of events so as to debug a
3382 different execution path this time.
3384 @cindex checkpoints and process id
3385 Finally, there is one bit of internal program state that will be
3386 different when you return to a checkpoint --- the program's process
3387 id. Each checkpoint will have a unique process id (or @var{pid}),
3388 and each will be different from the program's original @var{pid}.
3389 If your program has saved a local copy of its process id, this could
3390 potentially pose a problem.
3392 @subsection A Non-obvious Benefit of Using Checkpoints
3394 On some systems such as @sc{gnu}/Linux, address space randomization
3395 is performed on new processes for security reasons. This makes it
3396 difficult or impossible to set a breakpoint, or watchpoint, on an
3397 absolute address if you have to restart the program, since the
3398 absolute location of a symbol will change from one execution to the
3401 A checkpoint, however, is an @emph{identical} copy of a process.
3402 Therefore if you create a checkpoint at (eg.@:) the start of main,
3403 and simply return to that checkpoint instead of restarting the
3404 process, you can avoid the effects of address randomization and
3405 your symbols will all stay in the same place.
3408 @chapter Stopping and Continuing
3410 The principal purposes of using a debugger are so that you can stop your
3411 program before it terminates; or so that, if your program runs into
3412 trouble, you can investigate and find out why.
3414 Inside @value{GDBN}, your program may stop for any of several reasons,
3415 such as a signal, a breakpoint, or reaching a new line after a
3416 @value{GDBN} command such as @code{step}. You may then examine and
3417 change variables, set new breakpoints or remove old ones, and then
3418 continue execution. Usually, the messages shown by @value{GDBN} provide
3419 ample explanation of the status of your program---but you can also
3420 explicitly request this information at any time.
3423 @kindex info program
3425 Display information about the status of your program: whether it is
3426 running or not, what process it is, and why it stopped.
3430 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3431 * Continuing and Stepping:: Resuming execution
3432 * Skipping Over Functions and Files::
3433 Skipping over functions and files
3435 * Thread Stops:: Stopping and starting multi-thread programs
3439 @section Breakpoints, Watchpoints, and Catchpoints
3442 A @dfn{breakpoint} makes your program stop whenever a certain point in
3443 the program is reached. For each breakpoint, you can add conditions to
3444 control in finer detail whether your program stops. You can set
3445 breakpoints with the @code{break} command and its variants (@pxref{Set
3446 Breaks, ,Setting Breakpoints}), to specify the place where your program
3447 should stop by line number, function name or exact address in the
3450 On some systems, you can set breakpoints in shared libraries before
3451 the executable is run. There is a minor limitation on HP-UX systems:
3452 you must wait until the executable is run in order to set breakpoints
3453 in shared library routines that are not called directly by the program
3454 (for example, routines that are arguments in a @code{pthread_create}
3458 @cindex data breakpoints
3459 @cindex memory tracing
3460 @cindex breakpoint on memory address
3461 @cindex breakpoint on variable modification
3462 A @dfn{watchpoint} is a special breakpoint that stops your program
3463 when the value of an expression changes. The expression may be a value
3464 of a variable, or it could involve values of one or more variables
3465 combined by operators, such as @samp{a + b}. This is sometimes called
3466 @dfn{data breakpoints}. You must use a different command to set
3467 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3468 from that, you can manage a watchpoint like any other breakpoint: you
3469 enable, disable, and delete both breakpoints and watchpoints using the
3472 You can arrange to have values from your program displayed automatically
3473 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3477 @cindex breakpoint on events
3478 A @dfn{catchpoint} is another special breakpoint that stops your program
3479 when a certain kind of event occurs, such as the throwing of a C@t{++}
3480 exception or the loading of a library. As with watchpoints, you use a
3481 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3482 Catchpoints}), but aside from that, you can manage a catchpoint like any
3483 other breakpoint. (To stop when your program receives a signal, use the
3484 @code{handle} command; see @ref{Signals, ,Signals}.)
3486 @cindex breakpoint numbers
3487 @cindex numbers for breakpoints
3488 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3489 catchpoint when you create it; these numbers are successive integers
3490 starting with one. In many of the commands for controlling various
3491 features of breakpoints you use the breakpoint number to say which
3492 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3493 @dfn{disabled}; if disabled, it has no effect on your program until you
3496 @cindex breakpoint ranges
3497 @cindex ranges of breakpoints
3498 Some @value{GDBN} commands accept a range of breakpoints on which to
3499 operate. A breakpoint range is either a single breakpoint number, like
3500 @samp{5}, or two such numbers, in increasing order, separated by a
3501 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3502 all breakpoints in that range are operated on.
3505 * Set Breaks:: Setting breakpoints
3506 * Set Watchpoints:: Setting watchpoints
3507 * Set Catchpoints:: Setting catchpoints
3508 * Delete Breaks:: Deleting breakpoints
3509 * Disabling:: Disabling breakpoints
3510 * Conditions:: Break conditions
3511 * Break Commands:: Breakpoint command lists
3512 * Dynamic Printf:: Dynamic printf
3513 * Save Breakpoints:: How to save breakpoints in a file
3514 * Static Probe Points:: Listing static probe points
3515 * Error in Breakpoints:: ``Cannot insert breakpoints''
3516 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3520 @subsection Setting Breakpoints
3522 @c FIXME LMB what does GDB do if no code on line of breakpt?
3523 @c consider in particular declaration with/without initialization.
3525 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3528 @kindex b @r{(@code{break})}
3529 @vindex $bpnum@r{, convenience variable}
3530 @cindex latest breakpoint
3531 Breakpoints are set with the @code{break} command (abbreviated
3532 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3533 number of the breakpoint you've set most recently; see @ref{Convenience
3534 Vars,, Convenience Variables}, for a discussion of what you can do with
3535 convenience variables.
3538 @item break @var{location}
3539 Set a breakpoint at the given @var{location}, which can specify a
3540 function name, a line number, or an address of an instruction.
3541 (@xref{Specify Location}, for a list of all the possible ways to
3542 specify a @var{location}.) The breakpoint will stop your program just
3543 before it executes any of the code in the specified @var{location}.
3545 When using source languages that permit overloading of symbols, such as
3546 C@t{++}, a function name may refer to more than one possible place to break.
3547 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3550 It is also possible to insert a breakpoint that will stop the program
3551 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3552 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3555 When called without any arguments, @code{break} sets a breakpoint at
3556 the next instruction to be executed in the selected stack frame
3557 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3558 innermost, this makes your program stop as soon as control
3559 returns to that frame. This is similar to the effect of a
3560 @code{finish} command in the frame inside the selected frame---except
3561 that @code{finish} does not leave an active breakpoint. If you use
3562 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3563 the next time it reaches the current location; this may be useful
3566 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3567 least one instruction has been executed. If it did not do this, you
3568 would be unable to proceed past a breakpoint without first disabling the
3569 breakpoint. This rule applies whether or not the breakpoint already
3570 existed when your program stopped.
3572 @item break @dots{} if @var{cond}
3573 Set a breakpoint with condition @var{cond}; evaluate the expression
3574 @var{cond} each time the breakpoint is reached, and stop only if the
3575 value is nonzero---that is, if @var{cond} evaluates as true.
3576 @samp{@dots{}} stands for one of the possible arguments described
3577 above (or no argument) specifying where to break. @xref{Conditions,
3578 ,Break Conditions}, for more information on breakpoint conditions.
3581 @item tbreak @var{args}
3582 Set a breakpoint enabled only for one stop. The @var{args} are the
3583 same as for the @code{break} command, and the breakpoint is set in the same
3584 way, but the breakpoint is automatically deleted after the first time your
3585 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3588 @cindex hardware breakpoints
3589 @item hbreak @var{args}
3590 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
3591 @code{break} command and the breakpoint is set in the same way, but the
3592 breakpoint requires hardware support and some target hardware may not
3593 have this support. The main purpose of this is EPROM/ROM code
3594 debugging, so you can set a breakpoint at an instruction without
3595 changing the instruction. This can be used with the new trap-generation
3596 provided by SPARClite DSU and most x86-based targets. These targets
3597 will generate traps when a program accesses some data or instruction
3598 address that is assigned to the debug registers. However the hardware
3599 breakpoint registers can take a limited number of breakpoints. For
3600 example, on the DSU, only two data breakpoints can be set at a time, and
3601 @value{GDBN} will reject this command if more than two are used. Delete
3602 or disable unused hardware breakpoints before setting new ones
3603 (@pxref{Disabling, ,Disabling Breakpoints}).
3604 @xref{Conditions, ,Break Conditions}.
3605 For remote targets, you can restrict the number of hardware
3606 breakpoints @value{GDBN} will use, see @ref{set remote
3607 hardware-breakpoint-limit}.
3610 @item thbreak @var{args}
3611 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
3612 are the same as for the @code{hbreak} command and the breakpoint is set in
3613 the same way. However, like the @code{tbreak} command,
3614 the breakpoint is automatically deleted after the
3615 first time your program stops there. Also, like the @code{hbreak}
3616 command, the breakpoint requires hardware support and some target hardware
3617 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3618 See also @ref{Conditions, ,Break Conditions}.
3621 @cindex regular expression
3622 @cindex breakpoints at functions matching a regexp
3623 @cindex set breakpoints in many functions
3624 @item rbreak @var{regex}
3625 Set breakpoints on all functions matching the regular expression
3626 @var{regex}. This command sets an unconditional breakpoint on all
3627 matches, printing a list of all breakpoints it set. Once these
3628 breakpoints are set, they are treated just like the breakpoints set with
3629 the @code{break} command. You can delete them, disable them, or make
3630 them conditional the same way as any other breakpoint.
3632 The syntax of the regular expression is the standard one used with tools
3633 like @file{grep}. Note that this is different from the syntax used by
3634 shells, so for instance @code{foo*} matches all functions that include
3635 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3636 @code{.*} leading and trailing the regular expression you supply, so to
3637 match only functions that begin with @code{foo}, use @code{^foo}.
3639 @cindex non-member C@t{++} functions, set breakpoint in
3640 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3641 breakpoints on overloaded functions that are not members of any special
3644 @cindex set breakpoints on all functions
3645 The @code{rbreak} command can be used to set breakpoints in
3646 @strong{all} the functions in a program, like this:
3649 (@value{GDBP}) rbreak .
3652 @item rbreak @var{file}:@var{regex}
3653 If @code{rbreak} is called with a filename qualification, it limits
3654 the search for functions matching the given regular expression to the
3655 specified @var{file}. This can be used, for example, to set breakpoints on
3656 every function in a given file:
3659 (@value{GDBP}) rbreak file.c:.
3662 The colon separating the filename qualifier from the regex may
3663 optionally be surrounded by spaces.
3665 @kindex info breakpoints
3666 @cindex @code{$_} and @code{info breakpoints}
3667 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3668 @itemx info break @r{[}@var{n}@dots{}@r{]}
3669 Print a table of all breakpoints, watchpoints, and catchpoints set and
3670 not deleted. Optional argument @var{n} means print information only
3671 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3672 For each breakpoint, following columns are printed:
3675 @item Breakpoint Numbers
3677 Breakpoint, watchpoint, or catchpoint.
3679 Whether the breakpoint is marked to be disabled or deleted when hit.
3680 @item Enabled or Disabled
3681 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3682 that are not enabled.
3684 Where the breakpoint is in your program, as a memory address. For a
3685 pending breakpoint whose address is not yet known, this field will
3686 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3687 library that has the symbol or line referred by breakpoint is loaded.
3688 See below for details. A breakpoint with several locations will
3689 have @samp{<MULTIPLE>} in this field---see below for details.
3691 Where the breakpoint is in the source for your program, as a file and
3692 line number. For a pending breakpoint, the original string passed to
3693 the breakpoint command will be listed as it cannot be resolved until
3694 the appropriate shared library is loaded in the future.
3698 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3699 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3700 @value{GDBN} on the host's side. If it is ``target'', then the condition
3701 is evaluated by the target. The @code{info break} command shows
3702 the condition on the line following the affected breakpoint, together with
3703 its condition evaluation mode in between parentheses.
3705 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3706 allowed to have a condition specified for it. The condition is not parsed for
3707 validity until a shared library is loaded that allows the pending
3708 breakpoint to resolve to a valid location.
3711 @code{info break} with a breakpoint
3712 number @var{n} as argument lists only that breakpoint. The
3713 convenience variable @code{$_} and the default examining-address for
3714 the @code{x} command are set to the address of the last breakpoint
3715 listed (@pxref{Memory, ,Examining Memory}).
3718 @code{info break} displays a count of the number of times the breakpoint
3719 has been hit. This is especially useful in conjunction with the
3720 @code{ignore} command. You can ignore a large number of breakpoint
3721 hits, look at the breakpoint info to see how many times the breakpoint
3722 was hit, and then run again, ignoring one less than that number. This
3723 will get you quickly to the last hit of that breakpoint.
3726 For a breakpoints with an enable count (xref) greater than 1,
3727 @code{info break} also displays that count.
3731 @value{GDBN} allows you to set any number of breakpoints at the same place in
3732 your program. There is nothing silly or meaningless about this. When
3733 the breakpoints are conditional, this is even useful
3734 (@pxref{Conditions, ,Break Conditions}).
3736 @cindex multiple locations, breakpoints
3737 @cindex breakpoints, multiple locations
3738 It is possible that a breakpoint corresponds to several locations
3739 in your program. Examples of this situation are:
3743 Multiple functions in the program may have the same name.
3746 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3747 instances of the function body, used in different cases.
3750 For a C@t{++} template function, a given line in the function can
3751 correspond to any number of instantiations.
3754 For an inlined function, a given source line can correspond to
3755 several places where that function is inlined.
3758 In all those cases, @value{GDBN} will insert a breakpoint at all
3759 the relevant locations.
3761 A breakpoint with multiple locations is displayed in the breakpoint
3762 table using several rows---one header row, followed by one row for
3763 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3764 address column. The rows for individual locations contain the actual
3765 addresses for locations, and show the functions to which those
3766 locations belong. The number column for a location is of the form
3767 @var{breakpoint-number}.@var{location-number}.
3772 Num Type Disp Enb Address What
3773 1 breakpoint keep y <MULTIPLE>
3775 breakpoint already hit 1 time
3776 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3777 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3780 Each location can be individually enabled or disabled by passing
3781 @var{breakpoint-number}.@var{location-number} as argument to the
3782 @code{enable} and @code{disable} commands. Note that you cannot
3783 delete the individual locations from the list, you can only delete the
3784 entire list of locations that belong to their parent breakpoint (with
3785 the @kbd{delete @var{num}} command, where @var{num} is the number of
3786 the parent breakpoint, 1 in the above example). Disabling or enabling
3787 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3788 that belong to that breakpoint.
3790 @cindex pending breakpoints
3791 It's quite common to have a breakpoint inside a shared library.
3792 Shared libraries can be loaded and unloaded explicitly,
3793 and possibly repeatedly, as the program is executed. To support
3794 this use case, @value{GDBN} updates breakpoint locations whenever
3795 any shared library is loaded or unloaded. Typically, you would
3796 set a breakpoint in a shared library at the beginning of your
3797 debugging session, when the library is not loaded, and when the
3798 symbols from the library are not available. When you try to set
3799 breakpoint, @value{GDBN} will ask you if you want to set
3800 a so called @dfn{pending breakpoint}---breakpoint whose address
3801 is not yet resolved.
3803 After the program is run, whenever a new shared library is loaded,
3804 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3805 shared library contains the symbol or line referred to by some
3806 pending breakpoint, that breakpoint is resolved and becomes an
3807 ordinary breakpoint. When a library is unloaded, all breakpoints
3808 that refer to its symbols or source lines become pending again.
3810 This logic works for breakpoints with multiple locations, too. For
3811 example, if you have a breakpoint in a C@t{++} template function, and
3812 a newly loaded shared library has an instantiation of that template,
3813 a new location is added to the list of locations for the breakpoint.
3815 Except for having unresolved address, pending breakpoints do not
3816 differ from regular breakpoints. You can set conditions or commands,
3817 enable and disable them and perform other breakpoint operations.
3819 @value{GDBN} provides some additional commands for controlling what
3820 happens when the @samp{break} command cannot resolve breakpoint
3821 address specification to an address:
3823 @kindex set breakpoint pending
3824 @kindex show breakpoint pending
3826 @item set breakpoint pending auto
3827 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3828 location, it queries you whether a pending breakpoint should be created.
3830 @item set breakpoint pending on
3831 This indicates that an unrecognized breakpoint location should automatically
3832 result in a pending breakpoint being created.
3834 @item set breakpoint pending off
3835 This indicates that pending breakpoints are not to be created. Any
3836 unrecognized breakpoint location results in an error. This setting does
3837 not affect any pending breakpoints previously created.
3839 @item show breakpoint pending
3840 Show the current behavior setting for creating pending breakpoints.
3843 The settings above only affect the @code{break} command and its
3844 variants. Once breakpoint is set, it will be automatically updated
3845 as shared libraries are loaded and unloaded.
3847 @cindex automatic hardware breakpoints
3848 For some targets, @value{GDBN} can automatically decide if hardware or
3849 software breakpoints should be used, depending on whether the
3850 breakpoint address is read-only or read-write. This applies to
3851 breakpoints set with the @code{break} command as well as to internal
3852 breakpoints set by commands like @code{next} and @code{finish}. For
3853 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3856 You can control this automatic behaviour with the following commands::
3858 @kindex set breakpoint auto-hw
3859 @kindex show breakpoint auto-hw
3861 @item set breakpoint auto-hw on
3862 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3863 will try to use the target memory map to decide if software or hardware
3864 breakpoint must be used.
3866 @item set breakpoint auto-hw off
3867 This indicates @value{GDBN} should not automatically select breakpoint
3868 type. If the target provides a memory map, @value{GDBN} will warn when
3869 trying to set software breakpoint at a read-only address.
3872 @value{GDBN} normally implements breakpoints by replacing the program code
3873 at the breakpoint address with a special instruction, which, when
3874 executed, given control to the debugger. By default, the program
3875 code is so modified only when the program is resumed. As soon as
3876 the program stops, @value{GDBN} restores the original instructions. This
3877 behaviour guards against leaving breakpoints inserted in the
3878 target should gdb abrubptly disconnect. However, with slow remote
3879 targets, inserting and removing breakpoint can reduce the performance.
3880 This behavior can be controlled with the following commands::
3882 @kindex set breakpoint always-inserted
3883 @kindex show breakpoint always-inserted
3885 @item set breakpoint always-inserted off
3886 All breakpoints, including newly added by the user, are inserted in
3887 the target only when the target is resumed. All breakpoints are
3888 removed from the target when it stops. This is the default mode.
3890 @item set breakpoint always-inserted on
3891 Causes all breakpoints to be inserted in the target at all times. If
3892 the user adds a new breakpoint, or changes an existing breakpoint, the
3893 breakpoints in the target are updated immediately. A breakpoint is
3894 removed from the target only when breakpoint itself is deleted.
3897 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3898 when a breakpoint breaks. If the condition is true, then the process being
3899 debugged stops, otherwise the process is resumed.
3901 If the target supports evaluating conditions on its end, @value{GDBN} may
3902 download the breakpoint, together with its conditions, to it.
3904 This feature can be controlled via the following commands:
3906 @kindex set breakpoint condition-evaluation
3907 @kindex show breakpoint condition-evaluation
3909 @item set breakpoint condition-evaluation host
3910 This option commands @value{GDBN} to evaluate the breakpoint
3911 conditions on the host's side. Unconditional breakpoints are sent to
3912 the target which in turn receives the triggers and reports them back to GDB
3913 for condition evaluation. This is the standard evaluation mode.
3915 @item set breakpoint condition-evaluation target
3916 This option commands @value{GDBN} to download breakpoint conditions
3917 to the target at the moment of their insertion. The target
3918 is responsible for evaluating the conditional expression and reporting
3919 breakpoint stop events back to @value{GDBN} whenever the condition
3920 is true. Due to limitations of target-side evaluation, some conditions
3921 cannot be evaluated there, e.g., conditions that depend on local data
3922 that is only known to the host. Examples include
3923 conditional expressions involving convenience variables, complex types
3924 that cannot be handled by the agent expression parser and expressions
3925 that are too long to be sent over to the target, specially when the
3926 target is a remote system. In these cases, the conditions will be
3927 evaluated by @value{GDBN}.
3929 @item set breakpoint condition-evaluation auto
3930 This is the default mode. If the target supports evaluating breakpoint
3931 conditions on its end, @value{GDBN} will download breakpoint conditions to
3932 the target (limitations mentioned previously apply). If the target does
3933 not support breakpoint condition evaluation, then @value{GDBN} will fallback
3934 to evaluating all these conditions on the host's side.
3938 @cindex negative breakpoint numbers
3939 @cindex internal @value{GDBN} breakpoints
3940 @value{GDBN} itself sometimes sets breakpoints in your program for
3941 special purposes, such as proper handling of @code{longjmp} (in C
3942 programs). These internal breakpoints are assigned negative numbers,
3943 starting with @code{-1}; @samp{info breakpoints} does not display them.
3944 You can see these breakpoints with the @value{GDBN} maintenance command
3945 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3948 @node Set Watchpoints
3949 @subsection Setting Watchpoints
3951 @cindex setting watchpoints
3952 You can use a watchpoint to stop execution whenever the value of an
3953 expression changes, without having to predict a particular place where
3954 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3955 The expression may be as simple as the value of a single variable, or
3956 as complex as many variables combined by operators. Examples include:
3960 A reference to the value of a single variable.
3963 An address cast to an appropriate data type. For example,
3964 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3965 address (assuming an @code{int} occupies 4 bytes).
3968 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3969 expression can use any operators valid in the program's native
3970 language (@pxref{Languages}).
3973 You can set a watchpoint on an expression even if the expression can
3974 not be evaluated yet. For instance, you can set a watchpoint on
3975 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3976 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3977 the expression produces a valid value. If the expression becomes
3978 valid in some other way than changing a variable (e.g.@: if the memory
3979 pointed to by @samp{*global_ptr} becomes readable as the result of a
3980 @code{malloc} call), @value{GDBN} may not stop until the next time
3981 the expression changes.
3983 @cindex software watchpoints
3984 @cindex hardware watchpoints
3985 Depending on your system, watchpoints may be implemented in software or
3986 hardware. @value{GDBN} does software watchpointing by single-stepping your
3987 program and testing the variable's value each time, which is hundreds of
3988 times slower than normal execution. (But this may still be worth it, to
3989 catch errors where you have no clue what part of your program is the
3992 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3993 x86-based targets, @value{GDBN} includes support for hardware
3994 watchpoints, which do not slow down the running of your program.
3998 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3999 Set a watchpoint for an expression. @value{GDBN} will break when the
4000 expression @var{expr} is written into by the program and its value
4001 changes. The simplest (and the most popular) use of this command is
4002 to watch the value of a single variable:
4005 (@value{GDBP}) watch foo
4008 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
4009 argument, @value{GDBN} breaks only when the thread identified by
4010 @var{threadnum} changes the value of @var{expr}. If any other threads
4011 change the value of @var{expr}, @value{GDBN} will not break. Note
4012 that watchpoints restricted to a single thread in this way only work
4013 with Hardware Watchpoints.
4015 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4016 (see below). The @code{-location} argument tells @value{GDBN} to
4017 instead watch the memory referred to by @var{expr}. In this case,
4018 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4019 and watch the memory at that address. The type of the result is used
4020 to determine the size of the watched memory. If the expression's
4021 result does not have an address, then @value{GDBN} will print an
4024 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4025 of masked watchpoints, if the current architecture supports this
4026 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4027 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4028 to an address to watch. The mask specifies that some bits of an address
4029 (the bits which are reset in the mask) should be ignored when matching
4030 the address accessed by the inferior against the watchpoint address.
4031 Thus, a masked watchpoint watches many addresses simultaneously---those
4032 addresses whose unmasked bits are identical to the unmasked bits in the
4033 watchpoint address. The @code{mask} argument implies @code{-location}.
4037 (@value{GDBP}) watch foo mask 0xffff00ff
4038 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4042 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
4043 Set a watchpoint that will break when the value of @var{expr} is read
4047 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
4048 Set a watchpoint that will break when @var{expr} is either read from
4049 or written into by the program.
4051 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
4052 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
4053 This command prints a list of watchpoints, using the same format as
4054 @code{info break} (@pxref{Set Breaks}).
4057 If you watch for a change in a numerically entered address you need to
4058 dereference it, as the address itself is just a constant number which will
4059 never change. @value{GDBN} refuses to create a watchpoint that watches
4060 a never-changing value:
4063 (@value{GDBP}) watch 0x600850
4064 Cannot watch constant value 0x600850.
4065 (@value{GDBP}) watch *(int *) 0x600850
4066 Watchpoint 1: *(int *) 6293584
4069 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4070 watchpoints execute very quickly, and the debugger reports a change in
4071 value at the exact instruction where the change occurs. If @value{GDBN}
4072 cannot set a hardware watchpoint, it sets a software watchpoint, which
4073 executes more slowly and reports the change in value at the next
4074 @emph{statement}, not the instruction, after the change occurs.
4076 @cindex use only software watchpoints
4077 You can force @value{GDBN} to use only software watchpoints with the
4078 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4079 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4080 the underlying system supports them. (Note that hardware-assisted
4081 watchpoints that were set @emph{before} setting
4082 @code{can-use-hw-watchpoints} to zero will still use the hardware
4083 mechanism of watching expression values.)
4086 @item set can-use-hw-watchpoints
4087 @kindex set can-use-hw-watchpoints
4088 Set whether or not to use hardware watchpoints.
4090 @item show can-use-hw-watchpoints
4091 @kindex show can-use-hw-watchpoints
4092 Show the current mode of using hardware watchpoints.
4095 For remote targets, you can restrict the number of hardware
4096 watchpoints @value{GDBN} will use, see @ref{set remote
4097 hardware-breakpoint-limit}.
4099 When you issue the @code{watch} command, @value{GDBN} reports
4102 Hardware watchpoint @var{num}: @var{expr}
4106 if it was able to set a hardware watchpoint.
4108 Currently, the @code{awatch} and @code{rwatch} commands can only set
4109 hardware watchpoints, because accesses to data that don't change the
4110 value of the watched expression cannot be detected without examining
4111 every instruction as it is being executed, and @value{GDBN} does not do
4112 that currently. If @value{GDBN} finds that it is unable to set a
4113 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4114 will print a message like this:
4117 Expression cannot be implemented with read/access watchpoint.
4120 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4121 data type of the watched expression is wider than what a hardware
4122 watchpoint on the target machine can handle. For example, some systems
4123 can only watch regions that are up to 4 bytes wide; on such systems you
4124 cannot set hardware watchpoints for an expression that yields a
4125 double-precision floating-point number (which is typically 8 bytes
4126 wide). As a work-around, it might be possible to break the large region
4127 into a series of smaller ones and watch them with separate watchpoints.
4129 If you set too many hardware watchpoints, @value{GDBN} might be unable
4130 to insert all of them when you resume the execution of your program.
4131 Since the precise number of active watchpoints is unknown until such
4132 time as the program is about to be resumed, @value{GDBN} might not be
4133 able to warn you about this when you set the watchpoints, and the
4134 warning will be printed only when the program is resumed:
4137 Hardware watchpoint @var{num}: Could not insert watchpoint
4141 If this happens, delete or disable some of the watchpoints.
4143 Watching complex expressions that reference many variables can also
4144 exhaust the resources available for hardware-assisted watchpoints.
4145 That's because @value{GDBN} needs to watch every variable in the
4146 expression with separately allocated resources.
4148 If you call a function interactively using @code{print} or @code{call},
4149 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4150 kind of breakpoint or the call completes.
4152 @value{GDBN} automatically deletes watchpoints that watch local
4153 (automatic) variables, or expressions that involve such variables, when
4154 they go out of scope, that is, when the execution leaves the block in
4155 which these variables were defined. In particular, when the program
4156 being debugged terminates, @emph{all} local variables go out of scope,
4157 and so only watchpoints that watch global variables remain set. If you
4158 rerun the program, you will need to set all such watchpoints again. One
4159 way of doing that would be to set a code breakpoint at the entry to the
4160 @code{main} function and when it breaks, set all the watchpoints.
4162 @cindex watchpoints and threads
4163 @cindex threads and watchpoints
4164 In multi-threaded programs, watchpoints will detect changes to the
4165 watched expression from every thread.
4168 @emph{Warning:} In multi-threaded programs, software watchpoints
4169 have only limited usefulness. If @value{GDBN} creates a software
4170 watchpoint, it can only watch the value of an expression @emph{in a
4171 single thread}. If you are confident that the expression can only
4172 change due to the current thread's activity (and if you are also
4173 confident that no other thread can become current), then you can use
4174 software watchpoints as usual. However, @value{GDBN} may not notice
4175 when a non-current thread's activity changes the expression. (Hardware
4176 watchpoints, in contrast, watch an expression in all threads.)
4179 @xref{set remote hardware-watchpoint-limit}.
4181 @node Set Catchpoints
4182 @subsection Setting Catchpoints
4183 @cindex catchpoints, setting
4184 @cindex exception handlers
4185 @cindex event handling
4187 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4188 kinds of program events, such as C@t{++} exceptions or the loading of a
4189 shared library. Use the @code{catch} command to set a catchpoint.
4193 @item catch @var{event}
4194 Stop when @var{event} occurs. The @var{event} can be any of the following:
4197 @item throw @r{[}@var{regexp}@r{]}
4198 @itemx rethrow @r{[}@var{regexp}@r{]}
4199 @itemx catch @r{[}@var{regexp}@r{]}
4201 @kindex catch rethrow
4203 @cindex stop on C@t{++} exceptions
4204 The throwing, re-throwing, or catching of a C@t{++} exception.
4206 If @var{regexp} is given, then only exceptions whose type matches the
4207 regular expression will be caught.
4209 @vindex $_exception@r{, convenience variable}
4210 The convenience variable @code{$_exception} is available at an
4211 exception-related catchpoint, on some systems. This holds the
4212 exception being thrown.
4214 There are currently some limitations to C@t{++} exception handling in
4219 The support for these commands is system-dependent. Currently, only
4220 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4224 The regular expression feature and the @code{$_exception} convenience
4225 variable rely on the presence of some SDT probes in @code{libstdc++}.
4226 If these probes are not present, then these features cannot be used.
4227 These probes were first available in the GCC 4.8 release, but whether
4228 or not they are available in your GCC also depends on how it was
4232 The @code{$_exception} convenience variable is only valid at the
4233 instruction at which an exception-related catchpoint is set.
4236 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4237 location in the system library which implements runtime exception
4238 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4239 (@pxref{Selection}) to get to your code.
4242 If you call a function interactively, @value{GDBN} normally returns
4243 control to you when the function has finished executing. If the call
4244 raises an exception, however, the call may bypass the mechanism that
4245 returns control to you and cause your program either to abort or to
4246 simply continue running until it hits a breakpoint, catches a signal
4247 that @value{GDBN} is listening for, or exits. This is the case even if
4248 you set a catchpoint for the exception; catchpoints on exceptions are
4249 disabled within interactive calls. @xref{Calling}, for information on
4250 controlling this with @code{set unwind-on-terminating-exception}.
4253 You cannot raise an exception interactively.
4256 You cannot install an exception handler interactively.
4260 @kindex catch exception
4261 @cindex Ada exception catching
4262 @cindex catch Ada exceptions
4263 An Ada exception being raised. If an exception name is specified
4264 at the end of the command (eg @code{catch exception Program_Error}),
4265 the debugger will stop only when this specific exception is raised.
4266 Otherwise, the debugger stops execution when any Ada exception is raised.
4268 When inserting an exception catchpoint on a user-defined exception whose
4269 name is identical to one of the exceptions defined by the language, the
4270 fully qualified name must be used as the exception name. Otherwise,
4271 @value{GDBN} will assume that it should stop on the pre-defined exception
4272 rather than the user-defined one. For instance, assuming an exception
4273 called @code{Constraint_Error} is defined in package @code{Pck}, then
4274 the command to use to catch such exceptions is @kbd{catch exception
4275 Pck.Constraint_Error}.
4277 @item exception unhandled
4278 @kindex catch exception unhandled
4279 An exception that was raised but is not handled by the program.
4282 @kindex catch assert
4283 A failed Ada assertion.
4287 @cindex break on fork/exec
4288 A call to @code{exec}. This is currently only available for HP-UX
4292 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4293 @kindex catch syscall
4294 @cindex break on a system call.
4295 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4296 syscall is a mechanism for application programs to request a service
4297 from the operating system (OS) or one of the OS system services.
4298 @value{GDBN} can catch some or all of the syscalls issued by the
4299 debuggee, and show the related information for each syscall. If no
4300 argument is specified, calls to and returns from all system calls
4303 @var{name} can be any system call name that is valid for the
4304 underlying OS. Just what syscalls are valid depends on the OS. On
4305 GNU and Unix systems, you can find the full list of valid syscall
4306 names on @file{/usr/include/asm/unistd.h}.
4308 @c For MS-Windows, the syscall names and the corresponding numbers
4309 @c can be found, e.g., on this URL:
4310 @c http://www.metasploit.com/users/opcode/syscalls.html
4311 @c but we don't support Windows syscalls yet.
4313 Normally, @value{GDBN} knows in advance which syscalls are valid for
4314 each OS, so you can use the @value{GDBN} command-line completion
4315 facilities (@pxref{Completion,, command completion}) to list the
4318 You may also specify the system call numerically. A syscall's
4319 number is the value passed to the OS's syscall dispatcher to
4320 identify the requested service. When you specify the syscall by its
4321 name, @value{GDBN} uses its database of syscalls to convert the name
4322 into the corresponding numeric code, but using the number directly
4323 may be useful if @value{GDBN}'s database does not have the complete
4324 list of syscalls on your system (e.g., because @value{GDBN} lags
4325 behind the OS upgrades).
4327 The example below illustrates how this command works if you don't provide
4331 (@value{GDBP}) catch syscall
4332 Catchpoint 1 (syscall)
4334 Starting program: /tmp/catch-syscall
4336 Catchpoint 1 (call to syscall 'close'), \
4337 0xffffe424 in __kernel_vsyscall ()
4341 Catchpoint 1 (returned from syscall 'close'), \
4342 0xffffe424 in __kernel_vsyscall ()
4346 Here is an example of catching a system call by name:
4349 (@value{GDBP}) catch syscall chroot
4350 Catchpoint 1 (syscall 'chroot' [61])
4352 Starting program: /tmp/catch-syscall
4354 Catchpoint 1 (call to syscall 'chroot'), \
4355 0xffffe424 in __kernel_vsyscall ()
4359 Catchpoint 1 (returned from syscall 'chroot'), \
4360 0xffffe424 in __kernel_vsyscall ()
4364 An example of specifying a system call numerically. In the case
4365 below, the syscall number has a corresponding entry in the XML
4366 file, so @value{GDBN} finds its name and prints it:
4369 (@value{GDBP}) catch syscall 252
4370 Catchpoint 1 (syscall(s) 'exit_group')
4372 Starting program: /tmp/catch-syscall
4374 Catchpoint 1 (call to syscall 'exit_group'), \
4375 0xffffe424 in __kernel_vsyscall ()
4379 Program exited normally.
4383 However, there can be situations when there is no corresponding name
4384 in XML file for that syscall number. In this case, @value{GDBN} prints
4385 a warning message saying that it was not able to find the syscall name,
4386 but the catchpoint will be set anyway. See the example below:
4389 (@value{GDBP}) catch syscall 764
4390 warning: The number '764' does not represent a known syscall.
4391 Catchpoint 2 (syscall 764)
4395 If you configure @value{GDBN} using the @samp{--without-expat} option,
4396 it will not be able to display syscall names. Also, if your
4397 architecture does not have an XML file describing its system calls,
4398 you will not be able to see the syscall names. It is important to
4399 notice that these two features are used for accessing the syscall
4400 name database. In either case, you will see a warning like this:
4403 (@value{GDBP}) catch syscall
4404 warning: Could not open "syscalls/i386-linux.xml"
4405 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4406 GDB will not be able to display syscall names.
4407 Catchpoint 1 (syscall)
4411 Of course, the file name will change depending on your architecture and system.
4413 Still using the example above, you can also try to catch a syscall by its
4414 number. In this case, you would see something like:
4417 (@value{GDBP}) catch syscall 252
4418 Catchpoint 1 (syscall(s) 252)
4421 Again, in this case @value{GDBN} would not be able to display syscall's names.
4425 A call to @code{fork}. This is currently only available for HP-UX
4430 A call to @code{vfork}. This is currently only available for HP-UX
4433 @item load @r{[}regexp@r{]}
4434 @itemx unload @r{[}regexp@r{]}
4436 @kindex catch unload
4437 The loading or unloading of a shared library. If @var{regexp} is
4438 given, then the catchpoint will stop only if the regular expression
4439 matches one of the affected libraries.
4441 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4442 @kindex catch signal
4443 The delivery of a signal.
4445 With no arguments, this catchpoint will catch any signal that is not
4446 used internally by @value{GDBN}, specifically, all signals except
4447 @samp{SIGTRAP} and @samp{SIGINT}.
4449 With the argument @samp{all}, all signals, including those used by
4450 @value{GDBN}, will be caught. This argument cannot be used with other
4453 Otherwise, the arguments are a list of signal names as given to
4454 @code{handle} (@pxref{Signals}). Only signals specified in this list
4457 One reason that @code{catch signal} can be more useful than
4458 @code{handle} is that you can attach commands and conditions to the
4461 When a signal is caught by a catchpoint, the signal's @code{stop} and
4462 @code{print} settings, as specified by @code{handle}, are ignored.
4463 However, whether the signal is still delivered to the inferior depends
4464 on the @code{pass} setting; this can be changed in the catchpoint's
4469 @item tcatch @var{event}
4471 Set a catchpoint that is enabled only for one stop. The catchpoint is
4472 automatically deleted after the first time the event is caught.
4476 Use the @code{info break} command to list the current catchpoints.
4480 @subsection Deleting Breakpoints
4482 @cindex clearing breakpoints, watchpoints, catchpoints
4483 @cindex deleting breakpoints, watchpoints, catchpoints
4484 It is often necessary to eliminate a breakpoint, watchpoint, or
4485 catchpoint once it has done its job and you no longer want your program
4486 to stop there. This is called @dfn{deleting} the breakpoint. A
4487 breakpoint that has been deleted no longer exists; it is forgotten.
4489 With the @code{clear} command you can delete breakpoints according to
4490 where they are in your program. With the @code{delete} command you can
4491 delete individual breakpoints, watchpoints, or catchpoints by specifying
4492 their breakpoint numbers.
4494 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4495 automatically ignores breakpoints on the first instruction to be executed
4496 when you continue execution without changing the execution address.
4501 Delete any breakpoints at the next instruction to be executed in the
4502 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4503 the innermost frame is selected, this is a good way to delete a
4504 breakpoint where your program just stopped.
4506 @item clear @var{location}
4507 Delete any breakpoints set at the specified @var{location}.
4508 @xref{Specify Location}, for the various forms of @var{location}; the
4509 most useful ones are listed below:
4512 @item clear @var{function}
4513 @itemx clear @var{filename}:@var{function}
4514 Delete any breakpoints set at entry to the named @var{function}.
4516 @item clear @var{linenum}
4517 @itemx clear @var{filename}:@var{linenum}
4518 Delete any breakpoints set at or within the code of the specified
4519 @var{linenum} of the specified @var{filename}.
4522 @cindex delete breakpoints
4524 @kindex d @r{(@code{delete})}
4525 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4526 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4527 ranges specified as arguments. If no argument is specified, delete all
4528 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4529 confirm off}). You can abbreviate this command as @code{d}.
4533 @subsection Disabling Breakpoints
4535 @cindex enable/disable a breakpoint
4536 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4537 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4538 it had been deleted, but remembers the information on the breakpoint so
4539 that you can @dfn{enable} it again later.
4541 You disable and enable breakpoints, watchpoints, and catchpoints with
4542 the @code{enable} and @code{disable} commands, optionally specifying
4543 one or more breakpoint numbers as arguments. Use @code{info break} to
4544 print a list of all breakpoints, watchpoints, and catchpoints if you
4545 do not know which numbers to use.
4547 Disabling and enabling a breakpoint that has multiple locations
4548 affects all of its locations.
4550 A breakpoint, watchpoint, or catchpoint can have any of several
4551 different states of enablement:
4555 Enabled. The breakpoint stops your program. A breakpoint set
4556 with the @code{break} command starts out in this state.
4558 Disabled. The breakpoint has no effect on your program.
4560 Enabled once. The breakpoint stops your program, but then becomes
4563 Enabled for a count. The breakpoint stops your program for the next
4564 N times, then becomes disabled.
4566 Enabled for deletion. The breakpoint stops your program, but
4567 immediately after it does so it is deleted permanently. A breakpoint
4568 set with the @code{tbreak} command starts out in this state.
4571 You can use the following commands to enable or disable breakpoints,
4572 watchpoints, and catchpoints:
4576 @kindex dis @r{(@code{disable})}
4577 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4578 Disable the specified breakpoints---or all breakpoints, if none are
4579 listed. A disabled breakpoint has no effect but is not forgotten. All
4580 options such as ignore-counts, conditions and commands are remembered in
4581 case the breakpoint is enabled again later. You may abbreviate
4582 @code{disable} as @code{dis}.
4585 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4586 Enable the specified breakpoints (or all defined breakpoints). They
4587 become effective once again in stopping your program.
4589 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4590 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4591 of these breakpoints immediately after stopping your program.
4593 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4594 Enable the specified breakpoints temporarily. @value{GDBN} records
4595 @var{count} with each of the specified breakpoints, and decrements a
4596 breakpoint's count when it is hit. When any count reaches 0,
4597 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4598 count (@pxref{Conditions, ,Break Conditions}), that will be
4599 decremented to 0 before @var{count} is affected.
4601 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4602 Enable the specified breakpoints to work once, then die. @value{GDBN}
4603 deletes any of these breakpoints as soon as your program stops there.
4604 Breakpoints set by the @code{tbreak} command start out in this state.
4607 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4608 @c confusing: tbreak is also initially enabled.
4609 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4610 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4611 subsequently, they become disabled or enabled only when you use one of
4612 the commands above. (The command @code{until} can set and delete a
4613 breakpoint of its own, but it does not change the state of your other
4614 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4618 @subsection Break Conditions
4619 @cindex conditional breakpoints
4620 @cindex breakpoint conditions
4622 @c FIXME what is scope of break condition expr? Context where wanted?
4623 @c in particular for a watchpoint?
4624 The simplest sort of breakpoint breaks every time your program reaches a
4625 specified place. You can also specify a @dfn{condition} for a
4626 breakpoint. A condition is just a Boolean expression in your
4627 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4628 a condition evaluates the expression each time your program reaches it,
4629 and your program stops only if the condition is @emph{true}.
4631 This is the converse of using assertions for program validation; in that
4632 situation, you want to stop when the assertion is violated---that is,
4633 when the condition is false. In C, if you want to test an assertion expressed
4634 by the condition @var{assert}, you should set the condition
4635 @samp{! @var{assert}} on the appropriate breakpoint.
4637 Conditions are also accepted for watchpoints; you may not need them,
4638 since a watchpoint is inspecting the value of an expression anyhow---but
4639 it might be simpler, say, to just set a watchpoint on a variable name,
4640 and specify a condition that tests whether the new value is an interesting
4643 Break conditions can have side effects, and may even call functions in
4644 your program. This can be useful, for example, to activate functions
4645 that log program progress, or to use your own print functions to
4646 format special data structures. The effects are completely predictable
4647 unless there is another enabled breakpoint at the same address. (In
4648 that case, @value{GDBN} might see the other breakpoint first and stop your
4649 program without checking the condition of this one.) Note that
4650 breakpoint commands are usually more convenient and flexible than break
4652 purpose of performing side effects when a breakpoint is reached
4653 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4655 Breakpoint conditions can also be evaluated on the target's side if
4656 the target supports it. Instead of evaluating the conditions locally,
4657 @value{GDBN} encodes the expression into an agent expression
4658 (@pxref{Agent Expressions}) suitable for execution on the target,
4659 independently of @value{GDBN}. Global variables become raw memory
4660 locations, locals become stack accesses, and so forth.
4662 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4663 when its condition evaluates to true. This mechanism may provide faster
4664 response times depending on the performance characteristics of the target
4665 since it does not need to keep @value{GDBN} informed about
4666 every breakpoint trigger, even those with false conditions.
4668 Break conditions can be specified when a breakpoint is set, by using
4669 @samp{if} in the arguments to the @code{break} command. @xref{Set
4670 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4671 with the @code{condition} command.
4673 You can also use the @code{if} keyword with the @code{watch} command.
4674 The @code{catch} command does not recognize the @code{if} keyword;
4675 @code{condition} is the only way to impose a further condition on a
4680 @item condition @var{bnum} @var{expression}
4681 Specify @var{expression} as the break condition for breakpoint,
4682 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4683 breakpoint @var{bnum} stops your program only if the value of
4684 @var{expression} is true (nonzero, in C). When you use
4685 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4686 syntactic correctness, and to determine whether symbols in it have
4687 referents in the context of your breakpoint. If @var{expression} uses
4688 symbols not referenced in the context of the breakpoint, @value{GDBN}
4689 prints an error message:
4692 No symbol "foo" in current context.
4697 not actually evaluate @var{expression} at the time the @code{condition}
4698 command (or a command that sets a breakpoint with a condition, like
4699 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4701 @item condition @var{bnum}
4702 Remove the condition from breakpoint number @var{bnum}. It becomes
4703 an ordinary unconditional breakpoint.
4706 @cindex ignore count (of breakpoint)
4707 A special case of a breakpoint condition is to stop only when the
4708 breakpoint has been reached a certain number of times. This is so
4709 useful that there is a special way to do it, using the @dfn{ignore
4710 count} of the breakpoint. Every breakpoint has an ignore count, which
4711 is an integer. Most of the time, the ignore count is zero, and
4712 therefore has no effect. But if your program reaches a breakpoint whose
4713 ignore count is positive, then instead of stopping, it just decrements
4714 the ignore count by one and continues. As a result, if the ignore count
4715 value is @var{n}, the breakpoint does not stop the next @var{n} times
4716 your program reaches it.
4720 @item ignore @var{bnum} @var{count}
4721 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4722 The next @var{count} times the breakpoint is reached, your program's
4723 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4726 To make the breakpoint stop the next time it is reached, specify
4729 When you use @code{continue} to resume execution of your program from a
4730 breakpoint, you can specify an ignore count directly as an argument to
4731 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4732 Stepping,,Continuing and Stepping}.
4734 If a breakpoint has a positive ignore count and a condition, the
4735 condition is not checked. Once the ignore count reaches zero,
4736 @value{GDBN} resumes checking the condition.
4738 You could achieve the effect of the ignore count with a condition such
4739 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4740 is decremented each time. @xref{Convenience Vars, ,Convenience
4744 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4747 @node Break Commands
4748 @subsection Breakpoint Command Lists
4750 @cindex breakpoint commands
4751 You can give any breakpoint (or watchpoint or catchpoint) a series of
4752 commands to execute when your program stops due to that breakpoint. For
4753 example, you might want to print the values of certain expressions, or
4754 enable other breakpoints.
4758 @kindex end@r{ (breakpoint commands)}
4759 @item commands @r{[}@var{range}@dots{}@r{]}
4760 @itemx @dots{} @var{command-list} @dots{}
4762 Specify a list of commands for the given breakpoints. The commands
4763 themselves appear on the following lines. Type a line containing just
4764 @code{end} to terminate the commands.
4766 To remove all commands from a breakpoint, type @code{commands} and
4767 follow it immediately with @code{end}; that is, give no commands.
4769 With no argument, @code{commands} refers to the last breakpoint,
4770 watchpoint, or catchpoint set (not to the breakpoint most recently
4771 encountered). If the most recent breakpoints were set with a single
4772 command, then the @code{commands} will apply to all the breakpoints
4773 set by that command. This applies to breakpoints set by
4774 @code{rbreak}, and also applies when a single @code{break} command
4775 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4779 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4780 disabled within a @var{command-list}.
4782 You can use breakpoint commands to start your program up again. Simply
4783 use the @code{continue} command, or @code{step}, or any other command
4784 that resumes execution.
4786 Any other commands in the command list, after a command that resumes
4787 execution, are ignored. This is because any time you resume execution
4788 (even with a simple @code{next} or @code{step}), you may encounter
4789 another breakpoint---which could have its own command list, leading to
4790 ambiguities about which list to execute.
4793 If the first command you specify in a command list is @code{silent}, the
4794 usual message about stopping at a breakpoint is not printed. This may
4795 be desirable for breakpoints that are to print a specific message and
4796 then continue. If none of the remaining commands print anything, you
4797 see no sign that the breakpoint was reached. @code{silent} is
4798 meaningful only at the beginning of a breakpoint command list.
4800 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4801 print precisely controlled output, and are often useful in silent
4802 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4804 For example, here is how you could use breakpoint commands to print the
4805 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4811 printf "x is %d\n",x
4816 One application for breakpoint commands is to compensate for one bug so
4817 you can test for another. Put a breakpoint just after the erroneous line
4818 of code, give it a condition to detect the case in which something
4819 erroneous has been done, and give it commands to assign correct values
4820 to any variables that need them. End with the @code{continue} command
4821 so that your program does not stop, and start with the @code{silent}
4822 command so that no output is produced. Here is an example:
4833 @node Dynamic Printf
4834 @subsection Dynamic Printf
4836 @cindex dynamic printf
4838 The dynamic printf command @code{dprintf} combines a breakpoint with
4839 formatted printing of your program's data to give you the effect of
4840 inserting @code{printf} calls into your program on-the-fly, without
4841 having to recompile it.
4843 In its most basic form, the output goes to the GDB console. However,
4844 you can set the variable @code{dprintf-style} for alternate handling.
4845 For instance, you can ask to format the output by calling your
4846 program's @code{printf} function. This has the advantage that the
4847 characters go to the program's output device, so they can recorded in
4848 redirects to files and so forth.
4850 If you are doing remote debugging with a stub or agent, you can also
4851 ask to have the printf handled by the remote agent. In addition to
4852 ensuring that the output goes to the remote program's device along
4853 with any other output the program might produce, you can also ask that
4854 the dprintf remain active even after disconnecting from the remote
4855 target. Using the stub/agent is also more efficient, as it can do
4856 everything without needing to communicate with @value{GDBN}.
4860 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4861 Whenever execution reaches @var{location}, print the values of one or
4862 more @var{expressions} under the control of the string @var{template}.
4863 To print several values, separate them with commas.
4865 @item set dprintf-style @var{style}
4866 Set the dprintf output to be handled in one of several different
4867 styles enumerated below. A change of style affects all existing
4868 dynamic printfs immediately. (If you need individual control over the
4869 print commands, simply define normal breakpoints with
4870 explicitly-supplied command lists.)
4873 @kindex dprintf-style gdb
4874 Handle the output using the @value{GDBN} @code{printf} command.
4877 @kindex dprintf-style call
4878 Handle the output by calling a function in your program (normally
4882 @kindex dprintf-style agent
4883 Have the remote debugging agent (such as @code{gdbserver}) handle
4884 the output itself. This style is only available for agents that
4885 support running commands on the target.
4887 @item set dprintf-function @var{function}
4888 Set the function to call if the dprintf style is @code{call}. By
4889 default its value is @code{printf}. You may set it to any expression.
4890 that @value{GDBN} can evaluate to a function, as per the @code{call}
4893 @item set dprintf-channel @var{channel}
4894 Set a ``channel'' for dprintf. If set to a non-empty value,
4895 @value{GDBN} will evaluate it as an expression and pass the result as
4896 a first argument to the @code{dprintf-function}, in the manner of
4897 @code{fprintf} and similar functions. Otherwise, the dprintf format
4898 string will be the first argument, in the manner of @code{printf}.
4900 As an example, if you wanted @code{dprintf} output to go to a logfile
4901 that is a standard I/O stream assigned to the variable @code{mylog},
4902 you could do the following:
4905 (gdb) set dprintf-style call
4906 (gdb) set dprintf-function fprintf
4907 (gdb) set dprintf-channel mylog
4908 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
4909 Dprintf 1 at 0x123456: file main.c, line 25.
4911 1 dprintf keep y 0x00123456 in main at main.c:25
4912 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
4917 Note that the @code{info break} displays the dynamic printf commands
4918 as normal breakpoint commands; you can thus easily see the effect of
4919 the variable settings.
4921 @item set disconnected-dprintf on
4922 @itemx set disconnected-dprintf off
4923 @kindex set disconnected-dprintf
4924 Choose whether @code{dprintf} commands should continue to run if
4925 @value{GDBN} has disconnected from the target. This only applies
4926 if the @code{dprintf-style} is @code{agent}.
4928 @item show disconnected-dprintf off
4929 @kindex show disconnected-dprintf
4930 Show the current choice for disconnected @code{dprintf}.
4934 @value{GDBN} does not check the validity of function and channel,
4935 relying on you to supply values that are meaningful for the contexts
4936 in which they are being used. For instance, the function and channel
4937 may be the values of local variables, but if that is the case, then
4938 all enabled dynamic prints must be at locations within the scope of
4939 those locals. If evaluation fails, @value{GDBN} will report an error.
4941 @node Save Breakpoints
4942 @subsection How to save breakpoints to a file
4944 To save breakpoint definitions to a file use the @w{@code{save
4945 breakpoints}} command.
4948 @kindex save breakpoints
4949 @cindex save breakpoints to a file for future sessions
4950 @item save breakpoints [@var{filename}]
4951 This command saves all current breakpoint definitions together with
4952 their commands and ignore counts, into a file @file{@var{filename}}
4953 suitable for use in a later debugging session. This includes all
4954 types of breakpoints (breakpoints, watchpoints, catchpoints,
4955 tracepoints). To read the saved breakpoint definitions, use the
4956 @code{source} command (@pxref{Command Files}). Note that watchpoints
4957 with expressions involving local variables may fail to be recreated
4958 because it may not be possible to access the context where the
4959 watchpoint is valid anymore. Because the saved breakpoint definitions
4960 are simply a sequence of @value{GDBN} commands that recreate the
4961 breakpoints, you can edit the file in your favorite editing program,
4962 and remove the breakpoint definitions you're not interested in, or
4963 that can no longer be recreated.
4966 @node Static Probe Points
4967 @subsection Static Probe Points
4969 @cindex static probe point, SystemTap
4970 @cindex static probe point, DTrace
4971 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
4972 for Statically Defined Tracing, and the probes are designed to have a tiny
4973 runtime code and data footprint, and no dynamic relocations.
4975 Currently, the following types of probes are supported on
4976 ELF-compatible systems:
4980 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
4981 @acronym{SDT} probes@footnote{See
4982 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
4983 for more information on how to add @code{SystemTap} @acronym{SDT}
4984 probes in your applications.}. @code{SystemTap} probes are usable
4985 from assembly, C and C@t{++} languages@footnote{See
4986 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
4987 for a good reference on how the @acronym{SDT} probes are implemented.}.
4989 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
4990 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
4994 @cindex semaphores on static probe points
4995 Some @code{SystemTap} probes have an associated semaphore variable;
4996 for instance, this happens automatically if you defined your probe
4997 using a DTrace-style @file{.d} file. If your probe has a semaphore,
4998 @value{GDBN} will automatically enable it when you specify a
4999 breakpoint using the @samp{-probe-stap} notation. But, if you put a
5000 breakpoint at a probe's location by some other method (e.g.,
5001 @code{break file:line}), then @value{GDBN} will not automatically set
5002 the semaphore. @code{DTrace} probes do not support semaphores.
5004 You can examine the available static static probes using @code{info
5005 probes}, with optional arguments:
5009 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5010 If given, @var{type} is either @code{stap} for listing
5011 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5012 probes. If omitted all probes are listed regardless of their types.
5014 If given, @var{provider} is a regular expression used to match against provider
5015 names when selecting which probes to list. If omitted, probes by all
5016 probes from all providers are listed.
5018 If given, @var{name} is a regular expression to match against probe names
5019 when selecting which probes to list. If omitted, probe names are not
5020 considered when deciding whether to display them.
5022 If given, @var{objfile} is a regular expression used to select which
5023 object files (executable or shared libraries) to examine. If not
5024 given, all object files are considered.
5026 @item info probes all
5027 List the available static probes, from all types.
5030 @cindex enabling and disabling probes
5031 Some probe points can be enabled and/or disabled. The effect of
5032 enabling or disabling a probe depends on the type of probe being
5033 handled. Some @code{DTrace} probes can be enabled or
5034 disabled, but @code{SystemTap} probes cannot be disabled.
5036 You can enable (or disable) one or more probes using the following
5037 commands, with optional arguments:
5040 @kindex enable probes
5041 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5042 If given, @var{provider} is a regular expression used to match against
5043 provider names when selecting which probes to enable. If omitted,
5044 all probes from all providers are enabled.
5046 If given, @var{name} is a regular expression to match against probe
5047 names when selecting which probes to enable. If omitted, probe names
5048 are not considered when deciding whether to enable them.
5050 If given, @var{objfile} is a regular expression used to select which
5051 object files (executable or shared libraries) to examine. If not
5052 given, all object files are considered.
5054 @kindex disable probes
5055 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5056 See the @code{enable probes} command above for a description of the
5057 optional arguments accepted by this command.
5060 @vindex $_probe_arg@r{, convenience variable}
5061 A probe may specify up to twelve arguments. These are available at the
5062 point at which the probe is defined---that is, when the current PC is
5063 at the probe's location. The arguments are available using the
5064 convenience variables (@pxref{Convenience Vars})
5065 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
5066 probes each probe argument is an integer of the appropriate size;
5067 types are not preserved. In @code{DTrace} probes types are preserved
5068 provided that they are recognized as such by @value{GDBN}; otherwise
5069 the value of the probe argument will be a long integer. The
5070 convenience variable @code{$_probe_argc} holds the number of arguments
5071 at the current probe point.
5073 These variables are always available, but attempts to access them at
5074 any location other than a probe point will cause @value{GDBN} to give
5078 @c @ifclear BARETARGET
5079 @node Error in Breakpoints
5080 @subsection ``Cannot insert breakpoints''
5082 If you request too many active hardware-assisted breakpoints and
5083 watchpoints, you will see this error message:
5085 @c FIXME: the precise wording of this message may change; the relevant
5086 @c source change is not committed yet (Sep 3, 1999).
5088 Stopped; cannot insert breakpoints.
5089 You may have requested too many hardware breakpoints and watchpoints.
5093 This message is printed when you attempt to resume the program, since
5094 only then @value{GDBN} knows exactly how many hardware breakpoints and
5095 watchpoints it needs to insert.
5097 When this message is printed, you need to disable or remove some of the
5098 hardware-assisted breakpoints and watchpoints, and then continue.
5100 @node Breakpoint-related Warnings
5101 @subsection ``Breakpoint address adjusted...''
5102 @cindex breakpoint address adjusted
5104 Some processor architectures place constraints on the addresses at
5105 which breakpoints may be placed. For architectures thus constrained,
5106 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5107 with the constraints dictated by the architecture.
5109 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5110 a VLIW architecture in which a number of RISC-like instructions may be
5111 bundled together for parallel execution. The FR-V architecture
5112 constrains the location of a breakpoint instruction within such a
5113 bundle to the instruction with the lowest address. @value{GDBN}
5114 honors this constraint by adjusting a breakpoint's address to the
5115 first in the bundle.
5117 It is not uncommon for optimized code to have bundles which contain
5118 instructions from different source statements, thus it may happen that
5119 a breakpoint's address will be adjusted from one source statement to
5120 another. Since this adjustment may significantly alter @value{GDBN}'s
5121 breakpoint related behavior from what the user expects, a warning is
5122 printed when the breakpoint is first set and also when the breakpoint
5125 A warning like the one below is printed when setting a breakpoint
5126 that's been subject to address adjustment:
5129 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5132 Such warnings are printed both for user settable and @value{GDBN}'s
5133 internal breakpoints. If you see one of these warnings, you should
5134 verify that a breakpoint set at the adjusted address will have the
5135 desired affect. If not, the breakpoint in question may be removed and
5136 other breakpoints may be set which will have the desired behavior.
5137 E.g., it may be sufficient to place the breakpoint at a later
5138 instruction. A conditional breakpoint may also be useful in some
5139 cases to prevent the breakpoint from triggering too often.
5141 @value{GDBN} will also issue a warning when stopping at one of these
5142 adjusted breakpoints:
5145 warning: Breakpoint 1 address previously adjusted from 0x00010414
5149 When this warning is encountered, it may be too late to take remedial
5150 action except in cases where the breakpoint is hit earlier or more
5151 frequently than expected.
5153 @node Continuing and Stepping
5154 @section Continuing and Stepping
5158 @cindex resuming execution
5159 @dfn{Continuing} means resuming program execution until your program
5160 completes normally. In contrast, @dfn{stepping} means executing just
5161 one more ``step'' of your program, where ``step'' may mean either one
5162 line of source code, or one machine instruction (depending on what
5163 particular command you use). Either when continuing or when stepping,
5164 your program may stop even sooner, due to a breakpoint or a signal. (If
5165 it stops due to a signal, you may want to use @code{handle}, or use
5166 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5167 or you may step into the signal's handler (@pxref{stepping and signal
5172 @kindex c @r{(@code{continue})}
5173 @kindex fg @r{(resume foreground execution)}
5174 @item continue @r{[}@var{ignore-count}@r{]}
5175 @itemx c @r{[}@var{ignore-count}@r{]}
5176 @itemx fg @r{[}@var{ignore-count}@r{]}
5177 Resume program execution, at the address where your program last stopped;
5178 any breakpoints set at that address are bypassed. The optional argument
5179 @var{ignore-count} allows you to specify a further number of times to
5180 ignore a breakpoint at this location; its effect is like that of
5181 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5183 The argument @var{ignore-count} is meaningful only when your program
5184 stopped due to a breakpoint. At other times, the argument to
5185 @code{continue} is ignored.
5187 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5188 debugged program is deemed to be the foreground program) are provided
5189 purely for convenience, and have exactly the same behavior as
5193 To resume execution at a different place, you can use @code{return}
5194 (@pxref{Returning, ,Returning from a Function}) to go back to the
5195 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5196 Different Address}) to go to an arbitrary location in your program.
5198 A typical technique for using stepping is to set a breakpoint
5199 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5200 beginning of the function or the section of your program where a problem
5201 is believed to lie, run your program until it stops at that breakpoint,
5202 and then step through the suspect area, examining the variables that are
5203 interesting, until you see the problem happen.
5207 @kindex s @r{(@code{step})}
5209 Continue running your program until control reaches a different source
5210 line, then stop it and return control to @value{GDBN}. This command is
5211 abbreviated @code{s}.
5214 @c "without debugging information" is imprecise; actually "without line
5215 @c numbers in the debugging information". (gcc -g1 has debugging info but
5216 @c not line numbers). But it seems complex to try to make that
5217 @c distinction here.
5218 @emph{Warning:} If you use the @code{step} command while control is
5219 within a function that was compiled without debugging information,
5220 execution proceeds until control reaches a function that does have
5221 debugging information. Likewise, it will not step into a function which
5222 is compiled without debugging information. To step through functions
5223 without debugging information, use the @code{stepi} command, described
5227 The @code{step} command only stops at the first instruction of a source
5228 line. This prevents the multiple stops that could otherwise occur in
5229 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5230 to stop if a function that has debugging information is called within
5231 the line. In other words, @code{step} @emph{steps inside} any functions
5232 called within the line.
5234 Also, the @code{step} command only enters a function if there is line
5235 number information for the function. Otherwise it acts like the
5236 @code{next} command. This avoids problems when using @code{cc -gl}
5237 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5238 was any debugging information about the routine.
5240 @item step @var{count}
5241 Continue running as in @code{step}, but do so @var{count} times. If a
5242 breakpoint is reached, or a signal not related to stepping occurs before
5243 @var{count} steps, stepping stops right away.
5246 @kindex n @r{(@code{next})}
5247 @item next @r{[}@var{count}@r{]}
5248 Continue to the next source line in the current (innermost) stack frame.
5249 This is similar to @code{step}, but function calls that appear within
5250 the line of code are executed without stopping. Execution stops when
5251 control reaches a different line of code at the original stack level
5252 that was executing when you gave the @code{next} command. This command
5253 is abbreviated @code{n}.
5255 An argument @var{count} is a repeat count, as for @code{step}.
5258 @c FIX ME!! Do we delete this, or is there a way it fits in with
5259 @c the following paragraph? --- Vctoria
5261 @c @code{next} within a function that lacks debugging information acts like
5262 @c @code{step}, but any function calls appearing within the code of the
5263 @c function are executed without stopping.
5265 The @code{next} command only stops at the first instruction of a
5266 source line. This prevents multiple stops that could otherwise occur in
5267 @code{switch} statements, @code{for} loops, etc.
5269 @kindex set step-mode
5271 @cindex functions without line info, and stepping
5272 @cindex stepping into functions with no line info
5273 @itemx set step-mode on
5274 The @code{set step-mode on} command causes the @code{step} command to
5275 stop at the first instruction of a function which contains no debug line
5276 information rather than stepping over it.
5278 This is useful in cases where you may be interested in inspecting the
5279 machine instructions of a function which has no symbolic info and do not
5280 want @value{GDBN} to automatically skip over this function.
5282 @item set step-mode off
5283 Causes the @code{step} command to step over any functions which contains no
5284 debug information. This is the default.
5286 @item show step-mode
5287 Show whether @value{GDBN} will stop in or step over functions without
5288 source line debug information.
5291 @kindex fin @r{(@code{finish})}
5293 Continue running until just after function in the selected stack frame
5294 returns. Print the returned value (if any). This command can be
5295 abbreviated as @code{fin}.
5297 Contrast this with the @code{return} command (@pxref{Returning,
5298 ,Returning from a Function}).
5301 @kindex u @r{(@code{until})}
5302 @cindex run until specified location
5305 Continue running until a source line past the current line, in the
5306 current stack frame, is reached. This command is used to avoid single
5307 stepping through a loop more than once. It is like the @code{next}
5308 command, except that when @code{until} encounters a jump, it
5309 automatically continues execution until the program counter is greater
5310 than the address of the jump.
5312 This means that when you reach the end of a loop after single stepping
5313 though it, @code{until} makes your program continue execution until it
5314 exits the loop. In contrast, a @code{next} command at the end of a loop
5315 simply steps back to the beginning of the loop, which forces you to step
5316 through the next iteration.
5318 @code{until} always stops your program if it attempts to exit the current
5321 @code{until} may produce somewhat counterintuitive results if the order
5322 of machine code does not match the order of the source lines. For
5323 example, in the following excerpt from a debugging session, the @code{f}
5324 (@code{frame}) command shows that execution is stopped at line
5325 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5329 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5331 (@value{GDBP}) until
5332 195 for ( ; argc > 0; NEXTARG) @{
5335 This happened because, for execution efficiency, the compiler had
5336 generated code for the loop closure test at the end, rather than the
5337 start, of the loop---even though the test in a C @code{for}-loop is
5338 written before the body of the loop. The @code{until} command appeared
5339 to step back to the beginning of the loop when it advanced to this
5340 expression; however, it has not really gone to an earlier
5341 statement---not in terms of the actual machine code.
5343 @code{until} with no argument works by means of single
5344 instruction stepping, and hence is slower than @code{until} with an
5347 @item until @var{location}
5348 @itemx u @var{location}
5349 Continue running your program until either the specified @var{location} is
5350 reached, or the current stack frame returns. The location is any of
5351 the forms described in @ref{Specify Location}.
5352 This form of the command uses temporary breakpoints, and
5353 hence is quicker than @code{until} without an argument. The specified
5354 location is actually reached only if it is in the current frame. This
5355 implies that @code{until} can be used to skip over recursive function
5356 invocations. For instance in the code below, if the current location is
5357 line @code{96}, issuing @code{until 99} will execute the program up to
5358 line @code{99} in the same invocation of factorial, i.e., after the inner
5359 invocations have returned.
5362 94 int factorial (int value)
5364 96 if (value > 1) @{
5365 97 value *= factorial (value - 1);
5372 @kindex advance @var{location}
5373 @item advance @var{location}
5374 Continue running the program up to the given @var{location}. An argument is
5375 required, which should be of one of the forms described in
5376 @ref{Specify Location}.
5377 Execution will also stop upon exit from the current stack
5378 frame. This command is similar to @code{until}, but @code{advance} will
5379 not skip over recursive function calls, and the target location doesn't
5380 have to be in the same frame as the current one.
5384 @kindex si @r{(@code{stepi})}
5386 @itemx stepi @var{arg}
5388 Execute one machine instruction, then stop and return to the debugger.
5390 It is often useful to do @samp{display/i $pc} when stepping by machine
5391 instructions. This makes @value{GDBN} automatically display the next
5392 instruction to be executed, each time your program stops. @xref{Auto
5393 Display,, Automatic Display}.
5395 An argument is a repeat count, as in @code{step}.
5399 @kindex ni @r{(@code{nexti})}
5401 @itemx nexti @var{arg}
5403 Execute one machine instruction, but if it is a function call,
5404 proceed until the function returns.
5406 An argument is a repeat count, as in @code{next}.
5410 @anchor{range stepping}
5411 @cindex range stepping
5412 @cindex target-assisted range stepping
5413 By default, and if available, @value{GDBN} makes use of
5414 target-assisted @dfn{range stepping}. In other words, whenever you
5415 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5416 tells the target to step the corresponding range of instruction
5417 addresses instead of issuing multiple single-steps. This speeds up
5418 line stepping, particularly for remote targets. Ideally, there should
5419 be no reason you would want to turn range stepping off. However, it's
5420 possible that a bug in the debug info, a bug in the remote stub (for
5421 remote targets), or even a bug in @value{GDBN} could make line
5422 stepping behave incorrectly when target-assisted range stepping is
5423 enabled. You can use the following command to turn off range stepping
5427 @kindex set range-stepping
5428 @kindex show range-stepping
5429 @item set range-stepping
5430 @itemx show range-stepping
5431 Control whether range stepping is enabled.
5433 If @code{on}, and the target supports it, @value{GDBN} tells the
5434 target to step a range of addresses itself, instead of issuing
5435 multiple single-steps. If @code{off}, @value{GDBN} always issues
5436 single-steps, even if range stepping is supported by the target. The
5437 default is @code{on}.
5441 @node Skipping Over Functions and Files
5442 @section Skipping Over Functions and Files
5443 @cindex skipping over functions and files
5445 The program you are debugging may contain some functions which are
5446 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
5447 skip a function or all functions in a file when stepping.
5449 For example, consider the following C function:
5460 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5461 are not interested in stepping through @code{boring}. If you run @code{step}
5462 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5463 step over both @code{foo} and @code{boring}!
5465 One solution is to @code{step} into @code{boring} and use the @code{finish}
5466 command to immediately exit it. But this can become tedious if @code{boring}
5467 is called from many places.
5469 A more flexible solution is to execute @kbd{skip boring}. This instructs
5470 @value{GDBN} never to step into @code{boring}. Now when you execute
5471 @code{step} at line 103, you'll step over @code{boring} and directly into
5474 You can also instruct @value{GDBN} to skip all functions in a file, with, for
5475 example, @code{skip file boring.c}.
5478 @kindex skip function
5479 @item skip @r{[}@var{linespec}@r{]}
5480 @itemx skip function @r{[}@var{linespec}@r{]}
5481 After running this command, the function named by @var{linespec} or the
5482 function containing the line named by @var{linespec} will be skipped over when
5483 stepping. @xref{Specify Location}.
5485 If you do not specify @var{linespec}, the function you're currently debugging
5488 (If you have a function called @code{file} that you want to skip, use
5489 @kbd{skip function file}.)
5492 @item skip file @r{[}@var{filename}@r{]}
5493 After running this command, any function whose source lives in @var{filename}
5494 will be skipped over when stepping.
5496 If you do not specify @var{filename}, functions whose source lives in the file
5497 you're currently debugging will be skipped.
5500 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5501 These are the commands for managing your list of skips:
5505 @item info skip @r{[}@var{range}@r{]}
5506 Print details about the specified skip(s). If @var{range} is not specified,
5507 print a table with details about all functions and files marked for skipping.
5508 @code{info skip} prints the following information about each skip:
5512 A number identifying this skip.
5514 The type of this skip, either @samp{function} or @samp{file}.
5515 @item Enabled or Disabled
5516 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
5518 For function skips, this column indicates the address in memory of the function
5519 being skipped. If you've set a function skip on a function which has not yet
5520 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
5521 which has the function is loaded, @code{info skip} will show the function's
5524 For file skips, this field contains the filename being skipped. For functions
5525 skips, this field contains the function name and its line number in the file
5526 where it is defined.
5530 @item skip delete @r{[}@var{range}@r{]}
5531 Delete the specified skip(s). If @var{range} is not specified, delete all
5535 @item skip enable @r{[}@var{range}@r{]}
5536 Enable the specified skip(s). If @var{range} is not specified, enable all
5539 @kindex skip disable
5540 @item skip disable @r{[}@var{range}@r{]}
5541 Disable the specified skip(s). If @var{range} is not specified, disable all
5550 A signal is an asynchronous event that can happen in a program. The
5551 operating system defines the possible kinds of signals, and gives each
5552 kind a name and a number. For example, in Unix @code{SIGINT} is the
5553 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5554 @code{SIGSEGV} is the signal a program gets from referencing a place in
5555 memory far away from all the areas in use; @code{SIGALRM} occurs when
5556 the alarm clock timer goes off (which happens only if your program has
5557 requested an alarm).
5559 @cindex fatal signals
5560 Some signals, including @code{SIGALRM}, are a normal part of the
5561 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5562 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5563 program has not specified in advance some other way to handle the signal.
5564 @code{SIGINT} does not indicate an error in your program, but it is normally
5565 fatal so it can carry out the purpose of the interrupt: to kill the program.
5567 @value{GDBN} has the ability to detect any occurrence of a signal in your
5568 program. You can tell @value{GDBN} in advance what to do for each kind of
5571 @cindex handling signals
5572 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5573 @code{SIGALRM} be silently passed to your program
5574 (so as not to interfere with their role in the program's functioning)
5575 but to stop your program immediately whenever an error signal happens.
5576 You can change these settings with the @code{handle} command.
5579 @kindex info signals
5583 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5584 handle each one. You can use this to see the signal numbers of all
5585 the defined types of signals.
5587 @item info signals @var{sig}
5588 Similar, but print information only about the specified signal number.
5590 @code{info handle} is an alias for @code{info signals}.
5592 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5593 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5594 for details about this command.
5597 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5598 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
5599 can be the number of a signal or its name (with or without the
5600 @samp{SIG} at the beginning); a list of signal numbers of the form
5601 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5602 known signals. Optional arguments @var{keywords}, described below,
5603 say what change to make.
5607 The keywords allowed by the @code{handle} command can be abbreviated.
5608 Their full names are:
5612 @value{GDBN} should not stop your program when this signal happens. It may
5613 still print a message telling you that the signal has come in.
5616 @value{GDBN} should stop your program when this signal happens. This implies
5617 the @code{print} keyword as well.
5620 @value{GDBN} should print a message when this signal happens.
5623 @value{GDBN} should not mention the occurrence of the signal at all. This
5624 implies the @code{nostop} keyword as well.
5628 @value{GDBN} should allow your program to see this signal; your program
5629 can handle the signal, or else it may terminate if the signal is fatal
5630 and not handled. @code{pass} and @code{noignore} are synonyms.
5634 @value{GDBN} should not allow your program to see this signal.
5635 @code{nopass} and @code{ignore} are synonyms.
5639 When a signal stops your program, the signal is not visible to the
5641 continue. Your program sees the signal then, if @code{pass} is in
5642 effect for the signal in question @emph{at that time}. In other words,
5643 after @value{GDBN} reports a signal, you can use the @code{handle}
5644 command with @code{pass} or @code{nopass} to control whether your
5645 program sees that signal when you continue.
5647 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5648 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5649 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5652 You can also use the @code{signal} command to prevent your program from
5653 seeing a signal, or cause it to see a signal it normally would not see,
5654 or to give it any signal at any time. For example, if your program stopped
5655 due to some sort of memory reference error, you might store correct
5656 values into the erroneous variables and continue, hoping to see more
5657 execution; but your program would probably terminate immediately as
5658 a result of the fatal signal once it saw the signal. To prevent this,
5659 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5662 @cindex stepping and signal handlers
5663 @anchor{stepping and signal handlers}
5665 @value{GDBN} optimizes for stepping the mainline code. If a signal
5666 that has @code{handle nostop} and @code{handle pass} set arrives while
5667 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
5668 in progress, @value{GDBN} lets the signal handler run and then resumes
5669 stepping the mainline code once the signal handler returns. In other
5670 words, @value{GDBN} steps over the signal handler. This prevents
5671 signals that you've specified as not interesting (with @code{handle
5672 nostop}) from changing the focus of debugging unexpectedly. Note that
5673 the signal handler itself may still hit a breakpoint, stop for another
5674 signal that has @code{handle stop} in effect, or for any other event
5675 that normally results in stopping the stepping command sooner. Also
5676 note that @value{GDBN} still informs you that the program received a
5677 signal if @code{handle print} is set.
5679 @anchor{stepping into signal handlers}
5681 If you set @code{handle pass} for a signal, and your program sets up a
5682 handler for it, then issuing a stepping command, such as @code{step}
5683 or @code{stepi}, when your program is stopped due to the signal will
5684 step @emph{into} the signal handler (if the target supports that).
5686 Likewise, if you use the @code{queue-signal} command to queue a signal
5687 to be delivered to the current thread when execution of the thread
5688 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
5689 stepping command will step into the signal handler.
5691 Here's an example, using @code{stepi} to step to the first instruction
5692 of @code{SIGUSR1}'s handler:
5695 (@value{GDBP}) handle SIGUSR1
5696 Signal Stop Print Pass to program Description
5697 SIGUSR1 Yes Yes Yes User defined signal 1
5701 Program received signal SIGUSR1, User defined signal 1.
5702 main () sigusr1.c:28
5705 sigusr1_handler () at sigusr1.c:9
5709 The same, but using @code{queue-signal} instead of waiting for the
5710 program to receive the signal first:
5715 (@value{GDBP}) queue-signal SIGUSR1
5717 sigusr1_handler () at sigusr1.c:9
5722 @cindex extra signal information
5723 @anchor{extra signal information}
5725 On some targets, @value{GDBN} can inspect extra signal information
5726 associated with the intercepted signal, before it is actually
5727 delivered to the program being debugged. This information is exported
5728 by the convenience variable @code{$_siginfo}, and consists of data
5729 that is passed by the kernel to the signal handler at the time of the
5730 receipt of a signal. The data type of the information itself is
5731 target dependent. You can see the data type using the @code{ptype
5732 $_siginfo} command. On Unix systems, it typically corresponds to the
5733 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5736 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5737 referenced address that raised a segmentation fault.
5741 (@value{GDBP}) continue
5742 Program received signal SIGSEGV, Segmentation fault.
5743 0x0000000000400766 in main ()
5745 (@value{GDBP}) ptype $_siginfo
5752 struct @{...@} _kill;
5753 struct @{...@} _timer;
5755 struct @{...@} _sigchld;
5756 struct @{...@} _sigfault;
5757 struct @{...@} _sigpoll;
5760 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5764 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5765 $1 = (void *) 0x7ffff7ff7000
5769 Depending on target support, @code{$_siginfo} may also be writable.
5772 @section Stopping and Starting Multi-thread Programs
5774 @cindex stopped threads
5775 @cindex threads, stopped
5777 @cindex continuing threads
5778 @cindex threads, continuing
5780 @value{GDBN} supports debugging programs with multiple threads
5781 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5782 are two modes of controlling execution of your program within the
5783 debugger. In the default mode, referred to as @dfn{all-stop mode},
5784 when any thread in your program stops (for example, at a breakpoint
5785 or while being stepped), all other threads in the program are also stopped by
5786 @value{GDBN}. On some targets, @value{GDBN} also supports
5787 @dfn{non-stop mode}, in which other threads can continue to run freely while
5788 you examine the stopped thread in the debugger.
5791 * All-Stop Mode:: All threads stop when GDB takes control
5792 * Non-Stop Mode:: Other threads continue to execute
5793 * Background Execution:: Running your program asynchronously
5794 * Thread-Specific Breakpoints:: Controlling breakpoints
5795 * Interrupted System Calls:: GDB may interfere with system calls
5796 * Observer Mode:: GDB does not alter program behavior
5800 @subsection All-Stop Mode
5802 @cindex all-stop mode
5804 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5805 @emph{all} threads of execution stop, not just the current thread. This
5806 allows you to examine the overall state of the program, including
5807 switching between threads, without worrying that things may change
5810 Conversely, whenever you restart the program, @emph{all} threads start
5811 executing. @emph{This is true even when single-stepping} with commands
5812 like @code{step} or @code{next}.
5814 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5815 Since thread scheduling is up to your debugging target's operating
5816 system (not controlled by @value{GDBN}), other threads may
5817 execute more than one statement while the current thread completes a
5818 single step. Moreover, in general other threads stop in the middle of a
5819 statement, rather than at a clean statement boundary, when the program
5822 You might even find your program stopped in another thread after
5823 continuing or even single-stepping. This happens whenever some other
5824 thread runs into a breakpoint, a signal, or an exception before the
5825 first thread completes whatever you requested.
5827 @cindex automatic thread selection
5828 @cindex switching threads automatically
5829 @cindex threads, automatic switching
5830 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5831 signal, it automatically selects the thread where that breakpoint or
5832 signal happened. @value{GDBN} alerts you to the context switch with a
5833 message such as @samp{[Switching to Thread @var{n}]} to identify the
5836 On some OSes, you can modify @value{GDBN}'s default behavior by
5837 locking the OS scheduler to allow only a single thread to run.
5840 @item set scheduler-locking @var{mode}
5841 @cindex scheduler locking mode
5842 @cindex lock scheduler
5843 Set the scheduler locking mode. If it is @code{off}, then there is no
5844 locking and any thread may run at any time. If @code{on}, then only the
5845 current thread may run when the inferior is resumed. The @code{step}
5846 mode optimizes for single-stepping; it prevents other threads
5847 from preempting the current thread while you are stepping, so that
5848 the focus of debugging does not change unexpectedly.
5849 Other threads only rarely (or never) get a chance to run
5850 when you step. They are more likely to run when you @samp{next} over a
5851 function call, and they are completely free to run when you use commands
5852 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5853 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5854 the current thread away from the thread that you are debugging.
5856 @item show scheduler-locking
5857 Display the current scheduler locking mode.
5860 @cindex resume threads of multiple processes simultaneously
5861 By default, when you issue one of the execution commands such as
5862 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5863 threads of the current inferior to run. For example, if @value{GDBN}
5864 is attached to two inferiors, each with two threads, the
5865 @code{continue} command resumes only the two threads of the current
5866 inferior. This is useful, for example, when you debug a program that
5867 forks and you want to hold the parent stopped (so that, for instance,
5868 it doesn't run to exit), while you debug the child. In other
5869 situations, you may not be interested in inspecting the current state
5870 of any of the processes @value{GDBN} is attached to, and you may want
5871 to resume them all until some breakpoint is hit. In the latter case,
5872 you can instruct @value{GDBN} to allow all threads of all the
5873 inferiors to run with the @w{@code{set schedule-multiple}} command.
5876 @kindex set schedule-multiple
5877 @item set schedule-multiple
5878 Set the mode for allowing threads of multiple processes to be resumed
5879 when an execution command is issued. When @code{on}, all threads of
5880 all processes are allowed to run. When @code{off}, only the threads
5881 of the current process are resumed. The default is @code{off}. The
5882 @code{scheduler-locking} mode takes precedence when set to @code{on},
5883 or while you are stepping and set to @code{step}.
5885 @item show schedule-multiple
5886 Display the current mode for resuming the execution of threads of
5891 @subsection Non-Stop Mode
5893 @cindex non-stop mode
5895 @c This section is really only a place-holder, and needs to be expanded
5896 @c with more details.
5898 For some multi-threaded targets, @value{GDBN} supports an optional
5899 mode of operation in which you can examine stopped program threads in
5900 the debugger while other threads continue to execute freely. This
5901 minimizes intrusion when debugging live systems, such as programs
5902 where some threads have real-time constraints or must continue to
5903 respond to external events. This is referred to as @dfn{non-stop} mode.
5905 In non-stop mode, when a thread stops to report a debugging event,
5906 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5907 threads as well, in contrast to the all-stop mode behavior. Additionally,
5908 execution commands such as @code{continue} and @code{step} apply by default
5909 only to the current thread in non-stop mode, rather than all threads as
5910 in all-stop mode. This allows you to control threads explicitly in
5911 ways that are not possible in all-stop mode --- for example, stepping
5912 one thread while allowing others to run freely, stepping
5913 one thread while holding all others stopped, or stepping several threads
5914 independently and simultaneously.
5916 To enter non-stop mode, use this sequence of commands before you run
5917 or attach to your program:
5920 # If using the CLI, pagination breaks non-stop.
5923 # Finally, turn it on!
5927 You can use these commands to manipulate the non-stop mode setting:
5930 @kindex set non-stop
5931 @item set non-stop on
5932 Enable selection of non-stop mode.
5933 @item set non-stop off
5934 Disable selection of non-stop mode.
5935 @kindex show non-stop
5937 Show the current non-stop enablement setting.
5940 Note these commands only reflect whether non-stop mode is enabled,
5941 not whether the currently-executing program is being run in non-stop mode.
5942 In particular, the @code{set non-stop} preference is only consulted when
5943 @value{GDBN} starts or connects to the target program, and it is generally
5944 not possible to switch modes once debugging has started. Furthermore,
5945 since not all targets support non-stop mode, even when you have enabled
5946 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5949 In non-stop mode, all execution commands apply only to the current thread
5950 by default. That is, @code{continue} only continues one thread.
5951 To continue all threads, issue @code{continue -a} or @code{c -a}.
5953 You can use @value{GDBN}'s background execution commands
5954 (@pxref{Background Execution}) to run some threads in the background
5955 while you continue to examine or step others from @value{GDBN}.
5956 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5957 always executed asynchronously in non-stop mode.
5959 Suspending execution is done with the @code{interrupt} command when
5960 running in the background, or @kbd{Ctrl-c} during foreground execution.
5961 In all-stop mode, this stops the whole process;
5962 but in non-stop mode the interrupt applies only to the current thread.
5963 To stop the whole program, use @code{interrupt -a}.
5965 Other execution commands do not currently support the @code{-a} option.
5967 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5968 that thread current, as it does in all-stop mode. This is because the
5969 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5970 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5971 changed to a different thread just as you entered a command to operate on the
5972 previously current thread.
5974 @node Background Execution
5975 @subsection Background Execution
5977 @cindex foreground execution
5978 @cindex background execution
5979 @cindex asynchronous execution
5980 @cindex execution, foreground, background and asynchronous
5982 @value{GDBN}'s execution commands have two variants: the normal
5983 foreground (synchronous) behavior, and a background
5984 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5985 the program to report that some thread has stopped before prompting for
5986 another command. In background execution, @value{GDBN} immediately gives
5987 a command prompt so that you can issue other commands while your program runs.
5989 If the target doesn't support async mode, @value{GDBN} issues an error
5990 message if you attempt to use the background execution commands.
5992 To specify background execution, add a @code{&} to the command. For example,
5993 the background form of the @code{continue} command is @code{continue&}, or
5994 just @code{c&}. The execution commands that accept background execution
6000 @xref{Starting, , Starting your Program}.
6004 @xref{Attach, , Debugging an Already-running Process}.
6008 @xref{Continuing and Stepping, step}.
6012 @xref{Continuing and Stepping, stepi}.
6016 @xref{Continuing and Stepping, next}.
6020 @xref{Continuing and Stepping, nexti}.
6024 @xref{Continuing and Stepping, continue}.
6028 @xref{Continuing and Stepping, finish}.
6032 @xref{Continuing and Stepping, until}.
6036 Background execution is especially useful in conjunction with non-stop
6037 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
6038 However, you can also use these commands in the normal all-stop mode with
6039 the restriction that you cannot issue another execution command until the
6040 previous one finishes. Examples of commands that are valid in all-stop
6041 mode while the program is running include @code{help} and @code{info break}.
6043 You can interrupt your program while it is running in the background by
6044 using the @code{interrupt} command.
6051 Suspend execution of the running program. In all-stop mode,
6052 @code{interrupt} stops the whole process, but in non-stop mode, it stops
6053 only the current thread. To stop the whole program in non-stop mode,
6054 use @code{interrupt -a}.
6057 @node Thread-Specific Breakpoints
6058 @subsection Thread-Specific Breakpoints
6060 When your program has multiple threads (@pxref{Threads,, Debugging
6061 Programs with Multiple Threads}), you can choose whether to set
6062 breakpoints on all threads, or on a particular thread.
6065 @cindex breakpoints and threads
6066 @cindex thread breakpoints
6067 @kindex break @dots{} thread @var{threadno}
6068 @item break @var{linespec} thread @var{threadno}
6069 @itemx break @var{linespec} thread @var{threadno} if @dots{}
6070 @var{linespec} specifies source lines; there are several ways of
6071 writing them (@pxref{Specify Location}), but the effect is always to
6072 specify some source line.
6074 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
6075 to specify that you only want @value{GDBN} to stop the program when a
6076 particular thread reaches this breakpoint. The @var{threadno} specifier
6077 is one of the numeric thread identifiers assigned by @value{GDBN}, shown
6078 in the first column of the @samp{info threads} display.
6080 If you do not specify @samp{thread @var{threadno}} when you set a
6081 breakpoint, the breakpoint applies to @emph{all} threads of your
6084 You can use the @code{thread} qualifier on conditional breakpoints as
6085 well; in this case, place @samp{thread @var{threadno}} before or
6086 after the breakpoint condition, like this:
6089 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6094 Thread-specific breakpoints are automatically deleted when
6095 @value{GDBN} detects the corresponding thread is no longer in the
6096 thread list. For example:
6100 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6103 There are several ways for a thread to disappear, such as a regular
6104 thread exit, but also when you detach from the process with the
6105 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6106 Process}), or if @value{GDBN} loses the remote connection
6107 (@pxref{Remote Debugging}), etc. Note that with some targets,
6108 @value{GDBN} is only able to detect a thread has exited when the user
6109 explictly asks for the thread list with the @code{info threads}
6112 @node Interrupted System Calls
6113 @subsection Interrupted System Calls
6115 @cindex thread breakpoints and system calls
6116 @cindex system calls and thread breakpoints
6117 @cindex premature return from system calls
6118 There is an unfortunate side effect when using @value{GDBN} to debug
6119 multi-threaded programs. If one thread stops for a
6120 breakpoint, or for some other reason, and another thread is blocked in a
6121 system call, then the system call may return prematurely. This is a
6122 consequence of the interaction between multiple threads and the signals
6123 that @value{GDBN} uses to implement breakpoints and other events that
6126 To handle this problem, your program should check the return value of
6127 each system call and react appropriately. This is good programming
6130 For example, do not write code like this:
6136 The call to @code{sleep} will return early if a different thread stops
6137 at a breakpoint or for some other reason.
6139 Instead, write this:
6144 unslept = sleep (unslept);
6147 A system call is allowed to return early, so the system is still
6148 conforming to its specification. But @value{GDBN} does cause your
6149 multi-threaded program to behave differently than it would without
6152 Also, @value{GDBN} uses internal breakpoints in the thread library to
6153 monitor certain events such as thread creation and thread destruction.
6154 When such an event happens, a system call in another thread may return
6155 prematurely, even though your program does not appear to stop.
6158 @subsection Observer Mode
6160 If you want to build on non-stop mode and observe program behavior
6161 without any chance of disruption by @value{GDBN}, you can set
6162 variables to disable all of the debugger's attempts to modify state,
6163 whether by writing memory, inserting breakpoints, etc. These operate
6164 at a low level, intercepting operations from all commands.
6166 When all of these are set to @code{off}, then @value{GDBN} is said to
6167 be @dfn{observer mode}. As a convenience, the variable
6168 @code{observer} can be set to disable these, plus enable non-stop
6171 Note that @value{GDBN} will not prevent you from making nonsensical
6172 combinations of these settings. For instance, if you have enabled
6173 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6174 then breakpoints that work by writing trap instructions into the code
6175 stream will still not be able to be placed.
6180 @item set observer on
6181 @itemx set observer off
6182 When set to @code{on}, this disables all the permission variables
6183 below (except for @code{insert-fast-tracepoints}), plus enables
6184 non-stop debugging. Setting this to @code{off} switches back to
6185 normal debugging, though remaining in non-stop mode.
6188 Show whether observer mode is on or off.
6190 @kindex may-write-registers
6191 @item set may-write-registers on
6192 @itemx set may-write-registers off
6193 This controls whether @value{GDBN} will attempt to alter the values of
6194 registers, such as with assignment expressions in @code{print}, or the
6195 @code{jump} command. It defaults to @code{on}.
6197 @item show may-write-registers
6198 Show the current permission to write registers.
6200 @kindex may-write-memory
6201 @item set may-write-memory on
6202 @itemx set may-write-memory off
6203 This controls whether @value{GDBN} will attempt to alter the contents
6204 of memory, such as with assignment expressions in @code{print}. It
6205 defaults to @code{on}.
6207 @item show may-write-memory
6208 Show the current permission to write memory.
6210 @kindex may-insert-breakpoints
6211 @item set may-insert-breakpoints on
6212 @itemx set may-insert-breakpoints off
6213 This controls whether @value{GDBN} will attempt to insert breakpoints.
6214 This affects all breakpoints, including internal breakpoints defined
6215 by @value{GDBN}. It defaults to @code{on}.
6217 @item show may-insert-breakpoints
6218 Show the current permission to insert breakpoints.
6220 @kindex may-insert-tracepoints
6221 @item set may-insert-tracepoints on
6222 @itemx set may-insert-tracepoints off
6223 This controls whether @value{GDBN} will attempt to insert (regular)
6224 tracepoints at the beginning of a tracing experiment. It affects only
6225 non-fast tracepoints, fast tracepoints being under the control of
6226 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6228 @item show may-insert-tracepoints
6229 Show the current permission to insert tracepoints.
6231 @kindex may-insert-fast-tracepoints
6232 @item set may-insert-fast-tracepoints on
6233 @itemx set may-insert-fast-tracepoints off
6234 This controls whether @value{GDBN} will attempt to insert fast
6235 tracepoints at the beginning of a tracing experiment. It affects only
6236 fast tracepoints, regular (non-fast) tracepoints being under the
6237 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6239 @item show may-insert-fast-tracepoints
6240 Show the current permission to insert fast tracepoints.
6242 @kindex may-interrupt
6243 @item set may-interrupt on
6244 @itemx set may-interrupt off
6245 This controls whether @value{GDBN} will attempt to interrupt or stop
6246 program execution. When this variable is @code{off}, the
6247 @code{interrupt} command will have no effect, nor will
6248 @kbd{Ctrl-c}. It defaults to @code{on}.
6250 @item show may-interrupt
6251 Show the current permission to interrupt or stop the program.
6255 @node Reverse Execution
6256 @chapter Running programs backward
6257 @cindex reverse execution
6258 @cindex running programs backward
6260 When you are debugging a program, it is not unusual to realize that
6261 you have gone too far, and some event of interest has already happened.
6262 If the target environment supports it, @value{GDBN} can allow you to
6263 ``rewind'' the program by running it backward.
6265 A target environment that supports reverse execution should be able
6266 to ``undo'' the changes in machine state that have taken place as the
6267 program was executing normally. Variables, registers etc.@: should
6268 revert to their previous values. Obviously this requires a great
6269 deal of sophistication on the part of the target environment; not
6270 all target environments can support reverse execution.
6272 When a program is executed in reverse, the instructions that
6273 have most recently been executed are ``un-executed'', in reverse
6274 order. The program counter runs backward, following the previous
6275 thread of execution in reverse. As each instruction is ``un-executed'',
6276 the values of memory and/or registers that were changed by that
6277 instruction are reverted to their previous states. After executing
6278 a piece of source code in reverse, all side effects of that code
6279 should be ``undone'', and all variables should be returned to their
6280 prior values@footnote{
6281 Note that some side effects are easier to undo than others. For instance,
6282 memory and registers are relatively easy, but device I/O is hard. Some
6283 targets may be able undo things like device I/O, and some may not.
6285 The contract between @value{GDBN} and the reverse executing target
6286 requires only that the target do something reasonable when
6287 @value{GDBN} tells it to execute backwards, and then report the
6288 results back to @value{GDBN}. Whatever the target reports back to
6289 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6290 assumes that the memory and registers that the target reports are in a
6291 consistant state, but @value{GDBN} accepts whatever it is given.
6294 If you are debugging in a target environment that supports
6295 reverse execution, @value{GDBN} provides the following commands.
6298 @kindex reverse-continue
6299 @kindex rc @r{(@code{reverse-continue})}
6300 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6301 @itemx rc @r{[}@var{ignore-count}@r{]}
6302 Beginning at the point where your program last stopped, start executing
6303 in reverse. Reverse execution will stop for breakpoints and synchronous
6304 exceptions (signals), just like normal execution. Behavior of
6305 asynchronous signals depends on the target environment.
6307 @kindex reverse-step
6308 @kindex rs @r{(@code{step})}
6309 @item reverse-step @r{[}@var{count}@r{]}
6310 Run the program backward until control reaches the start of a
6311 different source line; then stop it, and return control to @value{GDBN}.
6313 Like the @code{step} command, @code{reverse-step} will only stop
6314 at the beginning of a source line. It ``un-executes'' the previously
6315 executed source line. If the previous source line included calls to
6316 debuggable functions, @code{reverse-step} will step (backward) into
6317 the called function, stopping at the beginning of the @emph{last}
6318 statement in the called function (typically a return statement).
6320 Also, as with the @code{step} command, if non-debuggable functions are
6321 called, @code{reverse-step} will run thru them backward without stopping.
6323 @kindex reverse-stepi
6324 @kindex rsi @r{(@code{reverse-stepi})}
6325 @item reverse-stepi @r{[}@var{count}@r{]}
6326 Reverse-execute one machine instruction. Note that the instruction
6327 to be reverse-executed is @emph{not} the one pointed to by the program
6328 counter, but the instruction executed prior to that one. For instance,
6329 if the last instruction was a jump, @code{reverse-stepi} will take you
6330 back from the destination of the jump to the jump instruction itself.
6332 @kindex reverse-next
6333 @kindex rn @r{(@code{reverse-next})}
6334 @item reverse-next @r{[}@var{count}@r{]}
6335 Run backward to the beginning of the previous line executed in
6336 the current (innermost) stack frame. If the line contains function
6337 calls, they will be ``un-executed'' without stopping. Starting from
6338 the first line of a function, @code{reverse-next} will take you back
6339 to the caller of that function, @emph{before} the function was called,
6340 just as the normal @code{next} command would take you from the last
6341 line of a function back to its return to its caller
6342 @footnote{Unless the code is too heavily optimized.}.
6344 @kindex reverse-nexti
6345 @kindex rni @r{(@code{reverse-nexti})}
6346 @item reverse-nexti @r{[}@var{count}@r{]}
6347 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6348 in reverse, except that called functions are ``un-executed'' atomically.
6349 That is, if the previously executed instruction was a return from
6350 another function, @code{reverse-nexti} will continue to execute
6351 in reverse until the call to that function (from the current stack
6354 @kindex reverse-finish
6355 @item reverse-finish
6356 Just as the @code{finish} command takes you to the point where the
6357 current function returns, @code{reverse-finish} takes you to the point
6358 where it was called. Instead of ending up at the end of the current
6359 function invocation, you end up at the beginning.
6361 @kindex set exec-direction
6362 @item set exec-direction
6363 Set the direction of target execution.
6364 @item set exec-direction reverse
6365 @cindex execute forward or backward in time
6366 @value{GDBN} will perform all execution commands in reverse, until the
6367 exec-direction mode is changed to ``forward''. Affected commands include
6368 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6369 command cannot be used in reverse mode.
6370 @item set exec-direction forward
6371 @value{GDBN} will perform all execution commands in the normal fashion.
6372 This is the default.
6376 @node Process Record and Replay
6377 @chapter Recording Inferior's Execution and Replaying It
6378 @cindex process record and replay
6379 @cindex recording inferior's execution and replaying it
6381 On some platforms, @value{GDBN} provides a special @dfn{process record
6382 and replay} target that can record a log of the process execution, and
6383 replay it later with both forward and reverse execution commands.
6386 When this target is in use, if the execution log includes the record
6387 for the next instruction, @value{GDBN} will debug in @dfn{replay
6388 mode}. In the replay mode, the inferior does not really execute code
6389 instructions. Instead, all the events that normally happen during
6390 code execution are taken from the execution log. While code is not
6391 really executed in replay mode, the values of registers (including the
6392 program counter register) and the memory of the inferior are still
6393 changed as they normally would. Their contents are taken from the
6397 If the record for the next instruction is not in the execution log,
6398 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6399 inferior executes normally, and @value{GDBN} records the execution log
6402 The process record and replay target supports reverse execution
6403 (@pxref{Reverse Execution}), even if the platform on which the
6404 inferior runs does not. However, the reverse execution is limited in
6405 this case by the range of the instructions recorded in the execution
6406 log. In other words, reverse execution on platforms that don't
6407 support it directly can only be done in the replay mode.
6409 When debugging in the reverse direction, @value{GDBN} will work in
6410 replay mode as long as the execution log includes the record for the
6411 previous instruction; otherwise, it will work in record mode, if the
6412 platform supports reverse execution, or stop if not.
6414 For architecture environments that support process record and replay,
6415 @value{GDBN} provides the following commands:
6418 @kindex target record
6419 @kindex target record-full
6420 @kindex target record-btrace
6423 @kindex record btrace
6424 @kindex record btrace bts
6429 @kindex rec btrace bts
6431 @item record @var{method}
6432 This command starts the process record and replay target. The
6433 recording method can be specified as parameter. Without a parameter
6434 the command uses the @code{full} recording method. The following
6435 recording methods are available:
6439 Full record/replay recording using @value{GDBN}'s software record and
6440 replay implementation. This method allows replaying and reverse
6443 @item btrace @var{format}
6444 Hardware-supported instruction recording. This method does not record
6445 data. Further, the data is collected in a ring buffer so old data will
6446 be overwritten when the buffer is full. It allows limited replay and
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 Not all recording formats may be available on all processors.
6464 The process record and replay target can only debug a process that is
6465 already running. Therefore, you need first to start the process with
6466 the @kbd{run} or @kbd{start} commands, and then start the recording
6467 with the @kbd{record @var{method}} command.
6469 Both @code{record @var{method}} and @code{rec @var{method}} are
6470 aliases of @code{target record-@var{method}}.
6472 @cindex displaced stepping, and process record and replay
6473 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6474 will be automatically disabled when process record and replay target
6475 is started. That's because the process record and replay target
6476 doesn't support displaced stepping.
6478 @cindex non-stop mode, and process record and replay
6479 @cindex asynchronous execution, and process record and replay
6480 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6481 the asynchronous execution mode (@pxref{Background Execution}), not
6482 all recording methods are available. The @code{full} recording method
6483 does not support these two modes.
6488 Stop the process record and replay target. When process record and
6489 replay target stops, the entire execution log will be deleted and the
6490 inferior will either be terminated, or will remain in its final state.
6492 When you stop the process record and replay target in record mode (at
6493 the end of the execution log), the inferior will be stopped at the
6494 next instruction that would have been recorded. In other words, if
6495 you record for a while and then stop recording, the inferior process
6496 will be left in the same state as if the recording never happened.
6498 On the other hand, if the process record and replay target is stopped
6499 while in replay mode (that is, not at the end of the execution log,
6500 but at some earlier point), the inferior process will become ``live''
6501 at that earlier state, and it will then be possible to continue the
6502 usual ``live'' debugging of the process from that state.
6504 When the inferior process exits, or @value{GDBN} detaches from it,
6505 process record and replay target will automatically stop itself.
6509 Go to a specific location in the execution log. There are several
6510 ways to specify the location to go to:
6513 @item record goto begin
6514 @itemx record goto start
6515 Go to the beginning of the execution log.
6517 @item record goto end
6518 Go to the end of the execution log.
6520 @item record goto @var{n}
6521 Go to instruction number @var{n} in the execution log.
6525 @item record save @var{filename}
6526 Save the execution log to a file @file{@var{filename}}.
6527 Default filename is @file{gdb_record.@var{process_id}}, where
6528 @var{process_id} is the process ID of the inferior.
6530 This command may not be available for all recording methods.
6532 @kindex record restore
6533 @item record restore @var{filename}
6534 Restore the execution log from a file @file{@var{filename}}.
6535 File must have been created with @code{record save}.
6537 @kindex set record full
6538 @item set record full insn-number-max @var{limit}
6539 @itemx set record full insn-number-max unlimited
6540 Set the limit of instructions to be recorded for the @code{full}
6541 recording method. Default value is 200000.
6543 If @var{limit} is a positive number, then @value{GDBN} will start
6544 deleting instructions from the log once the number of the record
6545 instructions becomes greater than @var{limit}. For every new recorded
6546 instruction, @value{GDBN} will delete the earliest recorded
6547 instruction to keep the number of recorded instructions at the limit.
6548 (Since deleting recorded instructions loses information, @value{GDBN}
6549 lets you control what happens when the limit is reached, by means of
6550 the @code{stop-at-limit} option, described below.)
6552 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6553 delete recorded instructions from the execution log. The number of
6554 recorded instructions is limited only by the available memory.
6556 @kindex show record full
6557 @item show record full insn-number-max
6558 Show the limit of instructions to be recorded with the @code{full}
6561 @item set record full stop-at-limit
6562 Control the behavior of the @code{full} recording method when the
6563 number of recorded instructions reaches the limit. If ON (the
6564 default), @value{GDBN} will stop when the limit is reached for the
6565 first time and ask you whether you want to stop the inferior or
6566 continue running it and recording the execution log. If you decide
6567 to continue recording, each new recorded instruction will cause the
6568 oldest one to be deleted.
6570 If this option is OFF, @value{GDBN} will automatically delete the
6571 oldest record to make room for each new one, without asking.
6573 @item show record full stop-at-limit
6574 Show the current setting of @code{stop-at-limit}.
6576 @item set record full memory-query
6577 Control the behavior when @value{GDBN} is unable to record memory
6578 changes caused by an instruction for the @code{full} recording method.
6579 If ON, @value{GDBN} will query whether to stop the inferior in that
6582 If this option is OFF (the default), @value{GDBN} will automatically
6583 ignore the effect of such instructions on memory. Later, when
6584 @value{GDBN} replays this execution log, it will mark the log of this
6585 instruction as not accessible, and it will not affect the replay
6588 @item show record full memory-query
6589 Show the current setting of @code{memory-query}.
6591 @kindex set record btrace
6592 The @code{btrace} record target does not trace data. As a
6593 convenience, when replaying, @value{GDBN} reads read-only memory off
6594 the live program directly, assuming that the addresses of the
6595 read-only areas don't change. This for example makes it possible to
6596 disassemble code while replaying, but not to print variables.
6597 In some cases, being able to inspect variables might be useful.
6598 You can use the following command for that:
6600 @item set record btrace replay-memory-access
6601 Control the behavior of the @code{btrace} recording method when
6602 accessing memory during replay. If @code{read-only} (the default),
6603 @value{GDBN} will only allow accesses to read-only memory.
6604 If @code{read-write}, @value{GDBN} will allow accesses to read-only
6605 and to read-write memory. Beware that the accessed memory corresponds
6606 to the live target and not necessarily to the current replay
6609 @kindex show record btrace
6610 @item show record btrace replay-memory-access
6611 Show the current setting of @code{replay-memory-access}.
6613 @kindex set record btrace bts
6614 @item set record btrace bts buffer-size @var{size}
6615 @itemx set record btrace bts buffer-size unlimited
6616 Set the requested ring buffer size for branch tracing in @acronym{BTS}
6617 format. Default is 64KB.
6619 If @var{size} is a positive number, then @value{GDBN} will try to
6620 allocate a buffer of at least @var{size} bytes for each new thread
6621 that uses the btrace recording method and the @acronym{BTS} format.
6622 The actually obtained buffer size may differ from the requested
6623 @var{size}. Use the @code{info record} command to see the actual
6624 buffer size for each thread that uses the btrace recording method and
6625 the @acronym{BTS} format.
6627 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6628 allocate a buffer of 4MB.
6630 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6631 also need longer to process the branch trace data before it can be used.
6633 @item show record btrace bts buffer-size @var{size}
6634 Show the current setting of the requested ring buffer size for branch
6635 tracing in @acronym{BTS} format.
6639 Show various statistics about the recording depending on the recording
6644 For the @code{full} recording method, it shows the state of process
6645 record and its in-memory execution log buffer, including:
6649 Whether in record mode or replay mode.
6651 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6653 Highest recorded instruction number.
6655 Current instruction about to be replayed (if in replay mode).
6657 Number of instructions contained in the execution log.
6659 Maximum number of instructions that may be contained in the execution log.
6663 For the @code{btrace} recording method, it shows:
6669 Number of instructions that have been recorded.
6671 Number of blocks of sequential control-flow formed by the recorded
6674 Whether in record mode or replay mode.
6677 For the @code{bts} recording format, it also shows:
6680 Size of the perf ring buffer.
6684 @kindex record delete
6687 When record target runs in replay mode (``in the past''), delete the
6688 subsequent execution log and begin to record a new execution log starting
6689 from the current address. This means you will abandon the previously
6690 recorded ``future'' and begin recording a new ``future''.
6692 @kindex record instruction-history
6693 @kindex rec instruction-history
6694 @item record instruction-history
6695 Disassembles instructions from the recorded execution log. By
6696 default, ten instructions are disassembled. This can be changed using
6697 the @code{set record instruction-history-size} command. Instructions
6698 are printed in execution order. There are several ways to specify
6699 what part of the execution log to disassemble:
6702 @item record instruction-history @var{insn}
6703 Disassembles ten instructions starting from instruction number
6706 @item record instruction-history @var{insn}, +/-@var{n}
6707 Disassembles @var{n} instructions around instruction number
6708 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
6709 @var{n} instructions after instruction number @var{insn}. If
6710 @var{n} is preceded with @code{-}, disassembles @var{n}
6711 instructions before instruction number @var{insn}.
6713 @item record instruction-history
6714 Disassembles ten more instructions after the last disassembly.
6716 @item record instruction-history -
6717 Disassembles ten more instructions before the last disassembly.
6719 @item record instruction-history @var{begin} @var{end}
6720 Disassembles instructions beginning with instruction number
6721 @var{begin} until instruction number @var{end}. The instruction
6722 number @var{end} is included.
6725 This command may not be available for all recording methods.
6728 @item set record instruction-history-size @var{size}
6729 @itemx set record instruction-history-size unlimited
6730 Define how many instructions to disassemble in the @code{record
6731 instruction-history} command. The default value is 10.
6732 A @var{size} of @code{unlimited} means unlimited instructions.
6735 @item show record instruction-history-size
6736 Show how many instructions to disassemble in the @code{record
6737 instruction-history} command.
6739 @kindex record function-call-history
6740 @kindex rec function-call-history
6741 @item record function-call-history
6742 Prints the execution history at function granularity. It prints one
6743 line for each sequence of instructions that belong to the same
6744 function giving the name of that function, the source lines
6745 for this instruction sequence (if the @code{/l} modifier is
6746 specified), and the instructions numbers that form the sequence (if
6747 the @code{/i} modifier is specified). The function names are indented
6748 to reflect the call stack depth if the @code{/c} modifier is
6749 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
6753 (@value{GDBP}) @b{list 1, 10}
6764 (@value{GDBP}) @b{record function-call-history /ilc}
6765 1 bar inst 1,4 at foo.c:6,8
6766 2 foo inst 5,10 at foo.c:2,3
6767 3 bar inst 11,13 at foo.c:9,10
6770 By default, ten lines are printed. This can be changed using the
6771 @code{set record function-call-history-size} command. Functions are
6772 printed in execution order. There are several ways to specify what
6776 @item record function-call-history @var{func}
6777 Prints ten functions starting from function number @var{func}.
6779 @item record function-call-history @var{func}, +/-@var{n}
6780 Prints @var{n} functions around function number @var{func}. If
6781 @var{n} is preceded with @code{+}, prints @var{n} functions after
6782 function number @var{func}. If @var{n} is preceded with @code{-},
6783 prints @var{n} functions before function number @var{func}.
6785 @item record function-call-history
6786 Prints ten more functions after the last ten-line print.
6788 @item record function-call-history -
6789 Prints ten more functions before the last ten-line print.
6791 @item record function-call-history @var{begin} @var{end}
6792 Prints functions beginning with function number @var{begin} until
6793 function number @var{end}. The function number @var{end} is included.
6796 This command may not be available for all recording methods.
6798 @item set record function-call-history-size @var{size}
6799 @itemx set record function-call-history-size unlimited
6800 Define how many lines to print in the
6801 @code{record function-call-history} command. The default value is 10.
6802 A size of @code{unlimited} means unlimited lines.
6804 @item show record function-call-history-size
6805 Show how many lines to print in the
6806 @code{record function-call-history} command.
6811 @chapter Examining the Stack
6813 When your program has stopped, the first thing you need to know is where it
6814 stopped and how it got there.
6817 Each time your program performs a function call, information about the call
6819 That information includes the location of the call in your program,
6820 the arguments of the call,
6821 and the local variables of the function being called.
6822 The information is saved in a block of data called a @dfn{stack frame}.
6823 The stack frames are allocated in a region of memory called the @dfn{call
6826 When your program stops, the @value{GDBN} commands for examining the
6827 stack allow you to see all of this information.
6829 @cindex selected frame
6830 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6831 @value{GDBN} commands refer implicitly to the selected frame. In
6832 particular, whenever you ask @value{GDBN} for the value of a variable in
6833 your program, the value is found in the selected frame. There are
6834 special @value{GDBN} commands to select whichever frame you are
6835 interested in. @xref{Selection, ,Selecting a Frame}.
6837 When your program stops, @value{GDBN} automatically selects the
6838 currently executing frame and describes it briefly, similar to the
6839 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6842 * Frames:: Stack frames
6843 * Backtrace:: Backtraces
6844 * Frame Filter Management:: Managing frame filters
6845 * Selection:: Selecting a frame
6846 * Frame Info:: Information on a frame
6851 @section Stack Frames
6853 @cindex frame, definition
6855 The call stack is divided up into contiguous pieces called @dfn{stack
6856 frames}, or @dfn{frames} for short; each frame is the data associated
6857 with one call to one function. The frame contains the arguments given
6858 to the function, the function's local variables, and the address at
6859 which the function is executing.
6861 @cindex initial frame
6862 @cindex outermost frame
6863 @cindex innermost frame
6864 When your program is started, the stack has only one frame, that of the
6865 function @code{main}. This is called the @dfn{initial} frame or the
6866 @dfn{outermost} frame. Each time a function is called, a new frame is
6867 made. Each time a function returns, the frame for that function invocation
6868 is eliminated. If a function is recursive, there can be many frames for
6869 the same function. The frame for the function in which execution is
6870 actually occurring is called the @dfn{innermost} frame. This is the most
6871 recently created of all the stack frames that still exist.
6873 @cindex frame pointer
6874 Inside your program, stack frames are identified by their addresses. A
6875 stack frame consists of many bytes, each of which has its own address; each
6876 kind of computer has a convention for choosing one byte whose
6877 address serves as the address of the frame. Usually this address is kept
6878 in a register called the @dfn{frame pointer register}
6879 (@pxref{Registers, $fp}) while execution is going on in that frame.
6881 @cindex frame number
6882 @value{GDBN} assigns numbers to all existing stack frames, starting with
6883 zero for the innermost frame, one for the frame that called it,
6884 and so on upward. These numbers do not really exist in your program;
6885 they are assigned by @value{GDBN} to give you a way of designating stack
6886 frames in @value{GDBN} commands.
6888 @c The -fomit-frame-pointer below perennially causes hbox overflow
6889 @c underflow problems.
6890 @cindex frameless execution
6891 Some compilers provide a way to compile functions so that they operate
6892 without stack frames. (For example, the @value{NGCC} option
6894 @samp{-fomit-frame-pointer}
6896 generates functions without a frame.)
6897 This is occasionally done with heavily used library functions to save
6898 the frame setup time. @value{GDBN} has limited facilities for dealing
6899 with these function invocations. If the innermost function invocation
6900 has no stack frame, @value{GDBN} nevertheless regards it as though
6901 it had a separate frame, which is numbered zero as usual, allowing
6902 correct tracing of the function call chain. However, @value{GDBN} has
6903 no provision for frameless functions elsewhere in the stack.
6906 @kindex frame@r{, command}
6907 @cindex current stack frame
6908 @item frame @r{[}@var{framespec}@r{]}
6909 The @code{frame} command allows you to move from one stack frame to another,
6910 and to print the stack frame you select. The @var{framespec} may be either the
6911 address of the frame or the stack frame number. Without an argument,
6912 @code{frame} prints the current stack frame.
6914 @kindex select-frame
6915 @cindex selecting frame silently
6917 The @code{select-frame} command allows you to move from one stack frame
6918 to another without printing the frame. This is the silent version of
6926 @cindex call stack traces
6927 A backtrace is a summary of how your program got where it is. It shows one
6928 line per frame, for many frames, starting with the currently executing
6929 frame (frame zero), followed by its caller (frame one), and on up the
6932 @anchor{backtrace-command}
6935 @kindex bt @r{(@code{backtrace})}
6938 Print a backtrace of the entire stack: one line per frame for all
6939 frames in the stack.
6941 You can stop the backtrace at any time by typing the system interrupt
6942 character, normally @kbd{Ctrl-c}.
6944 @item backtrace @var{n}
6946 Similar, but print only the innermost @var{n} frames.
6948 @item backtrace -@var{n}
6950 Similar, but print only the outermost @var{n} frames.
6952 @item backtrace full
6954 @itemx bt full @var{n}
6955 @itemx bt full -@var{n}
6956 Print the values of the local variables also. As described above,
6957 @var{n} specifies the number of frames to print.
6959 @item backtrace no-filters
6960 @itemx bt no-filters
6961 @itemx bt no-filters @var{n}
6962 @itemx bt no-filters -@var{n}
6963 @itemx bt no-filters full
6964 @itemx bt no-filters full @var{n}
6965 @itemx bt no-filters full -@var{n}
6966 Do not run Python frame filters on this backtrace. @xref{Frame
6967 Filter API}, for more information. Additionally use @ref{disable
6968 frame-filter all} to turn off all frame filters. This is only
6969 relevant when @value{GDBN} has been configured with @code{Python}
6975 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6976 are additional aliases for @code{backtrace}.
6978 @cindex multiple threads, backtrace
6979 In a multi-threaded program, @value{GDBN} by default shows the
6980 backtrace only for the current thread. To display the backtrace for
6981 several or all of the threads, use the command @code{thread apply}
6982 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6983 apply all backtrace}, @value{GDBN} will display the backtrace for all
6984 the threads; this is handy when you debug a core dump of a
6985 multi-threaded program.
6987 Each line in the backtrace shows the frame number and the function name.
6988 The program counter value is also shown---unless you use @code{set
6989 print address off}. The backtrace also shows the source file name and
6990 line number, as well as the arguments to the function. The program
6991 counter value is omitted if it is at the beginning of the code for that
6994 Here is an example of a backtrace. It was made with the command
6995 @samp{bt 3}, so it shows the innermost three frames.
6999 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7001 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
7002 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
7004 (More stack frames follow...)
7009 The display for frame zero does not begin with a program counter
7010 value, indicating that your program has stopped at the beginning of the
7011 code for line @code{993} of @code{builtin.c}.
7014 The value of parameter @code{data} in frame 1 has been replaced by
7015 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
7016 only if it is a scalar (integer, pointer, enumeration, etc). See command
7017 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
7018 on how to configure the way function parameter values are printed.
7020 @cindex optimized out, in backtrace
7021 @cindex function call arguments, optimized out
7022 If your program was compiled with optimizations, some compilers will
7023 optimize away arguments passed to functions if those arguments are
7024 never used after the call. Such optimizations generate code that
7025 passes arguments through registers, but doesn't store those arguments
7026 in the stack frame. @value{GDBN} has no way of displaying such
7027 arguments in stack frames other than the innermost one. Here's what
7028 such a backtrace might look like:
7032 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7034 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
7035 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
7037 (More stack frames follow...)
7042 The values of arguments that were not saved in their stack frames are
7043 shown as @samp{<optimized out>}.
7045 If you need to display the values of such optimized-out arguments,
7046 either deduce that from other variables whose values depend on the one
7047 you are interested in, or recompile without optimizations.
7049 @cindex backtrace beyond @code{main} function
7050 @cindex program entry point
7051 @cindex startup code, and backtrace
7052 Most programs have a standard user entry point---a place where system
7053 libraries and startup code transition into user code. For C this is
7054 @code{main}@footnote{
7055 Note that embedded programs (the so-called ``free-standing''
7056 environment) are not required to have a @code{main} function as the
7057 entry point. They could even have multiple entry points.}.
7058 When @value{GDBN} finds the entry function in a backtrace
7059 it will terminate the backtrace, to avoid tracing into highly
7060 system-specific (and generally uninteresting) code.
7062 If you need to examine the startup code, or limit the number of levels
7063 in a backtrace, you can change this behavior:
7066 @item set backtrace past-main
7067 @itemx set backtrace past-main on
7068 @kindex set backtrace
7069 Backtraces will continue past the user entry point.
7071 @item set backtrace past-main off
7072 Backtraces will stop when they encounter the user entry point. This is the
7075 @item show backtrace past-main
7076 @kindex show backtrace
7077 Display the current user entry point backtrace policy.
7079 @item set backtrace past-entry
7080 @itemx set backtrace past-entry on
7081 Backtraces will continue past the internal entry point of an application.
7082 This entry point is encoded by the linker when the application is built,
7083 and is likely before the user entry point @code{main} (or equivalent) is called.
7085 @item set backtrace past-entry off
7086 Backtraces will stop when they encounter the internal entry point of an
7087 application. This is the default.
7089 @item show backtrace past-entry
7090 Display the current internal entry point backtrace policy.
7092 @item set backtrace limit @var{n}
7093 @itemx set backtrace limit 0
7094 @itemx set backtrace limit unlimited
7095 @cindex backtrace limit
7096 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
7097 or zero means unlimited levels.
7099 @item show backtrace limit
7100 Display the current limit on backtrace levels.
7103 You can control how file names are displayed.
7106 @item set filename-display
7107 @itemx set filename-display relative
7108 @cindex filename-display
7109 Display file names relative to the compilation directory. This is the default.
7111 @item set filename-display basename
7112 Display only basename of a filename.
7114 @item set filename-display absolute
7115 Display an absolute filename.
7117 @item show filename-display
7118 Show the current way to display filenames.
7121 @node Frame Filter Management
7122 @section Management of Frame Filters.
7123 @cindex managing frame filters
7125 Frame filters are Python based utilities to manage and decorate the
7126 output of frames. @xref{Frame Filter API}, for further information.
7128 Managing frame filters is performed by several commands available
7129 within @value{GDBN}, detailed here.
7132 @kindex info frame-filter
7133 @item info frame-filter
7134 Print a list of installed frame filters from all dictionaries, showing
7135 their name, priority and enabled status.
7137 @kindex disable frame-filter
7138 @anchor{disable frame-filter all}
7139 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
7140 Disable a frame filter in the dictionary matching
7141 @var{filter-dictionary} and @var{filter-name}. The
7142 @var{filter-dictionary} may be @code{all}, @code{global},
7143 @code{progspace}, or the name of the object file where the frame filter
7144 dictionary resides. When @code{all} is specified, all frame filters
7145 across all dictionaries are disabled. The @var{filter-name} is the name
7146 of the frame filter and is used when @code{all} is not the option for
7147 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
7148 may be enabled again later.
7150 @kindex enable frame-filter
7151 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
7152 Enable a frame filter in the dictionary matching
7153 @var{filter-dictionary} and @var{filter-name}. The
7154 @var{filter-dictionary} may be @code{all}, @code{global},
7155 @code{progspace} or the name of the object file where the frame filter
7156 dictionary resides. When @code{all} is specified, all frame filters across
7157 all dictionaries are enabled. The @var{filter-name} is the name of the frame
7158 filter and is used when @code{all} is not the option for
7159 @var{filter-dictionary}.
7164 (gdb) info frame-filter
7166 global frame-filters:
7167 Priority Enabled Name
7168 1000 No PrimaryFunctionFilter
7171 progspace /build/test frame-filters:
7172 Priority Enabled Name
7173 100 Yes ProgspaceFilter
7175 objfile /build/test frame-filters:
7176 Priority Enabled Name
7177 999 Yes BuildProgra Filter
7179 (gdb) disable frame-filter /build/test BuildProgramFilter
7180 (gdb) info frame-filter
7182 global frame-filters:
7183 Priority Enabled Name
7184 1000 No PrimaryFunctionFilter
7187 progspace /build/test frame-filters:
7188 Priority Enabled Name
7189 100 Yes ProgspaceFilter
7191 objfile /build/test frame-filters:
7192 Priority Enabled Name
7193 999 No BuildProgramFilter
7195 (gdb) enable frame-filter global PrimaryFunctionFilter
7196 (gdb) info frame-filter
7198 global frame-filters:
7199 Priority Enabled Name
7200 1000 Yes PrimaryFunctionFilter
7203 progspace /build/test frame-filters:
7204 Priority Enabled Name
7205 100 Yes ProgspaceFilter
7207 objfile /build/test frame-filters:
7208 Priority Enabled Name
7209 999 No BuildProgramFilter
7212 @kindex set frame-filter priority
7213 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
7214 Set the @var{priority} of a frame filter in the dictionary matching
7215 @var{filter-dictionary}, and the frame filter name matching
7216 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7217 @code{progspace} or the name of the object file where the frame filter
7218 dictionary resides. The @var{priority} is an integer.
7220 @kindex show frame-filter priority
7221 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
7222 Show the @var{priority} of a frame filter in the dictionary matching
7223 @var{filter-dictionary}, and the frame filter name matching
7224 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7225 @code{progspace} or the name of the object file where the frame filter
7231 (gdb) info frame-filter
7233 global frame-filters:
7234 Priority Enabled Name
7235 1000 Yes PrimaryFunctionFilter
7238 progspace /build/test frame-filters:
7239 Priority Enabled Name
7240 100 Yes ProgspaceFilter
7242 objfile /build/test frame-filters:
7243 Priority Enabled Name
7244 999 No BuildProgramFilter
7246 (gdb) set frame-filter priority global Reverse 50
7247 (gdb) info frame-filter
7249 global frame-filters:
7250 Priority Enabled Name
7251 1000 Yes PrimaryFunctionFilter
7254 progspace /build/test frame-filters:
7255 Priority Enabled Name
7256 100 Yes ProgspaceFilter
7258 objfile /build/test frame-filters:
7259 Priority Enabled Name
7260 999 No BuildProgramFilter
7265 @section Selecting a Frame
7267 Most commands for examining the stack and other data in your program work on
7268 whichever stack frame is selected at the moment. Here are the commands for
7269 selecting a stack frame; all of them finish by printing a brief description
7270 of the stack frame just selected.
7273 @kindex frame@r{, selecting}
7274 @kindex f @r{(@code{frame})}
7277 Select frame number @var{n}. Recall that frame zero is the innermost
7278 (currently executing) frame, frame one is the frame that called the
7279 innermost one, and so on. The highest-numbered frame is the one for
7282 @item frame @var{addr}
7284 Select the frame at address @var{addr}. This is useful mainly if the
7285 chaining of stack frames has been damaged by a bug, making it
7286 impossible for @value{GDBN} to assign numbers properly to all frames. In
7287 addition, this can be useful when your program has multiple stacks and
7288 switches between them.
7290 On the SPARC architecture, @code{frame} needs two addresses to
7291 select an arbitrary frame: a frame pointer and a stack pointer.
7293 On the @acronym{MIPS} and Alpha architecture, it needs two addresses: a stack
7294 pointer and a program counter.
7296 On the 29k architecture, it needs three addresses: a register stack
7297 pointer, a program counter, and a memory stack pointer.
7301 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
7302 numbers @var{n}, this advances toward the outermost frame, to higher
7303 frame numbers, to frames that have existed longer.
7306 @kindex do @r{(@code{down})}
7308 Move @var{n} frames down the stack; @var{n} defaults to 1. For
7309 positive numbers @var{n}, this advances toward the innermost frame, to
7310 lower frame numbers, to frames that were created more recently.
7311 You may abbreviate @code{down} as @code{do}.
7314 All of these commands end by printing two lines of output describing the
7315 frame. The first line shows the frame number, the function name, the
7316 arguments, and the source file and line number of execution in that
7317 frame. The second line shows the text of that source line.
7325 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7327 10 read_input_file (argv[i]);
7331 After such a printout, the @code{list} command with no arguments
7332 prints ten lines centered on the point of execution in the frame.
7333 You can also edit the program at the point of execution with your favorite
7334 editing program by typing @code{edit}.
7335 @xref{List, ,Printing Source Lines},
7339 @kindex down-silently
7341 @item up-silently @var{n}
7342 @itemx down-silently @var{n}
7343 These two commands are variants of @code{up} and @code{down},
7344 respectively; they differ in that they do their work silently, without
7345 causing display of the new frame. They are intended primarily for use
7346 in @value{GDBN} command scripts, where the output might be unnecessary and
7351 @section Information About a Frame
7353 There are several other commands to print information about the selected
7359 When used without any argument, this command does not change which
7360 frame is selected, but prints a brief description of the currently
7361 selected stack frame. It can be abbreviated @code{f}. With an
7362 argument, this command is used to select a stack frame.
7363 @xref{Selection, ,Selecting a Frame}.
7366 @kindex info f @r{(@code{info frame})}
7369 This command prints a verbose description of the selected stack frame,
7374 the address of the frame
7376 the address of the next frame down (called by this frame)
7378 the address of the next frame up (caller of this frame)
7380 the language in which the source code corresponding to this frame is written
7382 the address of the frame's arguments
7384 the address of the frame's local variables
7386 the program counter saved in it (the address of execution in the caller frame)
7388 which registers were saved in the frame
7391 @noindent The verbose description is useful when
7392 something has gone wrong that has made the stack format fail to fit
7393 the usual conventions.
7395 @item info frame @var{addr}
7396 @itemx info f @var{addr}
7397 Print a verbose description of the frame at address @var{addr}, without
7398 selecting that frame. The selected frame remains unchanged by this
7399 command. This requires the same kind of address (more than one for some
7400 architectures) that you specify in the @code{frame} command.
7401 @xref{Selection, ,Selecting a Frame}.
7405 Print the arguments of the selected frame, each on a separate line.
7409 Print the local variables of the selected frame, each on a separate
7410 line. These are all variables (declared either static or automatic)
7411 accessible at the point of execution of the selected frame.
7417 @chapter Examining Source Files
7419 @value{GDBN} can print parts of your program's source, since the debugging
7420 information recorded in the program tells @value{GDBN} what source files were
7421 used to build it. When your program stops, @value{GDBN} spontaneously prints
7422 the line where it stopped. Likewise, when you select a stack frame
7423 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7424 execution in that frame has stopped. You can print other portions of
7425 source files by explicit command.
7427 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7428 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7429 @value{GDBN} under @sc{gnu} Emacs}.
7432 * List:: Printing source lines
7433 * Specify Location:: How to specify code locations
7434 * Edit:: Editing source files
7435 * Search:: Searching source files
7436 * Source Path:: Specifying source directories
7437 * Machine Code:: Source and machine code
7441 @section Printing Source Lines
7444 @kindex l @r{(@code{list})}
7445 To print lines from a source file, use the @code{list} command
7446 (abbreviated @code{l}). By default, ten lines are printed.
7447 There are several ways to specify what part of the file you want to
7448 print; see @ref{Specify Location}, for the full list.
7450 Here are the forms of the @code{list} command most commonly used:
7453 @item list @var{linenum}
7454 Print lines centered around line number @var{linenum} in the
7455 current source file.
7457 @item list @var{function}
7458 Print lines centered around the beginning of function
7462 Print more lines. If the last lines printed were printed with a
7463 @code{list} command, this prints lines following the last lines
7464 printed; however, if the last line printed was a solitary line printed
7465 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7466 Stack}), this prints lines centered around that line.
7469 Print lines just before the lines last printed.
7472 @cindex @code{list}, how many lines to display
7473 By default, @value{GDBN} prints ten source lines with any of these forms of
7474 the @code{list} command. You can change this using @code{set listsize}:
7477 @kindex set listsize
7478 @item set listsize @var{count}
7479 @itemx set listsize unlimited
7480 Make the @code{list} command display @var{count} source lines (unless
7481 the @code{list} argument explicitly specifies some other number).
7482 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7484 @kindex show listsize
7486 Display the number of lines that @code{list} prints.
7489 Repeating a @code{list} command with @key{RET} discards the argument,
7490 so it is equivalent to typing just @code{list}. This is more useful
7491 than listing the same lines again. An exception is made for an
7492 argument of @samp{-}; that argument is preserved in repetition so that
7493 each repetition moves up in the source file.
7495 In general, the @code{list} command expects you to supply zero, one or two
7496 @dfn{linespecs}. Linespecs specify source lines; there are several ways
7497 of writing them (@pxref{Specify Location}), but the effect is always
7498 to specify some source line.
7500 Here is a complete description of the possible arguments for @code{list}:
7503 @item list @var{linespec}
7504 Print lines centered around the line specified by @var{linespec}.
7506 @item list @var{first},@var{last}
7507 Print lines from @var{first} to @var{last}. Both arguments are
7508 linespecs. When a @code{list} command has two linespecs, and the
7509 source file of the second linespec is omitted, this refers to
7510 the same source file as the first linespec.
7512 @item list ,@var{last}
7513 Print lines ending with @var{last}.
7515 @item list @var{first},
7516 Print lines starting with @var{first}.
7519 Print lines just after the lines last printed.
7522 Print lines just before the lines last printed.
7525 As described in the preceding table.
7528 @node Specify Location
7529 @section Specifying a Location
7530 @cindex specifying location
7533 Several @value{GDBN} commands accept arguments that specify a location
7534 of your program's code. Since @value{GDBN} is a source-level
7535 debugger, a location usually specifies some line in the source code;
7536 for that reason, locations are also known as @dfn{linespecs}.
7538 Here are all the different ways of specifying a code location that
7539 @value{GDBN} understands:
7543 Specifies the line number @var{linenum} of the current source file.
7546 @itemx +@var{offset}
7547 Specifies the line @var{offset} lines before or after the @dfn{current
7548 line}. For the @code{list} command, the current line is the last one
7549 printed; for the breakpoint commands, this is the line at which
7550 execution stopped in the currently selected @dfn{stack frame}
7551 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7552 used as the second of the two linespecs in a @code{list} command,
7553 this specifies the line @var{offset} lines up or down from the first
7556 @item @var{filename}:@var{linenum}
7557 Specifies the line @var{linenum} in the source file @var{filename}.
7558 If @var{filename} is a relative file name, then it will match any
7559 source file name with the same trailing components. For example, if
7560 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7561 name of @file{/build/trunk/gcc/expr.c}, but not
7562 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7564 @item @var{function}
7565 Specifies the line that begins the body of the function @var{function}.
7566 For example, in C, this is the line with the open brace.
7568 @item @var{function}:@var{label}
7569 Specifies the line where @var{label} appears in @var{function}.
7571 @item @var{filename}:@var{function}
7572 Specifies the line that begins the body of the function @var{function}
7573 in the file @var{filename}. You only need the file name with a
7574 function name to avoid ambiguity when there are identically named
7575 functions in different source files.
7578 Specifies the line at which the label named @var{label} appears.
7579 @value{GDBN} searches for the label in the function corresponding to
7580 the currently selected stack frame. If there is no current selected
7581 stack frame (for instance, if the inferior is not running), then
7582 @value{GDBN} will not search for a label.
7584 @item *@var{address}
7585 Specifies the program address @var{address}. For line-oriented
7586 commands, such as @code{list} and @code{edit}, this specifies a source
7587 line that contains @var{address}. For @code{break} and other
7588 breakpoint oriented commands, this can be used to set breakpoints in
7589 parts of your program which do not have debugging information or
7592 Here @var{address} may be any expression valid in the current working
7593 language (@pxref{Languages, working language}) that specifies a code
7594 address. In addition, as a convenience, @value{GDBN} extends the
7595 semantics of expressions used in locations to cover the situations
7596 that frequently happen during debugging. Here are the various forms
7600 @item @var{expression}
7601 Any expression valid in the current working language.
7603 @item @var{funcaddr}
7604 An address of a function or procedure derived from its name. In C,
7605 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
7606 simply the function's name @var{function} (and actually a special case
7607 of a valid expression). In Pascal and Modula-2, this is
7608 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
7609 (although the Pascal form also works).
7611 This form specifies the address of the function's first instruction,
7612 before the stack frame and arguments have been set up.
7614 @item '@var{filename}':@var{funcaddr}
7615 Like @var{funcaddr} above, but also specifies the name of the source
7616 file explicitly. This is useful if the name of the function does not
7617 specify the function unambiguously, e.g., if there are several
7618 functions with identical names in different source files.
7621 @cindex breakpoint at static probe point
7622 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7623 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7624 applications to embed static probes. @xref{Static Probe Points}, for more
7625 information on finding and using static probes. This form of linespec
7626 specifies the location of such a static probe.
7628 If @var{objfile} is given, only probes coming from that shared library
7629 or executable matching @var{objfile} as a regular expression are considered.
7630 If @var{provider} is given, then only probes from that provider are considered.
7631 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7632 each one of those probes.
7638 @section Editing Source Files
7639 @cindex editing source files
7642 @kindex e @r{(@code{edit})}
7643 To edit the lines in a source file, use the @code{edit} command.
7644 The editing program of your choice
7645 is invoked with the current line set to
7646 the active line in the program.
7647 Alternatively, there are several ways to specify what part of the file you
7648 want to print if you want to see other parts of the program:
7651 @item edit @var{location}
7652 Edit the source file specified by @code{location}. Editing starts at
7653 that @var{location}, e.g., at the specified source line of the
7654 specified file. @xref{Specify Location}, for all the possible forms
7655 of the @var{location} argument; here are the forms of the @code{edit}
7656 command most commonly used:
7659 @item edit @var{number}
7660 Edit the current source file with @var{number} as the active line number.
7662 @item edit @var{function}
7663 Edit the file containing @var{function} at the beginning of its definition.
7668 @subsection Choosing your Editor
7669 You can customize @value{GDBN} to use any editor you want
7671 The only restriction is that your editor (say @code{ex}), recognizes the
7672 following command-line syntax:
7674 ex +@var{number} file
7676 The optional numeric value +@var{number} specifies the number of the line in
7677 the file where to start editing.}.
7678 By default, it is @file{@value{EDITOR}}, but you can change this
7679 by setting the environment variable @code{EDITOR} before using
7680 @value{GDBN}. For example, to configure @value{GDBN} to use the
7681 @code{vi} editor, you could use these commands with the @code{sh} shell:
7687 or in the @code{csh} shell,
7689 setenv EDITOR /usr/bin/vi
7694 @section Searching Source Files
7695 @cindex searching source files
7697 There are two commands for searching through the current source file for a
7702 @kindex forward-search
7703 @kindex fo @r{(@code{forward-search})}
7704 @item forward-search @var{regexp}
7705 @itemx search @var{regexp}
7706 The command @samp{forward-search @var{regexp}} checks each line,
7707 starting with the one following the last line listed, for a match for
7708 @var{regexp}. It lists the line that is found. You can use the
7709 synonym @samp{search @var{regexp}} or abbreviate the command name as
7712 @kindex reverse-search
7713 @item reverse-search @var{regexp}
7714 The command @samp{reverse-search @var{regexp}} checks each line, starting
7715 with the one before the last line listed and going backward, for a match
7716 for @var{regexp}. It lists the line that is found. You can abbreviate
7717 this command as @code{rev}.
7721 @section Specifying Source Directories
7724 @cindex directories for source files
7725 Executable programs sometimes do not record the directories of the source
7726 files from which they were compiled, just the names. Even when they do,
7727 the directories could be moved between the compilation and your debugging
7728 session. @value{GDBN} has a list of directories to search for source files;
7729 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
7730 it tries all the directories in the list, in the order they are present
7731 in the list, until it finds a file with the desired name.
7733 For example, suppose an executable references the file
7734 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
7735 @file{/mnt/cross}. The file is first looked up literally; if this
7736 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
7737 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
7738 message is printed. @value{GDBN} does not look up the parts of the
7739 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
7740 Likewise, the subdirectories of the source path are not searched: if
7741 the source path is @file{/mnt/cross}, and the binary refers to
7742 @file{foo.c}, @value{GDBN} would not find it under
7743 @file{/mnt/cross/usr/src/foo-1.0/lib}.
7745 Plain file names, relative file names with leading directories, file
7746 names containing dots, etc.@: are all treated as described above; for
7747 instance, if the source path is @file{/mnt/cross}, and the source file
7748 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
7749 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
7750 that---@file{/mnt/cross/foo.c}.
7752 Note that the executable search path is @emph{not} used to locate the
7755 Whenever you reset or rearrange the source path, @value{GDBN} clears out
7756 any information it has cached about where source files are found and where
7757 each line is in the file.
7761 When you start @value{GDBN}, its source path includes only @samp{cdir}
7762 and @samp{cwd}, in that order.
7763 To add other directories, use the @code{directory} command.
7765 The search path is used to find both program source files and @value{GDBN}
7766 script files (read using the @samp{-command} option and @samp{source} command).
7768 In addition to the source path, @value{GDBN} provides a set of commands
7769 that manage a list of source path substitution rules. A @dfn{substitution
7770 rule} specifies how to rewrite source directories stored in the program's
7771 debug information in case the sources were moved to a different
7772 directory between compilation and debugging. A rule is made of
7773 two strings, the first specifying what needs to be rewritten in
7774 the path, and the second specifying how it should be rewritten.
7775 In @ref{set substitute-path}, we name these two parts @var{from} and
7776 @var{to} respectively. @value{GDBN} does a simple string replacement
7777 of @var{from} with @var{to} at the start of the directory part of the
7778 source file name, and uses that result instead of the original file
7779 name to look up the sources.
7781 Using the previous example, suppose the @file{foo-1.0} tree has been
7782 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
7783 @value{GDBN} to replace @file{/usr/src} in all source path names with
7784 @file{/mnt/cross}. The first lookup will then be
7785 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
7786 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
7787 substitution rule, use the @code{set substitute-path} command
7788 (@pxref{set substitute-path}).
7790 To avoid unexpected substitution results, a rule is applied only if the
7791 @var{from} part of the directory name ends at a directory separator.
7792 For instance, a rule substituting @file{/usr/source} into
7793 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
7794 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
7795 is applied only at the beginning of the directory name, this rule will
7796 not be applied to @file{/root/usr/source/baz.c} either.
7798 In many cases, you can achieve the same result using the @code{directory}
7799 command. However, @code{set substitute-path} can be more efficient in
7800 the case where the sources are organized in a complex tree with multiple
7801 subdirectories. With the @code{directory} command, you need to add each
7802 subdirectory of your project. If you moved the entire tree while
7803 preserving its internal organization, then @code{set substitute-path}
7804 allows you to direct the debugger to all the sources with one single
7807 @code{set substitute-path} is also more than just a shortcut command.
7808 The source path is only used if the file at the original location no
7809 longer exists. On the other hand, @code{set substitute-path} modifies
7810 the debugger behavior to look at the rewritten location instead. So, if
7811 for any reason a source file that is not relevant to your executable is
7812 located at the original location, a substitution rule is the only
7813 method available to point @value{GDBN} at the new location.
7815 @cindex @samp{--with-relocated-sources}
7816 @cindex default source path substitution
7817 You can configure a default source path substitution rule by
7818 configuring @value{GDBN} with the
7819 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
7820 should be the name of a directory under @value{GDBN}'s configured
7821 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
7822 directory names in debug information under @var{dir} will be adjusted
7823 automatically if the installed @value{GDBN} is moved to a new
7824 location. This is useful if @value{GDBN}, libraries or executables
7825 with debug information and corresponding source code are being moved
7829 @item directory @var{dirname} @dots{}
7830 @item dir @var{dirname} @dots{}
7831 Add directory @var{dirname} to the front of the source path. Several
7832 directory names may be given to this command, separated by @samp{:}
7833 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
7834 part of absolute file names) or
7835 whitespace. You may specify a directory that is already in the source
7836 path; this moves it forward, so @value{GDBN} searches it sooner.
7840 @vindex $cdir@r{, convenience variable}
7841 @vindex $cwd@r{, convenience variable}
7842 @cindex compilation directory
7843 @cindex current directory
7844 @cindex working directory
7845 @cindex directory, current
7846 @cindex directory, compilation
7847 You can use the string @samp{$cdir} to refer to the compilation
7848 directory (if one is recorded), and @samp{$cwd} to refer to the current
7849 working directory. @samp{$cwd} is not the same as @samp{.}---the former
7850 tracks the current working directory as it changes during your @value{GDBN}
7851 session, while the latter is immediately expanded to the current
7852 directory at the time you add an entry to the source path.
7855 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
7857 @c RET-repeat for @code{directory} is explicitly disabled, but since
7858 @c repeating it would be a no-op we do not say that. (thanks to RMS)
7860 @item set directories @var{path-list}
7861 @kindex set directories
7862 Set the source path to @var{path-list}.
7863 @samp{$cdir:$cwd} are added if missing.
7865 @item show directories
7866 @kindex show directories
7867 Print the source path: show which directories it contains.
7869 @anchor{set substitute-path}
7870 @item set substitute-path @var{from} @var{to}
7871 @kindex set substitute-path
7872 Define a source path substitution rule, and add it at the end of the
7873 current list of existing substitution rules. If a rule with the same
7874 @var{from} was already defined, then the old rule is also deleted.
7876 For example, if the file @file{/foo/bar/baz.c} was moved to
7877 @file{/mnt/cross/baz.c}, then the command
7880 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
7884 will tell @value{GDBN} to replace @samp{/usr/src} with
7885 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
7886 @file{baz.c} even though it was moved.
7888 In the case when more than one substitution rule have been defined,
7889 the rules are evaluated one by one in the order where they have been
7890 defined. The first one matching, if any, is selected to perform
7893 For instance, if we had entered the following commands:
7896 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
7897 (@value{GDBP}) set substitute-path /usr/src /mnt/src
7901 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
7902 @file{/mnt/include/defs.h} by using the first rule. However, it would
7903 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
7904 @file{/mnt/src/lib/foo.c}.
7907 @item unset substitute-path [path]
7908 @kindex unset substitute-path
7909 If a path is specified, search the current list of substitution rules
7910 for a rule that would rewrite that path. Delete that rule if found.
7911 A warning is emitted by the debugger if no rule could be found.
7913 If no path is specified, then all substitution rules are deleted.
7915 @item show substitute-path [path]
7916 @kindex show substitute-path
7917 If a path is specified, then print the source path substitution rule
7918 which would rewrite that path, if any.
7920 If no path is specified, then print all existing source path substitution
7925 If your source path is cluttered with directories that are no longer of
7926 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
7927 versions of source. You can correct the situation as follows:
7931 Use @code{directory} with no argument to reset the source path to its default value.
7934 Use @code{directory} with suitable arguments to reinstall the
7935 directories you want in the source path. You can add all the
7936 directories in one command.
7940 @section Source and Machine Code
7941 @cindex source line and its code address
7943 You can use the command @code{info line} to map source lines to program
7944 addresses (and vice versa), and the command @code{disassemble} to display
7945 a range of addresses as machine instructions. You can use the command
7946 @code{set disassemble-next-line} to set whether to disassemble next
7947 source line when execution stops. When run under @sc{gnu} Emacs
7948 mode, the @code{info line} command causes the arrow to point to the
7949 line specified. Also, @code{info line} prints addresses in symbolic form as
7954 @item info line @var{linespec}
7955 Print the starting and ending addresses of the compiled code for
7956 source line @var{linespec}. You can specify source lines in any of
7957 the ways documented in @ref{Specify Location}.
7960 For example, we can use @code{info line} to discover the location of
7961 the object code for the first line of function
7962 @code{m4_changequote}:
7964 @c FIXME: I think this example should also show the addresses in
7965 @c symbolic form, as they usually would be displayed.
7967 (@value{GDBP}) info line m4_changequote
7968 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
7972 @cindex code address and its source line
7973 We can also inquire (using @code{*@var{addr}} as the form for
7974 @var{linespec}) what source line covers a particular address:
7976 (@value{GDBP}) info line *0x63ff
7977 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
7980 @cindex @code{$_} and @code{info line}
7981 @cindex @code{x} command, default address
7982 @kindex x@r{(examine), and} info line
7983 After @code{info line}, the default address for the @code{x} command
7984 is changed to the starting address of the line, so that @samp{x/i} is
7985 sufficient to begin examining the machine code (@pxref{Memory,
7986 ,Examining Memory}). Also, this address is saved as the value of the
7987 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
7992 @cindex assembly instructions
7993 @cindex instructions, assembly
7994 @cindex machine instructions
7995 @cindex listing machine instructions
7997 @itemx disassemble /m
7998 @itemx disassemble /r
7999 This specialized command dumps a range of memory as machine
8000 instructions. It can also print mixed source+disassembly by specifying
8001 the @code{/m} modifier and print the raw instructions in hex as well as
8002 in symbolic form by specifying the @code{/r}.
8003 The default memory range is the function surrounding the
8004 program counter of the selected frame. A single argument to this
8005 command is a program counter value; @value{GDBN} dumps the function
8006 surrounding this value. When two arguments are given, they should
8007 be separated by a comma, possibly surrounded by whitespace. The
8008 arguments specify a range of addresses to dump, in one of two forms:
8011 @item @var{start},@var{end}
8012 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
8013 @item @var{start},+@var{length}
8014 the addresses from @var{start} (inclusive) to
8015 @code{@var{start}+@var{length}} (exclusive).
8019 When 2 arguments are specified, the name of the function is also
8020 printed (since there could be several functions in the given range).
8022 The argument(s) can be any expression yielding a numeric value, such as
8023 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
8025 If the range of memory being disassembled contains current program counter,
8026 the instruction at that location is shown with a @code{=>} marker.
8029 The following example shows the disassembly of a range of addresses of
8030 HP PA-RISC 2.0 code:
8033 (@value{GDBP}) disas 0x32c4, 0x32e4
8034 Dump of assembler code from 0x32c4 to 0x32e4:
8035 0x32c4 <main+204>: addil 0,dp
8036 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
8037 0x32cc <main+212>: ldil 0x3000,r31
8038 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
8039 0x32d4 <main+220>: ldo 0(r31),rp
8040 0x32d8 <main+224>: addil -0x800,dp
8041 0x32dc <main+228>: ldo 0x588(r1),r26
8042 0x32e0 <main+232>: ldil 0x3000,r31
8043 End of assembler dump.
8046 Here is an example showing mixed source+assembly for Intel x86, when the
8047 program is stopped just after function prologue:
8050 (@value{GDBP}) disas /m main
8051 Dump of assembler code for function main:
8053 0x08048330 <+0>: push %ebp
8054 0x08048331 <+1>: mov %esp,%ebp
8055 0x08048333 <+3>: sub $0x8,%esp
8056 0x08048336 <+6>: and $0xfffffff0,%esp
8057 0x08048339 <+9>: sub $0x10,%esp
8059 6 printf ("Hello.\n");
8060 => 0x0804833c <+12>: movl $0x8048440,(%esp)
8061 0x08048343 <+19>: call 0x8048284 <puts@@plt>
8065 0x08048348 <+24>: mov $0x0,%eax
8066 0x0804834d <+29>: leave
8067 0x0804834e <+30>: ret
8069 End of assembler dump.
8072 Here is another example showing raw instructions in hex for AMD x86-64,
8075 (gdb) disas /r 0x400281,+10
8076 Dump of assembler code from 0x400281 to 0x40028b:
8077 0x0000000000400281: 38 36 cmp %dh,(%rsi)
8078 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
8079 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
8080 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
8081 End of assembler dump.
8084 Addresses cannot be specified as a linespec (@pxref{Specify Location}).
8085 So, for example, if you want to disassemble function @code{bar}
8086 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
8087 and not @samp{disassemble foo.c:bar}.
8089 Some architectures have more than one commonly-used set of instruction
8090 mnemonics or other syntax.
8092 For programs that were dynamically linked and use shared libraries,
8093 instructions that call functions or branch to locations in the shared
8094 libraries might show a seemingly bogus location---it's actually a
8095 location of the relocation table. On some architectures, @value{GDBN}
8096 might be able to resolve these to actual function names.
8099 @kindex set disassembly-flavor
8100 @cindex Intel disassembly flavor
8101 @cindex AT&T disassembly flavor
8102 @item set disassembly-flavor @var{instruction-set}
8103 Select the instruction set to use when disassembling the
8104 program via the @code{disassemble} or @code{x/i} commands.
8106 Currently this command is only defined for the Intel x86 family. You
8107 can set @var{instruction-set} to either @code{intel} or @code{att}.
8108 The default is @code{att}, the AT&T flavor used by default by Unix
8109 assemblers for x86-based targets.
8111 @kindex show disassembly-flavor
8112 @item show disassembly-flavor
8113 Show the current setting of the disassembly flavor.
8117 @kindex set disassemble-next-line
8118 @kindex show disassemble-next-line
8119 @item set disassemble-next-line
8120 @itemx show disassemble-next-line
8121 Control whether or not @value{GDBN} will disassemble the next source
8122 line or instruction when execution stops. If ON, @value{GDBN} will
8123 display disassembly of the next source line when execution of the
8124 program being debugged stops. This is @emph{in addition} to
8125 displaying the source line itself, which @value{GDBN} always does if
8126 possible. If the next source line cannot be displayed for some reason
8127 (e.g., if @value{GDBN} cannot find the source file, or there's no line
8128 info in the debug info), @value{GDBN} will display disassembly of the
8129 next @emph{instruction} instead of showing the next source line. If
8130 AUTO, @value{GDBN} will display disassembly of next instruction only
8131 if the source line cannot be displayed. This setting causes
8132 @value{GDBN} to display some feedback when you step through a function
8133 with no line info or whose source file is unavailable. The default is
8134 OFF, which means never display the disassembly of the next line or
8140 @chapter Examining Data
8142 @cindex printing data
8143 @cindex examining data
8146 The usual way to examine data in your program is with the @code{print}
8147 command (abbreviated @code{p}), or its synonym @code{inspect}. It
8148 evaluates and prints the value of an expression of the language your
8149 program is written in (@pxref{Languages, ,Using @value{GDBN} with
8150 Different Languages}). It may also print the expression using a
8151 Python-based pretty-printer (@pxref{Pretty Printing}).
8154 @item print @var{expr}
8155 @itemx print /@var{f} @var{expr}
8156 @var{expr} is an expression (in the source language). By default the
8157 value of @var{expr} is printed in a format appropriate to its data type;
8158 you can choose a different format by specifying @samp{/@var{f}}, where
8159 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
8163 @itemx print /@var{f}
8164 @cindex reprint the last value
8165 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
8166 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
8167 conveniently inspect the same value in an alternative format.
8170 A more low-level way of examining data is with the @code{x} command.
8171 It examines data in memory at a specified address and prints it in a
8172 specified format. @xref{Memory, ,Examining Memory}.
8174 If you are interested in information about types, or about how the
8175 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
8176 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
8179 @cindex exploring hierarchical data structures
8181 Another way of examining values of expressions and type information is
8182 through the Python extension command @code{explore} (available only if
8183 the @value{GDBN} build is configured with @code{--with-python}). It
8184 offers an interactive way to start at the highest level (or, the most
8185 abstract level) of the data type of an expression (or, the data type
8186 itself) and explore all the way down to leaf scalar values/fields
8187 embedded in the higher level data types.
8190 @item explore @var{arg}
8191 @var{arg} is either an expression (in the source language), or a type
8192 visible in the current context of the program being debugged.
8195 The working of the @code{explore} command can be illustrated with an
8196 example. If a data type @code{struct ComplexStruct} is defined in your
8206 struct ComplexStruct
8208 struct SimpleStruct *ss_p;
8214 followed by variable declarations as
8217 struct SimpleStruct ss = @{ 10, 1.11 @};
8218 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
8222 then, the value of the variable @code{cs} can be explored using the
8223 @code{explore} command as follows.
8227 The value of `cs' is a struct/class of type `struct ComplexStruct' with
8228 the following fields:
8230 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
8231 arr = <Enter 1 to explore this field of type `int [10]'>
8233 Enter the field number of choice:
8237 Since the fields of @code{cs} are not scalar values, you are being
8238 prompted to chose the field you want to explore. Let's say you choose
8239 the field @code{ss_p} by entering @code{0}. Then, since this field is a
8240 pointer, you will be asked if it is pointing to a single value. From
8241 the declaration of @code{cs} above, it is indeed pointing to a single
8242 value, hence you enter @code{y}. If you enter @code{n}, then you will
8243 be asked if it were pointing to an array of values, in which case this
8244 field will be explored as if it were an array.
8247 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
8248 Continue exploring it as a pointer to a single value [y/n]: y
8249 The value of `*(cs.ss_p)' is a struct/class of type `struct
8250 SimpleStruct' with the following fields:
8252 i = 10 .. (Value of type `int')
8253 d = 1.1100000000000001 .. (Value of type `double')
8255 Press enter to return to parent value:
8259 If the field @code{arr} of @code{cs} was chosen for exploration by
8260 entering @code{1} earlier, then since it is as array, you will be
8261 prompted to enter the index of the element in the array that you want
8265 `cs.arr' is an array of `int'.
8266 Enter the index of the element you want to explore in `cs.arr': 5
8268 `(cs.arr)[5]' is a scalar value of type `int'.
8272 Press enter to return to parent value:
8275 In general, at any stage of exploration, you can go deeper towards the
8276 leaf values by responding to the prompts appropriately, or hit the
8277 return key to return to the enclosing data structure (the @i{higher}
8278 level data structure).
8280 Similar to exploring values, you can use the @code{explore} command to
8281 explore types. Instead of specifying a value (which is typically a
8282 variable name or an expression valid in the current context of the
8283 program being debugged), you specify a type name. If you consider the
8284 same example as above, your can explore the type
8285 @code{struct ComplexStruct} by passing the argument
8286 @code{struct ComplexStruct} to the @code{explore} command.
8289 (gdb) explore struct ComplexStruct
8293 By responding to the prompts appropriately in the subsequent interactive
8294 session, you can explore the type @code{struct ComplexStruct} in a
8295 manner similar to how the value @code{cs} was explored in the above
8298 The @code{explore} command also has two sub-commands,
8299 @code{explore value} and @code{explore type}. The former sub-command is
8300 a way to explicitly specify that value exploration of the argument is
8301 being invoked, while the latter is a way to explicitly specify that type
8302 exploration of the argument is being invoked.
8305 @item explore value @var{expr}
8306 @cindex explore value
8307 This sub-command of @code{explore} explores the value of the
8308 expression @var{expr} (if @var{expr} is an expression valid in the
8309 current context of the program being debugged). The behavior of this
8310 command is identical to that of the behavior of the @code{explore}
8311 command being passed the argument @var{expr}.
8313 @item explore type @var{arg}
8314 @cindex explore type
8315 This sub-command of @code{explore} explores the type of @var{arg} (if
8316 @var{arg} is a type visible in the current context of program being
8317 debugged), or the type of the value/expression @var{arg} (if @var{arg}
8318 is an expression valid in the current context of the program being
8319 debugged). If @var{arg} is a type, then the behavior of this command is
8320 identical to that of the @code{explore} command being passed the
8321 argument @var{arg}. If @var{arg} is an expression, then the behavior of
8322 this command will be identical to that of the @code{explore} command
8323 being passed the type of @var{arg} as the argument.
8327 * Expressions:: Expressions
8328 * Ambiguous Expressions:: Ambiguous Expressions
8329 * Variables:: Program variables
8330 * Arrays:: Artificial arrays
8331 * Output Formats:: Output formats
8332 * Memory:: Examining memory
8333 * Auto Display:: Automatic display
8334 * Print Settings:: Print settings
8335 * Pretty Printing:: Python pretty printing
8336 * Value History:: Value history
8337 * Convenience Vars:: Convenience variables
8338 * Convenience Funs:: Convenience functions
8339 * Registers:: Registers
8340 * Floating Point Hardware:: Floating point hardware
8341 * Vector Unit:: Vector Unit
8342 * OS Information:: Auxiliary data provided by operating system
8343 * Memory Region Attributes:: Memory region attributes
8344 * Dump/Restore Files:: Copy between memory and a file
8345 * Core File Generation:: Cause a program dump its core
8346 * Character Sets:: Debugging programs that use a different
8347 character set than GDB does
8348 * Caching Target Data:: Data caching for targets
8349 * Searching Memory:: Searching memory for a sequence of bytes
8353 @section Expressions
8356 @code{print} and many other @value{GDBN} commands accept an expression and
8357 compute its value. Any kind of constant, variable or operator defined
8358 by the programming language you are using is valid in an expression in
8359 @value{GDBN}. This includes conditional expressions, function calls,
8360 casts, and string constants. It also includes preprocessor macros, if
8361 you compiled your program to include this information; see
8364 @cindex arrays in expressions
8365 @value{GDBN} supports array constants in expressions input by
8366 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
8367 you can use the command @code{print @{1, 2, 3@}} to create an array
8368 of three integers. If you pass an array to a function or assign it
8369 to a program variable, @value{GDBN} copies the array to memory that
8370 is @code{malloc}ed in the target program.
8372 Because C is so widespread, most of the expressions shown in examples in
8373 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
8374 Languages}, for information on how to use expressions in other
8377 In this section, we discuss operators that you can use in @value{GDBN}
8378 expressions regardless of your programming language.
8380 @cindex casts, in expressions
8381 Casts are supported in all languages, not just in C, because it is so
8382 useful to cast a number into a pointer in order to examine a structure
8383 at that address in memory.
8384 @c FIXME: casts supported---Mod2 true?
8386 @value{GDBN} supports these operators, in addition to those common
8387 to programming languages:
8391 @samp{@@} is a binary operator for treating parts of memory as arrays.
8392 @xref{Arrays, ,Artificial Arrays}, for more information.
8395 @samp{::} allows you to specify a variable in terms of the file or
8396 function where it is defined. @xref{Variables, ,Program Variables}.
8398 @cindex @{@var{type}@}
8399 @cindex type casting memory
8400 @cindex memory, viewing as typed object
8401 @cindex casts, to view memory
8402 @item @{@var{type}@} @var{addr}
8403 Refers to an object of type @var{type} stored at address @var{addr} in
8404 memory. The address @var{addr} may be any expression whose value is
8405 an integer or pointer (but parentheses are required around binary
8406 operators, just as in a cast). This construct is allowed regardless
8407 of what kind of data is normally supposed to reside at @var{addr}.
8410 @node Ambiguous Expressions
8411 @section Ambiguous Expressions
8412 @cindex ambiguous expressions
8414 Expressions can sometimes contain some ambiguous elements. For instance,
8415 some programming languages (notably Ada, C@t{++} and Objective-C) permit
8416 a single function name to be defined several times, for application in
8417 different contexts. This is called @dfn{overloading}. Another example
8418 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
8419 templates and is typically instantiated several times, resulting in
8420 the same function name being defined in different contexts.
8422 In some cases and depending on the language, it is possible to adjust
8423 the expression to remove the ambiguity. For instance in C@t{++}, you
8424 can specify the signature of the function you want to break on, as in
8425 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
8426 qualified name of your function often makes the expression unambiguous
8429 When an ambiguity that needs to be resolved is detected, the debugger
8430 has the capability to display a menu of numbered choices for each
8431 possibility, and then waits for the selection with the prompt @samp{>}.
8432 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
8433 aborts the current command. If the command in which the expression was
8434 used allows more than one choice to be selected, the next option in the
8435 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
8438 For example, the following session excerpt shows an attempt to set a
8439 breakpoint at the overloaded symbol @code{String::after}.
8440 We choose three particular definitions of that function name:
8442 @c FIXME! This is likely to change to show arg type lists, at least
8445 (@value{GDBP}) b String::after
8448 [2] file:String.cc; line number:867
8449 [3] file:String.cc; line number:860
8450 [4] file:String.cc; line number:875
8451 [5] file:String.cc; line number:853
8452 [6] file:String.cc; line number:846
8453 [7] file:String.cc; line number:735
8455 Breakpoint 1 at 0xb26c: file String.cc, line 867.
8456 Breakpoint 2 at 0xb344: file String.cc, line 875.
8457 Breakpoint 3 at 0xafcc: file String.cc, line 846.
8458 Multiple breakpoints were set.
8459 Use the "delete" command to delete unwanted
8466 @kindex set multiple-symbols
8467 @item set multiple-symbols @var{mode}
8468 @cindex multiple-symbols menu
8470 This option allows you to adjust the debugger behavior when an expression
8473 By default, @var{mode} is set to @code{all}. If the command with which
8474 the expression is used allows more than one choice, then @value{GDBN}
8475 automatically selects all possible choices. For instance, inserting
8476 a breakpoint on a function using an ambiguous name results in a breakpoint
8477 inserted on each possible match. However, if a unique choice must be made,
8478 then @value{GDBN} uses the menu to help you disambiguate the expression.
8479 For instance, printing the address of an overloaded function will result
8480 in the use of the menu.
8482 When @var{mode} is set to @code{ask}, the debugger always uses the menu
8483 when an ambiguity is detected.
8485 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
8486 an error due to the ambiguity and the command is aborted.
8488 @kindex show multiple-symbols
8489 @item show multiple-symbols
8490 Show the current value of the @code{multiple-symbols} setting.
8494 @section Program Variables
8496 The most common kind of expression to use is the name of a variable
8499 Variables in expressions are understood in the selected stack frame
8500 (@pxref{Selection, ,Selecting a Frame}); they must be either:
8504 global (or file-static)
8511 visible according to the scope rules of the
8512 programming language from the point of execution in that frame
8515 @noindent This means that in the function
8530 you can examine and use the variable @code{a} whenever your program is
8531 executing within the function @code{foo}, but you can only use or
8532 examine the variable @code{b} while your program is executing inside
8533 the block where @code{b} is declared.
8535 @cindex variable name conflict
8536 There is an exception: you can refer to a variable or function whose
8537 scope is a single source file even if the current execution point is not
8538 in this file. But it is possible to have more than one such variable or
8539 function with the same name (in different source files). If that
8540 happens, referring to that name has unpredictable effects. If you wish,
8541 you can specify a static variable in a particular function or file by
8542 using the colon-colon (@code{::}) notation:
8544 @cindex colon-colon, context for variables/functions
8546 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
8547 @cindex @code{::}, context for variables/functions
8550 @var{file}::@var{variable}
8551 @var{function}::@var{variable}
8555 Here @var{file} or @var{function} is the name of the context for the
8556 static @var{variable}. In the case of file names, you can use quotes to
8557 make sure @value{GDBN} parses the file name as a single word---for example,
8558 to print a global value of @code{x} defined in @file{f2.c}:
8561 (@value{GDBP}) p 'f2.c'::x
8564 The @code{::} notation is normally used for referring to
8565 static variables, since you typically disambiguate uses of local variables
8566 in functions by selecting the appropriate frame and using the
8567 simple name of the variable. However, you may also use this notation
8568 to refer to local variables in frames enclosing the selected frame:
8577 process (a); /* Stop here */
8588 For example, if there is a breakpoint at the commented line,
8589 here is what you might see
8590 when the program stops after executing the call @code{bar(0)}:
8595 (@value{GDBP}) p bar::a
8598 #2 0x080483d0 in foo (a=5) at foobar.c:12
8601 (@value{GDBP}) p bar::a
8605 @cindex C@t{++} scope resolution
8606 These uses of @samp{::} are very rarely in conflict with the very
8607 similar use of the same notation in C@t{++}. When they are in
8608 conflict, the C@t{++} meaning takes precedence; however, this can be
8609 overridden by quoting the file or function name with single quotes.
8611 For example, suppose the program is stopped in a method of a class
8612 that has a field named @code{includefile}, and there is also an
8613 include file named @file{includefile} that defines a variable,
8617 (@value{GDBP}) p includefile
8619 (@value{GDBP}) p includefile::some_global
8620 A syntax error in expression, near `'.
8621 (@value{GDBP}) p 'includefile'::some_global
8625 @cindex wrong values
8626 @cindex variable values, wrong
8627 @cindex function entry/exit, wrong values of variables
8628 @cindex optimized code, wrong values of variables
8630 @emph{Warning:} Occasionally, a local variable may appear to have the
8631 wrong value at certain points in a function---just after entry to a new
8632 scope, and just before exit.
8634 You may see this problem when you are stepping by machine instructions.
8635 This is because, on most machines, it takes more than one instruction to
8636 set up a stack frame (including local variable definitions); if you are
8637 stepping by machine instructions, variables may appear to have the wrong
8638 values until the stack frame is completely built. On exit, it usually
8639 also takes more than one machine instruction to destroy a stack frame;
8640 after you begin stepping through that group of instructions, local
8641 variable definitions may be gone.
8643 This may also happen when the compiler does significant optimizations.
8644 To be sure of always seeing accurate values, turn off all optimization
8647 @cindex ``No symbol "foo" in current context''
8648 Another possible effect of compiler optimizations is to optimize
8649 unused variables out of existence, or assign variables to registers (as
8650 opposed to memory addresses). Depending on the support for such cases
8651 offered by the debug info format used by the compiler, @value{GDBN}
8652 might not be able to display values for such local variables. If that
8653 happens, @value{GDBN} will print a message like this:
8656 No symbol "foo" in current context.
8659 To solve such problems, either recompile without optimizations, or use a
8660 different debug info format, if the compiler supports several such
8661 formats. @xref{Compilation}, for more information on choosing compiler
8662 options. @xref{C, ,C and C@t{++}}, for more information about debug
8663 info formats that are best suited to C@t{++} programs.
8665 If you ask to print an object whose contents are unknown to
8666 @value{GDBN}, e.g., because its data type is not completely specified
8667 by the debug information, @value{GDBN} will say @samp{<incomplete
8668 type>}. @xref{Symbols, incomplete type}, for more about this.
8670 If you append @kbd{@@entry} string to a function parameter name you get its
8671 value at the time the function got called. If the value is not available an
8672 error message is printed. Entry values are available only with some compilers.
8673 Entry values are normally also printed at the function parameter list according
8674 to @ref{set print entry-values}.
8677 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
8683 (gdb) print i@@entry
8687 Strings are identified as arrays of @code{char} values without specified
8688 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
8689 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
8690 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
8691 defines literal string type @code{"char"} as @code{char} without a sign.
8696 signed char var1[] = "A";
8699 You get during debugging
8704 $2 = @{65 'A', 0 '\0'@}
8708 @section Artificial Arrays
8710 @cindex artificial array
8712 @kindex @@@r{, referencing memory as an array}
8713 It is often useful to print out several successive objects of the
8714 same type in memory; a section of an array, or an array of
8715 dynamically determined size for which only a pointer exists in the
8718 You can do this by referring to a contiguous span of memory as an
8719 @dfn{artificial array}, using the binary operator @samp{@@}. The left
8720 operand of @samp{@@} should be the first element of the desired array
8721 and be an individual object. The right operand should be the desired length
8722 of the array. The result is an array value whose elements are all of
8723 the type of the left argument. The first element is actually the left
8724 argument; the second element comes from bytes of memory immediately
8725 following those that hold the first element, and so on. Here is an
8726 example. If a program says
8729 int *array = (int *) malloc (len * sizeof (int));
8733 you can print the contents of @code{array} with
8739 The left operand of @samp{@@} must reside in memory. Array values made
8740 with @samp{@@} in this way behave just like other arrays in terms of
8741 subscripting, and are coerced to pointers when used in expressions.
8742 Artificial arrays most often appear in expressions via the value history
8743 (@pxref{Value History, ,Value History}), after printing one out.
8745 Another way to create an artificial array is to use a cast.
8746 This re-interprets a value as if it were an array.
8747 The value need not be in memory:
8749 (@value{GDBP}) p/x (short[2])0x12345678
8750 $1 = @{0x1234, 0x5678@}
8753 As a convenience, if you leave the array length out (as in
8754 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
8755 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
8757 (@value{GDBP}) p/x (short[])0x12345678
8758 $2 = @{0x1234, 0x5678@}
8761 Sometimes the artificial array mechanism is not quite enough; in
8762 moderately complex data structures, the elements of interest may not
8763 actually be adjacent---for example, if you are interested in the values
8764 of pointers in an array. One useful work-around in this situation is
8765 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
8766 Variables}) as a counter in an expression that prints the first
8767 interesting value, and then repeat that expression via @key{RET}. For
8768 instance, suppose you have an array @code{dtab} of pointers to
8769 structures, and you are interested in the values of a field @code{fv}
8770 in each structure. Here is an example of what you might type:
8780 @node Output Formats
8781 @section Output Formats
8783 @cindex formatted output
8784 @cindex output formats
8785 By default, @value{GDBN} prints a value according to its data type. Sometimes
8786 this is not what you want. For example, you might want to print a number
8787 in hex, or a pointer in decimal. Or you might want to view data in memory
8788 at a certain address as a character string or as an instruction. To do
8789 these things, specify an @dfn{output format} when you print a value.
8791 The simplest use of output formats is to say how to print a value
8792 already computed. This is done by starting the arguments of the
8793 @code{print} command with a slash and a format letter. The format
8794 letters supported are:
8798 Regard the bits of the value as an integer, and print the integer in
8802 Print as integer in signed decimal.
8805 Print as integer in unsigned decimal.
8808 Print as integer in octal.
8811 Print as integer in binary. The letter @samp{t} stands for ``two''.
8812 @footnote{@samp{b} cannot be used because these format letters are also
8813 used with the @code{x} command, where @samp{b} stands for ``byte'';
8814 see @ref{Memory,,Examining Memory}.}
8817 @cindex unknown address, locating
8818 @cindex locate address
8819 Print as an address, both absolute in hexadecimal and as an offset from
8820 the nearest preceding symbol. You can use this format used to discover
8821 where (in what function) an unknown address is located:
8824 (@value{GDBP}) p/a 0x54320
8825 $3 = 0x54320 <_initialize_vx+396>
8829 The command @code{info symbol 0x54320} yields similar results.
8830 @xref{Symbols, info symbol}.
8833 Regard as an integer and print it as a character constant. This
8834 prints both the numerical value and its character representation. The
8835 character representation is replaced with the octal escape @samp{\nnn}
8836 for characters outside the 7-bit @sc{ascii} range.
8838 Without this format, @value{GDBN} displays @code{char},
8839 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
8840 constants. Single-byte members of vectors are displayed as integer
8844 Regard the bits of the value as a floating point number and print
8845 using typical floating point syntax.
8848 @cindex printing strings
8849 @cindex printing byte arrays
8850 Regard as a string, if possible. With this format, pointers to single-byte
8851 data are displayed as null-terminated strings and arrays of single-byte data
8852 are displayed as fixed-length strings. Other values are displayed in their
8855 Without this format, @value{GDBN} displays pointers to and arrays of
8856 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
8857 strings. Single-byte members of a vector are displayed as an integer
8861 Like @samp{x} formatting, the value is treated as an integer and
8862 printed as hexadecimal, but leading zeros are printed to pad the value
8863 to the size of the integer type.
8866 @cindex raw printing
8867 Print using the @samp{raw} formatting. By default, @value{GDBN} will
8868 use a Python-based pretty-printer, if one is available (@pxref{Pretty
8869 Printing}). This typically results in a higher-level display of the
8870 value's contents. The @samp{r} format bypasses any Python
8871 pretty-printer which might exist.
8874 For example, to print the program counter in hex (@pxref{Registers}), type
8881 Note that no space is required before the slash; this is because command
8882 names in @value{GDBN} cannot contain a slash.
8884 To reprint the last value in the value history with a different format,
8885 you can use the @code{print} command with just a format and no
8886 expression. For example, @samp{p/x} reprints the last value in hex.
8889 @section Examining Memory
8891 You can use the command @code{x} (for ``examine'') to examine memory in
8892 any of several formats, independently of your program's data types.
8894 @cindex examining memory
8896 @kindex x @r{(examine memory)}
8897 @item x/@var{nfu} @var{addr}
8900 Use the @code{x} command to examine memory.
8903 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
8904 much memory to display and how to format it; @var{addr} is an
8905 expression giving the address where you want to start displaying memory.
8906 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
8907 Several commands set convenient defaults for @var{addr}.
8910 @item @var{n}, the repeat count
8911 The repeat count is a decimal integer; the default is 1. It specifies
8912 how much memory (counting by units @var{u}) to display.
8913 @c This really is **decimal**; unaffected by 'set radix' as of GDB
8916 @item @var{f}, the display format
8917 The display format is one of the formats used by @code{print}
8918 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
8919 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
8920 The default is @samp{x} (hexadecimal) initially. The default changes
8921 each time you use either @code{x} or @code{print}.
8923 @item @var{u}, the unit size
8924 The unit size is any of
8930 Halfwords (two bytes).
8932 Words (four bytes). This is the initial default.
8934 Giant words (eight bytes).
8937 Each time you specify a unit size with @code{x}, that size becomes the
8938 default unit the next time you use @code{x}. For the @samp{i} format,
8939 the unit size is ignored and is normally not written. For the @samp{s} format,
8940 the unit size defaults to @samp{b}, unless it is explicitly given.
8941 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
8942 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
8943 Note that the results depend on the programming language of the
8944 current compilation unit. If the language is C, the @samp{s}
8945 modifier will use the UTF-16 encoding while @samp{w} will use
8946 UTF-32. The encoding is set by the programming language and cannot
8949 @item @var{addr}, starting display address
8950 @var{addr} is the address where you want @value{GDBN} to begin displaying
8951 memory. The expression need not have a pointer value (though it may);
8952 it is always interpreted as an integer address of a byte of memory.
8953 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
8954 @var{addr} is usually just after the last address examined---but several
8955 other commands also set the default address: @code{info breakpoints} (to
8956 the address of the last breakpoint listed), @code{info line} (to the
8957 starting address of a line), and @code{print} (if you use it to display
8958 a value from memory).
8961 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
8962 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
8963 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
8964 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
8965 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
8967 Since the letters indicating unit sizes are all distinct from the
8968 letters specifying output formats, you do not have to remember whether
8969 unit size or format comes first; either order works. The output
8970 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
8971 (However, the count @var{n} must come first; @samp{wx4} does not work.)
8973 Even though the unit size @var{u} is ignored for the formats @samp{s}
8974 and @samp{i}, you might still want to use a count @var{n}; for example,
8975 @samp{3i} specifies that you want to see three machine instructions,
8976 including any operands. For convenience, especially when used with
8977 the @code{display} command, the @samp{i} format also prints branch delay
8978 slot instructions, if any, beyond the count specified, which immediately
8979 follow the last instruction that is within the count. The command
8980 @code{disassemble} gives an alternative way of inspecting machine
8981 instructions; see @ref{Machine Code,,Source and Machine Code}.
8983 All the defaults for the arguments to @code{x} are designed to make it
8984 easy to continue scanning memory with minimal specifications each time
8985 you use @code{x}. For example, after you have inspected three machine
8986 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
8987 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
8988 the repeat count @var{n} is used again; the other arguments default as
8989 for successive uses of @code{x}.
8991 When examining machine instructions, the instruction at current program
8992 counter is shown with a @code{=>} marker. For example:
8995 (@value{GDBP}) x/5i $pc-6
8996 0x804837f <main+11>: mov %esp,%ebp
8997 0x8048381 <main+13>: push %ecx
8998 0x8048382 <main+14>: sub $0x4,%esp
8999 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
9000 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
9003 @cindex @code{$_}, @code{$__}, and value history
9004 The addresses and contents printed by the @code{x} command are not saved
9005 in the value history because there is often too much of them and they
9006 would get in the way. Instead, @value{GDBN} makes these values available for
9007 subsequent use in expressions as values of the convenience variables
9008 @code{$_} and @code{$__}. After an @code{x} command, the last address
9009 examined is available for use in expressions in the convenience variable
9010 @code{$_}. The contents of that address, as examined, are available in
9011 the convenience variable @code{$__}.
9013 If the @code{x} command has a repeat count, the address and contents saved
9014 are from the last memory unit printed; this is not the same as the last
9015 address printed if several units were printed on the last line of output.
9017 @cindex remote memory comparison
9018 @cindex target memory comparison
9019 @cindex verify remote memory image
9020 @cindex verify target memory image
9021 When you are debugging a program running on a remote target machine
9022 (@pxref{Remote Debugging}), you may wish to verify the program's image
9023 in the remote machine's memory against the executable file you
9024 downloaded to the target. Or, on any target, you may want to check
9025 whether the program has corrupted its own read-only sections. The
9026 @code{compare-sections} command is provided for such situations.
9029 @kindex compare-sections
9030 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
9031 Compare the data of a loadable section @var{section-name} in the
9032 executable file of the program being debugged with the same section in
9033 the target machine's memory, and report any mismatches. With no
9034 arguments, compares all loadable sections. With an argument of
9035 @code{-r}, compares all loadable read-only sections.
9037 Note: for remote targets, this command can be accelerated if the
9038 target supports computing the CRC checksum of a block of memory
9039 (@pxref{qCRC packet}).
9043 @section Automatic Display
9044 @cindex automatic display
9045 @cindex display of expressions
9047 If you find that you want to print the value of an expression frequently
9048 (to see how it changes), you might want to add it to the @dfn{automatic
9049 display list} so that @value{GDBN} prints its value each time your program stops.
9050 Each expression added to the list is given a number to identify it;
9051 to remove an expression from the list, you specify that number.
9052 The automatic display looks like this:
9056 3: bar[5] = (struct hack *) 0x3804
9060 This display shows item numbers, expressions and their current values. As with
9061 displays you request manually using @code{x} or @code{print}, you can
9062 specify the output format you prefer; in fact, @code{display} decides
9063 whether to use @code{print} or @code{x} depending your format
9064 specification---it uses @code{x} if you specify either the @samp{i}
9065 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
9069 @item display @var{expr}
9070 Add the expression @var{expr} to the list of expressions to display
9071 each time your program stops. @xref{Expressions, ,Expressions}.
9073 @code{display} does not repeat if you press @key{RET} again after using it.
9075 @item display/@var{fmt} @var{expr}
9076 For @var{fmt} specifying only a display format and not a size or
9077 count, add the expression @var{expr} to the auto-display list but
9078 arrange to display it each time in the specified format @var{fmt}.
9079 @xref{Output Formats,,Output Formats}.
9081 @item display/@var{fmt} @var{addr}
9082 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
9083 number of units, add the expression @var{addr} as a memory address to
9084 be examined each time your program stops. Examining means in effect
9085 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
9088 For example, @samp{display/i $pc} can be helpful, to see the machine
9089 instruction about to be executed each time execution stops (@samp{$pc}
9090 is a common name for the program counter; @pxref{Registers, ,Registers}).
9093 @kindex delete display
9095 @item undisplay @var{dnums}@dots{}
9096 @itemx delete display @var{dnums}@dots{}
9097 Remove items from the list of expressions to display. Specify the
9098 numbers of the displays that you want affected with the command
9099 argument @var{dnums}. It can be a single display number, one of the
9100 numbers shown in the first field of the @samp{info display} display;
9101 or it could be a range of display numbers, as in @code{2-4}.
9103 @code{undisplay} does not repeat if you press @key{RET} after using it.
9104 (Otherwise you would just get the error @samp{No display number @dots{}}.)
9106 @kindex disable display
9107 @item disable display @var{dnums}@dots{}
9108 Disable the display of item numbers @var{dnums}. A disabled display
9109 item is not printed automatically, but is not forgotten. It may be
9110 enabled again later. Specify the numbers of the displays that you
9111 want affected with the command argument @var{dnums}. It can be a
9112 single display number, one of the numbers shown in the first field of
9113 the @samp{info display} display; or it could be a range of display
9114 numbers, as in @code{2-4}.
9116 @kindex enable display
9117 @item enable display @var{dnums}@dots{}
9118 Enable display of item numbers @var{dnums}. It becomes effective once
9119 again in auto display of its expression, until you specify otherwise.
9120 Specify the numbers of the displays that you want affected with the
9121 command argument @var{dnums}. It can be a single display number, one
9122 of the numbers shown in the first field of the @samp{info display}
9123 display; or it could be a range of display numbers, as in @code{2-4}.
9126 Display the current values of the expressions on the list, just as is
9127 done when your program stops.
9129 @kindex info display
9131 Print the list of expressions previously set up to display
9132 automatically, each one with its item number, but without showing the
9133 values. This includes disabled expressions, which are marked as such.
9134 It also includes expressions which would not be displayed right now
9135 because they refer to automatic variables not currently available.
9138 @cindex display disabled out of scope
9139 If a display expression refers to local variables, then it does not make
9140 sense outside the lexical context for which it was set up. Such an
9141 expression is disabled when execution enters a context where one of its
9142 variables is not defined. For example, if you give the command
9143 @code{display last_char} while inside a function with an argument
9144 @code{last_char}, @value{GDBN} displays this argument while your program
9145 continues to stop inside that function. When it stops elsewhere---where
9146 there is no variable @code{last_char}---the display is disabled
9147 automatically. The next time your program stops where @code{last_char}
9148 is meaningful, you can enable the display expression once again.
9150 @node Print Settings
9151 @section Print Settings
9153 @cindex format options
9154 @cindex print settings
9155 @value{GDBN} provides the following ways to control how arrays, structures,
9156 and symbols are printed.
9159 These settings are useful for debugging programs in any language:
9163 @item set print address
9164 @itemx set print address on
9165 @cindex print/don't print memory addresses
9166 @value{GDBN} prints memory addresses showing the location of stack
9167 traces, structure values, pointer values, breakpoints, and so forth,
9168 even when it also displays the contents of those addresses. The default
9169 is @code{on}. For example, this is what a stack frame display looks like with
9170 @code{set print address on}:
9175 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
9177 530 if (lquote != def_lquote)
9181 @item set print address off
9182 Do not print addresses when displaying their contents. For example,
9183 this is the same stack frame displayed with @code{set print address off}:
9187 (@value{GDBP}) set print addr off
9189 #0 set_quotes (lq="<<", rq=">>") at input.c:530
9190 530 if (lquote != def_lquote)
9194 You can use @samp{set print address off} to eliminate all machine
9195 dependent displays from the @value{GDBN} interface. For example, with
9196 @code{print address off}, you should get the same text for backtraces on
9197 all machines---whether or not they involve pointer arguments.
9200 @item show print address
9201 Show whether or not addresses are to be printed.
9204 When @value{GDBN} prints a symbolic address, it normally prints the
9205 closest earlier symbol plus an offset. If that symbol does not uniquely
9206 identify the address (for example, it is a name whose scope is a single
9207 source file), you may need to clarify. One way to do this is with
9208 @code{info line}, for example @samp{info line *0x4537}. Alternately,
9209 you can set @value{GDBN} to print the source file and line number when
9210 it prints a symbolic address:
9213 @item set print symbol-filename on
9214 @cindex source file and line of a symbol
9215 @cindex symbol, source file and line
9216 Tell @value{GDBN} to print the source file name and line number of a
9217 symbol in the symbolic form of an address.
9219 @item set print symbol-filename off
9220 Do not print source file name and line number of a symbol. This is the
9223 @item show print symbol-filename
9224 Show whether or not @value{GDBN} will print the source file name and
9225 line number of a symbol in the symbolic form of an address.
9228 Another situation where it is helpful to show symbol filenames and line
9229 numbers is when disassembling code; @value{GDBN} shows you the line
9230 number and source file that corresponds to each instruction.
9232 Also, you may wish to see the symbolic form only if the address being
9233 printed is reasonably close to the closest earlier symbol:
9236 @item set print max-symbolic-offset @var{max-offset}
9237 @itemx set print max-symbolic-offset unlimited
9238 @cindex maximum value for offset of closest symbol
9239 Tell @value{GDBN} to only display the symbolic form of an address if the
9240 offset between the closest earlier symbol and the address is less than
9241 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
9242 to always print the symbolic form of an address if any symbol precedes
9243 it. Zero is equivalent to @code{unlimited}.
9245 @item show print max-symbolic-offset
9246 Ask how large the maximum offset is that @value{GDBN} prints in a
9250 @cindex wild pointer, interpreting
9251 @cindex pointer, finding referent
9252 If you have a pointer and you are not sure where it points, try
9253 @samp{set print symbol-filename on}. Then you can determine the name
9254 and source file location of the variable where it points, using
9255 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
9256 For example, here @value{GDBN} shows that a variable @code{ptt} points
9257 at another variable @code{t}, defined in @file{hi2.c}:
9260 (@value{GDBP}) set print symbol-filename on
9261 (@value{GDBP}) p/a ptt
9262 $4 = 0xe008 <t in hi2.c>
9266 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
9267 does not show the symbol name and filename of the referent, even with
9268 the appropriate @code{set print} options turned on.
9271 You can also enable @samp{/a}-like formatting all the time using
9272 @samp{set print symbol on}:
9275 @item set print symbol on
9276 Tell @value{GDBN} to print the symbol corresponding to an address, if
9279 @item set print symbol off
9280 Tell @value{GDBN} not to print the symbol corresponding to an
9281 address. In this mode, @value{GDBN} will still print the symbol
9282 corresponding to pointers to functions. This is the default.
9284 @item show print symbol
9285 Show whether @value{GDBN} will display the symbol corresponding to an
9289 Other settings control how different kinds of objects are printed:
9292 @item set print array
9293 @itemx set print array on
9294 @cindex pretty print arrays
9295 Pretty print arrays. This format is more convenient to read,
9296 but uses more space. The default is off.
9298 @item set print array off
9299 Return to compressed format for arrays.
9301 @item show print array
9302 Show whether compressed or pretty format is selected for displaying
9305 @cindex print array indexes
9306 @item set print array-indexes
9307 @itemx set print array-indexes on
9308 Print the index of each element when displaying arrays. May be more
9309 convenient to locate a given element in the array or quickly find the
9310 index of a given element in that printed array. The default is off.
9312 @item set print array-indexes off
9313 Stop printing element indexes when displaying arrays.
9315 @item show print array-indexes
9316 Show whether the index of each element is printed when displaying
9319 @item set print elements @var{number-of-elements}
9320 @itemx set print elements unlimited
9321 @cindex number of array elements to print
9322 @cindex limit on number of printed array elements
9323 Set a limit on how many elements of an array @value{GDBN} will print.
9324 If @value{GDBN} is printing a large array, it stops printing after it has
9325 printed the number of elements set by the @code{set print elements} command.
9326 This limit also applies to the display of strings.
9327 When @value{GDBN} starts, this limit is set to 200.
9328 Setting @var{number-of-elements} to @code{unlimited} or zero means
9329 that the number of elements to print is unlimited.
9331 @item show print elements
9332 Display the number of elements of a large array that @value{GDBN} will print.
9333 If the number is 0, then the printing is unlimited.
9335 @item set print frame-arguments @var{value}
9336 @kindex set print frame-arguments
9337 @cindex printing frame argument values
9338 @cindex print all frame argument values
9339 @cindex print frame argument values for scalars only
9340 @cindex do not print frame argument values
9341 This command allows to control how the values of arguments are printed
9342 when the debugger prints a frame (@pxref{Frames}). The possible
9347 The values of all arguments are printed.
9350 Print the value of an argument only if it is a scalar. The value of more
9351 complex arguments such as arrays, structures, unions, etc, is replaced
9352 by @code{@dots{}}. This is the default. Here is an example where
9353 only scalar arguments are shown:
9356 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9361 None of the argument values are printed. Instead, the value of each argument
9362 is replaced by @code{@dots{}}. In this case, the example above now becomes:
9365 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
9370 By default, only scalar arguments are printed. This command can be used
9371 to configure the debugger to print the value of all arguments, regardless
9372 of their type. However, it is often advantageous to not print the value
9373 of more complex parameters. For instance, it reduces the amount of
9374 information printed in each frame, making the backtrace more readable.
9375 Also, it improves performance when displaying Ada frames, because
9376 the computation of large arguments can sometimes be CPU-intensive,
9377 especially in large applications. Setting @code{print frame-arguments}
9378 to @code{scalars} (the default) or @code{none} avoids this computation,
9379 thus speeding up the display of each Ada frame.
9381 @item show print frame-arguments
9382 Show how the value of arguments should be displayed when printing a frame.
9384 @item set print raw frame-arguments on
9385 Print frame arguments in raw, non pretty-printed, form.
9387 @item set print raw frame-arguments off
9388 Print frame arguments in pretty-printed form, if there is a pretty-printer
9389 for the value (@pxref{Pretty Printing}),
9390 otherwise print the value in raw form.
9391 This is the default.
9393 @item show print raw frame-arguments
9394 Show whether to print frame arguments in raw form.
9396 @anchor{set print entry-values}
9397 @item set print entry-values @var{value}
9398 @kindex set print entry-values
9399 Set printing of frame argument values at function entry. In some cases
9400 @value{GDBN} can determine the value of function argument which was passed by
9401 the function caller, even if the value was modified inside the called function
9402 and therefore is different. With optimized code, the current value could be
9403 unavailable, but the entry value may still be known.
9405 The default value is @code{default} (see below for its description). Older
9406 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
9407 this feature will behave in the @code{default} setting the same way as with the
9410 This functionality is currently supported only by DWARF 2 debugging format and
9411 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9412 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9415 The @var{value} parameter can be one of the following:
9419 Print only actual parameter values, never print values from function entry
9423 #0 different (val=6)
9424 #0 lost (val=<optimized out>)
9426 #0 invalid (val=<optimized out>)
9430 Print only parameter values from function entry point. The actual parameter
9431 values are never printed.
9433 #0 equal (val@@entry=5)
9434 #0 different (val@@entry=5)
9435 #0 lost (val@@entry=5)
9436 #0 born (val@@entry=<optimized out>)
9437 #0 invalid (val@@entry=<optimized out>)
9441 Print only parameter values from function entry point. If value from function
9442 entry point is not known while the actual value is known, print the actual
9443 value for such parameter.
9445 #0 equal (val@@entry=5)
9446 #0 different (val@@entry=5)
9447 #0 lost (val@@entry=5)
9449 #0 invalid (val@@entry=<optimized out>)
9453 Print actual parameter values. If actual parameter value is not known while
9454 value from function entry point is known, print the entry point value for such
9458 #0 different (val=6)
9459 #0 lost (val@@entry=5)
9461 #0 invalid (val=<optimized out>)
9465 Always print both the actual parameter value and its value from function entry
9466 point, even if values of one or both are not available due to compiler
9469 #0 equal (val=5, val@@entry=5)
9470 #0 different (val=6, val@@entry=5)
9471 #0 lost (val=<optimized out>, val@@entry=5)
9472 #0 born (val=10, val@@entry=<optimized out>)
9473 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
9477 Print the actual parameter value if it is known and also its value from
9478 function entry point if it is known. If neither is known, print for the actual
9479 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
9480 values are known and identical, print the shortened
9481 @code{param=param@@entry=VALUE} notation.
9483 #0 equal (val=val@@entry=5)
9484 #0 different (val=6, val@@entry=5)
9485 #0 lost (val@@entry=5)
9487 #0 invalid (val=<optimized out>)
9491 Always print the actual parameter value. Print also its value from function
9492 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
9493 if both values are known and identical, print the shortened
9494 @code{param=param@@entry=VALUE} notation.
9496 #0 equal (val=val@@entry=5)
9497 #0 different (val=6, val@@entry=5)
9498 #0 lost (val=<optimized out>, val@@entry=5)
9500 #0 invalid (val=<optimized out>)
9504 For analysis messages on possible failures of frame argument values at function
9505 entry resolution see @ref{set debug entry-values}.
9507 @item show print entry-values
9508 Show the method being used for printing of frame argument values at function
9511 @item set print repeats @var{number-of-repeats}
9512 @itemx set print repeats unlimited
9513 @cindex repeated array elements
9514 Set the threshold for suppressing display of repeated array
9515 elements. When the number of consecutive identical elements of an
9516 array exceeds the threshold, @value{GDBN} prints the string
9517 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
9518 identical repetitions, instead of displaying the identical elements
9519 themselves. Setting the threshold to @code{unlimited} or zero will
9520 cause all elements to be individually printed. The default threshold
9523 @item show print repeats
9524 Display the current threshold for printing repeated identical
9527 @item set print null-stop
9528 @cindex @sc{null} elements in arrays
9529 Cause @value{GDBN} to stop printing the characters of an array when the first
9530 @sc{null} is encountered. This is useful when large arrays actually
9531 contain only short strings.
9534 @item show print null-stop
9535 Show whether @value{GDBN} stops printing an array on the first
9536 @sc{null} character.
9538 @item set print pretty on
9539 @cindex print structures in indented form
9540 @cindex indentation in structure display
9541 Cause @value{GDBN} to print structures in an indented format with one member
9542 per line, like this:
9557 @item set print pretty off
9558 Cause @value{GDBN} to print structures in a compact format, like this:
9562 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
9563 meat = 0x54 "Pork"@}
9568 This is the default format.
9570 @item show print pretty
9571 Show which format @value{GDBN} is using to print structures.
9573 @item set print sevenbit-strings on
9574 @cindex eight-bit characters in strings
9575 @cindex octal escapes in strings
9576 Print using only seven-bit characters; if this option is set,
9577 @value{GDBN} displays any eight-bit characters (in strings or
9578 character values) using the notation @code{\}@var{nnn}. This setting is
9579 best if you are working in English (@sc{ascii}) and you use the
9580 high-order bit of characters as a marker or ``meta'' bit.
9582 @item set print sevenbit-strings off
9583 Print full eight-bit characters. This allows the use of more
9584 international character sets, and is the default.
9586 @item show print sevenbit-strings
9587 Show whether or not @value{GDBN} is printing only seven-bit characters.
9589 @item set print union on
9590 @cindex unions in structures, printing
9591 Tell @value{GDBN} to print unions which are contained in structures
9592 and other unions. This is the default setting.
9594 @item set print union off
9595 Tell @value{GDBN} not to print unions which are contained in
9596 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
9599 @item show print union
9600 Ask @value{GDBN} whether or not it will print unions which are contained in
9601 structures and other unions.
9603 For example, given the declarations
9606 typedef enum @{Tree, Bug@} Species;
9607 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
9608 typedef enum @{Caterpillar, Cocoon, Butterfly@}
9619 struct thing foo = @{Tree, @{Acorn@}@};
9623 with @code{set print union on} in effect @samp{p foo} would print
9626 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
9630 and with @code{set print union off} in effect it would print
9633 $1 = @{it = Tree, form = @{...@}@}
9637 @code{set print union} affects programs written in C-like languages
9643 These settings are of interest when debugging C@t{++} programs:
9646 @cindex demangling C@t{++} names
9647 @item set print demangle
9648 @itemx set print demangle on
9649 Print C@t{++} names in their source form rather than in the encoded
9650 (``mangled'') form passed to the assembler and linker for type-safe
9651 linkage. The default is on.
9653 @item show print demangle
9654 Show whether C@t{++} names are printed in mangled or demangled form.
9656 @item set print asm-demangle
9657 @itemx set print asm-demangle on
9658 Print C@t{++} names in their source form rather than their mangled form, even
9659 in assembler code printouts such as instruction disassemblies.
9662 @item show print asm-demangle
9663 Show whether C@t{++} names in assembly listings are printed in mangled
9666 @cindex C@t{++} symbol decoding style
9667 @cindex symbol decoding style, C@t{++}
9668 @kindex set demangle-style
9669 @item set demangle-style @var{style}
9670 Choose among several encoding schemes used by different compilers to
9671 represent C@t{++} names. The choices for @var{style} are currently:
9675 Allow @value{GDBN} to choose a decoding style by inspecting your program.
9676 This is the default.
9679 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
9682 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
9685 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
9688 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
9689 @strong{Warning:} this setting alone is not sufficient to allow
9690 debugging @code{cfront}-generated executables. @value{GDBN} would
9691 require further enhancement to permit that.
9694 If you omit @var{style}, you will see a list of possible formats.
9696 @item show demangle-style
9697 Display the encoding style currently in use for decoding C@t{++} symbols.
9699 @item set print object
9700 @itemx set print object on
9701 @cindex derived type of an object, printing
9702 @cindex display derived types
9703 When displaying a pointer to an object, identify the @emph{actual}
9704 (derived) type of the object rather than the @emph{declared} type, using
9705 the virtual function table. Note that the virtual function table is
9706 required---this feature can only work for objects that have run-time
9707 type identification; a single virtual method in the object's declared
9708 type is sufficient. Note that this setting is also taken into account when
9709 working with variable objects via MI (@pxref{GDB/MI}).
9711 @item set print object off
9712 Display only the declared type of objects, without reference to the
9713 virtual function table. This is the default setting.
9715 @item show print object
9716 Show whether actual, or declared, object types are displayed.
9718 @item set print static-members
9719 @itemx set print static-members on
9720 @cindex static members of C@t{++} objects
9721 Print static members when displaying a C@t{++} object. The default is on.
9723 @item set print static-members off
9724 Do not print static members when displaying a C@t{++} object.
9726 @item show print static-members
9727 Show whether C@t{++} static members are printed or not.
9729 @item set print pascal_static-members
9730 @itemx set print pascal_static-members on
9731 @cindex static members of Pascal objects
9732 @cindex Pascal objects, static members display
9733 Print static members when displaying a Pascal object. The default is on.
9735 @item set print pascal_static-members off
9736 Do not print static members when displaying a Pascal object.
9738 @item show print pascal_static-members
9739 Show whether Pascal static members are printed or not.
9741 @c These don't work with HP ANSI C++ yet.
9742 @item set print vtbl
9743 @itemx set print vtbl on
9744 @cindex pretty print C@t{++} virtual function tables
9745 @cindex virtual functions (C@t{++}) display
9746 @cindex VTBL display
9747 Pretty print C@t{++} virtual function tables. The default is off.
9748 (The @code{vtbl} commands do not work on programs compiled with the HP
9749 ANSI C@t{++} compiler (@code{aCC}).)
9751 @item set print vtbl off
9752 Do not pretty print C@t{++} virtual function tables.
9754 @item show print vtbl
9755 Show whether C@t{++} virtual function tables are pretty printed, or not.
9758 @node Pretty Printing
9759 @section Pretty Printing
9761 @value{GDBN} provides a mechanism to allow pretty-printing of values using
9762 Python code. It greatly simplifies the display of complex objects. This
9763 mechanism works for both MI and the CLI.
9766 * Pretty-Printer Introduction:: Introduction to pretty-printers
9767 * Pretty-Printer Example:: An example pretty-printer
9768 * Pretty-Printer Commands:: Pretty-printer commands
9771 @node Pretty-Printer Introduction
9772 @subsection Pretty-Printer Introduction
9774 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
9775 registered for the value. If there is then @value{GDBN} invokes the
9776 pretty-printer to print the value. Otherwise the value is printed normally.
9778 Pretty-printers are normally named. This makes them easy to manage.
9779 The @samp{info pretty-printer} command will list all the installed
9780 pretty-printers with their names.
9781 If a pretty-printer can handle multiple data types, then its
9782 @dfn{subprinters} are the printers for the individual data types.
9783 Each such subprinter has its own name.
9784 The format of the name is @var{printer-name};@var{subprinter-name}.
9786 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
9787 Typically they are automatically loaded and registered when the corresponding
9788 debug information is loaded, thus making them available without having to
9789 do anything special.
9791 There are three places where a pretty-printer can be registered.
9795 Pretty-printers registered globally are available when debugging
9799 Pretty-printers registered with a program space are available only
9800 when debugging that program.
9801 @xref{Progspaces In Python}, for more details on program spaces in Python.
9804 Pretty-printers registered with an objfile are loaded and unloaded
9805 with the corresponding objfile (e.g., shared library).
9806 @xref{Objfiles In Python}, for more details on objfiles in Python.
9809 @xref{Selecting Pretty-Printers}, for further information on how
9810 pretty-printers are selected,
9812 @xref{Writing a Pretty-Printer}, for implementing pretty printers
9815 @node Pretty-Printer Example
9816 @subsection Pretty-Printer Example
9818 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
9821 (@value{GDBP}) print s
9823 static npos = 4294967295,
9825 <std::allocator<char>> = @{
9826 <__gnu_cxx::new_allocator<char>> = @{
9827 <No data fields>@}, <No data fields>
9829 members of std::basic_string<char, std::char_traits<char>,
9830 std::allocator<char> >::_Alloc_hider:
9831 _M_p = 0x804a014 "abcd"
9836 With a pretty-printer for @code{std::string} only the contents are printed:
9839 (@value{GDBP}) print s
9843 @node Pretty-Printer Commands
9844 @subsection Pretty-Printer Commands
9845 @cindex pretty-printer commands
9848 @kindex info pretty-printer
9849 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9850 Print the list of installed pretty-printers.
9851 This includes disabled pretty-printers, which are marked as such.
9853 @var{object-regexp} is a regular expression matching the objects
9854 whose pretty-printers to list.
9855 Objects can be @code{global}, the program space's file
9856 (@pxref{Progspaces In Python}),
9857 and the object files within that program space (@pxref{Objfiles In Python}).
9858 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
9859 looks up a printer from these three objects.
9861 @var{name-regexp} is a regular expression matching the name of the printers
9864 @kindex disable pretty-printer
9865 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9866 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9867 A disabled pretty-printer is not forgotten, it may be enabled again later.
9869 @kindex enable pretty-printer
9870 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9871 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9876 Suppose we have three pretty-printers installed: one from library1.so
9877 named @code{foo} that prints objects of type @code{foo}, and
9878 another from library2.so named @code{bar} that prints two types of objects,
9879 @code{bar1} and @code{bar2}.
9882 (gdb) info pretty-printer
9889 (gdb) info pretty-printer library2
9894 (gdb) disable pretty-printer library1
9896 2 of 3 printers enabled
9897 (gdb) info pretty-printer
9904 (gdb) disable pretty-printer library2 bar:bar1
9906 1 of 3 printers enabled
9907 (gdb) info pretty-printer library2
9914 (gdb) disable pretty-printer library2 bar
9916 0 of 3 printers enabled
9917 (gdb) info pretty-printer library2
9926 Note that for @code{bar} the entire printer can be disabled,
9927 as can each individual subprinter.
9930 @section Value History
9932 @cindex value history
9933 @cindex history of values printed by @value{GDBN}
9934 Values printed by the @code{print} command are saved in the @value{GDBN}
9935 @dfn{value history}. This allows you to refer to them in other expressions.
9936 Values are kept until the symbol table is re-read or discarded
9937 (for example with the @code{file} or @code{symbol-file} commands).
9938 When the symbol table changes, the value history is discarded,
9939 since the values may contain pointers back to the types defined in the
9944 @cindex history number
9945 The values printed are given @dfn{history numbers} by which you can
9946 refer to them. These are successive integers starting with one.
9947 @code{print} shows you the history number assigned to a value by
9948 printing @samp{$@var{num} = } before the value; here @var{num} is the
9951 To refer to any previous value, use @samp{$} followed by the value's
9952 history number. The way @code{print} labels its output is designed to
9953 remind you of this. Just @code{$} refers to the most recent value in
9954 the history, and @code{$$} refers to the value before that.
9955 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
9956 is the value just prior to @code{$$}, @code{$$1} is equivalent to
9957 @code{$$}, and @code{$$0} is equivalent to @code{$}.
9959 For example, suppose you have just printed a pointer to a structure and
9960 want to see the contents of the structure. It suffices to type
9966 If you have a chain of structures where the component @code{next} points
9967 to the next one, you can print the contents of the next one with this:
9974 You can print successive links in the chain by repeating this
9975 command---which you can do by just typing @key{RET}.
9977 Note that the history records values, not expressions. If the value of
9978 @code{x} is 4 and you type these commands:
9986 then the value recorded in the value history by the @code{print} command
9987 remains 4 even though the value of @code{x} has changed.
9992 Print the last ten values in the value history, with their item numbers.
9993 This is like @samp{p@ $$9} repeated ten times, except that @code{show
9994 values} does not change the history.
9996 @item show values @var{n}
9997 Print ten history values centered on history item number @var{n}.
10000 Print ten history values just after the values last printed. If no more
10001 values are available, @code{show values +} produces no display.
10004 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
10005 same effect as @samp{show values +}.
10007 @node Convenience Vars
10008 @section Convenience Variables
10010 @cindex convenience variables
10011 @cindex user-defined variables
10012 @value{GDBN} provides @dfn{convenience variables} that you can use within
10013 @value{GDBN} to hold on to a value and refer to it later. These variables
10014 exist entirely within @value{GDBN}; they are not part of your program, and
10015 setting a convenience variable has no direct effect on further execution
10016 of your program. That is why you can use them freely.
10018 Convenience variables are prefixed with @samp{$}. Any name preceded by
10019 @samp{$} can be used for a convenience variable, unless it is one of
10020 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
10021 (Value history references, in contrast, are @emph{numbers} preceded
10022 by @samp{$}. @xref{Value History, ,Value History}.)
10024 You can save a value in a convenience variable with an assignment
10025 expression, just as you would set a variable in your program.
10029 set $foo = *object_ptr
10033 would save in @code{$foo} the value contained in the object pointed to by
10036 Using a convenience variable for the first time creates it, but its
10037 value is @code{void} until you assign a new value. You can alter the
10038 value with another assignment at any time.
10040 Convenience variables have no fixed types. You can assign a convenience
10041 variable any type of value, including structures and arrays, even if
10042 that variable already has a value of a different type. The convenience
10043 variable, when used as an expression, has the type of its current value.
10046 @kindex show convenience
10047 @cindex show all user variables and functions
10048 @item show convenience
10049 Print a list of convenience variables used so far, and their values,
10050 as well as a list of the convenience functions.
10051 Abbreviated @code{show conv}.
10053 @kindex init-if-undefined
10054 @cindex convenience variables, initializing
10055 @item init-if-undefined $@var{variable} = @var{expression}
10056 Set a convenience variable if it has not already been set. This is useful
10057 for user-defined commands that keep some state. It is similar, in concept,
10058 to using local static variables with initializers in C (except that
10059 convenience variables are global). It can also be used to allow users to
10060 override default values used in a command script.
10062 If the variable is already defined then the expression is not evaluated so
10063 any side-effects do not occur.
10066 One of the ways to use a convenience variable is as a counter to be
10067 incremented or a pointer to be advanced. For example, to print
10068 a field from successive elements of an array of structures:
10072 print bar[$i++]->contents
10076 Repeat that command by typing @key{RET}.
10078 Some convenience variables are created automatically by @value{GDBN} and given
10079 values likely to be useful.
10082 @vindex $_@r{, convenience variable}
10084 The variable @code{$_} is automatically set by the @code{x} command to
10085 the last address examined (@pxref{Memory, ,Examining Memory}). Other
10086 commands which provide a default address for @code{x} to examine also
10087 set @code{$_} to that address; these commands include @code{info line}
10088 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
10089 except when set by the @code{x} command, in which case it is a pointer
10090 to the type of @code{$__}.
10092 @vindex $__@r{, convenience variable}
10094 The variable @code{$__} is automatically set by the @code{x} command
10095 to the value found in the last address examined. Its type is chosen
10096 to match the format in which the data was printed.
10099 @vindex $_exitcode@r{, convenience variable}
10100 When the program being debugged terminates normally, @value{GDBN}
10101 automatically sets this variable to the exit code of the program, and
10102 resets @code{$_exitsignal} to @code{void}.
10105 @vindex $_exitsignal@r{, convenience variable}
10106 When the program being debugged dies due to an uncaught signal,
10107 @value{GDBN} automatically sets this variable to that signal's number,
10108 and resets @code{$_exitcode} to @code{void}.
10110 To distinguish between whether the program being debugged has exited
10111 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
10112 @code{$_exitsignal} is not @code{void}), the convenience function
10113 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
10114 Functions}). For example, considering the following source code:
10117 #include <signal.h>
10120 main (int argc, char *argv[])
10127 A valid way of telling whether the program being debugged has exited
10128 or signalled would be:
10131 (@value{GDBP}) define has_exited_or_signalled
10132 Type commands for definition of ``has_exited_or_signalled''.
10133 End with a line saying just ``end''.
10134 >if $_isvoid ($_exitsignal)
10135 >echo The program has exited\n
10137 >echo The program has signalled\n
10143 Program terminated with signal SIGALRM, Alarm clock.
10144 The program no longer exists.
10145 (@value{GDBP}) has_exited_or_signalled
10146 The program has signalled
10149 As can be seen, @value{GDBN} correctly informs that the program being
10150 debugged has signalled, since it calls @code{raise} and raises a
10151 @code{SIGALRM} signal. If the program being debugged had not called
10152 @code{raise}, then @value{GDBN} would report a normal exit:
10155 (@value{GDBP}) has_exited_or_signalled
10156 The program has exited
10160 The variable @code{$_exception} is set to the exception object being
10161 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
10164 @itemx $_probe_arg0@dots{}$_probe_arg11
10165 Arguments to a static probe. @xref{Static Probe Points}.
10168 @vindex $_sdata@r{, inspect, convenience variable}
10169 The variable @code{$_sdata} contains extra collected static tracepoint
10170 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
10171 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
10172 if extra static tracepoint data has not been collected.
10175 @vindex $_siginfo@r{, convenience variable}
10176 The variable @code{$_siginfo} contains extra signal information
10177 (@pxref{extra signal information}). Note that @code{$_siginfo}
10178 could be empty, if the application has not yet received any signals.
10179 For example, it will be empty before you execute the @code{run} command.
10182 @vindex $_tlb@r{, convenience variable}
10183 The variable @code{$_tlb} is automatically set when debugging
10184 applications running on MS-Windows in native mode or connected to
10185 gdbserver that supports the @code{qGetTIBAddr} request.
10186 @xref{General Query Packets}.
10187 This variable contains the address of the thread information block.
10191 On HP-UX systems, if you refer to a function or variable name that
10192 begins with a dollar sign, @value{GDBN} searches for a user or system
10193 name first, before it searches for a convenience variable.
10195 @node Convenience Funs
10196 @section Convenience Functions
10198 @cindex convenience functions
10199 @value{GDBN} also supplies some @dfn{convenience functions}. These
10200 have a syntax similar to convenience variables. A convenience
10201 function can be used in an expression just like an ordinary function;
10202 however, a convenience function is implemented internally to
10205 These functions do not require @value{GDBN} to be configured with
10206 @code{Python} support, which means that they are always available.
10210 @item $_isvoid (@var{expr})
10211 @findex $_isvoid@r{, convenience function}
10212 Return one if the expression @var{expr} is @code{void}. Otherwise it
10215 A @code{void} expression is an expression where the type of the result
10216 is @code{void}. For example, you can examine a convenience variable
10217 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
10221 (@value{GDBP}) print $_exitcode
10223 (@value{GDBP}) print $_isvoid ($_exitcode)
10226 Starting program: ./a.out
10227 [Inferior 1 (process 29572) exited normally]
10228 (@value{GDBP}) print $_exitcode
10230 (@value{GDBP}) print $_isvoid ($_exitcode)
10234 In the example above, we used @code{$_isvoid} to check whether
10235 @code{$_exitcode} is @code{void} before and after the execution of the
10236 program being debugged. Before the execution there is no exit code to
10237 be examined, therefore @code{$_exitcode} is @code{void}. After the
10238 execution the program being debugged returned zero, therefore
10239 @code{$_exitcode} is zero, which means that it is not @code{void}
10242 The @code{void} expression can also be a call of a function from the
10243 program being debugged. For example, given the following function:
10252 The result of calling it inside @value{GDBN} is @code{void}:
10255 (@value{GDBP}) print foo ()
10257 (@value{GDBP}) print $_isvoid (foo ())
10259 (@value{GDBP}) set $v = foo ()
10260 (@value{GDBP}) print $v
10262 (@value{GDBP}) print $_isvoid ($v)
10268 These functions require @value{GDBN} to be configured with
10269 @code{Python} support.
10273 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
10274 @findex $_memeq@r{, convenience function}
10275 Returns one if the @var{length} bytes at the addresses given by
10276 @var{buf1} and @var{buf2} are equal.
10277 Otherwise it returns zero.
10279 @item $_regex(@var{str}, @var{regex})
10280 @findex $_regex@r{, convenience function}
10281 Returns one if the string @var{str} matches the regular expression
10282 @var{regex}. Otherwise it returns zero.
10283 The syntax of the regular expression is that specified by @code{Python}'s
10284 regular expression support.
10286 @item $_streq(@var{str1}, @var{str2})
10287 @findex $_streq@r{, convenience function}
10288 Returns one if the strings @var{str1} and @var{str2} are equal.
10289 Otherwise it returns zero.
10291 @item $_strlen(@var{str})
10292 @findex $_strlen@r{, convenience function}
10293 Returns the length of string @var{str}.
10295 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10296 @findex $_caller_is@r{, convenience function}
10297 Returns one if the calling function's name is equal to @var{name}.
10298 Otherwise it returns zero.
10300 If the optional argument @var{number_of_frames} is provided,
10301 it is the number of frames up in the stack to look.
10309 at testsuite/gdb.python/py-caller-is.c:21
10310 #1 0x00000000004005a0 in middle_func ()
10311 at testsuite/gdb.python/py-caller-is.c:27
10312 #2 0x00000000004005ab in top_func ()
10313 at testsuite/gdb.python/py-caller-is.c:33
10314 #3 0x00000000004005b6 in main ()
10315 at testsuite/gdb.python/py-caller-is.c:39
10316 (gdb) print $_caller_is ("middle_func")
10318 (gdb) print $_caller_is ("top_func", 2)
10322 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10323 @findex $_caller_matches@r{, convenience function}
10324 Returns one if the calling function's name matches the regular expression
10325 @var{regexp}. Otherwise it returns zero.
10327 If the optional argument @var{number_of_frames} is provided,
10328 it is the number of frames up in the stack to look.
10331 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10332 @findex $_any_caller_is@r{, convenience function}
10333 Returns one if any calling function's name is equal to @var{name}.
10334 Otherwise it returns zero.
10336 If the optional argument @var{number_of_frames} is provided,
10337 it is the number of frames up in the stack to look.
10340 This function differs from @code{$_caller_is} in that this function
10341 checks all stack frames from the immediate caller to the frame specified
10342 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
10343 frame specified by @var{number_of_frames}.
10345 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10346 @findex $_any_caller_matches@r{, convenience function}
10347 Returns one if any calling function's name matches the regular expression
10348 @var{regexp}. Otherwise it returns zero.
10350 If the optional argument @var{number_of_frames} is provided,
10351 it is the number of frames up in the stack to look.
10354 This function differs from @code{$_caller_matches} in that this function
10355 checks all stack frames from the immediate caller to the frame specified
10356 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
10357 frame specified by @var{number_of_frames}.
10361 @value{GDBN} provides the ability to list and get help on
10362 convenience functions.
10365 @item help function
10366 @kindex help function
10367 @cindex show all convenience functions
10368 Print a list of all convenience functions.
10375 You can refer to machine register contents, in expressions, as variables
10376 with names starting with @samp{$}. The names of registers are different
10377 for each machine; use @code{info registers} to see the names used on
10381 @kindex info registers
10382 @item info registers
10383 Print the names and values of all registers except floating-point
10384 and vector registers (in the selected stack frame).
10386 @kindex info all-registers
10387 @cindex floating point registers
10388 @item info all-registers
10389 Print the names and values of all registers, including floating-point
10390 and vector registers (in the selected stack frame).
10392 @item info registers @var{regname} @dots{}
10393 Print the @dfn{relativized} value of each specified register @var{regname}.
10394 As discussed in detail below, register values are normally relative to
10395 the selected stack frame. The @var{regname} may be any register name valid on
10396 the machine you are using, with or without the initial @samp{$}.
10399 @anchor{standard registers}
10400 @cindex stack pointer register
10401 @cindex program counter register
10402 @cindex process status register
10403 @cindex frame pointer register
10404 @cindex standard registers
10405 @value{GDBN} has four ``standard'' register names that are available (in
10406 expressions) on most machines---whenever they do not conflict with an
10407 architecture's canonical mnemonics for registers. The register names
10408 @code{$pc} and @code{$sp} are used for the program counter register and
10409 the stack pointer. @code{$fp} is used for a register that contains a
10410 pointer to the current stack frame, and @code{$ps} is used for a
10411 register that contains the processor status. For example,
10412 you could print the program counter in hex with
10419 or print the instruction to be executed next with
10426 or add four to the stack pointer@footnote{This is a way of removing
10427 one word from the stack, on machines where stacks grow downward in
10428 memory (most machines, nowadays). This assumes that the innermost
10429 stack frame is selected; setting @code{$sp} is not allowed when other
10430 stack frames are selected. To pop entire frames off the stack,
10431 regardless of machine architecture, use @code{return};
10432 see @ref{Returning, ,Returning from a Function}.} with
10438 Whenever possible, these four standard register names are available on
10439 your machine even though the machine has different canonical mnemonics,
10440 so long as there is no conflict. The @code{info registers} command
10441 shows the canonical names. For example, on the SPARC, @code{info
10442 registers} displays the processor status register as @code{$psr} but you
10443 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
10444 is an alias for the @sc{eflags} register.
10446 @value{GDBN} always considers the contents of an ordinary register as an
10447 integer when the register is examined in this way. Some machines have
10448 special registers which can hold nothing but floating point; these
10449 registers are considered to have floating point values. There is no way
10450 to refer to the contents of an ordinary register as floating point value
10451 (although you can @emph{print} it as a floating point value with
10452 @samp{print/f $@var{regname}}).
10454 Some registers have distinct ``raw'' and ``virtual'' data formats. This
10455 means that the data format in which the register contents are saved by
10456 the operating system is not the same one that your program normally
10457 sees. For example, the registers of the 68881 floating point
10458 coprocessor are always saved in ``extended'' (raw) format, but all C
10459 programs expect to work with ``double'' (virtual) format. In such
10460 cases, @value{GDBN} normally works with the virtual format only (the format
10461 that makes sense for your program), but the @code{info registers} command
10462 prints the data in both formats.
10464 @cindex SSE registers (x86)
10465 @cindex MMX registers (x86)
10466 Some machines have special registers whose contents can be interpreted
10467 in several different ways. For example, modern x86-based machines
10468 have SSE and MMX registers that can hold several values packed
10469 together in several different formats. @value{GDBN} refers to such
10470 registers in @code{struct} notation:
10473 (@value{GDBP}) print $xmm1
10475 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
10476 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
10477 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
10478 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
10479 v4_int32 = @{0, 20657912, 11, 13@},
10480 v2_int64 = @{88725056443645952, 55834574859@},
10481 uint128 = 0x0000000d0000000b013b36f800000000
10486 To set values of such registers, you need to tell @value{GDBN} which
10487 view of the register you wish to change, as if you were assigning
10488 value to a @code{struct} member:
10491 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
10494 Normally, register values are relative to the selected stack frame
10495 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
10496 value that the register would contain if all stack frames farther in
10497 were exited and their saved registers restored. In order to see the
10498 true contents of hardware registers, you must select the innermost
10499 frame (with @samp{frame 0}).
10501 @cindex caller-saved registers
10502 @cindex call-clobbered registers
10503 @cindex volatile registers
10504 @cindex <not saved> values
10505 Usually ABIs reserve some registers as not needed to be saved by the
10506 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
10507 registers). It may therefore not be possible for @value{GDBN} to know
10508 the value a register had before the call (in other words, in the outer
10509 frame), if the register value has since been changed by the callee.
10510 @value{GDBN} tries to deduce where the inner frame saved
10511 (``callee-saved'') registers, from the debug info, unwind info, or the
10512 machine code generated by your compiler. If some register is not
10513 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
10514 its own knowledge of the ABI, or because the debug/unwind info
10515 explicitly says the register's value is undefined), @value{GDBN}
10516 displays @w{@samp{<not saved>}} as the register's value. With targets
10517 that @value{GDBN} has no knowledge of the register saving convention,
10518 if a register was not saved by the callee, then its value and location
10519 in the outer frame are assumed to be the same of the inner frame.
10520 This is usually harmless, because if the register is call-clobbered,
10521 the caller either does not care what is in the register after the
10522 call, or has code to restore the value that it does care about. Note,
10523 however, that if you change such a register in the outer frame, you
10524 may also be affecting the inner frame. Also, the more ``outer'' the
10525 frame is you're looking at, the more likely a call-clobbered
10526 register's value is to be wrong, in the sense that it doesn't actually
10527 represent the value the register had just before the call.
10529 @node Floating Point Hardware
10530 @section Floating Point Hardware
10531 @cindex floating point
10533 Depending on the configuration, @value{GDBN} may be able to give
10534 you more information about the status of the floating point hardware.
10539 Display hardware-dependent information about the floating
10540 point unit. The exact contents and layout vary depending on the
10541 floating point chip. Currently, @samp{info float} is supported on
10542 the ARM and x86 machines.
10546 @section Vector Unit
10547 @cindex vector unit
10549 Depending on the configuration, @value{GDBN} may be able to give you
10550 more information about the status of the vector unit.
10553 @kindex info vector
10555 Display information about the vector unit. The exact contents and
10556 layout vary depending on the hardware.
10559 @node OS Information
10560 @section Operating System Auxiliary Information
10561 @cindex OS information
10563 @value{GDBN} provides interfaces to useful OS facilities that can help
10564 you debug your program.
10566 @cindex auxiliary vector
10567 @cindex vector, auxiliary
10568 Some operating systems supply an @dfn{auxiliary vector} to programs at
10569 startup. This is akin to the arguments and environment that you
10570 specify for a program, but contains a system-dependent variety of
10571 binary values that tell system libraries important details about the
10572 hardware, operating system, and process. Each value's purpose is
10573 identified by an integer tag; the meanings are well-known but system-specific.
10574 Depending on the configuration and operating system facilities,
10575 @value{GDBN} may be able to show you this information. For remote
10576 targets, this functionality may further depend on the remote stub's
10577 support of the @samp{qXfer:auxv:read} packet, see
10578 @ref{qXfer auxiliary vector read}.
10583 Display the auxiliary vector of the inferior, which can be either a
10584 live process or a core dump file. @value{GDBN} prints each tag value
10585 numerically, and also shows names and text descriptions for recognized
10586 tags. Some values in the vector are numbers, some bit masks, and some
10587 pointers to strings or other data. @value{GDBN} displays each value in the
10588 most appropriate form for a recognized tag, and in hexadecimal for
10589 an unrecognized tag.
10592 On some targets, @value{GDBN} can access operating system-specific
10593 information and show it to you. The types of information available
10594 will differ depending on the type of operating system running on the
10595 target. The mechanism used to fetch the data is described in
10596 @ref{Operating System Information}. For remote targets, this
10597 functionality depends on the remote stub's support of the
10598 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
10602 @item info os @var{infotype}
10604 Display OS information of the requested type.
10606 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
10608 @anchor{linux info os infotypes}
10610 @kindex info os processes
10612 Display the list of processes on the target. For each process,
10613 @value{GDBN} prints the process identifier, the name of the user, the
10614 command corresponding to the process, and the list of processor cores
10615 that the process is currently running on. (To understand what these
10616 properties mean, for this and the following info types, please consult
10617 the general @sc{gnu}/Linux documentation.)
10619 @kindex info os procgroups
10621 Display the list of process groups on the target. For each process,
10622 @value{GDBN} prints the identifier of the process group that it belongs
10623 to, the command corresponding to the process group leader, the process
10624 identifier, and the command line of the process. The list is sorted
10625 first by the process group identifier, then by the process identifier,
10626 so that processes belonging to the same process group are grouped together
10627 and the process group leader is listed first.
10629 @kindex info os threads
10631 Display the list of threads running on the target. For each thread,
10632 @value{GDBN} prints the identifier of the process that the thread
10633 belongs to, the command of the process, the thread identifier, and the
10634 processor core that it is currently running on. The main thread of a
10635 process is not listed.
10637 @kindex info os files
10639 Display the list of open file descriptors on the target. For each
10640 file descriptor, @value{GDBN} prints the identifier of the process
10641 owning the descriptor, the command of the owning process, the value
10642 of the descriptor, and the target of the descriptor.
10644 @kindex info os sockets
10646 Display the list of Internet-domain sockets on the target. For each
10647 socket, @value{GDBN} prints the address and port of the local and
10648 remote endpoints, the current state of the connection, the creator of
10649 the socket, the IP address family of the socket, and the type of the
10652 @kindex info os shm
10654 Display the list of all System V shared-memory regions on the target.
10655 For each shared-memory region, @value{GDBN} prints the region key,
10656 the shared-memory identifier, the access permissions, the size of the
10657 region, the process that created the region, the process that last
10658 attached to or detached from the region, the current number of live
10659 attaches to the region, and the times at which the region was last
10660 attached to, detach from, and changed.
10662 @kindex info os semaphores
10664 Display the list of all System V semaphore sets on the target. For each
10665 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
10666 set identifier, the access permissions, the number of semaphores in the
10667 set, the user and group of the owner and creator of the semaphore set,
10668 and the times at which the semaphore set was operated upon and changed.
10670 @kindex info os msg
10672 Display the list of all System V message queues on the target. For each
10673 message queue, @value{GDBN} prints the message queue key, the message
10674 queue identifier, the access permissions, the current number of bytes
10675 on the queue, the current number of messages on the queue, the processes
10676 that last sent and received a message on the queue, the user and group
10677 of the owner and creator of the message queue, the times at which a
10678 message was last sent and received on the queue, and the time at which
10679 the message queue was last changed.
10681 @kindex info os modules
10683 Display the list of all loaded kernel modules on the target. For each
10684 module, @value{GDBN} prints the module name, the size of the module in
10685 bytes, the number of times the module is used, the dependencies of the
10686 module, the status of the module, and the address of the loaded module
10691 If @var{infotype} is omitted, then list the possible values for
10692 @var{infotype} and the kind of OS information available for each
10693 @var{infotype}. If the target does not return a list of possible
10694 types, this command will report an error.
10697 @node Memory Region Attributes
10698 @section Memory Region Attributes
10699 @cindex memory region attributes
10701 @dfn{Memory region attributes} allow you to describe special handling
10702 required by regions of your target's memory. @value{GDBN} uses
10703 attributes to determine whether to allow certain types of memory
10704 accesses; whether to use specific width accesses; and whether to cache
10705 target memory. By default the description of memory regions is
10706 fetched from the target (if the current target supports this), but the
10707 user can override the fetched regions.
10709 Defined memory regions can be individually enabled and disabled. When a
10710 memory region is disabled, @value{GDBN} uses the default attributes when
10711 accessing memory in that region. Similarly, if no memory regions have
10712 been defined, @value{GDBN} uses the default attributes when accessing
10715 When a memory region is defined, it is given a number to identify it;
10716 to enable, disable, or remove a memory region, you specify that number.
10720 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
10721 Define a memory region bounded by @var{lower} and @var{upper} with
10722 attributes @var{attributes}@dots{}, and add it to the list of regions
10723 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
10724 case: it is treated as the target's maximum memory address.
10725 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
10728 Discard any user changes to the memory regions and use target-supplied
10729 regions, if available, or no regions if the target does not support.
10732 @item delete mem @var{nums}@dots{}
10733 Remove memory regions @var{nums}@dots{} from the list of regions
10734 monitored by @value{GDBN}.
10736 @kindex disable mem
10737 @item disable mem @var{nums}@dots{}
10738 Disable monitoring of memory regions @var{nums}@dots{}.
10739 A disabled memory region is not forgotten.
10740 It may be enabled again later.
10743 @item enable mem @var{nums}@dots{}
10744 Enable monitoring of memory regions @var{nums}@dots{}.
10748 Print a table of all defined memory regions, with the following columns
10752 @item Memory Region Number
10753 @item Enabled or Disabled.
10754 Enabled memory regions are marked with @samp{y}.
10755 Disabled memory regions are marked with @samp{n}.
10758 The address defining the inclusive lower bound of the memory region.
10761 The address defining the exclusive upper bound of the memory region.
10764 The list of attributes set for this memory region.
10769 @subsection Attributes
10771 @subsubsection Memory Access Mode
10772 The access mode attributes set whether @value{GDBN} may make read or
10773 write accesses to a memory region.
10775 While these attributes prevent @value{GDBN} from performing invalid
10776 memory accesses, they do nothing to prevent the target system, I/O DMA,
10777 etc.@: from accessing memory.
10781 Memory is read only.
10783 Memory is write only.
10785 Memory is read/write. This is the default.
10788 @subsubsection Memory Access Size
10789 The access size attribute tells @value{GDBN} to use specific sized
10790 accesses in the memory region. Often memory mapped device registers
10791 require specific sized accesses. If no access size attribute is
10792 specified, @value{GDBN} may use accesses of any size.
10796 Use 8 bit memory accesses.
10798 Use 16 bit memory accesses.
10800 Use 32 bit memory accesses.
10802 Use 64 bit memory accesses.
10805 @c @subsubsection Hardware/Software Breakpoints
10806 @c The hardware/software breakpoint attributes set whether @value{GDBN}
10807 @c will use hardware or software breakpoints for the internal breakpoints
10808 @c used by the step, next, finish, until, etc. commands.
10812 @c Always use hardware breakpoints
10813 @c @item swbreak (default)
10816 @subsubsection Data Cache
10817 The data cache attributes set whether @value{GDBN} will cache target
10818 memory. While this generally improves performance by reducing debug
10819 protocol overhead, it can lead to incorrect results because @value{GDBN}
10820 does not know about volatile variables or memory mapped device
10825 Enable @value{GDBN} to cache target memory.
10827 Disable @value{GDBN} from caching target memory. This is the default.
10830 @subsection Memory Access Checking
10831 @value{GDBN} can be instructed to refuse accesses to memory that is
10832 not explicitly described. This can be useful if accessing such
10833 regions has undesired effects for a specific target, or to provide
10834 better error checking. The following commands control this behaviour.
10837 @kindex set mem inaccessible-by-default
10838 @item set mem inaccessible-by-default [on|off]
10839 If @code{on} is specified, make @value{GDBN} treat memory not
10840 explicitly described by the memory ranges as non-existent and refuse accesses
10841 to such memory. The checks are only performed if there's at least one
10842 memory range defined. If @code{off} is specified, make @value{GDBN}
10843 treat the memory not explicitly described by the memory ranges as RAM.
10844 The default value is @code{on}.
10845 @kindex show mem inaccessible-by-default
10846 @item show mem inaccessible-by-default
10847 Show the current handling of accesses to unknown memory.
10851 @c @subsubsection Memory Write Verification
10852 @c The memory write verification attributes set whether @value{GDBN}
10853 @c will re-reads data after each write to verify the write was successful.
10857 @c @item noverify (default)
10860 @node Dump/Restore Files
10861 @section Copy Between Memory and a File
10862 @cindex dump/restore files
10863 @cindex append data to a file
10864 @cindex dump data to a file
10865 @cindex restore data from a file
10867 You can use the commands @code{dump}, @code{append}, and
10868 @code{restore} to copy data between target memory and a file. The
10869 @code{dump} and @code{append} commands write data to a file, and the
10870 @code{restore} command reads data from a file back into the inferior's
10871 memory. Files may be in binary, Motorola S-record, Intel hex, or
10872 Tektronix Hex format; however, @value{GDBN} can only append to binary
10878 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10879 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
10880 Dump the contents of memory from @var{start_addr} to @var{end_addr},
10881 or the value of @var{expr}, to @var{filename} in the given format.
10883 The @var{format} parameter may be any one of:
10890 Motorola S-record format.
10892 Tektronix Hex format.
10895 @value{GDBN} uses the same definitions of these formats as the
10896 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
10897 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
10901 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10902 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
10903 Append the contents of memory from @var{start_addr} to @var{end_addr},
10904 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
10905 (@value{GDBN} can only append data to files in raw binary form.)
10908 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
10909 Restore the contents of file @var{filename} into memory. The
10910 @code{restore} command can automatically recognize any known @sc{bfd}
10911 file format, except for raw binary. To restore a raw binary file you
10912 must specify the optional keyword @code{binary} after the filename.
10914 If @var{bias} is non-zero, its value will be added to the addresses
10915 contained in the file. Binary files always start at address zero, so
10916 they will be restored at address @var{bias}. Other bfd files have
10917 a built-in location; they will be restored at offset @var{bias}
10918 from that location.
10920 If @var{start} and/or @var{end} are non-zero, then only data between
10921 file offset @var{start} and file offset @var{end} will be restored.
10922 These offsets are relative to the addresses in the file, before
10923 the @var{bias} argument is applied.
10927 @node Core File Generation
10928 @section How to Produce a Core File from Your Program
10929 @cindex dump core from inferior
10931 A @dfn{core file} or @dfn{core dump} is a file that records the memory
10932 image of a running process and its process status (register values
10933 etc.). Its primary use is post-mortem debugging of a program that
10934 crashed while it ran outside a debugger. A program that crashes
10935 automatically produces a core file, unless this feature is disabled by
10936 the user. @xref{Files}, for information on invoking @value{GDBN} in
10937 the post-mortem debugging mode.
10939 Occasionally, you may wish to produce a core file of the program you
10940 are debugging in order to preserve a snapshot of its state.
10941 @value{GDBN} has a special command for that.
10945 @kindex generate-core-file
10946 @item generate-core-file [@var{file}]
10947 @itemx gcore [@var{file}]
10948 Produce a core dump of the inferior process. The optional argument
10949 @var{file} specifies the file name where to put the core dump. If not
10950 specified, the file name defaults to @file{core.@var{pid}}, where
10951 @var{pid} is the inferior process ID.
10953 Note that this command is implemented only for some systems (as of
10954 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
10957 @node Character Sets
10958 @section Character Sets
10959 @cindex character sets
10961 @cindex translating between character sets
10962 @cindex host character set
10963 @cindex target character set
10965 If the program you are debugging uses a different character set to
10966 represent characters and strings than the one @value{GDBN} uses itself,
10967 @value{GDBN} can automatically translate between the character sets for
10968 you. The character set @value{GDBN} uses we call the @dfn{host
10969 character set}; the one the inferior program uses we call the
10970 @dfn{target character set}.
10972 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
10973 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
10974 remote protocol (@pxref{Remote Debugging}) to debug a program
10975 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
10976 then the host character set is Latin-1, and the target character set is
10977 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
10978 target-charset EBCDIC-US}, then @value{GDBN} translates between
10979 @sc{ebcdic} and Latin 1 as you print character or string values, or use
10980 character and string literals in expressions.
10982 @value{GDBN} has no way to automatically recognize which character set
10983 the inferior program uses; you must tell it, using the @code{set
10984 target-charset} command, described below.
10986 Here are the commands for controlling @value{GDBN}'s character set
10990 @item set target-charset @var{charset}
10991 @kindex set target-charset
10992 Set the current target character set to @var{charset}. To display the
10993 list of supported target character sets, type
10994 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
10996 @item set host-charset @var{charset}
10997 @kindex set host-charset
10998 Set the current host character set to @var{charset}.
11000 By default, @value{GDBN} uses a host character set appropriate to the
11001 system it is running on; you can override that default using the
11002 @code{set host-charset} command. On some systems, @value{GDBN} cannot
11003 automatically determine the appropriate host character set. In this
11004 case, @value{GDBN} uses @samp{UTF-8}.
11006 @value{GDBN} can only use certain character sets as its host character
11007 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
11008 @value{GDBN} will list the host character sets it supports.
11010 @item set charset @var{charset}
11011 @kindex set charset
11012 Set the current host and target character sets to @var{charset}. As
11013 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
11014 @value{GDBN} will list the names of the character sets that can be used
11015 for both host and target.
11018 @kindex show charset
11019 Show the names of the current host and target character sets.
11021 @item show host-charset
11022 @kindex show host-charset
11023 Show the name of the current host character set.
11025 @item show target-charset
11026 @kindex show target-charset
11027 Show the name of the current target character set.
11029 @item set target-wide-charset @var{charset}
11030 @kindex set target-wide-charset
11031 Set the current target's wide character set to @var{charset}. This is
11032 the character set used by the target's @code{wchar_t} type. To
11033 display the list of supported wide character sets, type
11034 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
11036 @item show target-wide-charset
11037 @kindex show target-wide-charset
11038 Show the name of the current target's wide character set.
11041 Here is an example of @value{GDBN}'s character set support in action.
11042 Assume that the following source code has been placed in the file
11043 @file{charset-test.c}:
11049 = @{72, 101, 108, 108, 111, 44, 32, 119,
11050 111, 114, 108, 100, 33, 10, 0@};
11051 char ibm1047_hello[]
11052 = @{200, 133, 147, 147, 150, 107, 64, 166,
11053 150, 153, 147, 132, 90, 37, 0@};
11057 printf ("Hello, world!\n");
11061 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
11062 containing the string @samp{Hello, world!} followed by a newline,
11063 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
11065 We compile the program, and invoke the debugger on it:
11068 $ gcc -g charset-test.c -o charset-test
11069 $ gdb -nw charset-test
11070 GNU gdb 2001-12-19-cvs
11071 Copyright 2001 Free Software Foundation, Inc.
11076 We can use the @code{show charset} command to see what character sets
11077 @value{GDBN} is currently using to interpret and display characters and
11081 (@value{GDBP}) show charset
11082 The current host and target character set is `ISO-8859-1'.
11086 For the sake of printing this manual, let's use @sc{ascii} as our
11087 initial character set:
11089 (@value{GDBP}) set charset ASCII
11090 (@value{GDBP}) show charset
11091 The current host and target character set is `ASCII'.
11095 Let's assume that @sc{ascii} is indeed the correct character set for our
11096 host system --- in other words, let's assume that if @value{GDBN} prints
11097 characters using the @sc{ascii} character set, our terminal will display
11098 them properly. Since our current target character set is also
11099 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
11102 (@value{GDBP}) print ascii_hello
11103 $1 = 0x401698 "Hello, world!\n"
11104 (@value{GDBP}) print ascii_hello[0]
11109 @value{GDBN} uses the target character set for character and string
11110 literals you use in expressions:
11113 (@value{GDBP}) print '+'
11118 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
11121 @value{GDBN} relies on the user to tell it which character set the
11122 target program uses. If we print @code{ibm1047_hello} while our target
11123 character set is still @sc{ascii}, we get jibberish:
11126 (@value{GDBP}) print ibm1047_hello
11127 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
11128 (@value{GDBP}) print ibm1047_hello[0]
11133 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
11134 @value{GDBN} tells us the character sets it supports:
11137 (@value{GDBP}) set target-charset
11138 ASCII EBCDIC-US IBM1047 ISO-8859-1
11139 (@value{GDBP}) set target-charset
11142 We can select @sc{ibm1047} as our target character set, and examine the
11143 program's strings again. Now the @sc{ascii} string is wrong, but
11144 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
11145 target character set, @sc{ibm1047}, to the host character set,
11146 @sc{ascii}, and they display correctly:
11149 (@value{GDBP}) set target-charset IBM1047
11150 (@value{GDBP}) show charset
11151 The current host character set is `ASCII'.
11152 The current target character set is `IBM1047'.
11153 (@value{GDBP}) print ascii_hello
11154 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
11155 (@value{GDBP}) print ascii_hello[0]
11157 (@value{GDBP}) print ibm1047_hello
11158 $8 = 0x4016a8 "Hello, world!\n"
11159 (@value{GDBP}) print ibm1047_hello[0]
11164 As above, @value{GDBN} uses the target character set for character and
11165 string literals you use in expressions:
11168 (@value{GDBP}) print '+'
11173 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
11176 @node Caching Target Data
11177 @section Caching Data of Targets
11178 @cindex caching data of targets
11180 @value{GDBN} caches data exchanged between the debugger and a target.
11181 Each cache is associated with the address space of the inferior.
11182 @xref{Inferiors and Programs}, about inferior and address space.
11183 Such caching generally improves performance in remote debugging
11184 (@pxref{Remote Debugging}), because it reduces the overhead of the
11185 remote protocol by bundling memory reads and writes into large chunks.
11186 Unfortunately, simply caching everything would lead to incorrect results,
11187 since @value{GDBN} does not necessarily know anything about volatile
11188 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
11189 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
11191 Therefore, by default, @value{GDBN} only caches data
11192 known to be on the stack@footnote{In non-stop mode, it is moderately
11193 rare for a running thread to modify the stack of a stopped thread
11194 in a way that would interfere with a backtrace, and caching of
11195 stack reads provides a significant speed up of remote backtraces.} or
11196 in the code segment.
11197 Other regions of memory can be explicitly marked as
11198 cacheable; @pxref{Memory Region Attributes}.
11201 @kindex set remotecache
11202 @item set remotecache on
11203 @itemx set remotecache off
11204 This option no longer does anything; it exists for compatibility
11207 @kindex show remotecache
11208 @item show remotecache
11209 Show the current state of the obsolete remotecache flag.
11211 @kindex set stack-cache
11212 @item set stack-cache on
11213 @itemx set stack-cache off
11214 Enable or disable caching of stack accesses. When @code{on}, use
11215 caching. By default, this option is @code{on}.
11217 @kindex show stack-cache
11218 @item show stack-cache
11219 Show the current state of data caching for memory accesses.
11221 @kindex set code-cache
11222 @item set code-cache on
11223 @itemx set code-cache off
11224 Enable or disable caching of code segment accesses. When @code{on},
11225 use caching. By default, this option is @code{on}. This improves
11226 performance of disassembly in remote debugging.
11228 @kindex show code-cache
11229 @item show code-cache
11230 Show the current state of target memory cache for code segment
11233 @kindex info dcache
11234 @item info dcache @r{[}line@r{]}
11235 Print the information about the performance of data cache of the
11236 current inferior's address space. The information displayed
11237 includes the dcache width and depth, and for each cache line, its
11238 number, address, and how many times it was referenced. This
11239 command is useful for debugging the data cache operation.
11241 If a line number is specified, the contents of that line will be
11244 @item set dcache size @var{size}
11245 @cindex dcache size
11246 @kindex set dcache size
11247 Set maximum number of entries in dcache (dcache depth above).
11249 @item set dcache line-size @var{line-size}
11250 @cindex dcache line-size
11251 @kindex set dcache line-size
11252 Set number of bytes each dcache entry caches (dcache width above).
11253 Must be a power of 2.
11255 @item show dcache size
11256 @kindex show dcache size
11257 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
11259 @item show dcache line-size
11260 @kindex show dcache line-size
11261 Show default size of dcache lines.
11265 @node Searching Memory
11266 @section Search Memory
11267 @cindex searching memory
11269 Memory can be searched for a particular sequence of bytes with the
11270 @code{find} command.
11274 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11275 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11276 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
11277 etc. The search begins at address @var{start_addr} and continues for either
11278 @var{len} bytes or through to @var{end_addr} inclusive.
11281 @var{s} and @var{n} are optional parameters.
11282 They may be specified in either order, apart or together.
11285 @item @var{s}, search query size
11286 The size of each search query value.
11292 halfwords (two bytes)
11296 giant words (eight bytes)
11299 All values are interpreted in the current language.
11300 This means, for example, that if the current source language is C/C@t{++}
11301 then searching for the string ``hello'' includes the trailing '\0'.
11303 If the value size is not specified, it is taken from the
11304 value's type in the current language.
11305 This is useful when one wants to specify the search
11306 pattern as a mixture of types.
11307 Note that this means, for example, that in the case of C-like languages
11308 a search for an untyped 0x42 will search for @samp{(int) 0x42}
11309 which is typically four bytes.
11311 @item @var{n}, maximum number of finds
11312 The maximum number of matches to print. The default is to print all finds.
11315 You can use strings as search values. Quote them with double-quotes
11317 The string value is copied into the search pattern byte by byte,
11318 regardless of the endianness of the target and the size specification.
11320 The address of each match found is printed as well as a count of the
11321 number of matches found.
11323 The address of the last value found is stored in convenience variable
11325 A count of the number of matches is stored in @samp{$numfound}.
11327 For example, if stopped at the @code{printf} in this function:
11333 static char hello[] = "hello-hello";
11334 static struct @{ char c; short s; int i; @}
11335 __attribute__ ((packed)) mixed
11336 = @{ 'c', 0x1234, 0x87654321 @};
11337 printf ("%s\n", hello);
11342 you get during debugging:
11345 (gdb) find &hello[0], +sizeof(hello), "hello"
11346 0x804956d <hello.1620+6>
11348 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
11349 0x8049567 <hello.1620>
11350 0x804956d <hello.1620+6>
11352 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
11353 0x8049567 <hello.1620>
11355 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
11356 0x8049560 <mixed.1625>
11358 (gdb) print $numfound
11361 $2 = (void *) 0x8049560
11364 @node Optimized Code
11365 @chapter Debugging Optimized Code
11366 @cindex optimized code, debugging
11367 @cindex debugging optimized code
11369 Almost all compilers support optimization. With optimization
11370 disabled, the compiler generates assembly code that corresponds
11371 directly to your source code, in a simplistic way. As the compiler
11372 applies more powerful optimizations, the generated assembly code
11373 diverges from your original source code. With help from debugging
11374 information generated by the compiler, @value{GDBN} can map from
11375 the running program back to constructs from your original source.
11377 @value{GDBN} is more accurate with optimization disabled. If you
11378 can recompile without optimization, it is easier to follow the
11379 progress of your program during debugging. But, there are many cases
11380 where you may need to debug an optimized version.
11382 When you debug a program compiled with @samp{-g -O}, remember that the
11383 optimizer has rearranged your code; the debugger shows you what is
11384 really there. Do not be too surprised when the execution path does not
11385 exactly match your source file! An extreme example: if you define a
11386 variable, but never use it, @value{GDBN} never sees that
11387 variable---because the compiler optimizes it out of existence.
11389 Some things do not work as well with @samp{-g -O} as with just
11390 @samp{-g}, particularly on machines with instruction scheduling. If in
11391 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
11392 please report it to us as a bug (including a test case!).
11393 @xref{Variables}, for more information about debugging optimized code.
11396 * Inline Functions:: How @value{GDBN} presents inlining
11397 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
11400 @node Inline Functions
11401 @section Inline Functions
11402 @cindex inline functions, debugging
11404 @dfn{Inlining} is an optimization that inserts a copy of the function
11405 body directly at each call site, instead of jumping to a shared
11406 routine. @value{GDBN} displays inlined functions just like
11407 non-inlined functions. They appear in backtraces. You can view their
11408 arguments and local variables, step into them with @code{step}, skip
11409 them with @code{next}, and escape from them with @code{finish}.
11410 You can check whether a function was inlined by using the
11411 @code{info frame} command.
11413 For @value{GDBN} to support inlined functions, the compiler must
11414 record information about inlining in the debug information ---
11415 @value{NGCC} using the @sc{dwarf 2} format does this, and several
11416 other compilers do also. @value{GDBN} only supports inlined functions
11417 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
11418 do not emit two required attributes (@samp{DW_AT_call_file} and
11419 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
11420 function calls with earlier versions of @value{NGCC}. It instead
11421 displays the arguments and local variables of inlined functions as
11422 local variables in the caller.
11424 The body of an inlined function is directly included at its call site;
11425 unlike a non-inlined function, there are no instructions devoted to
11426 the call. @value{GDBN} still pretends that the call site and the
11427 start of the inlined function are different instructions. Stepping to
11428 the call site shows the call site, and then stepping again shows
11429 the first line of the inlined function, even though no additional
11430 instructions are executed.
11432 This makes source-level debugging much clearer; you can see both the
11433 context of the call and then the effect of the call. Only stepping by
11434 a single instruction using @code{stepi} or @code{nexti} does not do
11435 this; single instruction steps always show the inlined body.
11437 There are some ways that @value{GDBN} does not pretend that inlined
11438 function calls are the same as normal calls:
11442 Setting breakpoints at the call site of an inlined function may not
11443 work, because the call site does not contain any code. @value{GDBN}
11444 may incorrectly move the breakpoint to the next line of the enclosing
11445 function, after the call. This limitation will be removed in a future
11446 version of @value{GDBN}; until then, set a breakpoint on an earlier line
11447 or inside the inlined function instead.
11450 @value{GDBN} cannot locate the return value of inlined calls after
11451 using the @code{finish} command. This is a limitation of compiler-generated
11452 debugging information; after @code{finish}, you can step to the next line
11453 and print a variable where your program stored the return value.
11457 @node Tail Call Frames
11458 @section Tail Call Frames
11459 @cindex tail call frames, debugging
11461 Function @code{B} can call function @code{C} in its very last statement. In
11462 unoptimized compilation the call of @code{C} is immediately followed by return
11463 instruction at the end of @code{B} code. Optimizing compiler may replace the
11464 call and return in function @code{B} into one jump to function @code{C}
11465 instead. Such use of a jump instruction is called @dfn{tail call}.
11467 During execution of function @code{C}, there will be no indication in the
11468 function call stack frames that it was tail-called from @code{B}. If function
11469 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
11470 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
11471 some cases @value{GDBN} can determine that @code{C} was tail-called from
11472 @code{B}, and it will then create fictitious call frame for that, with the
11473 return address set up as if @code{B} called @code{C} normally.
11475 This functionality is currently supported only by DWARF 2 debugging format and
11476 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
11477 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11480 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
11481 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
11485 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
11487 Stack level 1, frame at 0x7fffffffda30:
11488 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
11489 tail call frame, caller of frame at 0x7fffffffda30
11490 source language c++.
11491 Arglist at unknown address.
11492 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
11495 The detection of all the possible code path executions can find them ambiguous.
11496 There is no execution history stored (possible @ref{Reverse Execution} is never
11497 used for this purpose) and the last known caller could have reached the known
11498 callee by multiple different jump sequences. In such case @value{GDBN} still
11499 tries to show at least all the unambiguous top tail callers and all the
11500 unambiguous bottom tail calees, if any.
11503 @anchor{set debug entry-values}
11504 @item set debug entry-values
11505 @kindex set debug entry-values
11506 When set to on, enables printing of analysis messages for both frame argument
11507 values at function entry and tail calls. It will show all the possible valid
11508 tail calls code paths it has considered. It will also print the intersection
11509 of them with the final unambiguous (possibly partial or even empty) code path
11512 @item show debug entry-values
11513 @kindex show debug entry-values
11514 Show the current state of analysis messages printing for both frame argument
11515 values at function entry and tail calls.
11518 The analysis messages for tail calls can for example show why the virtual tail
11519 call frame for function @code{c} has not been recognized (due to the indirect
11520 reference by variable @code{x}):
11523 static void __attribute__((noinline, noclone)) c (void);
11524 void (*x) (void) = c;
11525 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11526 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
11527 int main (void) @{ x (); return 0; @}
11529 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
11530 DW_TAG_GNU_call_site 0x40039a in main
11532 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11535 #1 0x000000000040039a in main () at t.c:5
11538 Another possibility is an ambiguous virtual tail call frames resolution:
11542 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
11543 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
11544 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
11545 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
11546 static void __attribute__((noinline, noclone)) b (void)
11547 @{ if (i) c (); else e (); @}
11548 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
11549 int main (void) @{ a (); return 0; @}
11551 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
11552 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
11553 tailcall: reduced: 0x4004d2(a) |
11556 #1 0x00000000004004d2 in a () at t.c:8
11557 #2 0x0000000000400395 in main () at t.c:9
11560 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
11561 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
11563 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
11564 @ifset HAVE_MAKEINFO_CLICK
11565 @set ARROW @click{}
11566 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
11567 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
11569 @ifclear HAVE_MAKEINFO_CLICK
11571 @set CALLSEQ1B @value{CALLSEQ1A}
11572 @set CALLSEQ2B @value{CALLSEQ2A}
11575 Frames #0 and #2 are real, #1 is a virtual tail call frame.
11576 The code can have possible execution paths @value{CALLSEQ1B} or
11577 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
11579 @code{initial:} state shows some random possible calling sequence @value{GDBN}
11580 has found. It then finds another possible calling sequcen - that one is
11581 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
11582 printed as the @code{reduced:} calling sequence. That one could have many
11583 futher @code{compare:} and @code{reduced:} statements as long as there remain
11584 any non-ambiguous sequence entries.
11586 For the frame of function @code{b} in both cases there are different possible
11587 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
11588 also ambigous. The only non-ambiguous frame is the one for function @code{a},
11589 therefore this one is displayed to the user while the ambiguous frames are
11592 There can be also reasons why printing of frame argument values at function
11597 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
11598 static void __attribute__((noinline, noclone)) a (int i);
11599 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
11600 static void __attribute__((noinline, noclone)) a (int i)
11601 @{ if (i) b (i - 1); else c (0); @}
11602 int main (void) @{ a (5); return 0; @}
11605 #0 c (i=i@@entry=0) at t.c:2
11606 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
11607 function "a" at 0x400420 can call itself via tail calls
11608 i=<optimized out>) at t.c:6
11609 #2 0x000000000040036e in main () at t.c:7
11612 @value{GDBN} cannot find out from the inferior state if and how many times did
11613 function @code{a} call itself (via function @code{b}) as these calls would be
11614 tail calls. Such tail calls would modify thue @code{i} variable, therefore
11615 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
11616 prints @code{<optimized out>} instead.
11619 @chapter C Preprocessor Macros
11621 Some languages, such as C and C@t{++}, provide a way to define and invoke
11622 ``preprocessor macros'' which expand into strings of tokens.
11623 @value{GDBN} can evaluate expressions containing macro invocations, show
11624 the result of macro expansion, and show a macro's definition, including
11625 where it was defined.
11627 You may need to compile your program specially to provide @value{GDBN}
11628 with information about preprocessor macros. Most compilers do not
11629 include macros in their debugging information, even when you compile
11630 with the @option{-g} flag. @xref{Compilation}.
11632 A program may define a macro at one point, remove that definition later,
11633 and then provide a different definition after that. Thus, at different
11634 points in the program, a macro may have different definitions, or have
11635 no definition at all. If there is a current stack frame, @value{GDBN}
11636 uses the macros in scope at that frame's source code line. Otherwise,
11637 @value{GDBN} uses the macros in scope at the current listing location;
11640 Whenever @value{GDBN} evaluates an expression, it always expands any
11641 macro invocations present in the expression. @value{GDBN} also provides
11642 the following commands for working with macros explicitly.
11646 @kindex macro expand
11647 @cindex macro expansion, showing the results of preprocessor
11648 @cindex preprocessor macro expansion, showing the results of
11649 @cindex expanding preprocessor macros
11650 @item macro expand @var{expression}
11651 @itemx macro exp @var{expression}
11652 Show the results of expanding all preprocessor macro invocations in
11653 @var{expression}. Since @value{GDBN} simply expands macros, but does
11654 not parse the result, @var{expression} need not be a valid expression;
11655 it can be any string of tokens.
11658 @item macro expand-once @var{expression}
11659 @itemx macro exp1 @var{expression}
11660 @cindex expand macro once
11661 @i{(This command is not yet implemented.)} Show the results of
11662 expanding those preprocessor macro invocations that appear explicitly in
11663 @var{expression}. Macro invocations appearing in that expansion are
11664 left unchanged. This command allows you to see the effect of a
11665 particular macro more clearly, without being confused by further
11666 expansions. Since @value{GDBN} simply expands macros, but does not
11667 parse the result, @var{expression} need not be a valid expression; it
11668 can be any string of tokens.
11671 @cindex macro definition, showing
11672 @cindex definition of a macro, showing
11673 @cindex macros, from debug info
11674 @item info macro [-a|-all] [--] @var{macro}
11675 Show the current definition or all definitions of the named @var{macro},
11676 and describe the source location or compiler command-line where that
11677 definition was established. The optional double dash is to signify the end of
11678 argument processing and the beginning of @var{macro} for non C-like macros where
11679 the macro may begin with a hyphen.
11681 @kindex info macros
11682 @item info macros @var{linespec}
11683 Show all macro definitions that are in effect at the location specified
11684 by @var{linespec}, and describe the source location or compiler
11685 command-line where those definitions were established.
11687 @kindex macro define
11688 @cindex user-defined macros
11689 @cindex defining macros interactively
11690 @cindex macros, user-defined
11691 @item macro define @var{macro} @var{replacement-list}
11692 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
11693 Introduce a definition for a preprocessor macro named @var{macro},
11694 invocations of which are replaced by the tokens given in
11695 @var{replacement-list}. The first form of this command defines an
11696 ``object-like'' macro, which takes no arguments; the second form
11697 defines a ``function-like'' macro, which takes the arguments given in
11700 A definition introduced by this command is in scope in every
11701 expression evaluated in @value{GDBN}, until it is removed with the
11702 @code{macro undef} command, described below. The definition overrides
11703 all definitions for @var{macro} present in the program being debugged,
11704 as well as any previous user-supplied definition.
11706 @kindex macro undef
11707 @item macro undef @var{macro}
11708 Remove any user-supplied definition for the macro named @var{macro}.
11709 This command only affects definitions provided with the @code{macro
11710 define} command, described above; it cannot remove definitions present
11711 in the program being debugged.
11715 List all the macros defined using the @code{macro define} command.
11718 @cindex macros, example of debugging with
11719 Here is a transcript showing the above commands in action. First, we
11720 show our source files:
11725 #include "sample.h"
11728 #define ADD(x) (M + x)
11733 printf ("Hello, world!\n");
11735 printf ("We're so creative.\n");
11737 printf ("Goodbye, world!\n");
11744 Now, we compile the program using the @sc{gnu} C compiler,
11745 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
11746 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
11747 and @option{-gdwarf-4}; we recommend always choosing the most recent
11748 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
11749 includes information about preprocessor macros in the debugging
11753 $ gcc -gdwarf-2 -g3 sample.c -o sample
11757 Now, we start @value{GDBN} on our sample program:
11761 GNU gdb 2002-05-06-cvs
11762 Copyright 2002 Free Software Foundation, Inc.
11763 GDB is free software, @dots{}
11767 We can expand macros and examine their definitions, even when the
11768 program is not running. @value{GDBN} uses the current listing position
11769 to decide which macro definitions are in scope:
11772 (@value{GDBP}) list main
11775 5 #define ADD(x) (M + x)
11780 10 printf ("Hello, world!\n");
11782 12 printf ("We're so creative.\n");
11783 (@value{GDBP}) info macro ADD
11784 Defined at /home/jimb/gdb/macros/play/sample.c:5
11785 #define ADD(x) (M + x)
11786 (@value{GDBP}) info macro Q
11787 Defined at /home/jimb/gdb/macros/play/sample.h:1
11788 included at /home/jimb/gdb/macros/play/sample.c:2
11790 (@value{GDBP}) macro expand ADD(1)
11791 expands to: (42 + 1)
11792 (@value{GDBP}) macro expand-once ADD(1)
11793 expands to: once (M + 1)
11797 In the example above, note that @code{macro expand-once} expands only
11798 the macro invocation explicit in the original text --- the invocation of
11799 @code{ADD} --- but does not expand the invocation of the macro @code{M},
11800 which was introduced by @code{ADD}.
11802 Once the program is running, @value{GDBN} uses the macro definitions in
11803 force at the source line of the current stack frame:
11806 (@value{GDBP}) break main
11807 Breakpoint 1 at 0x8048370: file sample.c, line 10.
11809 Starting program: /home/jimb/gdb/macros/play/sample
11811 Breakpoint 1, main () at sample.c:10
11812 10 printf ("Hello, world!\n");
11816 At line 10, the definition of the macro @code{N} at line 9 is in force:
11819 (@value{GDBP}) info macro N
11820 Defined at /home/jimb/gdb/macros/play/sample.c:9
11822 (@value{GDBP}) macro expand N Q M
11823 expands to: 28 < 42
11824 (@value{GDBP}) print N Q M
11829 As we step over directives that remove @code{N}'s definition, and then
11830 give it a new definition, @value{GDBN} finds the definition (or lack
11831 thereof) in force at each point:
11834 (@value{GDBP}) next
11836 12 printf ("We're so creative.\n");
11837 (@value{GDBP}) info macro N
11838 The symbol `N' has no definition as a C/C++ preprocessor macro
11839 at /home/jimb/gdb/macros/play/sample.c:12
11840 (@value{GDBP}) next
11842 14 printf ("Goodbye, world!\n");
11843 (@value{GDBP}) info macro N
11844 Defined at /home/jimb/gdb/macros/play/sample.c:13
11846 (@value{GDBP}) macro expand N Q M
11847 expands to: 1729 < 42
11848 (@value{GDBP}) print N Q M
11853 In addition to source files, macros can be defined on the compilation command
11854 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
11855 such a way, @value{GDBN} displays the location of their definition as line zero
11856 of the source file submitted to the compiler.
11859 (@value{GDBP}) info macro __STDC__
11860 Defined at /home/jimb/gdb/macros/play/sample.c:0
11867 @chapter Tracepoints
11868 @c This chapter is based on the documentation written by Michael
11869 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
11871 @cindex tracepoints
11872 In some applications, it is not feasible for the debugger to interrupt
11873 the program's execution long enough for the developer to learn
11874 anything helpful about its behavior. If the program's correctness
11875 depends on its real-time behavior, delays introduced by a debugger
11876 might cause the program to change its behavior drastically, or perhaps
11877 fail, even when the code itself is correct. It is useful to be able
11878 to observe the program's behavior without interrupting it.
11880 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
11881 specify locations in the program, called @dfn{tracepoints}, and
11882 arbitrary expressions to evaluate when those tracepoints are reached.
11883 Later, using the @code{tfind} command, you can examine the values
11884 those expressions had when the program hit the tracepoints. The
11885 expressions may also denote objects in memory---structures or arrays,
11886 for example---whose values @value{GDBN} should record; while visiting
11887 a particular tracepoint, you may inspect those objects as if they were
11888 in memory at that moment. However, because @value{GDBN} records these
11889 values without interacting with you, it can do so quickly and
11890 unobtrusively, hopefully not disturbing the program's behavior.
11892 The tracepoint facility is currently available only for remote
11893 targets. @xref{Targets}. In addition, your remote target must know
11894 how to collect trace data. This functionality is implemented in the
11895 remote stub; however, none of the stubs distributed with @value{GDBN}
11896 support tracepoints as of this writing. The format of the remote
11897 packets used to implement tracepoints are described in @ref{Tracepoint
11900 It is also possible to get trace data from a file, in a manner reminiscent
11901 of corefiles; you specify the filename, and use @code{tfind} to search
11902 through the file. @xref{Trace Files}, for more details.
11904 This chapter describes the tracepoint commands and features.
11907 * Set Tracepoints::
11908 * Analyze Collected Data::
11909 * Tracepoint Variables::
11913 @node Set Tracepoints
11914 @section Commands to Set Tracepoints
11916 Before running such a @dfn{trace experiment}, an arbitrary number of
11917 tracepoints can be set. A tracepoint is actually a special type of
11918 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
11919 standard breakpoint commands. For instance, as with breakpoints,
11920 tracepoint numbers are successive integers starting from one, and many
11921 of the commands associated with tracepoints take the tracepoint number
11922 as their argument, to identify which tracepoint to work on.
11924 For each tracepoint, you can specify, in advance, some arbitrary set
11925 of data that you want the target to collect in the trace buffer when
11926 it hits that tracepoint. The collected data can include registers,
11927 local variables, or global data. Later, you can use @value{GDBN}
11928 commands to examine the values these data had at the time the
11929 tracepoint was hit.
11931 Tracepoints do not support every breakpoint feature. Ignore counts on
11932 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
11933 commands when they are hit. Tracepoints may not be thread-specific
11936 @cindex fast tracepoints
11937 Some targets may support @dfn{fast tracepoints}, which are inserted in
11938 a different way (such as with a jump instead of a trap), that is
11939 faster but possibly restricted in where they may be installed.
11941 @cindex static tracepoints
11942 @cindex markers, static tracepoints
11943 @cindex probing markers, static tracepoints
11944 Regular and fast tracepoints are dynamic tracing facilities, meaning
11945 that they can be used to insert tracepoints at (almost) any location
11946 in the target. Some targets may also support controlling @dfn{static
11947 tracepoints} from @value{GDBN}. With static tracing, a set of
11948 instrumentation points, also known as @dfn{markers}, are embedded in
11949 the target program, and can be activated or deactivated by name or
11950 address. These are usually placed at locations which facilitate
11951 investigating what the target is actually doing. @value{GDBN}'s
11952 support for static tracing includes being able to list instrumentation
11953 points, and attach them with @value{GDBN} defined high level
11954 tracepoints that expose the whole range of convenience of
11955 @value{GDBN}'s tracepoints support. Namely, support for collecting
11956 registers values and values of global or local (to the instrumentation
11957 point) variables; tracepoint conditions and trace state variables.
11958 The act of installing a @value{GDBN} static tracepoint on an
11959 instrumentation point, or marker, is referred to as @dfn{probing} a
11960 static tracepoint marker.
11962 @code{gdbserver} supports tracepoints on some target systems.
11963 @xref{Server,,Tracepoints support in @code{gdbserver}}.
11965 This section describes commands to set tracepoints and associated
11966 conditions and actions.
11969 * Create and Delete Tracepoints::
11970 * Enable and Disable Tracepoints::
11971 * Tracepoint Passcounts::
11972 * Tracepoint Conditions::
11973 * Trace State Variables::
11974 * Tracepoint Actions::
11975 * Listing Tracepoints::
11976 * Listing Static Tracepoint Markers::
11977 * Starting and Stopping Trace Experiments::
11978 * Tracepoint Restrictions::
11981 @node Create and Delete Tracepoints
11982 @subsection Create and Delete Tracepoints
11985 @cindex set tracepoint
11987 @item trace @var{location}
11988 The @code{trace} command is very similar to the @code{break} command.
11989 Its argument @var{location} can be a source line, a function name, or
11990 an address in the target program. @xref{Specify Location}. The
11991 @code{trace} command defines a tracepoint, which is a point in the
11992 target program where the debugger will briefly stop, collect some
11993 data, and then allow the program to continue. Setting a tracepoint or
11994 changing its actions takes effect immediately if the remote stub
11995 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
11997 If remote stub doesn't support the @samp{InstallInTrace} feature, all
11998 these changes don't take effect until the next @code{tstart}
11999 command, and once a trace experiment is running, further changes will
12000 not have any effect until the next trace experiment starts. In addition,
12001 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
12002 address is not yet resolved. (This is similar to pending breakpoints.)
12003 Pending tracepoints are not downloaded to the target and not installed
12004 until they are resolved. The resolution of pending tracepoints requires
12005 @value{GDBN} support---when debugging with the remote target, and
12006 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
12007 tracing}), pending tracepoints can not be resolved (and downloaded to
12008 the remote stub) while @value{GDBN} is disconnected.
12010 Here are some examples of using the @code{trace} command:
12013 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
12015 (@value{GDBP}) @b{trace +2} // 2 lines forward
12017 (@value{GDBP}) @b{trace my_function} // first source line of function
12019 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
12021 (@value{GDBP}) @b{trace *0x2117c4} // an address
12025 You can abbreviate @code{trace} as @code{tr}.
12027 @item trace @var{location} if @var{cond}
12028 Set a tracepoint with condition @var{cond}; evaluate the expression
12029 @var{cond} each time the tracepoint is reached, and collect data only
12030 if the value is nonzero---that is, if @var{cond} evaluates as true.
12031 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
12032 information on tracepoint conditions.
12034 @item ftrace @var{location} [ if @var{cond} ]
12035 @cindex set fast tracepoint
12036 @cindex fast tracepoints, setting
12038 The @code{ftrace} command sets a fast tracepoint. For targets that
12039 support them, fast tracepoints will use a more efficient but possibly
12040 less general technique to trigger data collection, such as a jump
12041 instruction instead of a trap, or some sort of hardware support. It
12042 may not be possible to create a fast tracepoint at the desired
12043 location, in which case the command will exit with an explanatory
12046 @value{GDBN} handles arguments to @code{ftrace} exactly as for
12049 On 32-bit x86-architecture systems, fast tracepoints normally need to
12050 be placed at an instruction that is 5 bytes or longer, but can be
12051 placed at 4-byte instructions if the low 64K of memory of the target
12052 program is available to install trampolines. Some Unix-type systems,
12053 such as @sc{gnu}/Linux, exclude low addresses from the program's
12054 address space; but for instance with the Linux kernel it is possible
12055 to let @value{GDBN} use this area by doing a @command{sysctl} command
12056 to set the @code{mmap_min_addr} kernel parameter, as in
12059 sudo sysctl -w vm.mmap_min_addr=32768
12063 which sets the low address to 32K, which leaves plenty of room for
12064 trampolines. The minimum address should be set to a page boundary.
12066 @item strace @var{location} [ if @var{cond} ]
12067 @cindex set static tracepoint
12068 @cindex static tracepoints, setting
12069 @cindex probe static tracepoint marker
12071 The @code{strace} command sets a static tracepoint. For targets that
12072 support it, setting a static tracepoint probes a static
12073 instrumentation point, or marker, found at @var{location}. It may not
12074 be possible to set a static tracepoint at the desired location, in
12075 which case the command will exit with an explanatory message.
12077 @value{GDBN} handles arguments to @code{strace} exactly as for
12078 @code{trace}, with the addition that the user can also specify
12079 @code{-m @var{marker}} as @var{location}. This probes the marker
12080 identified by the @var{marker} string identifier. This identifier
12081 depends on the static tracepoint backend library your program is
12082 using. You can find all the marker identifiers in the @samp{ID} field
12083 of the @code{info static-tracepoint-markers} command output.
12084 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
12085 Markers}. For example, in the following small program using the UST
12091 trace_mark(ust, bar33, "str %s", "FOOBAZ");
12096 the marker id is composed of joining the first two arguments to the
12097 @code{trace_mark} call with a slash, which translates to:
12100 (@value{GDBP}) info static-tracepoint-markers
12101 Cnt Enb ID Address What
12102 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
12108 so you may probe the marker above with:
12111 (@value{GDBP}) strace -m ust/bar33
12114 Static tracepoints accept an extra collect action --- @code{collect
12115 $_sdata}. This collects arbitrary user data passed in the probe point
12116 call to the tracing library. In the UST example above, you'll see
12117 that the third argument to @code{trace_mark} is a printf-like format
12118 string. The user data is then the result of running that formating
12119 string against the following arguments. Note that @code{info
12120 static-tracepoint-markers} command output lists that format string in
12121 the @samp{Data:} field.
12123 You can inspect this data when analyzing the trace buffer, by printing
12124 the $_sdata variable like any other variable available to
12125 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
12128 @cindex last tracepoint number
12129 @cindex recent tracepoint number
12130 @cindex tracepoint number
12131 The convenience variable @code{$tpnum} records the tracepoint number
12132 of the most recently set tracepoint.
12134 @kindex delete tracepoint
12135 @cindex tracepoint deletion
12136 @item delete tracepoint @r{[}@var{num}@r{]}
12137 Permanently delete one or more tracepoints. With no argument, the
12138 default is to delete all tracepoints. Note that the regular
12139 @code{delete} command can remove tracepoints also.
12144 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
12146 (@value{GDBP}) @b{delete trace} // remove all tracepoints
12150 You can abbreviate this command as @code{del tr}.
12153 @node Enable and Disable Tracepoints
12154 @subsection Enable and Disable Tracepoints
12156 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
12159 @kindex disable tracepoint
12160 @item disable tracepoint @r{[}@var{num}@r{]}
12161 Disable tracepoint @var{num}, or all tracepoints if no argument
12162 @var{num} is given. A disabled tracepoint will have no effect during
12163 a trace experiment, but it is not forgotten. You can re-enable
12164 a disabled tracepoint using the @code{enable tracepoint} command.
12165 If the command is issued during a trace experiment and the debug target
12166 has support for disabling tracepoints during a trace experiment, then the
12167 change will be effective immediately. Otherwise, it will be applied to the
12168 next trace experiment.
12170 @kindex enable tracepoint
12171 @item enable tracepoint @r{[}@var{num}@r{]}
12172 Enable tracepoint @var{num}, or all tracepoints. If this command is
12173 issued during a trace experiment and the debug target supports enabling
12174 tracepoints during a trace experiment, then the enabled tracepoints will
12175 become effective immediately. Otherwise, they will become effective the
12176 next time a trace experiment is run.
12179 @node Tracepoint Passcounts
12180 @subsection Tracepoint Passcounts
12184 @cindex tracepoint pass count
12185 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
12186 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
12187 automatically stop a trace experiment. If a tracepoint's passcount is
12188 @var{n}, then the trace experiment will be automatically stopped on
12189 the @var{n}'th time that tracepoint is hit. If the tracepoint number
12190 @var{num} is not specified, the @code{passcount} command sets the
12191 passcount of the most recently defined tracepoint. If no passcount is
12192 given, the trace experiment will run until stopped explicitly by the
12198 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
12199 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
12201 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
12202 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
12203 (@value{GDBP}) @b{trace foo}
12204 (@value{GDBP}) @b{pass 3}
12205 (@value{GDBP}) @b{trace bar}
12206 (@value{GDBP}) @b{pass 2}
12207 (@value{GDBP}) @b{trace baz}
12208 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
12209 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
12210 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
12211 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
12215 @node Tracepoint Conditions
12216 @subsection Tracepoint Conditions
12217 @cindex conditional tracepoints
12218 @cindex tracepoint conditions
12220 The simplest sort of tracepoint collects data every time your program
12221 reaches a specified place. You can also specify a @dfn{condition} for
12222 a tracepoint. A condition is just a Boolean expression in your
12223 programming language (@pxref{Expressions, ,Expressions}). A
12224 tracepoint with a condition evaluates the expression each time your
12225 program reaches it, and data collection happens only if the condition
12228 Tracepoint conditions can be specified when a tracepoint is set, by
12229 using @samp{if} in the arguments to the @code{trace} command.
12230 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
12231 also be set or changed at any time with the @code{condition} command,
12232 just as with breakpoints.
12234 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
12235 the conditional expression itself. Instead, @value{GDBN} encodes the
12236 expression into an agent expression (@pxref{Agent Expressions})
12237 suitable for execution on the target, independently of @value{GDBN}.
12238 Global variables become raw memory locations, locals become stack
12239 accesses, and so forth.
12241 For instance, suppose you have a function that is usually called
12242 frequently, but should not be called after an error has occurred. You
12243 could use the following tracepoint command to collect data about calls
12244 of that function that happen while the error code is propagating
12245 through the program; an unconditional tracepoint could end up
12246 collecting thousands of useless trace frames that you would have to
12250 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
12253 @node Trace State Variables
12254 @subsection Trace State Variables
12255 @cindex trace state variables
12257 A @dfn{trace state variable} is a special type of variable that is
12258 created and managed by target-side code. The syntax is the same as
12259 that for GDB's convenience variables (a string prefixed with ``$''),
12260 but they are stored on the target. They must be created explicitly,
12261 using a @code{tvariable} command. They are always 64-bit signed
12264 Trace state variables are remembered by @value{GDBN}, and downloaded
12265 to the target along with tracepoint information when the trace
12266 experiment starts. There are no intrinsic limits on the number of
12267 trace state variables, beyond memory limitations of the target.
12269 @cindex convenience variables, and trace state variables
12270 Although trace state variables are managed by the target, you can use
12271 them in print commands and expressions as if they were convenience
12272 variables; @value{GDBN} will get the current value from the target
12273 while the trace experiment is running. Trace state variables share
12274 the same namespace as other ``$'' variables, which means that you
12275 cannot have trace state variables with names like @code{$23} or
12276 @code{$pc}, nor can you have a trace state variable and a convenience
12277 variable with the same name.
12281 @item tvariable $@var{name} [ = @var{expression} ]
12283 The @code{tvariable} command creates a new trace state variable named
12284 @code{$@var{name}}, and optionally gives it an initial value of
12285 @var{expression}. The @var{expression} is evaluated when this command is
12286 entered; the result will be converted to an integer if possible,
12287 otherwise @value{GDBN} will report an error. A subsequent
12288 @code{tvariable} command specifying the same name does not create a
12289 variable, but instead assigns the supplied initial value to the
12290 existing variable of that name, overwriting any previous initial
12291 value. The default initial value is 0.
12293 @item info tvariables
12294 @kindex info tvariables
12295 List all the trace state variables along with their initial values.
12296 Their current values may also be displayed, if the trace experiment is
12299 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
12300 @kindex delete tvariable
12301 Delete the given trace state variables, or all of them if no arguments
12306 @node Tracepoint Actions
12307 @subsection Tracepoint Action Lists
12311 @cindex tracepoint actions
12312 @item actions @r{[}@var{num}@r{]}
12313 This command will prompt for a list of actions to be taken when the
12314 tracepoint is hit. If the tracepoint number @var{num} is not
12315 specified, this command sets the actions for the one that was most
12316 recently defined (so that you can define a tracepoint and then say
12317 @code{actions} without bothering about its number). You specify the
12318 actions themselves on the following lines, one action at a time, and
12319 terminate the actions list with a line containing just @code{end}. So
12320 far, the only defined actions are @code{collect}, @code{teval}, and
12321 @code{while-stepping}.
12323 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
12324 Commands, ,Breakpoint Command Lists}), except that only the defined
12325 actions are allowed; any other @value{GDBN} command is rejected.
12327 @cindex remove actions from a tracepoint
12328 To remove all actions from a tracepoint, type @samp{actions @var{num}}
12329 and follow it immediately with @samp{end}.
12332 (@value{GDBP}) @b{collect @var{data}} // collect some data
12334 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
12336 (@value{GDBP}) @b{end} // signals the end of actions.
12339 In the following example, the action list begins with @code{collect}
12340 commands indicating the things to be collected when the tracepoint is
12341 hit. Then, in order to single-step and collect additional data
12342 following the tracepoint, a @code{while-stepping} command is used,
12343 followed by the list of things to be collected after each step in a
12344 sequence of single steps. The @code{while-stepping} command is
12345 terminated by its own separate @code{end} command. Lastly, the action
12346 list is terminated by an @code{end} command.
12349 (@value{GDBP}) @b{trace foo}
12350 (@value{GDBP}) @b{actions}
12351 Enter actions for tracepoint 1, one per line:
12354 > while-stepping 12
12355 > collect $pc, arr[i]
12360 @kindex collect @r{(tracepoints)}
12361 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
12362 Collect values of the given expressions when the tracepoint is hit.
12363 This command accepts a comma-separated list of any valid expressions.
12364 In addition to global, static, or local variables, the following
12365 special arguments are supported:
12369 Collect all registers.
12372 Collect all function arguments.
12375 Collect all local variables.
12378 Collect the return address. This is helpful if you want to see more
12382 Collects the number of arguments from the static probe at which the
12383 tracepoint is located.
12384 @xref{Static Probe Points}.
12386 @item $_probe_arg@var{n}
12387 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
12388 from the static probe at which the tracepoint is located.
12389 @xref{Static Probe Points}.
12392 @vindex $_sdata@r{, collect}
12393 Collect static tracepoint marker specific data. Only available for
12394 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
12395 Lists}. On the UST static tracepoints library backend, an
12396 instrumentation point resembles a @code{printf} function call. The
12397 tracing library is able to collect user specified data formatted to a
12398 character string using the format provided by the programmer that
12399 instrumented the program. Other backends have similar mechanisms.
12400 Here's an example of a UST marker call:
12403 const char master_name[] = "$your_name";
12404 trace_mark(channel1, marker1, "hello %s", master_name)
12407 In this case, collecting @code{$_sdata} collects the string
12408 @samp{hello $yourname}. When analyzing the trace buffer, you can
12409 inspect @samp{$_sdata} like any other variable available to
12413 You can give several consecutive @code{collect} commands, each one
12414 with a single argument, or one @code{collect} command with several
12415 arguments separated by commas; the effect is the same.
12417 The optional @var{mods} changes the usual handling of the arguments.
12418 @code{s} requests that pointers to chars be handled as strings, in
12419 particular collecting the contents of the memory being pointed at, up
12420 to the first zero. The upper bound is by default the value of the
12421 @code{print elements} variable; if @code{s} is followed by a decimal
12422 number, that is the upper bound instead. So for instance
12423 @samp{collect/s25 mystr} collects as many as 25 characters at
12426 The command @code{info scope} (@pxref{Symbols, info scope}) is
12427 particularly useful for figuring out what data to collect.
12429 @kindex teval @r{(tracepoints)}
12430 @item teval @var{expr1}, @var{expr2}, @dots{}
12431 Evaluate the given expressions when the tracepoint is hit. This
12432 command accepts a comma-separated list of expressions. The results
12433 are discarded, so this is mainly useful for assigning values to trace
12434 state variables (@pxref{Trace State Variables}) without adding those
12435 values to the trace buffer, as would be the case if the @code{collect}
12438 @kindex while-stepping @r{(tracepoints)}
12439 @item while-stepping @var{n}
12440 Perform @var{n} single-step instruction traces after the tracepoint,
12441 collecting new data after each step. The @code{while-stepping}
12442 command is followed by the list of what to collect while stepping
12443 (followed by its own @code{end} command):
12446 > while-stepping 12
12447 > collect $regs, myglobal
12453 Note that @code{$pc} is not automatically collected by
12454 @code{while-stepping}; you need to explicitly collect that register if
12455 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
12458 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
12459 @kindex set default-collect
12460 @cindex default collection action
12461 This variable is a list of expressions to collect at each tracepoint
12462 hit. It is effectively an additional @code{collect} action prepended
12463 to every tracepoint action list. The expressions are parsed
12464 individually for each tracepoint, so for instance a variable named
12465 @code{xyz} may be interpreted as a global for one tracepoint, and a
12466 local for another, as appropriate to the tracepoint's location.
12468 @item show default-collect
12469 @kindex show default-collect
12470 Show the list of expressions that are collected by default at each
12475 @node Listing Tracepoints
12476 @subsection Listing Tracepoints
12479 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
12480 @kindex info tp @r{[}@var{n}@dots{}@r{]}
12481 @cindex information about tracepoints
12482 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
12483 Display information about the tracepoint @var{num}. If you don't
12484 specify a tracepoint number, displays information about all the
12485 tracepoints defined so far. The format is similar to that used for
12486 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
12487 command, simply restricting itself to tracepoints.
12489 A tracepoint's listing may include additional information specific to
12494 its passcount as given by the @code{passcount @var{n}} command
12497 the state about installed on target of each location
12501 (@value{GDBP}) @b{info trace}
12502 Num Type Disp Enb Address What
12503 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
12505 collect globfoo, $regs
12510 2 tracepoint keep y <MULTIPLE>
12512 2.1 y 0x0804859c in func4 at change-loc.h:35
12513 installed on target
12514 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
12515 installed on target
12516 2.3 y <PENDING> set_tracepoint
12517 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
12518 not installed on target
12523 This command can be abbreviated @code{info tp}.
12526 @node Listing Static Tracepoint Markers
12527 @subsection Listing Static Tracepoint Markers
12530 @kindex info static-tracepoint-markers
12531 @cindex information about static tracepoint markers
12532 @item info static-tracepoint-markers
12533 Display information about all static tracepoint markers defined in the
12536 For each marker, the following columns are printed:
12540 An incrementing counter, output to help readability. This is not a
12543 The marker ID, as reported by the target.
12544 @item Enabled or Disabled
12545 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
12546 that are not enabled.
12548 Where the marker is in your program, as a memory address.
12550 Where the marker is in the source for your program, as a file and line
12551 number. If the debug information included in the program does not
12552 allow @value{GDBN} to locate the source of the marker, this column
12553 will be left blank.
12557 In addition, the following information may be printed for each marker:
12561 User data passed to the tracing library by the marker call. In the
12562 UST backend, this is the format string passed as argument to the
12564 @item Static tracepoints probing the marker
12565 The list of static tracepoints attached to the marker.
12569 (@value{GDBP}) info static-tracepoint-markers
12570 Cnt ID Enb Address What
12571 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
12572 Data: number1 %d number2 %d
12573 Probed by static tracepoints: #2
12574 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
12580 @node Starting and Stopping Trace Experiments
12581 @subsection Starting and Stopping Trace Experiments
12584 @kindex tstart [ @var{notes} ]
12585 @cindex start a new trace experiment
12586 @cindex collected data discarded
12588 This command starts the trace experiment, and begins collecting data.
12589 It has the side effect of discarding all the data collected in the
12590 trace buffer during the previous trace experiment. If any arguments
12591 are supplied, they are taken as a note and stored with the trace
12592 experiment's state. The notes may be arbitrary text, and are
12593 especially useful with disconnected tracing in a multi-user context;
12594 the notes can explain what the trace is doing, supply user contact
12595 information, and so forth.
12597 @kindex tstop [ @var{notes} ]
12598 @cindex stop a running trace experiment
12600 This command stops the trace experiment. If any arguments are
12601 supplied, they are recorded with the experiment as a note. This is
12602 useful if you are stopping a trace started by someone else, for
12603 instance if the trace is interfering with the system's behavior and
12604 needs to be stopped quickly.
12606 @strong{Note}: a trace experiment and data collection may stop
12607 automatically if any tracepoint's passcount is reached
12608 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
12611 @cindex status of trace data collection
12612 @cindex trace experiment, status of
12614 This command displays the status of the current trace data
12618 Here is an example of the commands we described so far:
12621 (@value{GDBP}) @b{trace gdb_c_test}
12622 (@value{GDBP}) @b{actions}
12623 Enter actions for tracepoint #1, one per line.
12624 > collect $regs,$locals,$args
12625 > while-stepping 11
12629 (@value{GDBP}) @b{tstart}
12630 [time passes @dots{}]
12631 (@value{GDBP}) @b{tstop}
12634 @anchor{disconnected tracing}
12635 @cindex disconnected tracing
12636 You can choose to continue running the trace experiment even if
12637 @value{GDBN} disconnects from the target, voluntarily or
12638 involuntarily. For commands such as @code{detach}, the debugger will
12639 ask what you want to do with the trace. But for unexpected
12640 terminations (@value{GDBN} crash, network outage), it would be
12641 unfortunate to lose hard-won trace data, so the variable
12642 @code{disconnected-tracing} lets you decide whether the trace should
12643 continue running without @value{GDBN}.
12646 @item set disconnected-tracing on
12647 @itemx set disconnected-tracing off
12648 @kindex set disconnected-tracing
12649 Choose whether a tracing run should continue to run if @value{GDBN}
12650 has disconnected from the target. Note that @code{detach} or
12651 @code{quit} will ask you directly what to do about a running trace no
12652 matter what this variable's setting, so the variable is mainly useful
12653 for handling unexpected situations, such as loss of the network.
12655 @item show disconnected-tracing
12656 @kindex show disconnected-tracing
12657 Show the current choice for disconnected tracing.
12661 When you reconnect to the target, the trace experiment may or may not
12662 still be running; it might have filled the trace buffer in the
12663 meantime, or stopped for one of the other reasons. If it is running,
12664 it will continue after reconnection.
12666 Upon reconnection, the target will upload information about the
12667 tracepoints in effect. @value{GDBN} will then compare that
12668 information to the set of tracepoints currently defined, and attempt
12669 to match them up, allowing for the possibility that the numbers may
12670 have changed due to creation and deletion in the meantime. If one of
12671 the target's tracepoints does not match any in @value{GDBN}, the
12672 debugger will create a new tracepoint, so that you have a number with
12673 which to specify that tracepoint. This matching-up process is
12674 necessarily heuristic, and it may result in useless tracepoints being
12675 created; you may simply delete them if they are of no use.
12677 @cindex circular trace buffer
12678 If your target agent supports a @dfn{circular trace buffer}, then you
12679 can run a trace experiment indefinitely without filling the trace
12680 buffer; when space runs out, the agent deletes already-collected trace
12681 frames, oldest first, until there is enough room to continue
12682 collecting. This is especially useful if your tracepoints are being
12683 hit too often, and your trace gets terminated prematurely because the
12684 buffer is full. To ask for a circular trace buffer, simply set
12685 @samp{circular-trace-buffer} to on. You can set this at any time,
12686 including during tracing; if the agent can do it, it will change
12687 buffer handling on the fly, otherwise it will not take effect until
12691 @item set circular-trace-buffer on
12692 @itemx set circular-trace-buffer off
12693 @kindex set circular-trace-buffer
12694 Choose whether a tracing run should use a linear or circular buffer
12695 for trace data. A linear buffer will not lose any trace data, but may
12696 fill up prematurely, while a circular buffer will discard old trace
12697 data, but it will have always room for the latest tracepoint hits.
12699 @item show circular-trace-buffer
12700 @kindex show circular-trace-buffer
12701 Show the current choice for the trace buffer. Note that this may not
12702 match the agent's current buffer handling, nor is it guaranteed to
12703 match the setting that might have been in effect during a past run,
12704 for instance if you are looking at frames from a trace file.
12709 @item set trace-buffer-size @var{n}
12710 @itemx set trace-buffer-size unlimited
12711 @kindex set trace-buffer-size
12712 Request that the target use a trace buffer of @var{n} bytes. Not all
12713 targets will honor the request; they may have a compiled-in size for
12714 the trace buffer, or some other limitation. Set to a value of
12715 @code{unlimited} or @code{-1} to let the target use whatever size it
12716 likes. This is also the default.
12718 @item show trace-buffer-size
12719 @kindex show trace-buffer-size
12720 Show the current requested size for the trace buffer. Note that this
12721 will only match the actual size if the target supports size-setting,
12722 and was able to handle the requested size. For instance, if the
12723 target can only change buffer size between runs, this variable will
12724 not reflect the change until the next run starts. Use @code{tstatus}
12725 to get a report of the actual buffer size.
12729 @item set trace-user @var{text}
12730 @kindex set trace-user
12732 @item show trace-user
12733 @kindex show trace-user
12735 @item set trace-notes @var{text}
12736 @kindex set trace-notes
12737 Set the trace run's notes.
12739 @item show trace-notes
12740 @kindex show trace-notes
12741 Show the trace run's notes.
12743 @item set trace-stop-notes @var{text}
12744 @kindex set trace-stop-notes
12745 Set the trace run's stop notes. The handling of the note is as for
12746 @code{tstop} arguments; the set command is convenient way to fix a
12747 stop note that is mistaken or incomplete.
12749 @item show trace-stop-notes
12750 @kindex show trace-stop-notes
12751 Show the trace run's stop notes.
12755 @node Tracepoint Restrictions
12756 @subsection Tracepoint Restrictions
12758 @cindex tracepoint restrictions
12759 There are a number of restrictions on the use of tracepoints. As
12760 described above, tracepoint data gathering occurs on the target
12761 without interaction from @value{GDBN}. Thus the full capabilities of
12762 the debugger are not available during data gathering, and then at data
12763 examination time, you will be limited by only having what was
12764 collected. The following items describe some common problems, but it
12765 is not exhaustive, and you may run into additional difficulties not
12771 Tracepoint expressions are intended to gather objects (lvalues). Thus
12772 the full flexibility of GDB's expression evaluator is not available.
12773 You cannot call functions, cast objects to aggregate types, access
12774 convenience variables or modify values (except by assignment to trace
12775 state variables). Some language features may implicitly call
12776 functions (for instance Objective-C fields with accessors), and therefore
12777 cannot be collected either.
12780 Collection of local variables, either individually or in bulk with
12781 @code{$locals} or @code{$args}, during @code{while-stepping} may
12782 behave erratically. The stepping action may enter a new scope (for
12783 instance by stepping into a function), or the location of the variable
12784 may change (for instance it is loaded into a register). The
12785 tracepoint data recorded uses the location information for the
12786 variables that is correct for the tracepoint location. When the
12787 tracepoint is created, it is not possible, in general, to determine
12788 where the steps of a @code{while-stepping} sequence will advance the
12789 program---particularly if a conditional branch is stepped.
12792 Collection of an incompletely-initialized or partially-destroyed object
12793 may result in something that @value{GDBN} cannot display, or displays
12794 in a misleading way.
12797 When @value{GDBN} displays a pointer to character it automatically
12798 dereferences the pointer to also display characters of the string
12799 being pointed to. However, collecting the pointer during tracing does
12800 not automatically collect the string. You need to explicitly
12801 dereference the pointer and provide size information if you want to
12802 collect not only the pointer, but the memory pointed to. For example,
12803 @code{*ptr@@50} can be used to collect the 50 element array pointed to
12807 It is not possible to collect a complete stack backtrace at a
12808 tracepoint. Instead, you may collect the registers and a few hundred
12809 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
12810 (adjust to use the name of the actual stack pointer register on your
12811 target architecture, and the amount of stack you wish to capture).
12812 Then the @code{backtrace} command will show a partial backtrace when
12813 using a trace frame. The number of stack frames that can be examined
12814 depends on the sizes of the frames in the collected stack. Note that
12815 if you ask for a block so large that it goes past the bottom of the
12816 stack, the target agent may report an error trying to read from an
12820 If you do not collect registers at a tracepoint, @value{GDBN} can
12821 infer that the value of @code{$pc} must be the same as the address of
12822 the tracepoint and use that when you are looking at a trace frame
12823 for that tracepoint. However, this cannot work if the tracepoint has
12824 multiple locations (for instance if it was set in a function that was
12825 inlined), or if it has a @code{while-stepping} loop. In those cases
12826 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
12831 @node Analyze Collected Data
12832 @section Using the Collected Data
12834 After the tracepoint experiment ends, you use @value{GDBN} commands
12835 for examining the trace data. The basic idea is that each tracepoint
12836 collects a trace @dfn{snapshot} every time it is hit and another
12837 snapshot every time it single-steps. All these snapshots are
12838 consecutively numbered from zero and go into a buffer, and you can
12839 examine them later. The way you examine them is to @dfn{focus} on a
12840 specific trace snapshot. When the remote stub is focused on a trace
12841 snapshot, it will respond to all @value{GDBN} requests for memory and
12842 registers by reading from the buffer which belongs to that snapshot,
12843 rather than from @emph{real} memory or registers of the program being
12844 debugged. This means that @strong{all} @value{GDBN} commands
12845 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
12846 behave as if we were currently debugging the program state as it was
12847 when the tracepoint occurred. Any requests for data that are not in
12848 the buffer will fail.
12851 * tfind:: How to select a trace snapshot
12852 * tdump:: How to display all data for a snapshot
12853 * save tracepoints:: How to save tracepoints for a future run
12857 @subsection @code{tfind @var{n}}
12860 @cindex select trace snapshot
12861 @cindex find trace snapshot
12862 The basic command for selecting a trace snapshot from the buffer is
12863 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
12864 counting from zero. If no argument @var{n} is given, the next
12865 snapshot is selected.
12867 Here are the various forms of using the @code{tfind} command.
12871 Find the first snapshot in the buffer. This is a synonym for
12872 @code{tfind 0} (since 0 is the number of the first snapshot).
12875 Stop debugging trace snapshots, resume @emph{live} debugging.
12878 Same as @samp{tfind none}.
12881 No argument means find the next trace snapshot.
12884 Find the previous trace snapshot before the current one. This permits
12885 retracing earlier steps.
12887 @item tfind tracepoint @var{num}
12888 Find the next snapshot associated with tracepoint @var{num}. Search
12889 proceeds forward from the last examined trace snapshot. If no
12890 argument @var{num} is given, it means find the next snapshot collected
12891 for the same tracepoint as the current snapshot.
12893 @item tfind pc @var{addr}
12894 Find the next snapshot associated with the value @var{addr} of the
12895 program counter. Search proceeds forward from the last examined trace
12896 snapshot. If no argument @var{addr} is given, it means find the next
12897 snapshot with the same value of PC as the current snapshot.
12899 @item tfind outside @var{addr1}, @var{addr2}
12900 Find the next snapshot whose PC is outside the given range of
12901 addresses (exclusive).
12903 @item tfind range @var{addr1}, @var{addr2}
12904 Find the next snapshot whose PC is between @var{addr1} and
12905 @var{addr2} (inclusive).
12907 @item tfind line @r{[}@var{file}:@r{]}@var{n}
12908 Find the next snapshot associated with the source line @var{n}. If
12909 the optional argument @var{file} is given, refer to line @var{n} in
12910 that source file. Search proceeds forward from the last examined
12911 trace snapshot. If no argument @var{n} is given, it means find the
12912 next line other than the one currently being examined; thus saying
12913 @code{tfind line} repeatedly can appear to have the same effect as
12914 stepping from line to line in a @emph{live} debugging session.
12917 The default arguments for the @code{tfind} commands are specifically
12918 designed to make it easy to scan through the trace buffer. For
12919 instance, @code{tfind} with no argument selects the next trace
12920 snapshot, and @code{tfind -} with no argument selects the previous
12921 trace snapshot. So, by giving one @code{tfind} command, and then
12922 simply hitting @key{RET} repeatedly you can examine all the trace
12923 snapshots in order. Or, by saying @code{tfind -} and then hitting
12924 @key{RET} repeatedly you can examine the snapshots in reverse order.
12925 The @code{tfind line} command with no argument selects the snapshot
12926 for the next source line executed. The @code{tfind pc} command with
12927 no argument selects the next snapshot with the same program counter
12928 (PC) as the current frame. The @code{tfind tracepoint} command with
12929 no argument selects the next trace snapshot collected by the same
12930 tracepoint as the current one.
12932 In addition to letting you scan through the trace buffer manually,
12933 these commands make it easy to construct @value{GDBN} scripts that
12934 scan through the trace buffer and print out whatever collected data
12935 you are interested in. Thus, if we want to examine the PC, FP, and SP
12936 registers from each trace frame in the buffer, we can say this:
12939 (@value{GDBP}) @b{tfind start}
12940 (@value{GDBP}) @b{while ($trace_frame != -1)}
12941 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
12942 $trace_frame, $pc, $sp, $fp
12946 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
12947 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
12948 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
12949 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
12950 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
12951 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
12952 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
12953 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
12954 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
12955 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
12956 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
12959 Or, if we want to examine the variable @code{X} at each source line in
12963 (@value{GDBP}) @b{tfind start}
12964 (@value{GDBP}) @b{while ($trace_frame != -1)}
12965 > printf "Frame %d, X == %d\n", $trace_frame, X
12975 @subsection @code{tdump}
12977 @cindex dump all data collected at tracepoint
12978 @cindex tracepoint data, display
12980 This command takes no arguments. It prints all the data collected at
12981 the current trace snapshot.
12984 (@value{GDBP}) @b{trace 444}
12985 (@value{GDBP}) @b{actions}
12986 Enter actions for tracepoint #2, one per line:
12987 > collect $regs, $locals, $args, gdb_long_test
12990 (@value{GDBP}) @b{tstart}
12992 (@value{GDBP}) @b{tfind line 444}
12993 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
12995 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
12997 (@value{GDBP}) @b{tdump}
12998 Data collected at tracepoint 2, trace frame 1:
12999 d0 0xc4aa0085 -995491707
13003 d4 0x71aea3d 119204413
13006 d7 0x380035 3670069
13007 a0 0x19e24a 1696330
13008 a1 0x3000668 50333288
13010 a3 0x322000 3284992
13011 a4 0x3000698 50333336
13012 a5 0x1ad3cc 1758156
13013 fp 0x30bf3c 0x30bf3c
13014 sp 0x30bf34 0x30bf34
13016 pc 0x20b2c8 0x20b2c8
13020 p = 0x20e5b4 "gdb-test"
13027 gdb_long_test = 17 '\021'
13032 @code{tdump} works by scanning the tracepoint's current collection
13033 actions and printing the value of each expression listed. So
13034 @code{tdump} can fail, if after a run, you change the tracepoint's
13035 actions to mention variables that were not collected during the run.
13037 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
13038 uses the collected value of @code{$pc} to distinguish between trace
13039 frames that were collected at the tracepoint hit, and frames that were
13040 collected while stepping. This allows it to correctly choose whether
13041 to display the basic list of collections, or the collections from the
13042 body of the while-stepping loop. However, if @code{$pc} was not collected,
13043 then @code{tdump} will always attempt to dump using the basic collection
13044 list, and may fail if a while-stepping frame does not include all the
13045 same data that is collected at the tracepoint hit.
13046 @c This is getting pretty arcane, example would be good.
13048 @node save tracepoints
13049 @subsection @code{save tracepoints @var{filename}}
13050 @kindex save tracepoints
13051 @kindex save-tracepoints
13052 @cindex save tracepoints for future sessions
13054 This command saves all current tracepoint definitions together with
13055 their actions and passcounts, into a file @file{@var{filename}}
13056 suitable for use in a later debugging session. To read the saved
13057 tracepoint definitions, use the @code{source} command (@pxref{Command
13058 Files}). The @w{@code{save-tracepoints}} command is a deprecated
13059 alias for @w{@code{save tracepoints}}
13061 @node Tracepoint Variables
13062 @section Convenience Variables for Tracepoints
13063 @cindex tracepoint variables
13064 @cindex convenience variables for tracepoints
13067 @vindex $trace_frame
13068 @item (int) $trace_frame
13069 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
13070 snapshot is selected.
13072 @vindex $tracepoint
13073 @item (int) $tracepoint
13074 The tracepoint for the current trace snapshot.
13076 @vindex $trace_line
13077 @item (int) $trace_line
13078 The line number for the current trace snapshot.
13080 @vindex $trace_file
13081 @item (char []) $trace_file
13082 The source file for the current trace snapshot.
13084 @vindex $trace_func
13085 @item (char []) $trace_func
13086 The name of the function containing @code{$tracepoint}.
13089 Note: @code{$trace_file} is not suitable for use in @code{printf},
13090 use @code{output} instead.
13092 Here's a simple example of using these convenience variables for
13093 stepping through all the trace snapshots and printing some of their
13094 data. Note that these are not the same as trace state variables,
13095 which are managed by the target.
13098 (@value{GDBP}) @b{tfind start}
13100 (@value{GDBP}) @b{while $trace_frame != -1}
13101 > output $trace_file
13102 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
13108 @section Using Trace Files
13109 @cindex trace files
13111 In some situations, the target running a trace experiment may no
13112 longer be available; perhaps it crashed, or the hardware was needed
13113 for a different activity. To handle these cases, you can arrange to
13114 dump the trace data into a file, and later use that file as a source
13115 of trace data, via the @code{target tfile} command.
13120 @item tsave [ -r ] @var{filename}
13121 @itemx tsave [-ctf] @var{dirname}
13122 Save the trace data to @var{filename}. By default, this command
13123 assumes that @var{filename} refers to the host filesystem, so if
13124 necessary @value{GDBN} will copy raw trace data up from the target and
13125 then save it. If the target supports it, you can also supply the
13126 optional argument @code{-r} (``remote'') to direct the target to save
13127 the data directly into @var{filename} in its own filesystem, which may be
13128 more efficient if the trace buffer is very large. (Note, however, that
13129 @code{target tfile} can only read from files accessible to the host.)
13130 By default, this command will save trace frame in tfile format.
13131 You can supply the optional argument @code{-ctf} to save date in CTF
13132 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
13133 that can be shared by multiple debugging and tracing tools. Please go to
13134 @indicateurl{http://www.efficios.com/ctf} to get more information.
13136 @kindex target tfile
13140 @item target tfile @var{filename}
13141 @itemx target ctf @var{dirname}
13142 Use the file named @var{filename} or directory named @var{dirname} as
13143 a source of trace data. Commands that examine data work as they do with
13144 a live target, but it is not possible to run any new trace experiments.
13145 @code{tstatus} will report the state of the trace run at the moment
13146 the data was saved, as well as the current trace frame you are examining.
13147 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
13151 (@value{GDBP}) target ctf ctf.ctf
13152 (@value{GDBP}) tfind
13153 Found trace frame 0, tracepoint 2
13154 39 ++a; /* set tracepoint 1 here */
13155 (@value{GDBP}) tdump
13156 Data collected at tracepoint 2, trace frame 0:
13160 c = @{"123", "456", "789", "123", "456", "789"@}
13161 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
13169 @chapter Debugging Programs That Use Overlays
13172 If your program is too large to fit completely in your target system's
13173 memory, you can sometimes use @dfn{overlays} to work around this
13174 problem. @value{GDBN} provides some support for debugging programs that
13178 * How Overlays Work:: A general explanation of overlays.
13179 * Overlay Commands:: Managing overlays in @value{GDBN}.
13180 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
13181 mapped by asking the inferior.
13182 * Overlay Sample Program:: A sample program using overlays.
13185 @node How Overlays Work
13186 @section How Overlays Work
13187 @cindex mapped overlays
13188 @cindex unmapped overlays
13189 @cindex load address, overlay's
13190 @cindex mapped address
13191 @cindex overlay area
13193 Suppose you have a computer whose instruction address space is only 64
13194 kilobytes long, but which has much more memory which can be accessed by
13195 other means: special instructions, segment registers, or memory
13196 management hardware, for example. Suppose further that you want to
13197 adapt a program which is larger than 64 kilobytes to run on this system.
13199 One solution is to identify modules of your program which are relatively
13200 independent, and need not call each other directly; call these modules
13201 @dfn{overlays}. Separate the overlays from the main program, and place
13202 their machine code in the larger memory. Place your main program in
13203 instruction memory, but leave at least enough space there to hold the
13204 largest overlay as well.
13206 Now, to call a function located in an overlay, you must first copy that
13207 overlay's machine code from the large memory into the space set aside
13208 for it in the instruction memory, and then jump to its entry point
13211 @c NB: In the below the mapped area's size is greater or equal to the
13212 @c size of all overlays. This is intentional to remind the developer
13213 @c that overlays don't necessarily need to be the same size.
13217 Data Instruction Larger
13218 Address Space Address Space Address Space
13219 +-----------+ +-----------+ +-----------+
13221 +-----------+ +-----------+ +-----------+<-- overlay 1
13222 | program | | main | .----| overlay 1 | load address
13223 | variables | | program | | +-----------+
13224 | and heap | | | | | |
13225 +-----------+ | | | +-----------+<-- overlay 2
13226 | | +-----------+ | | | load address
13227 +-----------+ | | | .-| overlay 2 |
13229 mapped --->+-----------+ | | +-----------+
13230 address | | | | | |
13231 | overlay | <-' | | |
13232 | area | <---' +-----------+<-- overlay 3
13233 | | <---. | | load address
13234 +-----------+ `--| overlay 3 |
13241 @anchor{A code overlay}A code overlay
13245 The diagram (@pxref{A code overlay}) shows a system with separate data
13246 and instruction address spaces. To map an overlay, the program copies
13247 its code from the larger address space to the instruction address space.
13248 Since the overlays shown here all use the same mapped address, only one
13249 may be mapped at a time. For a system with a single address space for
13250 data and instructions, the diagram would be similar, except that the
13251 program variables and heap would share an address space with the main
13252 program and the overlay area.
13254 An overlay loaded into instruction memory and ready for use is called a
13255 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
13256 instruction memory. An overlay not present (or only partially present)
13257 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
13258 is its address in the larger memory. The mapped address is also called
13259 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
13260 called the @dfn{load memory address}, or @dfn{LMA}.
13262 Unfortunately, overlays are not a completely transparent way to adapt a
13263 program to limited instruction memory. They introduce a new set of
13264 global constraints you must keep in mind as you design your program:
13269 Before calling or returning to a function in an overlay, your program
13270 must make sure that overlay is actually mapped. Otherwise, the call or
13271 return will transfer control to the right address, but in the wrong
13272 overlay, and your program will probably crash.
13275 If the process of mapping an overlay is expensive on your system, you
13276 will need to choose your overlays carefully to minimize their effect on
13277 your program's performance.
13280 The executable file you load onto your system must contain each
13281 overlay's instructions, appearing at the overlay's load address, not its
13282 mapped address. However, each overlay's instructions must be relocated
13283 and its symbols defined as if the overlay were at its mapped address.
13284 You can use GNU linker scripts to specify different load and relocation
13285 addresses for pieces of your program; see @ref{Overlay Description,,,
13286 ld.info, Using ld: the GNU linker}.
13289 The procedure for loading executable files onto your system must be able
13290 to load their contents into the larger address space as well as the
13291 instruction and data spaces.
13295 The overlay system described above is rather simple, and could be
13296 improved in many ways:
13301 If your system has suitable bank switch registers or memory management
13302 hardware, you could use those facilities to make an overlay's load area
13303 contents simply appear at their mapped address in instruction space.
13304 This would probably be faster than copying the overlay to its mapped
13305 area in the usual way.
13308 If your overlays are small enough, you could set aside more than one
13309 overlay area, and have more than one overlay mapped at a time.
13312 You can use overlays to manage data, as well as instructions. In
13313 general, data overlays are even less transparent to your design than
13314 code overlays: whereas code overlays only require care when you call or
13315 return to functions, data overlays require care every time you access
13316 the data. Also, if you change the contents of a data overlay, you
13317 must copy its contents back out to its load address before you can copy a
13318 different data overlay into the same mapped area.
13323 @node Overlay Commands
13324 @section Overlay Commands
13326 To use @value{GDBN}'s overlay support, each overlay in your program must
13327 correspond to a separate section of the executable file. The section's
13328 virtual memory address and load memory address must be the overlay's
13329 mapped and load addresses. Identifying overlays with sections allows
13330 @value{GDBN} to determine the appropriate address of a function or
13331 variable, depending on whether the overlay is mapped or not.
13333 @value{GDBN}'s overlay commands all start with the word @code{overlay};
13334 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
13339 Disable @value{GDBN}'s overlay support. When overlay support is
13340 disabled, @value{GDBN} assumes that all functions and variables are
13341 always present at their mapped addresses. By default, @value{GDBN}'s
13342 overlay support is disabled.
13344 @item overlay manual
13345 @cindex manual overlay debugging
13346 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
13347 relies on you to tell it which overlays are mapped, and which are not,
13348 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
13349 commands described below.
13351 @item overlay map-overlay @var{overlay}
13352 @itemx overlay map @var{overlay}
13353 @cindex map an overlay
13354 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
13355 be the name of the object file section containing the overlay. When an
13356 overlay is mapped, @value{GDBN} assumes it can find the overlay's
13357 functions and variables at their mapped addresses. @value{GDBN} assumes
13358 that any other overlays whose mapped ranges overlap that of
13359 @var{overlay} are now unmapped.
13361 @item overlay unmap-overlay @var{overlay}
13362 @itemx overlay unmap @var{overlay}
13363 @cindex unmap an overlay
13364 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
13365 must be the name of the object file section containing the overlay.
13366 When an overlay is unmapped, @value{GDBN} assumes it can find the
13367 overlay's functions and variables at their load addresses.
13370 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
13371 consults a data structure the overlay manager maintains in the inferior
13372 to see which overlays are mapped. For details, see @ref{Automatic
13373 Overlay Debugging}.
13375 @item overlay load-target
13376 @itemx overlay load
13377 @cindex reloading the overlay table
13378 Re-read the overlay table from the inferior. Normally, @value{GDBN}
13379 re-reads the table @value{GDBN} automatically each time the inferior
13380 stops, so this command should only be necessary if you have changed the
13381 overlay mapping yourself using @value{GDBN}. This command is only
13382 useful when using automatic overlay debugging.
13384 @item overlay list-overlays
13385 @itemx overlay list
13386 @cindex listing mapped overlays
13387 Display a list of the overlays currently mapped, along with their mapped
13388 addresses, load addresses, and sizes.
13392 Normally, when @value{GDBN} prints a code address, it includes the name
13393 of the function the address falls in:
13396 (@value{GDBP}) print main
13397 $3 = @{int ()@} 0x11a0 <main>
13400 When overlay debugging is enabled, @value{GDBN} recognizes code in
13401 unmapped overlays, and prints the names of unmapped functions with
13402 asterisks around them. For example, if @code{foo} is a function in an
13403 unmapped overlay, @value{GDBN} prints it this way:
13406 (@value{GDBP}) overlay list
13407 No sections are mapped.
13408 (@value{GDBP}) print foo
13409 $5 = @{int (int)@} 0x100000 <*foo*>
13412 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
13416 (@value{GDBP}) overlay list
13417 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
13418 mapped at 0x1016 - 0x104a
13419 (@value{GDBP}) print foo
13420 $6 = @{int (int)@} 0x1016 <foo>
13423 When overlay debugging is enabled, @value{GDBN} can find the correct
13424 address for functions and variables in an overlay, whether or not the
13425 overlay is mapped. This allows most @value{GDBN} commands, like
13426 @code{break} and @code{disassemble}, to work normally, even on unmapped
13427 code. However, @value{GDBN}'s breakpoint support has some limitations:
13431 @cindex breakpoints in overlays
13432 @cindex overlays, setting breakpoints in
13433 You can set breakpoints in functions in unmapped overlays, as long as
13434 @value{GDBN} can write to the overlay at its load address.
13436 @value{GDBN} can not set hardware or simulator-based breakpoints in
13437 unmapped overlays. However, if you set a breakpoint at the end of your
13438 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
13439 you are using manual overlay management), @value{GDBN} will re-set its
13440 breakpoints properly.
13444 @node Automatic Overlay Debugging
13445 @section Automatic Overlay Debugging
13446 @cindex automatic overlay debugging
13448 @value{GDBN} can automatically track which overlays are mapped and which
13449 are not, given some simple co-operation from the overlay manager in the
13450 inferior. If you enable automatic overlay debugging with the
13451 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
13452 looks in the inferior's memory for certain variables describing the
13453 current state of the overlays.
13455 Here are the variables your overlay manager must define to support
13456 @value{GDBN}'s automatic overlay debugging:
13460 @item @code{_ovly_table}:
13461 This variable must be an array of the following structures:
13466 /* The overlay's mapped address. */
13469 /* The size of the overlay, in bytes. */
13470 unsigned long size;
13472 /* The overlay's load address. */
13475 /* Non-zero if the overlay is currently mapped;
13477 unsigned long mapped;
13481 @item @code{_novlys}:
13482 This variable must be a four-byte signed integer, holding the total
13483 number of elements in @code{_ovly_table}.
13487 To decide whether a particular overlay is mapped or not, @value{GDBN}
13488 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
13489 @code{lma} members equal the VMA and LMA of the overlay's section in the
13490 executable file. When @value{GDBN} finds a matching entry, it consults
13491 the entry's @code{mapped} member to determine whether the overlay is
13494 In addition, your overlay manager may define a function called
13495 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
13496 will silently set a breakpoint there. If the overlay manager then
13497 calls this function whenever it has changed the overlay table, this
13498 will enable @value{GDBN} to accurately keep track of which overlays
13499 are in program memory, and update any breakpoints that may be set
13500 in overlays. This will allow breakpoints to work even if the
13501 overlays are kept in ROM or other non-writable memory while they
13502 are not being executed.
13504 @node Overlay Sample Program
13505 @section Overlay Sample Program
13506 @cindex overlay example program
13508 When linking a program which uses overlays, you must place the overlays
13509 at their load addresses, while relocating them to run at their mapped
13510 addresses. To do this, you must write a linker script (@pxref{Overlay
13511 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
13512 since linker scripts are specific to a particular host system, target
13513 architecture, and target memory layout, this manual cannot provide
13514 portable sample code demonstrating @value{GDBN}'s overlay support.
13516 However, the @value{GDBN} source distribution does contain an overlaid
13517 program, with linker scripts for a few systems, as part of its test
13518 suite. The program consists of the following files from
13519 @file{gdb/testsuite/gdb.base}:
13523 The main program file.
13525 A simple overlay manager, used by @file{overlays.c}.
13530 Overlay modules, loaded and used by @file{overlays.c}.
13533 Linker scripts for linking the test program on the @code{d10v-elf}
13534 and @code{m32r-elf} targets.
13537 You can build the test program using the @code{d10v-elf} GCC
13538 cross-compiler like this:
13541 $ d10v-elf-gcc -g -c overlays.c
13542 $ d10v-elf-gcc -g -c ovlymgr.c
13543 $ d10v-elf-gcc -g -c foo.c
13544 $ d10v-elf-gcc -g -c bar.c
13545 $ d10v-elf-gcc -g -c baz.c
13546 $ d10v-elf-gcc -g -c grbx.c
13547 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
13548 baz.o grbx.o -Wl,-Td10v.ld -o overlays
13551 The build process is identical for any other architecture, except that
13552 you must substitute the appropriate compiler and linker script for the
13553 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
13557 @chapter Using @value{GDBN} with Different Languages
13560 Although programming languages generally have common aspects, they are
13561 rarely expressed in the same manner. For instance, in ANSI C,
13562 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
13563 Modula-2, it is accomplished by @code{p^}. Values can also be
13564 represented (and displayed) differently. Hex numbers in C appear as
13565 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
13567 @cindex working language
13568 Language-specific information is built into @value{GDBN} for some languages,
13569 allowing you to express operations like the above in your program's
13570 native language, and allowing @value{GDBN} to output values in a manner
13571 consistent with the syntax of your program's native language. The
13572 language you use to build expressions is called the @dfn{working
13576 * Setting:: Switching between source languages
13577 * Show:: Displaying the language
13578 * Checks:: Type and range checks
13579 * Supported Languages:: Supported languages
13580 * Unsupported Languages:: Unsupported languages
13584 @section Switching Between Source Languages
13586 There are two ways to control the working language---either have @value{GDBN}
13587 set it automatically, or select it manually yourself. You can use the
13588 @code{set language} command for either purpose. On startup, @value{GDBN}
13589 defaults to setting the language automatically. The working language is
13590 used to determine how expressions you type are interpreted, how values
13593 In addition to the working language, every source file that
13594 @value{GDBN} knows about has its own working language. For some object
13595 file formats, the compiler might indicate which language a particular
13596 source file is in. However, most of the time @value{GDBN} infers the
13597 language from the name of the file. The language of a source file
13598 controls whether C@t{++} names are demangled---this way @code{backtrace} can
13599 show each frame appropriately for its own language. There is no way to
13600 set the language of a source file from within @value{GDBN}, but you can
13601 set the language associated with a filename extension. @xref{Show, ,
13602 Displaying the Language}.
13604 This is most commonly a problem when you use a program, such
13605 as @code{cfront} or @code{f2c}, that generates C but is written in
13606 another language. In that case, make the
13607 program use @code{#line} directives in its C output; that way
13608 @value{GDBN} will know the correct language of the source code of the original
13609 program, and will display that source code, not the generated C code.
13612 * Filenames:: Filename extensions and languages.
13613 * Manually:: Setting the working language manually
13614 * Automatically:: Having @value{GDBN} infer the source language
13618 @subsection List of Filename Extensions and Languages
13620 If a source file name ends in one of the following extensions, then
13621 @value{GDBN} infers that its language is the one indicated.
13639 C@t{++} source file
13645 Objective-C source file
13649 Fortran source file
13652 Modula-2 source file
13656 Assembler source file. This actually behaves almost like C, but
13657 @value{GDBN} does not skip over function prologues when stepping.
13660 In addition, you may set the language associated with a filename
13661 extension. @xref{Show, , Displaying the Language}.
13664 @subsection Setting the Working Language
13666 If you allow @value{GDBN} to set the language automatically,
13667 expressions are interpreted the same way in your debugging session and
13670 @kindex set language
13671 If you wish, you may set the language manually. To do this, issue the
13672 command @samp{set language @var{lang}}, where @var{lang} is the name of
13673 a language, such as
13674 @code{c} or @code{modula-2}.
13675 For a list of the supported languages, type @samp{set language}.
13677 Setting the language manually prevents @value{GDBN} from updating the working
13678 language automatically. This can lead to confusion if you try
13679 to debug a program when the working language is not the same as the
13680 source language, when an expression is acceptable to both
13681 languages---but means different things. For instance, if the current
13682 source file were written in C, and @value{GDBN} was parsing Modula-2, a
13690 might not have the effect you intended. In C, this means to add
13691 @code{b} and @code{c} and place the result in @code{a}. The result
13692 printed would be the value of @code{a}. In Modula-2, this means to compare
13693 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
13695 @node Automatically
13696 @subsection Having @value{GDBN} Infer the Source Language
13698 To have @value{GDBN} set the working language automatically, use
13699 @samp{set language local} or @samp{set language auto}. @value{GDBN}
13700 then infers the working language. That is, when your program stops in a
13701 frame (usually by encountering a breakpoint), @value{GDBN} sets the
13702 working language to the language recorded for the function in that
13703 frame. If the language for a frame is unknown (that is, if the function
13704 or block corresponding to the frame was defined in a source file that
13705 does not have a recognized extension), the current working language is
13706 not changed, and @value{GDBN} issues a warning.
13708 This may not seem necessary for most programs, which are written
13709 entirely in one source language. However, program modules and libraries
13710 written in one source language can be used by a main program written in
13711 a different source language. Using @samp{set language auto} in this
13712 case frees you from having to set the working language manually.
13715 @section Displaying the Language
13717 The following commands help you find out which language is the
13718 working language, and also what language source files were written in.
13721 @item show language
13722 @anchor{show language}
13723 @kindex show language
13724 Display the current working language. This is the
13725 language you can use with commands such as @code{print} to
13726 build and compute expressions that may involve variables in your program.
13729 @kindex info frame@r{, show the source language}
13730 Display the source language for this frame. This language becomes the
13731 working language if you use an identifier from this frame.
13732 @xref{Frame Info, ,Information about a Frame}, to identify the other
13733 information listed here.
13736 @kindex info source@r{, show the source language}
13737 Display the source language of this source file.
13738 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
13739 information listed here.
13742 In unusual circumstances, you may have source files with extensions
13743 not in the standard list. You can then set the extension associated
13744 with a language explicitly:
13747 @item set extension-language @var{ext} @var{language}
13748 @kindex set extension-language
13749 Tell @value{GDBN} that source files with extension @var{ext} are to be
13750 assumed as written in the source language @var{language}.
13752 @item info extensions
13753 @kindex info extensions
13754 List all the filename extensions and the associated languages.
13758 @section Type and Range Checking
13760 Some languages are designed to guard you against making seemingly common
13761 errors through a series of compile- and run-time checks. These include
13762 checking the type of arguments to functions and operators and making
13763 sure mathematical overflows are caught at run time. Checks such as
13764 these help to ensure a program's correctness once it has been compiled
13765 by eliminating type mismatches and providing active checks for range
13766 errors when your program is running.
13768 By default @value{GDBN} checks for these errors according to the
13769 rules of the current source language. Although @value{GDBN} does not check
13770 the statements in your program, it can check expressions entered directly
13771 into @value{GDBN} for evaluation via the @code{print} command, for example.
13774 * Type Checking:: An overview of type checking
13775 * Range Checking:: An overview of range checking
13778 @cindex type checking
13779 @cindex checks, type
13780 @node Type Checking
13781 @subsection An Overview of Type Checking
13783 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
13784 arguments to operators and functions have to be of the correct type,
13785 otherwise an error occurs. These checks prevent type mismatch
13786 errors from ever causing any run-time problems. For example,
13789 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
13791 (@value{GDBP}) print obj.my_method (0)
13794 (@value{GDBP}) print obj.my_method (0x1234)
13795 Cannot resolve method klass::my_method to any overloaded instance
13798 The second example fails because in C@t{++} the integer constant
13799 @samp{0x1234} is not type-compatible with the pointer parameter type.
13801 For the expressions you use in @value{GDBN} commands, you can tell
13802 @value{GDBN} to not enforce strict type checking or
13803 to treat any mismatches as errors and abandon the expression;
13804 When type checking is disabled, @value{GDBN} successfully evaluates
13805 expressions like the second example above.
13807 Even if type checking is off, there may be other reasons
13808 related to type that prevent @value{GDBN} from evaluating an expression.
13809 For instance, @value{GDBN} does not know how to add an @code{int} and
13810 a @code{struct foo}. These particular type errors have nothing to do
13811 with the language in use and usually arise from expressions which make
13812 little sense to evaluate anyway.
13814 @value{GDBN} provides some additional commands for controlling type checking:
13816 @kindex set check type
13817 @kindex show check type
13819 @item set check type on
13820 @itemx set check type off
13821 Set strict type checking on or off. If any type mismatches occur in
13822 evaluating an expression while type checking is on, @value{GDBN} prints a
13823 message and aborts evaluation of the expression.
13825 @item show check type
13826 Show the current setting of type checking and whether @value{GDBN}
13827 is enforcing strict type checking rules.
13830 @cindex range checking
13831 @cindex checks, range
13832 @node Range Checking
13833 @subsection An Overview of Range Checking
13835 In some languages (such as Modula-2), it is an error to exceed the
13836 bounds of a type; this is enforced with run-time checks. Such range
13837 checking is meant to ensure program correctness by making sure
13838 computations do not overflow, or indices on an array element access do
13839 not exceed the bounds of the array.
13841 For expressions you use in @value{GDBN} commands, you can tell
13842 @value{GDBN} to treat range errors in one of three ways: ignore them,
13843 always treat them as errors and abandon the expression, or issue
13844 warnings but evaluate the expression anyway.
13846 A range error can result from numerical overflow, from exceeding an
13847 array index bound, or when you type a constant that is not a member
13848 of any type. Some languages, however, do not treat overflows as an
13849 error. In many implementations of C, mathematical overflow causes the
13850 result to ``wrap around'' to lower values---for example, if @var{m} is
13851 the largest integer value, and @var{s} is the smallest, then
13854 @var{m} + 1 @result{} @var{s}
13857 This, too, is specific to individual languages, and in some cases
13858 specific to individual compilers or machines. @xref{Supported Languages, ,
13859 Supported Languages}, for further details on specific languages.
13861 @value{GDBN} provides some additional commands for controlling the range checker:
13863 @kindex set check range
13864 @kindex show check range
13866 @item set check range auto
13867 Set range checking on or off based on the current working language.
13868 @xref{Supported Languages, ,Supported Languages}, for the default settings for
13871 @item set check range on
13872 @itemx set check range off
13873 Set range checking on or off, overriding the default setting for the
13874 current working language. A warning is issued if the setting does not
13875 match the language default. If a range error occurs and range checking is on,
13876 then a message is printed and evaluation of the expression is aborted.
13878 @item set check range warn
13879 Output messages when the @value{GDBN} range checker detects a range error,
13880 but attempt to evaluate the expression anyway. Evaluating the
13881 expression may still be impossible for other reasons, such as accessing
13882 memory that the process does not own (a typical example from many Unix
13886 Show the current setting of the range checker, and whether or not it is
13887 being set automatically by @value{GDBN}.
13890 @node Supported Languages
13891 @section Supported Languages
13893 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
13894 OpenCL C, Pascal, assembly, Modula-2, and Ada.
13895 @c This is false ...
13896 Some @value{GDBN} features may be used in expressions regardless of the
13897 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
13898 and the @samp{@{type@}addr} construct (@pxref{Expressions,
13899 ,Expressions}) can be used with the constructs of any supported
13902 The following sections detail to what degree each source language is
13903 supported by @value{GDBN}. These sections are not meant to be language
13904 tutorials or references, but serve only as a reference guide to what the
13905 @value{GDBN} expression parser accepts, and what input and output
13906 formats should look like for different languages. There are many good
13907 books written on each of these languages; please look to these for a
13908 language reference or tutorial.
13911 * C:: C and C@t{++}
13914 * Objective-C:: Objective-C
13915 * OpenCL C:: OpenCL C
13916 * Fortran:: Fortran
13918 * Modula-2:: Modula-2
13923 @subsection C and C@t{++}
13925 @cindex C and C@t{++}
13926 @cindex expressions in C or C@t{++}
13928 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
13929 to both languages. Whenever this is the case, we discuss those languages
13933 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
13934 @cindex @sc{gnu} C@t{++}
13935 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
13936 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
13937 effectively, you must compile your C@t{++} programs with a supported
13938 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
13939 compiler (@code{aCC}).
13942 * C Operators:: C and C@t{++} operators
13943 * C Constants:: C and C@t{++} constants
13944 * C Plus Plus Expressions:: C@t{++} expressions
13945 * C Defaults:: Default settings for C and C@t{++}
13946 * C Checks:: C and C@t{++} type and range checks
13947 * Debugging C:: @value{GDBN} and C
13948 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
13949 * Decimal Floating Point:: Numbers in Decimal Floating Point format
13953 @subsubsection C and C@t{++} Operators
13955 @cindex C and C@t{++} operators
13957 Operators must be defined on values of specific types. For instance,
13958 @code{+} is defined on numbers, but not on structures. Operators are
13959 often defined on groups of types.
13961 For the purposes of C and C@t{++}, the following definitions hold:
13966 @emph{Integral types} include @code{int} with any of its storage-class
13967 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
13970 @emph{Floating-point types} include @code{float}, @code{double}, and
13971 @code{long double} (if supported by the target platform).
13974 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
13977 @emph{Scalar types} include all of the above.
13982 The following operators are supported. They are listed here
13983 in order of increasing precedence:
13987 The comma or sequencing operator. Expressions in a comma-separated list
13988 are evaluated from left to right, with the result of the entire
13989 expression being the last expression evaluated.
13992 Assignment. The value of an assignment expression is the value
13993 assigned. Defined on scalar types.
13996 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
13997 and translated to @w{@code{@var{a} = @var{a op b}}}.
13998 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
13999 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
14000 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
14003 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
14004 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
14005 should be of an integral type.
14008 Logical @sc{or}. Defined on integral types.
14011 Logical @sc{and}. Defined on integral types.
14014 Bitwise @sc{or}. Defined on integral types.
14017 Bitwise exclusive-@sc{or}. Defined on integral types.
14020 Bitwise @sc{and}. Defined on integral types.
14023 Equality and inequality. Defined on scalar types. The value of these
14024 expressions is 0 for false and non-zero for true.
14026 @item <@r{, }>@r{, }<=@r{, }>=
14027 Less than, greater than, less than or equal, greater than or equal.
14028 Defined on scalar types. The value of these expressions is 0 for false
14029 and non-zero for true.
14032 left shift, and right shift. Defined on integral types.
14035 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14038 Addition and subtraction. Defined on integral types, floating-point types and
14041 @item *@r{, }/@r{, }%
14042 Multiplication, division, and modulus. Multiplication and division are
14043 defined on integral and floating-point types. Modulus is defined on
14047 Increment and decrement. When appearing before a variable, the
14048 operation is performed before the variable is used in an expression;
14049 when appearing after it, the variable's value is used before the
14050 operation takes place.
14053 Pointer dereferencing. Defined on pointer types. Same precedence as
14057 Address operator. Defined on variables. Same precedence as @code{++}.
14059 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
14060 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
14061 to examine the address
14062 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
14066 Negative. Defined on integral and floating-point types. Same
14067 precedence as @code{++}.
14070 Logical negation. Defined on integral types. Same precedence as
14074 Bitwise complement operator. Defined on integral types. Same precedence as
14079 Structure member, and pointer-to-structure member. For convenience,
14080 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
14081 pointer based on the stored type information.
14082 Defined on @code{struct} and @code{union} data.
14085 Dereferences of pointers to members.
14088 Array indexing. @code{@var{a}[@var{i}]} is defined as
14089 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
14092 Function parameter list. Same precedence as @code{->}.
14095 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
14096 and @code{class} types.
14099 Doubled colons also represent the @value{GDBN} scope operator
14100 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
14104 If an operator is redefined in the user code, @value{GDBN} usually
14105 attempts to invoke the redefined version instead of using the operator's
14106 predefined meaning.
14109 @subsubsection C and C@t{++} Constants
14111 @cindex C and C@t{++} constants
14113 @value{GDBN} allows you to express the constants of C and C@t{++} in the
14118 Integer constants are a sequence of digits. Octal constants are
14119 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
14120 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
14121 @samp{l}, specifying that the constant should be treated as a
14125 Floating point constants are a sequence of digits, followed by a decimal
14126 point, followed by a sequence of digits, and optionally followed by an
14127 exponent. An exponent is of the form:
14128 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
14129 sequence of digits. The @samp{+} is optional for positive exponents.
14130 A floating-point constant may also end with a letter @samp{f} or
14131 @samp{F}, specifying that the constant should be treated as being of
14132 the @code{float} (as opposed to the default @code{double}) type; or with
14133 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
14137 Enumerated constants consist of enumerated identifiers, or their
14138 integral equivalents.
14141 Character constants are a single character surrounded by single quotes
14142 (@code{'}), or a number---the ordinal value of the corresponding character
14143 (usually its @sc{ascii} value). Within quotes, the single character may
14144 be represented by a letter or by @dfn{escape sequences}, which are of
14145 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
14146 of the character's ordinal value; or of the form @samp{\@var{x}}, where
14147 @samp{@var{x}} is a predefined special character---for example,
14148 @samp{\n} for newline.
14150 Wide character constants can be written by prefixing a character
14151 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
14152 form of @samp{x}. The target wide character set is used when
14153 computing the value of this constant (@pxref{Character Sets}).
14156 String constants are a sequence of character constants surrounded by
14157 double quotes (@code{"}). Any valid character constant (as described
14158 above) may appear. Double quotes within the string must be preceded by
14159 a backslash, so for instance @samp{"a\"b'c"} is a string of five
14162 Wide string constants can be written by prefixing a string constant
14163 with @samp{L}, as in C. The target wide character set is used when
14164 computing the value of this constant (@pxref{Character Sets}).
14167 Pointer constants are an integral value. You can also write pointers
14168 to constants using the C operator @samp{&}.
14171 Array constants are comma-separated lists surrounded by braces @samp{@{}
14172 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
14173 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
14174 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
14177 @node C Plus Plus Expressions
14178 @subsubsection C@t{++} Expressions
14180 @cindex expressions in C@t{++}
14181 @value{GDBN} expression handling can interpret most C@t{++} expressions.
14183 @cindex debugging C@t{++} programs
14184 @cindex C@t{++} compilers
14185 @cindex debug formats and C@t{++}
14186 @cindex @value{NGCC} and C@t{++}
14188 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
14189 the proper compiler and the proper debug format. Currently,
14190 @value{GDBN} works best when debugging C@t{++} code that is compiled
14191 with the most recent version of @value{NGCC} possible. The DWARF
14192 debugging format is preferred; @value{NGCC} defaults to this on most
14193 popular platforms. Other compilers and/or debug formats are likely to
14194 work badly or not at all when using @value{GDBN} to debug C@t{++}
14195 code. @xref{Compilation}.
14200 @cindex member functions
14202 Member function calls are allowed; you can use expressions like
14205 count = aml->GetOriginal(x, y)
14208 @vindex this@r{, inside C@t{++} member functions}
14209 @cindex namespace in C@t{++}
14211 While a member function is active (in the selected stack frame), your
14212 expressions have the same namespace available as the member function;
14213 that is, @value{GDBN} allows implicit references to the class instance
14214 pointer @code{this} following the same rules as C@t{++}. @code{using}
14215 declarations in the current scope are also respected by @value{GDBN}.
14217 @cindex call overloaded functions
14218 @cindex overloaded functions, calling
14219 @cindex type conversions in C@t{++}
14221 You can call overloaded functions; @value{GDBN} resolves the function
14222 call to the right definition, with some restrictions. @value{GDBN} does not
14223 perform overload resolution involving user-defined type conversions,
14224 calls to constructors, or instantiations of templates that do not exist
14225 in the program. It also cannot handle ellipsis argument lists or
14228 It does perform integral conversions and promotions, floating-point
14229 promotions, arithmetic conversions, pointer conversions, conversions of
14230 class objects to base classes, and standard conversions such as those of
14231 functions or arrays to pointers; it requires an exact match on the
14232 number of function arguments.
14234 Overload resolution is always performed, unless you have specified
14235 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
14236 ,@value{GDBN} Features for C@t{++}}.
14238 You must specify @code{set overload-resolution off} in order to use an
14239 explicit function signature to call an overloaded function, as in
14241 p 'foo(char,int)'('x', 13)
14244 The @value{GDBN} command-completion facility can simplify this;
14245 see @ref{Completion, ,Command Completion}.
14247 @cindex reference declarations
14249 @value{GDBN} understands variables declared as C@t{++} references; you can use
14250 them in expressions just as you do in C@t{++} source---they are automatically
14253 In the parameter list shown when @value{GDBN} displays a frame, the values of
14254 reference variables are not displayed (unlike other variables); this
14255 avoids clutter, since references are often used for large structures.
14256 The @emph{address} of a reference variable is always shown, unless
14257 you have specified @samp{set print address off}.
14260 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
14261 expressions can use it just as expressions in your program do. Since
14262 one scope may be defined in another, you can use @code{::} repeatedly if
14263 necessary, for example in an expression like
14264 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
14265 resolving name scope by reference to source files, in both C and C@t{++}
14266 debugging (@pxref{Variables, ,Program Variables}).
14269 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
14274 @subsubsection C and C@t{++} Defaults
14276 @cindex C and C@t{++} defaults
14278 If you allow @value{GDBN} to set range checking automatically, it
14279 defaults to @code{off} whenever the working language changes to
14280 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
14281 selects the working language.
14283 If you allow @value{GDBN} to set the language automatically, it
14284 recognizes source files whose names end with @file{.c}, @file{.C}, or
14285 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
14286 these files, it sets the working language to C or C@t{++}.
14287 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
14288 for further details.
14291 @subsubsection C and C@t{++} Type and Range Checks
14293 @cindex C and C@t{++} checks
14295 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
14296 checking is used. However, if you turn type checking off, @value{GDBN}
14297 will allow certain non-standard conversions, such as promoting integer
14298 constants to pointers.
14300 Range checking, if turned on, is done on mathematical operations. Array
14301 indices are not checked, since they are often used to index a pointer
14302 that is not itself an array.
14305 @subsubsection @value{GDBN} and C
14307 The @code{set print union} and @code{show print union} commands apply to
14308 the @code{union} type. When set to @samp{on}, any @code{union} that is
14309 inside a @code{struct} or @code{class} is also printed. Otherwise, it
14310 appears as @samp{@{...@}}.
14312 The @code{@@} operator aids in the debugging of dynamic arrays, formed
14313 with pointers and a memory allocation function. @xref{Expressions,
14316 @node Debugging C Plus Plus
14317 @subsubsection @value{GDBN} Features for C@t{++}
14319 @cindex commands for C@t{++}
14321 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
14322 designed specifically for use with C@t{++}. Here is a summary:
14325 @cindex break in overloaded functions
14326 @item @r{breakpoint menus}
14327 When you want a breakpoint in a function whose name is overloaded,
14328 @value{GDBN} has the capability to display a menu of possible breakpoint
14329 locations to help you specify which function definition you want.
14330 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
14332 @cindex overloading in C@t{++}
14333 @item rbreak @var{regex}
14334 Setting breakpoints using regular expressions is helpful for setting
14335 breakpoints on overloaded functions that are not members of any special
14337 @xref{Set Breaks, ,Setting Breakpoints}.
14339 @cindex C@t{++} exception handling
14341 @itemx catch rethrow
14343 Debug C@t{++} exception handling using these commands. @xref{Set
14344 Catchpoints, , Setting Catchpoints}.
14346 @cindex inheritance
14347 @item ptype @var{typename}
14348 Print inheritance relationships as well as other information for type
14350 @xref{Symbols, ,Examining the Symbol Table}.
14352 @item info vtbl @var{expression}.
14353 The @code{info vtbl} command can be used to display the virtual
14354 method tables of the object computed by @var{expression}. This shows
14355 one entry per virtual table; there may be multiple virtual tables when
14356 multiple inheritance is in use.
14358 @cindex C@t{++} demangling
14359 @item demangle @var{name}
14360 Demangle @var{name}.
14361 @xref{Symbols}, for a more complete description of the @code{demangle} command.
14363 @cindex C@t{++} symbol display
14364 @item set print demangle
14365 @itemx show print demangle
14366 @itemx set print asm-demangle
14367 @itemx show print asm-demangle
14368 Control whether C@t{++} symbols display in their source form, both when
14369 displaying code as C@t{++} source and when displaying disassemblies.
14370 @xref{Print Settings, ,Print Settings}.
14372 @item set print object
14373 @itemx show print object
14374 Choose whether to print derived (actual) or declared types of objects.
14375 @xref{Print Settings, ,Print Settings}.
14377 @item set print vtbl
14378 @itemx show print vtbl
14379 Control the format for printing virtual function tables.
14380 @xref{Print Settings, ,Print Settings}.
14381 (The @code{vtbl} commands do not work on programs compiled with the HP
14382 ANSI C@t{++} compiler (@code{aCC}).)
14384 @kindex set overload-resolution
14385 @cindex overloaded functions, overload resolution
14386 @item set overload-resolution on
14387 Enable overload resolution for C@t{++} expression evaluation. The default
14388 is on. For overloaded functions, @value{GDBN} evaluates the arguments
14389 and searches for a function whose signature matches the argument types,
14390 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
14391 Expressions, ,C@t{++} Expressions}, for details).
14392 If it cannot find a match, it emits a message.
14394 @item set overload-resolution off
14395 Disable overload resolution for C@t{++} expression evaluation. For
14396 overloaded functions that are not class member functions, @value{GDBN}
14397 chooses the first function of the specified name that it finds in the
14398 symbol table, whether or not its arguments are of the correct type. For
14399 overloaded functions that are class member functions, @value{GDBN}
14400 searches for a function whose signature @emph{exactly} matches the
14403 @kindex show overload-resolution
14404 @item show overload-resolution
14405 Show the current setting of overload resolution.
14407 @item @r{Overloaded symbol names}
14408 You can specify a particular definition of an overloaded symbol, using
14409 the same notation that is used to declare such symbols in C@t{++}: type
14410 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
14411 also use the @value{GDBN} command-line word completion facilities to list the
14412 available choices, or to finish the type list for you.
14413 @xref{Completion,, Command Completion}, for details on how to do this.
14416 @node Decimal Floating Point
14417 @subsubsection Decimal Floating Point format
14418 @cindex decimal floating point format
14420 @value{GDBN} can examine, set and perform computations with numbers in
14421 decimal floating point format, which in the C language correspond to the
14422 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
14423 specified by the extension to support decimal floating-point arithmetic.
14425 There are two encodings in use, depending on the architecture: BID (Binary
14426 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
14427 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
14430 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
14431 to manipulate decimal floating point numbers, it is not possible to convert
14432 (using a cast, for example) integers wider than 32-bit to decimal float.
14434 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
14435 point computations, error checking in decimal float operations ignores
14436 underflow, overflow and divide by zero exceptions.
14438 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
14439 to inspect @code{_Decimal128} values stored in floating point registers.
14440 See @ref{PowerPC,,PowerPC} for more details.
14446 @value{GDBN} can be used to debug programs written in D and compiled with
14447 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
14448 specific feature --- dynamic arrays.
14453 @cindex Go (programming language)
14454 @value{GDBN} can be used to debug programs written in Go and compiled with
14455 @file{gccgo} or @file{6g} compilers.
14457 Here is a summary of the Go-specific features and restrictions:
14460 @cindex current Go package
14461 @item The current Go package
14462 The name of the current package does not need to be specified when
14463 specifying global variables and functions.
14465 For example, given the program:
14469 var myglob = "Shall we?"
14475 When stopped inside @code{main} either of these work:
14479 (gdb) p main.myglob
14482 @cindex builtin Go types
14483 @item Builtin Go types
14484 The @code{string} type is recognized by @value{GDBN} and is printed
14487 @cindex builtin Go functions
14488 @item Builtin Go functions
14489 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
14490 function and handles it internally.
14492 @cindex restrictions on Go expressions
14493 @item Restrictions on Go expressions
14494 All Go operators are supported except @code{&^}.
14495 The Go @code{_} ``blank identifier'' is not supported.
14496 Automatic dereferencing of pointers is not supported.
14500 @subsection Objective-C
14502 @cindex Objective-C
14503 This section provides information about some commands and command
14504 options that are useful for debugging Objective-C code. See also
14505 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
14506 few more commands specific to Objective-C support.
14509 * Method Names in Commands::
14510 * The Print Command with Objective-C::
14513 @node Method Names in Commands
14514 @subsubsection Method Names in Commands
14516 The following commands have been extended to accept Objective-C method
14517 names as line specifications:
14519 @kindex clear@r{, and Objective-C}
14520 @kindex break@r{, and Objective-C}
14521 @kindex info line@r{, and Objective-C}
14522 @kindex jump@r{, and Objective-C}
14523 @kindex list@r{, and Objective-C}
14527 @item @code{info line}
14532 A fully qualified Objective-C method name is specified as
14535 -[@var{Class} @var{methodName}]
14538 where the minus sign is used to indicate an instance method and a
14539 plus sign (not shown) is used to indicate a class method. The class
14540 name @var{Class} and method name @var{methodName} are enclosed in
14541 brackets, similar to the way messages are specified in Objective-C
14542 source code. For example, to set a breakpoint at the @code{create}
14543 instance method of class @code{Fruit} in the program currently being
14547 break -[Fruit create]
14550 To list ten program lines around the @code{initialize} class method,
14554 list +[NSText initialize]
14557 In the current version of @value{GDBN}, the plus or minus sign is
14558 required. In future versions of @value{GDBN}, the plus or minus
14559 sign will be optional, but you can use it to narrow the search. It
14560 is also possible to specify just a method name:
14566 You must specify the complete method name, including any colons. If
14567 your program's source files contain more than one @code{create} method,
14568 you'll be presented with a numbered list of classes that implement that
14569 method. Indicate your choice by number, or type @samp{0} to exit if
14572 As another example, to clear a breakpoint established at the
14573 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
14576 clear -[NSWindow makeKeyAndOrderFront:]
14579 @node The Print Command with Objective-C
14580 @subsubsection The Print Command With Objective-C
14581 @cindex Objective-C, print objects
14582 @kindex print-object
14583 @kindex po @r{(@code{print-object})}
14585 The print command has also been extended to accept methods. For example:
14588 print -[@var{object} hash]
14591 @cindex print an Objective-C object description
14592 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
14594 will tell @value{GDBN} to send the @code{hash} message to @var{object}
14595 and print the result. Also, an additional command has been added,
14596 @code{print-object} or @code{po} for short, which is meant to print
14597 the description of an object. However, this command may only work
14598 with certain Objective-C libraries that have a particular hook
14599 function, @code{_NSPrintForDebugger}, defined.
14602 @subsection OpenCL C
14605 This section provides information about @value{GDBN}s OpenCL C support.
14608 * OpenCL C Datatypes::
14609 * OpenCL C Expressions::
14610 * OpenCL C Operators::
14613 @node OpenCL C Datatypes
14614 @subsubsection OpenCL C Datatypes
14616 @cindex OpenCL C Datatypes
14617 @value{GDBN} supports the builtin scalar and vector datatypes specified
14618 by OpenCL 1.1. In addition the half- and double-precision floating point
14619 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
14620 extensions are also known to @value{GDBN}.
14622 @node OpenCL C Expressions
14623 @subsubsection OpenCL C Expressions
14625 @cindex OpenCL C Expressions
14626 @value{GDBN} supports accesses to vector components including the access as
14627 lvalue where possible. Since OpenCL C is based on C99 most C expressions
14628 supported by @value{GDBN} can be used as well.
14630 @node OpenCL C Operators
14631 @subsubsection OpenCL C Operators
14633 @cindex OpenCL C Operators
14634 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
14638 @subsection Fortran
14639 @cindex Fortran-specific support in @value{GDBN}
14641 @value{GDBN} can be used to debug programs written in Fortran, but it
14642 currently supports only the features of Fortran 77 language.
14644 @cindex trailing underscore, in Fortran symbols
14645 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
14646 among them) append an underscore to the names of variables and
14647 functions. When you debug programs compiled by those compilers, you
14648 will need to refer to variables and functions with a trailing
14652 * Fortran Operators:: Fortran operators and expressions
14653 * Fortran Defaults:: Default settings for Fortran
14654 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
14657 @node Fortran Operators
14658 @subsubsection Fortran Operators and Expressions
14660 @cindex Fortran operators and expressions
14662 Operators must be defined on values of specific types. For instance,
14663 @code{+} is defined on numbers, but not on characters or other non-
14664 arithmetic types. Operators are often defined on groups of types.
14668 The exponentiation operator. It raises the first operand to the power
14672 The range operator. Normally used in the form of array(low:high) to
14673 represent a section of array.
14676 The access component operator. Normally used to access elements in derived
14677 types. Also suitable for unions. As unions aren't part of regular Fortran,
14678 this can only happen when accessing a register that uses a gdbarch-defined
14682 @node Fortran Defaults
14683 @subsubsection Fortran Defaults
14685 @cindex Fortran Defaults
14687 Fortran symbols are usually case-insensitive, so @value{GDBN} by
14688 default uses case-insensitive matches for Fortran symbols. You can
14689 change that with the @samp{set case-insensitive} command, see
14690 @ref{Symbols}, for the details.
14692 @node Special Fortran Commands
14693 @subsubsection Special Fortran Commands
14695 @cindex Special Fortran commands
14697 @value{GDBN} has some commands to support Fortran-specific features,
14698 such as displaying common blocks.
14701 @cindex @code{COMMON} blocks, Fortran
14702 @kindex info common
14703 @item info common @r{[}@var{common-name}@r{]}
14704 This command prints the values contained in the Fortran @code{COMMON}
14705 block whose name is @var{common-name}. With no argument, the names of
14706 all @code{COMMON} blocks visible at the current program location are
14713 @cindex Pascal support in @value{GDBN}, limitations
14714 Debugging Pascal programs which use sets, subranges, file variables, or
14715 nested functions does not currently work. @value{GDBN} does not support
14716 entering expressions, printing values, or similar features using Pascal
14719 The Pascal-specific command @code{set print pascal_static-members}
14720 controls whether static members of Pascal objects are displayed.
14721 @xref{Print Settings, pascal_static-members}.
14724 @subsection Modula-2
14726 @cindex Modula-2, @value{GDBN} support
14728 The extensions made to @value{GDBN} to support Modula-2 only support
14729 output from the @sc{gnu} Modula-2 compiler (which is currently being
14730 developed). Other Modula-2 compilers are not currently supported, and
14731 attempting to debug executables produced by them is most likely
14732 to give an error as @value{GDBN} reads in the executable's symbol
14735 @cindex expressions in Modula-2
14737 * M2 Operators:: Built-in operators
14738 * Built-In Func/Proc:: Built-in functions and procedures
14739 * M2 Constants:: Modula-2 constants
14740 * M2 Types:: Modula-2 types
14741 * M2 Defaults:: Default settings for Modula-2
14742 * Deviations:: Deviations from standard Modula-2
14743 * M2 Checks:: Modula-2 type and range checks
14744 * M2 Scope:: The scope operators @code{::} and @code{.}
14745 * GDB/M2:: @value{GDBN} and Modula-2
14749 @subsubsection Operators
14750 @cindex Modula-2 operators
14752 Operators must be defined on values of specific types. For instance,
14753 @code{+} is defined on numbers, but not on structures. Operators are
14754 often defined on groups of types. For the purposes of Modula-2, the
14755 following definitions hold:
14760 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
14764 @emph{Character types} consist of @code{CHAR} and its subranges.
14767 @emph{Floating-point types} consist of @code{REAL}.
14770 @emph{Pointer types} consist of anything declared as @code{POINTER TO
14774 @emph{Scalar types} consist of all of the above.
14777 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
14780 @emph{Boolean types} consist of @code{BOOLEAN}.
14784 The following operators are supported, and appear in order of
14785 increasing precedence:
14789 Function argument or array index separator.
14792 Assignment. The value of @var{var} @code{:=} @var{value} is
14796 Less than, greater than on integral, floating-point, or enumerated
14800 Less than or equal to, greater than or equal to
14801 on integral, floating-point and enumerated types, or set inclusion on
14802 set types. Same precedence as @code{<}.
14804 @item =@r{, }<>@r{, }#
14805 Equality and two ways of expressing inequality, valid on scalar types.
14806 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
14807 available for inequality, since @code{#} conflicts with the script
14811 Set membership. Defined on set types and the types of their members.
14812 Same precedence as @code{<}.
14815 Boolean disjunction. Defined on boolean types.
14818 Boolean conjunction. Defined on boolean types.
14821 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14824 Addition and subtraction on integral and floating-point types, or union
14825 and difference on set types.
14828 Multiplication on integral and floating-point types, or set intersection
14832 Division on floating-point types, or symmetric set difference on set
14833 types. Same precedence as @code{*}.
14836 Integer division and remainder. Defined on integral types. Same
14837 precedence as @code{*}.
14840 Negative. Defined on @code{INTEGER} and @code{REAL} data.
14843 Pointer dereferencing. Defined on pointer types.
14846 Boolean negation. Defined on boolean types. Same precedence as
14850 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
14851 precedence as @code{^}.
14854 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
14857 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
14861 @value{GDBN} and Modula-2 scope operators.
14865 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
14866 treats the use of the operator @code{IN}, or the use of operators
14867 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
14868 @code{<=}, and @code{>=} on sets as an error.
14872 @node Built-In Func/Proc
14873 @subsubsection Built-in Functions and Procedures
14874 @cindex Modula-2 built-ins
14876 Modula-2 also makes available several built-in procedures and functions.
14877 In describing these, the following metavariables are used:
14882 represents an @code{ARRAY} variable.
14885 represents a @code{CHAR} constant or variable.
14888 represents a variable or constant of integral type.
14891 represents an identifier that belongs to a set. Generally used in the
14892 same function with the metavariable @var{s}. The type of @var{s} should
14893 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
14896 represents a variable or constant of integral or floating-point type.
14899 represents a variable or constant of floating-point type.
14905 represents a variable.
14908 represents a variable or constant of one of many types. See the
14909 explanation of the function for details.
14912 All Modula-2 built-in procedures also return a result, described below.
14916 Returns the absolute value of @var{n}.
14919 If @var{c} is a lower case letter, it returns its upper case
14920 equivalent, otherwise it returns its argument.
14923 Returns the character whose ordinal value is @var{i}.
14926 Decrements the value in the variable @var{v} by one. Returns the new value.
14928 @item DEC(@var{v},@var{i})
14929 Decrements the value in the variable @var{v} by @var{i}. Returns the
14932 @item EXCL(@var{m},@var{s})
14933 Removes the element @var{m} from the set @var{s}. Returns the new
14936 @item FLOAT(@var{i})
14937 Returns the floating point equivalent of the integer @var{i}.
14939 @item HIGH(@var{a})
14940 Returns the index of the last member of @var{a}.
14943 Increments the value in the variable @var{v} by one. Returns the new value.
14945 @item INC(@var{v},@var{i})
14946 Increments the value in the variable @var{v} by @var{i}. Returns the
14949 @item INCL(@var{m},@var{s})
14950 Adds the element @var{m} to the set @var{s} if it is not already
14951 there. Returns the new set.
14954 Returns the maximum value of the type @var{t}.
14957 Returns the minimum value of the type @var{t}.
14960 Returns boolean TRUE if @var{i} is an odd number.
14963 Returns the ordinal value of its argument. For example, the ordinal
14964 value of a character is its @sc{ascii} value (on machines supporting
14965 the @sc{ascii} character set). The argument @var{x} must be of an
14966 ordered type, which include integral, character and enumerated types.
14968 @item SIZE(@var{x})
14969 Returns the size of its argument. The argument @var{x} can be a
14970 variable or a type.
14972 @item TRUNC(@var{r})
14973 Returns the integral part of @var{r}.
14975 @item TSIZE(@var{x})
14976 Returns the size of its argument. The argument @var{x} can be a
14977 variable or a type.
14979 @item VAL(@var{t},@var{i})
14980 Returns the member of the type @var{t} whose ordinal value is @var{i}.
14984 @emph{Warning:} Sets and their operations are not yet supported, so
14985 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
14989 @cindex Modula-2 constants
14991 @subsubsection Constants
14993 @value{GDBN} allows you to express the constants of Modula-2 in the following
14999 Integer constants are simply a sequence of digits. When used in an
15000 expression, a constant is interpreted to be type-compatible with the
15001 rest of the expression. Hexadecimal integers are specified by a
15002 trailing @samp{H}, and octal integers by a trailing @samp{B}.
15005 Floating point constants appear as a sequence of digits, followed by a
15006 decimal point and another sequence of digits. An optional exponent can
15007 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
15008 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
15009 digits of the floating point constant must be valid decimal (base 10)
15013 Character constants consist of a single character enclosed by a pair of
15014 like quotes, either single (@code{'}) or double (@code{"}). They may
15015 also be expressed by their ordinal value (their @sc{ascii} value, usually)
15016 followed by a @samp{C}.
15019 String constants consist of a sequence of characters enclosed by a
15020 pair of like quotes, either single (@code{'}) or double (@code{"}).
15021 Escape sequences in the style of C are also allowed. @xref{C
15022 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
15026 Enumerated constants consist of an enumerated identifier.
15029 Boolean constants consist of the identifiers @code{TRUE} and
15033 Pointer constants consist of integral values only.
15036 Set constants are not yet supported.
15040 @subsubsection Modula-2 Types
15041 @cindex Modula-2 types
15043 Currently @value{GDBN} can print the following data types in Modula-2
15044 syntax: array types, record types, set types, pointer types, procedure
15045 types, enumerated types, subrange types and base types. You can also
15046 print the contents of variables declared using these type.
15047 This section gives a number of simple source code examples together with
15048 sample @value{GDBN} sessions.
15050 The first example contains the following section of code:
15059 and you can request @value{GDBN} to interrogate the type and value of
15060 @code{r} and @code{s}.
15063 (@value{GDBP}) print s
15065 (@value{GDBP}) ptype s
15067 (@value{GDBP}) print r
15069 (@value{GDBP}) ptype r
15074 Likewise if your source code declares @code{s} as:
15078 s: SET ['A'..'Z'] ;
15082 then you may query the type of @code{s} by:
15085 (@value{GDBP}) ptype s
15086 type = SET ['A'..'Z']
15090 Note that at present you cannot interactively manipulate set
15091 expressions using the debugger.
15093 The following example shows how you might declare an array in Modula-2
15094 and how you can interact with @value{GDBN} to print its type and contents:
15098 s: ARRAY [-10..10] OF CHAR ;
15102 (@value{GDBP}) ptype s
15103 ARRAY [-10..10] OF CHAR
15106 Note that the array handling is not yet complete and although the type
15107 is printed correctly, expression handling still assumes that all
15108 arrays have a lower bound of zero and not @code{-10} as in the example
15111 Here are some more type related Modula-2 examples:
15115 colour = (blue, red, yellow, green) ;
15116 t = [blue..yellow] ;
15124 The @value{GDBN} interaction shows how you can query the data type
15125 and value of a variable.
15128 (@value{GDBP}) print s
15130 (@value{GDBP}) ptype t
15131 type = [blue..yellow]
15135 In this example a Modula-2 array is declared and its contents
15136 displayed. Observe that the contents are written in the same way as
15137 their @code{C} counterparts.
15141 s: ARRAY [1..5] OF CARDINAL ;
15147 (@value{GDBP}) print s
15148 $1 = @{1, 0, 0, 0, 0@}
15149 (@value{GDBP}) ptype s
15150 type = ARRAY [1..5] OF CARDINAL
15153 The Modula-2 language interface to @value{GDBN} also understands
15154 pointer types as shown in this example:
15158 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
15165 and you can request that @value{GDBN} describes the type of @code{s}.
15168 (@value{GDBP}) ptype s
15169 type = POINTER TO ARRAY [1..5] OF CARDINAL
15172 @value{GDBN} handles compound types as we can see in this example.
15173 Here we combine array types, record types, pointer types and subrange
15184 myarray = ARRAY myrange OF CARDINAL ;
15185 myrange = [-2..2] ;
15187 s: POINTER TO ARRAY myrange OF foo ;
15191 and you can ask @value{GDBN} to describe the type of @code{s} as shown
15195 (@value{GDBP}) ptype s
15196 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
15199 f3 : ARRAY [-2..2] OF CARDINAL;
15204 @subsubsection Modula-2 Defaults
15205 @cindex Modula-2 defaults
15207 If type and range checking are set automatically by @value{GDBN}, they
15208 both default to @code{on} whenever the working language changes to
15209 Modula-2. This happens regardless of whether you or @value{GDBN}
15210 selected the working language.
15212 If you allow @value{GDBN} to set the language automatically, then entering
15213 code compiled from a file whose name ends with @file{.mod} sets the
15214 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
15215 Infer the Source Language}, for further details.
15218 @subsubsection Deviations from Standard Modula-2
15219 @cindex Modula-2, deviations from
15221 A few changes have been made to make Modula-2 programs easier to debug.
15222 This is done primarily via loosening its type strictness:
15226 Unlike in standard Modula-2, pointer constants can be formed by
15227 integers. This allows you to modify pointer variables during
15228 debugging. (In standard Modula-2, the actual address contained in a
15229 pointer variable is hidden from you; it can only be modified
15230 through direct assignment to another pointer variable or expression that
15231 returned a pointer.)
15234 C escape sequences can be used in strings and characters to represent
15235 non-printable characters. @value{GDBN} prints out strings with these
15236 escape sequences embedded. Single non-printable characters are
15237 printed using the @samp{CHR(@var{nnn})} format.
15240 The assignment operator (@code{:=}) returns the value of its right-hand
15244 All built-in procedures both modify @emph{and} return their argument.
15248 @subsubsection Modula-2 Type and Range Checks
15249 @cindex Modula-2 checks
15252 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
15255 @c FIXME remove warning when type/range checks added
15257 @value{GDBN} considers two Modula-2 variables type equivalent if:
15261 They are of types that have been declared equivalent via a @code{TYPE
15262 @var{t1} = @var{t2}} statement
15265 They have been declared on the same line. (Note: This is true of the
15266 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
15269 As long as type checking is enabled, any attempt to combine variables
15270 whose types are not equivalent is an error.
15272 Range checking is done on all mathematical operations, assignment, array
15273 index bounds, and all built-in functions and procedures.
15276 @subsubsection The Scope Operators @code{::} and @code{.}
15278 @cindex @code{.}, Modula-2 scope operator
15279 @cindex colon, doubled as scope operator
15281 @vindex colon-colon@r{, in Modula-2}
15282 @c Info cannot handle :: but TeX can.
15285 @vindex ::@r{, in Modula-2}
15288 There are a few subtle differences between the Modula-2 scope operator
15289 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
15294 @var{module} . @var{id}
15295 @var{scope} :: @var{id}
15299 where @var{scope} is the name of a module or a procedure,
15300 @var{module} the name of a module, and @var{id} is any declared
15301 identifier within your program, except another module.
15303 Using the @code{::} operator makes @value{GDBN} search the scope
15304 specified by @var{scope} for the identifier @var{id}. If it is not
15305 found in the specified scope, then @value{GDBN} searches all scopes
15306 enclosing the one specified by @var{scope}.
15308 Using the @code{.} operator makes @value{GDBN} search the current scope for
15309 the identifier specified by @var{id} that was imported from the
15310 definition module specified by @var{module}. With this operator, it is
15311 an error if the identifier @var{id} was not imported from definition
15312 module @var{module}, or if @var{id} is not an identifier in
15316 @subsubsection @value{GDBN} and Modula-2
15318 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
15319 Five subcommands of @code{set print} and @code{show print} apply
15320 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
15321 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
15322 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
15323 analogue in Modula-2.
15325 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
15326 with any language, is not useful with Modula-2. Its
15327 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
15328 created in Modula-2 as they can in C or C@t{++}. However, because an
15329 address can be specified by an integral constant, the construct
15330 @samp{@{@var{type}@}@var{adrexp}} is still useful.
15332 @cindex @code{#} in Modula-2
15333 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
15334 interpreted as the beginning of a comment. Use @code{<>} instead.
15340 The extensions made to @value{GDBN} for Ada only support
15341 output from the @sc{gnu} Ada (GNAT) compiler.
15342 Other Ada compilers are not currently supported, and
15343 attempting to debug executables produced by them is most likely
15347 @cindex expressions in Ada
15349 * Ada Mode Intro:: General remarks on the Ada syntax
15350 and semantics supported by Ada mode
15352 * Omissions from Ada:: Restrictions on the Ada expression syntax.
15353 * Additions to Ada:: Extensions of the Ada expression syntax.
15354 * Stopping Before Main Program:: Debugging the program during elaboration.
15355 * Ada Exceptions:: Ada Exceptions
15356 * Ada Tasks:: Listing and setting breakpoints in tasks.
15357 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
15358 * Ravenscar Profile:: Tasking Support when using the Ravenscar
15360 * Ada Glitches:: Known peculiarities of Ada mode.
15363 @node Ada Mode Intro
15364 @subsubsection Introduction
15365 @cindex Ada mode, general
15367 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
15368 syntax, with some extensions.
15369 The philosophy behind the design of this subset is
15373 That @value{GDBN} should provide basic literals and access to operations for
15374 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
15375 leaving more sophisticated computations to subprograms written into the
15376 program (which therefore may be called from @value{GDBN}).
15379 That type safety and strict adherence to Ada language restrictions
15380 are not particularly important to the @value{GDBN} user.
15383 That brevity is important to the @value{GDBN} user.
15386 Thus, for brevity, the debugger acts as if all names declared in
15387 user-written packages are directly visible, even if they are not visible
15388 according to Ada rules, thus making it unnecessary to fully qualify most
15389 names with their packages, regardless of context. Where this causes
15390 ambiguity, @value{GDBN} asks the user's intent.
15392 The debugger will start in Ada mode if it detects an Ada main program.
15393 As for other languages, it will enter Ada mode when stopped in a program that
15394 was translated from an Ada source file.
15396 While in Ada mode, you may use `@t{--}' for comments. This is useful
15397 mostly for documenting command files. The standard @value{GDBN} comment
15398 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
15399 middle (to allow based literals).
15401 The debugger supports limited overloading. Given a subprogram call in which
15402 the function symbol has multiple definitions, it will use the number of
15403 actual parameters and some information about their types to attempt to narrow
15404 the set of definitions. It also makes very limited use of context, preferring
15405 procedures to functions in the context of the @code{call} command, and
15406 functions to procedures elsewhere.
15408 @node Omissions from Ada
15409 @subsubsection Omissions from Ada
15410 @cindex Ada, omissions from
15412 Here are the notable omissions from the subset:
15416 Only a subset of the attributes are supported:
15420 @t{'First}, @t{'Last}, and @t{'Length}
15421 on array objects (not on types and subtypes).
15424 @t{'Min} and @t{'Max}.
15427 @t{'Pos} and @t{'Val}.
15433 @t{'Range} on array objects (not subtypes), but only as the right
15434 operand of the membership (@code{in}) operator.
15437 @t{'Access}, @t{'Unchecked_Access}, and
15438 @t{'Unrestricted_Access} (a GNAT extension).
15446 @code{Characters.Latin_1} are not available and
15447 concatenation is not implemented. Thus, escape characters in strings are
15448 not currently available.
15451 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
15452 equality of representations. They will generally work correctly
15453 for strings and arrays whose elements have integer or enumeration types.
15454 They may not work correctly for arrays whose element
15455 types have user-defined equality, for arrays of real values
15456 (in particular, IEEE-conformant floating point, because of negative
15457 zeroes and NaNs), and for arrays whose elements contain unused bits with
15458 indeterminate values.
15461 The other component-by-component array operations (@code{and}, @code{or},
15462 @code{xor}, @code{not}, and relational tests other than equality)
15463 are not implemented.
15466 @cindex array aggregates (Ada)
15467 @cindex record aggregates (Ada)
15468 @cindex aggregates (Ada)
15469 There is limited support for array and record aggregates. They are
15470 permitted only on the right sides of assignments, as in these examples:
15473 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
15474 (@value{GDBP}) set An_Array := (1, others => 0)
15475 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
15476 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
15477 (@value{GDBP}) set A_Record := (1, "Peter", True);
15478 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
15482 discriminant's value by assigning an aggregate has an
15483 undefined effect if that discriminant is used within the record.
15484 However, you can first modify discriminants by directly assigning to
15485 them (which normally would not be allowed in Ada), and then performing an
15486 aggregate assignment. For example, given a variable @code{A_Rec}
15487 declared to have a type such as:
15490 type Rec (Len : Small_Integer := 0) is record
15492 Vals : IntArray (1 .. Len);
15496 you can assign a value with a different size of @code{Vals} with two
15500 (@value{GDBP}) set A_Rec.Len := 4
15501 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
15504 As this example also illustrates, @value{GDBN} is very loose about the usual
15505 rules concerning aggregates. You may leave out some of the
15506 components of an array or record aggregate (such as the @code{Len}
15507 component in the assignment to @code{A_Rec} above); they will retain their
15508 original values upon assignment. You may freely use dynamic values as
15509 indices in component associations. You may even use overlapping or
15510 redundant component associations, although which component values are
15511 assigned in such cases is not defined.
15514 Calls to dispatching subprograms are not implemented.
15517 The overloading algorithm is much more limited (i.e., less selective)
15518 than that of real Ada. It makes only limited use of the context in
15519 which a subexpression appears to resolve its meaning, and it is much
15520 looser in its rules for allowing type matches. As a result, some
15521 function calls will be ambiguous, and the user will be asked to choose
15522 the proper resolution.
15525 The @code{new} operator is not implemented.
15528 Entry calls are not implemented.
15531 Aside from printing, arithmetic operations on the native VAX floating-point
15532 formats are not supported.
15535 It is not possible to slice a packed array.
15538 The names @code{True} and @code{False}, when not part of a qualified name,
15539 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
15541 Should your program
15542 redefine these names in a package or procedure (at best a dubious practice),
15543 you will have to use fully qualified names to access their new definitions.
15546 @node Additions to Ada
15547 @subsubsection Additions to Ada
15548 @cindex Ada, deviations from
15550 As it does for other languages, @value{GDBN} makes certain generic
15551 extensions to Ada (@pxref{Expressions}):
15555 If the expression @var{E} is a variable residing in memory (typically
15556 a local variable or array element) and @var{N} is a positive integer,
15557 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
15558 @var{N}-1 adjacent variables following it in memory as an array. In
15559 Ada, this operator is generally not necessary, since its prime use is
15560 in displaying parts of an array, and slicing will usually do this in
15561 Ada. However, there are occasional uses when debugging programs in
15562 which certain debugging information has been optimized away.
15565 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
15566 appears in function or file @var{B}.'' When @var{B} is a file name,
15567 you must typically surround it in single quotes.
15570 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
15571 @var{type} that appears at address @var{addr}.''
15574 A name starting with @samp{$} is a convenience variable
15575 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
15578 In addition, @value{GDBN} provides a few other shortcuts and outright
15579 additions specific to Ada:
15583 The assignment statement is allowed as an expression, returning
15584 its right-hand operand as its value. Thus, you may enter
15587 (@value{GDBP}) set x := y + 3
15588 (@value{GDBP}) print A(tmp := y + 1)
15592 The semicolon is allowed as an ``operator,'' returning as its value
15593 the value of its right-hand operand.
15594 This allows, for example,
15595 complex conditional breaks:
15598 (@value{GDBP}) break f
15599 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
15603 Rather than use catenation and symbolic character names to introduce special
15604 characters into strings, one may instead use a special bracket notation,
15605 which is also used to print strings. A sequence of characters of the form
15606 @samp{["@var{XX}"]} within a string or character literal denotes the
15607 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
15608 sequence of characters @samp{["""]} also denotes a single quotation mark
15609 in strings. For example,
15611 "One line.["0a"]Next line.["0a"]"
15614 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
15618 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
15619 @t{'Max} is optional (and is ignored in any case). For example, it is valid
15623 (@value{GDBP}) print 'max(x, y)
15627 When printing arrays, @value{GDBN} uses positional notation when the
15628 array has a lower bound of 1, and uses a modified named notation otherwise.
15629 For example, a one-dimensional array of three integers with a lower bound
15630 of 3 might print as
15637 That is, in contrast to valid Ada, only the first component has a @code{=>}
15641 You may abbreviate attributes in expressions with any unique,
15642 multi-character subsequence of
15643 their names (an exact match gets preference).
15644 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
15645 in place of @t{a'length}.
15648 @cindex quoting Ada internal identifiers
15649 Since Ada is case-insensitive, the debugger normally maps identifiers you type
15650 to lower case. The GNAT compiler uses upper-case characters for
15651 some of its internal identifiers, which are normally of no interest to users.
15652 For the rare occasions when you actually have to look at them,
15653 enclose them in angle brackets to avoid the lower-case mapping.
15656 (@value{GDBP}) print <JMPBUF_SAVE>[0]
15660 Printing an object of class-wide type or dereferencing an
15661 access-to-class-wide value will display all the components of the object's
15662 specific type (as indicated by its run-time tag). Likewise, component
15663 selection on such a value will operate on the specific type of the
15668 @node Stopping Before Main Program
15669 @subsubsection Stopping at the Very Beginning
15671 @cindex breakpointing Ada elaboration code
15672 It is sometimes necessary to debug the program during elaboration, and
15673 before reaching the main procedure.
15674 As defined in the Ada Reference
15675 Manual, the elaboration code is invoked from a procedure called
15676 @code{adainit}. To run your program up to the beginning of
15677 elaboration, simply use the following two commands:
15678 @code{tbreak adainit} and @code{run}.
15680 @node Ada Exceptions
15681 @subsubsection Ada Exceptions
15683 A command is provided to list all Ada exceptions:
15686 @kindex info exceptions
15687 @item info exceptions
15688 @itemx info exceptions @var{regexp}
15689 The @code{info exceptions} command allows you to list all Ada exceptions
15690 defined within the program being debugged, as well as their addresses.
15691 With a regular expression, @var{regexp}, as argument, only those exceptions
15692 whose names match @var{regexp} are listed.
15695 Below is a small example, showing how the command can be used, first
15696 without argument, and next with a regular expression passed as an
15700 (@value{GDBP}) info exceptions
15701 All defined Ada exceptions:
15702 constraint_error: 0x613da0
15703 program_error: 0x613d20
15704 storage_error: 0x613ce0
15705 tasking_error: 0x613ca0
15706 const.aint_global_e: 0x613b00
15707 (@value{GDBP}) info exceptions const.aint
15708 All Ada exceptions matching regular expression "const.aint":
15709 constraint_error: 0x613da0
15710 const.aint_global_e: 0x613b00
15713 It is also possible to ask @value{GDBN} to stop your program's execution
15714 when an exception is raised. For more details, see @ref{Set Catchpoints}.
15717 @subsubsection Extensions for Ada Tasks
15718 @cindex Ada, tasking
15720 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
15721 @value{GDBN} provides the following task-related commands:
15726 This command shows a list of current Ada tasks, as in the following example:
15733 (@value{GDBP}) info tasks
15734 ID TID P-ID Pri State Name
15735 1 8088000 0 15 Child Activation Wait main_task
15736 2 80a4000 1 15 Accept Statement b
15737 3 809a800 1 15 Child Activation Wait a
15738 * 4 80ae800 3 15 Runnable c
15743 In this listing, the asterisk before the last task indicates it to be the
15744 task currently being inspected.
15748 Represents @value{GDBN}'s internal task number.
15754 The parent's task ID (@value{GDBN}'s internal task number).
15757 The base priority of the task.
15760 Current state of the task.
15764 The task has been created but has not been activated. It cannot be
15768 The task is not blocked for any reason known to Ada. (It may be waiting
15769 for a mutex, though.) It is conceptually "executing" in normal mode.
15772 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
15773 that were waiting on terminate alternatives have been awakened and have
15774 terminated themselves.
15776 @item Child Activation Wait
15777 The task is waiting for created tasks to complete activation.
15779 @item Accept Statement
15780 The task is waiting on an accept or selective wait statement.
15782 @item Waiting on entry call
15783 The task is waiting on an entry call.
15785 @item Async Select Wait
15786 The task is waiting to start the abortable part of an asynchronous
15790 The task is waiting on a select statement with only a delay
15793 @item Child Termination Wait
15794 The task is sleeping having completed a master within itself, and is
15795 waiting for the tasks dependent on that master to become terminated or
15796 waiting on a terminate Phase.
15798 @item Wait Child in Term Alt
15799 The task is sleeping waiting for tasks on terminate alternatives to
15800 finish terminating.
15802 @item Accepting RV with @var{taskno}
15803 The task is accepting a rendez-vous with the task @var{taskno}.
15807 Name of the task in the program.
15811 @kindex info task @var{taskno}
15812 @item info task @var{taskno}
15813 This command shows detailled informations on the specified task, as in
15814 the following example:
15819 (@value{GDBP}) info tasks
15820 ID TID P-ID Pri State Name
15821 1 8077880 0 15 Child Activation Wait main_task
15822 * 2 807c468 1 15 Runnable task_1
15823 (@value{GDBP}) info task 2
15824 Ada Task: 0x807c468
15827 Parent: 1 (main_task)
15833 @kindex task@r{ (Ada)}
15834 @cindex current Ada task ID
15835 This command prints the ID of the current task.
15841 (@value{GDBP}) info tasks
15842 ID TID P-ID Pri State Name
15843 1 8077870 0 15 Child Activation Wait main_task
15844 * 2 807c458 1 15 Runnable t
15845 (@value{GDBP}) task
15846 [Current task is 2]
15849 @item task @var{taskno}
15850 @cindex Ada task switching
15851 This command is like the @code{thread @var{threadno}}
15852 command (@pxref{Threads}). It switches the context of debugging
15853 from the current task to the given task.
15859 (@value{GDBP}) info tasks
15860 ID TID P-ID Pri State Name
15861 1 8077870 0 15 Child Activation Wait main_task
15862 * 2 807c458 1 15 Runnable t
15863 (@value{GDBP}) task 1
15864 [Switching to task 1]
15865 #0 0x8067726 in pthread_cond_wait ()
15867 #0 0x8067726 in pthread_cond_wait ()
15868 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
15869 #2 0x805cb63 in system.task_primitives.operations.sleep ()
15870 #3 0x806153e in system.tasking.stages.activate_tasks ()
15871 #4 0x804aacc in un () at un.adb:5
15874 @item break @var{linespec} task @var{taskno}
15875 @itemx break @var{linespec} task @var{taskno} if @dots{}
15876 @cindex breakpoints and tasks, in Ada
15877 @cindex task breakpoints, in Ada
15878 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
15879 These commands are like the @code{break @dots{} thread @dots{}}
15880 command (@pxref{Thread Stops}). The
15881 @var{linespec} argument specifies source lines, as described
15882 in @ref{Specify Location}.
15884 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
15885 to specify that you only want @value{GDBN} to stop the program when a
15886 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
15887 numeric task identifiers assigned by @value{GDBN}, shown in the first
15888 column of the @samp{info tasks} display.
15890 If you do not specify @samp{task @var{taskno}} when you set a
15891 breakpoint, the breakpoint applies to @emph{all} tasks of your
15894 You can use the @code{task} qualifier on conditional breakpoints as
15895 well; in this case, place @samp{task @var{taskno}} before the
15896 breakpoint condition (before the @code{if}).
15904 (@value{GDBP}) info tasks
15905 ID TID P-ID Pri State Name
15906 1 140022020 0 15 Child Activation Wait main_task
15907 2 140045060 1 15 Accept/Select Wait t2
15908 3 140044840 1 15 Runnable t1
15909 * 4 140056040 1 15 Runnable t3
15910 (@value{GDBP}) b 15 task 2
15911 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
15912 (@value{GDBP}) cont
15917 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
15919 (@value{GDBP}) info tasks
15920 ID TID P-ID Pri State Name
15921 1 140022020 0 15 Child Activation Wait main_task
15922 * 2 140045060 1 15 Runnable t2
15923 3 140044840 1 15 Runnable t1
15924 4 140056040 1 15 Delay Sleep t3
15928 @node Ada Tasks and Core Files
15929 @subsubsection Tasking Support when Debugging Core Files
15930 @cindex Ada tasking and core file debugging
15932 When inspecting a core file, as opposed to debugging a live program,
15933 tasking support may be limited or even unavailable, depending on
15934 the platform being used.
15935 For instance, on x86-linux, the list of tasks is available, but task
15936 switching is not supported.
15938 On certain platforms, the debugger needs to perform some
15939 memory writes in order to provide Ada tasking support. When inspecting
15940 a core file, this means that the core file must be opened with read-write
15941 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
15942 Under these circumstances, you should make a backup copy of the core
15943 file before inspecting it with @value{GDBN}.
15945 @node Ravenscar Profile
15946 @subsubsection Tasking Support when using the Ravenscar Profile
15947 @cindex Ravenscar Profile
15949 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
15950 specifically designed for systems with safety-critical real-time
15954 @kindex set ravenscar task-switching on
15955 @cindex task switching with program using Ravenscar Profile
15956 @item set ravenscar task-switching on
15957 Allows task switching when debugging a program that uses the Ravenscar
15958 Profile. This is the default.
15960 @kindex set ravenscar task-switching off
15961 @item set ravenscar task-switching off
15962 Turn off task switching when debugging a program that uses the Ravenscar
15963 Profile. This is mostly intended to disable the code that adds support
15964 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
15965 the Ravenscar runtime is preventing @value{GDBN} from working properly.
15966 To be effective, this command should be run before the program is started.
15968 @kindex show ravenscar task-switching
15969 @item show ravenscar task-switching
15970 Show whether it is possible to switch from task to task in a program
15971 using the Ravenscar Profile.
15976 @subsubsection Known Peculiarities of Ada Mode
15977 @cindex Ada, problems
15979 Besides the omissions listed previously (@pxref{Omissions from Ada}),
15980 we know of several problems with and limitations of Ada mode in
15982 some of which will be fixed with planned future releases of the debugger
15983 and the GNU Ada compiler.
15987 Static constants that the compiler chooses not to materialize as objects in
15988 storage are invisible to the debugger.
15991 Named parameter associations in function argument lists are ignored (the
15992 argument lists are treated as positional).
15995 Many useful library packages are currently invisible to the debugger.
15998 Fixed-point arithmetic, conversions, input, and output is carried out using
15999 floating-point arithmetic, and may give results that only approximate those on
16003 The GNAT compiler never generates the prefix @code{Standard} for any of
16004 the standard symbols defined by the Ada language. @value{GDBN} knows about
16005 this: it will strip the prefix from names when you use it, and will never
16006 look for a name you have so qualified among local symbols, nor match against
16007 symbols in other packages or subprograms. If you have
16008 defined entities anywhere in your program other than parameters and
16009 local variables whose simple names match names in @code{Standard},
16010 GNAT's lack of qualification here can cause confusion. When this happens,
16011 you can usually resolve the confusion
16012 by qualifying the problematic names with package
16013 @code{Standard} explicitly.
16016 Older versions of the compiler sometimes generate erroneous debugging
16017 information, resulting in the debugger incorrectly printing the value
16018 of affected entities. In some cases, the debugger is able to work
16019 around an issue automatically. In other cases, the debugger is able
16020 to work around the issue, but the work-around has to be specifically
16023 @kindex set ada trust-PAD-over-XVS
16024 @kindex show ada trust-PAD-over-XVS
16027 @item set ada trust-PAD-over-XVS on
16028 Configure GDB to strictly follow the GNAT encoding when computing the
16029 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
16030 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
16031 a complete description of the encoding used by the GNAT compiler).
16032 This is the default.
16034 @item set ada trust-PAD-over-XVS off
16035 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
16036 sometimes prints the wrong value for certain entities, changing @code{ada
16037 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
16038 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
16039 @code{off}, but this incurs a slight performance penalty, so it is
16040 recommended to leave this setting to @code{on} unless necessary.
16044 @cindex GNAT descriptive types
16045 @cindex GNAT encoding
16046 Internally, the debugger also relies on the compiler following a number
16047 of conventions known as the @samp{GNAT Encoding}, all documented in
16048 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
16049 how the debugging information should be generated for certain types.
16050 In particular, this convention makes use of @dfn{descriptive types},
16051 which are artificial types generated purely to help the debugger.
16053 These encodings were defined at a time when the debugging information
16054 format used was not powerful enough to describe some of the more complex
16055 types available in Ada. Since DWARF allows us to express nearly all
16056 Ada features, the long-term goal is to slowly replace these descriptive
16057 types by their pure DWARF equivalent. To facilitate that transition,
16058 a new maintenance option is available to force the debugger to ignore
16059 those descriptive types. It allows the user to quickly evaluate how
16060 well @value{GDBN} works without them.
16064 @kindex maint ada set ignore-descriptive-types
16065 @item maintenance ada set ignore-descriptive-types [on|off]
16066 Control whether the debugger should ignore descriptive types.
16067 The default is not to ignore descriptives types (@code{off}).
16069 @kindex maint ada show ignore-descriptive-types
16070 @item maintenance ada show ignore-descriptive-types
16071 Show if descriptive types are ignored by @value{GDBN}.
16075 @node Unsupported Languages
16076 @section Unsupported Languages
16078 @cindex unsupported languages
16079 @cindex minimal language
16080 In addition to the other fully-supported programming languages,
16081 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
16082 It does not represent a real programming language, but provides a set
16083 of capabilities close to what the C or assembly languages provide.
16084 This should allow most simple operations to be performed while debugging
16085 an application that uses a language currently not supported by @value{GDBN}.
16087 If the language is set to @code{auto}, @value{GDBN} will automatically
16088 select this language if the current frame corresponds to an unsupported
16092 @chapter Examining the Symbol Table
16094 The commands described in this chapter allow you to inquire about the
16095 symbols (names of variables, functions and types) defined in your
16096 program. This information is inherent in the text of your program and
16097 does not change as your program executes. @value{GDBN} finds it in your
16098 program's symbol table, in the file indicated when you started @value{GDBN}
16099 (@pxref{File Options, ,Choosing Files}), or by one of the
16100 file-management commands (@pxref{Files, ,Commands to Specify Files}).
16102 @cindex symbol names
16103 @cindex names of symbols
16104 @cindex quoting names
16105 Occasionally, you may need to refer to symbols that contain unusual
16106 characters, which @value{GDBN} ordinarily treats as word delimiters. The
16107 most frequent case is in referring to static variables in other
16108 source files (@pxref{Variables,,Program Variables}). File names
16109 are recorded in object files as debugging symbols, but @value{GDBN} would
16110 ordinarily parse a typical file name, like @file{foo.c}, as the three words
16111 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
16112 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
16119 looks up the value of @code{x} in the scope of the file @file{foo.c}.
16122 @cindex case-insensitive symbol names
16123 @cindex case sensitivity in symbol names
16124 @kindex set case-sensitive
16125 @item set case-sensitive on
16126 @itemx set case-sensitive off
16127 @itemx set case-sensitive auto
16128 Normally, when @value{GDBN} looks up symbols, it matches their names
16129 with case sensitivity determined by the current source language.
16130 Occasionally, you may wish to control that. The command @code{set
16131 case-sensitive} lets you do that by specifying @code{on} for
16132 case-sensitive matches or @code{off} for case-insensitive ones. If
16133 you specify @code{auto}, case sensitivity is reset to the default
16134 suitable for the source language. The default is case-sensitive
16135 matches for all languages except for Fortran, for which the default is
16136 case-insensitive matches.
16138 @kindex show case-sensitive
16139 @item show case-sensitive
16140 This command shows the current setting of case sensitivity for symbols
16143 @kindex set print type methods
16144 @item set print type methods
16145 @itemx set print type methods on
16146 @itemx set print type methods off
16147 Normally, when @value{GDBN} prints a class, it displays any methods
16148 declared in that class. You can control this behavior either by
16149 passing the appropriate flag to @code{ptype}, or using @command{set
16150 print type methods}. Specifying @code{on} will cause @value{GDBN} to
16151 display the methods; this is the default. Specifying @code{off} will
16152 cause @value{GDBN} to omit the methods.
16154 @kindex show print type methods
16155 @item show print type methods
16156 This command shows the current setting of method display when printing
16159 @kindex set print type typedefs
16160 @item set print type typedefs
16161 @itemx set print type typedefs on
16162 @itemx set print type typedefs off
16164 Normally, when @value{GDBN} prints a class, it displays any typedefs
16165 defined in that class. You can control this behavior either by
16166 passing the appropriate flag to @code{ptype}, or using @command{set
16167 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
16168 display the typedef definitions; this is the default. Specifying
16169 @code{off} will cause @value{GDBN} to omit the typedef definitions.
16170 Note that this controls whether the typedef definition itself is
16171 printed, not whether typedef names are substituted when printing other
16174 @kindex show print type typedefs
16175 @item show print type typedefs
16176 This command shows the current setting of typedef display when
16179 @kindex info address
16180 @cindex address of a symbol
16181 @item info address @var{symbol}
16182 Describe where the data for @var{symbol} is stored. For a register
16183 variable, this says which register it is kept in. For a non-register
16184 local variable, this prints the stack-frame offset at which the variable
16187 Note the contrast with @samp{print &@var{symbol}}, which does not work
16188 at all for a register variable, and for a stack local variable prints
16189 the exact address of the current instantiation of the variable.
16191 @kindex info symbol
16192 @cindex symbol from address
16193 @cindex closest symbol and offset for an address
16194 @item info symbol @var{addr}
16195 Print the name of a symbol which is stored at the address @var{addr}.
16196 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
16197 nearest symbol and an offset from it:
16200 (@value{GDBP}) info symbol 0x54320
16201 _initialize_vx + 396 in section .text
16205 This is the opposite of the @code{info address} command. You can use
16206 it to find out the name of a variable or a function given its address.
16208 For dynamically linked executables, the name of executable or shared
16209 library containing the symbol is also printed:
16212 (@value{GDBP}) info symbol 0x400225
16213 _start + 5 in section .text of /tmp/a.out
16214 (@value{GDBP}) info symbol 0x2aaaac2811cf
16215 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
16220 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
16221 Demangle @var{name}.
16222 If @var{language} is provided it is the name of the language to demangle
16223 @var{name} in. Otherwise @var{name} is demangled in the current language.
16225 The @samp{--} option specifies the end of options,
16226 and is useful when @var{name} begins with a dash.
16228 The parameter @code{demangle-style} specifies how to interpret the kind
16229 of mangling used. @xref{Print Settings}.
16232 @item whatis[/@var{flags}] [@var{arg}]
16233 Print the data type of @var{arg}, which can be either an expression
16234 or a name of a data type. With no argument, print the data type of
16235 @code{$}, the last value in the value history.
16237 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
16238 is not actually evaluated, and any side-effecting operations (such as
16239 assignments or function calls) inside it do not take place.
16241 If @var{arg} is a variable or an expression, @code{whatis} prints its
16242 literal type as it is used in the source code. If the type was
16243 defined using a @code{typedef}, @code{whatis} will @emph{not} print
16244 the data type underlying the @code{typedef}. If the type of the
16245 variable or the expression is a compound data type, such as
16246 @code{struct} or @code{class}, @code{whatis} never prints their
16247 fields or methods. It just prints the @code{struct}/@code{class}
16248 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
16249 such a compound data type, use @code{ptype}.
16251 If @var{arg} is a type name that was defined using @code{typedef},
16252 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
16253 Unrolling means that @code{whatis} will show the underlying type used
16254 in the @code{typedef} declaration of @var{arg}. However, if that
16255 underlying type is also a @code{typedef}, @code{whatis} will not
16258 For C code, the type names may also have the form @samp{class
16259 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
16260 @var{union-tag}} or @samp{enum @var{enum-tag}}.
16262 @var{flags} can be used to modify how the type is displayed.
16263 Available flags are:
16267 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
16268 parameters and typedefs defined in a class when printing the class'
16269 members. The @code{/r} flag disables this.
16272 Do not print methods defined in the class.
16275 Print methods defined in the class. This is the default, but the flag
16276 exists in case you change the default with @command{set print type methods}.
16279 Do not print typedefs defined in the class. Note that this controls
16280 whether the typedef definition itself is printed, not whether typedef
16281 names are substituted when printing other types.
16284 Print typedefs defined in the class. This is the default, but the flag
16285 exists in case you change the default with @command{set print type typedefs}.
16289 @item ptype[/@var{flags}] [@var{arg}]
16290 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
16291 detailed description of the type, instead of just the name of the type.
16292 @xref{Expressions, ,Expressions}.
16294 Contrary to @code{whatis}, @code{ptype} always unrolls any
16295 @code{typedef}s in its argument declaration, whether the argument is
16296 a variable, expression, or a data type. This means that @code{ptype}
16297 of a variable or an expression will not print literally its type as
16298 present in the source code---use @code{whatis} for that. @code{typedef}s at
16299 the pointer or reference targets are also unrolled. Only @code{typedef}s of
16300 fields, methods and inner @code{class typedef}s of @code{struct}s,
16301 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
16303 For example, for this variable declaration:
16306 typedef double real_t;
16307 struct complex @{ real_t real; double imag; @};
16308 typedef struct complex complex_t;
16310 real_t *real_pointer_var;
16314 the two commands give this output:
16318 (@value{GDBP}) whatis var
16320 (@value{GDBP}) ptype var
16321 type = struct complex @{
16325 (@value{GDBP}) whatis complex_t
16326 type = struct complex
16327 (@value{GDBP}) whatis struct complex
16328 type = struct complex
16329 (@value{GDBP}) ptype struct complex
16330 type = struct complex @{
16334 (@value{GDBP}) whatis real_pointer_var
16336 (@value{GDBP}) ptype real_pointer_var
16342 As with @code{whatis}, using @code{ptype} without an argument refers to
16343 the type of @code{$}, the last value in the value history.
16345 @cindex incomplete type
16346 Sometimes, programs use opaque data types or incomplete specifications
16347 of complex data structure. If the debug information included in the
16348 program does not allow @value{GDBN} to display a full declaration of
16349 the data type, it will say @samp{<incomplete type>}. For example,
16350 given these declarations:
16354 struct foo *fooptr;
16358 but no definition for @code{struct foo} itself, @value{GDBN} will say:
16361 (@value{GDBP}) ptype foo
16362 $1 = <incomplete type>
16366 ``Incomplete type'' is C terminology for data types that are not
16367 completely specified.
16370 @item info types @var{regexp}
16372 Print a brief description of all types whose names match the regular
16373 expression @var{regexp} (or all types in your program, if you supply
16374 no argument). Each complete typename is matched as though it were a
16375 complete line; thus, @samp{i type value} gives information on all
16376 types in your program whose names include the string @code{value}, but
16377 @samp{i type ^value$} gives information only on types whose complete
16378 name is @code{value}.
16380 This command differs from @code{ptype} in two ways: first, like
16381 @code{whatis}, it does not print a detailed description; second, it
16382 lists all source files where a type is defined.
16384 @kindex info type-printers
16385 @item info type-printers
16386 Versions of @value{GDBN} that ship with Python scripting enabled may
16387 have ``type printers'' available. When using @command{ptype} or
16388 @command{whatis}, these printers are consulted when the name of a type
16389 is needed. @xref{Type Printing API}, for more information on writing
16392 @code{info type-printers} displays all the available type printers.
16394 @kindex enable type-printer
16395 @kindex disable type-printer
16396 @item enable type-printer @var{name}@dots{}
16397 @item disable type-printer @var{name}@dots{}
16398 These commands can be used to enable or disable type printers.
16401 @cindex local variables
16402 @item info scope @var{location}
16403 List all the variables local to a particular scope. This command
16404 accepts a @var{location} argument---a function name, a source line, or
16405 an address preceded by a @samp{*}, and prints all the variables local
16406 to the scope defined by that location. (@xref{Specify Location}, for
16407 details about supported forms of @var{location}.) For example:
16410 (@value{GDBP}) @b{info scope command_line_handler}
16411 Scope for command_line_handler:
16412 Symbol rl is an argument at stack/frame offset 8, length 4.
16413 Symbol linebuffer is in static storage at address 0x150a18, length 4.
16414 Symbol linelength is in static storage at address 0x150a1c, length 4.
16415 Symbol p is a local variable in register $esi, length 4.
16416 Symbol p1 is a local variable in register $ebx, length 4.
16417 Symbol nline is a local variable in register $edx, length 4.
16418 Symbol repeat is a local variable at frame offset -8, length 4.
16422 This command is especially useful for determining what data to collect
16423 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
16426 @kindex info source
16428 Show information about the current source file---that is, the source file for
16429 the function containing the current point of execution:
16432 the name of the source file, and the directory containing it,
16434 the directory it was compiled in,
16436 its length, in lines,
16438 which programming language it is written in,
16440 if the debug information provides it, the program that compiled the file
16441 (which may include, e.g., the compiler version and command line arguments),
16443 whether the executable includes debugging information for that file, and
16444 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
16446 whether the debugging information includes information about
16447 preprocessor macros.
16451 @kindex info sources
16453 Print the names of all source files in your program for which there is
16454 debugging information, organized into two lists: files whose symbols
16455 have already been read, and files whose symbols will be read when needed.
16457 @kindex info functions
16458 @item info functions
16459 Print the names and data types of all defined functions.
16461 @item info functions @var{regexp}
16462 Print the names and data types of all defined functions
16463 whose names contain a match for regular expression @var{regexp}.
16464 Thus, @samp{info fun step} finds all functions whose names
16465 include @code{step}; @samp{info fun ^step} finds those whose names
16466 start with @code{step}. If a function name contains characters
16467 that conflict with the regular expression language (e.g.@:
16468 @samp{operator*()}), they may be quoted with a backslash.
16470 @kindex info variables
16471 @item info variables
16472 Print the names and data types of all variables that are defined
16473 outside of functions (i.e.@: excluding local variables).
16475 @item info variables @var{regexp}
16476 Print the names and data types of all variables (except for local
16477 variables) whose names contain a match for regular expression
16480 @kindex info classes
16481 @cindex Objective-C, classes and selectors
16483 @itemx info classes @var{regexp}
16484 Display all Objective-C classes in your program, or
16485 (with the @var{regexp} argument) all those matching a particular regular
16488 @kindex info selectors
16489 @item info selectors
16490 @itemx info selectors @var{regexp}
16491 Display all Objective-C selectors in your program, or
16492 (with the @var{regexp} argument) all those matching a particular regular
16496 This was never implemented.
16497 @kindex info methods
16499 @itemx info methods @var{regexp}
16500 The @code{info methods} command permits the user to examine all defined
16501 methods within C@t{++} program, or (with the @var{regexp} argument) a
16502 specific set of methods found in the various C@t{++} classes. Many
16503 C@t{++} classes provide a large number of methods. Thus, the output
16504 from the @code{ptype} command can be overwhelming and hard to use. The
16505 @code{info-methods} command filters the methods, printing only those
16506 which match the regular-expression @var{regexp}.
16509 @cindex opaque data types
16510 @kindex set opaque-type-resolution
16511 @item set opaque-type-resolution on
16512 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
16513 declared as a pointer to a @code{struct}, @code{class}, or
16514 @code{union}---for example, @code{struct MyType *}---that is used in one
16515 source file although the full declaration of @code{struct MyType} is in
16516 another source file. The default is on.
16518 A change in the setting of this subcommand will not take effect until
16519 the next time symbols for a file are loaded.
16521 @item set opaque-type-resolution off
16522 Tell @value{GDBN} not to resolve opaque types. In this case, the type
16523 is printed as follows:
16525 @{<no data fields>@}
16528 @kindex show opaque-type-resolution
16529 @item show opaque-type-resolution
16530 Show whether opaque types are resolved or not.
16532 @kindex set print symbol-loading
16533 @cindex print messages when symbols are loaded
16534 @item set print symbol-loading
16535 @itemx set print symbol-loading full
16536 @itemx set print symbol-loading brief
16537 @itemx set print symbol-loading off
16538 The @code{set print symbol-loading} command allows you to control the
16539 printing of messages when @value{GDBN} loads symbol information.
16540 By default a message is printed for the executable and one for each
16541 shared library, and normally this is what you want. However, when
16542 debugging apps with large numbers of shared libraries these messages
16544 When set to @code{brief} a message is printed for each executable,
16545 and when @value{GDBN} loads a collection of shared libraries at once
16546 it will only print one message regardless of the number of shared
16547 libraries. When set to @code{off} no messages are printed.
16549 @kindex show print symbol-loading
16550 @item show print symbol-loading
16551 Show whether messages will be printed when a @value{GDBN} command
16552 entered from the keyboard causes symbol information to be loaded.
16554 @kindex maint print symbols
16555 @cindex symbol dump
16556 @kindex maint print psymbols
16557 @cindex partial symbol dump
16558 @kindex maint print msymbols
16559 @cindex minimal symbol dump
16560 @item maint print symbols @var{filename}
16561 @itemx maint print psymbols @var{filename}
16562 @itemx maint print msymbols @var{filename}
16563 Write a dump of debugging symbol data into the file @var{filename}.
16564 These commands are used to debug the @value{GDBN} symbol-reading code. Only
16565 symbols with debugging data are included. If you use @samp{maint print
16566 symbols}, @value{GDBN} includes all the symbols for which it has already
16567 collected full details: that is, @var{filename} reflects symbols for
16568 only those files whose symbols @value{GDBN} has read. You can use the
16569 command @code{info sources} to find out which files these are. If you
16570 use @samp{maint print psymbols} instead, the dump shows information about
16571 symbols that @value{GDBN} only knows partially---that is, symbols defined in
16572 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
16573 @samp{maint print msymbols} dumps just the minimal symbol information
16574 required for each object file from which @value{GDBN} has read some symbols.
16575 @xref{Files, ,Commands to Specify Files}, for a discussion of how
16576 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
16578 @kindex maint info symtabs
16579 @kindex maint info psymtabs
16580 @cindex listing @value{GDBN}'s internal symbol tables
16581 @cindex symbol tables, listing @value{GDBN}'s internal
16582 @cindex full symbol tables, listing @value{GDBN}'s internal
16583 @cindex partial symbol tables, listing @value{GDBN}'s internal
16584 @item maint info symtabs @r{[} @var{regexp} @r{]}
16585 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
16587 List the @code{struct symtab} or @code{struct partial_symtab}
16588 structures whose names match @var{regexp}. If @var{regexp} is not
16589 given, list them all. The output includes expressions which you can
16590 copy into a @value{GDBN} debugging this one to examine a particular
16591 structure in more detail. For example:
16594 (@value{GDBP}) maint info psymtabs dwarf2read
16595 @{ objfile /home/gnu/build/gdb/gdb
16596 ((struct objfile *) 0x82e69d0)
16597 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
16598 ((struct partial_symtab *) 0x8474b10)
16601 text addresses 0x814d3c8 -- 0x8158074
16602 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
16603 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
16604 dependencies (none)
16607 (@value{GDBP}) maint info symtabs
16611 We see that there is one partial symbol table whose filename contains
16612 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
16613 and we see that @value{GDBN} has not read in any symtabs yet at all.
16614 If we set a breakpoint on a function, that will cause @value{GDBN} to
16615 read the symtab for the compilation unit containing that function:
16618 (@value{GDBP}) break dwarf2_psymtab_to_symtab
16619 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
16621 (@value{GDBP}) maint info symtabs
16622 @{ objfile /home/gnu/build/gdb/gdb
16623 ((struct objfile *) 0x82e69d0)
16624 @{ symtab /home/gnu/src/gdb/dwarf2read.c
16625 ((struct symtab *) 0x86c1f38)
16628 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
16629 linetable ((struct linetable *) 0x8370fa0)
16630 debugformat DWARF 2
16636 @kindex maint set symbol-cache-size
16637 @cindex symbol cache size
16638 @item maint set symbol-cache-size @var{size}
16639 Set the size of the symbol cache to @var{size}.
16640 The default size is intended to be good enough for debugging
16641 most applications. This option exists to allow for experimenting
16642 with different sizes.
16644 @kindex maint show symbol-cache-size
16645 @item maint show symbol-cache-size
16646 Show the size of the symbol cache.
16648 @kindex maint print symbol-cache
16649 @cindex symbol cache, printing its contents
16650 @item maint print symbol-cache
16651 Print the contents of the symbol cache.
16652 This is useful when debugging symbol cache issues.
16654 @kindex maint print symbol-cache-statistics
16655 @cindex symbol cache, printing usage statistics
16656 @item maint print symbol-cache-statistics
16657 Print symbol cache usage statistics.
16658 This helps determine how well the cache is being utilized.
16660 @kindex maint flush-symbol-cache
16661 @cindex symbol cache, flushing
16662 @item maint flush-symbol-cache
16663 Flush the contents of the symbol cache, all entries are removed.
16664 This command is useful when debugging the symbol cache.
16665 It is also useful when collecting performance data.
16670 @chapter Altering Execution
16672 Once you think you have found an error in your program, you might want to
16673 find out for certain whether correcting the apparent error would lead to
16674 correct results in the rest of the run. You can find the answer by
16675 experiment, using the @value{GDBN} features for altering execution of the
16678 For example, you can store new values into variables or memory
16679 locations, give your program a signal, restart it at a different
16680 address, or even return prematurely from a function.
16683 * Assignment:: Assignment to variables
16684 * Jumping:: Continuing at a different address
16685 * Signaling:: Giving your program a signal
16686 * Returning:: Returning from a function
16687 * Calling:: Calling your program's functions
16688 * Patching:: Patching your program
16689 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
16693 @section Assignment to Variables
16696 @cindex setting variables
16697 To alter the value of a variable, evaluate an assignment expression.
16698 @xref{Expressions, ,Expressions}. For example,
16705 stores the value 4 into the variable @code{x}, and then prints the
16706 value of the assignment expression (which is 4).
16707 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
16708 information on operators in supported languages.
16710 @kindex set variable
16711 @cindex variables, setting
16712 If you are not interested in seeing the value of the assignment, use the
16713 @code{set} command instead of the @code{print} command. @code{set} is
16714 really the same as @code{print} except that the expression's value is
16715 not printed and is not put in the value history (@pxref{Value History,
16716 ,Value History}). The expression is evaluated only for its effects.
16718 If the beginning of the argument string of the @code{set} command
16719 appears identical to a @code{set} subcommand, use the @code{set
16720 variable} command instead of just @code{set}. This command is identical
16721 to @code{set} except for its lack of subcommands. For example, if your
16722 program has a variable @code{width}, you get an error if you try to set
16723 a new value with just @samp{set width=13}, because @value{GDBN} has the
16724 command @code{set width}:
16727 (@value{GDBP}) whatis width
16729 (@value{GDBP}) p width
16731 (@value{GDBP}) set width=47
16732 Invalid syntax in expression.
16736 The invalid expression, of course, is @samp{=47}. In
16737 order to actually set the program's variable @code{width}, use
16740 (@value{GDBP}) set var width=47
16743 Because the @code{set} command has many subcommands that can conflict
16744 with the names of program variables, it is a good idea to use the
16745 @code{set variable} command instead of just @code{set}. For example, if
16746 your program has a variable @code{g}, you run into problems if you try
16747 to set a new value with just @samp{set g=4}, because @value{GDBN} has
16748 the command @code{set gnutarget}, abbreviated @code{set g}:
16752 (@value{GDBP}) whatis g
16756 (@value{GDBP}) set g=4
16760 The program being debugged has been started already.
16761 Start it from the beginning? (y or n) y
16762 Starting program: /home/smith/cc_progs/a.out
16763 "/home/smith/cc_progs/a.out": can't open to read symbols:
16764 Invalid bfd target.
16765 (@value{GDBP}) show g
16766 The current BFD target is "=4".
16771 The program variable @code{g} did not change, and you silently set the
16772 @code{gnutarget} to an invalid value. In order to set the variable
16776 (@value{GDBP}) set var g=4
16779 @value{GDBN} allows more implicit conversions in assignments than C; you can
16780 freely store an integer value into a pointer variable or vice versa,
16781 and you can convert any structure to any other structure that is the
16782 same length or shorter.
16783 @comment FIXME: how do structs align/pad in these conversions?
16784 @comment /doc@cygnus.com 18dec1990
16786 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
16787 construct to generate a value of specified type at a specified address
16788 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
16789 to memory location @code{0x83040} as an integer (which implies a certain size
16790 and representation in memory), and
16793 set @{int@}0x83040 = 4
16797 stores the value 4 into that memory location.
16800 @section Continuing at a Different Address
16802 Ordinarily, when you continue your program, you do so at the place where
16803 it stopped, with the @code{continue} command. You can instead continue at
16804 an address of your own choosing, with the following commands:
16808 @kindex j @r{(@code{jump})}
16809 @item jump @var{linespec}
16810 @itemx j @var{linespec}
16811 @itemx jump @var{location}
16812 @itemx j @var{location}
16813 Resume execution at line @var{linespec} or at address given by
16814 @var{location}. Execution stops again immediately if there is a
16815 breakpoint there. @xref{Specify Location}, for a description of the
16816 different forms of @var{linespec} and @var{location}. It is common
16817 practice to use the @code{tbreak} command in conjunction with
16818 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
16820 The @code{jump} command does not change the current stack frame, or
16821 the stack pointer, or the contents of any memory location or any
16822 register other than the program counter. If line @var{linespec} is in
16823 a different function from the one currently executing, the results may
16824 be bizarre if the two functions expect different patterns of arguments or
16825 of local variables. For this reason, the @code{jump} command requests
16826 confirmation if the specified line is not in the function currently
16827 executing. However, even bizarre results are predictable if you are
16828 well acquainted with the machine-language code of your program.
16831 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
16832 On many systems, you can get much the same effect as the @code{jump}
16833 command by storing a new value into the register @code{$pc}. The
16834 difference is that this does not start your program running; it only
16835 changes the address of where it @emph{will} run when you continue. For
16843 makes the next @code{continue} command or stepping command execute at
16844 address @code{0x485}, rather than at the address where your program stopped.
16845 @xref{Continuing and Stepping, ,Continuing and Stepping}.
16847 The most common occasion to use the @code{jump} command is to back
16848 up---perhaps with more breakpoints set---over a portion of a program
16849 that has already executed, in order to examine its execution in more
16854 @section Giving your Program a Signal
16855 @cindex deliver a signal to a program
16859 @item signal @var{signal}
16860 Resume execution where your program is stopped, but immediately give it the
16861 signal @var{signal}. The @var{signal} can be the name or the number of a
16862 signal. For example, on many systems @code{signal 2} and @code{signal
16863 SIGINT} are both ways of sending an interrupt signal.
16865 Alternatively, if @var{signal} is zero, continue execution without
16866 giving a signal. This is useful when your program stopped on account of
16867 a signal and would ordinarily see the signal when resumed with the
16868 @code{continue} command; @samp{signal 0} causes it to resume without a
16871 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
16872 delivered to the currently selected thread, not the thread that last
16873 reported a stop. This includes the situation where a thread was
16874 stopped due to a signal. So if you want to continue execution
16875 suppressing the signal that stopped a thread, you should select that
16876 same thread before issuing the @samp{signal 0} command. If you issue
16877 the @samp{signal 0} command with another thread as the selected one,
16878 @value{GDBN} detects that and asks for confirmation.
16880 Invoking the @code{signal} command is not the same as invoking the
16881 @code{kill} utility from the shell. Sending a signal with @code{kill}
16882 causes @value{GDBN} to decide what to do with the signal depending on
16883 the signal handling tables (@pxref{Signals}). The @code{signal} command
16884 passes the signal directly to your program.
16886 @code{signal} does not repeat when you press @key{RET} a second time
16887 after executing the command.
16889 @kindex queue-signal
16890 @item queue-signal @var{signal}
16891 Queue @var{signal} to be delivered immediately to the current thread
16892 when execution of the thread resumes. The @var{signal} can be the name or
16893 the number of a signal. For example, on many systems @code{signal 2} and
16894 @code{signal SIGINT} are both ways of sending an interrupt signal.
16895 The handling of the signal must be set to pass the signal to the program,
16896 otherwise @value{GDBN} will report an error.
16897 You can control the handling of signals from @value{GDBN} with the
16898 @code{handle} command (@pxref{Signals}).
16900 Alternatively, if @var{signal} is zero, any currently queued signal
16901 for the current thread is discarded and when execution resumes no signal
16902 will be delivered. This is useful when your program stopped on account
16903 of a signal and would ordinarily see the signal when resumed with the
16904 @code{continue} command.
16906 This command differs from the @code{signal} command in that the signal
16907 is just queued, execution is not resumed. And @code{queue-signal} cannot
16908 be used to pass a signal whose handling state has been set to @code{nopass}
16913 @xref{stepping into signal handlers}, for information on how stepping
16914 commands behave when the thread has a signal queued.
16917 @section Returning from a Function
16920 @cindex returning from a function
16923 @itemx return @var{expression}
16924 You can cancel execution of a function call with the @code{return}
16925 command. If you give an
16926 @var{expression} argument, its value is used as the function's return
16930 When you use @code{return}, @value{GDBN} discards the selected stack frame
16931 (and all frames within it). You can think of this as making the
16932 discarded frame return prematurely. If you wish to specify a value to
16933 be returned, give that value as the argument to @code{return}.
16935 This pops the selected stack frame (@pxref{Selection, ,Selecting a
16936 Frame}), and any other frames inside of it, leaving its caller as the
16937 innermost remaining frame. That frame becomes selected. The
16938 specified value is stored in the registers used for returning values
16941 The @code{return} command does not resume execution; it leaves the
16942 program stopped in the state that would exist if the function had just
16943 returned. In contrast, the @code{finish} command (@pxref{Continuing
16944 and Stepping, ,Continuing and Stepping}) resumes execution until the
16945 selected stack frame returns naturally.
16947 @value{GDBN} needs to know how the @var{expression} argument should be set for
16948 the inferior. The concrete registers assignment depends on the OS ABI and the
16949 type being returned by the selected stack frame. For example it is common for
16950 OS ABI to return floating point values in FPU registers while integer values in
16951 CPU registers. Still some ABIs return even floating point values in CPU
16952 registers. Larger integer widths (such as @code{long long int}) also have
16953 specific placement rules. @value{GDBN} already knows the OS ABI from its
16954 current target so it needs to find out also the type being returned to make the
16955 assignment into the right register(s).
16957 Normally, the selected stack frame has debug info. @value{GDBN} will always
16958 use the debug info instead of the implicit type of @var{expression} when the
16959 debug info is available. For example, if you type @kbd{return -1}, and the
16960 function in the current stack frame is declared to return a @code{long long
16961 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
16962 into a @code{long long int}:
16965 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
16967 (@value{GDBP}) return -1
16968 Make func return now? (y or n) y
16969 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
16970 43 printf ("result=%lld\n", func ());
16974 However, if the selected stack frame does not have a debug info, e.g., if the
16975 function was compiled without debug info, @value{GDBN} has to find out the type
16976 to return from user. Specifying a different type by mistake may set the value
16977 in different inferior registers than the caller code expects. For example,
16978 typing @kbd{return -1} with its implicit type @code{int} would set only a part
16979 of a @code{long long int} result for a debug info less function (on 32-bit
16980 architectures). Therefore the user is required to specify the return type by
16981 an appropriate cast explicitly:
16984 Breakpoint 2, 0x0040050b in func ()
16985 (@value{GDBP}) return -1
16986 Return value type not available for selected stack frame.
16987 Please use an explicit cast of the value to return.
16988 (@value{GDBP}) return (long long int) -1
16989 Make selected stack frame return now? (y or n) y
16990 #0 0x00400526 in main ()
16995 @section Calling Program Functions
16998 @cindex calling functions
16999 @cindex inferior functions, calling
17000 @item print @var{expr}
17001 Evaluate the expression @var{expr} and display the resulting value.
17002 The expression may include calls to functions in the program being
17006 @item call @var{expr}
17007 Evaluate the expression @var{expr} without displaying @code{void}
17010 You can use this variant of the @code{print} command if you want to
17011 execute a function from your program that does not return anything
17012 (a.k.a.@: @dfn{a void function}), but without cluttering the output
17013 with @code{void} returned values that @value{GDBN} will otherwise
17014 print. If the result is not void, it is printed and saved in the
17018 It is possible for the function you call via the @code{print} or
17019 @code{call} command to generate a signal (e.g., if there's a bug in
17020 the function, or if you passed it incorrect arguments). What happens
17021 in that case is controlled by the @code{set unwindonsignal} command.
17023 Similarly, with a C@t{++} program it is possible for the function you
17024 call via the @code{print} or @code{call} command to generate an
17025 exception that is not handled due to the constraints of the dummy
17026 frame. In this case, any exception that is raised in the frame, but has
17027 an out-of-frame exception handler will not be found. GDB builds a
17028 dummy-frame for the inferior function call, and the unwinder cannot
17029 seek for exception handlers outside of this dummy-frame. What happens
17030 in that case is controlled by the
17031 @code{set unwind-on-terminating-exception} command.
17034 @item set unwindonsignal
17035 @kindex set unwindonsignal
17036 @cindex unwind stack in called functions
17037 @cindex call dummy stack unwinding
17038 Set unwinding of the stack if a signal is received while in a function
17039 that @value{GDBN} called in the program being debugged. If set to on,
17040 @value{GDBN} unwinds the stack it created for the call and restores
17041 the context to what it was before the call. If set to off (the
17042 default), @value{GDBN} stops in the frame where the signal was
17045 @item show unwindonsignal
17046 @kindex show unwindonsignal
17047 Show the current setting of stack unwinding in the functions called by
17050 @item set unwind-on-terminating-exception
17051 @kindex set unwind-on-terminating-exception
17052 @cindex unwind stack in called functions with unhandled exceptions
17053 @cindex call dummy stack unwinding on unhandled exception.
17054 Set unwinding of the stack if a C@t{++} exception is raised, but left
17055 unhandled while in a function that @value{GDBN} called in the program being
17056 debugged. If set to on (the default), @value{GDBN} unwinds the stack
17057 it created for the call and restores the context to what it was before
17058 the call. If set to off, @value{GDBN} the exception is delivered to
17059 the default C@t{++} exception handler and the inferior terminated.
17061 @item show unwind-on-terminating-exception
17062 @kindex show unwind-on-terminating-exception
17063 Show the current setting of stack unwinding in the functions called by
17068 @cindex weak alias functions
17069 Sometimes, a function you wish to call is actually a @dfn{weak alias}
17070 for another function. In such case, @value{GDBN} might not pick up
17071 the type information, including the types of the function arguments,
17072 which causes @value{GDBN} to call the inferior function incorrectly.
17073 As a result, the called function will function erroneously and may
17074 even crash. A solution to that is to use the name of the aliased
17078 @section Patching Programs
17080 @cindex patching binaries
17081 @cindex writing into executables
17082 @cindex writing into corefiles
17084 By default, @value{GDBN} opens the file containing your program's
17085 executable code (or the corefile) read-only. This prevents accidental
17086 alterations to machine code; but it also prevents you from intentionally
17087 patching your program's binary.
17089 If you'd like to be able to patch the binary, you can specify that
17090 explicitly with the @code{set write} command. For example, you might
17091 want to turn on internal debugging flags, or even to make emergency
17097 @itemx set write off
17098 If you specify @samp{set write on}, @value{GDBN} opens executable and
17099 core files for both reading and writing; if you specify @kbd{set write
17100 off} (the default), @value{GDBN} opens them read-only.
17102 If you have already loaded a file, you must load it again (using the
17103 @code{exec-file} or @code{core-file} command) after changing @code{set
17104 write}, for your new setting to take effect.
17108 Display whether executable files and core files are opened for writing
17109 as well as reading.
17112 @node Compiling and Injecting Code
17113 @section Compiling and injecting code in @value{GDBN}
17114 @cindex injecting code
17115 @cindex writing into executables
17116 @cindex compiling code
17118 @value{GDBN} supports on-demand compilation and code injection into
17119 programs running under @value{GDBN}. GCC 5.0 or higher built with
17120 @file{libcc1.so} must be installed for this functionality to be enabled.
17121 This functionality is implemented with the following commands.
17124 @kindex compile code
17125 @item compile code @var{source-code}
17126 @itemx compile code -raw @var{--} @var{source-code}
17127 Compile @var{source-code} with the compiler language found as the current
17128 language in @value{GDBN} (@pxref{Languages}). If compilation and
17129 injection is not supported with the current language specified in
17130 @value{GDBN}, or the compiler does not support this feature, an error
17131 message will be printed. If @var{source-code} compiles and links
17132 successfully, @value{GDBN} will load the object-code emitted,
17133 and execute it within the context of the currently selected inferior.
17134 It is important to note that the compiled code is executed immediately.
17135 After execution, the compiled code is removed from @value{GDBN} and any
17136 new types or variables you have defined will be deleted.
17138 The command allows you to specify @var{source-code} in two ways.
17139 The simplest method is to provide a single line of code to the command.
17143 compile code printf ("hello world\n");
17146 If you specify options on the command line as well as source code, they
17147 may conflict. The @samp{--} delimiter can be used to separate options
17148 from actual source code. E.g.:
17151 compile code -r -- printf ("hello world\n");
17154 Alternatively you can enter source code as multiple lines of text. To
17155 enter this mode, invoke the @samp{compile code} command without any text
17156 following the command. This will start the multiple-line editor and
17157 allow you to type as many lines of source code as required. When you
17158 have completed typing, enter @samp{end} on its own line to exit the
17163 >printf ("hello\n");
17164 >printf ("world\n");
17168 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
17169 provided @var{source-code} in a callable scope. In this case, you must
17170 specify the entry point of the code by defining a function named
17171 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
17172 inferior. Using @samp{-raw} option may be needed for example when
17173 @var{source-code} requires @samp{#include} lines which may conflict with
17174 inferior symbols otherwise.
17176 @kindex compile file
17177 @item compile file @var{filename}
17178 @itemx compile file -raw @var{filename}
17179 Like @code{compile code}, but take the source code from @var{filename}.
17182 compile file /home/user/example.c
17186 @subsection Caveats when using the @code{compile} command
17188 There are a few caveats to keep in mind when using the @code{compile}
17189 command. As the caveats are different per language, the table below
17190 highlights specific issues on a per language basis.
17193 @item C code examples and caveats
17194 When the language in @value{GDBN} is set to @samp{C}, the compiler will
17195 attempt to compile the source code with a @samp{C} compiler. The source
17196 code provided to the @code{compile} command will have much the same
17197 access to variables and types as it normally would if it were part of
17198 the program currently being debugged in @value{GDBN}.
17200 Below is a sample program that forms the basis of the examples that
17201 follow. This program has been compiled and loaded into @value{GDBN},
17202 much like any other normal debugging session.
17205 void function1 (void)
17208 printf ("function 1\n");
17211 void function2 (void)
17226 For the purposes of the examples in this section, the program above has
17227 been compiled, loaded into @value{GDBN}, stopped at the function
17228 @code{main}, and @value{GDBN} is awaiting input from the user.
17230 To access variables and types for any program in @value{GDBN}, the
17231 program must be compiled and packaged with debug information. The
17232 @code{compile} command is not an exception to this rule. Without debug
17233 information, you can still use the @code{compile} command, but you will
17234 be very limited in what variables and types you can access.
17236 So with that in mind, the example above has been compiled with debug
17237 information enabled. The @code{compile} command will have access to
17238 all variables and types (except those that may have been optimized
17239 out). Currently, as @value{GDBN} has stopped the program in the
17240 @code{main} function, the @code{compile} command would have access to
17241 the variable @code{k}. You could invoke the @code{compile} command
17242 and type some source code to set the value of @code{k}. You can also
17243 read it, or do anything with that variable you would normally do in
17244 @code{C}. Be aware that changes to inferior variables in the
17245 @code{compile} command are persistent. In the following example:
17248 compile code k = 3;
17252 the variable @code{k} is now 3. It will retain that value until
17253 something else in the example program changes it, or another
17254 @code{compile} command changes it.
17256 Normal scope and access rules apply to source code compiled and
17257 injected by the @code{compile} command. In the example, the variables
17258 @code{j} and @code{k} are not accessible yet, because the program is
17259 currently stopped in the @code{main} function, where these variables
17260 are not in scope. Therefore, the following command
17263 compile code j = 3;
17267 will result in a compilation error message.
17269 Once the program is continued, execution will bring these variables in
17270 scope, and they will become accessible; then the code you specify via
17271 the @code{compile} command will be able to access them.
17273 You can create variables and types with the @code{compile} command as
17274 part of your source code. Variables and types that are created as part
17275 of the @code{compile} command are not visible to the rest of the program for
17276 the duration of its run. This example is valid:
17279 compile code int ff = 5; printf ("ff is %d\n", ff);
17282 However, if you were to type the following into @value{GDBN} after that
17283 command has completed:
17286 compile code printf ("ff is %d\n'', ff);
17290 a compiler error would be raised as the variable @code{ff} no longer
17291 exists. Object code generated and injected by the @code{compile}
17292 command is removed when its execution ends. Caution is advised
17293 when assigning to program variables values of variables created by the
17294 code submitted to the @code{compile} command. This example is valid:
17297 compile code int ff = 5; k = ff;
17300 The value of the variable @code{ff} is assigned to @code{k}. The variable
17301 @code{k} does not require the existence of @code{ff} to maintain the value
17302 it has been assigned. However, pointers require particular care in
17303 assignment. If the source code compiled with the @code{compile} command
17304 changed the address of a pointer in the example program, perhaps to a
17305 variable created in the @code{compile} command, that pointer would point
17306 to an invalid location when the command exits. The following example
17307 would likely cause issues with your debugged program:
17310 compile code int ff = 5; p = &ff;
17313 In this example, @code{p} would point to @code{ff} when the
17314 @code{compile} command is executing the source code provided to it.
17315 However, as variables in the (example) program persist with their
17316 assigned values, the variable @code{p} would point to an invalid
17317 location when the command exists. A general rule should be followed
17318 in that you should either assign @code{NULL} to any assigned pointers,
17319 or restore a valid location to the pointer before the command exits.
17321 Similar caution must be exercised with any structs, unions, and typedefs
17322 defined in @code{compile} command. Types defined in the @code{compile}
17323 command will no longer be available in the next @code{compile} command.
17324 Therefore, if you cast a variable to a type defined in the
17325 @code{compile} command, care must be taken to ensure that any future
17326 need to resolve the type can be achieved.
17329 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
17330 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
17331 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
17332 Compilation failed.
17333 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
17337 Variables that have been optimized away by the compiler are not
17338 accessible to the code submitted to the @code{compile} command.
17339 Access to those variables will generate a compiler error which @value{GDBN}
17340 will print to the console.
17344 @chapter @value{GDBN} Files
17346 @value{GDBN} needs to know the file name of the program to be debugged,
17347 both in order to read its symbol table and in order to start your
17348 program. To debug a core dump of a previous run, you must also tell
17349 @value{GDBN} the name of the core dump file.
17352 * Files:: Commands to specify files
17353 * Separate Debug Files:: Debugging information in separate files
17354 * MiniDebugInfo:: Debugging information in a special section
17355 * Index Files:: Index files speed up GDB
17356 * Symbol Errors:: Errors reading symbol files
17357 * Data Files:: GDB data files
17361 @section Commands to Specify Files
17363 @cindex symbol table
17364 @cindex core dump file
17366 You may want to specify executable and core dump file names. The usual
17367 way to do this is at start-up time, using the arguments to
17368 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
17369 Out of @value{GDBN}}).
17371 Occasionally it is necessary to change to a different file during a
17372 @value{GDBN} session. Or you may run @value{GDBN} and forget to
17373 specify a file you want to use. Or you are debugging a remote target
17374 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
17375 Program}). In these situations the @value{GDBN} commands to specify
17376 new files are useful.
17379 @cindex executable file
17381 @item file @var{filename}
17382 Use @var{filename} as the program to be debugged. It is read for its
17383 symbols and for the contents of pure memory. It is also the program
17384 executed when you use the @code{run} command. If you do not specify a
17385 directory and the file is not found in the @value{GDBN} working directory,
17386 @value{GDBN} uses the environment variable @code{PATH} as a list of
17387 directories to search, just as the shell does when looking for a program
17388 to run. You can change the value of this variable, for both @value{GDBN}
17389 and your program, using the @code{path} command.
17391 @cindex unlinked object files
17392 @cindex patching object files
17393 You can load unlinked object @file{.o} files into @value{GDBN} using
17394 the @code{file} command. You will not be able to ``run'' an object
17395 file, but you can disassemble functions and inspect variables. Also,
17396 if the underlying BFD functionality supports it, you could use
17397 @kbd{gdb -write} to patch object files using this technique. Note
17398 that @value{GDBN} can neither interpret nor modify relocations in this
17399 case, so branches and some initialized variables will appear to go to
17400 the wrong place. But this feature is still handy from time to time.
17403 @code{file} with no argument makes @value{GDBN} discard any information it
17404 has on both executable file and the symbol table.
17407 @item exec-file @r{[} @var{filename} @r{]}
17408 Specify that the program to be run (but not the symbol table) is found
17409 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
17410 if necessary to locate your program. Omitting @var{filename} means to
17411 discard information on the executable file.
17413 @kindex symbol-file
17414 @item symbol-file @r{[} @var{filename} @r{]}
17415 Read symbol table information from file @var{filename}. @code{PATH} is
17416 searched when necessary. Use the @code{file} command to get both symbol
17417 table and program to run from the same file.
17419 @code{symbol-file} with no argument clears out @value{GDBN} information on your
17420 program's symbol table.
17422 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
17423 some breakpoints and auto-display expressions. This is because they may
17424 contain pointers to the internal data recording symbols and data types,
17425 which are part of the old symbol table data being discarded inside
17428 @code{symbol-file} does not repeat if you press @key{RET} again after
17431 When @value{GDBN} is configured for a particular environment, it
17432 understands debugging information in whatever format is the standard
17433 generated for that environment; you may use either a @sc{gnu} compiler, or
17434 other compilers that adhere to the local conventions.
17435 Best results are usually obtained from @sc{gnu} compilers; for example,
17436 using @code{@value{NGCC}} you can generate debugging information for
17439 For most kinds of object files, with the exception of old SVR3 systems
17440 using COFF, the @code{symbol-file} command does not normally read the
17441 symbol table in full right away. Instead, it scans the symbol table
17442 quickly to find which source files and which symbols are present. The
17443 details are read later, one source file at a time, as they are needed.
17445 The purpose of this two-stage reading strategy is to make @value{GDBN}
17446 start up faster. For the most part, it is invisible except for
17447 occasional pauses while the symbol table details for a particular source
17448 file are being read. (The @code{set verbose} command can turn these
17449 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
17450 Warnings and Messages}.)
17452 We have not implemented the two-stage strategy for COFF yet. When the
17453 symbol table is stored in COFF format, @code{symbol-file} reads the
17454 symbol table data in full right away. Note that ``stabs-in-COFF''
17455 still does the two-stage strategy, since the debug info is actually
17459 @cindex reading symbols immediately
17460 @cindex symbols, reading immediately
17461 @item symbol-file @r{[} -readnow @r{]} @var{filename}
17462 @itemx file @r{[} -readnow @r{]} @var{filename}
17463 You can override the @value{GDBN} two-stage strategy for reading symbol
17464 tables by using the @samp{-readnow} option with any of the commands that
17465 load symbol table information, if you want to be sure @value{GDBN} has the
17466 entire symbol table available.
17468 @c FIXME: for now no mention of directories, since this seems to be in
17469 @c flux. 13mar1992 status is that in theory GDB would look either in
17470 @c current dir or in same dir as myprog; but issues like competing
17471 @c GDB's, or clutter in system dirs, mean that in practice right now
17472 @c only current dir is used. FFish says maybe a special GDB hierarchy
17473 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
17477 @item core-file @r{[}@var{filename}@r{]}
17479 Specify the whereabouts of a core dump file to be used as the ``contents
17480 of memory''. Traditionally, core files contain only some parts of the
17481 address space of the process that generated them; @value{GDBN} can access the
17482 executable file itself for other parts.
17484 @code{core-file} with no argument specifies that no core file is
17487 Note that the core file is ignored when your program is actually running
17488 under @value{GDBN}. So, if you have been running your program and you
17489 wish to debug a core file instead, you must kill the subprocess in which
17490 the program is running. To do this, use the @code{kill} command
17491 (@pxref{Kill Process, ,Killing the Child Process}).
17493 @kindex add-symbol-file
17494 @cindex dynamic linking
17495 @item add-symbol-file @var{filename} @var{address}
17496 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
17497 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
17498 The @code{add-symbol-file} command reads additional symbol table
17499 information from the file @var{filename}. You would use this command
17500 when @var{filename} has been dynamically loaded (by some other means)
17501 into the program that is running. The @var{address} should give the memory
17502 address at which the file has been loaded; @value{GDBN} cannot figure
17503 this out for itself. You can additionally specify an arbitrary number
17504 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
17505 section name and base address for that section. You can specify any
17506 @var{address} as an expression.
17508 The symbol table of the file @var{filename} is added to the symbol table
17509 originally read with the @code{symbol-file} command. You can use the
17510 @code{add-symbol-file} command any number of times; the new symbol data
17511 thus read is kept in addition to the old.
17513 Changes can be reverted using the command @code{remove-symbol-file}.
17515 @cindex relocatable object files, reading symbols from
17516 @cindex object files, relocatable, reading symbols from
17517 @cindex reading symbols from relocatable object files
17518 @cindex symbols, reading from relocatable object files
17519 @cindex @file{.o} files, reading symbols from
17520 Although @var{filename} is typically a shared library file, an
17521 executable file, or some other object file which has been fully
17522 relocated for loading into a process, you can also load symbolic
17523 information from relocatable @file{.o} files, as long as:
17527 the file's symbolic information refers only to linker symbols defined in
17528 that file, not to symbols defined by other object files,
17530 every section the file's symbolic information refers to has actually
17531 been loaded into the inferior, as it appears in the file, and
17533 you can determine the address at which every section was loaded, and
17534 provide these to the @code{add-symbol-file} command.
17538 Some embedded operating systems, like Sun Chorus and VxWorks, can load
17539 relocatable files into an already running program; such systems
17540 typically make the requirements above easy to meet. However, it's
17541 important to recognize that many native systems use complex link
17542 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
17543 assembly, for example) that make the requirements difficult to meet. In
17544 general, one cannot assume that using @code{add-symbol-file} to read a
17545 relocatable object file's symbolic information will have the same effect
17546 as linking the relocatable object file into the program in the normal
17549 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
17551 @kindex remove-symbol-file
17552 @item remove-symbol-file @var{filename}
17553 @item remove-symbol-file -a @var{address}
17554 Remove a symbol file added via the @code{add-symbol-file} command. The
17555 file to remove can be identified by its @var{filename} or by an @var{address}
17556 that lies within the boundaries of this symbol file in memory. Example:
17559 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
17560 add symbol table from file "/home/user/gdb/mylib.so" at
17561 .text_addr = 0x7ffff7ff9480
17563 Reading symbols from /home/user/gdb/mylib.so...done.
17564 (gdb) remove-symbol-file -a 0x7ffff7ff9480
17565 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
17570 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
17572 @kindex add-symbol-file-from-memory
17573 @cindex @code{syscall DSO}
17574 @cindex load symbols from memory
17575 @item add-symbol-file-from-memory @var{address}
17576 Load symbols from the given @var{address} in a dynamically loaded
17577 object file whose image is mapped directly into the inferior's memory.
17578 For example, the Linux kernel maps a @code{syscall DSO} into each
17579 process's address space; this DSO provides kernel-specific code for
17580 some system calls. The argument can be any expression whose
17581 evaluation yields the address of the file's shared object file header.
17582 For this command to work, you must have used @code{symbol-file} or
17583 @code{exec-file} commands in advance.
17586 @item section @var{section} @var{addr}
17587 The @code{section} command changes the base address of the named
17588 @var{section} of the exec file to @var{addr}. This can be used if the
17589 exec file does not contain section addresses, (such as in the
17590 @code{a.out} format), or when the addresses specified in the file
17591 itself are wrong. Each section must be changed separately. The
17592 @code{info files} command, described below, lists all the sections and
17596 @kindex info target
17599 @code{info files} and @code{info target} are synonymous; both print the
17600 current target (@pxref{Targets, ,Specifying a Debugging Target}),
17601 including the names of the executable and core dump files currently in
17602 use by @value{GDBN}, and the files from which symbols were loaded. The
17603 command @code{help target} lists all possible targets rather than
17606 @kindex maint info sections
17607 @item maint info sections
17608 Another command that can give you extra information about program sections
17609 is @code{maint info sections}. In addition to the section information
17610 displayed by @code{info files}, this command displays the flags and file
17611 offset of each section in the executable and core dump files. In addition,
17612 @code{maint info sections} provides the following command options (which
17613 may be arbitrarily combined):
17617 Display sections for all loaded object files, including shared libraries.
17618 @item @var{sections}
17619 Display info only for named @var{sections}.
17620 @item @var{section-flags}
17621 Display info only for sections for which @var{section-flags} are true.
17622 The section flags that @value{GDBN} currently knows about are:
17625 Section will have space allocated in the process when loaded.
17626 Set for all sections except those containing debug information.
17628 Section will be loaded from the file into the child process memory.
17629 Set for pre-initialized code and data, clear for @code{.bss} sections.
17631 Section needs to be relocated before loading.
17633 Section cannot be modified by the child process.
17635 Section contains executable code only.
17637 Section contains data only (no executable code).
17639 Section will reside in ROM.
17641 Section contains data for constructor/destructor lists.
17643 Section is not empty.
17645 An instruction to the linker to not output the section.
17646 @item COFF_SHARED_LIBRARY
17647 A notification to the linker that the section contains
17648 COFF shared library information.
17650 Section contains common symbols.
17653 @kindex set trust-readonly-sections
17654 @cindex read-only sections
17655 @item set trust-readonly-sections on
17656 Tell @value{GDBN} that readonly sections in your object file
17657 really are read-only (i.e.@: that their contents will not change).
17658 In that case, @value{GDBN} can fetch values from these sections
17659 out of the object file, rather than from the target program.
17660 For some targets (notably embedded ones), this can be a significant
17661 enhancement to debugging performance.
17663 The default is off.
17665 @item set trust-readonly-sections off
17666 Tell @value{GDBN} not to trust readonly sections. This means that
17667 the contents of the section might change while the program is running,
17668 and must therefore be fetched from the target when needed.
17670 @item show trust-readonly-sections
17671 Show the current setting of trusting readonly sections.
17674 All file-specifying commands allow both absolute and relative file names
17675 as arguments. @value{GDBN} always converts the file name to an absolute file
17676 name and remembers it that way.
17678 @cindex shared libraries
17679 @anchor{Shared Libraries}
17680 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
17681 and IBM RS/6000 AIX shared libraries.
17683 On MS-Windows @value{GDBN} must be linked with the Expat library to support
17684 shared libraries. @xref{Expat}.
17686 @value{GDBN} automatically loads symbol definitions from shared libraries
17687 when you use the @code{run} command, or when you examine a core file.
17688 (Before you issue the @code{run} command, @value{GDBN} does not understand
17689 references to a function in a shared library, however---unless you are
17690 debugging a core file).
17692 On HP-UX, if the program loads a library explicitly, @value{GDBN}
17693 automatically loads the symbols at the time of the @code{shl_load} call.
17695 @c FIXME: some @value{GDBN} release may permit some refs to undef
17696 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
17697 @c FIXME...lib; check this from time to time when updating manual
17699 There are times, however, when you may wish to not automatically load
17700 symbol definitions from shared libraries, such as when they are
17701 particularly large or there are many of them.
17703 To control the automatic loading of shared library symbols, use the
17707 @kindex set auto-solib-add
17708 @item set auto-solib-add @var{mode}
17709 If @var{mode} is @code{on}, symbols from all shared object libraries
17710 will be loaded automatically when the inferior begins execution, you
17711 attach to an independently started inferior, or when the dynamic linker
17712 informs @value{GDBN} that a new library has been loaded. If @var{mode}
17713 is @code{off}, symbols must be loaded manually, using the
17714 @code{sharedlibrary} command. The default value is @code{on}.
17716 @cindex memory used for symbol tables
17717 If your program uses lots of shared libraries with debug info that
17718 takes large amounts of memory, you can decrease the @value{GDBN}
17719 memory footprint by preventing it from automatically loading the
17720 symbols from shared libraries. To that end, type @kbd{set
17721 auto-solib-add off} before running the inferior, then load each
17722 library whose debug symbols you do need with @kbd{sharedlibrary
17723 @var{regexp}}, where @var{regexp} is a regular expression that matches
17724 the libraries whose symbols you want to be loaded.
17726 @kindex show auto-solib-add
17727 @item show auto-solib-add
17728 Display the current autoloading mode.
17731 @cindex load shared library
17732 To explicitly load shared library symbols, use the @code{sharedlibrary}
17736 @kindex info sharedlibrary
17738 @item info share @var{regex}
17739 @itemx info sharedlibrary @var{regex}
17740 Print the names of the shared libraries which are currently loaded
17741 that match @var{regex}. If @var{regex} is omitted then print
17742 all shared libraries that are loaded.
17744 @kindex sharedlibrary
17746 @item sharedlibrary @var{regex}
17747 @itemx share @var{regex}
17748 Load shared object library symbols for files matching a
17749 Unix regular expression.
17750 As with files loaded automatically, it only loads shared libraries
17751 required by your program for a core file or after typing @code{run}. If
17752 @var{regex} is omitted all shared libraries required by your program are
17755 @item nosharedlibrary
17756 @kindex nosharedlibrary
17757 @cindex unload symbols from shared libraries
17758 Unload all shared object library symbols. This discards all symbols
17759 that have been loaded from all shared libraries. Symbols from shared
17760 libraries that were loaded by explicit user requests are not
17764 Sometimes you may wish that @value{GDBN} stops and gives you control
17765 when any of shared library events happen. The best way to do this is
17766 to use @code{catch load} and @code{catch unload} (@pxref{Set
17769 @value{GDBN} also supports the the @code{set stop-on-solib-events}
17770 command for this. This command exists for historical reasons. It is
17771 less useful than setting a catchpoint, because it does not allow for
17772 conditions or commands as a catchpoint does.
17775 @item set stop-on-solib-events
17776 @kindex set stop-on-solib-events
17777 This command controls whether @value{GDBN} should give you control
17778 when the dynamic linker notifies it about some shared library event.
17779 The most common event of interest is loading or unloading of a new
17782 @item show stop-on-solib-events
17783 @kindex show stop-on-solib-events
17784 Show whether @value{GDBN} stops and gives you control when shared
17785 library events happen.
17788 Shared libraries are also supported in many cross or remote debugging
17789 configurations. @value{GDBN} needs to have access to the target's libraries;
17790 this can be accomplished either by providing copies of the libraries
17791 on the host system, or by asking @value{GDBN} to automatically retrieve the
17792 libraries from the target. If copies of the target libraries are
17793 provided, they need to be the same as the target libraries, although the
17794 copies on the target can be stripped as long as the copies on the host are
17797 @cindex where to look for shared libraries
17798 For remote debugging, you need to tell @value{GDBN} where the target
17799 libraries are, so that it can load the correct copies---otherwise, it
17800 may try to load the host's libraries. @value{GDBN} has two variables
17801 to specify the search directories for target libraries.
17804 @cindex prefix for shared library file names
17805 @cindex system root, alternate
17806 @kindex set solib-absolute-prefix
17807 @kindex set sysroot
17808 @item set sysroot @var{path}
17809 Use @var{path} as the system root for the program being debugged. Any
17810 absolute shared library paths will be prefixed with @var{path}; many
17811 runtime loaders store the absolute paths to the shared library in the
17812 target program's memory. If you use @code{set sysroot} to find shared
17813 libraries, they need to be laid out in the same way that they are on
17814 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
17817 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
17818 retrieve the target libraries from the remote system. This is only
17819 supported when using a remote target that supports the @code{remote get}
17820 command (@pxref{File Transfer,,Sending files to a remote system}).
17821 The part of @var{path} following the initial @file{remote:}
17822 (if present) is used as system root prefix on the remote file system.
17823 @footnote{If you want to specify a local system root using a directory
17824 that happens to be named @file{remote:}, you need to use some equivalent
17825 variant of the name like @file{./remote:}.}
17827 For targets with an MS-DOS based filesystem, such as MS-Windows and
17828 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
17829 absolute file name with @var{path}. But first, on Unix hosts,
17830 @value{GDBN} converts all backslash directory separators into forward
17831 slashes, because the backslash is not a directory separator on Unix:
17834 c:\foo\bar.dll @result{} c:/foo/bar.dll
17837 Then, @value{GDBN} attempts prefixing the target file name with
17838 @var{path}, and looks for the resulting file name in the host file
17842 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
17845 If that does not find the shared library, @value{GDBN} tries removing
17846 the @samp{:} character from the drive spec, both for convenience, and,
17847 for the case of the host file system not supporting file names with
17851 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
17854 This makes it possible to have a system root that mirrors a target
17855 with more than one drive. E.g., you may want to setup your local
17856 copies of the target system shared libraries like so (note @samp{c} vs
17860 @file{/path/to/sysroot/c/sys/bin/foo.dll}
17861 @file{/path/to/sysroot/c/sys/bin/bar.dll}
17862 @file{/path/to/sysroot/z/sys/bin/bar.dll}
17866 and point the system root at @file{/path/to/sysroot}, so that
17867 @value{GDBN} can find the correct copies of both
17868 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
17870 If that still does not find the shared library, @value{GDBN} tries
17871 removing the whole drive spec from the target file name:
17874 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
17877 This last lookup makes it possible to not care about the drive name,
17878 if you don't want or need to.
17880 The @code{set solib-absolute-prefix} command is an alias for @code{set
17883 @cindex default system root
17884 @cindex @samp{--with-sysroot}
17885 You can set the default system root by using the configure-time
17886 @samp{--with-sysroot} option. If the system root is inside
17887 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
17888 @samp{--exec-prefix}), then the default system root will be updated
17889 automatically if the installed @value{GDBN} is moved to a new
17892 @kindex show sysroot
17894 Display the current shared library prefix.
17896 @kindex set solib-search-path
17897 @item set solib-search-path @var{path}
17898 If this variable is set, @var{path} is a colon-separated list of
17899 directories to search for shared libraries. @samp{solib-search-path}
17900 is used after @samp{sysroot} fails to locate the library, or if the
17901 path to the library is relative instead of absolute. If you want to
17902 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
17903 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
17904 finding your host's libraries. @samp{sysroot} is preferred; setting
17905 it to a nonexistent directory may interfere with automatic loading
17906 of shared library symbols.
17908 @kindex show solib-search-path
17909 @item show solib-search-path
17910 Display the current shared library search path.
17912 @cindex DOS file-name semantics of file names.
17913 @kindex set target-file-system-kind (unix|dos-based|auto)
17914 @kindex show target-file-system-kind
17915 @item set target-file-system-kind @var{kind}
17916 Set assumed file system kind for target reported file names.
17918 Shared library file names as reported by the target system may not
17919 make sense as is on the system @value{GDBN} is running on. For
17920 example, when remote debugging a target that has MS-DOS based file
17921 system semantics, from a Unix host, the target may be reporting to
17922 @value{GDBN} a list of loaded shared libraries with file names such as
17923 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
17924 drive letters, so the @samp{c:\} prefix is not normally understood as
17925 indicating an absolute file name, and neither is the backslash
17926 normally considered a directory separator character. In that case,
17927 the native file system would interpret this whole absolute file name
17928 as a relative file name with no directory components. This would make
17929 it impossible to point @value{GDBN} at a copy of the remote target's
17930 shared libraries on the host using @code{set sysroot}, and impractical
17931 with @code{set solib-search-path}. Setting
17932 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
17933 to interpret such file names similarly to how the target would, and to
17934 map them to file names valid on @value{GDBN}'s native file system
17935 semantics. The value of @var{kind} can be @code{"auto"}, in addition
17936 to one of the supported file system kinds. In that case, @value{GDBN}
17937 tries to determine the appropriate file system variant based on the
17938 current target's operating system (@pxref{ABI, ,Configuring the
17939 Current ABI}). The supported file system settings are:
17943 Instruct @value{GDBN} to assume the target file system is of Unix
17944 kind. Only file names starting the forward slash (@samp{/}) character
17945 are considered absolute, and the directory separator character is also
17949 Instruct @value{GDBN} to assume the target file system is DOS based.
17950 File names starting with either a forward slash, or a drive letter
17951 followed by a colon (e.g., @samp{c:}), are considered absolute, and
17952 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
17953 considered directory separators.
17956 Instruct @value{GDBN} to use the file system kind associated with the
17957 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
17958 This is the default.
17962 @cindex file name canonicalization
17963 @cindex base name differences
17964 When processing file names provided by the user, @value{GDBN}
17965 frequently needs to compare them to the file names recorded in the
17966 program's debug info. Normally, @value{GDBN} compares just the
17967 @dfn{base names} of the files as strings, which is reasonably fast
17968 even for very large programs. (The base name of a file is the last
17969 portion of its name, after stripping all the leading directories.)
17970 This shortcut in comparison is based upon the assumption that files
17971 cannot have more than one base name. This is usually true, but
17972 references to files that use symlinks or similar filesystem
17973 facilities violate that assumption. If your program records files
17974 using such facilities, or if you provide file names to @value{GDBN}
17975 using symlinks etc., you can set @code{basenames-may-differ} to
17976 @code{true} to instruct @value{GDBN} to completely canonicalize each
17977 pair of file names it needs to compare. This will make file-name
17978 comparisons accurate, but at a price of a significant slowdown.
17981 @item set basenames-may-differ
17982 @kindex set basenames-may-differ
17983 Set whether a source file may have multiple base names.
17985 @item show basenames-may-differ
17986 @kindex show basenames-may-differ
17987 Show whether a source file may have multiple base names.
17990 @node Separate Debug Files
17991 @section Debugging Information in Separate Files
17992 @cindex separate debugging information files
17993 @cindex debugging information in separate files
17994 @cindex @file{.debug} subdirectories
17995 @cindex debugging information directory, global
17996 @cindex global debugging information directories
17997 @cindex build ID, and separate debugging files
17998 @cindex @file{.build-id} directory
18000 @value{GDBN} allows you to put a program's debugging information in a
18001 file separate from the executable itself, in a way that allows
18002 @value{GDBN} to find and load the debugging information automatically.
18003 Since debugging information can be very large---sometimes larger
18004 than the executable code itself---some systems distribute debugging
18005 information for their executables in separate files, which users can
18006 install only when they need to debug a problem.
18008 @value{GDBN} supports two ways of specifying the separate debug info
18013 The executable contains a @dfn{debug link} that specifies the name of
18014 the separate debug info file. The separate debug file's name is
18015 usually @file{@var{executable}.debug}, where @var{executable} is the
18016 name of the corresponding executable file without leading directories
18017 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
18018 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
18019 checksum for the debug file, which @value{GDBN} uses to validate that
18020 the executable and the debug file came from the same build.
18023 The executable contains a @dfn{build ID}, a unique bit string that is
18024 also present in the corresponding debug info file. (This is supported
18025 only on some operating systems, notably those which use the ELF format
18026 for binary files and the @sc{gnu} Binutils.) For more details about
18027 this feature, see the description of the @option{--build-id}
18028 command-line option in @ref{Options, , Command Line Options, ld.info,
18029 The GNU Linker}. The debug info file's name is not specified
18030 explicitly by the build ID, but can be computed from the build ID, see
18034 Depending on the way the debug info file is specified, @value{GDBN}
18035 uses two different methods of looking for the debug file:
18039 For the ``debug link'' method, @value{GDBN} looks up the named file in
18040 the directory of the executable file, then in a subdirectory of that
18041 directory named @file{.debug}, and finally under each one of the global debug
18042 directories, in a subdirectory whose name is identical to the leading
18043 directories of the executable's absolute file name.
18046 For the ``build ID'' method, @value{GDBN} looks in the
18047 @file{.build-id} subdirectory of each one of the global debug directories for
18048 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
18049 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
18050 are the rest of the bit string. (Real build ID strings are 32 or more
18051 hex characters, not 10.)
18054 So, for example, suppose you ask @value{GDBN} to debug
18055 @file{/usr/bin/ls}, which has a debug link that specifies the
18056 file @file{ls.debug}, and a build ID whose value in hex is
18057 @code{abcdef1234}. If the list of the global debug directories includes
18058 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
18059 debug information files, in the indicated order:
18063 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
18065 @file{/usr/bin/ls.debug}
18067 @file{/usr/bin/.debug/ls.debug}
18069 @file{/usr/lib/debug/usr/bin/ls.debug}.
18072 @anchor{debug-file-directory}
18073 Global debugging info directories default to what is set by @value{GDBN}
18074 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
18075 you can also set the global debugging info directories, and view the list
18076 @value{GDBN} is currently using.
18080 @kindex set debug-file-directory
18081 @item set debug-file-directory @var{directories}
18082 Set the directories which @value{GDBN} searches for separate debugging
18083 information files to @var{directory}. Multiple path components can be set
18084 concatenating them by a path separator.
18086 @kindex show debug-file-directory
18087 @item show debug-file-directory
18088 Show the directories @value{GDBN} searches for separate debugging
18093 @cindex @code{.gnu_debuglink} sections
18094 @cindex debug link sections
18095 A debug link is a special section of the executable file named
18096 @code{.gnu_debuglink}. The section must contain:
18100 A filename, with any leading directory components removed, followed by
18103 zero to three bytes of padding, as needed to reach the next four-byte
18104 boundary within the section, and
18106 a four-byte CRC checksum, stored in the same endianness used for the
18107 executable file itself. The checksum is computed on the debugging
18108 information file's full contents by the function given below, passing
18109 zero as the @var{crc} argument.
18112 Any executable file format can carry a debug link, as long as it can
18113 contain a section named @code{.gnu_debuglink} with the contents
18116 @cindex @code{.note.gnu.build-id} sections
18117 @cindex build ID sections
18118 The build ID is a special section in the executable file (and in other
18119 ELF binary files that @value{GDBN} may consider). This section is
18120 often named @code{.note.gnu.build-id}, but that name is not mandatory.
18121 It contains unique identification for the built files---the ID remains
18122 the same across multiple builds of the same build tree. The default
18123 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
18124 content for the build ID string. The same section with an identical
18125 value is present in the original built binary with symbols, in its
18126 stripped variant, and in the separate debugging information file.
18128 The debugging information file itself should be an ordinary
18129 executable, containing a full set of linker symbols, sections, and
18130 debugging information. The sections of the debugging information file
18131 should have the same names, addresses, and sizes as the original file,
18132 but they need not contain any data---much like a @code{.bss} section
18133 in an ordinary executable.
18135 The @sc{gnu} binary utilities (Binutils) package includes the
18136 @samp{objcopy} utility that can produce
18137 the separated executable / debugging information file pairs using the
18138 following commands:
18141 @kbd{objcopy --only-keep-debug foo foo.debug}
18146 These commands remove the debugging
18147 information from the executable file @file{foo} and place it in the file
18148 @file{foo.debug}. You can use the first, second or both methods to link the
18153 The debug link method needs the following additional command to also leave
18154 behind a debug link in @file{foo}:
18157 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
18160 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
18161 a version of the @code{strip} command such that the command @kbd{strip foo -f
18162 foo.debug} has the same functionality as the two @code{objcopy} commands and
18163 the @code{ln -s} command above, together.
18166 Build ID gets embedded into the main executable using @code{ld --build-id} or
18167 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
18168 compatibility fixes for debug files separation are present in @sc{gnu} binary
18169 utilities (Binutils) package since version 2.18.
18174 @cindex CRC algorithm definition
18175 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
18176 IEEE 802.3 using the polynomial:
18178 @c TexInfo requires naked braces for multi-digit exponents for Tex
18179 @c output, but this causes HTML output to barf. HTML has to be set using
18180 @c raw commands. So we end up having to specify this equation in 2
18185 <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>
18186 + <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
18192 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
18193 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
18197 The function is computed byte at a time, taking the least
18198 significant bit of each byte first. The initial pattern
18199 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
18200 the final result is inverted to ensure trailing zeros also affect the
18203 @emph{Note:} This is the same CRC polynomial as used in handling the
18204 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
18205 However in the case of the Remote Serial Protocol, the CRC is computed
18206 @emph{most} significant bit first, and the result is not inverted, so
18207 trailing zeros have no effect on the CRC value.
18209 To complete the description, we show below the code of the function
18210 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
18211 initially supplied @code{crc} argument means that an initial call to
18212 this function passing in zero will start computing the CRC using
18215 @kindex gnu_debuglink_crc32
18218 gnu_debuglink_crc32 (unsigned long crc,
18219 unsigned char *buf, size_t len)
18221 static const unsigned long crc32_table[256] =
18223 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
18224 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
18225 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
18226 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
18227 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
18228 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
18229 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
18230 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
18231 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
18232 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
18233 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
18234 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
18235 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
18236 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
18237 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
18238 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
18239 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
18240 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
18241 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
18242 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
18243 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
18244 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
18245 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
18246 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
18247 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
18248 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
18249 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
18250 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
18251 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
18252 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
18253 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
18254 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
18255 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
18256 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
18257 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
18258 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
18259 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
18260 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
18261 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
18262 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
18263 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
18264 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
18265 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
18266 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
18267 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
18268 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
18269 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
18270 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
18271 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
18272 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
18273 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
18276 unsigned char *end;
18278 crc = ~crc & 0xffffffff;
18279 for (end = buf + len; buf < end; ++buf)
18280 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
18281 return ~crc & 0xffffffff;
18286 This computation does not apply to the ``build ID'' method.
18288 @node MiniDebugInfo
18289 @section Debugging information in a special section
18290 @cindex separate debug sections
18291 @cindex @samp{.gnu_debugdata} section
18293 Some systems ship pre-built executables and libraries that have a
18294 special @samp{.gnu_debugdata} section. This feature is called
18295 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
18296 is used to supply extra symbols for backtraces.
18298 The intent of this section is to provide extra minimal debugging
18299 information for use in simple backtraces. It is not intended to be a
18300 replacement for full separate debugging information (@pxref{Separate
18301 Debug Files}). The example below shows the intended use; however,
18302 @value{GDBN} does not currently put restrictions on what sort of
18303 debugging information might be included in the section.
18305 @value{GDBN} has support for this extension. If the section exists,
18306 then it is used provided that no other source of debugging information
18307 can be found, and that @value{GDBN} was configured with LZMA support.
18309 This section can be easily created using @command{objcopy} and other
18310 standard utilities:
18313 # Extract the dynamic symbols from the main binary, there is no need
18314 # to also have these in the normal symbol table.
18315 nm -D @var{binary} --format=posix --defined-only \
18316 | awk '@{ print $1 @}' | sort > dynsyms
18318 # Extract all the text (i.e. function) symbols from the debuginfo.
18319 # (Note that we actually also accept "D" symbols, for the benefit
18320 # of platforms like PowerPC64 that use function descriptors.)
18321 nm @var{binary} --format=posix --defined-only \
18322 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
18325 # Keep all the function symbols not already in the dynamic symbol
18327 comm -13 dynsyms funcsyms > keep_symbols
18329 # Separate full debug info into debug binary.
18330 objcopy --only-keep-debug @var{binary} debug
18332 # Copy the full debuginfo, keeping only a minimal set of symbols and
18333 # removing some unnecessary sections.
18334 objcopy -S --remove-section .gdb_index --remove-section .comment \
18335 --keep-symbols=keep_symbols debug mini_debuginfo
18337 # Drop the full debug info from the original binary.
18338 strip --strip-all -R .comment @var{binary}
18340 # Inject the compressed data into the .gnu_debugdata section of the
18343 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
18347 @section Index Files Speed Up @value{GDBN}
18348 @cindex index files
18349 @cindex @samp{.gdb_index} section
18351 When @value{GDBN} finds a symbol file, it scans the symbols in the
18352 file in order to construct an internal symbol table. This lets most
18353 @value{GDBN} operations work quickly---at the cost of a delay early
18354 on. For large programs, this delay can be quite lengthy, so
18355 @value{GDBN} provides a way to build an index, which speeds up
18358 The index is stored as a section in the symbol file. @value{GDBN} can
18359 write the index to a file, then you can put it into the symbol file
18360 using @command{objcopy}.
18362 To create an index file, use the @code{save gdb-index} command:
18365 @item save gdb-index @var{directory}
18366 @kindex save gdb-index
18367 Create an index file for each symbol file currently known by
18368 @value{GDBN}. Each file is named after its corresponding symbol file,
18369 with @samp{.gdb-index} appended, and is written into the given
18373 Once you have created an index file you can merge it into your symbol
18374 file, here named @file{symfile}, using @command{objcopy}:
18377 $ objcopy --add-section .gdb_index=symfile.gdb-index \
18378 --set-section-flags .gdb_index=readonly symfile symfile
18381 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
18382 sections that have been deprecated. Usually they are deprecated because
18383 they are missing a new feature or have performance issues.
18384 To tell @value{GDBN} to use a deprecated index section anyway
18385 specify @code{set use-deprecated-index-sections on}.
18386 The default is @code{off}.
18387 This can speed up startup, but may result in some functionality being lost.
18388 @xref{Index Section Format}.
18390 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
18391 must be done before gdb reads the file. The following will not work:
18394 $ gdb -ex "set use-deprecated-index-sections on" <program>
18397 Instead you must do, for example,
18400 $ gdb -iex "set use-deprecated-index-sections on" <program>
18403 There are currently some limitation on indices. They only work when
18404 for DWARF debugging information, not stabs. And, they do not
18405 currently work for programs using Ada.
18407 @node Symbol Errors
18408 @section Errors Reading Symbol Files
18410 While reading a symbol file, @value{GDBN} occasionally encounters problems,
18411 such as symbol types it does not recognize, or known bugs in compiler
18412 output. By default, @value{GDBN} does not notify you of such problems, since
18413 they are relatively common and primarily of interest to people
18414 debugging compilers. If you are interested in seeing information
18415 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
18416 only one message about each such type of problem, no matter how many
18417 times the problem occurs; or you can ask @value{GDBN} to print more messages,
18418 to see how many times the problems occur, with the @code{set
18419 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
18422 The messages currently printed, and their meanings, include:
18425 @item inner block not inside outer block in @var{symbol}
18427 The symbol information shows where symbol scopes begin and end
18428 (such as at the start of a function or a block of statements). This
18429 error indicates that an inner scope block is not fully contained
18430 in its outer scope blocks.
18432 @value{GDBN} circumvents the problem by treating the inner block as if it had
18433 the same scope as the outer block. In the error message, @var{symbol}
18434 may be shown as ``@code{(don't know)}'' if the outer block is not a
18437 @item block at @var{address} out of order
18439 The symbol information for symbol scope blocks should occur in
18440 order of increasing addresses. This error indicates that it does not
18443 @value{GDBN} does not circumvent this problem, and has trouble
18444 locating symbols in the source file whose symbols it is reading. (You
18445 can often determine what source file is affected by specifying
18446 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
18449 @item bad block start address patched
18451 The symbol information for a symbol scope block has a start address
18452 smaller than the address of the preceding source line. This is known
18453 to occur in the SunOS 4.1.1 (and earlier) C compiler.
18455 @value{GDBN} circumvents the problem by treating the symbol scope block as
18456 starting on the previous source line.
18458 @item bad string table offset in symbol @var{n}
18461 Symbol number @var{n} contains a pointer into the string table which is
18462 larger than the size of the string table.
18464 @value{GDBN} circumvents the problem by considering the symbol to have the
18465 name @code{foo}, which may cause other problems if many symbols end up
18468 @item unknown symbol type @code{0x@var{nn}}
18470 The symbol information contains new data types that @value{GDBN} does
18471 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
18472 uncomprehended information, in hexadecimal.
18474 @value{GDBN} circumvents the error by ignoring this symbol information.
18475 This usually allows you to debug your program, though certain symbols
18476 are not accessible. If you encounter such a problem and feel like
18477 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
18478 on @code{complain}, then go up to the function @code{read_dbx_symtab}
18479 and examine @code{*bufp} to see the symbol.
18481 @item stub type has NULL name
18483 @value{GDBN} could not find the full definition for a struct or class.
18485 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
18486 The symbol information for a C@t{++} member function is missing some
18487 information that recent versions of the compiler should have output for
18490 @item info mismatch between compiler and debugger
18492 @value{GDBN} could not parse a type specification output by the compiler.
18497 @section GDB Data Files
18499 @cindex prefix for data files
18500 @value{GDBN} will sometimes read an auxiliary data file. These files
18501 are kept in a directory known as the @dfn{data directory}.
18503 You can set the data directory's name, and view the name @value{GDBN}
18504 is currently using.
18507 @kindex set data-directory
18508 @item set data-directory @var{directory}
18509 Set the directory which @value{GDBN} searches for auxiliary data files
18510 to @var{directory}.
18512 @kindex show data-directory
18513 @item show data-directory
18514 Show the directory @value{GDBN} searches for auxiliary data files.
18517 @cindex default data directory
18518 @cindex @samp{--with-gdb-datadir}
18519 You can set the default data directory by using the configure-time
18520 @samp{--with-gdb-datadir} option. If the data directory is inside
18521 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
18522 @samp{--exec-prefix}), then the default data directory will be updated
18523 automatically if the installed @value{GDBN} is moved to a new
18526 The data directory may also be specified with the
18527 @code{--data-directory} command line option.
18528 @xref{Mode Options}.
18531 @chapter Specifying a Debugging Target
18533 @cindex debugging target
18534 A @dfn{target} is the execution environment occupied by your program.
18536 Often, @value{GDBN} runs in the same host environment as your program;
18537 in that case, the debugging target is specified as a side effect when
18538 you use the @code{file} or @code{core} commands. When you need more
18539 flexibility---for example, running @value{GDBN} on a physically separate
18540 host, or controlling a standalone system over a serial port or a
18541 realtime system over a TCP/IP connection---you can use the @code{target}
18542 command to specify one of the target types configured for @value{GDBN}
18543 (@pxref{Target Commands, ,Commands for Managing Targets}).
18545 @cindex target architecture
18546 It is possible to build @value{GDBN} for several different @dfn{target
18547 architectures}. When @value{GDBN} is built like that, you can choose
18548 one of the available architectures with the @kbd{set architecture}
18552 @kindex set architecture
18553 @kindex show architecture
18554 @item set architecture @var{arch}
18555 This command sets the current target architecture to @var{arch}. The
18556 value of @var{arch} can be @code{"auto"}, in addition to one of the
18557 supported architectures.
18559 @item show architecture
18560 Show the current target architecture.
18562 @item set processor
18564 @kindex set processor
18565 @kindex show processor
18566 These are alias commands for, respectively, @code{set architecture}
18567 and @code{show architecture}.
18571 * Active Targets:: Active targets
18572 * Target Commands:: Commands for managing targets
18573 * Byte Order:: Choosing target byte order
18576 @node Active Targets
18577 @section Active Targets
18579 @cindex stacking targets
18580 @cindex active targets
18581 @cindex multiple targets
18583 There are multiple classes of targets such as: processes, executable files or
18584 recording sessions. Core files belong to the process class, making core file
18585 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
18586 on multiple active targets, one in each class. This allows you to (for
18587 example) start a process and inspect its activity, while still having access to
18588 the executable file after the process finishes. Or if you start process
18589 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
18590 presented a virtual layer of the recording target, while the process target
18591 remains stopped at the chronologically last point of the process execution.
18593 Use the @code{core-file} and @code{exec-file} commands to select a new core
18594 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
18595 specify as a target a process that is already running, use the @code{attach}
18596 command (@pxref{Attach, ,Debugging an Already-running Process}).
18598 @node Target Commands
18599 @section Commands for Managing Targets
18602 @item target @var{type} @var{parameters}
18603 Connects the @value{GDBN} host environment to a target machine or
18604 process. A target is typically a protocol for talking to debugging
18605 facilities. You use the argument @var{type} to specify the type or
18606 protocol of the target machine.
18608 Further @var{parameters} are interpreted by the target protocol, but
18609 typically include things like device names or host names to connect
18610 with, process numbers, and baud rates.
18612 The @code{target} command does not repeat if you press @key{RET} again
18613 after executing the command.
18615 @kindex help target
18617 Displays the names of all targets available. To display targets
18618 currently selected, use either @code{info target} or @code{info files}
18619 (@pxref{Files, ,Commands to Specify Files}).
18621 @item help target @var{name}
18622 Describe a particular target, including any parameters necessary to
18625 @kindex set gnutarget
18626 @item set gnutarget @var{args}
18627 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
18628 knows whether it is reading an @dfn{executable},
18629 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
18630 with the @code{set gnutarget} command. Unlike most @code{target} commands,
18631 with @code{gnutarget} the @code{target} refers to a program, not a machine.
18634 @emph{Warning:} To specify a file format with @code{set gnutarget},
18635 you must know the actual BFD name.
18639 @xref{Files, , Commands to Specify Files}.
18641 @kindex show gnutarget
18642 @item show gnutarget
18643 Use the @code{show gnutarget} command to display what file format
18644 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
18645 @value{GDBN} will determine the file format for each file automatically,
18646 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
18649 @cindex common targets
18650 Here are some common targets (available, or not, depending on the GDB
18655 @item target exec @var{program}
18656 @cindex executable file target
18657 An executable file. @samp{target exec @var{program}} is the same as
18658 @samp{exec-file @var{program}}.
18660 @item target core @var{filename}
18661 @cindex core dump file target
18662 A core dump file. @samp{target core @var{filename}} is the same as
18663 @samp{core-file @var{filename}}.
18665 @item target remote @var{medium}
18666 @cindex remote target
18667 A remote system connected to @value{GDBN} via a serial line or network
18668 connection. This command tells @value{GDBN} to use its own remote
18669 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
18671 For example, if you have a board connected to @file{/dev/ttya} on the
18672 machine running @value{GDBN}, you could say:
18675 target remote /dev/ttya
18678 @code{target remote} supports the @code{load} command. This is only
18679 useful if you have some other way of getting the stub to the target
18680 system, and you can put it somewhere in memory where it won't get
18681 clobbered by the download.
18683 @item target sim @r{[}@var{simargs}@r{]} @dots{}
18684 @cindex built-in simulator target
18685 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
18693 works; however, you cannot assume that a specific memory map, device
18694 drivers, or even basic I/O is available, although some simulators do
18695 provide these. For info about any processor-specific simulator details,
18696 see the appropriate section in @ref{Embedded Processors, ,Embedded
18699 @item target native
18700 @cindex native target
18701 Setup for local/native process debugging. Useful to make the
18702 @code{run} command spawn native processes (likewise @code{attach},
18703 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
18704 (@pxref{set auto-connect-native-target}).
18708 Different targets are available on different configurations of @value{GDBN};
18709 your configuration may have more or fewer targets.
18711 Many remote targets require you to download the executable's code once
18712 you've successfully established a connection. You may wish to control
18713 various aspects of this process.
18718 @kindex set hash@r{, for remote monitors}
18719 @cindex hash mark while downloading
18720 This command controls whether a hash mark @samp{#} is displayed while
18721 downloading a file to the remote monitor. If on, a hash mark is
18722 displayed after each S-record is successfully downloaded to the
18726 @kindex show hash@r{, for remote monitors}
18727 Show the current status of displaying the hash mark.
18729 @item set debug monitor
18730 @kindex set debug monitor
18731 @cindex display remote monitor communications
18732 Enable or disable display of communications messages between
18733 @value{GDBN} and the remote monitor.
18735 @item show debug monitor
18736 @kindex show debug monitor
18737 Show the current status of displaying communications between
18738 @value{GDBN} and the remote monitor.
18743 @kindex load @var{filename}
18744 @item load @var{filename}
18746 Depending on what remote debugging facilities are configured into
18747 @value{GDBN}, the @code{load} command may be available. Where it exists, it
18748 is meant to make @var{filename} (an executable) available for debugging
18749 on the remote system---by downloading, or dynamic linking, for example.
18750 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
18751 the @code{add-symbol-file} command.
18753 If your @value{GDBN} does not have a @code{load} command, attempting to
18754 execute it gets the error message ``@code{You can't do that when your
18755 target is @dots{}}''
18757 The file is loaded at whatever address is specified in the executable.
18758 For some object file formats, you can specify the load address when you
18759 link the program; for other formats, like a.out, the object file format
18760 specifies a fixed address.
18761 @c FIXME! This would be a good place for an xref to the GNU linker doc.
18763 Depending on the remote side capabilities, @value{GDBN} may be able to
18764 load programs into flash memory.
18766 @code{load} does not repeat if you press @key{RET} again after using it.
18770 @section Choosing Target Byte Order
18772 @cindex choosing target byte order
18773 @cindex target byte order
18775 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
18776 offer the ability to run either big-endian or little-endian byte
18777 orders. Usually the executable or symbol will include a bit to
18778 designate the endian-ness, and you will not need to worry about
18779 which to use. However, you may still find it useful to adjust
18780 @value{GDBN}'s idea of processor endian-ness manually.
18784 @item set endian big
18785 Instruct @value{GDBN} to assume the target is big-endian.
18787 @item set endian little
18788 Instruct @value{GDBN} to assume the target is little-endian.
18790 @item set endian auto
18791 Instruct @value{GDBN} to use the byte order associated with the
18795 Display @value{GDBN}'s current idea of the target byte order.
18799 Note that these commands merely adjust interpretation of symbolic
18800 data on the host, and that they have absolutely no effect on the
18804 @node Remote Debugging
18805 @chapter Debugging Remote Programs
18806 @cindex remote debugging
18808 If you are trying to debug a program running on a machine that cannot run
18809 @value{GDBN} in the usual way, it is often useful to use remote debugging.
18810 For example, you might use remote debugging on an operating system kernel,
18811 or on a small system which does not have a general purpose operating system
18812 powerful enough to run a full-featured debugger.
18814 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
18815 to make this work with particular debugging targets. In addition,
18816 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
18817 but not specific to any particular target system) which you can use if you
18818 write the remote stubs---the code that runs on the remote system to
18819 communicate with @value{GDBN}.
18821 Other remote targets may be available in your
18822 configuration of @value{GDBN}; use @code{help target} to list them.
18825 * Connecting:: Connecting to a remote target
18826 * File Transfer:: Sending files to a remote system
18827 * Server:: Using the gdbserver program
18828 * Remote Configuration:: Remote configuration
18829 * Remote Stub:: Implementing a remote stub
18833 @section Connecting to a Remote Target
18835 On the @value{GDBN} host machine, you will need an unstripped copy of
18836 your program, since @value{GDBN} needs symbol and debugging information.
18837 Start up @value{GDBN} as usual, using the name of the local copy of your
18838 program as the first argument.
18840 @cindex @code{target remote}
18841 @value{GDBN} can communicate with the target over a serial line, or
18842 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
18843 each case, @value{GDBN} uses the same protocol for debugging your
18844 program; only the medium carrying the debugging packets varies. The
18845 @code{target remote} command establishes a connection to the target.
18846 Its arguments indicate which medium to use:
18850 @item target remote @var{serial-device}
18851 @cindex serial line, @code{target remote}
18852 Use @var{serial-device} to communicate with the target. For example,
18853 to use a serial line connected to the device named @file{/dev/ttyb}:
18856 target remote /dev/ttyb
18859 If you're using a serial line, you may want to give @value{GDBN} the
18860 @samp{--baud} option, or use the @code{set serial baud} command
18861 (@pxref{Remote Configuration, set serial baud}) before the
18862 @code{target} command.
18864 @item target remote @code{@var{host}:@var{port}}
18865 @itemx target remote @code{tcp:@var{host}:@var{port}}
18866 @cindex @acronym{TCP} port, @code{target remote}
18867 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
18868 The @var{host} may be either a host name or a numeric @acronym{IP}
18869 address; @var{port} must be a decimal number. The @var{host} could be
18870 the target machine itself, if it is directly connected to the net, or
18871 it might be a terminal server which in turn has a serial line to the
18874 For example, to connect to port 2828 on a terminal server named
18878 target remote manyfarms:2828
18881 If your remote target is actually running on the same machine as your
18882 debugger session (e.g.@: a simulator for your target running on the
18883 same host), you can omit the hostname. For example, to connect to
18884 port 1234 on your local machine:
18887 target remote :1234
18891 Note that the colon is still required here.
18893 @item target remote @code{udp:@var{host}:@var{port}}
18894 @cindex @acronym{UDP} port, @code{target remote}
18895 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
18896 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
18899 target remote udp:manyfarms:2828
18902 When using a @acronym{UDP} connection for remote debugging, you should
18903 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
18904 can silently drop packets on busy or unreliable networks, which will
18905 cause havoc with your debugging session.
18907 @item target remote | @var{command}
18908 @cindex pipe, @code{target remote} to
18909 Run @var{command} in the background and communicate with it using a
18910 pipe. The @var{command} is a shell command, to be parsed and expanded
18911 by the system's command shell, @code{/bin/sh}; it should expect remote
18912 protocol packets on its standard input, and send replies on its
18913 standard output. You could use this to run a stand-alone simulator
18914 that speaks the remote debugging protocol, to make net connections
18915 using programs like @code{ssh}, or for other similar tricks.
18917 If @var{command} closes its standard output (perhaps by exiting),
18918 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
18919 program has already exited, this will have no effect.)
18923 Once the connection has been established, you can use all the usual
18924 commands to examine and change data. The remote program is already
18925 running; you can use @kbd{step} and @kbd{continue}, and you do not
18926 need to use @kbd{run}.
18928 @cindex interrupting remote programs
18929 @cindex remote programs, interrupting
18930 Whenever @value{GDBN} is waiting for the remote program, if you type the
18931 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
18932 program. This may or may not succeed, depending in part on the hardware
18933 and the serial drivers the remote system uses. If you type the
18934 interrupt character once again, @value{GDBN} displays this prompt:
18937 Interrupted while waiting for the program.
18938 Give up (and stop debugging it)? (y or n)
18941 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
18942 (If you decide you want to try again later, you can use @samp{target
18943 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
18944 goes back to waiting.
18947 @kindex detach (remote)
18949 When you have finished debugging the remote program, you can use the
18950 @code{detach} command to release it from @value{GDBN} control.
18951 Detaching from the target normally resumes its execution, but the results
18952 will depend on your particular remote stub. After the @code{detach}
18953 command, @value{GDBN} is free to connect to another target.
18957 The @code{disconnect} command behaves like @code{detach}, except that
18958 the target is generally not resumed. It will wait for @value{GDBN}
18959 (this instance or another one) to connect and continue debugging. After
18960 the @code{disconnect} command, @value{GDBN} is again free to connect to
18963 @cindex send command to remote monitor
18964 @cindex extend @value{GDBN} for remote targets
18965 @cindex add new commands for external monitor
18967 @item monitor @var{cmd}
18968 This command allows you to send arbitrary commands directly to the
18969 remote monitor. Since @value{GDBN} doesn't care about the commands it
18970 sends like this, this command is the way to extend @value{GDBN}---you
18971 can add new commands that only the external monitor will understand
18975 @node File Transfer
18976 @section Sending files to a remote system
18977 @cindex remote target, file transfer
18978 @cindex file transfer
18979 @cindex sending files to remote systems
18981 Some remote targets offer the ability to transfer files over the same
18982 connection used to communicate with @value{GDBN}. This is convenient
18983 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
18984 running @code{gdbserver} over a network interface. For other targets,
18985 e.g.@: embedded devices with only a single serial port, this may be
18986 the only way to upload or download files.
18988 Not all remote targets support these commands.
18992 @item remote put @var{hostfile} @var{targetfile}
18993 Copy file @var{hostfile} from the host system (the machine running
18994 @value{GDBN}) to @var{targetfile} on the target system.
18997 @item remote get @var{targetfile} @var{hostfile}
18998 Copy file @var{targetfile} from the target system to @var{hostfile}
18999 on the host system.
19001 @kindex remote delete
19002 @item remote delete @var{targetfile}
19003 Delete @var{targetfile} from the target system.
19008 @section Using the @code{gdbserver} Program
19011 @cindex remote connection without stubs
19012 @code{gdbserver} is a control program for Unix-like systems, which
19013 allows you to connect your program with a remote @value{GDBN} via
19014 @code{target remote}---but without linking in the usual debugging stub.
19016 @code{gdbserver} is not a complete replacement for the debugging stubs,
19017 because it requires essentially the same operating-system facilities
19018 that @value{GDBN} itself does. In fact, a system that can run
19019 @code{gdbserver} to connect to a remote @value{GDBN} could also run
19020 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
19021 because it is a much smaller program than @value{GDBN} itself. It is
19022 also easier to port than all of @value{GDBN}, so you may be able to get
19023 started more quickly on a new system by using @code{gdbserver}.
19024 Finally, if you develop code for real-time systems, you may find that
19025 the tradeoffs involved in real-time operation make it more convenient to
19026 do as much development work as possible on another system, for example
19027 by cross-compiling. You can use @code{gdbserver} to make a similar
19028 choice for debugging.
19030 @value{GDBN} and @code{gdbserver} communicate via either a serial line
19031 or a TCP connection, using the standard @value{GDBN} remote serial
19035 @emph{Warning:} @code{gdbserver} does not have any built-in security.
19036 Do not run @code{gdbserver} connected to any public network; a
19037 @value{GDBN} connection to @code{gdbserver} provides access to the
19038 target system with the same privileges as the user running
19042 @subsection Running @code{gdbserver}
19043 @cindex arguments, to @code{gdbserver}
19044 @cindex @code{gdbserver}, command-line arguments
19046 Run @code{gdbserver} on the target system. You need a copy of the
19047 program you want to debug, including any libraries it requires.
19048 @code{gdbserver} does not need your program's symbol table, so you can
19049 strip the program if necessary to save space. @value{GDBN} on the host
19050 system does all the symbol handling.
19052 To use the server, you must tell it how to communicate with @value{GDBN};
19053 the name of your program; and the arguments for your program. The usual
19057 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
19060 @var{comm} is either a device name (to use a serial line), or a TCP
19061 hostname and portnumber, or @code{-} or @code{stdio} to use
19062 stdin/stdout of @code{gdbserver}.
19063 For example, to debug Emacs with the argument
19064 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
19068 target> gdbserver /dev/com1 emacs foo.txt
19071 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
19074 To use a TCP connection instead of a serial line:
19077 target> gdbserver host:2345 emacs foo.txt
19080 The only difference from the previous example is the first argument,
19081 specifying that you are communicating with the host @value{GDBN} via
19082 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
19083 expect a TCP connection from machine @samp{host} to local TCP port 2345.
19084 (Currently, the @samp{host} part is ignored.) You can choose any number
19085 you want for the port number as long as it does not conflict with any
19086 TCP ports already in use on the target system (for example, @code{23} is
19087 reserved for @code{telnet}).@footnote{If you choose a port number that
19088 conflicts with another service, @code{gdbserver} prints an error message
19089 and exits.} You must use the same port number with the host @value{GDBN}
19090 @code{target remote} command.
19092 The @code{stdio} connection is useful when starting @code{gdbserver}
19096 (gdb) target remote | ssh -T hostname gdbserver - hello
19099 The @samp{-T} option to ssh is provided because we don't need a remote pty,
19100 and we don't want escape-character handling. Ssh does this by default when
19101 a command is provided, the flag is provided to make it explicit.
19102 You could elide it if you want to.
19104 Programs started with stdio-connected gdbserver have @file{/dev/null} for
19105 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
19106 display through a pipe connected to gdbserver.
19107 Both @code{stdout} and @code{stderr} use the same pipe.
19109 @subsubsection Attaching to a Running Program
19110 @cindex attach to a program, @code{gdbserver}
19111 @cindex @option{--attach}, @code{gdbserver} option
19113 On some targets, @code{gdbserver} can also attach to running programs.
19114 This is accomplished via the @code{--attach} argument. The syntax is:
19117 target> gdbserver --attach @var{comm} @var{pid}
19120 @var{pid} is the process ID of a currently running process. It isn't necessary
19121 to point @code{gdbserver} at a binary for the running process.
19124 You can debug processes by name instead of process ID if your target has the
19125 @code{pidof} utility:
19128 target> gdbserver --attach @var{comm} `pidof @var{program}`
19131 In case more than one copy of @var{program} is running, or @var{program}
19132 has multiple threads, most versions of @code{pidof} support the
19133 @code{-s} option to only return the first process ID.
19135 @subsubsection Multi-Process Mode for @code{gdbserver}
19136 @cindex @code{gdbserver}, multiple processes
19137 @cindex multiple processes with @code{gdbserver}
19139 When you connect to @code{gdbserver} using @code{target remote},
19140 @code{gdbserver} debugs the specified program only once. When the
19141 program exits, or you detach from it, @value{GDBN} closes the connection
19142 and @code{gdbserver} exits.
19144 If you connect using @kbd{target extended-remote}, @code{gdbserver}
19145 enters multi-process mode. When the debugged program exits, or you
19146 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
19147 though no program is running. The @code{run} and @code{attach}
19148 commands instruct @code{gdbserver} to run or attach to a new program.
19149 The @code{run} command uses @code{set remote exec-file} (@pxref{set
19150 remote exec-file}) to select the program to run. Command line
19151 arguments are supported, except for wildcard expansion and I/O
19152 redirection (@pxref{Arguments}).
19154 @cindex @option{--multi}, @code{gdbserver} option
19155 To start @code{gdbserver} without supplying an initial command to run
19156 or process ID to attach, use the @option{--multi} command line option.
19157 Then you can connect using @kbd{target extended-remote} and start
19158 the program you want to debug.
19160 In multi-process mode @code{gdbserver} does not automatically exit unless you
19161 use the option @option{--once}. You can terminate it by using
19162 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
19163 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
19164 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
19165 @option{--multi} option to @code{gdbserver} has no influence on that.
19167 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
19169 This section applies only when @code{gdbserver} is run to listen on a TCP port.
19171 @code{gdbserver} normally terminates after all of its debugged processes have
19172 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
19173 extended-remote}, @code{gdbserver} stays running even with no processes left.
19174 @value{GDBN} normally terminates the spawned debugged process on its exit,
19175 which normally also terminates @code{gdbserver} in the @kbd{target remote}
19176 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
19177 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
19178 stays running even in the @kbd{target remote} mode.
19180 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
19181 Such reconnecting is useful for features like @ref{disconnected tracing}. For
19182 completeness, at most one @value{GDBN} can be connected at a time.
19184 @cindex @option{--once}, @code{gdbserver} option
19185 By default, @code{gdbserver} keeps the listening TCP port open, so that
19186 subsequent connections are possible. However, if you start @code{gdbserver}
19187 with the @option{--once} option, it will stop listening for any further
19188 connection attempts after connecting to the first @value{GDBN} session. This
19189 means no further connections to @code{gdbserver} will be possible after the
19190 first one. It also means @code{gdbserver} will terminate after the first
19191 connection with remote @value{GDBN} has closed, even for unexpectedly closed
19192 connections and even in the @kbd{target extended-remote} mode. The
19193 @option{--once} option allows reusing the same port number for connecting to
19194 multiple instances of @code{gdbserver} running on the same host, since each
19195 instance closes its port after the first connection.
19197 @anchor{Other Command-Line Arguments for gdbserver}
19198 @subsubsection Other Command-Line Arguments for @code{gdbserver}
19200 @cindex @option{--debug}, @code{gdbserver} option
19201 The @option{--debug} option tells @code{gdbserver} to display extra
19202 status information about the debugging process.
19203 @cindex @option{--remote-debug}, @code{gdbserver} option
19204 The @option{--remote-debug} option tells @code{gdbserver} to display
19205 remote protocol debug output. These options are intended for
19206 @code{gdbserver} development and for bug reports to the developers.
19208 @cindex @option{--debug-format}, @code{gdbserver} option
19209 The @option{--debug-format=option1[,option2,...]} option tells
19210 @code{gdbserver} to include additional information in each output.
19211 Possible options are:
19215 Turn off all extra information in debugging output.
19217 Turn on all extra information in debugging output.
19219 Include a timestamp in each line of debugging output.
19222 Options are processed in order. Thus, for example, if @option{none}
19223 appears last then no additional information is added to debugging output.
19225 @cindex @option{--wrapper}, @code{gdbserver} option
19226 The @option{--wrapper} option specifies a wrapper to launch programs
19227 for debugging. The option should be followed by the name of the
19228 wrapper, then any command-line arguments to pass to the wrapper, then
19229 @kbd{--} indicating the end of the wrapper arguments.
19231 @code{gdbserver} runs the specified wrapper program with a combined
19232 command line including the wrapper arguments, then the name of the
19233 program to debug, then any arguments to the program. The wrapper
19234 runs until it executes your program, and then @value{GDBN} gains control.
19236 You can use any program that eventually calls @code{execve} with
19237 its arguments as a wrapper. Several standard Unix utilities do
19238 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
19239 with @code{exec "$@@"} will also work.
19241 For example, you can use @code{env} to pass an environment variable to
19242 the debugged program, without setting the variable in @code{gdbserver}'s
19246 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
19249 @subsection Connecting to @code{gdbserver}
19251 Run @value{GDBN} on the host system.
19253 First make sure you have the necessary symbol files. Load symbols for
19254 your application using the @code{file} command before you connect. Use
19255 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
19256 was compiled with the correct sysroot using @code{--with-sysroot}).
19258 The symbol file and target libraries must exactly match the executable
19259 and libraries on the target, with one exception: the files on the host
19260 system should not be stripped, even if the files on the target system
19261 are. Mismatched or missing files will lead to confusing results
19262 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
19263 files may also prevent @code{gdbserver} from debugging multi-threaded
19266 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
19267 For TCP connections, you must start up @code{gdbserver} prior to using
19268 the @code{target remote} command. Otherwise you may get an error whose
19269 text depends on the host system, but which usually looks something like
19270 @samp{Connection refused}. Don't use the @code{load}
19271 command in @value{GDBN} when using @code{gdbserver}, since the program is
19272 already on the target.
19274 @subsection Monitor Commands for @code{gdbserver}
19275 @cindex monitor commands, for @code{gdbserver}
19276 @anchor{Monitor Commands for gdbserver}
19278 During a @value{GDBN} session using @code{gdbserver}, you can use the
19279 @code{monitor} command to send special requests to @code{gdbserver}.
19280 Here are the available commands.
19284 List the available monitor commands.
19286 @item monitor set debug 0
19287 @itemx monitor set debug 1
19288 Disable or enable general debugging messages.
19290 @item monitor set remote-debug 0
19291 @itemx monitor set remote-debug 1
19292 Disable or enable specific debugging messages associated with the remote
19293 protocol (@pxref{Remote Protocol}).
19295 @item monitor set debug-format option1@r{[},option2,...@r{]}
19296 Specify additional text to add to debugging messages.
19297 Possible options are:
19301 Turn off all extra information in debugging output.
19303 Turn on all extra information in debugging output.
19305 Include a timestamp in each line of debugging output.
19308 Options are processed in order. Thus, for example, if @option{none}
19309 appears last then no additional information is added to debugging output.
19311 @item monitor set libthread-db-search-path [PATH]
19312 @cindex gdbserver, search path for @code{libthread_db}
19313 When this command is issued, @var{path} is a colon-separated list of
19314 directories to search for @code{libthread_db} (@pxref{Threads,,set
19315 libthread-db-search-path}). If you omit @var{path},
19316 @samp{libthread-db-search-path} will be reset to its default value.
19318 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
19319 not supported in @code{gdbserver}.
19322 Tell gdbserver to exit immediately. This command should be followed by
19323 @code{disconnect} to close the debugging session. @code{gdbserver} will
19324 detach from any attached processes and kill any processes it created.
19325 Use @code{monitor exit} to terminate @code{gdbserver} at the end
19326 of a multi-process mode debug session.
19330 @subsection Tracepoints support in @code{gdbserver}
19331 @cindex tracepoints support in @code{gdbserver}
19333 On some targets, @code{gdbserver} supports tracepoints, fast
19334 tracepoints and static tracepoints.
19336 For fast or static tracepoints to work, a special library called the
19337 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
19338 This library is built and distributed as an integral part of
19339 @code{gdbserver}. In addition, support for static tracepoints
19340 requires building the in-process agent library with static tracepoints
19341 support. At present, the UST (LTTng Userspace Tracer,
19342 @url{http://lttng.org/ust}) tracing engine is supported. This support
19343 is automatically available if UST development headers are found in the
19344 standard include path when @code{gdbserver} is built, or if
19345 @code{gdbserver} was explicitly configured using @option{--with-ust}
19346 to point at such headers. You can explicitly disable the support
19347 using @option{--with-ust=no}.
19349 There are several ways to load the in-process agent in your program:
19352 @item Specifying it as dependency at link time
19354 You can link your program dynamically with the in-process agent
19355 library. On most systems, this is accomplished by adding
19356 @code{-linproctrace} to the link command.
19358 @item Using the system's preloading mechanisms
19360 You can force loading the in-process agent at startup time by using
19361 your system's support for preloading shared libraries. Many Unixes
19362 support the concept of preloading user defined libraries. In most
19363 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
19364 in the environment. See also the description of @code{gdbserver}'s
19365 @option{--wrapper} command line option.
19367 @item Using @value{GDBN} to force loading the agent at run time
19369 On some systems, you can force the inferior to load a shared library,
19370 by calling a dynamic loader function in the inferior that takes care
19371 of dynamically looking up and loading a shared library. On most Unix
19372 systems, the function is @code{dlopen}. You'll use the @code{call}
19373 command for that. For example:
19376 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
19379 Note that on most Unix systems, for the @code{dlopen} function to be
19380 available, the program needs to be linked with @code{-ldl}.
19383 On systems that have a userspace dynamic loader, like most Unix
19384 systems, when you connect to @code{gdbserver} using @code{target
19385 remote}, you'll find that the program is stopped at the dynamic
19386 loader's entry point, and no shared library has been loaded in the
19387 program's address space yet, including the in-process agent. In that
19388 case, before being able to use any of the fast or static tracepoints
19389 features, you need to let the loader run and load the shared
19390 libraries. The simplest way to do that is to run the program to the
19391 main procedure. E.g., if debugging a C or C@t{++} program, start
19392 @code{gdbserver} like so:
19395 $ gdbserver :9999 myprogram
19398 Start GDB and connect to @code{gdbserver} like so, and run to main:
19402 (@value{GDBP}) target remote myhost:9999
19403 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
19404 (@value{GDBP}) b main
19405 (@value{GDBP}) continue
19408 The in-process tracing agent library should now be loaded into the
19409 process; you can confirm it with the @code{info sharedlibrary}
19410 command, which will list @file{libinproctrace.so} as loaded in the
19411 process. You are now ready to install fast tracepoints, list static
19412 tracepoint markers, probe static tracepoints markers, and start
19415 @node Remote Configuration
19416 @section Remote Configuration
19419 @kindex show remote
19420 This section documents the configuration options available when
19421 debugging remote programs. For the options related to the File I/O
19422 extensions of the remote protocol, see @ref{system,
19423 system-call-allowed}.
19426 @item set remoteaddresssize @var{bits}
19427 @cindex address size for remote targets
19428 @cindex bits in remote address
19429 Set the maximum size of address in a memory packet to the specified
19430 number of bits. @value{GDBN} will mask off the address bits above
19431 that number, when it passes addresses to the remote target. The
19432 default value is the number of bits in the target's address.
19434 @item show remoteaddresssize
19435 Show the current value of remote address size in bits.
19437 @item set serial baud @var{n}
19438 @cindex baud rate for remote targets
19439 Set the baud rate for the remote serial I/O to @var{n} baud. The
19440 value is used to set the speed of the serial port used for debugging
19443 @item show serial baud
19444 Show the current speed of the remote connection.
19446 @item set remotebreak
19447 @cindex interrupt remote programs
19448 @cindex BREAK signal instead of Ctrl-C
19449 @anchor{set remotebreak}
19450 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
19451 when you type @kbd{Ctrl-c} to interrupt the program running
19452 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
19453 character instead. The default is off, since most remote systems
19454 expect to see @samp{Ctrl-C} as the interrupt signal.
19456 @item show remotebreak
19457 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
19458 interrupt the remote program.
19460 @item set remoteflow on
19461 @itemx set remoteflow off
19462 @kindex set remoteflow
19463 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
19464 on the serial port used to communicate to the remote target.
19466 @item show remoteflow
19467 @kindex show remoteflow
19468 Show the current setting of hardware flow control.
19470 @item set remotelogbase @var{base}
19471 Set the base (a.k.a.@: radix) of logging serial protocol
19472 communications to @var{base}. Supported values of @var{base} are:
19473 @code{ascii}, @code{octal}, and @code{hex}. The default is
19476 @item show remotelogbase
19477 Show the current setting of the radix for logging remote serial
19480 @item set remotelogfile @var{file}
19481 @cindex record serial communications on file
19482 Record remote serial communications on the named @var{file}. The
19483 default is not to record at all.
19485 @item show remotelogfile.
19486 Show the current setting of the file name on which to record the
19487 serial communications.
19489 @item set remotetimeout @var{num}
19490 @cindex timeout for serial communications
19491 @cindex remote timeout
19492 Set the timeout limit to wait for the remote target to respond to
19493 @var{num} seconds. The default is 2 seconds.
19495 @item show remotetimeout
19496 Show the current number of seconds to wait for the remote target
19499 @cindex limit hardware breakpoints and watchpoints
19500 @cindex remote target, limit break- and watchpoints
19501 @anchor{set remote hardware-watchpoint-limit}
19502 @anchor{set remote hardware-breakpoint-limit}
19503 @item set remote hardware-watchpoint-limit @var{limit}
19504 @itemx set remote hardware-breakpoint-limit @var{limit}
19505 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
19506 watchpoints. A limit of -1, the default, is treated as unlimited.
19508 @cindex limit hardware watchpoints length
19509 @cindex remote target, limit watchpoints length
19510 @anchor{set remote hardware-watchpoint-length-limit}
19511 @item set remote hardware-watchpoint-length-limit @var{limit}
19512 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
19513 a remote hardware watchpoint. A limit of -1, the default, is treated
19516 @item show remote hardware-watchpoint-length-limit
19517 Show the current limit (in bytes) of the maximum length of
19518 a remote hardware watchpoint.
19520 @item set remote exec-file @var{filename}
19521 @itemx show remote exec-file
19522 @anchor{set remote exec-file}
19523 @cindex executable file, for remote target
19524 Select the file used for @code{run} with @code{target
19525 extended-remote}. This should be set to a filename valid on the
19526 target system. If it is not set, the target will use a default
19527 filename (e.g.@: the last program run).
19529 @item set remote interrupt-sequence
19530 @cindex interrupt remote programs
19531 @cindex select Ctrl-C, BREAK or BREAK-g
19532 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
19533 @samp{BREAK-g} as the
19534 sequence to the remote target in order to interrupt the execution.
19535 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
19536 is high level of serial line for some certain time.
19537 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
19538 It is @code{BREAK} signal followed by character @code{g}.
19540 @item show interrupt-sequence
19541 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
19542 is sent by @value{GDBN} to interrupt the remote program.
19543 @code{BREAK-g} is BREAK signal followed by @code{g} and
19544 also known as Magic SysRq g.
19546 @item set remote interrupt-on-connect
19547 @cindex send interrupt-sequence on start
19548 Specify whether interrupt-sequence is sent to remote target when
19549 @value{GDBN} connects to it. This is mostly needed when you debug
19550 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
19551 which is known as Magic SysRq g in order to connect @value{GDBN}.
19553 @item show interrupt-on-connect
19554 Show whether interrupt-sequence is sent
19555 to remote target when @value{GDBN} connects to it.
19559 @item set tcp auto-retry on
19560 @cindex auto-retry, for remote TCP target
19561 Enable auto-retry for remote TCP connections. This is useful if the remote
19562 debugging agent is launched in parallel with @value{GDBN}; there is a race
19563 condition because the agent may not become ready to accept the connection
19564 before @value{GDBN} attempts to connect. When auto-retry is
19565 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
19566 to establish the connection using the timeout specified by
19567 @code{set tcp connect-timeout}.
19569 @item set tcp auto-retry off
19570 Do not auto-retry failed TCP connections.
19572 @item show tcp auto-retry
19573 Show the current auto-retry setting.
19575 @item set tcp connect-timeout @var{seconds}
19576 @itemx set tcp connect-timeout unlimited
19577 @cindex connection timeout, for remote TCP target
19578 @cindex timeout, for remote target connection
19579 Set the timeout for establishing a TCP connection to the remote target to
19580 @var{seconds}. The timeout affects both polling to retry failed connections
19581 (enabled by @code{set tcp auto-retry on}) and waiting for connections
19582 that are merely slow to complete, and represents an approximate cumulative
19583 value. If @var{seconds} is @code{unlimited}, there is no timeout and
19584 @value{GDBN} will keep attempting to establish a connection forever,
19585 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
19587 @item show tcp connect-timeout
19588 Show the current connection timeout setting.
19591 @cindex remote packets, enabling and disabling
19592 The @value{GDBN} remote protocol autodetects the packets supported by
19593 your debugging stub. If you need to override the autodetection, you
19594 can use these commands to enable or disable individual packets. Each
19595 packet can be set to @samp{on} (the remote target supports this
19596 packet), @samp{off} (the remote target does not support this packet),
19597 or @samp{auto} (detect remote target support for this packet). They
19598 all default to @samp{auto}. For more information about each packet,
19599 see @ref{Remote Protocol}.
19601 During normal use, you should not have to use any of these commands.
19602 If you do, that may be a bug in your remote debugging stub, or a bug
19603 in @value{GDBN}. You may want to report the problem to the
19604 @value{GDBN} developers.
19606 For each packet @var{name}, the command to enable or disable the
19607 packet is @code{set remote @var{name}-packet}. The available settings
19610 @multitable @columnfractions 0.28 0.32 0.25
19613 @tab Related Features
19615 @item @code{fetch-register}
19617 @tab @code{info registers}
19619 @item @code{set-register}
19623 @item @code{binary-download}
19625 @tab @code{load}, @code{set}
19627 @item @code{read-aux-vector}
19628 @tab @code{qXfer:auxv:read}
19629 @tab @code{info auxv}
19631 @item @code{symbol-lookup}
19632 @tab @code{qSymbol}
19633 @tab Detecting multiple threads
19635 @item @code{attach}
19636 @tab @code{vAttach}
19639 @item @code{verbose-resume}
19641 @tab Stepping or resuming multiple threads
19647 @item @code{software-breakpoint}
19651 @item @code{hardware-breakpoint}
19655 @item @code{write-watchpoint}
19659 @item @code{read-watchpoint}
19663 @item @code{access-watchpoint}
19667 @item @code{target-features}
19668 @tab @code{qXfer:features:read}
19669 @tab @code{set architecture}
19671 @item @code{library-info}
19672 @tab @code{qXfer:libraries:read}
19673 @tab @code{info sharedlibrary}
19675 @item @code{memory-map}
19676 @tab @code{qXfer:memory-map:read}
19677 @tab @code{info mem}
19679 @item @code{read-sdata-object}
19680 @tab @code{qXfer:sdata:read}
19681 @tab @code{print $_sdata}
19683 @item @code{read-spu-object}
19684 @tab @code{qXfer:spu:read}
19685 @tab @code{info spu}
19687 @item @code{write-spu-object}
19688 @tab @code{qXfer:spu:write}
19689 @tab @code{info spu}
19691 @item @code{read-siginfo-object}
19692 @tab @code{qXfer:siginfo:read}
19693 @tab @code{print $_siginfo}
19695 @item @code{write-siginfo-object}
19696 @tab @code{qXfer:siginfo:write}
19697 @tab @code{set $_siginfo}
19699 @item @code{threads}
19700 @tab @code{qXfer:threads:read}
19701 @tab @code{info threads}
19703 @item @code{get-thread-local-@*storage-address}
19704 @tab @code{qGetTLSAddr}
19705 @tab Displaying @code{__thread} variables
19707 @item @code{get-thread-information-block-address}
19708 @tab @code{qGetTIBAddr}
19709 @tab Display MS-Windows Thread Information Block.
19711 @item @code{search-memory}
19712 @tab @code{qSearch:memory}
19715 @item @code{supported-packets}
19716 @tab @code{qSupported}
19717 @tab Remote communications parameters
19719 @item @code{pass-signals}
19720 @tab @code{QPassSignals}
19721 @tab @code{handle @var{signal}}
19723 @item @code{program-signals}
19724 @tab @code{QProgramSignals}
19725 @tab @code{handle @var{signal}}
19727 @item @code{hostio-close-packet}
19728 @tab @code{vFile:close}
19729 @tab @code{remote get}, @code{remote put}
19731 @item @code{hostio-open-packet}
19732 @tab @code{vFile:open}
19733 @tab @code{remote get}, @code{remote put}
19735 @item @code{hostio-pread-packet}
19736 @tab @code{vFile:pread}
19737 @tab @code{remote get}, @code{remote put}
19739 @item @code{hostio-pwrite-packet}
19740 @tab @code{vFile:pwrite}
19741 @tab @code{remote get}, @code{remote put}
19743 @item @code{hostio-unlink-packet}
19744 @tab @code{vFile:unlink}
19745 @tab @code{remote delete}
19747 @item @code{hostio-readlink-packet}
19748 @tab @code{vFile:readlink}
19751 @item @code{noack-packet}
19752 @tab @code{QStartNoAckMode}
19753 @tab Packet acknowledgment
19755 @item @code{osdata}
19756 @tab @code{qXfer:osdata:read}
19757 @tab @code{info os}
19759 @item @code{query-attached}
19760 @tab @code{qAttached}
19761 @tab Querying remote process attach state.
19763 @item @code{trace-buffer-size}
19764 @tab @code{QTBuffer:size}
19765 @tab @code{set trace-buffer-size}
19767 @item @code{trace-status}
19768 @tab @code{qTStatus}
19769 @tab @code{tstatus}
19771 @item @code{traceframe-info}
19772 @tab @code{qXfer:traceframe-info:read}
19773 @tab Traceframe info
19775 @item @code{install-in-trace}
19776 @tab @code{InstallInTrace}
19777 @tab Install tracepoint in tracing
19779 @item @code{disable-randomization}
19780 @tab @code{QDisableRandomization}
19781 @tab @code{set disable-randomization}
19783 @item @code{conditional-breakpoints-packet}
19784 @tab @code{Z0 and Z1}
19785 @tab @code{Support for target-side breakpoint condition evaluation}
19787 @item @code{swbreak-feature}
19788 @tab @code{swbreak stop reason}
19791 @item @code{hwbreak-feature}
19792 @tab @code{hwbreak stop reason}
19798 @section Implementing a Remote Stub
19800 @cindex debugging stub, example
19801 @cindex remote stub, example
19802 @cindex stub example, remote debugging
19803 The stub files provided with @value{GDBN} implement the target side of the
19804 communication protocol, and the @value{GDBN} side is implemented in the
19805 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
19806 these subroutines to communicate, and ignore the details. (If you're
19807 implementing your own stub file, you can still ignore the details: start
19808 with one of the existing stub files. @file{sparc-stub.c} is the best
19809 organized, and therefore the easiest to read.)
19811 @cindex remote serial debugging, overview
19812 To debug a program running on another machine (the debugging
19813 @dfn{target} machine), you must first arrange for all the usual
19814 prerequisites for the program to run by itself. For example, for a C
19819 A startup routine to set up the C runtime environment; these usually
19820 have a name like @file{crt0}. The startup routine may be supplied by
19821 your hardware supplier, or you may have to write your own.
19824 A C subroutine library to support your program's
19825 subroutine calls, notably managing input and output.
19828 A way of getting your program to the other machine---for example, a
19829 download program. These are often supplied by the hardware
19830 manufacturer, but you may have to write your own from hardware
19834 The next step is to arrange for your program to use a serial port to
19835 communicate with the machine where @value{GDBN} is running (the @dfn{host}
19836 machine). In general terms, the scheme looks like this:
19840 @value{GDBN} already understands how to use this protocol; when everything
19841 else is set up, you can simply use the @samp{target remote} command
19842 (@pxref{Targets,,Specifying a Debugging Target}).
19844 @item On the target,
19845 you must link with your program a few special-purpose subroutines that
19846 implement the @value{GDBN} remote serial protocol. The file containing these
19847 subroutines is called a @dfn{debugging stub}.
19849 On certain remote targets, you can use an auxiliary program
19850 @code{gdbserver} instead of linking a stub into your program.
19851 @xref{Server,,Using the @code{gdbserver} Program}, for details.
19854 The debugging stub is specific to the architecture of the remote
19855 machine; for example, use @file{sparc-stub.c} to debug programs on
19858 @cindex remote serial stub list
19859 These working remote stubs are distributed with @value{GDBN}:
19864 @cindex @file{i386-stub.c}
19867 For Intel 386 and compatible architectures.
19870 @cindex @file{m68k-stub.c}
19871 @cindex Motorola 680x0
19873 For Motorola 680x0 architectures.
19876 @cindex @file{sh-stub.c}
19879 For Renesas SH architectures.
19882 @cindex @file{sparc-stub.c}
19884 For @sc{sparc} architectures.
19886 @item sparcl-stub.c
19887 @cindex @file{sparcl-stub.c}
19890 For Fujitsu @sc{sparclite} architectures.
19894 The @file{README} file in the @value{GDBN} distribution may list other
19895 recently added stubs.
19898 * Stub Contents:: What the stub can do for you
19899 * Bootstrapping:: What you must do for the stub
19900 * Debug Session:: Putting it all together
19903 @node Stub Contents
19904 @subsection What the Stub Can Do for You
19906 @cindex remote serial stub
19907 The debugging stub for your architecture supplies these three
19911 @item set_debug_traps
19912 @findex set_debug_traps
19913 @cindex remote serial stub, initialization
19914 This routine arranges for @code{handle_exception} to run when your
19915 program stops. You must call this subroutine explicitly in your
19916 program's startup code.
19918 @item handle_exception
19919 @findex handle_exception
19920 @cindex remote serial stub, main routine
19921 This is the central workhorse, but your program never calls it
19922 explicitly---the setup code arranges for @code{handle_exception} to
19923 run when a trap is triggered.
19925 @code{handle_exception} takes control when your program stops during
19926 execution (for example, on a breakpoint), and mediates communications
19927 with @value{GDBN} on the host machine. This is where the communications
19928 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
19929 representative on the target machine. It begins by sending summary
19930 information on the state of your program, then continues to execute,
19931 retrieving and transmitting any information @value{GDBN} needs, until you
19932 execute a @value{GDBN} command that makes your program resume; at that point,
19933 @code{handle_exception} returns control to your own code on the target
19937 @cindex @code{breakpoint} subroutine, remote
19938 Use this auxiliary subroutine to make your program contain a
19939 breakpoint. Depending on the particular situation, this may be the only
19940 way for @value{GDBN} to get control. For instance, if your target
19941 machine has some sort of interrupt button, you won't need to call this;
19942 pressing the interrupt button transfers control to
19943 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
19944 simply receiving characters on the serial port may also trigger a trap;
19945 again, in that situation, you don't need to call @code{breakpoint} from
19946 your own program---simply running @samp{target remote} from the host
19947 @value{GDBN} session gets control.
19949 Call @code{breakpoint} if none of these is true, or if you simply want
19950 to make certain your program stops at a predetermined point for the
19951 start of your debugging session.
19954 @node Bootstrapping
19955 @subsection What You Must Do for the Stub
19957 @cindex remote stub, support routines
19958 The debugging stubs that come with @value{GDBN} are set up for a particular
19959 chip architecture, but they have no information about the rest of your
19960 debugging target machine.
19962 First of all you need to tell the stub how to communicate with the
19966 @item int getDebugChar()
19967 @findex getDebugChar
19968 Write this subroutine to read a single character from the serial port.
19969 It may be identical to @code{getchar} for your target system; a
19970 different name is used to allow you to distinguish the two if you wish.
19972 @item void putDebugChar(int)
19973 @findex putDebugChar
19974 Write this subroutine to write a single character to the serial port.
19975 It may be identical to @code{putchar} for your target system; a
19976 different name is used to allow you to distinguish the two if you wish.
19979 @cindex control C, and remote debugging
19980 @cindex interrupting remote targets
19981 If you want @value{GDBN} to be able to stop your program while it is
19982 running, you need to use an interrupt-driven serial driver, and arrange
19983 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
19984 character). That is the character which @value{GDBN} uses to tell the
19985 remote system to stop.
19987 Getting the debugging target to return the proper status to @value{GDBN}
19988 probably requires changes to the standard stub; one quick and dirty way
19989 is to just execute a breakpoint instruction (the ``dirty'' part is that
19990 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
19992 Other routines you need to supply are:
19995 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
19996 @findex exceptionHandler
19997 Write this function to install @var{exception_address} in the exception
19998 handling tables. You need to do this because the stub does not have any
19999 way of knowing what the exception handling tables on your target system
20000 are like (for example, the processor's table might be in @sc{rom},
20001 containing entries which point to a table in @sc{ram}).
20002 The @var{exception_number} specifies the exception which should be changed;
20003 its meaning is architecture-dependent (for example, different numbers
20004 might represent divide by zero, misaligned access, etc). When this
20005 exception occurs, control should be transferred directly to
20006 @var{exception_address}, and the processor state (stack, registers,
20007 and so on) should be just as it is when a processor exception occurs. So if
20008 you want to use a jump instruction to reach @var{exception_address}, it
20009 should be a simple jump, not a jump to subroutine.
20011 For the 386, @var{exception_address} should be installed as an interrupt
20012 gate so that interrupts are masked while the handler runs. The gate
20013 should be at privilege level 0 (the most privileged level). The
20014 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
20015 help from @code{exceptionHandler}.
20017 @item void flush_i_cache()
20018 @findex flush_i_cache
20019 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
20020 instruction cache, if any, on your target machine. If there is no
20021 instruction cache, this subroutine may be a no-op.
20023 On target machines that have instruction caches, @value{GDBN} requires this
20024 function to make certain that the state of your program is stable.
20028 You must also make sure this library routine is available:
20031 @item void *memset(void *, int, int)
20033 This is the standard library function @code{memset} that sets an area of
20034 memory to a known value. If you have one of the free versions of
20035 @code{libc.a}, @code{memset} can be found there; otherwise, you must
20036 either obtain it from your hardware manufacturer, or write your own.
20039 If you do not use the GNU C compiler, you may need other standard
20040 library subroutines as well; this varies from one stub to another,
20041 but in general the stubs are likely to use any of the common library
20042 subroutines which @code{@value{NGCC}} generates as inline code.
20045 @node Debug Session
20046 @subsection Putting it All Together
20048 @cindex remote serial debugging summary
20049 In summary, when your program is ready to debug, you must follow these
20054 Make sure you have defined the supporting low-level routines
20055 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
20057 @code{getDebugChar}, @code{putDebugChar},
20058 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
20062 Insert these lines in your program's startup code, before the main
20063 procedure is called:
20070 On some machines, when a breakpoint trap is raised, the hardware
20071 automatically makes the PC point to the instruction after the
20072 breakpoint. If your machine doesn't do that, you may need to adjust
20073 @code{handle_exception} to arrange for it to return to the instruction
20074 after the breakpoint on this first invocation, so that your program
20075 doesn't keep hitting the initial breakpoint instead of making
20079 For the 680x0 stub only, you need to provide a variable called
20080 @code{exceptionHook}. Normally you just use:
20083 void (*exceptionHook)() = 0;
20087 but if before calling @code{set_debug_traps}, you set it to point to a
20088 function in your program, that function is called when
20089 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
20090 error). The function indicated by @code{exceptionHook} is called with
20091 one parameter: an @code{int} which is the exception number.
20094 Compile and link together: your program, the @value{GDBN} debugging stub for
20095 your target architecture, and the supporting subroutines.
20098 Make sure you have a serial connection between your target machine and
20099 the @value{GDBN} host, and identify the serial port on the host.
20102 @c The "remote" target now provides a `load' command, so we should
20103 @c document that. FIXME.
20104 Download your program to your target machine (or get it there by
20105 whatever means the manufacturer provides), and start it.
20108 Start @value{GDBN} on the host, and connect to the target
20109 (@pxref{Connecting,,Connecting to a Remote Target}).
20113 @node Configurations
20114 @chapter Configuration-Specific Information
20116 While nearly all @value{GDBN} commands are available for all native and
20117 cross versions of the debugger, there are some exceptions. This chapter
20118 describes things that are only available in certain configurations.
20120 There are three major categories of configurations: native
20121 configurations, where the host and target are the same, embedded
20122 operating system configurations, which are usually the same for several
20123 different processor architectures, and bare embedded processors, which
20124 are quite different from each other.
20129 * Embedded Processors::
20136 This section describes details specific to particular native
20141 * BSD libkvm Interface:: Debugging BSD kernel memory images
20142 * SVR4 Process Information:: SVR4 process information
20143 * DJGPP Native:: Features specific to the DJGPP port
20144 * Cygwin Native:: Features specific to the Cygwin port
20145 * Hurd Native:: Features specific to @sc{gnu} Hurd
20146 * Darwin:: Features specific to Darwin
20152 On HP-UX systems, if you refer to a function or variable name that
20153 begins with a dollar sign, @value{GDBN} searches for a user or system
20154 name first, before it searches for a convenience variable.
20157 @node BSD libkvm Interface
20158 @subsection BSD libkvm Interface
20161 @cindex kernel memory image
20162 @cindex kernel crash dump
20164 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
20165 interface that provides a uniform interface for accessing kernel virtual
20166 memory images, including live systems and crash dumps. @value{GDBN}
20167 uses this interface to allow you to debug live kernels and kernel crash
20168 dumps on many native BSD configurations. This is implemented as a
20169 special @code{kvm} debugging target. For debugging a live system, load
20170 the currently running kernel into @value{GDBN} and connect to the
20174 (@value{GDBP}) @b{target kvm}
20177 For debugging crash dumps, provide the file name of the crash dump as an
20181 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
20184 Once connected to the @code{kvm} target, the following commands are
20190 Set current context from the @dfn{Process Control Block} (PCB) address.
20193 Set current context from proc address. This command isn't available on
20194 modern FreeBSD systems.
20197 @node SVR4 Process Information
20198 @subsection SVR4 Process Information
20200 @cindex examine process image
20201 @cindex process info via @file{/proc}
20203 Many versions of SVR4 and compatible systems provide a facility called
20204 @samp{/proc} that can be used to examine the image of a running
20205 process using file-system subroutines.
20207 If @value{GDBN} is configured for an operating system with this
20208 facility, the command @code{info proc} is available to report
20209 information about the process running your program, or about any
20210 process running on your system. This includes, as of this writing,
20211 @sc{gnu}/Linux and Solaris, but not HP-UX, for example.
20213 This command may also work on core files that were created on a system
20214 that has the @samp{/proc} facility.
20220 @itemx info proc @var{process-id}
20221 Summarize available information about any running process. If a
20222 process ID is specified by @var{process-id}, display information about
20223 that process; otherwise display information about the program being
20224 debugged. The summary includes the debugged process ID, the command
20225 line used to invoke it, its current working directory, and its
20226 executable file's absolute file name.
20228 On some systems, @var{process-id} can be of the form
20229 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
20230 within a process. If the optional @var{pid} part is missing, it means
20231 a thread from the process being debugged (the leading @samp{/} still
20232 needs to be present, or else @value{GDBN} will interpret the number as
20233 a process ID rather than a thread ID).
20235 @item info proc cmdline
20236 @cindex info proc cmdline
20237 Show the original command line of the process. This command is
20238 specific to @sc{gnu}/Linux.
20240 @item info proc cwd
20241 @cindex info proc cwd
20242 Show the current working directory of the process. This command is
20243 specific to @sc{gnu}/Linux.
20245 @item info proc exe
20246 @cindex info proc exe
20247 Show the name of executable of the process. This command is specific
20250 @item info proc mappings
20251 @cindex memory address space mappings
20252 Report the memory address space ranges accessible in the program, with
20253 information on whether the process has read, write, or execute access
20254 rights to each range. On @sc{gnu}/Linux systems, each memory range
20255 includes the object file which is mapped to that range, instead of the
20256 memory access rights to that range.
20258 @item info proc stat
20259 @itemx info proc status
20260 @cindex process detailed status information
20261 These subcommands are specific to @sc{gnu}/Linux systems. They show
20262 the process-related information, including the user ID and group ID;
20263 how many threads are there in the process; its virtual memory usage;
20264 the signals that are pending, blocked, and ignored; its TTY; its
20265 consumption of system and user time; its stack size; its @samp{nice}
20266 value; etc. For more information, see the @samp{proc} man page
20267 (type @kbd{man 5 proc} from your shell prompt).
20269 @item info proc all
20270 Show all the information about the process described under all of the
20271 above @code{info proc} subcommands.
20274 @comment These sub-options of 'info proc' were not included when
20275 @comment procfs.c was re-written. Keep their descriptions around
20276 @comment against the day when someone finds the time to put them back in.
20277 @kindex info proc times
20278 @item info proc times
20279 Starting time, user CPU time, and system CPU time for your program and
20282 @kindex info proc id
20284 Report on the process IDs related to your program: its own process ID,
20285 the ID of its parent, the process group ID, and the session ID.
20288 @item set procfs-trace
20289 @kindex set procfs-trace
20290 @cindex @code{procfs} API calls
20291 This command enables and disables tracing of @code{procfs} API calls.
20293 @item show procfs-trace
20294 @kindex show procfs-trace
20295 Show the current state of @code{procfs} API call tracing.
20297 @item set procfs-file @var{file}
20298 @kindex set procfs-file
20299 Tell @value{GDBN} to write @code{procfs} API trace to the named
20300 @var{file}. @value{GDBN} appends the trace info to the previous
20301 contents of the file. The default is to display the trace on the
20304 @item show procfs-file
20305 @kindex show procfs-file
20306 Show the file to which @code{procfs} API trace is written.
20308 @item proc-trace-entry
20309 @itemx proc-trace-exit
20310 @itemx proc-untrace-entry
20311 @itemx proc-untrace-exit
20312 @kindex proc-trace-entry
20313 @kindex proc-trace-exit
20314 @kindex proc-untrace-entry
20315 @kindex proc-untrace-exit
20316 These commands enable and disable tracing of entries into and exits
20317 from the @code{syscall} interface.
20320 @kindex info pidlist
20321 @cindex process list, QNX Neutrino
20322 For QNX Neutrino only, this command displays the list of all the
20323 processes and all the threads within each process.
20326 @kindex info meminfo
20327 @cindex mapinfo list, QNX Neutrino
20328 For QNX Neutrino only, this command displays the list of all mapinfos.
20332 @subsection Features for Debugging @sc{djgpp} Programs
20333 @cindex @sc{djgpp} debugging
20334 @cindex native @sc{djgpp} debugging
20335 @cindex MS-DOS-specific commands
20338 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
20339 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
20340 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
20341 top of real-mode DOS systems and their emulations.
20343 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
20344 defines a few commands specific to the @sc{djgpp} port. This
20345 subsection describes those commands.
20350 This is a prefix of @sc{djgpp}-specific commands which print
20351 information about the target system and important OS structures.
20354 @cindex MS-DOS system info
20355 @cindex free memory information (MS-DOS)
20356 @item info dos sysinfo
20357 This command displays assorted information about the underlying
20358 platform: the CPU type and features, the OS version and flavor, the
20359 DPMI version, and the available conventional and DPMI memory.
20364 @cindex segment descriptor tables
20365 @cindex descriptor tables display
20367 @itemx info dos ldt
20368 @itemx info dos idt
20369 These 3 commands display entries from, respectively, Global, Local,
20370 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
20371 tables are data structures which store a descriptor for each segment
20372 that is currently in use. The segment's selector is an index into a
20373 descriptor table; the table entry for that index holds the
20374 descriptor's base address and limit, and its attributes and access
20377 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
20378 segment (used for both data and the stack), and a DOS segment (which
20379 allows access to DOS/BIOS data structures and absolute addresses in
20380 conventional memory). However, the DPMI host will usually define
20381 additional segments in order to support the DPMI environment.
20383 @cindex garbled pointers
20384 These commands allow to display entries from the descriptor tables.
20385 Without an argument, all entries from the specified table are
20386 displayed. An argument, which should be an integer expression, means
20387 display a single entry whose index is given by the argument. For
20388 example, here's a convenient way to display information about the
20389 debugged program's data segment:
20392 @exdent @code{(@value{GDBP}) info dos ldt $ds}
20393 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
20397 This comes in handy when you want to see whether a pointer is outside
20398 the data segment's limit (i.e.@: @dfn{garbled}).
20400 @cindex page tables display (MS-DOS)
20402 @itemx info dos pte
20403 These two commands display entries from, respectively, the Page
20404 Directory and the Page Tables. Page Directories and Page Tables are
20405 data structures which control how virtual memory addresses are mapped
20406 into physical addresses. A Page Table includes an entry for every
20407 page of memory that is mapped into the program's address space; there
20408 may be several Page Tables, each one holding up to 4096 entries. A
20409 Page Directory has up to 4096 entries, one each for every Page Table
20410 that is currently in use.
20412 Without an argument, @kbd{info dos pde} displays the entire Page
20413 Directory, and @kbd{info dos pte} displays all the entries in all of
20414 the Page Tables. An argument, an integer expression, given to the
20415 @kbd{info dos pde} command means display only that entry from the Page
20416 Directory table. An argument given to the @kbd{info dos pte} command
20417 means display entries from a single Page Table, the one pointed to by
20418 the specified entry in the Page Directory.
20420 @cindex direct memory access (DMA) on MS-DOS
20421 These commands are useful when your program uses @dfn{DMA} (Direct
20422 Memory Access), which needs physical addresses to program the DMA
20425 These commands are supported only with some DPMI servers.
20427 @cindex physical address from linear address
20428 @item info dos address-pte @var{addr}
20429 This command displays the Page Table entry for a specified linear
20430 address. The argument @var{addr} is a linear address which should
20431 already have the appropriate segment's base address added to it,
20432 because this command accepts addresses which may belong to @emph{any}
20433 segment. For example, here's how to display the Page Table entry for
20434 the page where a variable @code{i} is stored:
20437 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
20438 @exdent @code{Page Table entry for address 0x11a00d30:}
20439 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
20443 This says that @code{i} is stored at offset @code{0xd30} from the page
20444 whose physical base address is @code{0x02698000}, and shows all the
20445 attributes of that page.
20447 Note that you must cast the addresses of variables to a @code{char *},
20448 since otherwise the value of @code{__djgpp_base_address}, the base
20449 address of all variables and functions in a @sc{djgpp} program, will
20450 be added using the rules of C pointer arithmetics: if @code{i} is
20451 declared an @code{int}, @value{GDBN} will add 4 times the value of
20452 @code{__djgpp_base_address} to the address of @code{i}.
20454 Here's another example, it displays the Page Table entry for the
20458 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
20459 @exdent @code{Page Table entry for address 0x29110:}
20460 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
20464 (The @code{+ 3} offset is because the transfer buffer's address is the
20465 3rd member of the @code{_go32_info_block} structure.) The output
20466 clearly shows that this DPMI server maps the addresses in conventional
20467 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
20468 linear (@code{0x29110}) addresses are identical.
20470 This command is supported only with some DPMI servers.
20473 @cindex DOS serial data link, remote debugging
20474 In addition to native debugging, the DJGPP port supports remote
20475 debugging via a serial data link. The following commands are specific
20476 to remote serial debugging in the DJGPP port of @value{GDBN}.
20479 @kindex set com1base
20480 @kindex set com1irq
20481 @kindex set com2base
20482 @kindex set com2irq
20483 @kindex set com3base
20484 @kindex set com3irq
20485 @kindex set com4base
20486 @kindex set com4irq
20487 @item set com1base @var{addr}
20488 This command sets the base I/O port address of the @file{COM1} serial
20491 @item set com1irq @var{irq}
20492 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
20493 for the @file{COM1} serial port.
20495 There are similar commands @samp{set com2base}, @samp{set com3irq},
20496 etc.@: for setting the port address and the @code{IRQ} lines for the
20499 @kindex show com1base
20500 @kindex show com1irq
20501 @kindex show com2base
20502 @kindex show com2irq
20503 @kindex show com3base
20504 @kindex show com3irq
20505 @kindex show com4base
20506 @kindex show com4irq
20507 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
20508 display the current settings of the base address and the @code{IRQ}
20509 lines used by the COM ports.
20512 @kindex info serial
20513 @cindex DOS serial port status
20514 This command prints the status of the 4 DOS serial ports. For each
20515 port, it prints whether it's active or not, its I/O base address and
20516 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
20517 counts of various errors encountered so far.
20521 @node Cygwin Native
20522 @subsection Features for Debugging MS Windows PE Executables
20523 @cindex MS Windows debugging
20524 @cindex native Cygwin debugging
20525 @cindex Cygwin-specific commands
20527 @value{GDBN} supports native debugging of MS Windows programs, including
20528 DLLs with and without symbolic debugging information.
20530 @cindex Ctrl-BREAK, MS-Windows
20531 @cindex interrupt debuggee on MS-Windows
20532 MS-Windows programs that call @code{SetConsoleMode} to switch off the
20533 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
20534 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
20535 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
20536 sequence, which can be used to interrupt the debuggee even if it
20539 There are various additional Cygwin-specific commands, described in
20540 this section. Working with DLLs that have no debugging symbols is
20541 described in @ref{Non-debug DLL Symbols}.
20546 This is a prefix of MS Windows-specific commands which print
20547 information about the target system and important OS structures.
20549 @item info w32 selector
20550 This command displays information returned by
20551 the Win32 API @code{GetThreadSelectorEntry} function.
20552 It takes an optional argument that is evaluated to
20553 a long value to give the information about this given selector.
20554 Without argument, this command displays information
20555 about the six segment registers.
20557 @item info w32 thread-information-block
20558 This command displays thread specific information stored in the
20559 Thread Information Block (readable on the X86 CPU family using @code{$fs}
20560 selector for 32-bit programs and @code{$gs} for 64-bit programs).
20564 This is a Cygwin-specific alias of @code{info shared}.
20566 @kindex set cygwin-exceptions
20567 @cindex debugging the Cygwin DLL
20568 @cindex Cygwin DLL, debugging
20569 @item set cygwin-exceptions @var{mode}
20570 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
20571 happen inside the Cygwin DLL. If @var{mode} is @code{off},
20572 @value{GDBN} will delay recognition of exceptions, and may ignore some
20573 exceptions which seem to be caused by internal Cygwin DLL
20574 ``bookkeeping''. This option is meant primarily for debugging the
20575 Cygwin DLL itself; the default value is @code{off} to avoid annoying
20576 @value{GDBN} users with false @code{SIGSEGV} signals.
20578 @kindex show cygwin-exceptions
20579 @item show cygwin-exceptions
20580 Displays whether @value{GDBN} will break on exceptions that happen
20581 inside the Cygwin DLL itself.
20583 @kindex set new-console
20584 @item set new-console @var{mode}
20585 If @var{mode} is @code{on} the debuggee will
20586 be started in a new console on next start.
20587 If @var{mode} is @code{off}, the debuggee will
20588 be started in the same console as the debugger.
20590 @kindex show new-console
20591 @item show new-console
20592 Displays whether a new console is used
20593 when the debuggee is started.
20595 @kindex set new-group
20596 @item set new-group @var{mode}
20597 This boolean value controls whether the debuggee should
20598 start a new group or stay in the same group as the debugger.
20599 This affects the way the Windows OS handles
20602 @kindex show new-group
20603 @item show new-group
20604 Displays current value of new-group boolean.
20606 @kindex set debugevents
20607 @item set debugevents
20608 This boolean value adds debug output concerning kernel events related
20609 to the debuggee seen by the debugger. This includes events that
20610 signal thread and process creation and exit, DLL loading and
20611 unloading, console interrupts, and debugging messages produced by the
20612 Windows @code{OutputDebugString} API call.
20614 @kindex set debugexec
20615 @item set debugexec
20616 This boolean value adds debug output concerning execute events
20617 (such as resume thread) seen by the debugger.
20619 @kindex set debugexceptions
20620 @item set debugexceptions
20621 This boolean value adds debug output concerning exceptions in the
20622 debuggee seen by the debugger.
20624 @kindex set debugmemory
20625 @item set debugmemory
20626 This boolean value adds debug output concerning debuggee memory reads
20627 and writes by the debugger.
20631 This boolean values specifies whether the debuggee is called
20632 via a shell or directly (default value is on).
20636 Displays if the debuggee will be started with a shell.
20641 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
20644 @node Non-debug DLL Symbols
20645 @subsubsection Support for DLLs without Debugging Symbols
20646 @cindex DLLs with no debugging symbols
20647 @cindex Minimal symbols and DLLs
20649 Very often on windows, some of the DLLs that your program relies on do
20650 not include symbolic debugging information (for example,
20651 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
20652 symbols in a DLL, it relies on the minimal amount of symbolic
20653 information contained in the DLL's export table. This section
20654 describes working with such symbols, known internally to @value{GDBN} as
20655 ``minimal symbols''.
20657 Note that before the debugged program has started execution, no DLLs
20658 will have been loaded. The easiest way around this problem is simply to
20659 start the program --- either by setting a breakpoint or letting the
20660 program run once to completion.
20662 @subsubsection DLL Name Prefixes
20664 In keeping with the naming conventions used by the Microsoft debugging
20665 tools, DLL export symbols are made available with a prefix based on the
20666 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
20667 also entered into the symbol table, so @code{CreateFileA} is often
20668 sufficient. In some cases there will be name clashes within a program
20669 (particularly if the executable itself includes full debugging symbols)
20670 necessitating the use of the fully qualified name when referring to the
20671 contents of the DLL. Use single-quotes around the name to avoid the
20672 exclamation mark (``!'') being interpreted as a language operator.
20674 Note that the internal name of the DLL may be all upper-case, even
20675 though the file name of the DLL is lower-case, or vice-versa. Since
20676 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
20677 some confusion. If in doubt, try the @code{info functions} and
20678 @code{info variables} commands or even @code{maint print msymbols}
20679 (@pxref{Symbols}). Here's an example:
20682 (@value{GDBP}) info function CreateFileA
20683 All functions matching regular expression "CreateFileA":
20685 Non-debugging symbols:
20686 0x77e885f4 CreateFileA
20687 0x77e885f4 KERNEL32!CreateFileA
20691 (@value{GDBP}) info function !
20692 All functions matching regular expression "!":
20694 Non-debugging symbols:
20695 0x6100114c cygwin1!__assert
20696 0x61004034 cygwin1!_dll_crt0@@0
20697 0x61004240 cygwin1!dll_crt0(per_process *)
20701 @subsubsection Working with Minimal Symbols
20703 Symbols extracted from a DLL's export table do not contain very much
20704 type information. All that @value{GDBN} can do is guess whether a symbol
20705 refers to a function or variable depending on the linker section that
20706 contains the symbol. Also note that the actual contents of the memory
20707 contained in a DLL are not available unless the program is running. This
20708 means that you cannot examine the contents of a variable or disassemble
20709 a function within a DLL without a running program.
20711 Variables are generally treated as pointers and dereferenced
20712 automatically. For this reason, it is often necessary to prefix a
20713 variable name with the address-of operator (``&'') and provide explicit
20714 type information in the command. Here's an example of the type of
20718 (@value{GDBP}) print 'cygwin1!__argv'
20723 (@value{GDBP}) x 'cygwin1!__argv'
20724 0x10021610: "\230y\""
20727 And two possible solutions:
20730 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
20731 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
20735 (@value{GDBP}) x/2x &'cygwin1!__argv'
20736 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
20737 (@value{GDBP}) x/x 0x10021608
20738 0x10021608: 0x0022fd98
20739 (@value{GDBP}) x/s 0x0022fd98
20740 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
20743 Setting a break point within a DLL is possible even before the program
20744 starts execution. However, under these circumstances, @value{GDBN} can't
20745 examine the initial instructions of the function in order to skip the
20746 function's frame set-up code. You can work around this by using ``*&''
20747 to set the breakpoint at a raw memory address:
20750 (@value{GDBP}) break *&'python22!PyOS_Readline'
20751 Breakpoint 1 at 0x1e04eff0
20754 The author of these extensions is not entirely convinced that setting a
20755 break point within a shared DLL like @file{kernel32.dll} is completely
20759 @subsection Commands Specific to @sc{gnu} Hurd Systems
20760 @cindex @sc{gnu} Hurd debugging
20762 This subsection describes @value{GDBN} commands specific to the
20763 @sc{gnu} Hurd native debugging.
20768 @kindex set signals@r{, Hurd command}
20769 @kindex set sigs@r{, Hurd command}
20770 This command toggles the state of inferior signal interception by
20771 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
20772 affected by this command. @code{sigs} is a shorthand alias for
20777 @kindex show signals@r{, Hurd command}
20778 @kindex show sigs@r{, Hurd command}
20779 Show the current state of intercepting inferior's signals.
20781 @item set signal-thread
20782 @itemx set sigthread
20783 @kindex set signal-thread
20784 @kindex set sigthread
20785 This command tells @value{GDBN} which thread is the @code{libc} signal
20786 thread. That thread is run when a signal is delivered to a running
20787 process. @code{set sigthread} is the shorthand alias of @code{set
20790 @item show signal-thread
20791 @itemx show sigthread
20792 @kindex show signal-thread
20793 @kindex show sigthread
20794 These two commands show which thread will run when the inferior is
20795 delivered a signal.
20798 @kindex set stopped@r{, Hurd command}
20799 This commands tells @value{GDBN} that the inferior process is stopped,
20800 as with the @code{SIGSTOP} signal. The stopped process can be
20801 continued by delivering a signal to it.
20804 @kindex show stopped@r{, Hurd command}
20805 This command shows whether @value{GDBN} thinks the debuggee is
20808 @item set exceptions
20809 @kindex set exceptions@r{, Hurd command}
20810 Use this command to turn off trapping of exceptions in the inferior.
20811 When exception trapping is off, neither breakpoints nor
20812 single-stepping will work. To restore the default, set exception
20815 @item show exceptions
20816 @kindex show exceptions@r{, Hurd command}
20817 Show the current state of trapping exceptions in the inferior.
20819 @item set task pause
20820 @kindex set task@r{, Hurd commands}
20821 @cindex task attributes (@sc{gnu} Hurd)
20822 @cindex pause current task (@sc{gnu} Hurd)
20823 This command toggles task suspension when @value{GDBN} has control.
20824 Setting it to on takes effect immediately, and the task is suspended
20825 whenever @value{GDBN} gets control. Setting it to off will take
20826 effect the next time the inferior is continued. If this option is set
20827 to off, you can use @code{set thread default pause on} or @code{set
20828 thread pause on} (see below) to pause individual threads.
20830 @item show task pause
20831 @kindex show task@r{, Hurd commands}
20832 Show the current state of task suspension.
20834 @item set task detach-suspend-count
20835 @cindex task suspend count
20836 @cindex detach from task, @sc{gnu} Hurd
20837 This command sets the suspend count the task will be left with when
20838 @value{GDBN} detaches from it.
20840 @item show task detach-suspend-count
20841 Show the suspend count the task will be left with when detaching.
20843 @item set task exception-port
20844 @itemx set task excp
20845 @cindex task exception port, @sc{gnu} Hurd
20846 This command sets the task exception port to which @value{GDBN} will
20847 forward exceptions. The argument should be the value of the @dfn{send
20848 rights} of the task. @code{set task excp} is a shorthand alias.
20850 @item set noninvasive
20851 @cindex noninvasive task options
20852 This command switches @value{GDBN} to a mode that is the least
20853 invasive as far as interfering with the inferior is concerned. This
20854 is the same as using @code{set task pause}, @code{set exceptions}, and
20855 @code{set signals} to values opposite to the defaults.
20857 @item info send-rights
20858 @itemx info receive-rights
20859 @itemx info port-rights
20860 @itemx info port-sets
20861 @itemx info dead-names
20864 @cindex send rights, @sc{gnu} Hurd
20865 @cindex receive rights, @sc{gnu} Hurd
20866 @cindex port rights, @sc{gnu} Hurd
20867 @cindex port sets, @sc{gnu} Hurd
20868 @cindex dead names, @sc{gnu} Hurd
20869 These commands display information about, respectively, send rights,
20870 receive rights, port rights, port sets, and dead names of a task.
20871 There are also shorthand aliases: @code{info ports} for @code{info
20872 port-rights} and @code{info psets} for @code{info port-sets}.
20874 @item set thread pause
20875 @kindex set thread@r{, Hurd command}
20876 @cindex thread properties, @sc{gnu} Hurd
20877 @cindex pause current thread (@sc{gnu} Hurd)
20878 This command toggles current thread suspension when @value{GDBN} has
20879 control. Setting it to on takes effect immediately, and the current
20880 thread is suspended whenever @value{GDBN} gets control. Setting it to
20881 off will take effect the next time the inferior is continued.
20882 Normally, this command has no effect, since when @value{GDBN} has
20883 control, the whole task is suspended. However, if you used @code{set
20884 task pause off} (see above), this command comes in handy to suspend
20885 only the current thread.
20887 @item show thread pause
20888 @kindex show thread@r{, Hurd command}
20889 This command shows the state of current thread suspension.
20891 @item set thread run
20892 This command sets whether the current thread is allowed to run.
20894 @item show thread run
20895 Show whether the current thread is allowed to run.
20897 @item set thread detach-suspend-count
20898 @cindex thread suspend count, @sc{gnu} Hurd
20899 @cindex detach from thread, @sc{gnu} Hurd
20900 This command sets the suspend count @value{GDBN} will leave on a
20901 thread when detaching. This number is relative to the suspend count
20902 found by @value{GDBN} when it notices the thread; use @code{set thread
20903 takeover-suspend-count} to force it to an absolute value.
20905 @item show thread detach-suspend-count
20906 Show the suspend count @value{GDBN} will leave on the thread when
20909 @item set thread exception-port
20910 @itemx set thread excp
20911 Set the thread exception port to which to forward exceptions. This
20912 overrides the port set by @code{set task exception-port} (see above).
20913 @code{set thread excp} is the shorthand alias.
20915 @item set thread takeover-suspend-count
20916 Normally, @value{GDBN}'s thread suspend counts are relative to the
20917 value @value{GDBN} finds when it notices each thread. This command
20918 changes the suspend counts to be absolute instead.
20920 @item set thread default
20921 @itemx show thread default
20922 @cindex thread default settings, @sc{gnu} Hurd
20923 Each of the above @code{set thread} commands has a @code{set thread
20924 default} counterpart (e.g., @code{set thread default pause}, @code{set
20925 thread default exception-port}, etc.). The @code{thread default}
20926 variety of commands sets the default thread properties for all
20927 threads; you can then change the properties of individual threads with
20928 the non-default commands.
20935 @value{GDBN} provides the following commands specific to the Darwin target:
20938 @item set debug darwin @var{num}
20939 @kindex set debug darwin
20940 When set to a non zero value, enables debugging messages specific to
20941 the Darwin support. Higher values produce more verbose output.
20943 @item show debug darwin
20944 @kindex show debug darwin
20945 Show the current state of Darwin messages.
20947 @item set debug mach-o @var{num}
20948 @kindex set debug mach-o
20949 When set to a non zero value, enables debugging messages while
20950 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
20951 file format used on Darwin for object and executable files.) Higher
20952 values produce more verbose output. This is a command to diagnose
20953 problems internal to @value{GDBN} and should not be needed in normal
20956 @item show debug mach-o
20957 @kindex show debug mach-o
20958 Show the current state of Mach-O file messages.
20960 @item set mach-exceptions on
20961 @itemx set mach-exceptions off
20962 @kindex set mach-exceptions
20963 On Darwin, faults are first reported as a Mach exception and are then
20964 mapped to a Posix signal. Use this command to turn on trapping of
20965 Mach exceptions in the inferior. This might be sometimes useful to
20966 better understand the cause of a fault. The default is off.
20968 @item show mach-exceptions
20969 @kindex show mach-exceptions
20970 Show the current state of exceptions trapping.
20975 @section Embedded Operating Systems
20977 This section describes configurations involving the debugging of
20978 embedded operating systems that are available for several different
20981 @value{GDBN} includes the ability to debug programs running on
20982 various real-time operating systems.
20984 @node Embedded Processors
20985 @section Embedded Processors
20987 This section goes into details specific to particular embedded
20990 @cindex send command to simulator
20991 Whenever a specific embedded processor has a simulator, @value{GDBN}
20992 allows to send an arbitrary command to the simulator.
20995 @item sim @var{command}
20996 @kindex sim@r{, a command}
20997 Send an arbitrary @var{command} string to the simulator. Consult the
20998 documentation for the specific simulator in use for information about
20999 acceptable commands.
21005 * M32R/D:: Renesas M32R/D
21006 * M68K:: Motorola M68K
21007 * MicroBlaze:: Xilinx MicroBlaze
21008 * MIPS Embedded:: MIPS Embedded
21009 * PowerPC Embedded:: PowerPC Embedded
21010 * PA:: HP PA Embedded
21011 * Sparclet:: Tsqware Sparclet
21012 * Sparclite:: Fujitsu Sparclite
21013 * Z8000:: Zilog Z8000
21016 * Super-H:: Renesas Super-H
21025 @item target rdi @var{dev}
21026 ARM Angel monitor, via RDI library interface to ADP protocol. You may
21027 use this target to communicate with both boards running the Angel
21028 monitor, or with the EmbeddedICE JTAG debug device.
21031 @item target rdp @var{dev}
21036 @value{GDBN} provides the following ARM-specific commands:
21039 @item set arm disassembler
21041 This commands selects from a list of disassembly styles. The
21042 @code{"std"} style is the standard style.
21044 @item show arm disassembler
21046 Show the current disassembly style.
21048 @item set arm apcs32
21049 @cindex ARM 32-bit mode
21050 This command toggles ARM operation mode between 32-bit and 26-bit.
21052 @item show arm apcs32
21053 Display the current usage of the ARM 32-bit mode.
21055 @item set arm fpu @var{fputype}
21056 This command sets the ARM floating-point unit (FPU) type. The
21057 argument @var{fputype} can be one of these:
21061 Determine the FPU type by querying the OS ABI.
21063 Software FPU, with mixed-endian doubles on little-endian ARM
21066 GCC-compiled FPA co-processor.
21068 Software FPU with pure-endian doubles.
21074 Show the current type of the FPU.
21077 This command forces @value{GDBN} to use the specified ABI.
21080 Show the currently used ABI.
21082 @item set arm fallback-mode (arm|thumb|auto)
21083 @value{GDBN} uses the symbol table, when available, to determine
21084 whether instructions are ARM or Thumb. This command controls
21085 @value{GDBN}'s default behavior when the symbol table is not
21086 available. The default is @samp{auto}, which causes @value{GDBN} to
21087 use the current execution mode (from the @code{T} bit in the @code{CPSR}
21090 @item show arm fallback-mode
21091 Show the current fallback instruction mode.
21093 @item set arm force-mode (arm|thumb|auto)
21094 This command overrides use of the symbol table to determine whether
21095 instructions are ARM or Thumb. The default is @samp{auto}, which
21096 causes @value{GDBN} to use the symbol table and then the setting
21097 of @samp{set arm fallback-mode}.
21099 @item show arm force-mode
21100 Show the current forced instruction mode.
21102 @item set debug arm
21103 Toggle whether to display ARM-specific debugging messages from the ARM
21104 target support subsystem.
21106 @item show debug arm
21107 Show whether ARM-specific debugging messages are enabled.
21110 The following commands are available when an ARM target is debugged
21111 using the RDI interface:
21114 @item rdilogfile @r{[}@var{file}@r{]}
21116 @cindex ADP (Angel Debugger Protocol) logging
21117 Set the filename for the ADP (Angel Debugger Protocol) packet log.
21118 With an argument, sets the log file to the specified @var{file}. With
21119 no argument, show the current log file name. The default log file is
21122 @item rdilogenable @r{[}@var{arg}@r{]}
21123 @kindex rdilogenable
21124 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
21125 enables logging, with an argument 0 or @code{"no"} disables it. With
21126 no arguments displays the current setting. When logging is enabled,
21127 ADP packets exchanged between @value{GDBN} and the RDI target device
21128 are logged to a file.
21130 @item set rdiromatzero
21131 @kindex set rdiromatzero
21132 @cindex ROM at zero address, RDI
21133 Tell @value{GDBN} whether the target has ROM at address 0. If on,
21134 vector catching is disabled, so that zero address can be used. If off
21135 (the default), vector catching is enabled. For this command to take
21136 effect, it needs to be invoked prior to the @code{target rdi} command.
21138 @item show rdiromatzero
21139 @kindex show rdiromatzero
21140 Show the current setting of ROM at zero address.
21142 @item set rdiheartbeat
21143 @kindex set rdiheartbeat
21144 @cindex RDI heartbeat
21145 Enable or disable RDI heartbeat packets. It is not recommended to
21146 turn on this option, since it confuses ARM and EPI JTAG interface, as
21147 well as the Angel monitor.
21149 @item show rdiheartbeat
21150 @kindex show rdiheartbeat
21151 Show the setting of RDI heartbeat packets.
21155 @item target sim @r{[}@var{simargs}@r{]} @dots{}
21156 The @value{GDBN} ARM simulator accepts the following optional arguments.
21159 @item --swi-support=@var{type}
21160 Tell the simulator which SWI interfaces to support. The argument
21161 @var{type} may be a comma separated list of the following values.
21162 The default value is @code{all}.
21175 @subsection Renesas M32R/D and M32R/SDI
21178 @kindex target m32r
21179 @item target m32r @var{dev}
21180 Renesas M32R/D ROM monitor.
21182 @kindex target m32rsdi
21183 @item target m32rsdi @var{dev}
21184 Renesas M32R SDI server, connected via parallel port to the board.
21187 The following @value{GDBN} commands are specific to the M32R monitor:
21190 @item set download-path @var{path}
21191 @kindex set download-path
21192 @cindex find downloadable @sc{srec} files (M32R)
21193 Set the default path for finding downloadable @sc{srec} files.
21195 @item show download-path
21196 @kindex show download-path
21197 Show the default path for downloadable @sc{srec} files.
21199 @item set board-address @var{addr}
21200 @kindex set board-address
21201 @cindex M32-EVA target board address
21202 Set the IP address for the M32R-EVA target board.
21204 @item show board-address
21205 @kindex show board-address
21206 Show the current IP address of the target board.
21208 @item set server-address @var{addr}
21209 @kindex set server-address
21210 @cindex download server address (M32R)
21211 Set the IP address for the download server, which is the @value{GDBN}'s
21214 @item show server-address
21215 @kindex show server-address
21216 Display the IP address of the download server.
21218 @item upload @r{[}@var{file}@r{]}
21219 @kindex upload@r{, M32R}
21220 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
21221 upload capability. If no @var{file} argument is given, the current
21222 executable file is uploaded.
21224 @item tload @r{[}@var{file}@r{]}
21225 @kindex tload@r{, M32R}
21226 Test the @code{upload} command.
21229 The following commands are available for M32R/SDI:
21234 @cindex reset SDI connection, M32R
21235 This command resets the SDI connection.
21239 This command shows the SDI connection status.
21242 @kindex debug_chaos
21243 @cindex M32R/Chaos debugging
21244 Instructs the remote that M32R/Chaos debugging is to be used.
21246 @item use_debug_dma
21247 @kindex use_debug_dma
21248 Instructs the remote to use the DEBUG_DMA method of accessing memory.
21251 @kindex use_mon_code
21252 Instructs the remote to use the MON_CODE method of accessing memory.
21255 @kindex use_ib_break
21256 Instructs the remote to set breakpoints by IB break.
21258 @item use_dbt_break
21259 @kindex use_dbt_break
21260 Instructs the remote to set breakpoints by DBT.
21266 The Motorola m68k configuration includes ColdFire support, and a
21267 target command for the following ROM monitor.
21271 @kindex target dbug
21272 @item target dbug @var{dev}
21273 dBUG ROM monitor for Motorola ColdFire.
21278 @subsection MicroBlaze
21279 @cindex Xilinx MicroBlaze
21280 @cindex XMD, Xilinx Microprocessor Debugger
21282 The MicroBlaze is a soft-core processor supported on various Xilinx
21283 FPGAs, such as Spartan or Virtex series. Boards with these processors
21284 usually have JTAG ports which connect to a host system running the Xilinx
21285 Embedded Development Kit (EDK) or Software Development Kit (SDK).
21286 This host system is used to download the configuration bitstream to
21287 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
21288 communicates with the target board using the JTAG interface and
21289 presents a @code{gdbserver} interface to the board. By default
21290 @code{xmd} uses port @code{1234}. (While it is possible to change
21291 this default port, it requires the use of undocumented @code{xmd}
21292 commands. Contact Xilinx support if you need to do this.)
21294 Use these GDB commands to connect to the MicroBlaze target processor.
21297 @item target remote :1234
21298 Use this command to connect to the target if you are running @value{GDBN}
21299 on the same system as @code{xmd}.
21301 @item target remote @var{xmd-host}:1234
21302 Use this command to connect to the target if it is connected to @code{xmd}
21303 running on a different system named @var{xmd-host}.
21306 Use this command to download a program to the MicroBlaze target.
21308 @item set debug microblaze @var{n}
21309 Enable MicroBlaze-specific debugging messages if non-zero.
21311 @item show debug microblaze @var{n}
21312 Show MicroBlaze-specific debugging level.
21315 @node MIPS Embedded
21316 @subsection @acronym{MIPS} Embedded
21318 @cindex @acronym{MIPS} boards
21319 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
21320 @acronym{MIPS} board attached to a serial line. This is available when
21321 you configure @value{GDBN} with @samp{--target=mips-elf}.
21324 Use these @value{GDBN} commands to specify the connection to your target board:
21327 @item target mips @var{port}
21328 @kindex target mips @var{port}
21329 To run a program on the board, start up @code{@value{GDBP}} with the
21330 name of your program as the argument. To connect to the board, use the
21331 command @samp{target mips @var{port}}, where @var{port} is the name of
21332 the serial port connected to the board. If the program has not already
21333 been downloaded to the board, you may use the @code{load} command to
21334 download it. You can then use all the usual @value{GDBN} commands.
21336 For example, this sequence connects to the target board through a serial
21337 port, and loads and runs a program called @var{prog} through the
21341 host$ @value{GDBP} @var{prog}
21342 @value{GDBN} is free software and @dots{}
21343 (@value{GDBP}) target mips /dev/ttyb
21344 (@value{GDBP}) load @var{prog}
21348 @item target mips @var{hostname}:@var{portnumber}
21349 On some @value{GDBN} host configurations, you can specify a TCP
21350 connection (for instance, to a serial line managed by a terminal
21351 concentrator) instead of a serial port, using the syntax
21352 @samp{@var{hostname}:@var{portnumber}}.
21354 @item target pmon @var{port}
21355 @kindex target pmon @var{port}
21358 @item target ddb @var{port}
21359 @kindex target ddb @var{port}
21360 NEC's DDB variant of PMON for Vr4300.
21362 @item target lsi @var{port}
21363 @kindex target lsi @var{port}
21364 LSI variant of PMON.
21366 @kindex target r3900
21367 @item target r3900 @var{dev}
21368 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
21370 @kindex target array
21371 @item target array @var{dev}
21372 Array Tech LSI33K RAID controller board.
21378 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
21381 @item set mipsfpu double
21382 @itemx set mipsfpu single
21383 @itemx set mipsfpu none
21384 @itemx set mipsfpu auto
21385 @itemx show mipsfpu
21386 @kindex set mipsfpu
21387 @kindex show mipsfpu
21388 @cindex @acronym{MIPS} remote floating point
21389 @cindex floating point, @acronym{MIPS} remote
21390 If your target board does not support the @acronym{MIPS} floating point
21391 coprocessor, you should use the command @samp{set mipsfpu none} (if you
21392 need this, you may wish to put the command in your @value{GDBN} init
21393 file). This tells @value{GDBN} how to find the return value of
21394 functions which return floating point values. It also allows
21395 @value{GDBN} to avoid saving the floating point registers when calling
21396 functions on the board. If you are using a floating point coprocessor
21397 with only single precision floating point support, as on the @sc{r4650}
21398 processor, use the command @samp{set mipsfpu single}. The default
21399 double precision floating point coprocessor may be selected using
21400 @samp{set mipsfpu double}.
21402 In previous versions the only choices were double precision or no
21403 floating point, so @samp{set mipsfpu on} will select double precision
21404 and @samp{set mipsfpu off} will select no floating point.
21406 As usual, you can inquire about the @code{mipsfpu} variable with
21407 @samp{show mipsfpu}.
21409 @item set timeout @var{seconds}
21410 @itemx set retransmit-timeout @var{seconds}
21411 @itemx show timeout
21412 @itemx show retransmit-timeout
21413 @cindex @code{timeout}, @acronym{MIPS} protocol
21414 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
21415 @kindex set timeout
21416 @kindex show timeout
21417 @kindex set retransmit-timeout
21418 @kindex show retransmit-timeout
21419 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
21420 remote protocol, with the @code{set timeout @var{seconds}} command. The
21421 default is 5 seconds. Similarly, you can control the timeout used while
21422 waiting for an acknowledgment of a packet with the @code{set
21423 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
21424 You can inspect both values with @code{show timeout} and @code{show
21425 retransmit-timeout}. (These commands are @emph{only} available when
21426 @value{GDBN} is configured for @samp{--target=mips-elf}.)
21428 The timeout set by @code{set timeout} does not apply when @value{GDBN}
21429 is waiting for your program to stop. In that case, @value{GDBN} waits
21430 forever because it has no way of knowing how long the program is going
21431 to run before stopping.
21433 @item set syn-garbage-limit @var{num}
21434 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
21435 @cindex synchronize with remote @acronym{MIPS} target
21436 Limit the maximum number of characters @value{GDBN} should ignore when
21437 it tries to synchronize with the remote target. The default is 10
21438 characters. Setting the limit to -1 means there's no limit.
21440 @item show syn-garbage-limit
21441 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
21442 Show the current limit on the number of characters to ignore when
21443 trying to synchronize with the remote system.
21445 @item set monitor-prompt @var{prompt}
21446 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
21447 @cindex remote monitor prompt
21448 Tell @value{GDBN} to expect the specified @var{prompt} string from the
21449 remote monitor. The default depends on the target:
21459 @item show monitor-prompt
21460 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
21461 Show the current strings @value{GDBN} expects as the prompt from the
21464 @item set monitor-warnings
21465 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
21466 Enable or disable monitor warnings about hardware breakpoints. This
21467 has effect only for the @code{lsi} target. When on, @value{GDBN} will
21468 display warning messages whose codes are returned by the @code{lsi}
21469 PMON monitor for breakpoint commands.
21471 @item show monitor-warnings
21472 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
21473 Show the current setting of printing monitor warnings.
21475 @item pmon @var{command}
21476 @kindex pmon@r{, @acronym{MIPS} remote}
21477 @cindex send PMON command
21478 This command allows sending an arbitrary @var{command} string to the
21479 monitor. The monitor must be in debug mode for this to work.
21482 @node PowerPC Embedded
21483 @subsection PowerPC Embedded
21485 @cindex DVC register
21486 @value{GDBN} supports using the DVC (Data Value Compare) register to
21487 implement in hardware simple hardware watchpoint conditions of the form:
21490 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
21491 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
21494 The DVC register will be automatically used when @value{GDBN} detects
21495 such pattern in a condition expression, and the created watchpoint uses one
21496 debug register (either the @code{exact-watchpoints} option is on and the
21497 variable is scalar, or the variable has a length of one byte). This feature
21498 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
21501 When running on PowerPC embedded processors, @value{GDBN} automatically uses
21502 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
21503 in which case watchpoints using only one debug register are created when
21504 watching variables of scalar types.
21506 You can create an artificial array to watch an arbitrary memory
21507 region using one of the following commands (@pxref{Expressions}):
21510 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
21511 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
21514 PowerPC embedded processors support masked watchpoints. See the discussion
21515 about the @code{mask} argument in @ref{Set Watchpoints}.
21517 @cindex ranged breakpoint
21518 PowerPC embedded processors support hardware accelerated
21519 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
21520 the inferior whenever it executes an instruction at any address within
21521 the range it specifies. To set a ranged breakpoint in @value{GDBN},
21522 use the @code{break-range} command.
21524 @value{GDBN} provides the following PowerPC-specific commands:
21527 @kindex break-range
21528 @item break-range @var{start-location}, @var{end-location}
21529 Set a breakpoint for an address range given by
21530 @var{start-location} and @var{end-location}, which can specify a function name,
21531 a line number, an offset of lines from the current line or from the start
21532 location, or an address of an instruction (see @ref{Specify Location},
21533 for a list of all the possible ways to specify a @var{location}.)
21534 The breakpoint will stop execution of the inferior whenever it
21535 executes an instruction at any address within the specified range,
21536 (including @var{start-location} and @var{end-location}.)
21538 @kindex set powerpc
21539 @item set powerpc soft-float
21540 @itemx show powerpc soft-float
21541 Force @value{GDBN} to use (or not use) a software floating point calling
21542 convention. By default, @value{GDBN} selects the calling convention based
21543 on the selected architecture and the provided executable file.
21545 @item set powerpc vector-abi
21546 @itemx show powerpc vector-abi
21547 Force @value{GDBN} to use the specified calling convention for vector
21548 arguments and return values. The valid options are @samp{auto};
21549 @samp{generic}, to avoid vector registers even if they are present;
21550 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
21551 registers. By default, @value{GDBN} selects the calling convention
21552 based on the selected architecture and the provided executable file.
21554 @item set powerpc exact-watchpoints
21555 @itemx show powerpc exact-watchpoints
21556 Allow @value{GDBN} to use only one debug register when watching a variable
21557 of scalar type, thus assuming that the variable is accessed through the
21558 address of its first byte.
21560 @kindex target dink32
21561 @item target dink32 @var{dev}
21562 DINK32 ROM monitor.
21564 @kindex target ppcbug
21565 @item target ppcbug @var{dev}
21566 @kindex target ppcbug1
21567 @item target ppcbug1 @var{dev}
21568 PPCBUG ROM monitor for PowerPC.
21571 @item target sds @var{dev}
21572 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
21575 @cindex SDS protocol
21576 The following commands specific to the SDS protocol are supported
21580 @item set sdstimeout @var{nsec}
21581 @kindex set sdstimeout
21582 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
21583 default is 2 seconds.
21585 @item show sdstimeout
21586 @kindex show sdstimeout
21587 Show the current value of the SDS timeout.
21589 @item sds @var{command}
21590 @kindex sds@r{, a command}
21591 Send the specified @var{command} string to the SDS monitor.
21596 @subsection HP PA Embedded
21600 @kindex target op50n
21601 @item target op50n @var{dev}
21602 OP50N monitor, running on an OKI HPPA board.
21604 @kindex target w89k
21605 @item target w89k @var{dev}
21606 W89K monitor, running on a Winbond HPPA board.
21611 @subsection Tsqware Sparclet
21615 @value{GDBN} enables developers to debug tasks running on
21616 Sparclet targets from a Unix host.
21617 @value{GDBN} uses code that runs on
21618 both the Unix host and on the Sparclet target. The program
21619 @code{@value{GDBP}} is installed and executed on the Unix host.
21622 @item remotetimeout @var{args}
21623 @kindex remotetimeout
21624 @value{GDBN} supports the option @code{remotetimeout}.
21625 This option is set by the user, and @var{args} represents the number of
21626 seconds @value{GDBN} waits for responses.
21629 @cindex compiling, on Sparclet
21630 When compiling for debugging, include the options @samp{-g} to get debug
21631 information and @samp{-Ttext} to relocate the program to where you wish to
21632 load it on the target. You may also want to add the options @samp{-n} or
21633 @samp{-N} in order to reduce the size of the sections. Example:
21636 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
21639 You can use @code{objdump} to verify that the addresses are what you intended:
21642 sparclet-aout-objdump --headers --syms prog
21645 @cindex running, on Sparclet
21647 your Unix execution search path to find @value{GDBN}, you are ready to
21648 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
21649 (or @code{sparclet-aout-gdb}, depending on your installation).
21651 @value{GDBN} comes up showing the prompt:
21658 * Sparclet File:: Setting the file to debug
21659 * Sparclet Connection:: Connecting to Sparclet
21660 * Sparclet Download:: Sparclet download
21661 * Sparclet Execution:: Running and debugging
21664 @node Sparclet File
21665 @subsubsection Setting File to Debug
21667 The @value{GDBN} command @code{file} lets you choose with program to debug.
21670 (gdbslet) file prog
21674 @value{GDBN} then attempts to read the symbol table of @file{prog}.
21675 @value{GDBN} locates
21676 the file by searching the directories listed in the command search
21678 If the file was compiled with debug information (option @samp{-g}), source
21679 files will be searched as well.
21680 @value{GDBN} locates
21681 the source files by searching the directories listed in the directory search
21682 path (@pxref{Environment, ,Your Program's Environment}).
21684 to find a file, it displays a message such as:
21687 prog: No such file or directory.
21690 When this happens, add the appropriate directories to the search paths with
21691 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
21692 @code{target} command again.
21694 @node Sparclet Connection
21695 @subsubsection Connecting to Sparclet
21697 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
21698 To connect to a target on serial port ``@code{ttya}'', type:
21701 (gdbslet) target sparclet /dev/ttya
21702 Remote target sparclet connected to /dev/ttya
21703 main () at ../prog.c:3
21707 @value{GDBN} displays messages like these:
21713 @node Sparclet Download
21714 @subsubsection Sparclet Download
21716 @cindex download to Sparclet
21717 Once connected to the Sparclet target,
21718 you can use the @value{GDBN}
21719 @code{load} command to download the file from the host to the target.
21720 The file name and load offset should be given as arguments to the @code{load}
21722 Since the file format is aout, the program must be loaded to the starting
21723 address. You can use @code{objdump} to find out what this value is. The load
21724 offset is an offset which is added to the VMA (virtual memory address)
21725 of each of the file's sections.
21726 For instance, if the program
21727 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
21728 and bss at 0x12010170, in @value{GDBN}, type:
21731 (gdbslet) load prog 0x12010000
21732 Loading section .text, size 0xdb0 vma 0x12010000
21735 If the code is loaded at a different address then what the program was linked
21736 to, you may need to use the @code{section} and @code{add-symbol-file} commands
21737 to tell @value{GDBN} where to map the symbol table.
21739 @node Sparclet Execution
21740 @subsubsection Running and Debugging
21742 @cindex running and debugging Sparclet programs
21743 You can now begin debugging the task using @value{GDBN}'s execution control
21744 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
21745 manual for the list of commands.
21749 Breakpoint 1 at 0x12010000: file prog.c, line 3.
21751 Starting program: prog
21752 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
21753 3 char *symarg = 0;
21755 4 char *execarg = "hello!";
21760 @subsection Fujitsu Sparclite
21764 @kindex target sparclite
21765 @item target sparclite @var{dev}
21766 Fujitsu sparclite boards, used only for the purpose of loading.
21767 You must use an additional command to debug the program.
21768 For example: target remote @var{dev} using @value{GDBN} standard
21774 @subsection Zilog Z8000
21777 @cindex simulator, Z8000
21778 @cindex Zilog Z8000 simulator
21780 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
21783 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
21784 unsegmented variant of the Z8000 architecture) or the Z8001 (the
21785 segmented variant). The simulator recognizes which architecture is
21786 appropriate by inspecting the object code.
21789 @item target sim @var{args}
21791 @kindex target sim@r{, with Z8000}
21792 Debug programs on a simulated CPU. If the simulator supports setup
21793 options, specify them via @var{args}.
21797 After specifying this target, you can debug programs for the simulated
21798 CPU in the same style as programs for your host computer; use the
21799 @code{file} command to load a new program image, the @code{run} command
21800 to run your program, and so on.
21802 As well as making available all the usual machine registers
21803 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
21804 additional items of information as specially named registers:
21809 Counts clock-ticks in the simulator.
21812 Counts instructions run in the simulator.
21815 Execution time in 60ths of a second.
21819 You can refer to these values in @value{GDBN} expressions with the usual
21820 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
21821 conditional breakpoint that suspends only after at least 5000
21822 simulated clock ticks.
21825 @subsection Atmel AVR
21828 When configured for debugging the Atmel AVR, @value{GDBN} supports the
21829 following AVR-specific commands:
21832 @item info io_registers
21833 @kindex info io_registers@r{, AVR}
21834 @cindex I/O registers (Atmel AVR)
21835 This command displays information about the AVR I/O registers. For
21836 each register, @value{GDBN} prints its number and value.
21843 When configured for debugging CRIS, @value{GDBN} provides the
21844 following CRIS-specific commands:
21847 @item set cris-version @var{ver}
21848 @cindex CRIS version
21849 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
21850 The CRIS version affects register names and sizes. This command is useful in
21851 case autodetection of the CRIS version fails.
21853 @item show cris-version
21854 Show the current CRIS version.
21856 @item set cris-dwarf2-cfi
21857 @cindex DWARF-2 CFI and CRIS
21858 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
21859 Change to @samp{off} when using @code{gcc-cris} whose version is below
21862 @item show cris-dwarf2-cfi
21863 Show the current state of using DWARF-2 CFI.
21865 @item set cris-mode @var{mode}
21867 Set the current CRIS mode to @var{mode}. It should only be changed when
21868 debugging in guru mode, in which case it should be set to
21869 @samp{guru} (the default is @samp{normal}).
21871 @item show cris-mode
21872 Show the current CRIS mode.
21876 @subsection Renesas Super-H
21879 For the Renesas Super-H processor, @value{GDBN} provides these
21883 @item set sh calling-convention @var{convention}
21884 @kindex set sh calling-convention
21885 Set the calling-convention used when calling functions from @value{GDBN}.
21886 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
21887 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
21888 convention. If the DWARF-2 information of the called function specifies
21889 that the function follows the Renesas calling convention, the function
21890 is called using the Renesas calling convention. If the calling convention
21891 is set to @samp{renesas}, the Renesas calling convention is always used,
21892 regardless of the DWARF-2 information. This can be used to override the
21893 default of @samp{gcc} if debug information is missing, or the compiler
21894 does not emit the DWARF-2 calling convention entry for a function.
21896 @item show sh calling-convention
21897 @kindex show sh calling-convention
21898 Show the current calling convention setting.
21903 @node Architectures
21904 @section Architectures
21906 This section describes characteristics of architectures that affect
21907 all uses of @value{GDBN} with the architecture, both native and cross.
21914 * HPPA:: HP PA architecture
21915 * SPU:: Cell Broadband Engine SPU architecture
21921 @subsection AArch64
21922 @cindex AArch64 support
21924 When @value{GDBN} is debugging the AArch64 architecture, it provides the
21925 following special commands:
21928 @item set debug aarch64
21929 @kindex set debug aarch64
21930 This command determines whether AArch64 architecture-specific debugging
21931 messages are to be displayed.
21933 @item show debug aarch64
21934 Show whether AArch64 debugging messages are displayed.
21939 @subsection x86 Architecture-specific Issues
21942 @item set struct-convention @var{mode}
21943 @kindex set struct-convention
21944 @cindex struct return convention
21945 @cindex struct/union returned in registers
21946 Set the convention used by the inferior to return @code{struct}s and
21947 @code{union}s from functions to @var{mode}. Possible values of
21948 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
21949 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
21950 are returned on the stack, while @code{"reg"} means that a
21951 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
21952 be returned in a register.
21954 @item show struct-convention
21955 @kindex show struct-convention
21956 Show the current setting of the convention to return @code{struct}s
21960 @subsubsection Intel(R) @dfn{Memory Protection Extensions} (MPX).
21961 @cindex Intel(R) Memory Protection Extensions (MPX).
21963 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
21964 @footnote{The register named with capital letters represent the architecture
21965 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
21966 which are the lower bound and upper bound. Bounds are effective addresses or
21967 memory locations. The upper bounds are architecturally represented in 1's
21968 complement form. A bound having lower bound = 0, and upper bound = 0
21969 (1's complement of all bits set) will allow access to the entire address space.
21971 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
21972 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
21973 display the upper bound performing the complement of one operation on the
21974 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
21975 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
21976 can also be noted that the upper bounds are inclusive.
21978 As an example, assume that the register BND0 holds bounds for a pointer having
21979 access allowed for the range between 0x32 and 0x71. The values present on
21980 bnd0raw and bnd registers are presented as follows:
21983 bnd0raw = @{0x32, 0xffffffff8e@}
21984 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
21987 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
21988 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
21989 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
21990 Python, the display includes the memory size, in bits, accessible to
21996 See the following section.
21999 @subsection @acronym{MIPS}
22001 @cindex stack on Alpha
22002 @cindex stack on @acronym{MIPS}
22003 @cindex Alpha stack
22004 @cindex @acronym{MIPS} stack
22005 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
22006 sometimes requires @value{GDBN} to search backward in the object code to
22007 find the beginning of a function.
22009 @cindex response time, @acronym{MIPS} debugging
22010 To improve response time (especially for embedded applications, where
22011 @value{GDBN} may be restricted to a slow serial line for this search)
22012 you may want to limit the size of this search, using one of these
22016 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
22017 @item set heuristic-fence-post @var{limit}
22018 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
22019 search for the beginning of a function. A value of @var{0} (the
22020 default) means there is no limit. However, except for @var{0}, the
22021 larger the limit the more bytes @code{heuristic-fence-post} must search
22022 and therefore the longer it takes to run. You should only need to use
22023 this command when debugging a stripped executable.
22025 @item show heuristic-fence-post
22026 Display the current limit.
22030 These commands are available @emph{only} when @value{GDBN} is configured
22031 for debugging programs on Alpha or @acronym{MIPS} processors.
22033 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
22037 @item set mips abi @var{arg}
22038 @kindex set mips abi
22039 @cindex set ABI for @acronym{MIPS}
22040 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
22041 values of @var{arg} are:
22045 The default ABI associated with the current binary (this is the
22055 @item show mips abi
22056 @kindex show mips abi
22057 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
22059 @item set mips compression @var{arg}
22060 @kindex set mips compression
22061 @cindex code compression, @acronym{MIPS}
22062 Tell @value{GDBN} which @acronym{MIPS} compressed
22063 @acronym{ISA, Instruction Set Architecture} encoding is used by the
22064 inferior. @value{GDBN} uses this for code disassembly and other
22065 internal interpretation purposes. This setting is only referred to
22066 when no executable has been associated with the debugging session or
22067 the executable does not provide information about the encoding it uses.
22068 Otherwise this setting is automatically updated from information
22069 provided by the executable.
22071 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
22072 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
22073 executables containing @acronym{MIPS16} code frequently are not
22074 identified as such.
22076 This setting is ``sticky''; that is, it retains its value across
22077 debugging sessions until reset either explicitly with this command or
22078 implicitly from an executable.
22080 The compiler and/or assembler typically add symbol table annotations to
22081 identify functions compiled for the @acronym{MIPS16} or
22082 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
22083 are present, @value{GDBN} uses them in preference to the global
22084 compressed @acronym{ISA} encoding setting.
22086 @item show mips compression
22087 @kindex show mips compression
22088 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
22089 @value{GDBN} to debug the inferior.
22092 @itemx show mipsfpu
22093 @xref{MIPS Embedded, set mipsfpu}.
22095 @item set mips mask-address @var{arg}
22096 @kindex set mips mask-address
22097 @cindex @acronym{MIPS} addresses, masking
22098 This command determines whether the most-significant 32 bits of 64-bit
22099 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
22100 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
22101 setting, which lets @value{GDBN} determine the correct value.
22103 @item show mips mask-address
22104 @kindex show mips mask-address
22105 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
22108 @item set remote-mips64-transfers-32bit-regs
22109 @kindex set remote-mips64-transfers-32bit-regs
22110 This command controls compatibility with 64-bit @acronym{MIPS} targets that
22111 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
22112 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
22113 and 64 bits for other registers, set this option to @samp{on}.
22115 @item show remote-mips64-transfers-32bit-regs
22116 @kindex show remote-mips64-transfers-32bit-regs
22117 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
22119 @item set debug mips
22120 @kindex set debug mips
22121 This command turns on and off debugging messages for the @acronym{MIPS}-specific
22122 target code in @value{GDBN}.
22124 @item show debug mips
22125 @kindex show debug mips
22126 Show the current setting of @acronym{MIPS} debugging messages.
22132 @cindex HPPA support
22134 When @value{GDBN} is debugging the HP PA architecture, it provides the
22135 following special commands:
22138 @item set debug hppa
22139 @kindex set debug hppa
22140 This command determines whether HPPA architecture-specific debugging
22141 messages are to be displayed.
22143 @item show debug hppa
22144 Show whether HPPA debugging messages are displayed.
22146 @item maint print unwind @var{address}
22147 @kindex maint print unwind@r{, HPPA}
22148 This command displays the contents of the unwind table entry at the
22149 given @var{address}.
22155 @subsection Cell Broadband Engine SPU architecture
22156 @cindex Cell Broadband Engine
22159 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
22160 it provides the following special commands:
22163 @item info spu event
22165 Display SPU event facility status. Shows current event mask
22166 and pending event status.
22168 @item info spu signal
22169 Display SPU signal notification facility status. Shows pending
22170 signal-control word and signal notification mode of both signal
22171 notification channels.
22173 @item info spu mailbox
22174 Display SPU mailbox facility status. Shows all pending entries,
22175 in order of processing, in each of the SPU Write Outbound,
22176 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
22179 Display MFC DMA status. Shows all pending commands in the MFC
22180 DMA queue. For each entry, opcode, tag, class IDs, effective
22181 and local store addresses and transfer size are shown.
22183 @item info spu proxydma
22184 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
22185 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
22186 and local store addresses and transfer size are shown.
22190 When @value{GDBN} is debugging a combined PowerPC/SPU application
22191 on the Cell Broadband Engine, it provides in addition the following
22195 @item set spu stop-on-load @var{arg}
22197 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
22198 will give control to the user when a new SPE thread enters its @code{main}
22199 function. The default is @code{off}.
22201 @item show spu stop-on-load
22203 Show whether to stop for new SPE threads.
22205 @item set spu auto-flush-cache @var{arg}
22206 Set whether to automatically flush the software-managed cache. When set to
22207 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
22208 cache to be flushed whenever SPE execution stops. This provides a consistent
22209 view of PowerPC memory that is accessed via the cache. If an application
22210 does not use the software-managed cache, this option has no effect.
22212 @item show spu auto-flush-cache
22213 Show whether to automatically flush the software-managed cache.
22218 @subsection PowerPC
22219 @cindex PowerPC architecture
22221 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
22222 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
22223 numbers stored in the floating point registers. These values must be stored
22224 in two consecutive registers, always starting at an even register like
22225 @code{f0} or @code{f2}.
22227 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
22228 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
22229 @code{f2} and @code{f3} for @code{$dl1} and so on.
22231 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
22232 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
22235 @subsection Nios II
22236 @cindex Nios II architecture
22238 When @value{GDBN} is debugging the Nios II architecture,
22239 it provides the following special commands:
22243 @item set debug nios2
22244 @kindex set debug nios2
22245 This command turns on and off debugging messages for the Nios II
22246 target code in @value{GDBN}.
22248 @item show debug nios2
22249 @kindex show debug nios2
22250 Show the current setting of Nios II debugging messages.
22253 @node Controlling GDB
22254 @chapter Controlling @value{GDBN}
22256 You can alter the way @value{GDBN} interacts with you by using the
22257 @code{set} command. For commands controlling how @value{GDBN} displays
22258 data, see @ref{Print Settings, ,Print Settings}. Other settings are
22263 * Editing:: Command editing
22264 * Command History:: Command history
22265 * Screen Size:: Screen size
22266 * Numbers:: Numbers
22267 * ABI:: Configuring the current ABI
22268 * Auto-loading:: Automatically loading associated files
22269 * Messages/Warnings:: Optional warnings and messages
22270 * Debugging Output:: Optional messages about internal happenings
22271 * Other Misc Settings:: Other Miscellaneous Settings
22279 @value{GDBN} indicates its readiness to read a command by printing a string
22280 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
22281 can change the prompt string with the @code{set prompt} command. For
22282 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
22283 the prompt in one of the @value{GDBN} sessions so that you can always tell
22284 which one you are talking to.
22286 @emph{Note:} @code{set prompt} does not add a space for you after the
22287 prompt you set. This allows you to set a prompt which ends in a space
22288 or a prompt that does not.
22292 @item set prompt @var{newprompt}
22293 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
22295 @kindex show prompt
22297 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
22300 Versions of @value{GDBN} that ship with Python scripting enabled have
22301 prompt extensions. The commands for interacting with these extensions
22305 @kindex set extended-prompt
22306 @item set extended-prompt @var{prompt}
22307 Set an extended prompt that allows for substitutions.
22308 @xref{gdb.prompt}, for a list of escape sequences that can be used for
22309 substitution. Any escape sequences specified as part of the prompt
22310 string are replaced with the corresponding strings each time the prompt
22316 set extended-prompt Current working directory: \w (gdb)
22319 Note that when an extended-prompt is set, it takes control of the
22320 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
22322 @kindex show extended-prompt
22323 @item show extended-prompt
22324 Prints the extended prompt. Any escape sequences specified as part of
22325 the prompt string with @code{set extended-prompt}, are replaced with the
22326 corresponding strings each time the prompt is displayed.
22330 @section Command Editing
22332 @cindex command line editing
22334 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
22335 @sc{gnu} library provides consistent behavior for programs which provide a
22336 command line interface to the user. Advantages are @sc{gnu} Emacs-style
22337 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
22338 substitution, and a storage and recall of command history across
22339 debugging sessions.
22341 You may control the behavior of command line editing in @value{GDBN} with the
22342 command @code{set}.
22345 @kindex set editing
22348 @itemx set editing on
22349 Enable command line editing (enabled by default).
22351 @item set editing off
22352 Disable command line editing.
22354 @kindex show editing
22356 Show whether command line editing is enabled.
22359 @ifset SYSTEM_READLINE
22360 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
22362 @ifclear SYSTEM_READLINE
22363 @xref{Command Line Editing},
22365 for more details about the Readline
22366 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
22367 encouraged to read that chapter.
22369 @node Command History
22370 @section Command History
22371 @cindex command history
22373 @value{GDBN} can keep track of the commands you type during your
22374 debugging sessions, so that you can be certain of precisely what
22375 happened. Use these commands to manage the @value{GDBN} command
22378 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
22379 package, to provide the history facility.
22380 @ifset SYSTEM_READLINE
22381 @xref{Using History Interactively, , , history, GNU History Library},
22383 @ifclear SYSTEM_READLINE
22384 @xref{Using History Interactively},
22386 for the detailed description of the History library.
22388 To issue a command to @value{GDBN} without affecting certain aspects of
22389 the state which is seen by users, prefix it with @samp{server }
22390 (@pxref{Server Prefix}). This
22391 means that this command will not affect the command history, nor will it
22392 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
22393 pressed on a line by itself.
22395 @cindex @code{server}, command prefix
22396 The server prefix does not affect the recording of values into the value
22397 history; to print a value without recording it into the value history,
22398 use the @code{output} command instead of the @code{print} command.
22400 Here is the description of @value{GDBN} commands related to command
22404 @cindex history substitution
22405 @cindex history file
22406 @kindex set history filename
22407 @cindex @env{GDBHISTFILE}, environment variable
22408 @item set history filename @var{fname}
22409 Set the name of the @value{GDBN} command history file to @var{fname}.
22410 This is the file where @value{GDBN} reads an initial command history
22411 list, and where it writes the command history from this session when it
22412 exits. You can access this list through history expansion or through
22413 the history command editing characters listed below. This file defaults
22414 to the value of the environment variable @code{GDBHISTFILE}, or to
22415 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
22418 @cindex save command history
22419 @kindex set history save
22420 @item set history save
22421 @itemx set history save on
22422 Record command history in a file, whose name may be specified with the
22423 @code{set history filename} command. By default, this option is disabled.
22425 @item set history save off
22426 Stop recording command history in a file.
22428 @cindex history size
22429 @kindex set history size
22430 @cindex @env{HISTSIZE}, environment variable
22431 @item set history size @var{size}
22432 @itemx set history size unlimited
22433 Set the number of commands which @value{GDBN} keeps in its history list.
22434 This defaults to the value of the environment variable
22435 @code{HISTSIZE}, or to 256 if this variable is not set. If @var{size}
22436 is @code{unlimited}, the number of commands @value{GDBN} keeps in the
22437 history list is unlimited.
22440 History expansion assigns special meaning to the character @kbd{!}.
22441 @ifset SYSTEM_READLINE
22442 @xref{Event Designators, , , history, GNU History Library},
22444 @ifclear SYSTEM_READLINE
22445 @xref{Event Designators},
22449 @cindex history expansion, turn on/off
22450 Since @kbd{!} is also the logical not operator in C, history expansion
22451 is off by default. If you decide to enable history expansion with the
22452 @code{set history expansion on} command, you may sometimes need to
22453 follow @kbd{!} (when it is used as logical not, in an expression) with
22454 a space or a tab to prevent it from being expanded. The readline
22455 history facilities do not attempt substitution on the strings
22456 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
22458 The commands to control history expansion are:
22461 @item set history expansion on
22462 @itemx set history expansion
22463 @kindex set history expansion
22464 Enable history expansion. History expansion is off by default.
22466 @item set history expansion off
22467 Disable history expansion.
22470 @kindex show history
22472 @itemx show history filename
22473 @itemx show history save
22474 @itemx show history size
22475 @itemx show history expansion
22476 These commands display the state of the @value{GDBN} history parameters.
22477 @code{show history} by itself displays all four states.
22482 @kindex show commands
22483 @cindex show last commands
22484 @cindex display command history
22485 @item show commands
22486 Display the last ten commands in the command history.
22488 @item show commands @var{n}
22489 Print ten commands centered on command number @var{n}.
22491 @item show commands +
22492 Print ten commands just after the commands last printed.
22496 @section Screen Size
22497 @cindex size of screen
22498 @cindex screen size
22501 @cindex pauses in output
22503 Certain commands to @value{GDBN} may produce large amounts of
22504 information output to the screen. To help you read all of it,
22505 @value{GDBN} pauses and asks you for input at the end of each page of
22506 output. Type @key{RET} when you want to continue the output, or @kbd{q}
22507 to discard the remaining output. Also, the screen width setting
22508 determines when to wrap lines of output. Depending on what is being
22509 printed, @value{GDBN} tries to break the line at a readable place,
22510 rather than simply letting it overflow onto the following line.
22512 Normally @value{GDBN} knows the size of the screen from the terminal
22513 driver software. For example, on Unix @value{GDBN} uses the termcap data base
22514 together with the value of the @code{TERM} environment variable and the
22515 @code{stty rows} and @code{stty cols} settings. If this is not correct,
22516 you can override it with the @code{set height} and @code{set
22523 @kindex show height
22524 @item set height @var{lpp}
22525 @itemx set height unlimited
22527 @itemx set width @var{cpl}
22528 @itemx set width unlimited
22530 These @code{set} commands specify a screen height of @var{lpp} lines and
22531 a screen width of @var{cpl} characters. The associated @code{show}
22532 commands display the current settings.
22534 If you specify a height of either @code{unlimited} or zero lines,
22535 @value{GDBN} does not pause during output no matter how long the
22536 output is. This is useful if output is to a file or to an editor
22539 Likewise, you can specify @samp{set width unlimited} or @samp{set
22540 width 0} to prevent @value{GDBN} from wrapping its output.
22542 @item set pagination on
22543 @itemx set pagination off
22544 @kindex set pagination
22545 Turn the output pagination on or off; the default is on. Turning
22546 pagination off is the alternative to @code{set height unlimited}. Note that
22547 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
22548 Options, -batch}) also automatically disables pagination.
22550 @item show pagination
22551 @kindex show pagination
22552 Show the current pagination mode.
22557 @cindex number representation
22558 @cindex entering numbers
22560 You can always enter numbers in octal, decimal, or hexadecimal in
22561 @value{GDBN} by the usual conventions: octal numbers begin with
22562 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
22563 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
22564 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
22565 10; likewise, the default display for numbers---when no particular
22566 format is specified---is base 10. You can change the default base for
22567 both input and output with the commands described below.
22570 @kindex set input-radix
22571 @item set input-radix @var{base}
22572 Set the default base for numeric input. Supported choices
22573 for @var{base} are decimal 8, 10, or 16. The base must itself be
22574 specified either unambiguously or using the current input radix; for
22578 set input-radix 012
22579 set input-radix 10.
22580 set input-radix 0xa
22584 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
22585 leaves the input radix unchanged, no matter what it was, since
22586 @samp{10}, being without any leading or trailing signs of its base, is
22587 interpreted in the current radix. Thus, if the current radix is 16,
22588 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
22591 @kindex set output-radix
22592 @item set output-radix @var{base}
22593 Set the default base for numeric display. Supported choices
22594 for @var{base} are decimal 8, 10, or 16. The base must itself be
22595 specified either unambiguously or using the current input radix.
22597 @kindex show input-radix
22598 @item show input-radix
22599 Display the current default base for numeric input.
22601 @kindex show output-radix
22602 @item show output-radix
22603 Display the current default base for numeric display.
22605 @item set radix @r{[}@var{base}@r{]}
22609 These commands set and show the default base for both input and output
22610 of numbers. @code{set radix} sets the radix of input and output to
22611 the same base; without an argument, it resets the radix back to its
22612 default value of 10.
22617 @section Configuring the Current ABI
22619 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
22620 application automatically. However, sometimes you need to override its
22621 conclusions. Use these commands to manage @value{GDBN}'s view of the
22627 @cindex Newlib OS ABI and its influence on the longjmp handling
22629 One @value{GDBN} configuration can debug binaries for multiple operating
22630 system targets, either via remote debugging or native emulation.
22631 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
22632 but you can override its conclusion using the @code{set osabi} command.
22633 One example where this is useful is in debugging of binaries which use
22634 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
22635 not have the same identifying marks that the standard C library for your
22638 When @value{GDBN} is debugging the AArch64 architecture, it provides a
22639 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
22640 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
22641 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
22645 Show the OS ABI currently in use.
22648 With no argument, show the list of registered available OS ABI's.
22650 @item set osabi @var{abi}
22651 Set the current OS ABI to @var{abi}.
22654 @cindex float promotion
22656 Generally, the way that an argument of type @code{float} is passed to a
22657 function depends on whether the function is prototyped. For a prototyped
22658 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
22659 according to the architecture's convention for @code{float}. For unprototyped
22660 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
22661 @code{double} and then passed.
22663 Unfortunately, some forms of debug information do not reliably indicate whether
22664 a function is prototyped. If @value{GDBN} calls a function that is not marked
22665 as prototyped, it consults @kbd{set coerce-float-to-double}.
22668 @kindex set coerce-float-to-double
22669 @item set coerce-float-to-double
22670 @itemx set coerce-float-to-double on
22671 Arguments of type @code{float} will be promoted to @code{double} when passed
22672 to an unprototyped function. This is the default setting.
22674 @item set coerce-float-to-double off
22675 Arguments of type @code{float} will be passed directly to unprototyped
22678 @kindex show coerce-float-to-double
22679 @item show coerce-float-to-double
22680 Show the current setting of promoting @code{float} to @code{double}.
22684 @kindex show cp-abi
22685 @value{GDBN} needs to know the ABI used for your program's C@t{++}
22686 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
22687 used to build your application. @value{GDBN} only fully supports
22688 programs with a single C@t{++} ABI; if your program contains code using
22689 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
22690 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
22691 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
22692 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
22693 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
22694 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
22699 Show the C@t{++} ABI currently in use.
22702 With no argument, show the list of supported C@t{++} ABI's.
22704 @item set cp-abi @var{abi}
22705 @itemx set cp-abi auto
22706 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
22710 @section Automatically loading associated files
22711 @cindex auto-loading
22713 @value{GDBN} sometimes reads files with commands and settings automatically,
22714 without being explicitly told so by the user. We call this feature
22715 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
22716 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
22717 results or introduce security risks (e.g., if the file comes from untrusted
22721 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
22722 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
22724 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
22725 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
22728 There are various kinds of files @value{GDBN} can automatically load.
22729 In addition to these files, @value{GDBN} supports auto-loading code written
22730 in various extension languages. @xref{Auto-loading extensions}.
22732 Note that loading of these associated files (including the local @file{.gdbinit}
22733 file) requires accordingly configured @code{auto-load safe-path}
22734 (@pxref{Auto-loading safe path}).
22736 For these reasons, @value{GDBN} includes commands and options to let you
22737 control when to auto-load files and which files should be auto-loaded.
22740 @anchor{set auto-load off}
22741 @kindex set auto-load off
22742 @item set auto-load off
22743 Globally disable loading of all auto-loaded files.
22744 You may want to use this command with the @samp{-iex} option
22745 (@pxref{Option -init-eval-command}) such as:
22747 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
22750 Be aware that system init file (@pxref{System-wide configuration})
22751 and init files from your home directory (@pxref{Home Directory Init File})
22752 still get read (as they come from generally trusted directories).
22753 To prevent @value{GDBN} from auto-loading even those init files, use the
22754 @option{-nx} option (@pxref{Mode Options}), in addition to
22755 @code{set auto-load no}.
22757 @anchor{show auto-load}
22758 @kindex show auto-load
22759 @item show auto-load
22760 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
22764 (gdb) show auto-load
22765 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
22766 libthread-db: Auto-loading of inferior specific libthread_db is on.
22767 local-gdbinit: Auto-loading of .gdbinit script from current directory
22769 python-scripts: Auto-loading of Python scripts is on.
22770 safe-path: List of directories from which it is safe to auto-load files
22771 is $debugdir:$datadir/auto-load.
22772 scripts-directory: List of directories from which to load auto-loaded scripts
22773 is $debugdir:$datadir/auto-load.
22776 @anchor{info auto-load}
22777 @kindex info auto-load
22778 @item info auto-load
22779 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
22783 (gdb) info auto-load
22786 Yes /home/user/gdb/gdb-gdb.gdb
22787 libthread-db: No auto-loaded libthread-db.
22788 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
22792 Yes /home/user/gdb/gdb-gdb.py
22796 These are @value{GDBN} control commands for the auto-loading:
22798 @multitable @columnfractions .5 .5
22799 @item @xref{set auto-load off}.
22800 @tab Disable auto-loading globally.
22801 @item @xref{show auto-load}.
22802 @tab Show setting of all kinds of files.
22803 @item @xref{info auto-load}.
22804 @tab Show state of all kinds of files.
22805 @item @xref{set auto-load gdb-scripts}.
22806 @tab Control for @value{GDBN} command scripts.
22807 @item @xref{show auto-load gdb-scripts}.
22808 @tab Show setting of @value{GDBN} command scripts.
22809 @item @xref{info auto-load gdb-scripts}.
22810 @tab Show state of @value{GDBN} command scripts.
22811 @item @xref{set auto-load python-scripts}.
22812 @tab Control for @value{GDBN} Python scripts.
22813 @item @xref{show auto-load python-scripts}.
22814 @tab Show setting of @value{GDBN} Python scripts.
22815 @item @xref{info auto-load python-scripts}.
22816 @tab Show state of @value{GDBN} Python scripts.
22817 @item @xref{set auto-load guile-scripts}.
22818 @tab Control for @value{GDBN} Guile scripts.
22819 @item @xref{show auto-load guile-scripts}.
22820 @tab Show setting of @value{GDBN} Guile scripts.
22821 @item @xref{info auto-load guile-scripts}.
22822 @tab Show state of @value{GDBN} Guile scripts.
22823 @item @xref{set auto-load scripts-directory}.
22824 @tab Control for @value{GDBN} auto-loaded scripts location.
22825 @item @xref{show auto-load scripts-directory}.
22826 @tab Show @value{GDBN} auto-loaded scripts location.
22827 @item @xref{add-auto-load-scripts-directory}.
22828 @tab Add directory for auto-loaded scripts location list.
22829 @item @xref{set auto-load local-gdbinit}.
22830 @tab Control for init file in the current directory.
22831 @item @xref{show auto-load local-gdbinit}.
22832 @tab Show setting of init file in the current directory.
22833 @item @xref{info auto-load local-gdbinit}.
22834 @tab Show state of init file in the current directory.
22835 @item @xref{set auto-load libthread-db}.
22836 @tab Control for thread debugging library.
22837 @item @xref{show auto-load libthread-db}.
22838 @tab Show setting of thread debugging library.
22839 @item @xref{info auto-load libthread-db}.
22840 @tab Show state of thread debugging library.
22841 @item @xref{set auto-load safe-path}.
22842 @tab Control directories trusted for automatic loading.
22843 @item @xref{show auto-load safe-path}.
22844 @tab Show directories trusted for automatic loading.
22845 @item @xref{add-auto-load-safe-path}.
22846 @tab Add directory trusted for automatic loading.
22849 @node Init File in the Current Directory
22850 @subsection Automatically loading init file in the current directory
22851 @cindex auto-loading init file in the current directory
22853 By default, @value{GDBN} reads and executes the canned sequences of commands
22854 from init file (if any) in the current working directory,
22855 see @ref{Init File in the Current Directory during Startup}.
22857 Note that loading of this local @file{.gdbinit} file also requires accordingly
22858 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22861 @anchor{set auto-load local-gdbinit}
22862 @kindex set auto-load local-gdbinit
22863 @item set auto-load local-gdbinit [on|off]
22864 Enable or disable the auto-loading of canned sequences of commands
22865 (@pxref{Sequences}) found in init file in the current directory.
22867 @anchor{show auto-load local-gdbinit}
22868 @kindex show auto-load local-gdbinit
22869 @item show auto-load local-gdbinit
22870 Show whether auto-loading of canned sequences of commands from init file in the
22871 current directory is enabled or disabled.
22873 @anchor{info auto-load local-gdbinit}
22874 @kindex info auto-load local-gdbinit
22875 @item info auto-load local-gdbinit
22876 Print whether canned sequences of commands from init file in the
22877 current directory have been auto-loaded.
22880 @node libthread_db.so.1 file
22881 @subsection Automatically loading thread debugging library
22882 @cindex auto-loading libthread_db.so.1
22884 This feature is currently present only on @sc{gnu}/Linux native hosts.
22886 @value{GDBN} reads in some cases thread debugging library from places specific
22887 to the inferior (@pxref{set libthread-db-search-path}).
22889 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
22890 without checking this @samp{set auto-load libthread-db} switch as system
22891 libraries have to be trusted in general. In all other cases of
22892 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
22893 auto-load libthread-db} is enabled before trying to open such thread debugging
22896 Note that loading of this debugging library also requires accordingly configured
22897 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22900 @anchor{set auto-load libthread-db}
22901 @kindex set auto-load libthread-db
22902 @item set auto-load libthread-db [on|off]
22903 Enable or disable the auto-loading of inferior specific thread debugging library.
22905 @anchor{show auto-load libthread-db}
22906 @kindex show auto-load libthread-db
22907 @item show auto-load libthread-db
22908 Show whether auto-loading of inferior specific thread debugging library is
22909 enabled or disabled.
22911 @anchor{info auto-load libthread-db}
22912 @kindex info auto-load libthread-db
22913 @item info auto-load libthread-db
22914 Print the list of all loaded inferior specific thread debugging libraries and
22915 for each such library print list of inferior @var{pid}s using it.
22918 @node Auto-loading safe path
22919 @subsection Security restriction for auto-loading
22920 @cindex auto-loading safe-path
22922 As the files of inferior can come from untrusted source (such as submitted by
22923 an application user) @value{GDBN} does not always load any files automatically.
22924 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
22925 directories trusted for loading files not explicitly requested by user.
22926 Each directory can also be a shell wildcard pattern.
22928 If the path is not set properly you will see a warning and the file will not
22933 Reading symbols from /home/user/gdb/gdb...done.
22934 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
22935 declined by your `auto-load safe-path' set
22936 to "$debugdir:$datadir/auto-load".
22937 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
22938 declined by your `auto-load safe-path' set
22939 to "$debugdir:$datadir/auto-load".
22943 To instruct @value{GDBN} to go ahead and use the init files anyway,
22944 invoke @value{GDBN} like this:
22947 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
22950 The list of trusted directories is controlled by the following commands:
22953 @anchor{set auto-load safe-path}
22954 @kindex set auto-load safe-path
22955 @item set auto-load safe-path @r{[}@var{directories}@r{]}
22956 Set the list of directories (and their subdirectories) trusted for automatic
22957 loading and execution of scripts. You can also enter a specific trusted file.
22958 Each directory can also be a shell wildcard pattern; wildcards do not match
22959 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
22960 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
22961 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
22962 its default value as specified during @value{GDBN} compilation.
22964 The list of directories uses path separator (@samp{:} on GNU and Unix
22965 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
22966 to the @env{PATH} environment variable.
22968 @anchor{show auto-load safe-path}
22969 @kindex show auto-load safe-path
22970 @item show auto-load safe-path
22971 Show the list of directories trusted for automatic loading and execution of
22974 @anchor{add-auto-load-safe-path}
22975 @kindex add-auto-load-safe-path
22976 @item add-auto-load-safe-path
22977 Add an entry (or list of entries) to the list of directories trusted for
22978 automatic loading and execution of scripts. Multiple entries may be delimited
22979 by the host platform path separator in use.
22982 This variable defaults to what @code{--with-auto-load-dir} has been configured
22983 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
22984 substitution applies the same as for @ref{set auto-load scripts-directory}.
22985 The default @code{set auto-load safe-path} value can be also overriden by
22986 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
22988 Setting this variable to @file{/} disables this security protection,
22989 corresponding @value{GDBN} configuration option is
22990 @option{--without-auto-load-safe-path}.
22991 This variable is supposed to be set to the system directories writable by the
22992 system superuser only. Users can add their source directories in init files in
22993 their home directories (@pxref{Home Directory Init File}). See also deprecated
22994 init file in the current directory
22995 (@pxref{Init File in the Current Directory during Startup}).
22997 To force @value{GDBN} to load the files it declined to load in the previous
22998 example, you could use one of the following ways:
23001 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
23002 Specify this trusted directory (or a file) as additional component of the list.
23003 You have to specify also any existing directories displayed by
23004 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
23006 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
23007 Specify this directory as in the previous case but just for a single
23008 @value{GDBN} session.
23010 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
23011 Disable auto-loading safety for a single @value{GDBN} session.
23012 This assumes all the files you debug during this @value{GDBN} session will come
23013 from trusted sources.
23015 @item @kbd{./configure --without-auto-load-safe-path}
23016 During compilation of @value{GDBN} you may disable any auto-loading safety.
23017 This assumes all the files you will ever debug with this @value{GDBN} come from
23021 On the other hand you can also explicitly forbid automatic files loading which
23022 also suppresses any such warning messages:
23025 @item @kbd{gdb -iex "set auto-load no" @dots{}}
23026 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
23028 @item @file{~/.gdbinit}: @samp{set auto-load no}
23029 Disable auto-loading globally for the user
23030 (@pxref{Home Directory Init File}). While it is improbable, you could also
23031 use system init file instead (@pxref{System-wide configuration}).
23034 This setting applies to the file names as entered by user. If no entry matches
23035 @value{GDBN} tries as a last resort to also resolve all the file names into
23036 their canonical form (typically resolving symbolic links) and compare the
23037 entries again. @value{GDBN} already canonicalizes most of the filenames on its
23038 own before starting the comparison so a canonical form of directories is
23039 recommended to be entered.
23041 @node Auto-loading verbose mode
23042 @subsection Displaying files tried for auto-load
23043 @cindex auto-loading verbose mode
23045 For better visibility of all the file locations where you can place scripts to
23046 be auto-loaded with inferior --- or to protect yourself against accidental
23047 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
23048 all the files attempted to be loaded. Both existing and non-existing files may
23051 For example the list of directories from which it is safe to auto-load files
23052 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
23053 may not be too obvious while setting it up.
23056 (gdb) set debug auto-load on
23057 (gdb) file ~/src/t/true
23058 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
23059 for objfile "/tmp/true".
23060 auto-load: Updating directories of "/usr:/opt".
23061 auto-load: Using directory "/usr".
23062 auto-load: Using directory "/opt".
23063 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
23064 by your `auto-load safe-path' set to "/usr:/opt".
23068 @anchor{set debug auto-load}
23069 @kindex set debug auto-load
23070 @item set debug auto-load [on|off]
23071 Set whether to print the filenames attempted to be auto-loaded.
23073 @anchor{show debug auto-load}
23074 @kindex show debug auto-load
23075 @item show debug auto-load
23076 Show whether printing of the filenames attempted to be auto-loaded is turned
23080 @node Messages/Warnings
23081 @section Optional Warnings and Messages
23083 @cindex verbose operation
23084 @cindex optional warnings
23085 By default, @value{GDBN} is silent about its inner workings. If you are
23086 running on a slow machine, you may want to use the @code{set verbose}
23087 command. This makes @value{GDBN} tell you when it does a lengthy
23088 internal operation, so you will not think it has crashed.
23090 Currently, the messages controlled by @code{set verbose} are those
23091 which announce that the symbol table for a source file is being read;
23092 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
23095 @kindex set verbose
23096 @item set verbose on
23097 Enables @value{GDBN} output of certain informational messages.
23099 @item set verbose off
23100 Disables @value{GDBN} output of certain informational messages.
23102 @kindex show verbose
23104 Displays whether @code{set verbose} is on or off.
23107 By default, if @value{GDBN} encounters bugs in the symbol table of an
23108 object file, it is silent; but if you are debugging a compiler, you may
23109 find this information useful (@pxref{Symbol Errors, ,Errors Reading
23114 @kindex set complaints
23115 @item set complaints @var{limit}
23116 Permits @value{GDBN} to output @var{limit} complaints about each type of
23117 unusual symbols before becoming silent about the problem. Set
23118 @var{limit} to zero to suppress all complaints; set it to a large number
23119 to prevent complaints from being suppressed.
23121 @kindex show complaints
23122 @item show complaints
23123 Displays how many symbol complaints @value{GDBN} is permitted to produce.
23127 @anchor{confirmation requests}
23128 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
23129 lot of stupid questions to confirm certain commands. For example, if
23130 you try to run a program which is already running:
23134 The program being debugged has been started already.
23135 Start it from the beginning? (y or n)
23138 If you are willing to unflinchingly face the consequences of your own
23139 commands, you can disable this ``feature'':
23143 @kindex set confirm
23145 @cindex confirmation
23146 @cindex stupid questions
23147 @item set confirm off
23148 Disables confirmation requests. Note that running @value{GDBN} with
23149 the @option{--batch} option (@pxref{Mode Options, -batch}) also
23150 automatically disables confirmation requests.
23152 @item set confirm on
23153 Enables confirmation requests (the default).
23155 @kindex show confirm
23157 Displays state of confirmation requests.
23161 @cindex command tracing
23162 If you need to debug user-defined commands or sourced files you may find it
23163 useful to enable @dfn{command tracing}. In this mode each command will be
23164 printed as it is executed, prefixed with one or more @samp{+} symbols, the
23165 quantity denoting the call depth of each command.
23168 @kindex set trace-commands
23169 @cindex command scripts, debugging
23170 @item set trace-commands on
23171 Enable command tracing.
23172 @item set trace-commands off
23173 Disable command tracing.
23174 @item show trace-commands
23175 Display the current state of command tracing.
23178 @node Debugging Output
23179 @section Optional Messages about Internal Happenings
23180 @cindex optional debugging messages
23182 @value{GDBN} has commands that enable optional debugging messages from
23183 various @value{GDBN} subsystems; normally these commands are of
23184 interest to @value{GDBN} maintainers, or when reporting a bug. This
23185 section documents those commands.
23188 @kindex set exec-done-display
23189 @item set exec-done-display
23190 Turns on or off the notification of asynchronous commands'
23191 completion. When on, @value{GDBN} will print a message when an
23192 asynchronous command finishes its execution. The default is off.
23193 @kindex show exec-done-display
23194 @item show exec-done-display
23195 Displays the current setting of asynchronous command completion
23198 @cindex ARM AArch64
23199 @item set debug aarch64
23200 Turns on or off display of debugging messages related to ARM AArch64.
23201 The default is off.
23203 @item show debug aarch64
23204 Displays the current state of displaying debugging messages related to
23206 @cindex gdbarch debugging info
23207 @cindex architecture debugging info
23208 @item set debug arch
23209 Turns on or off display of gdbarch debugging info. The default is off
23210 @item show debug arch
23211 Displays the current state of displaying gdbarch debugging info.
23212 @item set debug aix-solib
23213 @cindex AIX shared library debugging
23214 Control display of debugging messages from the AIX shared library
23215 support module. The default is off.
23216 @item show debug aix-thread
23217 Show the current state of displaying AIX shared library debugging messages.
23218 @item set debug aix-thread
23219 @cindex AIX threads
23220 Display debugging messages about inner workings of the AIX thread
23222 @item show debug aix-thread
23223 Show the current state of AIX thread debugging info display.
23224 @item set debug check-physname
23226 Check the results of the ``physname'' computation. When reading DWARF
23227 debugging information for C@t{++}, @value{GDBN} attempts to compute
23228 each entity's name. @value{GDBN} can do this computation in two
23229 different ways, depending on exactly what information is present.
23230 When enabled, this setting causes @value{GDBN} to compute the names
23231 both ways and display any discrepancies.
23232 @item show debug check-physname
23233 Show the current state of ``physname'' checking.
23234 @item set debug coff-pe-read
23235 @cindex COFF/PE exported symbols
23236 Control display of debugging messages related to reading of COFF/PE
23237 exported symbols. The default is off.
23238 @item show debug coff-pe-read
23239 Displays the current state of displaying debugging messages related to
23240 reading of COFF/PE exported symbols.
23241 @item set debug dwarf2-die
23242 @cindex DWARF2 DIEs
23243 Dump DWARF2 DIEs after they are read in.
23244 The value is the number of nesting levels to print.
23245 A value of zero turns off the display.
23246 @item show debug dwarf2-die
23247 Show the current state of DWARF2 DIE debugging.
23248 @item set debug dwarf2-read
23249 @cindex DWARF2 Reading
23250 Turns on or off display of debugging messages related to reading
23251 DWARF debug info. The default is 0 (off).
23252 A value of 1 provides basic information.
23253 A value greater than 1 provides more verbose information.
23254 @item show debug dwarf2-read
23255 Show the current state of DWARF2 reader debugging.
23256 @item set debug displaced
23257 @cindex displaced stepping debugging info
23258 Turns on or off display of @value{GDBN} debugging info for the
23259 displaced stepping support. The default is off.
23260 @item show debug displaced
23261 Displays the current state of displaying @value{GDBN} debugging info
23262 related to displaced stepping.
23263 @item set debug event
23264 @cindex event debugging info
23265 Turns on or off display of @value{GDBN} event debugging info. The
23267 @item show debug event
23268 Displays the current state of displaying @value{GDBN} event debugging
23270 @item set debug expression
23271 @cindex expression debugging info
23272 Turns on or off display of debugging info about @value{GDBN}
23273 expression parsing. The default is off.
23274 @item show debug expression
23275 Displays the current state of displaying debugging info about
23276 @value{GDBN} expression parsing.
23277 @item set debug frame
23278 @cindex frame debugging info
23279 Turns on or off display of @value{GDBN} frame debugging info. The
23281 @item show debug frame
23282 Displays the current state of displaying @value{GDBN} frame debugging
23284 @item set debug gnu-nat
23285 @cindex @sc{gnu}/Hurd debug messages
23286 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
23287 @item show debug gnu-nat
23288 Show the current state of @sc{gnu}/Hurd debugging messages.
23289 @item set debug infrun
23290 @cindex inferior debugging info
23291 Turns on or off display of @value{GDBN} debugging info for running the inferior.
23292 The default is off. @file{infrun.c} contains GDB's runtime state machine used
23293 for implementing operations such as single-stepping the inferior.
23294 @item show debug infrun
23295 Displays the current state of @value{GDBN} inferior debugging.
23296 @item set debug jit
23297 @cindex just-in-time compilation, debugging messages
23298 Turns on or off debugging messages from JIT debug support.
23299 @item show debug jit
23300 Displays the current state of @value{GDBN} JIT debugging.
23301 @item set debug lin-lwp
23302 @cindex @sc{gnu}/Linux LWP debug messages
23303 @cindex Linux lightweight processes
23304 Turns on or off debugging messages from the Linux LWP debug support.
23305 @item show debug lin-lwp
23306 Show the current state of Linux LWP debugging messages.
23307 @item set debug mach-o
23308 @cindex Mach-O symbols processing
23309 Control display of debugging messages related to Mach-O symbols
23310 processing. The default is off.
23311 @item show debug mach-o
23312 Displays the current state of displaying debugging messages related to
23313 reading of COFF/PE exported symbols.
23314 @item set debug notification
23315 @cindex remote async notification debugging info
23316 Turns on or off debugging messages about remote async notification.
23317 The default is off.
23318 @item show debug notification
23319 Displays the current state of remote async notification debugging messages.
23320 @item set debug observer
23321 @cindex observer debugging info
23322 Turns on or off display of @value{GDBN} observer debugging. This
23323 includes info such as the notification of observable events.
23324 @item show debug observer
23325 Displays the current state of observer debugging.
23326 @item set debug overload
23327 @cindex C@t{++} overload debugging info
23328 Turns on or off display of @value{GDBN} C@t{++} overload debugging
23329 info. This includes info such as ranking of functions, etc. The default
23331 @item show debug overload
23332 Displays the current state of displaying @value{GDBN} C@t{++} overload
23334 @cindex expression parser, debugging info
23335 @cindex debug expression parser
23336 @item set debug parser
23337 Turns on or off the display of expression parser debugging output.
23338 Internally, this sets the @code{yydebug} variable in the expression
23339 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
23340 details. The default is off.
23341 @item show debug parser
23342 Show the current state of expression parser debugging.
23343 @cindex packets, reporting on stdout
23344 @cindex serial connections, debugging
23345 @cindex debug remote protocol
23346 @cindex remote protocol debugging
23347 @cindex display remote packets
23348 @item set debug remote
23349 Turns on or off display of reports on all packets sent back and forth across
23350 the serial line to the remote machine. The info is printed on the
23351 @value{GDBN} standard output stream. The default is off.
23352 @item show debug remote
23353 Displays the state of display of remote packets.
23354 @item set debug serial
23355 Turns on or off display of @value{GDBN} serial debugging info. The
23357 @item show debug serial
23358 Displays the current state of displaying @value{GDBN} serial debugging
23360 @item set debug solib-frv
23361 @cindex FR-V shared-library debugging
23362 Turns on or off debugging messages for FR-V shared-library code.
23363 @item show debug solib-frv
23364 Display the current state of FR-V shared-library code debugging
23366 @item set debug symbol-lookup
23367 @cindex symbol lookup
23368 Turns on or off display of debugging messages related to symbol lookup.
23369 The default is 0 (off).
23370 A value of 1 provides basic information.
23371 A value greater than 1 provides more verbose information.
23372 @item show debug symbol-lookup
23373 Show the current state of symbol lookup debugging messages.
23374 @item set debug symfile
23375 @cindex symbol file functions
23376 Turns on or off display of debugging messages related to symbol file functions.
23377 The default is off. @xref{Files}.
23378 @item show debug symfile
23379 Show the current state of symbol file debugging messages.
23380 @item set debug symtab-create
23381 @cindex symbol table creation
23382 Turns on or off display of debugging messages related to symbol table creation.
23383 The default is 0 (off).
23384 A value of 1 provides basic information.
23385 A value greater than 1 provides more verbose information.
23386 @item show debug symtab-create
23387 Show the current state of symbol table creation debugging.
23388 @item set debug target
23389 @cindex target debugging info
23390 Turns on or off display of @value{GDBN} target debugging info. This info
23391 includes what is going on at the target level of GDB, as it happens. The
23392 default is 0. Set it to 1 to track events, and to 2 to also track the
23393 value of large memory transfers.
23394 @item show debug target
23395 Displays the current state of displaying @value{GDBN} target debugging
23397 @item set debug timestamp
23398 @cindex timestampping debugging info
23399 Turns on or off display of timestamps with @value{GDBN} debugging info.
23400 When enabled, seconds and microseconds are displayed before each debugging
23402 @item show debug timestamp
23403 Displays the current state of displaying timestamps with @value{GDBN}
23405 @item set debug varobj
23406 @cindex variable object debugging info
23407 Turns on or off display of @value{GDBN} variable object debugging
23408 info. The default is off.
23409 @item show debug varobj
23410 Displays the current state of displaying @value{GDBN} variable object
23412 @item set debug xml
23413 @cindex XML parser debugging
23414 Turns on or off debugging messages for built-in XML parsers.
23415 @item show debug xml
23416 Displays the current state of XML debugging messages.
23419 @node Other Misc Settings
23420 @section Other Miscellaneous Settings
23421 @cindex miscellaneous settings
23424 @kindex set interactive-mode
23425 @item set interactive-mode
23426 If @code{on}, forces @value{GDBN} to assume that GDB was started
23427 in a terminal. In practice, this means that @value{GDBN} should wait
23428 for the user to answer queries generated by commands entered at
23429 the command prompt. If @code{off}, forces @value{GDBN} to operate
23430 in the opposite mode, and it uses the default answers to all queries.
23431 If @code{auto} (the default), @value{GDBN} tries to determine whether
23432 its standard input is a terminal, and works in interactive-mode if it
23433 is, non-interactively otherwise.
23435 In the vast majority of cases, the debugger should be able to guess
23436 correctly which mode should be used. But this setting can be useful
23437 in certain specific cases, such as running a MinGW @value{GDBN}
23438 inside a cygwin window.
23440 @kindex show interactive-mode
23441 @item show interactive-mode
23442 Displays whether the debugger is operating in interactive mode or not.
23445 @node Extending GDB
23446 @chapter Extending @value{GDBN}
23447 @cindex extending GDB
23449 @value{GDBN} provides several mechanisms for extension.
23450 @value{GDBN} also provides the ability to automatically load
23451 extensions when it reads a file for debugging. This allows the
23452 user to automatically customize @value{GDBN} for the program
23456 * Sequences:: Canned Sequences of @value{GDBN} Commands
23457 * Python:: Extending @value{GDBN} using Python
23458 * Guile:: Extending @value{GDBN} using Guile
23459 * Auto-loading extensions:: Automatically loading extensions
23460 * Multiple Extension Languages:: Working with multiple extension languages
23461 * Aliases:: Creating new spellings of existing commands
23464 To facilitate the use of extension languages, @value{GDBN} is capable
23465 of evaluating the contents of a file. When doing so, @value{GDBN}
23466 can recognize which extension language is being used by looking at
23467 the filename extension. Files with an unrecognized filename extension
23468 are always treated as a @value{GDBN} Command Files.
23469 @xref{Command Files,, Command files}.
23471 You can control how @value{GDBN} evaluates these files with the following
23475 @kindex set script-extension
23476 @kindex show script-extension
23477 @item set script-extension off
23478 All scripts are always evaluated as @value{GDBN} Command Files.
23480 @item set script-extension soft
23481 The debugger determines the scripting language based on filename
23482 extension. If this scripting language is supported, @value{GDBN}
23483 evaluates the script using that language. Otherwise, it evaluates
23484 the file as a @value{GDBN} Command File.
23486 @item set script-extension strict
23487 The debugger determines the scripting language based on filename
23488 extension, and evaluates the script using that language. If the
23489 language is not supported, then the evaluation fails.
23491 @item show script-extension
23492 Display the current value of the @code{script-extension} option.
23497 @section Canned Sequences of Commands
23499 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
23500 Command Lists}), @value{GDBN} provides two ways to store sequences of
23501 commands for execution as a unit: user-defined commands and command
23505 * Define:: How to define your own commands
23506 * Hooks:: Hooks for user-defined commands
23507 * Command Files:: How to write scripts of commands to be stored in a file
23508 * Output:: Commands for controlled output
23509 * Auto-loading sequences:: Controlling auto-loaded command files
23513 @subsection User-defined Commands
23515 @cindex user-defined command
23516 @cindex arguments, to user-defined commands
23517 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
23518 which you assign a new name as a command. This is done with the
23519 @code{define} command. User commands may accept up to 10 arguments
23520 separated by whitespace. Arguments are accessed within the user command
23521 via @code{$arg0@dots{}$arg9}. A trivial example:
23525 print $arg0 + $arg1 + $arg2
23530 To execute the command use:
23537 This defines the command @code{adder}, which prints the sum of
23538 its three arguments. Note the arguments are text substitutions, so they may
23539 reference variables, use complex expressions, or even perform inferior
23542 @cindex argument count in user-defined commands
23543 @cindex how many arguments (user-defined commands)
23544 In addition, @code{$argc} may be used to find out how many arguments have
23545 been passed. This expands to a number in the range 0@dots{}10.
23550 print $arg0 + $arg1
23553 print $arg0 + $arg1 + $arg2
23561 @item define @var{commandname}
23562 Define a command named @var{commandname}. If there is already a command
23563 by that name, you are asked to confirm that you want to redefine it.
23564 The argument @var{commandname} may be a bare command name consisting of letters,
23565 numbers, dashes, and underscores. It may also start with any predefined
23566 prefix command. For example, @samp{define target my-target} creates
23567 a user-defined @samp{target my-target} command.
23569 The definition of the command is made up of other @value{GDBN} command lines,
23570 which are given following the @code{define} command. The end of these
23571 commands is marked by a line containing @code{end}.
23574 @kindex end@r{ (user-defined commands)}
23575 @item document @var{commandname}
23576 Document the user-defined command @var{commandname}, so that it can be
23577 accessed by @code{help}. The command @var{commandname} must already be
23578 defined. This command reads lines of documentation just as @code{define}
23579 reads the lines of the command definition, ending with @code{end}.
23580 After the @code{document} command is finished, @code{help} on command
23581 @var{commandname} displays the documentation you have written.
23583 You may use the @code{document} command again to change the
23584 documentation of a command. Redefining the command with @code{define}
23585 does not change the documentation.
23587 @kindex dont-repeat
23588 @cindex don't repeat command
23590 Used inside a user-defined command, this tells @value{GDBN} that this
23591 command should not be repeated when the user hits @key{RET}
23592 (@pxref{Command Syntax, repeat last command}).
23594 @kindex help user-defined
23595 @item help user-defined
23596 List all user-defined commands and all python commands defined in class
23597 COMAND_USER. The first line of the documentation or docstring is
23602 @itemx show user @var{commandname}
23603 Display the @value{GDBN} commands used to define @var{commandname} (but
23604 not its documentation). If no @var{commandname} is given, display the
23605 definitions for all user-defined commands.
23606 This does not work for user-defined python commands.
23608 @cindex infinite recursion in user-defined commands
23609 @kindex show max-user-call-depth
23610 @kindex set max-user-call-depth
23611 @item show max-user-call-depth
23612 @itemx set max-user-call-depth
23613 The value of @code{max-user-call-depth} controls how many recursion
23614 levels are allowed in user-defined commands before @value{GDBN} suspects an
23615 infinite recursion and aborts the command.
23616 This does not apply to user-defined python commands.
23619 In addition to the above commands, user-defined commands frequently
23620 use control flow commands, described in @ref{Command Files}.
23622 When user-defined commands are executed, the
23623 commands of the definition are not printed. An error in any command
23624 stops execution of the user-defined command.
23626 If used interactively, commands that would ask for confirmation proceed
23627 without asking when used inside a user-defined command. Many @value{GDBN}
23628 commands that normally print messages to say what they are doing omit the
23629 messages when used in a user-defined command.
23632 @subsection User-defined Command Hooks
23633 @cindex command hooks
23634 @cindex hooks, for commands
23635 @cindex hooks, pre-command
23638 You may define @dfn{hooks}, which are a special kind of user-defined
23639 command. Whenever you run the command @samp{foo}, if the user-defined
23640 command @samp{hook-foo} exists, it is executed (with no arguments)
23641 before that command.
23643 @cindex hooks, post-command
23645 A hook may also be defined which is run after the command you executed.
23646 Whenever you run the command @samp{foo}, if the user-defined command
23647 @samp{hookpost-foo} exists, it is executed (with no arguments) after
23648 that command. Post-execution hooks may exist simultaneously with
23649 pre-execution hooks, for the same command.
23651 It is valid for a hook to call the command which it hooks. If this
23652 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
23654 @c It would be nice if hookpost could be passed a parameter indicating
23655 @c if the command it hooks executed properly or not. FIXME!
23657 @kindex stop@r{, a pseudo-command}
23658 In addition, a pseudo-command, @samp{stop} exists. Defining
23659 (@samp{hook-stop}) makes the associated commands execute every time
23660 execution stops in your program: before breakpoint commands are run,
23661 displays are printed, or the stack frame is printed.
23663 For example, to ignore @code{SIGALRM} signals while
23664 single-stepping, but treat them normally during normal execution,
23669 handle SIGALRM nopass
23673 handle SIGALRM pass
23676 define hook-continue
23677 handle SIGALRM pass
23681 As a further example, to hook at the beginning and end of the @code{echo}
23682 command, and to add extra text to the beginning and end of the message,
23690 define hookpost-echo
23694 (@value{GDBP}) echo Hello World
23695 <<<---Hello World--->>>
23700 You can define a hook for any single-word command in @value{GDBN}, but
23701 not for command aliases; you should define a hook for the basic command
23702 name, e.g.@: @code{backtrace} rather than @code{bt}.
23703 @c FIXME! So how does Joe User discover whether a command is an alias
23705 You can hook a multi-word command by adding @code{hook-} or
23706 @code{hookpost-} to the last word of the command, e.g.@:
23707 @samp{define target hook-remote} to add a hook to @samp{target remote}.
23709 If an error occurs during the execution of your hook, execution of
23710 @value{GDBN} commands stops and @value{GDBN} issues a prompt
23711 (before the command that you actually typed had a chance to run).
23713 If you try to define a hook which does not match any known command, you
23714 get a warning from the @code{define} command.
23716 @node Command Files
23717 @subsection Command Files
23719 @cindex command files
23720 @cindex scripting commands
23721 A command file for @value{GDBN} is a text file made of lines that are
23722 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
23723 also be included. An empty line in a command file does nothing; it
23724 does not mean to repeat the last command, as it would from the
23727 You can request the execution of a command file with the @code{source}
23728 command. Note that the @code{source} command is also used to evaluate
23729 scripts that are not Command Files. The exact behavior can be configured
23730 using the @code{script-extension} setting.
23731 @xref{Extending GDB,, Extending GDB}.
23735 @cindex execute commands from a file
23736 @item source [-s] [-v] @var{filename}
23737 Execute the command file @var{filename}.
23740 The lines in a command file are generally executed sequentially,
23741 unless the order of execution is changed by one of the
23742 @emph{flow-control commands} described below. The commands are not
23743 printed as they are executed. An error in any command terminates
23744 execution of the command file and control is returned to the console.
23746 @value{GDBN} first searches for @var{filename} in the current directory.
23747 If the file is not found there, and @var{filename} does not specify a
23748 directory, then @value{GDBN} also looks for the file on the source search path
23749 (specified with the @samp{directory} command);
23750 except that @file{$cdir} is not searched because the compilation directory
23751 is not relevant to scripts.
23753 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
23754 on the search path even if @var{filename} specifies a directory.
23755 The search is done by appending @var{filename} to each element of the
23756 search path. So, for example, if @var{filename} is @file{mylib/myscript}
23757 and the search path contains @file{/home/user} then @value{GDBN} will
23758 look for the script @file{/home/user/mylib/myscript}.
23759 The search is also done if @var{filename} is an absolute path.
23760 For example, if @var{filename} is @file{/tmp/myscript} and
23761 the search path contains @file{/home/user} then @value{GDBN} will
23762 look for the script @file{/home/user/tmp/myscript}.
23763 For DOS-like systems, if @var{filename} contains a drive specification,
23764 it is stripped before concatenation. For example, if @var{filename} is
23765 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
23766 will look for the script @file{c:/tmp/myscript}.
23768 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
23769 each command as it is executed. The option must be given before
23770 @var{filename}, and is interpreted as part of the filename anywhere else.
23772 Commands that would ask for confirmation if used interactively proceed
23773 without asking when used in a command file. Many @value{GDBN} commands that
23774 normally print messages to say what they are doing omit the messages
23775 when called from command files.
23777 @value{GDBN} also accepts command input from standard input. In this
23778 mode, normal output goes to standard output and error output goes to
23779 standard error. Errors in a command file supplied on standard input do
23780 not terminate execution of the command file---execution continues with
23784 gdb < cmds > log 2>&1
23787 (The syntax above will vary depending on the shell used.) This example
23788 will execute commands from the file @file{cmds}. All output and errors
23789 would be directed to @file{log}.
23791 Since commands stored on command files tend to be more general than
23792 commands typed interactively, they frequently need to deal with
23793 complicated situations, such as different or unexpected values of
23794 variables and symbols, changes in how the program being debugged is
23795 built, etc. @value{GDBN} provides a set of flow-control commands to
23796 deal with these complexities. Using these commands, you can write
23797 complex scripts that loop over data structures, execute commands
23798 conditionally, etc.
23805 This command allows to include in your script conditionally executed
23806 commands. The @code{if} command takes a single argument, which is an
23807 expression to evaluate. It is followed by a series of commands that
23808 are executed only if the expression is true (its value is nonzero).
23809 There can then optionally be an @code{else} line, followed by a series
23810 of commands that are only executed if the expression was false. The
23811 end of the list is marked by a line containing @code{end}.
23815 This command allows to write loops. Its syntax is similar to
23816 @code{if}: the command takes a single argument, which is an expression
23817 to evaluate, and must be followed by the commands to execute, one per
23818 line, terminated by an @code{end}. These commands are called the
23819 @dfn{body} of the loop. The commands in the body of @code{while} are
23820 executed repeatedly as long as the expression evaluates to true.
23824 This command exits the @code{while} loop in whose body it is included.
23825 Execution of the script continues after that @code{while}s @code{end}
23828 @kindex loop_continue
23829 @item loop_continue
23830 This command skips the execution of the rest of the body of commands
23831 in the @code{while} loop in whose body it is included. Execution
23832 branches to the beginning of the @code{while} loop, where it evaluates
23833 the controlling expression.
23835 @kindex end@r{ (if/else/while commands)}
23837 Terminate the block of commands that are the body of @code{if},
23838 @code{else}, or @code{while} flow-control commands.
23843 @subsection Commands for Controlled Output
23845 During the execution of a command file or a user-defined command, normal
23846 @value{GDBN} output is suppressed; the only output that appears is what is
23847 explicitly printed by the commands in the definition. This section
23848 describes three commands useful for generating exactly the output you
23853 @item echo @var{text}
23854 @c I do not consider backslash-space a standard C escape sequence
23855 @c because it is not in ANSI.
23856 Print @var{text}. Nonprinting characters can be included in
23857 @var{text} using C escape sequences, such as @samp{\n} to print a
23858 newline. @strong{No newline is printed unless you specify one.}
23859 In addition to the standard C escape sequences, a backslash followed
23860 by a space stands for a space. This is useful for displaying a
23861 string with spaces at the beginning or the end, since leading and
23862 trailing spaces are otherwise trimmed from all arguments.
23863 To print @samp{@w{ }and foo =@w{ }}, use the command
23864 @samp{echo \@w{ }and foo = \@w{ }}.
23866 A backslash at the end of @var{text} can be used, as in C, to continue
23867 the command onto subsequent lines. For example,
23870 echo This is some text\n\
23871 which is continued\n\
23872 onto several lines.\n
23875 produces the same output as
23878 echo This is some text\n
23879 echo which is continued\n
23880 echo onto several lines.\n
23884 @item output @var{expression}
23885 Print the value of @var{expression} and nothing but that value: no
23886 newlines, no @samp{$@var{nn} = }. The value is not entered in the
23887 value history either. @xref{Expressions, ,Expressions}, for more information
23890 @item output/@var{fmt} @var{expression}
23891 Print the value of @var{expression} in format @var{fmt}. You can use
23892 the same formats as for @code{print}. @xref{Output Formats,,Output
23893 Formats}, for more information.
23896 @item printf @var{template}, @var{expressions}@dots{}
23897 Print the values of one or more @var{expressions} under the control of
23898 the string @var{template}. To print several values, make
23899 @var{expressions} be a comma-separated list of individual expressions,
23900 which may be either numbers or pointers. Their values are printed as
23901 specified by @var{template}, exactly as a C program would do by
23902 executing the code below:
23905 printf (@var{template}, @var{expressions}@dots{});
23908 As in @code{C} @code{printf}, ordinary characters in @var{template}
23909 are printed verbatim, while @dfn{conversion specification} introduced
23910 by the @samp{%} character cause subsequent @var{expressions} to be
23911 evaluated, their values converted and formatted according to type and
23912 style information encoded in the conversion specifications, and then
23915 For example, you can print two values in hex like this:
23918 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
23921 @code{printf} supports all the standard @code{C} conversion
23922 specifications, including the flags and modifiers between the @samp{%}
23923 character and the conversion letter, with the following exceptions:
23927 The argument-ordering modifiers, such as @samp{2$}, are not supported.
23930 The modifier @samp{*} is not supported for specifying precision or
23934 The @samp{'} flag (for separation of digits into groups according to
23935 @code{LC_NUMERIC'}) is not supported.
23938 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
23942 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
23945 The conversion letters @samp{a} and @samp{A} are not supported.
23949 Note that the @samp{ll} type modifier is supported only if the
23950 underlying @code{C} implementation used to build @value{GDBN} supports
23951 the @code{long long int} type, and the @samp{L} type modifier is
23952 supported only if @code{long double} type is available.
23954 As in @code{C}, @code{printf} supports simple backslash-escape
23955 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
23956 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
23957 single character. Octal and hexadecimal escape sequences are not
23960 Additionally, @code{printf} supports conversion specifications for DFP
23961 (@dfn{Decimal Floating Point}) types using the following length modifiers
23962 together with a floating point specifier.
23967 @samp{H} for printing @code{Decimal32} types.
23970 @samp{D} for printing @code{Decimal64} types.
23973 @samp{DD} for printing @code{Decimal128} types.
23976 If the underlying @code{C} implementation used to build @value{GDBN} has
23977 support for the three length modifiers for DFP types, other modifiers
23978 such as width and precision will also be available for @value{GDBN} to use.
23980 In case there is no such @code{C} support, no additional modifiers will be
23981 available and the value will be printed in the standard way.
23983 Here's an example of printing DFP types using the above conversion letters:
23985 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
23989 @item eval @var{template}, @var{expressions}@dots{}
23990 Convert the values of one or more @var{expressions} under the control of
23991 the string @var{template} to a command line, and call it.
23995 @node Auto-loading sequences
23996 @subsection Controlling auto-loading native @value{GDBN} scripts
23997 @cindex native script auto-loading
23999 When a new object file is read (for example, due to the @code{file}
24000 command, or because the inferior has loaded a shared library),
24001 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
24002 @xref{Auto-loading extensions}.
24004 Auto-loading can be enabled or disabled,
24005 and the list of auto-loaded scripts can be printed.
24008 @anchor{set auto-load gdb-scripts}
24009 @kindex set auto-load gdb-scripts
24010 @item set auto-load gdb-scripts [on|off]
24011 Enable or disable the auto-loading of canned sequences of commands scripts.
24013 @anchor{show auto-load gdb-scripts}
24014 @kindex show auto-load gdb-scripts
24015 @item show auto-load gdb-scripts
24016 Show whether auto-loading of canned sequences of commands scripts is enabled or
24019 @anchor{info auto-load gdb-scripts}
24020 @kindex info auto-load gdb-scripts
24021 @cindex print list of auto-loaded canned sequences of commands scripts
24022 @item info auto-load gdb-scripts [@var{regexp}]
24023 Print the list of all canned sequences of commands scripts that @value{GDBN}
24027 If @var{regexp} is supplied only canned sequences of commands scripts with
24028 matching names are printed.
24030 @c Python docs live in a separate file.
24031 @include python.texi
24033 @c Guile docs live in a separate file.
24034 @include guile.texi
24036 @node Auto-loading extensions
24037 @section Auto-loading extensions
24038 @cindex auto-loading extensions
24040 @value{GDBN} provides two mechanisms for automatically loading extensions
24041 when a new object file is read (for example, due to the @code{file}
24042 command, or because the inferior has loaded a shared library):
24043 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
24044 section of modern file formats like ELF.
24047 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
24048 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
24049 * Which flavor to choose?::
24052 The auto-loading feature is useful for supplying application-specific
24053 debugging commands and features.
24055 Auto-loading can be enabled or disabled,
24056 and the list of auto-loaded scripts can be printed.
24057 See the @samp{auto-loading} section of each extension language
24058 for more information.
24059 For @value{GDBN} command files see @ref{Auto-loading sequences}.
24060 For Python files see @ref{Python Auto-loading}.
24062 Note that loading of this script file also requires accordingly configured
24063 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24065 @node objfile-gdbdotext file
24066 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
24067 @cindex @file{@var{objfile}-gdb.gdb}
24068 @cindex @file{@var{objfile}-gdb.py}
24069 @cindex @file{@var{objfile}-gdb.scm}
24071 When a new object file is read, @value{GDBN} looks for a file named
24072 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
24073 where @var{objfile} is the object file's name and
24074 where @var{ext} is the file extension for the extension language:
24077 @item @file{@var{objfile}-gdb.gdb}
24078 GDB's own command language
24079 @item @file{@var{objfile}-gdb.py}
24081 @item @file{@var{objfile}-gdb.scm}
24085 @var{script-name} is formed by ensuring that the file name of @var{objfile}
24086 is absolute, following all symlinks, and resolving @code{.} and @code{..}
24087 components, and appending the @file{-gdb.@var{ext}} suffix.
24088 If this file exists and is readable, @value{GDBN} will evaluate it as a
24089 script in the specified extension language.
24091 If this file does not exist, then @value{GDBN} will look for
24092 @var{script-name} file in all of the directories as specified below.
24094 Note that loading of these files requires an accordingly configured
24095 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24097 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
24098 scripts normally according to its @file{.exe} filename. But if no scripts are
24099 found @value{GDBN} also tries script filenames matching the object file without
24100 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
24101 is attempted on any platform. This makes the script filenames compatible
24102 between Unix and MS-Windows hosts.
24105 @anchor{set auto-load scripts-directory}
24106 @kindex set auto-load scripts-directory
24107 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
24108 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
24109 may be delimited by the host platform path separator in use
24110 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
24112 Each entry here needs to be covered also by the security setting
24113 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
24115 @anchor{with-auto-load-dir}
24116 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
24117 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
24118 configuration option @option{--with-auto-load-dir}.
24120 Any reference to @file{$debugdir} will get replaced by
24121 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
24122 reference to @file{$datadir} will get replaced by @var{data-directory} which is
24123 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
24124 @file{$datadir} must be placed as a directory component --- either alone or
24125 delimited by @file{/} or @file{\} directory separators, depending on the host
24128 The list of directories uses path separator (@samp{:} on GNU and Unix
24129 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
24130 to the @env{PATH} environment variable.
24132 @anchor{show auto-load scripts-directory}
24133 @kindex show auto-load scripts-directory
24134 @item show auto-load scripts-directory
24135 Show @value{GDBN} auto-loaded scripts location.
24137 @anchor{add-auto-load-scripts-directory}
24138 @kindex add-auto-load-scripts-directory
24139 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
24140 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
24141 Multiple entries may be delimited by the host platform path separator in use.
24144 @value{GDBN} does not track which files it has already auto-loaded this way.
24145 @value{GDBN} will load the associated script every time the corresponding
24146 @var{objfile} is opened.
24147 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
24148 is evaluated more than once.
24150 @node dotdebug_gdb_scripts section
24151 @subsection The @code{.debug_gdb_scripts} section
24152 @cindex @code{.debug_gdb_scripts} section
24154 For systems using file formats like ELF and COFF,
24155 when @value{GDBN} loads a new object file
24156 it will look for a special section named @code{.debug_gdb_scripts}.
24157 If this section exists, its contents is a list of null-terminated entries
24158 specifying scripts to load. Each entry begins with a non-null prefix byte that
24159 specifies the kind of entry, typically the extension language and whether the
24160 script is in a file or inlined in @code{.debug_gdb_scripts}.
24162 The following entries are supported:
24165 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
24166 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
24167 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
24168 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
24171 @subsubsection Script File Entries
24173 If the entry specifies a file, @value{GDBN} will look for the file first
24174 in the current directory and then along the source search path
24175 (@pxref{Source Path, ,Specifying Source Directories}),
24176 except that @file{$cdir} is not searched, since the compilation
24177 directory is not relevant to scripts.
24179 File entries can be placed in section @code{.debug_gdb_scripts} with,
24180 for example, this GCC macro for Python scripts.
24183 /* Note: The "MS" section flags are to remove duplicates. */
24184 #define DEFINE_GDB_PY_SCRIPT(script_name) \
24186 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
24187 .byte 1 /* Python */\n\
24188 .asciz \"" script_name "\"\n\
24194 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
24195 Then one can reference the macro in a header or source file like this:
24198 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
24201 The script name may include directories if desired.
24203 Note that loading of this script file also requires accordingly configured
24204 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24206 If the macro invocation is put in a header, any application or library
24207 using this header will get a reference to the specified script,
24208 and with the use of @code{"MS"} attributes on the section, the linker
24209 will remove duplicates.
24211 @subsubsection Script Text Entries
24213 Script text entries allow to put the executable script in the entry
24214 itself instead of loading it from a file.
24215 The first line of the entry, everything after the prefix byte and up to
24216 the first newline (@code{0xa}) character, is the script name, and must not
24217 contain any kind of space character, e.g., spaces or tabs.
24218 The rest of the entry, up to the trailing null byte, is the script to
24219 execute in the specified language. The name needs to be unique among
24220 all script names, as @value{GDBN} executes each script only once based
24223 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
24227 #include "symcat.h"
24228 #include "gdb/section-scripts.h"
24230 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
24231 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
24232 ".ascii \"gdb.inlined-script\\n\"\n"
24233 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
24234 ".ascii \" def __init__ (self):\\n\"\n"
24235 ".ascii \" super (test_cmd, self).__init__ ("
24236 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
24237 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
24238 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
24239 ".ascii \"test_cmd ()\\n\"\n"
24245 Loading of inlined scripts requires a properly configured
24246 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24247 The path to specify in @code{auto-load safe-path} is the path of the file
24248 containing the @code{.debug_gdb_scripts} section.
24250 @node Which flavor to choose?
24251 @subsection Which flavor to choose?
24253 Given the multiple ways of auto-loading extensions, it might not always
24254 be clear which one to choose. This section provides some guidance.
24257 Benefits of the @file{-gdb.@var{ext}} way:
24261 Can be used with file formats that don't support multiple sections.
24264 Ease of finding scripts for public libraries.
24266 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
24267 in the source search path.
24268 For publicly installed libraries, e.g., @file{libstdc++}, there typically
24269 isn't a source directory in which to find the script.
24272 Doesn't require source code additions.
24276 Benefits of the @code{.debug_gdb_scripts} way:
24280 Works with static linking.
24282 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
24283 trigger their loading. When an application is statically linked the only
24284 objfile available is the executable, and it is cumbersome to attach all the
24285 scripts from all the input libraries to the executable's
24286 @file{-gdb.@var{ext}} script.
24289 Works with classes that are entirely inlined.
24291 Some classes can be entirely inlined, and thus there may not be an associated
24292 shared library to attach a @file{-gdb.@var{ext}} script to.
24295 Scripts needn't be copied out of the source tree.
24297 In some circumstances, apps can be built out of large collections of internal
24298 libraries, and the build infrastructure necessary to install the
24299 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
24300 cumbersome. It may be easier to specify the scripts in the
24301 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
24302 top of the source tree to the source search path.
24305 @node Multiple Extension Languages
24306 @section Multiple Extension Languages
24308 The Guile and Python extension languages do not share any state,
24309 and generally do not interfere with each other.
24310 There are some things to be aware of, however.
24312 @subsection Python comes first
24314 Python was @value{GDBN}'s first extension language, and to avoid breaking
24315 existing behaviour Python comes first. This is generally solved by the
24316 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
24317 extension languages, and when it makes a call to an extension language,
24318 (say to pretty-print a value), it tries each in turn until an extension
24319 language indicates it has performed the request (e.g., has returned the
24320 pretty-printed form of a value).
24321 This extends to errors while performing such requests: If an error happens
24322 while, for example, trying to pretty-print an object then the error is
24323 reported and any following extension languages are not tried.
24326 @section Creating new spellings of existing commands
24327 @cindex aliases for commands
24329 It is often useful to define alternate spellings of existing commands.
24330 For example, if a new @value{GDBN} command defined in Python has
24331 a long name to type, it is handy to have an abbreviated version of it
24332 that involves less typing.
24334 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
24335 of the @samp{step} command even though it is otherwise an ambiguous
24336 abbreviation of other commands like @samp{set} and @samp{show}.
24338 Aliases are also used to provide shortened or more common versions
24339 of multi-word commands. For example, @value{GDBN} provides the
24340 @samp{tty} alias of the @samp{set inferior-tty} command.
24342 You can define a new alias with the @samp{alias} command.
24347 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
24351 @var{ALIAS} specifies the name of the new alias.
24352 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
24355 @var{COMMAND} specifies the name of an existing command
24356 that is being aliased.
24358 The @samp{-a} option specifies that the new alias is an abbreviation
24359 of the command. Abbreviations are not shown in command
24360 lists displayed by the @samp{help} command.
24362 The @samp{--} option specifies the end of options,
24363 and is useful when @var{ALIAS} begins with a dash.
24365 Here is a simple example showing how to make an abbreviation
24366 of a command so that there is less to type.
24367 Suppose you were tired of typing @samp{disas}, the current
24368 shortest unambiguous abbreviation of the @samp{disassemble} command
24369 and you wanted an even shorter version named @samp{di}.
24370 The following will accomplish this.
24373 (gdb) alias -a di = disas
24376 Note that aliases are different from user-defined commands.
24377 With a user-defined command, you also need to write documentation
24378 for it with the @samp{document} command.
24379 An alias automatically picks up the documentation of the existing command.
24381 Here is an example where we make @samp{elms} an abbreviation of
24382 @samp{elements} in the @samp{set print elements} command.
24383 This is to show that you can make an abbreviation of any part
24387 (gdb) alias -a set print elms = set print elements
24388 (gdb) alias -a show print elms = show print elements
24389 (gdb) set p elms 20
24391 Limit on string chars or array elements to print is 200.
24394 Note that if you are defining an alias of a @samp{set} command,
24395 and you want to have an alias for the corresponding @samp{show}
24396 command, then you need to define the latter separately.
24398 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
24399 @var{ALIAS}, just as they are normally.
24402 (gdb) alias -a set pr elms = set p ele
24405 Finally, here is an example showing the creation of a one word
24406 alias for a more complex command.
24407 This creates alias @samp{spe} of the command @samp{set print elements}.
24410 (gdb) alias spe = set print elements
24415 @chapter Command Interpreters
24416 @cindex command interpreters
24418 @value{GDBN} supports multiple command interpreters, and some command
24419 infrastructure to allow users or user interface writers to switch
24420 between interpreters or run commands in other interpreters.
24422 @value{GDBN} currently supports two command interpreters, the console
24423 interpreter (sometimes called the command-line interpreter or @sc{cli})
24424 and the machine interface interpreter (or @sc{gdb/mi}). This manual
24425 describes both of these interfaces in great detail.
24427 By default, @value{GDBN} will start with the console interpreter.
24428 However, the user may choose to start @value{GDBN} with another
24429 interpreter by specifying the @option{-i} or @option{--interpreter}
24430 startup options. Defined interpreters include:
24434 @cindex console interpreter
24435 The traditional console or command-line interpreter. This is the most often
24436 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
24437 @value{GDBN} will use this interpreter.
24440 @cindex mi interpreter
24441 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
24442 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
24443 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
24447 @cindex mi2 interpreter
24448 The current @sc{gdb/mi} interface.
24451 @cindex mi1 interpreter
24452 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
24456 @cindex invoke another interpreter
24457 The interpreter being used by @value{GDBN} may not be dynamically
24458 switched at runtime. Although possible, this could lead to a very
24459 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
24460 enters the command "interpreter-set console" in a console view,
24461 @value{GDBN} would switch to using the console interpreter, rendering
24462 the IDE inoperable!
24464 @kindex interpreter-exec
24465 Although you may only choose a single interpreter at startup, you may execute
24466 commands in any interpreter from the current interpreter using the appropriate
24467 command. If you are running the console interpreter, simply use the
24468 @code{interpreter-exec} command:
24471 interpreter-exec mi "-data-list-register-names"
24474 @sc{gdb/mi} has a similar command, although it is only available in versions of
24475 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
24478 @chapter @value{GDBN} Text User Interface
24480 @cindex Text User Interface
24483 * TUI Overview:: TUI overview
24484 * TUI Keys:: TUI key bindings
24485 * TUI Single Key Mode:: TUI single key mode
24486 * TUI Commands:: TUI-specific commands
24487 * TUI Configuration:: TUI configuration variables
24490 The @value{GDBN} Text User Interface (TUI) is a terminal
24491 interface which uses the @code{curses} library to show the source
24492 file, the assembly output, the program registers and @value{GDBN}
24493 commands in separate text windows. The TUI mode is supported only
24494 on platforms where a suitable version of the @code{curses} library
24497 The TUI mode is enabled by default when you invoke @value{GDBN} as
24498 @samp{@value{GDBP} -tui}.
24499 You can also switch in and out of TUI mode while @value{GDBN} runs by
24500 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
24501 @xref{TUI Keys, ,TUI Key Bindings}.
24504 @section TUI Overview
24506 In TUI mode, @value{GDBN} can display several text windows:
24510 This window is the @value{GDBN} command window with the @value{GDBN}
24511 prompt and the @value{GDBN} output. The @value{GDBN} input is still
24512 managed using readline.
24515 The source window shows the source file of the program. The current
24516 line and active breakpoints are displayed in this window.
24519 The assembly window shows the disassembly output of the program.
24522 This window shows the processor registers. Registers are highlighted
24523 when their values change.
24526 The source and assembly windows show the current program position
24527 by highlighting the current line and marking it with a @samp{>} marker.
24528 Breakpoints are indicated with two markers. The first marker
24529 indicates the breakpoint type:
24533 Breakpoint which was hit at least once.
24536 Breakpoint which was never hit.
24539 Hardware breakpoint which was hit at least once.
24542 Hardware breakpoint which was never hit.
24545 The second marker indicates whether the breakpoint is enabled or not:
24549 Breakpoint is enabled.
24552 Breakpoint is disabled.
24555 The source, assembly and register windows are updated when the current
24556 thread changes, when the frame changes, or when the program counter
24559 These windows are not all visible at the same time. The command
24560 window is always visible. The others can be arranged in several
24571 source and assembly,
24574 source and registers, or
24577 assembly and registers.
24580 A status line above the command window shows the following information:
24584 Indicates the current @value{GDBN} target.
24585 (@pxref{Targets, ,Specifying a Debugging Target}).
24588 Gives the current process or thread number.
24589 When no process is being debugged, this field is set to @code{No process}.
24592 Gives the current function name for the selected frame.
24593 The name is demangled if demangling is turned on (@pxref{Print Settings}).
24594 When there is no symbol corresponding to the current program counter,
24595 the string @code{??} is displayed.
24598 Indicates the current line number for the selected frame.
24599 When the current line number is not known, the string @code{??} is displayed.
24602 Indicates the current program counter address.
24606 @section TUI Key Bindings
24607 @cindex TUI key bindings
24609 The TUI installs several key bindings in the readline keymaps
24610 @ifset SYSTEM_READLINE
24611 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
24613 @ifclear SYSTEM_READLINE
24614 (@pxref{Command Line Editing}).
24616 The following key bindings are installed for both TUI mode and the
24617 @value{GDBN} standard mode.
24626 Enter or leave the TUI mode. When leaving the TUI mode,
24627 the curses window management stops and @value{GDBN} operates using
24628 its standard mode, writing on the terminal directly. When reentering
24629 the TUI mode, control is given back to the curses windows.
24630 The screen is then refreshed.
24634 Use a TUI layout with only one window. The layout will
24635 either be @samp{source} or @samp{assembly}. When the TUI mode
24636 is not active, it will switch to the TUI mode.
24638 Think of this key binding as the Emacs @kbd{C-x 1} binding.
24642 Use a TUI layout with at least two windows. When the current
24643 layout already has two windows, the next layout with two windows is used.
24644 When a new layout is chosen, one window will always be common to the
24645 previous layout and the new one.
24647 Think of it as the Emacs @kbd{C-x 2} binding.
24651 Change the active window. The TUI associates several key bindings
24652 (like scrolling and arrow keys) with the active window. This command
24653 gives the focus to the next TUI window.
24655 Think of it as the Emacs @kbd{C-x o} binding.
24659 Switch in and out of the TUI SingleKey mode that binds single
24660 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
24663 The following key bindings only work in the TUI mode:
24668 Scroll the active window one page up.
24672 Scroll the active window one page down.
24676 Scroll the active window one line up.
24680 Scroll the active window one line down.
24684 Scroll the active window one column left.
24688 Scroll the active window one column right.
24692 Refresh the screen.
24695 Because the arrow keys scroll the active window in the TUI mode, they
24696 are not available for their normal use by readline unless the command
24697 window has the focus. When another window is active, you must use
24698 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
24699 and @kbd{C-f} to control the command window.
24701 @node TUI Single Key Mode
24702 @section TUI Single Key Mode
24703 @cindex TUI single key mode
24705 The TUI also provides a @dfn{SingleKey} mode, which binds several
24706 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
24707 switch into this mode, where the following key bindings are used:
24710 @kindex c @r{(SingleKey TUI key)}
24714 @kindex d @r{(SingleKey TUI key)}
24718 @kindex f @r{(SingleKey TUI key)}
24722 @kindex n @r{(SingleKey TUI key)}
24726 @kindex q @r{(SingleKey TUI key)}
24728 exit the SingleKey mode.
24730 @kindex r @r{(SingleKey TUI key)}
24734 @kindex s @r{(SingleKey TUI key)}
24738 @kindex u @r{(SingleKey TUI key)}
24742 @kindex v @r{(SingleKey TUI key)}
24746 @kindex w @r{(SingleKey TUI key)}
24751 Other keys temporarily switch to the @value{GDBN} command prompt.
24752 The key that was pressed is inserted in the editing buffer so that
24753 it is possible to type most @value{GDBN} commands without interaction
24754 with the TUI SingleKey mode. Once the command is entered the TUI
24755 SingleKey mode is restored. The only way to permanently leave
24756 this mode is by typing @kbd{q} or @kbd{C-x s}.
24760 @section TUI-specific Commands
24761 @cindex TUI commands
24763 The TUI has specific commands to control the text windows.
24764 These commands are always available, even when @value{GDBN} is not in
24765 the TUI mode. When @value{GDBN} is in the standard mode, most
24766 of these commands will automatically switch to the TUI mode.
24768 Note that if @value{GDBN}'s @code{stdout} is not connected to a
24769 terminal, or @value{GDBN} has been started with the machine interface
24770 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
24771 these commands will fail with an error, because it would not be
24772 possible or desirable to enable curses window management.
24777 List and give the size of all displayed windows.
24781 Display the next layout.
24784 Display the previous layout.
24787 Display the source window only.
24790 Display the assembly window only.
24793 Display the source and assembly window.
24796 Display the register window together with the source or assembly window.
24800 Make the next window active for scrolling.
24803 Make the previous window active for scrolling.
24806 Make the source window active for scrolling.
24809 Make the assembly window active for scrolling.
24812 Make the register window active for scrolling.
24815 Make the command window active for scrolling.
24819 Refresh the screen. This is similar to typing @kbd{C-L}.
24821 @item tui reg float
24823 Show the floating point registers in the register window.
24825 @item tui reg general
24826 Show the general registers in the register window.
24829 Show the next register group. The list of register groups as well as
24830 their order is target specific. The predefined register groups are the
24831 following: @code{general}, @code{float}, @code{system}, @code{vector},
24832 @code{all}, @code{save}, @code{restore}.
24834 @item tui reg system
24835 Show the system registers in the register window.
24839 Update the source window and the current execution point.
24841 @item winheight @var{name} +@var{count}
24842 @itemx winheight @var{name} -@var{count}
24844 Change the height of the window @var{name} by @var{count}
24845 lines. Positive counts increase the height, while negative counts
24846 decrease it. The @var{name} parameter can be one of @code{src} (the
24847 source window), @code{cmd} (the command window), @code{asm} (the
24848 disassembly window), or @code{regs} (the register display window).
24850 @item tabset @var{nchars}
24852 Set the width of tab stops to be @var{nchars} characters. This
24853 setting affects the display of TAB characters in the source and
24857 @node TUI Configuration
24858 @section TUI Configuration Variables
24859 @cindex TUI configuration variables
24861 Several configuration variables control the appearance of TUI windows.
24864 @item set tui border-kind @var{kind}
24865 @kindex set tui border-kind
24866 Select the border appearance for the source, assembly and register windows.
24867 The possible values are the following:
24870 Use a space character to draw the border.
24873 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
24876 Use the Alternate Character Set to draw the border. The border is
24877 drawn using character line graphics if the terminal supports them.
24880 @item set tui border-mode @var{mode}
24881 @kindex set tui border-mode
24882 @itemx set tui active-border-mode @var{mode}
24883 @kindex set tui active-border-mode
24884 Select the display attributes for the borders of the inactive windows
24885 or the active window. The @var{mode} can be one of the following:
24888 Use normal attributes to display the border.
24894 Use reverse video mode.
24897 Use half bright mode.
24899 @item half-standout
24900 Use half bright and standout mode.
24903 Use extra bright or bold mode.
24905 @item bold-standout
24906 Use extra bright or bold and standout mode.
24911 @chapter Using @value{GDBN} under @sc{gnu} Emacs
24914 @cindex @sc{gnu} Emacs
24915 A special interface allows you to use @sc{gnu} Emacs to view (and
24916 edit) the source files for the program you are debugging with
24919 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
24920 executable file you want to debug as an argument. This command starts
24921 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
24922 created Emacs buffer.
24923 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
24925 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
24930 All ``terminal'' input and output goes through an Emacs buffer, called
24933 This applies both to @value{GDBN} commands and their output, and to the input
24934 and output done by the program you are debugging.
24936 This is useful because it means that you can copy the text of previous
24937 commands and input them again; you can even use parts of the output
24940 All the facilities of Emacs' Shell mode are available for interacting
24941 with your program. In particular, you can send signals the usual
24942 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
24946 @value{GDBN} displays source code through Emacs.
24948 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
24949 source file for that frame and puts an arrow (@samp{=>}) at the
24950 left margin of the current line. Emacs uses a separate buffer for
24951 source display, and splits the screen to show both your @value{GDBN} session
24954 Explicit @value{GDBN} @code{list} or search commands still produce output as
24955 usual, but you probably have no reason to use them from Emacs.
24958 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
24959 a graphical mode, enabled by default, which provides further buffers
24960 that can control the execution and describe the state of your program.
24961 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
24963 If you specify an absolute file name when prompted for the @kbd{M-x
24964 gdb} argument, then Emacs sets your current working directory to where
24965 your program resides. If you only specify the file name, then Emacs
24966 sets your current working directory to the directory associated
24967 with the previous buffer. In this case, @value{GDBN} may find your
24968 program by searching your environment's @code{PATH} variable, but on
24969 some operating systems it might not find the source. So, although the
24970 @value{GDBN} input and output session proceeds normally, the auxiliary
24971 buffer does not display the current source and line of execution.
24973 The initial working directory of @value{GDBN} is printed on the top
24974 line of the GUD buffer and this serves as a default for the commands
24975 that specify files for @value{GDBN} to operate on. @xref{Files,
24976 ,Commands to Specify Files}.
24978 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
24979 need to call @value{GDBN} by a different name (for example, if you
24980 keep several configurations around, with different names) you can
24981 customize the Emacs variable @code{gud-gdb-command-name} to run the
24984 In the GUD buffer, you can use these special Emacs commands in
24985 addition to the standard Shell mode commands:
24989 Describe the features of Emacs' GUD Mode.
24992 Execute to another source line, like the @value{GDBN} @code{step} command; also
24993 update the display window to show the current file and location.
24996 Execute to next source line in this function, skipping all function
24997 calls, like the @value{GDBN} @code{next} command. Then update the display window
24998 to show the current file and location.
25001 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
25002 display window accordingly.
25005 Execute until exit from the selected stack frame, like the @value{GDBN}
25006 @code{finish} command.
25009 Continue execution of your program, like the @value{GDBN} @code{continue}
25013 Go up the number of frames indicated by the numeric argument
25014 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
25015 like the @value{GDBN} @code{up} command.
25018 Go down the number of frames indicated by the numeric argument, like the
25019 @value{GDBN} @code{down} command.
25022 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
25023 tells @value{GDBN} to set a breakpoint on the source line point is on.
25025 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
25026 separate frame which shows a backtrace when the GUD buffer is current.
25027 Move point to any frame in the stack and type @key{RET} to make it
25028 become the current frame and display the associated source in the
25029 source buffer. Alternatively, click @kbd{Mouse-2} to make the
25030 selected frame become the current one. In graphical mode, the
25031 speedbar displays watch expressions.
25033 If you accidentally delete the source-display buffer, an easy way to get
25034 it back is to type the command @code{f} in the @value{GDBN} buffer, to
25035 request a frame display; when you run under Emacs, this recreates
25036 the source buffer if necessary to show you the context of the current
25039 The source files displayed in Emacs are in ordinary Emacs buffers
25040 which are visiting the source files in the usual way. You can edit
25041 the files with these buffers if you wish; but keep in mind that @value{GDBN}
25042 communicates with Emacs in terms of line numbers. If you add or
25043 delete lines from the text, the line numbers that @value{GDBN} knows cease
25044 to correspond properly with the code.
25046 A more detailed description of Emacs' interaction with @value{GDBN} is
25047 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
25051 @chapter The @sc{gdb/mi} Interface
25053 @unnumberedsec Function and Purpose
25055 @cindex @sc{gdb/mi}, its purpose
25056 @sc{gdb/mi} is a line based machine oriented text interface to
25057 @value{GDBN} and is activated by specifying using the
25058 @option{--interpreter} command line option (@pxref{Mode Options}). It
25059 is specifically intended to support the development of systems which
25060 use the debugger as just one small component of a larger system.
25062 This chapter is a specification of the @sc{gdb/mi} interface. It is written
25063 in the form of a reference manual.
25065 Note that @sc{gdb/mi} is still under construction, so some of the
25066 features described below are incomplete and subject to change
25067 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
25069 @unnumberedsec Notation and Terminology
25071 @cindex notational conventions, for @sc{gdb/mi}
25072 This chapter uses the following notation:
25076 @code{|} separates two alternatives.
25079 @code{[ @var{something} ]} indicates that @var{something} is optional:
25080 it may or may not be given.
25083 @code{( @var{group} )*} means that @var{group} inside the parentheses
25084 may repeat zero or more times.
25087 @code{( @var{group} )+} means that @var{group} inside the parentheses
25088 may repeat one or more times.
25091 @code{"@var{string}"} means a literal @var{string}.
25095 @heading Dependencies
25099 * GDB/MI General Design::
25100 * GDB/MI Command Syntax::
25101 * GDB/MI Compatibility with CLI::
25102 * GDB/MI Development and Front Ends::
25103 * GDB/MI Output Records::
25104 * GDB/MI Simple Examples::
25105 * GDB/MI Command Description Format::
25106 * GDB/MI Breakpoint Commands::
25107 * GDB/MI Catchpoint Commands::
25108 * GDB/MI Program Context::
25109 * GDB/MI Thread Commands::
25110 * GDB/MI Ada Tasking Commands::
25111 * GDB/MI Program Execution::
25112 * GDB/MI Stack Manipulation::
25113 * GDB/MI Variable Objects::
25114 * GDB/MI Data Manipulation::
25115 * GDB/MI Tracepoint Commands::
25116 * GDB/MI Symbol Query::
25117 * GDB/MI File Commands::
25119 * GDB/MI Kod Commands::
25120 * GDB/MI Memory Overlay Commands::
25121 * GDB/MI Signal Handling Commands::
25123 * GDB/MI Target Manipulation::
25124 * GDB/MI File Transfer Commands::
25125 * GDB/MI Ada Exceptions Commands::
25126 * GDB/MI Support Commands::
25127 * GDB/MI Miscellaneous Commands::
25130 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25131 @node GDB/MI General Design
25132 @section @sc{gdb/mi} General Design
25133 @cindex GDB/MI General Design
25135 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
25136 parts---commands sent to @value{GDBN}, responses to those commands
25137 and notifications. Each command results in exactly one response,
25138 indicating either successful completion of the command, or an error.
25139 For the commands that do not resume the target, the response contains the
25140 requested information. For the commands that resume the target, the
25141 response only indicates whether the target was successfully resumed.
25142 Notifications is the mechanism for reporting changes in the state of the
25143 target, or in @value{GDBN} state, that cannot conveniently be associated with
25144 a command and reported as part of that command response.
25146 The important examples of notifications are:
25150 Exec notifications. These are used to report changes in
25151 target state---when a target is resumed, or stopped. It would not
25152 be feasible to include this information in response of resuming
25153 commands, because one resume commands can result in multiple events in
25154 different threads. Also, quite some time may pass before any event
25155 happens in the target, while a frontend needs to know whether the resuming
25156 command itself was successfully executed.
25159 Console output, and status notifications. Console output
25160 notifications are used to report output of CLI commands, as well as
25161 diagnostics for other commands. Status notifications are used to
25162 report the progress of a long-running operation. Naturally, including
25163 this information in command response would mean no output is produced
25164 until the command is finished, which is undesirable.
25167 General notifications. Commands may have various side effects on
25168 the @value{GDBN} or target state beyond their official purpose. For example,
25169 a command may change the selected thread. Although such changes can
25170 be included in command response, using notification allows for more
25171 orthogonal frontend design.
25175 There's no guarantee that whenever an MI command reports an error,
25176 @value{GDBN} or the target are in any specific state, and especially,
25177 the state is not reverted to the state before the MI command was
25178 processed. Therefore, whenever an MI command results in an error,
25179 we recommend that the frontend refreshes all the information shown in
25180 the user interface.
25184 * Context management::
25185 * Asynchronous and non-stop modes::
25189 @node Context management
25190 @subsection Context management
25192 @subsubsection Threads and Frames
25194 In most cases when @value{GDBN} accesses the target, this access is
25195 done in context of a specific thread and frame (@pxref{Frames}).
25196 Often, even when accessing global data, the target requires that a thread
25197 be specified. The CLI interface maintains the selected thread and frame,
25198 and supplies them to target on each command. This is convenient,
25199 because a command line user would not want to specify that information
25200 explicitly on each command, and because user interacts with
25201 @value{GDBN} via a single terminal, so no confusion is possible as
25202 to what thread and frame are the current ones.
25204 In the case of MI, the concept of selected thread and frame is less
25205 useful. First, a frontend can easily remember this information
25206 itself. Second, a graphical frontend can have more than one window,
25207 each one used for debugging a different thread, and the frontend might
25208 want to access additional threads for internal purposes. This
25209 increases the risk that by relying on implicitly selected thread, the
25210 frontend may be operating on a wrong one. Therefore, each MI command
25211 should explicitly specify which thread and frame to operate on. To
25212 make it possible, each MI command accepts the @samp{--thread} and
25213 @samp{--frame} options, the value to each is @value{GDBN} identifier
25214 for thread and frame to operate on.
25216 Usually, each top-level window in a frontend allows the user to select
25217 a thread and a frame, and remembers the user selection for further
25218 operations. However, in some cases @value{GDBN} may suggest that the
25219 current thread be changed. For example, when stopping on a breakpoint
25220 it is reasonable to switch to the thread where breakpoint is hit. For
25221 another example, if the user issues the CLI @samp{thread} command via
25222 the frontend, it is desirable to change the frontend's selected thread to the
25223 one specified by user. @value{GDBN} communicates the suggestion to
25224 change current thread using the @samp{=thread-selected} notification.
25225 No such notification is available for the selected frame at the moment.
25227 Note that historically, MI shares the selected thread with CLI, so
25228 frontends used the @code{-thread-select} to execute commands in the
25229 right context. However, getting this to work right is cumbersome. The
25230 simplest way is for frontend to emit @code{-thread-select} command
25231 before every command. This doubles the number of commands that need
25232 to be sent. The alternative approach is to suppress @code{-thread-select}
25233 if the selected thread in @value{GDBN} is supposed to be identical to the
25234 thread the frontend wants to operate on. However, getting this
25235 optimization right can be tricky. In particular, if the frontend
25236 sends several commands to @value{GDBN}, and one of the commands changes the
25237 selected thread, then the behaviour of subsequent commands will
25238 change. So, a frontend should either wait for response from such
25239 problematic commands, or explicitly add @code{-thread-select} for
25240 all subsequent commands. No frontend is known to do this exactly
25241 right, so it is suggested to just always pass the @samp{--thread} and
25242 @samp{--frame} options.
25244 @subsubsection Language
25246 The execution of several commands depends on which language is selected.
25247 By default, the current language (@pxref{show language}) is used.
25248 But for commands known to be language-sensitive, it is recommended
25249 to use the @samp{--language} option. This option takes one argument,
25250 which is the name of the language to use while executing the command.
25254 -data-evaluate-expression --language c "sizeof (void*)"
25259 The valid language names are the same names accepted by the
25260 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
25261 @samp{local} or @samp{unknown}.
25263 @node Asynchronous and non-stop modes
25264 @subsection Asynchronous command execution and non-stop mode
25266 On some targets, @value{GDBN} is capable of processing MI commands
25267 even while the target is running. This is called @dfn{asynchronous
25268 command execution} (@pxref{Background Execution}). The frontend may
25269 specify a preferrence for asynchronous execution using the
25270 @code{-gdb-set mi-async 1} command, which should be emitted before
25271 either running the executable or attaching to the target. After the
25272 frontend has started the executable or attached to the target, it can
25273 find if asynchronous execution is enabled using the
25274 @code{-list-target-features} command.
25277 @item -gdb-set mi-async on
25278 @item -gdb-set mi-async off
25279 Set whether MI is in asynchronous mode.
25281 When @code{off}, which is the default, MI execution commands (e.g.,
25282 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
25283 for the program to stop before processing further commands.
25285 When @code{on}, MI execution commands are background execution
25286 commands (e.g., @code{-exec-continue} becomes the equivalent of the
25287 @code{c&} CLI command), and so @value{GDBN} is capable of processing
25288 MI commands even while the target is running.
25290 @item -gdb-show mi-async
25291 Show whether MI asynchronous mode is enabled.
25294 Note: In @value{GDBN} version 7.7 and earlier, this option was called
25295 @code{target-async} instead of @code{mi-async}, and it had the effect
25296 of both putting MI in asynchronous mode and making CLI background
25297 commands possible. CLI background commands are now always possible
25298 ``out of the box'' if the target supports them. The old spelling is
25299 kept as a deprecated alias for backwards compatibility.
25301 Even if @value{GDBN} can accept a command while target is running,
25302 many commands that access the target do not work when the target is
25303 running. Therefore, asynchronous command execution is most useful
25304 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
25305 it is possible to examine the state of one thread, while other threads
25308 When a given thread is running, MI commands that try to access the
25309 target in the context of that thread may not work, or may work only on
25310 some targets. In particular, commands that try to operate on thread's
25311 stack will not work, on any target. Commands that read memory, or
25312 modify breakpoints, may work or not work, depending on the target. Note
25313 that even commands that operate on global state, such as @code{print},
25314 @code{set}, and breakpoint commands, still access the target in the
25315 context of a specific thread, so frontend should try to find a
25316 stopped thread and perform the operation on that thread (using the
25317 @samp{--thread} option).
25319 Which commands will work in the context of a running thread is
25320 highly target dependent. However, the two commands
25321 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
25322 to find the state of a thread, will always work.
25324 @node Thread groups
25325 @subsection Thread groups
25326 @value{GDBN} may be used to debug several processes at the same time.
25327 On some platfroms, @value{GDBN} may support debugging of several
25328 hardware systems, each one having several cores with several different
25329 processes running on each core. This section describes the MI
25330 mechanism to support such debugging scenarios.
25332 The key observation is that regardless of the structure of the
25333 target, MI can have a global list of threads, because most commands that
25334 accept the @samp{--thread} option do not need to know what process that
25335 thread belongs to. Therefore, it is not necessary to introduce
25336 neither additional @samp{--process} option, nor an notion of the
25337 current process in the MI interface. The only strictly new feature
25338 that is required is the ability to find how the threads are grouped
25341 To allow the user to discover such grouping, and to support arbitrary
25342 hierarchy of machines/cores/processes, MI introduces the concept of a
25343 @dfn{thread group}. Thread group is a collection of threads and other
25344 thread groups. A thread group always has a string identifier, a type,
25345 and may have additional attributes specific to the type. A new
25346 command, @code{-list-thread-groups}, returns the list of top-level
25347 thread groups, which correspond to processes that @value{GDBN} is
25348 debugging at the moment. By passing an identifier of a thread group
25349 to the @code{-list-thread-groups} command, it is possible to obtain
25350 the members of specific thread group.
25352 To allow the user to easily discover processes, and other objects, he
25353 wishes to debug, a concept of @dfn{available thread group} is
25354 introduced. Available thread group is an thread group that
25355 @value{GDBN} is not debugging, but that can be attached to, using the
25356 @code{-target-attach} command. The list of available top-level thread
25357 groups can be obtained using @samp{-list-thread-groups --available}.
25358 In general, the content of a thread group may be only retrieved only
25359 after attaching to that thread group.
25361 Thread groups are related to inferiors (@pxref{Inferiors and
25362 Programs}). Each inferior corresponds to a thread group of a special
25363 type @samp{process}, and some additional operations are permitted on
25364 such thread groups.
25366 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25367 @node GDB/MI Command Syntax
25368 @section @sc{gdb/mi} Command Syntax
25371 * GDB/MI Input Syntax::
25372 * GDB/MI Output Syntax::
25375 @node GDB/MI Input Syntax
25376 @subsection @sc{gdb/mi} Input Syntax
25378 @cindex input syntax for @sc{gdb/mi}
25379 @cindex @sc{gdb/mi}, input syntax
25381 @item @var{command} @expansion{}
25382 @code{@var{cli-command} | @var{mi-command}}
25384 @item @var{cli-command} @expansion{}
25385 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
25386 @var{cli-command} is any existing @value{GDBN} CLI command.
25388 @item @var{mi-command} @expansion{}
25389 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
25390 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
25392 @item @var{token} @expansion{}
25393 "any sequence of digits"
25395 @item @var{option} @expansion{}
25396 @code{"-" @var{parameter} [ " " @var{parameter} ]}
25398 @item @var{parameter} @expansion{}
25399 @code{@var{non-blank-sequence} | @var{c-string}}
25401 @item @var{operation} @expansion{}
25402 @emph{any of the operations described in this chapter}
25404 @item @var{non-blank-sequence} @expansion{}
25405 @emph{anything, provided it doesn't contain special characters such as
25406 "-", @var{nl}, """ and of course " "}
25408 @item @var{c-string} @expansion{}
25409 @code{""" @var{seven-bit-iso-c-string-content} """}
25411 @item @var{nl} @expansion{}
25420 The CLI commands are still handled by the @sc{mi} interpreter; their
25421 output is described below.
25424 The @code{@var{token}}, when present, is passed back when the command
25428 Some @sc{mi} commands accept optional arguments as part of the parameter
25429 list. Each option is identified by a leading @samp{-} (dash) and may be
25430 followed by an optional argument parameter. Options occur first in the
25431 parameter list and can be delimited from normal parameters using
25432 @samp{--} (this is useful when some parameters begin with a dash).
25439 We want easy access to the existing CLI syntax (for debugging).
25442 We want it to be easy to spot a @sc{mi} operation.
25445 @node GDB/MI Output Syntax
25446 @subsection @sc{gdb/mi} Output Syntax
25448 @cindex output syntax of @sc{gdb/mi}
25449 @cindex @sc{gdb/mi}, output syntax
25450 The output from @sc{gdb/mi} consists of zero or more out-of-band records
25451 followed, optionally, by a single result record. This result record
25452 is for the most recent command. The sequence of output records is
25453 terminated by @samp{(gdb)}.
25455 If an input command was prefixed with a @code{@var{token}} then the
25456 corresponding output for that command will also be prefixed by that same
25460 @item @var{output} @expansion{}
25461 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
25463 @item @var{result-record} @expansion{}
25464 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
25466 @item @var{out-of-band-record} @expansion{}
25467 @code{@var{async-record} | @var{stream-record}}
25469 @item @var{async-record} @expansion{}
25470 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
25472 @item @var{exec-async-output} @expansion{}
25473 @code{[ @var{token} ] "*" @var{async-output nl}}
25475 @item @var{status-async-output} @expansion{}
25476 @code{[ @var{token} ] "+" @var{async-output nl}}
25478 @item @var{notify-async-output} @expansion{}
25479 @code{[ @var{token} ] "=" @var{async-output nl}}
25481 @item @var{async-output} @expansion{}
25482 @code{@var{async-class} ( "," @var{result} )*}
25484 @item @var{result-class} @expansion{}
25485 @code{"done" | "running" | "connected" | "error" | "exit"}
25487 @item @var{async-class} @expansion{}
25488 @code{"stopped" | @var{others}} (where @var{others} will be added
25489 depending on the needs---this is still in development).
25491 @item @var{result} @expansion{}
25492 @code{ @var{variable} "=" @var{value}}
25494 @item @var{variable} @expansion{}
25495 @code{ @var{string} }
25497 @item @var{value} @expansion{}
25498 @code{ @var{const} | @var{tuple} | @var{list} }
25500 @item @var{const} @expansion{}
25501 @code{@var{c-string}}
25503 @item @var{tuple} @expansion{}
25504 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
25506 @item @var{list} @expansion{}
25507 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
25508 @var{result} ( "," @var{result} )* "]" }
25510 @item @var{stream-record} @expansion{}
25511 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
25513 @item @var{console-stream-output} @expansion{}
25514 @code{"~" @var{c-string nl}}
25516 @item @var{target-stream-output} @expansion{}
25517 @code{"@@" @var{c-string nl}}
25519 @item @var{log-stream-output} @expansion{}
25520 @code{"&" @var{c-string nl}}
25522 @item @var{nl} @expansion{}
25525 @item @var{token} @expansion{}
25526 @emph{any sequence of digits}.
25534 All output sequences end in a single line containing a period.
25537 The @code{@var{token}} is from the corresponding request. Note that
25538 for all async output, while the token is allowed by the grammar and
25539 may be output by future versions of @value{GDBN} for select async
25540 output messages, it is generally omitted. Frontends should treat
25541 all async output as reporting general changes in the state of the
25542 target and there should be no need to associate async output to any
25546 @cindex status output in @sc{gdb/mi}
25547 @var{status-async-output} contains on-going status information about the
25548 progress of a slow operation. It can be discarded. All status output is
25549 prefixed by @samp{+}.
25552 @cindex async output in @sc{gdb/mi}
25553 @var{exec-async-output} contains asynchronous state change on the target
25554 (stopped, started, disappeared). All async output is prefixed by
25558 @cindex notify output in @sc{gdb/mi}
25559 @var{notify-async-output} contains supplementary information that the
25560 client should handle (e.g., a new breakpoint information). All notify
25561 output is prefixed by @samp{=}.
25564 @cindex console output in @sc{gdb/mi}
25565 @var{console-stream-output} is output that should be displayed as is in the
25566 console. It is the textual response to a CLI command. All the console
25567 output is prefixed by @samp{~}.
25570 @cindex target output in @sc{gdb/mi}
25571 @var{target-stream-output} is the output produced by the target program.
25572 All the target output is prefixed by @samp{@@}.
25575 @cindex log output in @sc{gdb/mi}
25576 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
25577 instance messages that should be displayed as part of an error log. All
25578 the log output is prefixed by @samp{&}.
25581 @cindex list output in @sc{gdb/mi}
25582 New @sc{gdb/mi} commands should only output @var{lists} containing
25588 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
25589 details about the various output records.
25591 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25592 @node GDB/MI Compatibility with CLI
25593 @section @sc{gdb/mi} Compatibility with CLI
25595 @cindex compatibility, @sc{gdb/mi} and CLI
25596 @cindex @sc{gdb/mi}, compatibility with CLI
25598 For the developers convenience CLI commands can be entered directly,
25599 but there may be some unexpected behaviour. For example, commands
25600 that query the user will behave as if the user replied yes, breakpoint
25601 command lists are not executed and some CLI commands, such as
25602 @code{if}, @code{when} and @code{define}, prompt for further input with
25603 @samp{>}, which is not valid MI output.
25605 This feature may be removed at some stage in the future and it is
25606 recommended that front ends use the @code{-interpreter-exec} command
25607 (@pxref{-interpreter-exec}).
25609 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25610 @node GDB/MI Development and Front Ends
25611 @section @sc{gdb/mi} Development and Front Ends
25612 @cindex @sc{gdb/mi} development
25614 The application which takes the MI output and presents the state of the
25615 program being debugged to the user is called a @dfn{front end}.
25617 Although @sc{gdb/mi} is still incomplete, it is currently being used
25618 by a variety of front ends to @value{GDBN}. This makes it difficult
25619 to introduce new functionality without breaking existing usage. This
25620 section tries to minimize the problems by describing how the protocol
25623 Some changes in MI need not break a carefully designed front end, and
25624 for these the MI version will remain unchanged. The following is a
25625 list of changes that may occur within one level, so front ends should
25626 parse MI output in a way that can handle them:
25630 New MI commands may be added.
25633 New fields may be added to the output of any MI command.
25636 The range of values for fields with specified values, e.g.,
25637 @code{in_scope} (@pxref{-var-update}) may be extended.
25639 @c The format of field's content e.g type prefix, may change so parse it
25640 @c at your own risk. Yes, in general?
25642 @c The order of fields may change? Shouldn't really matter but it might
25643 @c resolve inconsistencies.
25646 If the changes are likely to break front ends, the MI version level
25647 will be increased by one. This will allow the front end to parse the
25648 output according to the MI version. Apart from mi0, new versions of
25649 @value{GDBN} will not support old versions of MI and it will be the
25650 responsibility of the front end to work with the new one.
25652 @c Starting with mi3, add a new command -mi-version that prints the MI
25655 The best way to avoid unexpected changes in MI that might break your front
25656 end is to make your project known to @value{GDBN} developers and
25657 follow development on @email{gdb@@sourceware.org} and
25658 @email{gdb-patches@@sourceware.org}.
25659 @cindex mailing lists
25661 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25662 @node GDB/MI Output Records
25663 @section @sc{gdb/mi} Output Records
25666 * GDB/MI Result Records::
25667 * GDB/MI Stream Records::
25668 * GDB/MI Async Records::
25669 * GDB/MI Breakpoint Information::
25670 * GDB/MI Frame Information::
25671 * GDB/MI Thread Information::
25672 * GDB/MI Ada Exception Information::
25675 @node GDB/MI Result Records
25676 @subsection @sc{gdb/mi} Result Records
25678 @cindex result records in @sc{gdb/mi}
25679 @cindex @sc{gdb/mi}, result records
25680 In addition to a number of out-of-band notifications, the response to a
25681 @sc{gdb/mi} command includes one of the following result indications:
25685 @item "^done" [ "," @var{results} ]
25686 The synchronous operation was successful, @code{@var{results}} are the return
25691 This result record is equivalent to @samp{^done}. Historically, it
25692 was output instead of @samp{^done} if the command has resumed the
25693 target. This behaviour is maintained for backward compatibility, but
25694 all frontends should treat @samp{^done} and @samp{^running}
25695 identically and rely on the @samp{*running} output record to determine
25696 which threads are resumed.
25700 @value{GDBN} has connected to a remote target.
25702 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
25704 The operation failed. The @code{msg=@var{c-string}} variable contains
25705 the corresponding error message.
25707 If present, the @code{code=@var{c-string}} variable provides an error
25708 code on which consumers can rely on to detect the corresponding
25709 error condition. At present, only one error code is defined:
25712 @item "undefined-command"
25713 Indicates that the command causing the error does not exist.
25718 @value{GDBN} has terminated.
25722 @node GDB/MI Stream Records
25723 @subsection @sc{gdb/mi} Stream Records
25725 @cindex @sc{gdb/mi}, stream records
25726 @cindex stream records in @sc{gdb/mi}
25727 @value{GDBN} internally maintains a number of output streams: the console, the
25728 target, and the log. The output intended for each of these streams is
25729 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
25731 Each stream record begins with a unique @dfn{prefix character} which
25732 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
25733 Syntax}). In addition to the prefix, each stream record contains a
25734 @code{@var{string-output}}. This is either raw text (with an implicit new
25735 line) or a quoted C string (which does not contain an implicit newline).
25738 @item "~" @var{string-output}
25739 The console output stream contains text that should be displayed in the
25740 CLI console window. It contains the textual responses to CLI commands.
25742 @item "@@" @var{string-output}
25743 The target output stream contains any textual output from the running
25744 target. This is only present when GDB's event loop is truly
25745 asynchronous, which is currently only the case for remote targets.
25747 @item "&" @var{string-output}
25748 The log stream contains debugging messages being produced by @value{GDBN}'s
25752 @node GDB/MI Async Records
25753 @subsection @sc{gdb/mi} Async Records
25755 @cindex async records in @sc{gdb/mi}
25756 @cindex @sc{gdb/mi}, async records
25757 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
25758 additional changes that have occurred. Those changes can either be a
25759 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
25760 target activity (e.g., target stopped).
25762 The following is the list of possible async records:
25766 @item *running,thread-id="@var{thread}"
25767 The target is now running. The @var{thread} field tells which
25768 specific thread is now running, and can be @samp{all} if all threads
25769 are running. The frontend should assume that no interaction with a
25770 running thread is possible after this notification is produced.
25771 The frontend should not assume that this notification is output
25772 only once for any command. @value{GDBN} may emit this notification
25773 several times, either for different threads, because it cannot resume
25774 all threads together, or even for a single thread, if the thread must
25775 be stepped though some code before letting it run freely.
25777 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
25778 The target has stopped. The @var{reason} field can have one of the
25782 @item breakpoint-hit
25783 A breakpoint was reached.
25784 @item watchpoint-trigger
25785 A watchpoint was triggered.
25786 @item read-watchpoint-trigger
25787 A read watchpoint was triggered.
25788 @item access-watchpoint-trigger
25789 An access watchpoint was triggered.
25790 @item function-finished
25791 An -exec-finish or similar CLI command was accomplished.
25792 @item location-reached
25793 An -exec-until or similar CLI command was accomplished.
25794 @item watchpoint-scope
25795 A watchpoint has gone out of scope.
25796 @item end-stepping-range
25797 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
25798 similar CLI command was accomplished.
25799 @item exited-signalled
25800 The inferior exited because of a signal.
25802 The inferior exited.
25803 @item exited-normally
25804 The inferior exited normally.
25805 @item signal-received
25806 A signal was received by the inferior.
25808 The inferior has stopped due to a library being loaded or unloaded.
25809 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
25810 set or when a @code{catch load} or @code{catch unload} catchpoint is
25811 in use (@pxref{Set Catchpoints}).
25813 The inferior has forked. This is reported when @code{catch fork}
25814 (@pxref{Set Catchpoints}) has been used.
25816 The inferior has vforked. This is reported in when @code{catch vfork}
25817 (@pxref{Set Catchpoints}) has been used.
25818 @item syscall-entry
25819 The inferior entered a system call. This is reported when @code{catch
25820 syscall} (@pxref{Set Catchpoints}) has been used.
25821 @item syscall-return
25822 The inferior returned from a system call. This is reported when
25823 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
25825 The inferior called @code{exec}. This is reported when @code{catch exec}
25826 (@pxref{Set Catchpoints}) has been used.
25829 The @var{id} field identifies the thread that directly caused the stop
25830 -- for example by hitting a breakpoint. Depending on whether all-stop
25831 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
25832 stop all threads, or only the thread that directly triggered the stop.
25833 If all threads are stopped, the @var{stopped} field will have the
25834 value of @code{"all"}. Otherwise, the value of the @var{stopped}
25835 field will be a list of thread identifiers. Presently, this list will
25836 always include a single thread, but frontend should be prepared to see
25837 several threads in the list. The @var{core} field reports the
25838 processor core on which the stop event has happened. This field may be absent
25839 if such information is not available.
25841 @item =thread-group-added,id="@var{id}"
25842 @itemx =thread-group-removed,id="@var{id}"
25843 A thread group was either added or removed. The @var{id} field
25844 contains the @value{GDBN} identifier of the thread group. When a thread
25845 group is added, it generally might not be associated with a running
25846 process. When a thread group is removed, its id becomes invalid and
25847 cannot be used in any way.
25849 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
25850 A thread group became associated with a running program,
25851 either because the program was just started or the thread group
25852 was attached to a program. The @var{id} field contains the
25853 @value{GDBN} identifier of the thread group. The @var{pid} field
25854 contains process identifier, specific to the operating system.
25856 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
25857 A thread group is no longer associated with a running program,
25858 either because the program has exited, or because it was detached
25859 from. The @var{id} field contains the @value{GDBN} identifier of the
25860 thread group. The @var{code} field is the exit code of the inferior; it exists
25861 only when the inferior exited with some code.
25863 @item =thread-created,id="@var{id}",group-id="@var{gid}"
25864 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
25865 A thread either was created, or has exited. The @var{id} field
25866 contains the @value{GDBN} identifier of the thread. The @var{gid}
25867 field identifies the thread group this thread belongs to.
25869 @item =thread-selected,id="@var{id}"
25870 Informs that the selected thread was changed as result of the last
25871 command. This notification is not emitted as result of @code{-thread-select}
25872 command but is emitted whenever an MI command that is not documented
25873 to change the selected thread actually changes it. In particular,
25874 invoking, directly or indirectly (via user-defined command), the CLI
25875 @code{thread} command, will generate this notification.
25877 We suggest that in response to this notification, front ends
25878 highlight the selected thread and cause subsequent commands to apply to
25881 @item =library-loaded,...
25882 Reports that a new library file was loaded by the program. This
25883 notification has 4 fields---@var{id}, @var{target-name},
25884 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
25885 opaque identifier of the library. For remote debugging case,
25886 @var{target-name} and @var{host-name} fields give the name of the
25887 library file on the target, and on the host respectively. For native
25888 debugging, both those fields have the same value. The
25889 @var{symbols-loaded} field is emitted only for backward compatibility
25890 and should not be relied on to convey any useful information. The
25891 @var{thread-group} field, if present, specifies the id of the thread
25892 group in whose context the library was loaded. If the field is
25893 absent, it means the library was loaded in the context of all present
25896 @item =library-unloaded,...
25897 Reports that a library was unloaded by the program. This notification
25898 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
25899 the same meaning as for the @code{=library-loaded} notification.
25900 The @var{thread-group} field, if present, specifies the id of the
25901 thread group in whose context the library was unloaded. If the field is
25902 absent, it means the library was unloaded in the context of all present
25905 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
25906 @itemx =traceframe-changed,end
25907 Reports that the trace frame was changed and its new number is
25908 @var{tfnum}. The number of the tracepoint associated with this trace
25909 frame is @var{tpnum}.
25911 @item =tsv-created,name=@var{name},initial=@var{initial}
25912 Reports that the new trace state variable @var{name} is created with
25913 initial value @var{initial}.
25915 @item =tsv-deleted,name=@var{name}
25916 @itemx =tsv-deleted
25917 Reports that the trace state variable @var{name} is deleted or all
25918 trace state variables are deleted.
25920 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
25921 Reports that the trace state variable @var{name} is modified with
25922 the initial value @var{initial}. The current value @var{current} of
25923 trace state variable is optional and is reported if the current
25924 value of trace state variable is known.
25926 @item =breakpoint-created,bkpt=@{...@}
25927 @itemx =breakpoint-modified,bkpt=@{...@}
25928 @itemx =breakpoint-deleted,id=@var{number}
25929 Reports that a breakpoint was created, modified, or deleted,
25930 respectively. Only user-visible breakpoints are reported to the MI
25933 The @var{bkpt} argument is of the same form as returned by the various
25934 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
25935 @var{number} is the ordinal number of the breakpoint.
25937 Note that if a breakpoint is emitted in the result record of a
25938 command, then it will not also be emitted in an async record.
25940 @item =record-started,thread-group="@var{id}"
25941 @itemx =record-stopped,thread-group="@var{id}"
25942 Execution log recording was either started or stopped on an
25943 inferior. The @var{id} is the @value{GDBN} identifier of the thread
25944 group corresponding to the affected inferior.
25946 @item =cmd-param-changed,param=@var{param},value=@var{value}
25947 Reports that a parameter of the command @code{set @var{param}} is
25948 changed to @var{value}. In the multi-word @code{set} command,
25949 the @var{param} is the whole parameter list to @code{set} command.
25950 For example, In command @code{set check type on}, @var{param}
25951 is @code{check type} and @var{value} is @code{on}.
25953 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
25954 Reports that bytes from @var{addr} to @var{data} + @var{len} were
25955 written in an inferior. The @var{id} is the identifier of the
25956 thread group corresponding to the affected inferior. The optional
25957 @code{type="code"} part is reported if the memory written to holds
25961 @node GDB/MI Breakpoint Information
25962 @subsection @sc{gdb/mi} Breakpoint Information
25964 When @value{GDBN} reports information about a breakpoint, a
25965 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
25970 The breakpoint number. For a breakpoint that represents one location
25971 of a multi-location breakpoint, this will be a dotted pair, like
25975 The type of the breakpoint. For ordinary breakpoints this will be
25976 @samp{breakpoint}, but many values are possible.
25979 If the type of the breakpoint is @samp{catchpoint}, then this
25980 indicates the exact type of catchpoint.
25983 This is the breakpoint disposition---either @samp{del}, meaning that
25984 the breakpoint will be deleted at the next stop, or @samp{keep},
25985 meaning that the breakpoint will not be deleted.
25988 This indicates whether the breakpoint is enabled, in which case the
25989 value is @samp{y}, or disabled, in which case the value is @samp{n}.
25990 Note that this is not the same as the field @code{enable}.
25993 The address of the breakpoint. This may be a hexidecimal number,
25994 giving the address; or the string @samp{<PENDING>}, for a pending
25995 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
25996 multiple locations. This field will not be present if no address can
25997 be determined. For example, a watchpoint does not have an address.
26000 If known, the function in which the breakpoint appears.
26001 If not known, this field is not present.
26004 The name of the source file which contains this function, if known.
26005 If not known, this field is not present.
26008 The full file name of the source file which contains this function, if
26009 known. If not known, this field is not present.
26012 The line number at which this breakpoint appears, if known.
26013 If not known, this field is not present.
26016 If the source file is not known, this field may be provided. If
26017 provided, this holds the address of the breakpoint, possibly followed
26021 If this breakpoint is pending, this field is present and holds the
26022 text used to set the breakpoint, as entered by the user.
26025 Where this breakpoint's condition is evaluated, either @samp{host} or
26029 If this is a thread-specific breakpoint, then this identifies the
26030 thread in which the breakpoint can trigger.
26033 If this breakpoint is restricted to a particular Ada task, then this
26034 field will hold the task identifier.
26037 If the breakpoint is conditional, this is the condition expression.
26040 The ignore count of the breakpoint.
26043 The enable count of the breakpoint.
26045 @item traceframe-usage
26048 @item static-tracepoint-marker-string-id
26049 For a static tracepoint, the name of the static tracepoint marker.
26052 For a masked watchpoint, this is the mask.
26055 A tracepoint's pass count.
26057 @item original-location
26058 The location of the breakpoint as originally specified by the user.
26059 This field is optional.
26062 The number of times the breakpoint has been hit.
26065 This field is only given for tracepoints. This is either @samp{y},
26066 meaning that the tracepoint is installed, or @samp{n}, meaning that it
26070 Some extra data, the exact contents of which are type-dependent.
26074 For example, here is what the output of @code{-break-insert}
26075 (@pxref{GDB/MI Breakpoint Commands}) might be:
26078 -> -break-insert main
26079 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26080 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26081 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
26086 @node GDB/MI Frame Information
26087 @subsection @sc{gdb/mi} Frame Information
26089 Response from many MI commands includes an information about stack
26090 frame. This information is a tuple that may have the following
26095 The level of the stack frame. The innermost frame has the level of
26096 zero. This field is always present.
26099 The name of the function corresponding to the frame. This field may
26100 be absent if @value{GDBN} is unable to determine the function name.
26103 The code address for the frame. This field is always present.
26106 The name of the source files that correspond to the frame's code
26107 address. This field may be absent.
26110 The source line corresponding to the frames' code address. This field
26114 The name of the binary file (either executable or shared library) the
26115 corresponds to the frame's code address. This field may be absent.
26119 @node GDB/MI Thread Information
26120 @subsection @sc{gdb/mi} Thread Information
26122 Whenever @value{GDBN} has to report an information about a thread, it
26123 uses a tuple with the following fields:
26127 The numeric id assigned to the thread by @value{GDBN}. This field is
26131 Target-specific string identifying the thread. This field is always present.
26134 Additional information about the thread provided by the target.
26135 It is supposed to be human-readable and not interpreted by the
26136 frontend. This field is optional.
26139 Either @samp{stopped} or @samp{running}, depending on whether the
26140 thread is presently running. This field is always present.
26143 The value of this field is an integer number of the processor core the
26144 thread was last seen on. This field is optional.
26147 @node GDB/MI Ada Exception Information
26148 @subsection @sc{gdb/mi} Ada Exception Information
26150 Whenever a @code{*stopped} record is emitted because the program
26151 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
26152 @value{GDBN} provides the name of the exception that was raised via
26153 the @code{exception-name} field.
26155 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26156 @node GDB/MI Simple Examples
26157 @section Simple Examples of @sc{gdb/mi} Interaction
26158 @cindex @sc{gdb/mi}, simple examples
26160 This subsection presents several simple examples of interaction using
26161 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
26162 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
26163 the output received from @sc{gdb/mi}.
26165 Note the line breaks shown in the examples are here only for
26166 readability, they don't appear in the real output.
26168 @subheading Setting a Breakpoint
26170 Setting a breakpoint generates synchronous output which contains detailed
26171 information of the breakpoint.
26174 -> -break-insert main
26175 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26176 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26177 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
26182 @subheading Program Execution
26184 Program execution generates asynchronous records and MI gives the
26185 reason that execution stopped.
26191 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
26192 frame=@{addr="0x08048564",func="main",
26193 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
26194 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
26199 <- *stopped,reason="exited-normally"
26203 @subheading Quitting @value{GDBN}
26205 Quitting @value{GDBN} just prints the result class @samp{^exit}.
26213 Please note that @samp{^exit} is printed immediately, but it might
26214 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
26215 performs necessary cleanups, including killing programs being debugged
26216 or disconnecting from debug hardware, so the frontend should wait till
26217 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
26218 fails to exit in reasonable time.
26220 @subheading A Bad Command
26222 Here's what happens if you pass a non-existent command:
26226 <- ^error,msg="Undefined MI command: rubbish"
26231 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26232 @node GDB/MI Command Description Format
26233 @section @sc{gdb/mi} Command Description Format
26235 The remaining sections describe blocks of commands. Each block of
26236 commands is laid out in a fashion similar to this section.
26238 @subheading Motivation
26240 The motivation for this collection of commands.
26242 @subheading Introduction
26244 A brief introduction to this collection of commands as a whole.
26246 @subheading Commands
26248 For each command in the block, the following is described:
26250 @subsubheading Synopsis
26253 -command @var{args}@dots{}
26256 @subsubheading Result
26258 @subsubheading @value{GDBN} Command
26260 The corresponding @value{GDBN} CLI command(s), if any.
26262 @subsubheading Example
26264 Example(s) formatted for readability. Some of the described commands have
26265 not been implemented yet and these are labeled N.A.@: (not available).
26268 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26269 @node GDB/MI Breakpoint Commands
26270 @section @sc{gdb/mi} Breakpoint Commands
26272 @cindex breakpoint commands for @sc{gdb/mi}
26273 @cindex @sc{gdb/mi}, breakpoint commands
26274 This section documents @sc{gdb/mi} commands for manipulating
26277 @subheading The @code{-break-after} Command
26278 @findex -break-after
26280 @subsubheading Synopsis
26283 -break-after @var{number} @var{count}
26286 The breakpoint number @var{number} is not in effect until it has been
26287 hit @var{count} times. To see how this is reflected in the output of
26288 the @samp{-break-list} command, see the description of the
26289 @samp{-break-list} command below.
26291 @subsubheading @value{GDBN} Command
26293 The corresponding @value{GDBN} command is @samp{ignore}.
26295 @subsubheading Example
26300 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26301 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26302 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
26310 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26311 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26312 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26313 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26314 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26315 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26316 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26317 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26318 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26319 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
26324 @subheading The @code{-break-catch} Command
26325 @findex -break-catch
26328 @subheading The @code{-break-commands} Command
26329 @findex -break-commands
26331 @subsubheading Synopsis
26334 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
26337 Specifies the CLI commands that should be executed when breakpoint
26338 @var{number} is hit. The parameters @var{command1} to @var{commandN}
26339 are the commands. If no command is specified, any previously-set
26340 commands are cleared. @xref{Break Commands}. Typical use of this
26341 functionality is tracing a program, that is, printing of values of
26342 some variables whenever breakpoint is hit and then continuing.
26344 @subsubheading @value{GDBN} Command
26346 The corresponding @value{GDBN} command is @samp{commands}.
26348 @subsubheading Example
26353 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26354 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26355 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
26358 -break-commands 1 "print v" "continue"
26363 @subheading The @code{-break-condition} Command
26364 @findex -break-condition
26366 @subsubheading Synopsis
26369 -break-condition @var{number} @var{expr}
26372 Breakpoint @var{number} will stop the program only if the condition in
26373 @var{expr} is true. The condition becomes part of the
26374 @samp{-break-list} output (see the description of the @samp{-break-list}
26377 @subsubheading @value{GDBN} Command
26379 The corresponding @value{GDBN} command is @samp{condition}.
26381 @subsubheading Example
26385 -break-condition 1 1
26389 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26390 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26391 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26392 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26393 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26394 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26395 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26396 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26397 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26398 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
26402 @subheading The @code{-break-delete} Command
26403 @findex -break-delete
26405 @subsubheading Synopsis
26408 -break-delete ( @var{breakpoint} )+
26411 Delete the breakpoint(s) whose number(s) are specified in the argument
26412 list. This is obviously reflected in the breakpoint list.
26414 @subsubheading @value{GDBN} Command
26416 The corresponding @value{GDBN} command is @samp{delete}.
26418 @subsubheading Example
26426 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26427 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26428 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26429 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26430 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26431 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26432 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26437 @subheading The @code{-break-disable} Command
26438 @findex -break-disable
26440 @subsubheading Synopsis
26443 -break-disable ( @var{breakpoint} )+
26446 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
26447 break list is now set to @samp{n} for the named @var{breakpoint}(s).
26449 @subsubheading @value{GDBN} Command
26451 The corresponding @value{GDBN} command is @samp{disable}.
26453 @subsubheading Example
26461 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26462 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26463 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26464 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26465 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26466 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26467 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26468 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
26469 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26470 line="5",thread-groups=["i1"],times="0"@}]@}
26474 @subheading The @code{-break-enable} Command
26475 @findex -break-enable
26477 @subsubheading Synopsis
26480 -break-enable ( @var{breakpoint} )+
26483 Enable (previously disabled) @var{breakpoint}(s).
26485 @subsubheading @value{GDBN} Command
26487 The corresponding @value{GDBN} command is @samp{enable}.
26489 @subsubheading Example
26497 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26498 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26499 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26500 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26501 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26502 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26503 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26504 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26505 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26506 line="5",thread-groups=["i1"],times="0"@}]@}
26510 @subheading The @code{-break-info} Command
26511 @findex -break-info
26513 @subsubheading Synopsis
26516 -break-info @var{breakpoint}
26520 Get information about a single breakpoint.
26522 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
26523 Information}, for details on the format of each breakpoint in the
26526 @subsubheading @value{GDBN} Command
26528 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
26530 @subsubheading Example
26533 @subheading The @code{-break-insert} Command
26534 @findex -break-insert
26536 @subsubheading Synopsis
26539 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
26540 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26541 [ -p @var{thread-id} ] [ @var{location} ]
26545 If specified, @var{location}, can be one of:
26552 @item filename:linenum
26553 @item filename:function
26557 The possible optional parameters of this command are:
26561 Insert a temporary breakpoint.
26563 Insert a hardware breakpoint.
26565 If @var{location} cannot be parsed (for example if it
26566 refers to unknown files or functions), create a pending
26567 breakpoint. Without this flag, @value{GDBN} will report
26568 an error, and won't create a breakpoint, if @var{location}
26571 Create a disabled breakpoint.
26573 Create a tracepoint. @xref{Tracepoints}. When this parameter
26574 is used together with @samp{-h}, a fast tracepoint is created.
26575 @item -c @var{condition}
26576 Make the breakpoint conditional on @var{condition}.
26577 @item -i @var{ignore-count}
26578 Initialize the @var{ignore-count}.
26579 @item -p @var{thread-id}
26580 Restrict the breakpoint to the specified @var{thread-id}.
26583 @subsubheading Result
26585 @xref{GDB/MI Breakpoint Information}, for details on the format of the
26586 resulting breakpoint.
26588 Note: this format is open to change.
26589 @c An out-of-band breakpoint instead of part of the result?
26591 @subsubheading @value{GDBN} Command
26593 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
26594 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
26596 @subsubheading Example
26601 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
26602 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
26605 -break-insert -t foo
26606 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
26607 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
26611 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26612 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26613 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26614 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26615 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26616 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26617 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26618 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26619 addr="0x0001072c", func="main",file="recursive2.c",
26620 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
26622 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
26623 addr="0x00010774",func="foo",file="recursive2.c",
26624 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
26627 @c -break-insert -r foo.*
26628 @c ~int foo(int, int);
26629 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
26630 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
26635 @subheading The @code{-dprintf-insert} Command
26636 @findex -dprintf-insert
26638 @subsubheading Synopsis
26641 -dprintf-insert [ -t ] [ -f ] [ -d ]
26642 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26643 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
26648 If specified, @var{location}, can be one of:
26651 @item @var{function}
26654 @c @item @var{linenum}
26655 @item @var{filename}:@var{linenum}
26656 @item @var{filename}:function
26657 @item *@var{address}
26660 The possible optional parameters of this command are:
26664 Insert a temporary breakpoint.
26666 If @var{location} cannot be parsed (for example, if it
26667 refers to unknown files or functions), create a pending
26668 breakpoint. Without this flag, @value{GDBN} will report
26669 an error, and won't create a breakpoint, if @var{location}
26672 Create a disabled breakpoint.
26673 @item -c @var{condition}
26674 Make the breakpoint conditional on @var{condition}.
26675 @item -i @var{ignore-count}
26676 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
26677 to @var{ignore-count}.
26678 @item -p @var{thread-id}
26679 Restrict the breakpoint to the specified @var{thread-id}.
26682 @subsubheading Result
26684 @xref{GDB/MI Breakpoint Information}, for details on the format of the
26685 resulting breakpoint.
26687 @c An out-of-band breakpoint instead of part of the result?
26689 @subsubheading @value{GDBN} Command
26691 The corresponding @value{GDBN} command is @samp{dprintf}.
26693 @subsubheading Example
26697 4-dprintf-insert foo "At foo entry\n"
26698 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
26699 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
26700 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
26701 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
26702 original-location="foo"@}
26704 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
26705 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
26706 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
26707 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
26708 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
26709 original-location="mi-dprintf.c:26"@}
26713 @subheading The @code{-break-list} Command
26714 @findex -break-list
26716 @subsubheading Synopsis
26722 Displays the list of inserted breakpoints, showing the following fields:
26726 number of the breakpoint
26728 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
26730 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
26733 is the breakpoint enabled or no: @samp{y} or @samp{n}
26735 memory location at which the breakpoint is set
26737 logical location of the breakpoint, expressed by function name, file
26739 @item Thread-groups
26740 list of thread groups to which this breakpoint applies
26742 number of times the breakpoint has been hit
26745 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
26746 @code{body} field is an empty list.
26748 @subsubheading @value{GDBN} Command
26750 The corresponding @value{GDBN} command is @samp{info break}.
26752 @subsubheading Example
26757 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26758 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26759 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26760 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26761 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26762 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26763 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26764 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26765 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
26767 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26768 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
26769 line="13",thread-groups=["i1"],times="0"@}]@}
26773 Here's an example of the result when there are no breakpoints:
26778 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26779 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26780 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26781 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26782 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26783 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26784 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26789 @subheading The @code{-break-passcount} Command
26790 @findex -break-passcount
26792 @subsubheading Synopsis
26795 -break-passcount @var{tracepoint-number} @var{passcount}
26798 Set the passcount for tracepoint @var{tracepoint-number} to
26799 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
26800 is not a tracepoint, error is emitted. This corresponds to CLI
26801 command @samp{passcount}.
26803 @subheading The @code{-break-watch} Command
26804 @findex -break-watch
26806 @subsubheading Synopsis
26809 -break-watch [ -a | -r ]
26812 Create a watchpoint. With the @samp{-a} option it will create an
26813 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
26814 read from or on a write to the memory location. With the @samp{-r}
26815 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
26816 trigger only when the memory location is accessed for reading. Without
26817 either of the options, the watchpoint created is a regular watchpoint,
26818 i.e., it will trigger when the memory location is accessed for writing.
26819 @xref{Set Watchpoints, , Setting Watchpoints}.
26821 Note that @samp{-break-list} will report a single list of watchpoints and
26822 breakpoints inserted.
26824 @subsubheading @value{GDBN} Command
26826 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
26829 @subsubheading Example
26831 Setting a watchpoint on a variable in the @code{main} function:
26836 ^done,wpt=@{number="2",exp="x"@}
26841 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
26842 value=@{old="-268439212",new="55"@},
26843 frame=@{func="main",args=[],file="recursive2.c",
26844 fullname="/home/foo/bar/recursive2.c",line="5"@}
26848 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
26849 the program execution twice: first for the variable changing value, then
26850 for the watchpoint going out of scope.
26855 ^done,wpt=@{number="5",exp="C"@}
26860 *stopped,reason="watchpoint-trigger",
26861 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
26862 frame=@{func="callee4",args=[],
26863 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26864 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
26869 *stopped,reason="watchpoint-scope",wpnum="5",
26870 frame=@{func="callee3",args=[@{name="strarg",
26871 value="0x11940 \"A string argument.\""@}],
26872 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26873 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26877 Listing breakpoints and watchpoints, at different points in the program
26878 execution. Note that once the watchpoint goes out of scope, it is
26884 ^done,wpt=@{number="2",exp="C"@}
26887 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26888 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26889 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26890 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26891 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26892 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26893 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26894 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26895 addr="0x00010734",func="callee4",
26896 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26897 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
26899 bkpt=@{number="2",type="watchpoint",disp="keep",
26900 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
26905 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
26906 value=@{old="-276895068",new="3"@},
26907 frame=@{func="callee4",args=[],
26908 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26909 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
26912 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26913 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26914 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26915 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26916 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26917 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26918 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26919 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26920 addr="0x00010734",func="callee4",
26921 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26922 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
26924 bkpt=@{number="2",type="watchpoint",disp="keep",
26925 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
26929 ^done,reason="watchpoint-scope",wpnum="2",
26930 frame=@{func="callee3",args=[@{name="strarg",
26931 value="0x11940 \"A string argument.\""@}],
26932 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26933 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26936 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26937 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26938 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26939 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26940 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26941 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26942 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26943 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26944 addr="0x00010734",func="callee4",
26945 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26946 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
26947 thread-groups=["i1"],times="1"@}]@}
26952 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26953 @node GDB/MI Catchpoint Commands
26954 @section @sc{gdb/mi} Catchpoint Commands
26956 This section documents @sc{gdb/mi} commands for manipulating
26960 * Shared Library GDB/MI Catchpoint Commands::
26961 * Ada Exception GDB/MI Catchpoint Commands::
26964 @node Shared Library GDB/MI Catchpoint Commands
26965 @subsection Shared Library @sc{gdb/mi} Catchpoints
26967 @subheading The @code{-catch-load} Command
26968 @findex -catch-load
26970 @subsubheading Synopsis
26973 -catch-load [ -t ] [ -d ] @var{regexp}
26976 Add a catchpoint for library load events. If the @samp{-t} option is used,
26977 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
26978 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
26979 in a disabled state. The @samp{regexp} argument is a regular
26980 expression used to match the name of the loaded library.
26983 @subsubheading @value{GDBN} Command
26985 The corresponding @value{GDBN} command is @samp{catch load}.
26987 @subsubheading Example
26990 -catch-load -t foo.so
26991 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
26992 what="load of library matching foo.so",catch-type="load",times="0"@}
26997 @subheading The @code{-catch-unload} Command
26998 @findex -catch-unload
27000 @subsubheading Synopsis
27003 -catch-unload [ -t ] [ -d ] @var{regexp}
27006 Add a catchpoint for library unload events. If the @samp{-t} option is
27007 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
27008 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
27009 created in a disabled state. The @samp{regexp} argument is a regular
27010 expression used to match the name of the unloaded library.
27012 @subsubheading @value{GDBN} Command
27014 The corresponding @value{GDBN} command is @samp{catch unload}.
27016 @subsubheading Example
27019 -catch-unload -d bar.so
27020 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
27021 what="load of library matching bar.so",catch-type="unload",times="0"@}
27025 @node Ada Exception GDB/MI Catchpoint Commands
27026 @subsection Ada Exception @sc{gdb/mi} Catchpoints
27028 The following @sc{gdb/mi} commands can be used to create catchpoints
27029 that stop the execution when Ada exceptions are being raised.
27031 @subheading The @code{-catch-assert} Command
27032 @findex -catch-assert
27034 @subsubheading Synopsis
27037 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
27040 Add a catchpoint for failed Ada assertions.
27042 The possible optional parameters for this command are:
27045 @item -c @var{condition}
27046 Make the catchpoint conditional on @var{condition}.
27048 Create a disabled catchpoint.
27050 Create a temporary catchpoint.
27053 @subsubheading @value{GDBN} Command
27055 The corresponding @value{GDBN} command is @samp{catch assert}.
27057 @subsubheading Example
27061 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
27062 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
27063 thread-groups=["i1"],times="0",
27064 original-location="__gnat_debug_raise_assert_failure"@}
27068 @subheading The @code{-catch-exception} Command
27069 @findex -catch-exception
27071 @subsubheading Synopsis
27074 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
27078 Add a catchpoint stopping when Ada exceptions are raised.
27079 By default, the command stops the program when any Ada exception
27080 gets raised. But it is also possible, by using some of the
27081 optional parameters described below, to create more selective
27084 The possible optional parameters for this command are:
27087 @item -c @var{condition}
27088 Make the catchpoint conditional on @var{condition}.
27090 Create a disabled catchpoint.
27091 @item -e @var{exception-name}
27092 Only stop when @var{exception-name} is raised. This option cannot
27093 be used combined with @samp{-u}.
27095 Create a temporary catchpoint.
27097 Stop only when an unhandled exception gets raised. This option
27098 cannot be used combined with @samp{-e}.
27101 @subsubheading @value{GDBN} Command
27103 The corresponding @value{GDBN} commands are @samp{catch exception}
27104 and @samp{catch exception unhandled}.
27106 @subsubheading Example
27109 -catch-exception -e Program_Error
27110 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
27111 enabled="y",addr="0x0000000000404874",
27112 what="`Program_Error' Ada exception", thread-groups=["i1"],
27113 times="0",original-location="__gnat_debug_raise_exception"@}
27117 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27118 @node GDB/MI Program Context
27119 @section @sc{gdb/mi} Program Context
27121 @subheading The @code{-exec-arguments} Command
27122 @findex -exec-arguments
27125 @subsubheading Synopsis
27128 -exec-arguments @var{args}
27131 Set the inferior program arguments, to be used in the next
27134 @subsubheading @value{GDBN} Command
27136 The corresponding @value{GDBN} command is @samp{set args}.
27138 @subsubheading Example
27142 -exec-arguments -v word
27149 @subheading The @code{-exec-show-arguments} Command
27150 @findex -exec-show-arguments
27152 @subsubheading Synopsis
27155 -exec-show-arguments
27158 Print the arguments of the program.
27160 @subsubheading @value{GDBN} Command
27162 The corresponding @value{GDBN} command is @samp{show args}.
27164 @subsubheading Example
27169 @subheading The @code{-environment-cd} Command
27170 @findex -environment-cd
27172 @subsubheading Synopsis
27175 -environment-cd @var{pathdir}
27178 Set @value{GDBN}'s working directory.
27180 @subsubheading @value{GDBN} Command
27182 The corresponding @value{GDBN} command is @samp{cd}.
27184 @subsubheading Example
27188 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27194 @subheading The @code{-environment-directory} Command
27195 @findex -environment-directory
27197 @subsubheading Synopsis
27200 -environment-directory [ -r ] [ @var{pathdir} ]+
27203 Add directories @var{pathdir} to beginning of search path for source files.
27204 If the @samp{-r} option is used, the search path is reset to the default
27205 search path. If directories @var{pathdir} are supplied in addition to the
27206 @samp{-r} option, the search path is first reset and then addition
27208 Multiple directories may be specified, separated by blanks. Specifying
27209 multiple directories in a single command
27210 results in the directories added to the beginning of the
27211 search path in the same order they were presented in the command.
27212 If blanks are needed as
27213 part of a directory name, double-quotes should be used around
27214 the name. In the command output, the path will show up separated
27215 by the system directory-separator character. The directory-separator
27216 character must not be used
27217 in any directory name.
27218 If no directories are specified, the current search path is displayed.
27220 @subsubheading @value{GDBN} Command
27222 The corresponding @value{GDBN} command is @samp{dir}.
27224 @subsubheading Example
27228 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27229 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27231 -environment-directory ""
27232 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27234 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
27235 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
27237 -environment-directory -r
27238 ^done,source-path="$cdir:$cwd"
27243 @subheading The @code{-environment-path} Command
27244 @findex -environment-path
27246 @subsubheading Synopsis
27249 -environment-path [ -r ] [ @var{pathdir} ]+
27252 Add directories @var{pathdir} to beginning of search path for object files.
27253 If the @samp{-r} option is used, the search path is reset to the original
27254 search path that existed at gdb start-up. If directories @var{pathdir} are
27255 supplied in addition to the
27256 @samp{-r} option, the search path is first reset and then addition
27258 Multiple directories may be specified, separated by blanks. Specifying
27259 multiple directories in a single command
27260 results in the directories added to the beginning of the
27261 search path in the same order they were presented in the command.
27262 If blanks are needed as
27263 part of a directory name, double-quotes should be used around
27264 the name. In the command output, the path will show up separated
27265 by the system directory-separator character. The directory-separator
27266 character must not be used
27267 in any directory name.
27268 If no directories are specified, the current path is displayed.
27271 @subsubheading @value{GDBN} Command
27273 The corresponding @value{GDBN} command is @samp{path}.
27275 @subsubheading Example
27280 ^done,path="/usr/bin"
27282 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
27283 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
27285 -environment-path -r /usr/local/bin
27286 ^done,path="/usr/local/bin:/usr/bin"
27291 @subheading The @code{-environment-pwd} Command
27292 @findex -environment-pwd
27294 @subsubheading Synopsis
27300 Show the current working directory.
27302 @subsubheading @value{GDBN} Command
27304 The corresponding @value{GDBN} command is @samp{pwd}.
27306 @subsubheading Example
27311 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
27315 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27316 @node GDB/MI Thread Commands
27317 @section @sc{gdb/mi} Thread Commands
27320 @subheading The @code{-thread-info} Command
27321 @findex -thread-info
27323 @subsubheading Synopsis
27326 -thread-info [ @var{thread-id} ]
27329 Reports information about either a specific thread, if
27330 the @var{thread-id} parameter is present, or about all
27331 threads. When printing information about all threads,
27332 also reports the current thread.
27334 @subsubheading @value{GDBN} Command
27336 The @samp{info thread} command prints the same information
27339 @subsubheading Result
27341 The result is a list of threads. The following attributes are
27342 defined for a given thread:
27346 This field exists only for the current thread. It has the value @samp{*}.
27349 The identifier that @value{GDBN} uses to refer to the thread.
27352 The identifier that the target uses to refer to the thread.
27355 Extra information about the thread, in a target-specific format. This
27359 The name of the thread. If the user specified a name using the
27360 @code{thread name} command, then this name is given. Otherwise, if
27361 @value{GDBN} can extract the thread name from the target, then that
27362 name is given. If @value{GDBN} cannot find the thread name, then this
27366 The stack frame currently executing in the thread.
27369 The thread's state. The @samp{state} field may have the following
27374 The thread is stopped. Frame information is available for stopped
27378 The thread is running. There's no frame information for running
27384 If @value{GDBN} can find the CPU core on which this thread is running,
27385 then this field is the core identifier. This field is optional.
27389 @subsubheading Example
27394 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
27395 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
27396 args=[]@},state="running"@},
27397 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
27398 frame=@{level="0",addr="0x0804891f",func="foo",
27399 args=[@{name="i",value="10"@}],
27400 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
27401 state="running"@}],
27402 current-thread-id="1"
27406 @subheading The @code{-thread-list-ids} Command
27407 @findex -thread-list-ids
27409 @subsubheading Synopsis
27415 Produces a list of the currently known @value{GDBN} thread ids. At the
27416 end of the list it also prints the total number of such threads.
27418 This command is retained for historical reasons, the
27419 @code{-thread-info} command should be used instead.
27421 @subsubheading @value{GDBN} Command
27423 Part of @samp{info threads} supplies the same information.
27425 @subsubheading Example
27430 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27431 current-thread-id="1",number-of-threads="3"
27436 @subheading The @code{-thread-select} Command
27437 @findex -thread-select
27439 @subsubheading Synopsis
27442 -thread-select @var{threadnum}
27445 Make @var{threadnum} the current thread. It prints the number of the new
27446 current thread, and the topmost frame for that thread.
27448 This command is deprecated in favor of explicitly using the
27449 @samp{--thread} option to each command.
27451 @subsubheading @value{GDBN} Command
27453 The corresponding @value{GDBN} command is @samp{thread}.
27455 @subsubheading Example
27462 *stopped,reason="end-stepping-range",thread-id="2",line="187",
27463 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
27467 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27468 number-of-threads="3"
27471 ^done,new-thread-id="3",
27472 frame=@{level="0",func="vprintf",
27473 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
27474 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
27478 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27479 @node GDB/MI Ada Tasking Commands
27480 @section @sc{gdb/mi} Ada Tasking Commands
27482 @subheading The @code{-ada-task-info} Command
27483 @findex -ada-task-info
27485 @subsubheading Synopsis
27488 -ada-task-info [ @var{task-id} ]
27491 Reports information about either a specific Ada task, if the
27492 @var{task-id} parameter is present, or about all Ada tasks.
27494 @subsubheading @value{GDBN} Command
27496 The @samp{info tasks} command prints the same information
27497 about all Ada tasks (@pxref{Ada Tasks}).
27499 @subsubheading Result
27501 The result is a table of Ada tasks. The following columns are
27502 defined for each Ada task:
27506 This field exists only for the current thread. It has the value @samp{*}.
27509 The identifier that @value{GDBN} uses to refer to the Ada task.
27512 The identifier that the target uses to refer to the Ada task.
27515 The identifier of the thread corresponding to the Ada task.
27517 This field should always exist, as Ada tasks are always implemented
27518 on top of a thread. But if @value{GDBN} cannot find this corresponding
27519 thread for any reason, the field is omitted.
27522 This field exists only when the task was created by another task.
27523 In this case, it provides the ID of the parent task.
27526 The base priority of the task.
27529 The current state of the task. For a detailed description of the
27530 possible states, see @ref{Ada Tasks}.
27533 The name of the task.
27537 @subsubheading Example
27541 ^done,tasks=@{nr_rows="3",nr_cols="8",
27542 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
27543 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
27544 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
27545 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
27546 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
27547 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
27548 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
27549 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
27550 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
27551 state="Child Termination Wait",name="main_task"@}]@}
27555 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27556 @node GDB/MI Program Execution
27557 @section @sc{gdb/mi} Program Execution
27559 These are the asynchronous commands which generate the out-of-band
27560 record @samp{*stopped}. Currently @value{GDBN} only really executes
27561 asynchronously with remote targets and this interaction is mimicked in
27564 @subheading The @code{-exec-continue} Command
27565 @findex -exec-continue
27567 @subsubheading Synopsis
27570 -exec-continue [--reverse] [--all|--thread-group N]
27573 Resumes the execution of the inferior program, which will continue
27574 to execute until it reaches a debugger stop event. If the
27575 @samp{--reverse} option is specified, execution resumes in reverse until
27576 it reaches a stop event. Stop events may include
27579 breakpoints or watchpoints
27581 signals or exceptions
27583 the end of the process (or its beginning under @samp{--reverse})
27585 the end or beginning of a replay log if one is being used.
27587 In all-stop mode (@pxref{All-Stop
27588 Mode}), may resume only one thread, or all threads, depending on the
27589 value of the @samp{scheduler-locking} variable. If @samp{--all} is
27590 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
27591 ignored in all-stop mode. If the @samp{--thread-group} options is
27592 specified, then all threads in that thread group are resumed.
27594 @subsubheading @value{GDBN} Command
27596 The corresponding @value{GDBN} corresponding is @samp{continue}.
27598 @subsubheading Example
27605 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
27606 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
27612 @subheading The @code{-exec-finish} Command
27613 @findex -exec-finish
27615 @subsubheading Synopsis
27618 -exec-finish [--reverse]
27621 Resumes the execution of the inferior program until the current
27622 function is exited. Displays the results returned by the function.
27623 If the @samp{--reverse} option is specified, resumes the reverse
27624 execution of the inferior program until the point where current
27625 function was called.
27627 @subsubheading @value{GDBN} Command
27629 The corresponding @value{GDBN} command is @samp{finish}.
27631 @subsubheading Example
27633 Function returning @code{void}.
27640 *stopped,reason="function-finished",frame=@{func="main",args=[],
27641 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
27645 Function returning other than @code{void}. The name of the internal
27646 @value{GDBN} variable storing the result is printed, together with the
27653 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
27654 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
27655 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27656 gdb-result-var="$1",return-value="0"
27661 @subheading The @code{-exec-interrupt} Command
27662 @findex -exec-interrupt
27664 @subsubheading Synopsis
27667 -exec-interrupt [--all|--thread-group N]
27670 Interrupts the background execution of the target. Note how the token
27671 associated with the stop message is the one for the execution command
27672 that has been interrupted. The token for the interrupt itself only
27673 appears in the @samp{^done} output. If the user is trying to
27674 interrupt a non-running program, an error message will be printed.
27676 Note that when asynchronous execution is enabled, this command is
27677 asynchronous just like other execution commands. That is, first the
27678 @samp{^done} response will be printed, and the target stop will be
27679 reported after that using the @samp{*stopped} notification.
27681 In non-stop mode, only the context thread is interrupted by default.
27682 All threads (in all inferiors) will be interrupted if the
27683 @samp{--all} option is specified. If the @samp{--thread-group}
27684 option is specified, all threads in that group will be interrupted.
27686 @subsubheading @value{GDBN} Command
27688 The corresponding @value{GDBN} command is @samp{interrupt}.
27690 @subsubheading Example
27701 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
27702 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
27703 fullname="/home/foo/bar/try.c",line="13"@}
27708 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
27712 @subheading The @code{-exec-jump} Command
27715 @subsubheading Synopsis
27718 -exec-jump @var{location}
27721 Resumes execution of the inferior program at the location specified by
27722 parameter. @xref{Specify Location}, for a description of the
27723 different forms of @var{location}.
27725 @subsubheading @value{GDBN} Command
27727 The corresponding @value{GDBN} command is @samp{jump}.
27729 @subsubheading Example
27732 -exec-jump foo.c:10
27733 *running,thread-id="all"
27738 @subheading The @code{-exec-next} Command
27741 @subsubheading Synopsis
27744 -exec-next [--reverse]
27747 Resumes execution of the inferior program, stopping when the beginning
27748 of the next source line is reached.
27750 If the @samp{--reverse} option is specified, resumes reverse execution
27751 of the inferior program, stopping at the beginning of the previous
27752 source line. If you issue this command on the first line of a
27753 function, it will take you back to the caller of that function, to the
27754 source line where the function was called.
27757 @subsubheading @value{GDBN} Command
27759 The corresponding @value{GDBN} command is @samp{next}.
27761 @subsubheading Example
27767 *stopped,reason="end-stepping-range",line="8",file="hello.c"
27772 @subheading The @code{-exec-next-instruction} Command
27773 @findex -exec-next-instruction
27775 @subsubheading Synopsis
27778 -exec-next-instruction [--reverse]
27781 Executes one machine instruction. If the instruction is a function
27782 call, continues until the function returns. If the program stops at an
27783 instruction in the middle of a source line, the address will be
27786 If the @samp{--reverse} option is specified, resumes reverse execution
27787 of the inferior program, stopping at the previous instruction. If the
27788 previously executed instruction was a return from another function,
27789 it will continue to execute in reverse until the call to that function
27790 (from the current stack frame) is reached.
27792 @subsubheading @value{GDBN} Command
27794 The corresponding @value{GDBN} command is @samp{nexti}.
27796 @subsubheading Example
27800 -exec-next-instruction
27804 *stopped,reason="end-stepping-range",
27805 addr="0x000100d4",line="5",file="hello.c"
27810 @subheading The @code{-exec-return} Command
27811 @findex -exec-return
27813 @subsubheading Synopsis
27819 Makes current function return immediately. Doesn't execute the inferior.
27820 Displays the new current frame.
27822 @subsubheading @value{GDBN} Command
27824 The corresponding @value{GDBN} command is @samp{return}.
27826 @subsubheading Example
27830 200-break-insert callee4
27831 200^done,bkpt=@{number="1",addr="0x00010734",
27832 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27837 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27838 frame=@{func="callee4",args=[],
27839 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27840 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27846 111^done,frame=@{level="0",func="callee3",
27847 args=[@{name="strarg",
27848 value="0x11940 \"A string argument.\""@}],
27849 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27850 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27855 @subheading The @code{-exec-run} Command
27858 @subsubheading Synopsis
27861 -exec-run [ --all | --thread-group N ] [ --start ]
27864 Starts execution of the inferior from the beginning. The inferior
27865 executes until either a breakpoint is encountered or the program
27866 exits. In the latter case the output will include an exit code, if
27867 the program has exited exceptionally.
27869 When neither the @samp{--all} nor the @samp{--thread-group} option
27870 is specified, the current inferior is started. If the
27871 @samp{--thread-group} option is specified, it should refer to a thread
27872 group of type @samp{process}, and that thread group will be started.
27873 If the @samp{--all} option is specified, then all inferiors will be started.
27875 Using the @samp{--start} option instructs the debugger to stop
27876 the execution at the start of the inferior's main subprogram,
27877 following the same behavior as the @code{start} command
27878 (@pxref{Starting}).
27880 @subsubheading @value{GDBN} Command
27882 The corresponding @value{GDBN} command is @samp{run}.
27884 @subsubheading Examples
27889 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
27894 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27895 frame=@{func="main",args=[],file="recursive2.c",
27896 fullname="/home/foo/bar/recursive2.c",line="4"@}
27901 Program exited normally:
27909 *stopped,reason="exited-normally"
27914 Program exited exceptionally:
27922 *stopped,reason="exited",exit-code="01"
27926 Another way the program can terminate is if it receives a signal such as
27927 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
27931 *stopped,reason="exited-signalled",signal-name="SIGINT",
27932 signal-meaning="Interrupt"
27936 @c @subheading -exec-signal
27939 @subheading The @code{-exec-step} Command
27942 @subsubheading Synopsis
27945 -exec-step [--reverse]
27948 Resumes execution of the inferior program, stopping when the beginning
27949 of the next source line is reached, if the next source line is not a
27950 function call. If it is, stop at the first instruction of the called
27951 function. If the @samp{--reverse} option is specified, resumes reverse
27952 execution of the inferior program, stopping at the beginning of the
27953 previously executed source line.
27955 @subsubheading @value{GDBN} Command
27957 The corresponding @value{GDBN} command is @samp{step}.
27959 @subsubheading Example
27961 Stepping into a function:
27967 *stopped,reason="end-stepping-range",
27968 frame=@{func="foo",args=[@{name="a",value="10"@},
27969 @{name="b",value="0"@}],file="recursive2.c",
27970 fullname="/home/foo/bar/recursive2.c",line="11"@}
27980 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
27985 @subheading The @code{-exec-step-instruction} Command
27986 @findex -exec-step-instruction
27988 @subsubheading Synopsis
27991 -exec-step-instruction [--reverse]
27994 Resumes the inferior which executes one machine instruction. If the
27995 @samp{--reverse} option is specified, resumes reverse execution of the
27996 inferior program, stopping at the previously executed instruction.
27997 The output, once @value{GDBN} has stopped, will vary depending on
27998 whether we have stopped in the middle of a source line or not. In the
27999 former case, the address at which the program stopped will be printed
28002 @subsubheading @value{GDBN} Command
28004 The corresponding @value{GDBN} command is @samp{stepi}.
28006 @subsubheading Example
28010 -exec-step-instruction
28014 *stopped,reason="end-stepping-range",
28015 frame=@{func="foo",args=[],file="try.c",
28016 fullname="/home/foo/bar/try.c",line="10"@}
28018 -exec-step-instruction
28022 *stopped,reason="end-stepping-range",
28023 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
28024 fullname="/home/foo/bar/try.c",line="10"@}
28029 @subheading The @code{-exec-until} Command
28030 @findex -exec-until
28032 @subsubheading Synopsis
28035 -exec-until [ @var{location} ]
28038 Executes the inferior until the @var{location} specified in the
28039 argument is reached. If there is no argument, the inferior executes
28040 until a source line greater than the current one is reached. The
28041 reason for stopping in this case will be @samp{location-reached}.
28043 @subsubheading @value{GDBN} Command
28045 The corresponding @value{GDBN} command is @samp{until}.
28047 @subsubheading Example
28051 -exec-until recursive2.c:6
28055 *stopped,reason="location-reached",frame=@{func="main",args=[],
28056 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
28061 @subheading -file-clear
28062 Is this going away????
28065 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28066 @node GDB/MI Stack Manipulation
28067 @section @sc{gdb/mi} Stack Manipulation Commands
28069 @subheading The @code{-enable-frame-filters} Command
28070 @findex -enable-frame-filters
28073 -enable-frame-filters
28076 @value{GDBN} allows Python-based frame filters to affect the output of
28077 the MI commands relating to stack traces. As there is no way to
28078 implement this in a fully backward-compatible way, a front end must
28079 request that this functionality be enabled.
28081 Once enabled, this feature cannot be disabled.
28083 Note that if Python support has not been compiled into @value{GDBN},
28084 this command will still succeed (and do nothing).
28086 @subheading The @code{-stack-info-frame} Command
28087 @findex -stack-info-frame
28089 @subsubheading Synopsis
28095 Get info on the selected frame.
28097 @subsubheading @value{GDBN} Command
28099 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
28100 (without arguments).
28102 @subsubheading Example
28107 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
28108 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28109 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
28113 @subheading The @code{-stack-info-depth} Command
28114 @findex -stack-info-depth
28116 @subsubheading Synopsis
28119 -stack-info-depth [ @var{max-depth} ]
28122 Return the depth of the stack. If the integer argument @var{max-depth}
28123 is specified, do not count beyond @var{max-depth} frames.
28125 @subsubheading @value{GDBN} Command
28127 There's no equivalent @value{GDBN} command.
28129 @subsubheading Example
28131 For a stack with frame levels 0 through 11:
28138 -stack-info-depth 4
28141 -stack-info-depth 12
28144 -stack-info-depth 11
28147 -stack-info-depth 13
28152 @anchor{-stack-list-arguments}
28153 @subheading The @code{-stack-list-arguments} Command
28154 @findex -stack-list-arguments
28156 @subsubheading Synopsis
28159 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28160 [ @var{low-frame} @var{high-frame} ]
28163 Display a list of the arguments for the frames between @var{low-frame}
28164 and @var{high-frame} (inclusive). If @var{low-frame} and
28165 @var{high-frame} are not provided, list the arguments for the whole
28166 call stack. If the two arguments are equal, show the single frame
28167 at the corresponding level. It is an error if @var{low-frame} is
28168 larger than the actual number of frames. On the other hand,
28169 @var{high-frame} may be larger than the actual number of frames, in
28170 which case only existing frames will be returned.
28172 If @var{print-values} is 0 or @code{--no-values}, print only the names of
28173 the variables; if it is 1 or @code{--all-values}, print also their
28174 values; and if it is 2 or @code{--simple-values}, print the name,
28175 type and value for simple data types, and the name and type for arrays,
28176 structures and unions. If the option @code{--no-frame-filters} is
28177 supplied, then Python frame filters will not be executed.
28179 If the @code{--skip-unavailable} option is specified, arguments that
28180 are not available are not listed. Partially available arguments
28181 are still displayed, however.
28183 Use of this command to obtain arguments in a single frame is
28184 deprecated in favor of the @samp{-stack-list-variables} command.
28186 @subsubheading @value{GDBN} Command
28188 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
28189 @samp{gdb_get_args} command which partially overlaps with the
28190 functionality of @samp{-stack-list-arguments}.
28192 @subsubheading Example
28199 frame=@{level="0",addr="0x00010734",func="callee4",
28200 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28201 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
28202 frame=@{level="1",addr="0x0001076c",func="callee3",
28203 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28204 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
28205 frame=@{level="2",addr="0x0001078c",func="callee2",
28206 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28207 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
28208 frame=@{level="3",addr="0x000107b4",func="callee1",
28209 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28210 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
28211 frame=@{level="4",addr="0x000107e0",func="main",
28212 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28213 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
28215 -stack-list-arguments 0
28218 frame=@{level="0",args=[]@},
28219 frame=@{level="1",args=[name="strarg"]@},
28220 frame=@{level="2",args=[name="intarg",name="strarg"]@},
28221 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
28222 frame=@{level="4",args=[]@}]
28224 -stack-list-arguments 1
28227 frame=@{level="0",args=[]@},
28229 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28230 frame=@{level="2",args=[
28231 @{name="intarg",value="2"@},
28232 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28233 @{frame=@{level="3",args=[
28234 @{name="intarg",value="2"@},
28235 @{name="strarg",value="0x11940 \"A string argument.\""@},
28236 @{name="fltarg",value="3.5"@}]@},
28237 frame=@{level="4",args=[]@}]
28239 -stack-list-arguments 0 2 2
28240 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
28242 -stack-list-arguments 1 2 2
28243 ^done,stack-args=[frame=@{level="2",
28244 args=[@{name="intarg",value="2"@},
28245 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
28249 @c @subheading -stack-list-exception-handlers
28252 @anchor{-stack-list-frames}
28253 @subheading The @code{-stack-list-frames} Command
28254 @findex -stack-list-frames
28256 @subsubheading Synopsis
28259 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
28262 List the frames currently on the stack. For each frame it displays the
28267 The frame number, 0 being the topmost frame, i.e., the innermost function.
28269 The @code{$pc} value for that frame.
28273 File name of the source file where the function lives.
28274 @item @var{fullname}
28275 The full file name of the source file where the function lives.
28277 Line number corresponding to the @code{$pc}.
28279 The shared library where this function is defined. This is only given
28280 if the frame's function is not known.
28283 If invoked without arguments, this command prints a backtrace for the
28284 whole stack. If given two integer arguments, it shows the frames whose
28285 levels are between the two arguments (inclusive). If the two arguments
28286 are equal, it shows the single frame at the corresponding level. It is
28287 an error if @var{low-frame} is larger than the actual number of
28288 frames. On the other hand, @var{high-frame} may be larger than the
28289 actual number of frames, in which case only existing frames will be
28290 returned. If the option @code{--no-frame-filters} is supplied, then
28291 Python frame filters will not be executed.
28293 @subsubheading @value{GDBN} Command
28295 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
28297 @subsubheading Example
28299 Full stack backtrace:
28305 [frame=@{level="0",addr="0x0001076c",func="foo",
28306 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
28307 frame=@{level="1",addr="0x000107a4",func="foo",
28308 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28309 frame=@{level="2",addr="0x000107a4",func="foo",
28310 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28311 frame=@{level="3",addr="0x000107a4",func="foo",
28312 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28313 frame=@{level="4",addr="0x000107a4",func="foo",
28314 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28315 frame=@{level="5",addr="0x000107a4",func="foo",
28316 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28317 frame=@{level="6",addr="0x000107a4",func="foo",
28318 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28319 frame=@{level="7",addr="0x000107a4",func="foo",
28320 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28321 frame=@{level="8",addr="0x000107a4",func="foo",
28322 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28323 frame=@{level="9",addr="0x000107a4",func="foo",
28324 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28325 frame=@{level="10",addr="0x000107a4",func="foo",
28326 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28327 frame=@{level="11",addr="0x00010738",func="main",
28328 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
28332 Show frames between @var{low_frame} and @var{high_frame}:
28336 -stack-list-frames 3 5
28338 [frame=@{level="3",addr="0x000107a4",func="foo",
28339 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28340 frame=@{level="4",addr="0x000107a4",func="foo",
28341 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28342 frame=@{level="5",addr="0x000107a4",func="foo",
28343 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28347 Show a single frame:
28351 -stack-list-frames 3 3
28353 [frame=@{level="3",addr="0x000107a4",func="foo",
28354 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28359 @subheading The @code{-stack-list-locals} Command
28360 @findex -stack-list-locals
28361 @anchor{-stack-list-locals}
28363 @subsubheading Synopsis
28366 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28369 Display the local variable names for the selected frame. If
28370 @var{print-values} is 0 or @code{--no-values}, print only the names of
28371 the variables; if it is 1 or @code{--all-values}, print also their
28372 values; and if it is 2 or @code{--simple-values}, print the name,
28373 type and value for simple data types, and the name and type for arrays,
28374 structures and unions. In this last case, a frontend can immediately
28375 display the value of simple data types and create variable objects for
28376 other data types when the user wishes to explore their values in
28377 more detail. If the option @code{--no-frame-filters} is supplied, then
28378 Python frame filters will not be executed.
28380 If the @code{--skip-unavailable} option is specified, local variables
28381 that are not available are not listed. Partially available local
28382 variables are still displayed, however.
28384 This command is deprecated in favor of the
28385 @samp{-stack-list-variables} command.
28387 @subsubheading @value{GDBN} Command
28389 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
28391 @subsubheading Example
28395 -stack-list-locals 0
28396 ^done,locals=[name="A",name="B",name="C"]
28398 -stack-list-locals --all-values
28399 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
28400 @{name="C",value="@{1, 2, 3@}"@}]
28401 -stack-list-locals --simple-values
28402 ^done,locals=[@{name="A",type="int",value="1"@},
28403 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
28407 @anchor{-stack-list-variables}
28408 @subheading The @code{-stack-list-variables} Command
28409 @findex -stack-list-variables
28411 @subsubheading Synopsis
28414 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28417 Display the names of local variables and function arguments for the selected frame. If
28418 @var{print-values} is 0 or @code{--no-values}, print only the names of
28419 the variables; if it is 1 or @code{--all-values}, print also their
28420 values; and if it is 2 or @code{--simple-values}, print the name,
28421 type and value for simple data types, and the name and type for arrays,
28422 structures and unions. If the option @code{--no-frame-filters} is
28423 supplied, then Python frame filters will not be executed.
28425 If the @code{--skip-unavailable} option is specified, local variables
28426 and arguments that are not available are not listed. Partially
28427 available arguments and local variables are still displayed, however.
28429 @subsubheading Example
28433 -stack-list-variables --thread 1 --frame 0 --all-values
28434 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
28439 @subheading The @code{-stack-select-frame} Command
28440 @findex -stack-select-frame
28442 @subsubheading Synopsis
28445 -stack-select-frame @var{framenum}
28448 Change the selected frame. Select a different frame @var{framenum} on
28451 This command in deprecated in favor of passing the @samp{--frame}
28452 option to every command.
28454 @subsubheading @value{GDBN} Command
28456 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
28457 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
28459 @subsubheading Example
28463 -stack-select-frame 2
28468 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28469 @node GDB/MI Variable Objects
28470 @section @sc{gdb/mi} Variable Objects
28474 @subheading Motivation for Variable Objects in @sc{gdb/mi}
28476 For the implementation of a variable debugger window (locals, watched
28477 expressions, etc.), we are proposing the adaptation of the existing code
28478 used by @code{Insight}.
28480 The two main reasons for that are:
28484 It has been proven in practice (it is already on its second generation).
28487 It will shorten development time (needless to say how important it is
28491 The original interface was designed to be used by Tcl code, so it was
28492 slightly changed so it could be used through @sc{gdb/mi}. This section
28493 describes the @sc{gdb/mi} operations that will be available and gives some
28494 hints about their use.
28496 @emph{Note}: In addition to the set of operations described here, we
28497 expect the @sc{gui} implementation of a variable window to require, at
28498 least, the following operations:
28501 @item @code{-gdb-show} @code{output-radix}
28502 @item @code{-stack-list-arguments}
28503 @item @code{-stack-list-locals}
28504 @item @code{-stack-select-frame}
28509 @subheading Introduction to Variable Objects
28511 @cindex variable objects in @sc{gdb/mi}
28513 Variable objects are "object-oriented" MI interface for examining and
28514 changing values of expressions. Unlike some other MI interfaces that
28515 work with expressions, variable objects are specifically designed for
28516 simple and efficient presentation in the frontend. A variable object
28517 is identified by string name. When a variable object is created, the
28518 frontend specifies the expression for that variable object. The
28519 expression can be a simple variable, or it can be an arbitrary complex
28520 expression, and can even involve CPU registers. After creating a
28521 variable object, the frontend can invoke other variable object
28522 operations---for example to obtain or change the value of a variable
28523 object, or to change display format.
28525 Variable objects have hierarchical tree structure. Any variable object
28526 that corresponds to a composite type, such as structure in C, has
28527 a number of child variable objects, for example corresponding to each
28528 element of a structure. A child variable object can itself have
28529 children, recursively. Recursion ends when we reach
28530 leaf variable objects, which always have built-in types. Child variable
28531 objects are created only by explicit request, so if a frontend
28532 is not interested in the children of a particular variable object, no
28533 child will be created.
28535 For a leaf variable object it is possible to obtain its value as a
28536 string, or set the value from a string. String value can be also
28537 obtained for a non-leaf variable object, but it's generally a string
28538 that only indicates the type of the object, and does not list its
28539 contents. Assignment to a non-leaf variable object is not allowed.
28541 A frontend does not need to read the values of all variable objects each time
28542 the program stops. Instead, MI provides an update command that lists all
28543 variable objects whose values has changed since the last update
28544 operation. This considerably reduces the amount of data that must
28545 be transferred to the frontend. As noted above, children variable
28546 objects are created on demand, and only leaf variable objects have a
28547 real value. As result, gdb will read target memory only for leaf
28548 variables that frontend has created.
28550 The automatic update is not always desirable. For example, a frontend
28551 might want to keep a value of some expression for future reference,
28552 and never update it. For another example, fetching memory is
28553 relatively slow for embedded targets, so a frontend might want
28554 to disable automatic update for the variables that are either not
28555 visible on the screen, or ``closed''. This is possible using so
28556 called ``frozen variable objects''. Such variable objects are never
28557 implicitly updated.
28559 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
28560 fixed variable object, the expression is parsed when the variable
28561 object is created, including associating identifiers to specific
28562 variables. The meaning of expression never changes. For a floating
28563 variable object the values of variables whose names appear in the
28564 expressions are re-evaluated every time in the context of the current
28565 frame. Consider this example:
28570 struct work_state state;
28577 If a fixed variable object for the @code{state} variable is created in
28578 this function, and we enter the recursive call, the variable
28579 object will report the value of @code{state} in the top-level
28580 @code{do_work} invocation. On the other hand, a floating variable
28581 object will report the value of @code{state} in the current frame.
28583 If an expression specified when creating a fixed variable object
28584 refers to a local variable, the variable object becomes bound to the
28585 thread and frame in which the variable object is created. When such
28586 variable object is updated, @value{GDBN} makes sure that the
28587 thread/frame combination the variable object is bound to still exists,
28588 and re-evaluates the variable object in context of that thread/frame.
28590 The following is the complete set of @sc{gdb/mi} operations defined to
28591 access this functionality:
28593 @multitable @columnfractions .4 .6
28594 @item @strong{Operation}
28595 @tab @strong{Description}
28597 @item @code{-enable-pretty-printing}
28598 @tab enable Python-based pretty-printing
28599 @item @code{-var-create}
28600 @tab create a variable object
28601 @item @code{-var-delete}
28602 @tab delete the variable object and/or its children
28603 @item @code{-var-set-format}
28604 @tab set the display format of this variable
28605 @item @code{-var-show-format}
28606 @tab show the display format of this variable
28607 @item @code{-var-info-num-children}
28608 @tab tells how many children this object has
28609 @item @code{-var-list-children}
28610 @tab return a list of the object's children
28611 @item @code{-var-info-type}
28612 @tab show the type of this variable object
28613 @item @code{-var-info-expression}
28614 @tab print parent-relative expression that this variable object represents
28615 @item @code{-var-info-path-expression}
28616 @tab print full expression that this variable object represents
28617 @item @code{-var-show-attributes}
28618 @tab is this variable editable? does it exist here?
28619 @item @code{-var-evaluate-expression}
28620 @tab get the value of this variable
28621 @item @code{-var-assign}
28622 @tab set the value of this variable
28623 @item @code{-var-update}
28624 @tab update the variable and its children
28625 @item @code{-var-set-frozen}
28626 @tab set frozeness attribute
28627 @item @code{-var-set-update-range}
28628 @tab set range of children to display on update
28631 In the next subsection we describe each operation in detail and suggest
28632 how it can be used.
28634 @subheading Description And Use of Operations on Variable Objects
28636 @subheading The @code{-enable-pretty-printing} Command
28637 @findex -enable-pretty-printing
28640 -enable-pretty-printing
28643 @value{GDBN} allows Python-based visualizers to affect the output of the
28644 MI variable object commands. However, because there was no way to
28645 implement this in a fully backward-compatible way, a front end must
28646 request that this functionality be enabled.
28648 Once enabled, this feature cannot be disabled.
28650 Note that if Python support has not been compiled into @value{GDBN},
28651 this command will still succeed (and do nothing).
28653 This feature is currently (as of @value{GDBN} 7.0) experimental, and
28654 may work differently in future versions of @value{GDBN}.
28656 @subheading The @code{-var-create} Command
28657 @findex -var-create
28659 @subsubheading Synopsis
28662 -var-create @{@var{name} | "-"@}
28663 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
28666 This operation creates a variable object, which allows the monitoring of
28667 a variable, the result of an expression, a memory cell or a CPU
28670 The @var{name} parameter is the string by which the object can be
28671 referenced. It must be unique. If @samp{-} is specified, the varobj
28672 system will generate a string ``varNNNNNN'' automatically. It will be
28673 unique provided that one does not specify @var{name} of that format.
28674 The command fails if a duplicate name is found.
28676 The frame under which the expression should be evaluated can be
28677 specified by @var{frame-addr}. A @samp{*} indicates that the current
28678 frame should be used. A @samp{@@} indicates that a floating variable
28679 object must be created.
28681 @var{expression} is any expression valid on the current language set (must not
28682 begin with a @samp{*}), or one of the following:
28686 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
28689 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
28692 @samp{$@var{regname}} --- a CPU register name
28695 @cindex dynamic varobj
28696 A varobj's contents may be provided by a Python-based pretty-printer. In this
28697 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
28698 have slightly different semantics in some cases. If the
28699 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
28700 will never create a dynamic varobj. This ensures backward
28701 compatibility for existing clients.
28703 @subsubheading Result
28705 This operation returns attributes of the newly-created varobj. These
28710 The name of the varobj.
28713 The number of children of the varobj. This number is not necessarily
28714 reliable for a dynamic varobj. Instead, you must examine the
28715 @samp{has_more} attribute.
28718 The varobj's scalar value. For a varobj whose type is some sort of
28719 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
28720 will not be interesting.
28723 The varobj's type. This is a string representation of the type, as
28724 would be printed by the @value{GDBN} CLI. If @samp{print object}
28725 (@pxref{Print Settings, set print object}) is set to @code{on}, the
28726 @emph{actual} (derived) type of the object is shown rather than the
28727 @emph{declared} one.
28730 If a variable object is bound to a specific thread, then this is the
28731 thread's identifier.
28734 For a dynamic varobj, this indicates whether there appear to be any
28735 children available. For a non-dynamic varobj, this will be 0.
28738 This attribute will be present and have the value @samp{1} if the
28739 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28740 then this attribute will not be present.
28743 A dynamic varobj can supply a display hint to the front end. The
28744 value comes directly from the Python pretty-printer object's
28745 @code{display_hint} method. @xref{Pretty Printing API}.
28748 Typical output will look like this:
28751 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
28752 has_more="@var{has_more}"
28756 @subheading The @code{-var-delete} Command
28757 @findex -var-delete
28759 @subsubheading Synopsis
28762 -var-delete [ -c ] @var{name}
28765 Deletes a previously created variable object and all of its children.
28766 With the @samp{-c} option, just deletes the children.
28768 Returns an error if the object @var{name} is not found.
28771 @subheading The @code{-var-set-format} Command
28772 @findex -var-set-format
28774 @subsubheading Synopsis
28777 -var-set-format @var{name} @var{format-spec}
28780 Sets the output format for the value of the object @var{name} to be
28783 @anchor{-var-set-format}
28784 The syntax for the @var{format-spec} is as follows:
28787 @var{format-spec} @expansion{}
28788 @{binary | decimal | hexadecimal | octal | natural@}
28791 The natural format is the default format choosen automatically
28792 based on the variable type (like decimal for an @code{int}, hex
28793 for pointers, etc.).
28795 For a variable with children, the format is set only on the
28796 variable itself, and the children are not affected.
28798 @subheading The @code{-var-show-format} Command
28799 @findex -var-show-format
28801 @subsubheading Synopsis
28804 -var-show-format @var{name}
28807 Returns the format used to display the value of the object @var{name}.
28810 @var{format} @expansion{}
28815 @subheading The @code{-var-info-num-children} Command
28816 @findex -var-info-num-children
28818 @subsubheading Synopsis
28821 -var-info-num-children @var{name}
28824 Returns the number of children of a variable object @var{name}:
28830 Note that this number is not completely reliable for a dynamic varobj.
28831 It will return the current number of children, but more children may
28835 @subheading The @code{-var-list-children} Command
28836 @findex -var-list-children
28838 @subsubheading Synopsis
28841 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
28843 @anchor{-var-list-children}
28845 Return a list of the children of the specified variable object and
28846 create variable objects for them, if they do not already exist. With
28847 a single argument or if @var{print-values} has a value of 0 or
28848 @code{--no-values}, print only the names of the variables; if
28849 @var{print-values} is 1 or @code{--all-values}, also print their
28850 values; and if it is 2 or @code{--simple-values} print the name and
28851 value for simple data types and just the name for arrays, structures
28854 @var{from} and @var{to}, if specified, indicate the range of children
28855 to report. If @var{from} or @var{to} is less than zero, the range is
28856 reset and all children will be reported. Otherwise, children starting
28857 at @var{from} (zero-based) and up to and excluding @var{to} will be
28860 If a child range is requested, it will only affect the current call to
28861 @code{-var-list-children}, but not future calls to @code{-var-update}.
28862 For this, you must instead use @code{-var-set-update-range}. The
28863 intent of this approach is to enable a front end to implement any
28864 update approach it likes; for example, scrolling a view may cause the
28865 front end to request more children with @code{-var-list-children}, and
28866 then the front end could call @code{-var-set-update-range} with a
28867 different range to ensure that future updates are restricted to just
28870 For each child the following results are returned:
28875 Name of the variable object created for this child.
28878 The expression to be shown to the user by the front end to designate this child.
28879 For example this may be the name of a structure member.
28881 For a dynamic varobj, this value cannot be used to form an
28882 expression. There is no way to do this at all with a dynamic varobj.
28884 For C/C@t{++} structures there are several pseudo children returned to
28885 designate access qualifiers. For these pseudo children @var{exp} is
28886 @samp{public}, @samp{private}, or @samp{protected}. In this case the
28887 type and value are not present.
28889 A dynamic varobj will not report the access qualifying
28890 pseudo-children, regardless of the language. This information is not
28891 available at all with a dynamic varobj.
28894 Number of children this child has. For a dynamic varobj, this will be
28898 The type of the child. If @samp{print object}
28899 (@pxref{Print Settings, set print object}) is set to @code{on}, the
28900 @emph{actual} (derived) type of the object is shown rather than the
28901 @emph{declared} one.
28904 If values were requested, this is the value.
28907 If this variable object is associated with a thread, this is the thread id.
28908 Otherwise this result is not present.
28911 If the variable object is frozen, this variable will be present with a value of 1.
28914 A dynamic varobj can supply a display hint to the front end. The
28915 value comes directly from the Python pretty-printer object's
28916 @code{display_hint} method. @xref{Pretty Printing API}.
28919 This attribute will be present and have the value @samp{1} if the
28920 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28921 then this attribute will not be present.
28925 The result may have its own attributes:
28929 A dynamic varobj can supply a display hint to the front end. The
28930 value comes directly from the Python pretty-printer object's
28931 @code{display_hint} method. @xref{Pretty Printing API}.
28934 This is an integer attribute which is nonzero if there are children
28935 remaining after the end of the selected range.
28938 @subsubheading Example
28942 -var-list-children n
28943 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28944 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
28946 -var-list-children --all-values n
28947 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28948 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
28952 @subheading The @code{-var-info-type} Command
28953 @findex -var-info-type
28955 @subsubheading Synopsis
28958 -var-info-type @var{name}
28961 Returns the type of the specified variable @var{name}. The type is
28962 returned as a string in the same format as it is output by the
28966 type=@var{typename}
28970 @subheading The @code{-var-info-expression} Command
28971 @findex -var-info-expression
28973 @subsubheading Synopsis
28976 -var-info-expression @var{name}
28979 Returns a string that is suitable for presenting this
28980 variable object in user interface. The string is generally
28981 not valid expression in the current language, and cannot be evaluated.
28983 For example, if @code{a} is an array, and variable object
28984 @code{A} was created for @code{a}, then we'll get this output:
28987 (gdb) -var-info-expression A.1
28988 ^done,lang="C",exp="1"
28992 Here, the value of @code{lang} is the language name, which can be
28993 found in @ref{Supported Languages}.
28995 Note that the output of the @code{-var-list-children} command also
28996 includes those expressions, so the @code{-var-info-expression} command
28999 @subheading The @code{-var-info-path-expression} Command
29000 @findex -var-info-path-expression
29002 @subsubheading Synopsis
29005 -var-info-path-expression @var{name}
29008 Returns an expression that can be evaluated in the current
29009 context and will yield the same value that a variable object has.
29010 Compare this with the @code{-var-info-expression} command, which
29011 result can be used only for UI presentation. Typical use of
29012 the @code{-var-info-path-expression} command is creating a
29013 watchpoint from a variable object.
29015 This command is currently not valid for children of a dynamic varobj,
29016 and will give an error when invoked on one.
29018 For example, suppose @code{C} is a C@t{++} class, derived from class
29019 @code{Base}, and that the @code{Base} class has a member called
29020 @code{m_size}. Assume a variable @code{c} is has the type of
29021 @code{C} and a variable object @code{C} was created for variable
29022 @code{c}. Then, we'll get this output:
29024 (gdb) -var-info-path-expression C.Base.public.m_size
29025 ^done,path_expr=((Base)c).m_size)
29028 @subheading The @code{-var-show-attributes} Command
29029 @findex -var-show-attributes
29031 @subsubheading Synopsis
29034 -var-show-attributes @var{name}
29037 List attributes of the specified variable object @var{name}:
29040 status=@var{attr} [ ( ,@var{attr} )* ]
29044 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
29046 @subheading The @code{-var-evaluate-expression} Command
29047 @findex -var-evaluate-expression
29049 @subsubheading Synopsis
29052 -var-evaluate-expression [-f @var{format-spec}] @var{name}
29055 Evaluates the expression that is represented by the specified variable
29056 object and returns its value as a string. The format of the string
29057 can be specified with the @samp{-f} option. The possible values of
29058 this option are the same as for @code{-var-set-format}
29059 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
29060 the current display format will be used. The current display format
29061 can be changed using the @code{-var-set-format} command.
29067 Note that one must invoke @code{-var-list-children} for a variable
29068 before the value of a child variable can be evaluated.
29070 @subheading The @code{-var-assign} Command
29071 @findex -var-assign
29073 @subsubheading Synopsis
29076 -var-assign @var{name} @var{expression}
29079 Assigns the value of @var{expression} to the variable object specified
29080 by @var{name}. The object must be @samp{editable}. If the variable's
29081 value is altered by the assign, the variable will show up in any
29082 subsequent @code{-var-update} list.
29084 @subsubheading Example
29092 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
29096 @subheading The @code{-var-update} Command
29097 @findex -var-update
29099 @subsubheading Synopsis
29102 -var-update [@var{print-values}] @{@var{name} | "*"@}
29105 Reevaluate the expressions corresponding to the variable object
29106 @var{name} and all its direct and indirect children, and return the
29107 list of variable objects whose values have changed; @var{name} must
29108 be a root variable object. Here, ``changed'' means that the result of
29109 @code{-var-evaluate-expression} before and after the
29110 @code{-var-update} is different. If @samp{*} is used as the variable
29111 object names, all existing variable objects are updated, except
29112 for frozen ones (@pxref{-var-set-frozen}). The option
29113 @var{print-values} determines whether both names and values, or just
29114 names are printed. The possible values of this option are the same
29115 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
29116 recommended to use the @samp{--all-values} option, to reduce the
29117 number of MI commands needed on each program stop.
29119 With the @samp{*} parameter, if a variable object is bound to a
29120 currently running thread, it will not be updated, without any
29123 If @code{-var-set-update-range} was previously used on a varobj, then
29124 only the selected range of children will be reported.
29126 @code{-var-update} reports all the changed varobjs in a tuple named
29129 Each item in the change list is itself a tuple holding:
29133 The name of the varobj.
29136 If values were requested for this update, then this field will be
29137 present and will hold the value of the varobj.
29140 @anchor{-var-update}
29141 This field is a string which may take one of three values:
29145 The variable object's current value is valid.
29148 The variable object does not currently hold a valid value but it may
29149 hold one in the future if its associated expression comes back into
29153 The variable object no longer holds a valid value.
29154 This can occur when the executable file being debugged has changed,
29155 either through recompilation or by using the @value{GDBN} @code{file}
29156 command. The front end should normally choose to delete these variable
29160 In the future new values may be added to this list so the front should
29161 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
29164 This is only present if the varobj is still valid. If the type
29165 changed, then this will be the string @samp{true}; otherwise it will
29168 When a varobj's type changes, its children are also likely to have
29169 become incorrect. Therefore, the varobj's children are automatically
29170 deleted when this attribute is @samp{true}. Also, the varobj's update
29171 range, when set using the @code{-var-set-update-range} command, is
29175 If the varobj's type changed, then this field will be present and will
29178 @item new_num_children
29179 For a dynamic varobj, if the number of children changed, or if the
29180 type changed, this will be the new number of children.
29182 The @samp{numchild} field in other varobj responses is generally not
29183 valid for a dynamic varobj -- it will show the number of children that
29184 @value{GDBN} knows about, but because dynamic varobjs lazily
29185 instantiate their children, this will not reflect the number of
29186 children which may be available.
29188 The @samp{new_num_children} attribute only reports changes to the
29189 number of children known by @value{GDBN}. This is the only way to
29190 detect whether an update has removed children (which necessarily can
29191 only happen at the end of the update range).
29194 The display hint, if any.
29197 This is an integer value, which will be 1 if there are more children
29198 available outside the varobj's update range.
29201 This attribute will be present and have the value @samp{1} if the
29202 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29203 then this attribute will not be present.
29206 If new children were added to a dynamic varobj within the selected
29207 update range (as set by @code{-var-set-update-range}), then they will
29208 be listed in this attribute.
29211 @subsubheading Example
29218 -var-update --all-values var1
29219 ^done,changelist=[@{name="var1",value="3",in_scope="true",
29220 type_changed="false"@}]
29224 @subheading The @code{-var-set-frozen} Command
29225 @findex -var-set-frozen
29226 @anchor{-var-set-frozen}
29228 @subsubheading Synopsis
29231 -var-set-frozen @var{name} @var{flag}
29234 Set the frozenness flag on the variable object @var{name}. The
29235 @var{flag} parameter should be either @samp{1} to make the variable
29236 frozen or @samp{0} to make it unfrozen. If a variable object is
29237 frozen, then neither itself, nor any of its children, are
29238 implicitly updated by @code{-var-update} of
29239 a parent variable or by @code{-var-update *}. Only
29240 @code{-var-update} of the variable itself will update its value and
29241 values of its children. After a variable object is unfrozen, it is
29242 implicitly updated by all subsequent @code{-var-update} operations.
29243 Unfreezing a variable does not update it, only subsequent
29244 @code{-var-update} does.
29246 @subsubheading Example
29250 -var-set-frozen V 1
29255 @subheading The @code{-var-set-update-range} command
29256 @findex -var-set-update-range
29257 @anchor{-var-set-update-range}
29259 @subsubheading Synopsis
29262 -var-set-update-range @var{name} @var{from} @var{to}
29265 Set the range of children to be returned by future invocations of
29266 @code{-var-update}.
29268 @var{from} and @var{to} indicate the range of children to report. If
29269 @var{from} or @var{to} is less than zero, the range is reset and all
29270 children will be reported. Otherwise, children starting at @var{from}
29271 (zero-based) and up to and excluding @var{to} will be reported.
29273 @subsubheading Example
29277 -var-set-update-range V 1 2
29281 @subheading The @code{-var-set-visualizer} command
29282 @findex -var-set-visualizer
29283 @anchor{-var-set-visualizer}
29285 @subsubheading Synopsis
29288 -var-set-visualizer @var{name} @var{visualizer}
29291 Set a visualizer for the variable object @var{name}.
29293 @var{visualizer} is the visualizer to use. The special value
29294 @samp{None} means to disable any visualizer in use.
29296 If not @samp{None}, @var{visualizer} must be a Python expression.
29297 This expression must evaluate to a callable object which accepts a
29298 single argument. @value{GDBN} will call this object with the value of
29299 the varobj @var{name} as an argument (this is done so that the same
29300 Python pretty-printing code can be used for both the CLI and MI).
29301 When called, this object must return an object which conforms to the
29302 pretty-printing interface (@pxref{Pretty Printing API}).
29304 The pre-defined function @code{gdb.default_visualizer} may be used to
29305 select a visualizer by following the built-in process
29306 (@pxref{Selecting Pretty-Printers}). This is done automatically when
29307 a varobj is created, and so ordinarily is not needed.
29309 This feature is only available if Python support is enabled. The MI
29310 command @code{-list-features} (@pxref{GDB/MI Support Commands})
29311 can be used to check this.
29313 @subsubheading Example
29315 Resetting the visualizer:
29319 -var-set-visualizer V None
29323 Reselecting the default (type-based) visualizer:
29327 -var-set-visualizer V gdb.default_visualizer
29331 Suppose @code{SomeClass} is a visualizer class. A lambda expression
29332 can be used to instantiate this class for a varobj:
29336 -var-set-visualizer V "lambda val: SomeClass()"
29340 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29341 @node GDB/MI Data Manipulation
29342 @section @sc{gdb/mi} Data Manipulation
29344 @cindex data manipulation, in @sc{gdb/mi}
29345 @cindex @sc{gdb/mi}, data manipulation
29346 This section describes the @sc{gdb/mi} commands that manipulate data:
29347 examine memory and registers, evaluate expressions, etc.
29349 @c REMOVED FROM THE INTERFACE.
29350 @c @subheading -data-assign
29351 @c Change the value of a program variable. Plenty of side effects.
29352 @c @subsubheading GDB Command
29354 @c @subsubheading Example
29357 @subheading The @code{-data-disassemble} Command
29358 @findex -data-disassemble
29360 @subsubheading Synopsis
29364 [ -s @var{start-addr} -e @var{end-addr} ]
29365 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
29373 @item @var{start-addr}
29374 is the beginning address (or @code{$pc})
29375 @item @var{end-addr}
29377 @item @var{filename}
29378 is the name of the file to disassemble
29379 @item @var{linenum}
29380 is the line number to disassemble around
29382 is the number of disassembly lines to be produced. If it is -1,
29383 the whole function will be disassembled, in case no @var{end-addr} is
29384 specified. If @var{end-addr} is specified as a non-zero value, and
29385 @var{lines} is lower than the number of disassembly lines between
29386 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
29387 displayed; if @var{lines} is higher than the number of lines between
29388 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
29391 is either 0 (meaning only disassembly), 1 (meaning mixed source and
29392 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
29393 mixed source and disassembly with raw opcodes).
29396 @subsubheading Result
29398 The result of the @code{-data-disassemble} command will be a list named
29399 @samp{asm_insns}, the contents of this list depend on the @var{mode}
29400 used with the @code{-data-disassemble} command.
29402 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
29407 The address at which this instruction was disassembled.
29410 The name of the function this instruction is within.
29413 The decimal offset in bytes from the start of @samp{func-name}.
29416 The text disassembly for this @samp{address}.
29419 This field is only present for mode 2. This contains the raw opcode
29420 bytes for the @samp{inst} field.
29424 For modes 1 and 3 the @samp{asm_insns} list contains tuples named
29425 @samp{src_and_asm_line}, each of which has the following fields:
29429 The line number within @samp{file}.
29432 The file name from the compilation unit. This might be an absolute
29433 file name or a relative file name depending on the compile command
29437 Absolute file name of @samp{file}. It is converted to a canonical form
29438 using the source file search path
29439 (@pxref{Source Path, ,Specifying Source Directories})
29440 and after resolving all the symbolic links.
29442 If the source file is not found this field will contain the path as
29443 present in the debug information.
29445 @item line_asm_insn
29446 This is a list of tuples containing the disassembly for @samp{line} in
29447 @samp{file}. The fields of each tuple are the same as for
29448 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
29449 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
29454 Note that whatever included in the @samp{inst} field, is not
29455 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
29458 @subsubheading @value{GDBN} Command
29460 The corresponding @value{GDBN} command is @samp{disassemble}.
29462 @subsubheading Example
29464 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
29468 -data-disassemble -s $pc -e "$pc + 20" -- 0
29471 @{address="0x000107c0",func-name="main",offset="4",
29472 inst="mov 2, %o0"@},
29473 @{address="0x000107c4",func-name="main",offset="8",
29474 inst="sethi %hi(0x11800), %o2"@},
29475 @{address="0x000107c8",func-name="main",offset="12",
29476 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
29477 @{address="0x000107cc",func-name="main",offset="16",
29478 inst="sethi %hi(0x11800), %o2"@},
29479 @{address="0x000107d0",func-name="main",offset="20",
29480 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
29484 Disassemble the whole @code{main} function. Line 32 is part of
29488 -data-disassemble -f basics.c -l 32 -- 0
29490 @{address="0x000107bc",func-name="main",offset="0",
29491 inst="save %sp, -112, %sp"@},
29492 @{address="0x000107c0",func-name="main",offset="4",
29493 inst="mov 2, %o0"@},
29494 @{address="0x000107c4",func-name="main",offset="8",
29495 inst="sethi %hi(0x11800), %o2"@},
29497 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
29498 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
29502 Disassemble 3 instructions from the start of @code{main}:
29506 -data-disassemble -f basics.c -l 32 -n 3 -- 0
29508 @{address="0x000107bc",func-name="main",offset="0",
29509 inst="save %sp, -112, %sp"@},
29510 @{address="0x000107c0",func-name="main",offset="4",
29511 inst="mov 2, %o0"@},
29512 @{address="0x000107c4",func-name="main",offset="8",
29513 inst="sethi %hi(0x11800), %o2"@}]
29517 Disassemble 3 instructions from the start of @code{main} in mixed mode:
29521 -data-disassemble -f basics.c -l 32 -n 3 -- 1
29523 src_and_asm_line=@{line="31",
29524 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
29525 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
29526 line_asm_insn=[@{address="0x000107bc",
29527 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
29528 src_and_asm_line=@{line="32",
29529 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
29530 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
29531 line_asm_insn=[@{address="0x000107c0",
29532 func-name="main",offset="4",inst="mov 2, %o0"@},
29533 @{address="0x000107c4",func-name="main",offset="8",
29534 inst="sethi %hi(0x11800), %o2"@}]@}]
29539 @subheading The @code{-data-evaluate-expression} Command
29540 @findex -data-evaluate-expression
29542 @subsubheading Synopsis
29545 -data-evaluate-expression @var{expr}
29548 Evaluate @var{expr} as an expression. The expression could contain an
29549 inferior function call. The function call will execute synchronously.
29550 If the expression contains spaces, it must be enclosed in double quotes.
29552 @subsubheading @value{GDBN} Command
29554 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
29555 @samp{call}. In @code{gdbtk} only, there's a corresponding
29556 @samp{gdb_eval} command.
29558 @subsubheading Example
29560 In the following example, the numbers that precede the commands are the
29561 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
29562 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
29566 211-data-evaluate-expression A
29569 311-data-evaluate-expression &A
29570 311^done,value="0xefffeb7c"
29572 411-data-evaluate-expression A+3
29575 511-data-evaluate-expression "A + 3"
29581 @subheading The @code{-data-list-changed-registers} Command
29582 @findex -data-list-changed-registers
29584 @subsubheading Synopsis
29587 -data-list-changed-registers
29590 Display a list of the registers that have changed.
29592 @subsubheading @value{GDBN} Command
29594 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
29595 has the corresponding command @samp{gdb_changed_register_list}.
29597 @subsubheading Example
29599 On a PPC MBX board:
29607 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
29608 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
29611 -data-list-changed-registers
29612 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
29613 "10","11","13","14","15","16","17","18","19","20","21","22","23",
29614 "24","25","26","27","28","30","31","64","65","66","67","69"]
29619 @subheading The @code{-data-list-register-names} Command
29620 @findex -data-list-register-names
29622 @subsubheading Synopsis
29625 -data-list-register-names [ ( @var{regno} )+ ]
29628 Show a list of register names for the current target. If no arguments
29629 are given, it shows a list of the names of all the registers. If
29630 integer numbers are given as arguments, it will print a list of the
29631 names of the registers corresponding to the arguments. To ensure
29632 consistency between a register name and its number, the output list may
29633 include empty register names.
29635 @subsubheading @value{GDBN} Command
29637 @value{GDBN} does not have a command which corresponds to
29638 @samp{-data-list-register-names}. In @code{gdbtk} there is a
29639 corresponding command @samp{gdb_regnames}.
29641 @subsubheading Example
29643 For the PPC MBX board:
29646 -data-list-register-names
29647 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
29648 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
29649 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
29650 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
29651 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
29652 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
29653 "", "pc","ps","cr","lr","ctr","xer"]
29655 -data-list-register-names 1 2 3
29656 ^done,register-names=["r1","r2","r3"]
29660 @subheading The @code{-data-list-register-values} Command
29661 @findex -data-list-register-values
29663 @subsubheading Synopsis
29666 -data-list-register-values
29667 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
29670 Display the registers' contents. The format according to which the
29671 registers' contents are to be returned is given by @var{fmt}, followed
29672 by an optional list of numbers specifying the registers to display. A
29673 missing list of numbers indicates that the contents of all the
29674 registers must be returned. The @code{--skip-unavailable} option
29675 indicates that only the available registers are to be returned.
29677 Allowed formats for @var{fmt} are:
29694 @subsubheading @value{GDBN} Command
29696 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
29697 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
29699 @subsubheading Example
29701 For a PPC MBX board (note: line breaks are for readability only, they
29702 don't appear in the actual output):
29706 -data-list-register-values r 64 65
29707 ^done,register-values=[@{number="64",value="0xfe00a300"@},
29708 @{number="65",value="0x00029002"@}]
29710 -data-list-register-values x
29711 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
29712 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
29713 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
29714 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
29715 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
29716 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
29717 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
29718 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
29719 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
29720 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
29721 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
29722 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
29723 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
29724 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
29725 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
29726 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
29727 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
29728 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
29729 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
29730 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
29731 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
29732 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
29733 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
29734 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
29735 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
29736 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
29737 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
29738 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
29739 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
29740 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
29741 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
29742 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
29743 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
29744 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
29745 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
29746 @{number="69",value="0x20002b03"@}]
29751 @subheading The @code{-data-read-memory} Command
29752 @findex -data-read-memory
29754 This command is deprecated, use @code{-data-read-memory-bytes} instead.
29756 @subsubheading Synopsis
29759 -data-read-memory [ -o @var{byte-offset} ]
29760 @var{address} @var{word-format} @var{word-size}
29761 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
29768 @item @var{address}
29769 An expression specifying the address of the first memory word to be
29770 read. Complex expressions containing embedded white space should be
29771 quoted using the C convention.
29773 @item @var{word-format}
29774 The format to be used to print the memory words. The notation is the
29775 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
29778 @item @var{word-size}
29779 The size of each memory word in bytes.
29781 @item @var{nr-rows}
29782 The number of rows in the output table.
29784 @item @var{nr-cols}
29785 The number of columns in the output table.
29788 If present, indicates that each row should include an @sc{ascii} dump. The
29789 value of @var{aschar} is used as a padding character when a byte is not a
29790 member of the printable @sc{ascii} character set (printable @sc{ascii}
29791 characters are those whose code is between 32 and 126, inclusively).
29793 @item @var{byte-offset}
29794 An offset to add to the @var{address} before fetching memory.
29797 This command displays memory contents as a table of @var{nr-rows} by
29798 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
29799 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
29800 (returned as @samp{total-bytes}). Should less than the requested number
29801 of bytes be returned by the target, the missing words are identified
29802 using @samp{N/A}. The number of bytes read from the target is returned
29803 in @samp{nr-bytes} and the starting address used to read memory in
29806 The address of the next/previous row or page is available in
29807 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
29810 @subsubheading @value{GDBN} Command
29812 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
29813 @samp{gdb_get_mem} memory read command.
29815 @subsubheading Example
29817 Read six bytes of memory starting at @code{bytes+6} but then offset by
29818 @code{-6} bytes. Format as three rows of two columns. One byte per
29819 word. Display each word in hex.
29823 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
29824 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
29825 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
29826 prev-page="0x0000138a",memory=[
29827 @{addr="0x00001390",data=["0x00","0x01"]@},
29828 @{addr="0x00001392",data=["0x02","0x03"]@},
29829 @{addr="0x00001394",data=["0x04","0x05"]@}]
29833 Read two bytes of memory starting at address @code{shorts + 64} and
29834 display as a single word formatted in decimal.
29838 5-data-read-memory shorts+64 d 2 1 1
29839 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
29840 next-row="0x00001512",prev-row="0x0000150e",
29841 next-page="0x00001512",prev-page="0x0000150e",memory=[
29842 @{addr="0x00001510",data=["128"]@}]
29846 Read thirty two bytes of memory starting at @code{bytes+16} and format
29847 as eight rows of four columns. Include a string encoding with @samp{x}
29848 used as the non-printable character.
29852 4-data-read-memory bytes+16 x 1 8 4 x
29853 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
29854 next-row="0x000013c0",prev-row="0x0000139c",
29855 next-page="0x000013c0",prev-page="0x00001380",memory=[
29856 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
29857 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
29858 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
29859 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
29860 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
29861 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
29862 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
29863 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
29867 @subheading The @code{-data-read-memory-bytes} Command
29868 @findex -data-read-memory-bytes
29870 @subsubheading Synopsis
29873 -data-read-memory-bytes [ -o @var{byte-offset} ]
29874 @var{address} @var{count}
29881 @item @var{address}
29882 An expression specifying the address of the first memory word to be
29883 read. Complex expressions containing embedded white space should be
29884 quoted using the C convention.
29887 The number of bytes to read. This should be an integer literal.
29889 @item @var{byte-offset}
29890 The offsets in bytes relative to @var{address} at which to start
29891 reading. This should be an integer literal. This option is provided
29892 so that a frontend is not required to first evaluate address and then
29893 perform address arithmetics itself.
29897 This command attempts to read all accessible memory regions in the
29898 specified range. First, all regions marked as unreadable in the memory
29899 map (if one is defined) will be skipped. @xref{Memory Region
29900 Attributes}. Second, @value{GDBN} will attempt to read the remaining
29901 regions. For each one, if reading full region results in an errors,
29902 @value{GDBN} will try to read a subset of the region.
29904 In general, every single byte in the region may be readable or not,
29905 and the only way to read every readable byte is to try a read at
29906 every address, which is not practical. Therefore, @value{GDBN} will
29907 attempt to read all accessible bytes at either beginning or the end
29908 of the region, using a binary division scheme. This heuristic works
29909 well for reading accross a memory map boundary. Note that if a region
29910 has a readable range that is neither at the beginning or the end,
29911 @value{GDBN} will not read it.
29913 The result record (@pxref{GDB/MI Result Records}) that is output of
29914 the command includes a field named @samp{memory} whose content is a
29915 list of tuples. Each tuple represent a successfully read memory block
29916 and has the following fields:
29920 The start address of the memory block, as hexadecimal literal.
29923 The end address of the memory block, as hexadecimal literal.
29926 The offset of the memory block, as hexadecimal literal, relative to
29927 the start address passed to @code{-data-read-memory-bytes}.
29930 The contents of the memory block, in hex.
29936 @subsubheading @value{GDBN} Command
29938 The corresponding @value{GDBN} command is @samp{x}.
29940 @subsubheading Example
29944 -data-read-memory-bytes &a 10
29945 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
29947 contents="01000000020000000300"@}]
29952 @subheading The @code{-data-write-memory-bytes} Command
29953 @findex -data-write-memory-bytes
29955 @subsubheading Synopsis
29958 -data-write-memory-bytes @var{address} @var{contents}
29959 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
29966 @item @var{address}
29967 An expression specifying the address of the first memory word to be
29968 read. Complex expressions containing embedded white space should be
29969 quoted using the C convention.
29971 @item @var{contents}
29972 The hex-encoded bytes to write.
29975 Optional argument indicating the number of bytes to be written. If @var{count}
29976 is greater than @var{contents}' length, @value{GDBN} will repeatedly
29977 write @var{contents} until it fills @var{count} bytes.
29981 @subsubheading @value{GDBN} Command
29983 There's no corresponding @value{GDBN} command.
29985 @subsubheading Example
29989 -data-write-memory-bytes &a "aabbccdd"
29996 -data-write-memory-bytes &a "aabbccdd" 16e
30001 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30002 @node GDB/MI Tracepoint Commands
30003 @section @sc{gdb/mi} Tracepoint Commands
30005 The commands defined in this section implement MI support for
30006 tracepoints. For detailed introduction, see @ref{Tracepoints}.
30008 @subheading The @code{-trace-find} Command
30009 @findex -trace-find
30011 @subsubheading Synopsis
30014 -trace-find @var{mode} [@var{parameters}@dots{}]
30017 Find a trace frame using criteria defined by @var{mode} and
30018 @var{parameters}. The following table lists permissible
30019 modes and their parameters. For details of operation, see @ref{tfind}.
30024 No parameters are required. Stops examining trace frames.
30027 An integer is required as parameter. Selects tracepoint frame with
30030 @item tracepoint-number
30031 An integer is required as parameter. Finds next
30032 trace frame that corresponds to tracepoint with the specified number.
30035 An address is required as parameter. Finds
30036 next trace frame that corresponds to any tracepoint at the specified
30039 @item pc-inside-range
30040 Two addresses are required as parameters. Finds next trace
30041 frame that corresponds to a tracepoint at an address inside the
30042 specified range. Both bounds are considered to be inside the range.
30044 @item pc-outside-range
30045 Two addresses are required as parameters. Finds
30046 next trace frame that corresponds to a tracepoint at an address outside
30047 the specified range. Both bounds are considered to be inside the range.
30050 Line specification is required as parameter. @xref{Specify Location}.
30051 Finds next trace frame that corresponds to a tracepoint at
30052 the specified location.
30056 If @samp{none} was passed as @var{mode}, the response does not
30057 have fields. Otherwise, the response may have the following fields:
30061 This field has either @samp{0} or @samp{1} as the value, depending
30062 on whether a matching tracepoint was found.
30065 The index of the found traceframe. This field is present iff
30066 the @samp{found} field has value of @samp{1}.
30069 The index of the found tracepoint. This field is present iff
30070 the @samp{found} field has value of @samp{1}.
30073 The information about the frame corresponding to the found trace
30074 frame. This field is present only if a trace frame was found.
30075 @xref{GDB/MI Frame Information}, for description of this field.
30079 @subsubheading @value{GDBN} Command
30081 The corresponding @value{GDBN} command is @samp{tfind}.
30083 @subheading -trace-define-variable
30084 @findex -trace-define-variable
30086 @subsubheading Synopsis
30089 -trace-define-variable @var{name} [ @var{value} ]
30092 Create trace variable @var{name} if it does not exist. If
30093 @var{value} is specified, sets the initial value of the specified
30094 trace variable to that value. Note that the @var{name} should start
30095 with the @samp{$} character.
30097 @subsubheading @value{GDBN} Command
30099 The corresponding @value{GDBN} command is @samp{tvariable}.
30101 @subheading The @code{-trace-frame-collected} Command
30102 @findex -trace-frame-collected
30104 @subsubheading Synopsis
30107 -trace-frame-collected
30108 [--var-print-values @var{var_pval}]
30109 [--comp-print-values @var{comp_pval}]
30110 [--registers-format @var{regformat}]
30111 [--memory-contents]
30114 This command returns the set of collected objects, register names,
30115 trace state variable names, memory ranges and computed expressions
30116 that have been collected at a particular trace frame. The optional
30117 parameters to the command affect the output format in different ways.
30118 See the output description table below for more details.
30120 The reported names can be used in the normal manner to create
30121 varobjs and inspect the objects themselves. The items returned by
30122 this command are categorized so that it is clear which is a variable,
30123 which is a register, which is a trace state variable, which is a
30124 memory range and which is a computed expression.
30126 For instance, if the actions were
30128 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
30129 collect *(int*)0xaf02bef0@@40
30133 the object collected in its entirety would be @code{myVar}. The
30134 object @code{myArray} would be partially collected, because only the
30135 element at index @code{myIndex} would be collected. The remaining
30136 objects would be computed expressions.
30138 An example output would be:
30142 -trace-frame-collected
30144 explicit-variables=[@{name="myVar",value="1"@}],
30145 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
30146 @{name="myObj.field",value="0"@},
30147 @{name="myPtr->field",value="1"@},
30148 @{name="myCount + 2",value="3"@},
30149 @{name="$tvar1 + 1",value="43970027"@}],
30150 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
30151 @{number="1",value="0x0"@},
30152 @{number="2",value="0x4"@},
30154 @{number="125",value="0x0"@}],
30155 tvars=[@{name="$tvar1",current="43970026"@}],
30156 memory=[@{address="0x0000000000602264",length="4"@},
30157 @{address="0x0000000000615bc0",length="4"@}]
30164 @item explicit-variables
30165 The set of objects that have been collected in their entirety (as
30166 opposed to collecting just a few elements of an array or a few struct
30167 members). For each object, its name and value are printed.
30168 The @code{--var-print-values} option affects how or whether the value
30169 field is output. If @var{var_pval} is 0, then print only the names;
30170 if it is 1, print also their values; and if it is 2, print the name,
30171 type and value for simple data types, and the name and type for
30172 arrays, structures and unions.
30174 @item computed-expressions
30175 The set of computed expressions that have been collected at the
30176 current trace frame. The @code{--comp-print-values} option affects
30177 this set like the @code{--var-print-values} option affects the
30178 @code{explicit-variables} set. See above.
30181 The registers that have been collected at the current trace frame.
30182 For each register collected, the name and current value are returned.
30183 The value is formatted according to the @code{--registers-format}
30184 option. See the @command{-data-list-register-values} command for a
30185 list of the allowed formats. The default is @samp{x}.
30188 The trace state variables that have been collected at the current
30189 trace frame. For each trace state variable collected, the name and
30190 current value are returned.
30193 The set of memory ranges that have been collected at the current trace
30194 frame. Its content is a list of tuples. Each tuple represents a
30195 collected memory range and has the following fields:
30199 The start address of the memory range, as hexadecimal literal.
30202 The length of the memory range, as decimal literal.
30205 The contents of the memory block, in hex. This field is only present
30206 if the @code{--memory-contents} option is specified.
30212 @subsubheading @value{GDBN} Command
30214 There is no corresponding @value{GDBN} command.
30216 @subsubheading Example
30218 @subheading -trace-list-variables
30219 @findex -trace-list-variables
30221 @subsubheading Synopsis
30224 -trace-list-variables
30227 Return a table of all defined trace variables. Each element of the
30228 table has the following fields:
30232 The name of the trace variable. This field is always present.
30235 The initial value. This is a 64-bit signed integer. This
30236 field is always present.
30239 The value the trace variable has at the moment. This is a 64-bit
30240 signed integer. This field is absent iff current value is
30241 not defined, for example if the trace was never run, or is
30246 @subsubheading @value{GDBN} Command
30248 The corresponding @value{GDBN} command is @samp{tvariables}.
30250 @subsubheading Example
30254 -trace-list-variables
30255 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
30256 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
30257 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
30258 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
30259 body=[variable=@{name="$trace_timestamp",initial="0"@}
30260 variable=@{name="$foo",initial="10",current="15"@}]@}
30264 @subheading -trace-save
30265 @findex -trace-save
30267 @subsubheading Synopsis
30270 -trace-save [-r ] @var{filename}
30273 Saves the collected trace data to @var{filename}. Without the
30274 @samp{-r} option, the data is downloaded from the target and saved
30275 in a local file. With the @samp{-r} option the target is asked
30276 to perform the save.
30278 @subsubheading @value{GDBN} Command
30280 The corresponding @value{GDBN} command is @samp{tsave}.
30283 @subheading -trace-start
30284 @findex -trace-start
30286 @subsubheading Synopsis
30292 Starts a tracing experiments. The result of this command does not
30295 @subsubheading @value{GDBN} Command
30297 The corresponding @value{GDBN} command is @samp{tstart}.
30299 @subheading -trace-status
30300 @findex -trace-status
30302 @subsubheading Synopsis
30308 Obtains the status of a tracing experiment. The result may include
30309 the following fields:
30314 May have a value of either @samp{0}, when no tracing operations are
30315 supported, @samp{1}, when all tracing operations are supported, or
30316 @samp{file} when examining trace file. In the latter case, examining
30317 of trace frame is possible but new tracing experiement cannot be
30318 started. This field is always present.
30321 May have a value of either @samp{0} or @samp{1} depending on whether
30322 tracing experiement is in progress on target. This field is present
30323 if @samp{supported} field is not @samp{0}.
30326 Report the reason why the tracing was stopped last time. This field
30327 may be absent iff tracing was never stopped on target yet. The
30328 value of @samp{request} means the tracing was stopped as result of
30329 the @code{-trace-stop} command. The value of @samp{overflow} means
30330 the tracing buffer is full. The value of @samp{disconnection} means
30331 tracing was automatically stopped when @value{GDBN} has disconnected.
30332 The value of @samp{passcount} means tracing was stopped when a
30333 tracepoint was passed a maximal number of times for that tracepoint.
30334 This field is present if @samp{supported} field is not @samp{0}.
30336 @item stopping-tracepoint
30337 The number of tracepoint whose passcount as exceeded. This field is
30338 present iff the @samp{stop-reason} field has the value of
30342 @itemx frames-created
30343 The @samp{frames} field is a count of the total number of trace frames
30344 in the trace buffer, while @samp{frames-created} is the total created
30345 during the run, including ones that were discarded, such as when a
30346 circular trace buffer filled up. Both fields are optional.
30350 These fields tell the current size of the tracing buffer and the
30351 remaining space. These fields are optional.
30354 The value of the circular trace buffer flag. @code{1} means that the
30355 trace buffer is circular and old trace frames will be discarded if
30356 necessary to make room, @code{0} means that the trace buffer is linear
30360 The value of the disconnected tracing flag. @code{1} means that
30361 tracing will continue after @value{GDBN} disconnects, @code{0} means
30362 that the trace run will stop.
30365 The filename of the trace file being examined. This field is
30366 optional, and only present when examining a trace file.
30370 @subsubheading @value{GDBN} Command
30372 The corresponding @value{GDBN} command is @samp{tstatus}.
30374 @subheading -trace-stop
30375 @findex -trace-stop
30377 @subsubheading Synopsis
30383 Stops a tracing experiment. The result of this command has the same
30384 fields as @code{-trace-status}, except that the @samp{supported} and
30385 @samp{running} fields are not output.
30387 @subsubheading @value{GDBN} Command
30389 The corresponding @value{GDBN} command is @samp{tstop}.
30392 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30393 @node GDB/MI Symbol Query
30394 @section @sc{gdb/mi} Symbol Query Commands
30398 @subheading The @code{-symbol-info-address} Command
30399 @findex -symbol-info-address
30401 @subsubheading Synopsis
30404 -symbol-info-address @var{symbol}
30407 Describe where @var{symbol} is stored.
30409 @subsubheading @value{GDBN} Command
30411 The corresponding @value{GDBN} command is @samp{info address}.
30413 @subsubheading Example
30417 @subheading The @code{-symbol-info-file} Command
30418 @findex -symbol-info-file
30420 @subsubheading Synopsis
30426 Show the file for the symbol.
30428 @subsubheading @value{GDBN} Command
30430 There's no equivalent @value{GDBN} command. @code{gdbtk} has
30431 @samp{gdb_find_file}.
30433 @subsubheading Example
30437 @subheading The @code{-symbol-info-function} Command
30438 @findex -symbol-info-function
30440 @subsubheading Synopsis
30443 -symbol-info-function
30446 Show which function the symbol lives in.
30448 @subsubheading @value{GDBN} Command
30450 @samp{gdb_get_function} in @code{gdbtk}.
30452 @subsubheading Example
30456 @subheading The @code{-symbol-info-line} Command
30457 @findex -symbol-info-line
30459 @subsubheading Synopsis
30465 Show the core addresses of the code for a source line.
30467 @subsubheading @value{GDBN} Command
30469 The corresponding @value{GDBN} command is @samp{info line}.
30470 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
30472 @subsubheading Example
30476 @subheading The @code{-symbol-info-symbol} Command
30477 @findex -symbol-info-symbol
30479 @subsubheading Synopsis
30482 -symbol-info-symbol @var{addr}
30485 Describe what symbol is at location @var{addr}.
30487 @subsubheading @value{GDBN} Command
30489 The corresponding @value{GDBN} command is @samp{info symbol}.
30491 @subsubheading Example
30495 @subheading The @code{-symbol-list-functions} Command
30496 @findex -symbol-list-functions
30498 @subsubheading Synopsis
30501 -symbol-list-functions
30504 List the functions in the executable.
30506 @subsubheading @value{GDBN} Command
30508 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
30509 @samp{gdb_search} in @code{gdbtk}.
30511 @subsubheading Example
30516 @subheading The @code{-symbol-list-lines} Command
30517 @findex -symbol-list-lines
30519 @subsubheading Synopsis
30522 -symbol-list-lines @var{filename}
30525 Print the list of lines that contain code and their associated program
30526 addresses for the given source filename. The entries are sorted in
30527 ascending PC order.
30529 @subsubheading @value{GDBN} Command
30531 There is no corresponding @value{GDBN} command.
30533 @subsubheading Example
30536 -symbol-list-lines basics.c
30537 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
30543 @subheading The @code{-symbol-list-types} Command
30544 @findex -symbol-list-types
30546 @subsubheading Synopsis
30552 List all the type names.
30554 @subsubheading @value{GDBN} Command
30556 The corresponding commands are @samp{info types} in @value{GDBN},
30557 @samp{gdb_search} in @code{gdbtk}.
30559 @subsubheading Example
30563 @subheading The @code{-symbol-list-variables} Command
30564 @findex -symbol-list-variables
30566 @subsubheading Synopsis
30569 -symbol-list-variables
30572 List all the global and static variable names.
30574 @subsubheading @value{GDBN} Command
30576 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
30578 @subsubheading Example
30582 @subheading The @code{-symbol-locate} Command
30583 @findex -symbol-locate
30585 @subsubheading Synopsis
30591 @subsubheading @value{GDBN} Command
30593 @samp{gdb_loc} in @code{gdbtk}.
30595 @subsubheading Example
30599 @subheading The @code{-symbol-type} Command
30600 @findex -symbol-type
30602 @subsubheading Synopsis
30605 -symbol-type @var{variable}
30608 Show type of @var{variable}.
30610 @subsubheading @value{GDBN} Command
30612 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
30613 @samp{gdb_obj_variable}.
30615 @subsubheading Example
30620 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30621 @node GDB/MI File Commands
30622 @section @sc{gdb/mi} File Commands
30624 This section describes the GDB/MI commands to specify executable file names
30625 and to read in and obtain symbol table information.
30627 @subheading The @code{-file-exec-and-symbols} Command
30628 @findex -file-exec-and-symbols
30630 @subsubheading Synopsis
30633 -file-exec-and-symbols @var{file}
30636 Specify the executable file to be debugged. This file is the one from
30637 which the symbol table is also read. If no file is specified, the
30638 command clears the executable and symbol information. If breakpoints
30639 are set when using this command with no arguments, @value{GDBN} will produce
30640 error messages. Otherwise, no output is produced, except a completion
30643 @subsubheading @value{GDBN} Command
30645 The corresponding @value{GDBN} command is @samp{file}.
30647 @subsubheading Example
30651 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30657 @subheading The @code{-file-exec-file} Command
30658 @findex -file-exec-file
30660 @subsubheading Synopsis
30663 -file-exec-file @var{file}
30666 Specify the executable file to be debugged. Unlike
30667 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
30668 from this file. If used without argument, @value{GDBN} clears the information
30669 about the executable file. No output is produced, except a completion
30672 @subsubheading @value{GDBN} Command
30674 The corresponding @value{GDBN} command is @samp{exec-file}.
30676 @subsubheading Example
30680 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30687 @subheading The @code{-file-list-exec-sections} Command
30688 @findex -file-list-exec-sections
30690 @subsubheading Synopsis
30693 -file-list-exec-sections
30696 List the sections of the current executable file.
30698 @subsubheading @value{GDBN} Command
30700 The @value{GDBN} command @samp{info file} shows, among the rest, the same
30701 information as this command. @code{gdbtk} has a corresponding command
30702 @samp{gdb_load_info}.
30704 @subsubheading Example
30709 @subheading The @code{-file-list-exec-source-file} Command
30710 @findex -file-list-exec-source-file
30712 @subsubheading Synopsis
30715 -file-list-exec-source-file
30718 List the line number, the current source file, and the absolute path
30719 to the current source file for the current executable. The macro
30720 information field has a value of @samp{1} or @samp{0} depending on
30721 whether or not the file includes preprocessor macro information.
30723 @subsubheading @value{GDBN} Command
30725 The @value{GDBN} equivalent is @samp{info source}
30727 @subsubheading Example
30731 123-file-list-exec-source-file
30732 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
30737 @subheading The @code{-file-list-exec-source-files} Command
30738 @findex -file-list-exec-source-files
30740 @subsubheading Synopsis
30743 -file-list-exec-source-files
30746 List the source files for the current executable.
30748 It will always output both the filename and fullname (absolute file
30749 name) of a source file.
30751 @subsubheading @value{GDBN} Command
30753 The @value{GDBN} equivalent is @samp{info sources}.
30754 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
30756 @subsubheading Example
30759 -file-list-exec-source-files
30761 @{file=foo.c,fullname=/home/foo.c@},
30762 @{file=/home/bar.c,fullname=/home/bar.c@},
30763 @{file=gdb_could_not_find_fullpath.c@}]
30768 @subheading The @code{-file-list-shared-libraries} Command
30769 @findex -file-list-shared-libraries
30771 @subsubheading Synopsis
30774 -file-list-shared-libraries
30777 List the shared libraries in the program.
30779 @subsubheading @value{GDBN} Command
30781 The corresponding @value{GDBN} command is @samp{info shared}.
30783 @subsubheading Example
30787 @subheading The @code{-file-list-symbol-files} Command
30788 @findex -file-list-symbol-files
30790 @subsubheading Synopsis
30793 -file-list-symbol-files
30798 @subsubheading @value{GDBN} Command
30800 The corresponding @value{GDBN} command is @samp{info file} (part of it).
30802 @subsubheading Example
30807 @subheading The @code{-file-symbol-file} Command
30808 @findex -file-symbol-file
30810 @subsubheading Synopsis
30813 -file-symbol-file @var{file}
30816 Read symbol table info from the specified @var{file} argument. When
30817 used without arguments, clears @value{GDBN}'s symbol table info. No output is
30818 produced, except for a completion notification.
30820 @subsubheading @value{GDBN} Command
30822 The corresponding @value{GDBN} command is @samp{symbol-file}.
30824 @subsubheading Example
30828 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30834 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30835 @node GDB/MI Memory Overlay Commands
30836 @section @sc{gdb/mi} Memory Overlay Commands
30838 The memory overlay commands are not implemented.
30840 @c @subheading -overlay-auto
30842 @c @subheading -overlay-list-mapping-state
30844 @c @subheading -overlay-list-overlays
30846 @c @subheading -overlay-map
30848 @c @subheading -overlay-off
30850 @c @subheading -overlay-on
30852 @c @subheading -overlay-unmap
30854 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30855 @node GDB/MI Signal Handling Commands
30856 @section @sc{gdb/mi} Signal Handling Commands
30858 Signal handling commands are not implemented.
30860 @c @subheading -signal-handle
30862 @c @subheading -signal-list-handle-actions
30864 @c @subheading -signal-list-signal-types
30868 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30869 @node GDB/MI Target Manipulation
30870 @section @sc{gdb/mi} Target Manipulation Commands
30873 @subheading The @code{-target-attach} Command
30874 @findex -target-attach
30876 @subsubheading Synopsis
30879 -target-attach @var{pid} | @var{gid} | @var{file}
30882 Attach to a process @var{pid} or a file @var{file} outside of
30883 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
30884 group, the id previously returned by
30885 @samp{-list-thread-groups --available} must be used.
30887 @subsubheading @value{GDBN} Command
30889 The corresponding @value{GDBN} command is @samp{attach}.
30891 @subsubheading Example
30895 =thread-created,id="1"
30896 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
30902 @subheading The @code{-target-compare-sections} Command
30903 @findex -target-compare-sections
30905 @subsubheading Synopsis
30908 -target-compare-sections [ @var{section} ]
30911 Compare data of section @var{section} on target to the exec file.
30912 Without the argument, all sections are compared.
30914 @subsubheading @value{GDBN} Command
30916 The @value{GDBN} equivalent is @samp{compare-sections}.
30918 @subsubheading Example
30923 @subheading The @code{-target-detach} Command
30924 @findex -target-detach
30926 @subsubheading Synopsis
30929 -target-detach [ @var{pid} | @var{gid} ]
30932 Detach from the remote target which normally resumes its execution.
30933 If either @var{pid} or @var{gid} is specified, detaches from either
30934 the specified process, or specified thread group. There's no output.
30936 @subsubheading @value{GDBN} Command
30938 The corresponding @value{GDBN} command is @samp{detach}.
30940 @subsubheading Example
30950 @subheading The @code{-target-disconnect} Command
30951 @findex -target-disconnect
30953 @subsubheading Synopsis
30959 Disconnect from the remote target. There's no output and the target is
30960 generally not resumed.
30962 @subsubheading @value{GDBN} Command
30964 The corresponding @value{GDBN} command is @samp{disconnect}.
30966 @subsubheading Example
30976 @subheading The @code{-target-download} Command
30977 @findex -target-download
30979 @subsubheading Synopsis
30985 Loads the executable onto the remote target.
30986 It prints out an update message every half second, which includes the fields:
30990 The name of the section.
30992 The size of what has been sent so far for that section.
30994 The size of the section.
30996 The total size of what was sent so far (the current and the previous sections).
30998 The size of the overall executable to download.
31002 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
31003 @sc{gdb/mi} Output Syntax}).
31005 In addition, it prints the name and size of the sections, as they are
31006 downloaded. These messages include the following fields:
31010 The name of the section.
31012 The size of the section.
31014 The size of the overall executable to download.
31018 At the end, a summary is printed.
31020 @subsubheading @value{GDBN} Command
31022 The corresponding @value{GDBN} command is @samp{load}.
31024 @subsubheading Example
31026 Note: each status message appears on a single line. Here the messages
31027 have been broken down so that they can fit onto a page.
31032 +download,@{section=".text",section-size="6668",total-size="9880"@}
31033 +download,@{section=".text",section-sent="512",section-size="6668",
31034 total-sent="512",total-size="9880"@}
31035 +download,@{section=".text",section-sent="1024",section-size="6668",
31036 total-sent="1024",total-size="9880"@}
31037 +download,@{section=".text",section-sent="1536",section-size="6668",
31038 total-sent="1536",total-size="9880"@}
31039 +download,@{section=".text",section-sent="2048",section-size="6668",
31040 total-sent="2048",total-size="9880"@}
31041 +download,@{section=".text",section-sent="2560",section-size="6668",
31042 total-sent="2560",total-size="9880"@}
31043 +download,@{section=".text",section-sent="3072",section-size="6668",
31044 total-sent="3072",total-size="9880"@}
31045 +download,@{section=".text",section-sent="3584",section-size="6668",
31046 total-sent="3584",total-size="9880"@}
31047 +download,@{section=".text",section-sent="4096",section-size="6668",
31048 total-sent="4096",total-size="9880"@}
31049 +download,@{section=".text",section-sent="4608",section-size="6668",
31050 total-sent="4608",total-size="9880"@}
31051 +download,@{section=".text",section-sent="5120",section-size="6668",
31052 total-sent="5120",total-size="9880"@}
31053 +download,@{section=".text",section-sent="5632",section-size="6668",
31054 total-sent="5632",total-size="9880"@}
31055 +download,@{section=".text",section-sent="6144",section-size="6668",
31056 total-sent="6144",total-size="9880"@}
31057 +download,@{section=".text",section-sent="6656",section-size="6668",
31058 total-sent="6656",total-size="9880"@}
31059 +download,@{section=".init",section-size="28",total-size="9880"@}
31060 +download,@{section=".fini",section-size="28",total-size="9880"@}
31061 +download,@{section=".data",section-size="3156",total-size="9880"@}
31062 +download,@{section=".data",section-sent="512",section-size="3156",
31063 total-sent="7236",total-size="9880"@}
31064 +download,@{section=".data",section-sent="1024",section-size="3156",
31065 total-sent="7748",total-size="9880"@}
31066 +download,@{section=".data",section-sent="1536",section-size="3156",
31067 total-sent="8260",total-size="9880"@}
31068 +download,@{section=".data",section-sent="2048",section-size="3156",
31069 total-sent="8772",total-size="9880"@}
31070 +download,@{section=".data",section-sent="2560",section-size="3156",
31071 total-sent="9284",total-size="9880"@}
31072 +download,@{section=".data",section-sent="3072",section-size="3156",
31073 total-sent="9796",total-size="9880"@}
31074 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
31081 @subheading The @code{-target-exec-status} Command
31082 @findex -target-exec-status
31084 @subsubheading Synopsis
31087 -target-exec-status
31090 Provide information on the state of the target (whether it is running or
31091 not, for instance).
31093 @subsubheading @value{GDBN} Command
31095 There's no equivalent @value{GDBN} command.
31097 @subsubheading Example
31101 @subheading The @code{-target-list-available-targets} Command
31102 @findex -target-list-available-targets
31104 @subsubheading Synopsis
31107 -target-list-available-targets
31110 List the possible targets to connect to.
31112 @subsubheading @value{GDBN} Command
31114 The corresponding @value{GDBN} command is @samp{help target}.
31116 @subsubheading Example
31120 @subheading The @code{-target-list-current-targets} Command
31121 @findex -target-list-current-targets
31123 @subsubheading Synopsis
31126 -target-list-current-targets
31129 Describe the current target.
31131 @subsubheading @value{GDBN} Command
31133 The corresponding information is printed by @samp{info file} (among
31136 @subsubheading Example
31140 @subheading The @code{-target-list-parameters} Command
31141 @findex -target-list-parameters
31143 @subsubheading Synopsis
31146 -target-list-parameters
31152 @subsubheading @value{GDBN} Command
31156 @subsubheading Example
31160 @subheading The @code{-target-select} Command
31161 @findex -target-select
31163 @subsubheading Synopsis
31166 -target-select @var{type} @var{parameters @dots{}}
31169 Connect @value{GDBN} to the remote target. This command takes two args:
31173 The type of target, for instance @samp{remote}, etc.
31174 @item @var{parameters}
31175 Device names, host names and the like. @xref{Target Commands, ,
31176 Commands for Managing Targets}, for more details.
31179 The output is a connection notification, followed by the address at
31180 which the target program is, in the following form:
31183 ^connected,addr="@var{address}",func="@var{function name}",
31184 args=[@var{arg list}]
31187 @subsubheading @value{GDBN} Command
31189 The corresponding @value{GDBN} command is @samp{target}.
31191 @subsubheading Example
31195 -target-select remote /dev/ttya
31196 ^connected,addr="0xfe00a300",func="??",args=[]
31200 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31201 @node GDB/MI File Transfer Commands
31202 @section @sc{gdb/mi} File Transfer Commands
31205 @subheading The @code{-target-file-put} Command
31206 @findex -target-file-put
31208 @subsubheading Synopsis
31211 -target-file-put @var{hostfile} @var{targetfile}
31214 Copy file @var{hostfile} from the host system (the machine running
31215 @value{GDBN}) to @var{targetfile} on the target system.
31217 @subsubheading @value{GDBN} Command
31219 The corresponding @value{GDBN} command is @samp{remote put}.
31221 @subsubheading Example
31225 -target-file-put localfile remotefile
31231 @subheading The @code{-target-file-get} Command
31232 @findex -target-file-get
31234 @subsubheading Synopsis
31237 -target-file-get @var{targetfile} @var{hostfile}
31240 Copy file @var{targetfile} from the target system to @var{hostfile}
31241 on the host system.
31243 @subsubheading @value{GDBN} Command
31245 The corresponding @value{GDBN} command is @samp{remote get}.
31247 @subsubheading Example
31251 -target-file-get remotefile localfile
31257 @subheading The @code{-target-file-delete} Command
31258 @findex -target-file-delete
31260 @subsubheading Synopsis
31263 -target-file-delete @var{targetfile}
31266 Delete @var{targetfile} from the target system.
31268 @subsubheading @value{GDBN} Command
31270 The corresponding @value{GDBN} command is @samp{remote delete}.
31272 @subsubheading Example
31276 -target-file-delete remotefile
31282 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31283 @node GDB/MI Ada Exceptions Commands
31284 @section Ada Exceptions @sc{gdb/mi} Commands
31286 @subheading The @code{-info-ada-exceptions} Command
31287 @findex -info-ada-exceptions
31289 @subsubheading Synopsis
31292 -info-ada-exceptions [ @var{regexp}]
31295 List all Ada exceptions defined within the program being debugged.
31296 With a regular expression @var{regexp}, only those exceptions whose
31297 names match @var{regexp} are listed.
31299 @subsubheading @value{GDBN} Command
31301 The corresponding @value{GDBN} command is @samp{info exceptions}.
31303 @subsubheading Result
31305 The result is a table of Ada exceptions. The following columns are
31306 defined for each exception:
31310 The name of the exception.
31313 The address of the exception.
31317 @subsubheading Example
31320 -info-ada-exceptions aint
31321 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
31322 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
31323 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
31324 body=[@{name="constraint_error",address="0x0000000000613da0"@},
31325 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
31328 @subheading Catching Ada Exceptions
31330 The commands describing how to ask @value{GDBN} to stop when a program
31331 raises an exception are described at @ref{Ada Exception GDB/MI
31332 Catchpoint Commands}.
31335 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31336 @node GDB/MI Support Commands
31337 @section @sc{gdb/mi} Support Commands
31339 Since new commands and features get regularly added to @sc{gdb/mi},
31340 some commands are available to help front-ends query the debugger
31341 about support for these capabilities. Similarly, it is also possible
31342 to query @value{GDBN} about target support of certain features.
31344 @subheading The @code{-info-gdb-mi-command} Command
31345 @cindex @code{-info-gdb-mi-command}
31346 @findex -info-gdb-mi-command
31348 @subsubheading Synopsis
31351 -info-gdb-mi-command @var{cmd_name}
31354 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
31356 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
31357 is technically not part of the command name (@pxref{GDB/MI Input
31358 Syntax}), and thus should be omitted in @var{cmd_name}. However,
31359 for ease of use, this command also accepts the form with the leading
31362 @subsubheading @value{GDBN} Command
31364 There is no corresponding @value{GDBN} command.
31366 @subsubheading Result
31368 The result is a tuple. There is currently only one field:
31372 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
31373 @code{"false"} otherwise.
31377 @subsubheading Example
31379 Here is an example where the @sc{gdb/mi} command does not exist:
31382 -info-gdb-mi-command unsupported-command
31383 ^done,command=@{exists="false"@}
31387 And here is an example where the @sc{gdb/mi} command is known
31391 -info-gdb-mi-command symbol-list-lines
31392 ^done,command=@{exists="true"@}
31395 @subheading The @code{-list-features} Command
31396 @findex -list-features
31397 @cindex supported @sc{gdb/mi} features, list
31399 Returns a list of particular features of the MI protocol that
31400 this version of gdb implements. A feature can be a command,
31401 or a new field in an output of some command, or even an
31402 important bugfix. While a frontend can sometimes detect presence
31403 of a feature at runtime, it is easier to perform detection at debugger
31406 The command returns a list of strings, with each string naming an
31407 available feature. Each returned string is just a name, it does not
31408 have any internal structure. The list of possible feature names
31414 (gdb) -list-features
31415 ^done,result=["feature1","feature2"]
31418 The current list of features is:
31421 @item frozen-varobjs
31422 Indicates support for the @code{-var-set-frozen} command, as well
31423 as possible presense of the @code{frozen} field in the output
31424 of @code{-varobj-create}.
31425 @item pending-breakpoints
31426 Indicates support for the @option{-f} option to the @code{-break-insert}
31429 Indicates Python scripting support, Python-based
31430 pretty-printing commands, and possible presence of the
31431 @samp{display_hint} field in the output of @code{-var-list-children}
31433 Indicates support for the @code{-thread-info} command.
31434 @item data-read-memory-bytes
31435 Indicates support for the @code{-data-read-memory-bytes} and the
31436 @code{-data-write-memory-bytes} commands.
31437 @item breakpoint-notifications
31438 Indicates that changes to breakpoints and breakpoints created via the
31439 CLI will be announced via async records.
31440 @item ada-task-info
31441 Indicates support for the @code{-ada-task-info} command.
31442 @item language-option
31443 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
31444 option (@pxref{Context management}).
31445 @item info-gdb-mi-command
31446 Indicates support for the @code{-info-gdb-mi-command} command.
31447 @item undefined-command-error-code
31448 Indicates support for the "undefined-command" error code in error result
31449 records, produced when trying to execute an undefined @sc{gdb/mi} command
31450 (@pxref{GDB/MI Result Records}).
31451 @item exec-run-start-option
31452 Indicates that the @code{-exec-run} command supports the @option{--start}
31453 option (@pxref{GDB/MI Program Execution}).
31456 @subheading The @code{-list-target-features} Command
31457 @findex -list-target-features
31459 Returns a list of particular features that are supported by the
31460 target. Those features affect the permitted MI commands, but
31461 unlike the features reported by the @code{-list-features} command, the
31462 features depend on which target GDB is using at the moment. Whenever
31463 a target can change, due to commands such as @code{-target-select},
31464 @code{-target-attach} or @code{-exec-run}, the list of target features
31465 may change, and the frontend should obtain it again.
31469 (gdb) -list-target-features
31470 ^done,result=["async"]
31473 The current list of features is:
31477 Indicates that the target is capable of asynchronous command
31478 execution, which means that @value{GDBN} will accept further commands
31479 while the target is running.
31482 Indicates that the target is capable of reverse execution.
31483 @xref{Reverse Execution}, for more information.
31487 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31488 @node GDB/MI Miscellaneous Commands
31489 @section Miscellaneous @sc{gdb/mi} Commands
31491 @c @subheading -gdb-complete
31493 @subheading The @code{-gdb-exit} Command
31496 @subsubheading Synopsis
31502 Exit @value{GDBN} immediately.
31504 @subsubheading @value{GDBN} Command
31506 Approximately corresponds to @samp{quit}.
31508 @subsubheading Example
31518 @subheading The @code{-exec-abort} Command
31519 @findex -exec-abort
31521 @subsubheading Synopsis
31527 Kill the inferior running program.
31529 @subsubheading @value{GDBN} Command
31531 The corresponding @value{GDBN} command is @samp{kill}.
31533 @subsubheading Example
31538 @subheading The @code{-gdb-set} Command
31541 @subsubheading Synopsis
31547 Set an internal @value{GDBN} variable.
31548 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
31550 @subsubheading @value{GDBN} Command
31552 The corresponding @value{GDBN} command is @samp{set}.
31554 @subsubheading Example
31564 @subheading The @code{-gdb-show} Command
31567 @subsubheading Synopsis
31573 Show the current value of a @value{GDBN} variable.
31575 @subsubheading @value{GDBN} Command
31577 The corresponding @value{GDBN} command is @samp{show}.
31579 @subsubheading Example
31588 @c @subheading -gdb-source
31591 @subheading The @code{-gdb-version} Command
31592 @findex -gdb-version
31594 @subsubheading Synopsis
31600 Show version information for @value{GDBN}. Used mostly in testing.
31602 @subsubheading @value{GDBN} Command
31604 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
31605 default shows this information when you start an interactive session.
31607 @subsubheading Example
31609 @c This example modifies the actual output from GDB to avoid overfull
31615 ~Copyright 2000 Free Software Foundation, Inc.
31616 ~GDB is free software, covered by the GNU General Public License, and
31617 ~you are welcome to change it and/or distribute copies of it under
31618 ~ certain conditions.
31619 ~Type "show copying" to see the conditions.
31620 ~There is absolutely no warranty for GDB. Type "show warranty" for
31622 ~This GDB was configured as
31623 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
31628 @subheading The @code{-list-thread-groups} Command
31629 @findex -list-thread-groups
31631 @subheading Synopsis
31634 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
31637 Lists thread groups (@pxref{Thread groups}). When a single thread
31638 group is passed as the argument, lists the children of that group.
31639 When several thread group are passed, lists information about those
31640 thread groups. Without any parameters, lists information about all
31641 top-level thread groups.
31643 Normally, thread groups that are being debugged are reported.
31644 With the @samp{--available} option, @value{GDBN} reports thread groups
31645 available on the target.
31647 The output of this command may have either a @samp{threads} result or
31648 a @samp{groups} result. The @samp{thread} result has a list of tuples
31649 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
31650 Information}). The @samp{groups} result has a list of tuples as value,
31651 each tuple describing a thread group. If top-level groups are
31652 requested (that is, no parameter is passed), or when several groups
31653 are passed, the output always has a @samp{groups} result. The format
31654 of the @samp{group} result is described below.
31656 To reduce the number of roundtrips it's possible to list thread groups
31657 together with their children, by passing the @samp{--recurse} option
31658 and the recursion depth. Presently, only recursion depth of 1 is
31659 permitted. If this option is present, then every reported thread group
31660 will also include its children, either as @samp{group} or
31661 @samp{threads} field.
31663 In general, any combination of option and parameters is permitted, with
31664 the following caveats:
31668 When a single thread group is passed, the output will typically
31669 be the @samp{threads} result. Because threads may not contain
31670 anything, the @samp{recurse} option will be ignored.
31673 When the @samp{--available} option is passed, limited information may
31674 be available. In particular, the list of threads of a process might
31675 be inaccessible. Further, specifying specific thread groups might
31676 not give any performance advantage over listing all thread groups.
31677 The frontend should assume that @samp{-list-thread-groups --available}
31678 is always an expensive operation and cache the results.
31682 The @samp{groups} result is a list of tuples, where each tuple may
31683 have the following fields:
31687 Identifier of the thread group. This field is always present.
31688 The identifier is an opaque string; frontends should not try to
31689 convert it to an integer, even though it might look like one.
31692 The type of the thread group. At present, only @samp{process} is a
31696 The target-specific process identifier. This field is only present
31697 for thread groups of type @samp{process} and only if the process exists.
31700 The exit code of this group's last exited thread, formatted in octal.
31701 This field is only present for thread groups of type @samp{process} and
31702 only if the process is not running.
31705 The number of children this thread group has. This field may be
31706 absent for an available thread group.
31709 This field has a list of tuples as value, each tuple describing a
31710 thread. It may be present if the @samp{--recurse} option is
31711 specified, and it's actually possible to obtain the threads.
31714 This field is a list of integers, each identifying a core that one
31715 thread of the group is running on. This field may be absent if
31716 such information is not available.
31719 The name of the executable file that corresponds to this thread group.
31720 The field is only present for thread groups of type @samp{process},
31721 and only if there is a corresponding executable file.
31725 @subheading Example
31729 -list-thread-groups
31730 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
31731 -list-thread-groups 17
31732 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31733 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
31734 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31735 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
31736 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
31737 -list-thread-groups --available
31738 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
31739 -list-thread-groups --available --recurse 1
31740 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31741 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31742 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
31743 -list-thread-groups --available --recurse 1 17 18
31744 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31745 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31746 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
31749 @subheading The @code{-info-os} Command
31752 @subsubheading Synopsis
31755 -info-os [ @var{type} ]
31758 If no argument is supplied, the command returns a table of available
31759 operating-system-specific information types. If one of these types is
31760 supplied as an argument @var{type}, then the command returns a table
31761 of data of that type.
31763 The types of information available depend on the target operating
31766 @subsubheading @value{GDBN} Command
31768 The corresponding @value{GDBN} command is @samp{info os}.
31770 @subsubheading Example
31772 When run on a @sc{gnu}/Linux system, the output will look something
31778 ^done,OSDataTable=@{nr_rows="9",nr_cols="3",
31779 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
31780 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
31781 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
31782 body=[item=@{col0="processes",col1="Listing of all processes",
31783 col2="Processes"@},
31784 item=@{col0="procgroups",col1="Listing of all process groups",
31785 col2="Process groups"@},
31786 item=@{col0="threads",col1="Listing of all threads",
31788 item=@{col0="files",col1="Listing of all file descriptors",
31789 col2="File descriptors"@},
31790 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
31792 item=@{col0="shm",col1="Listing of all shared-memory regions",
31793 col2="Shared-memory regions"@},
31794 item=@{col0="semaphores",col1="Listing of all semaphores",
31795 col2="Semaphores"@},
31796 item=@{col0="msg",col1="Listing of all message queues",
31797 col2="Message queues"@},
31798 item=@{col0="modules",col1="Listing of all loaded kernel modules",
31799 col2="Kernel modules"@}]@}
31802 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
31803 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
31804 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
31805 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
31806 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
31807 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
31808 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
31809 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
31811 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
31812 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
31816 (Note that the MI output here includes a @code{"Title"} column that
31817 does not appear in command-line @code{info os}; this column is useful
31818 for MI clients that want to enumerate the types of data, such as in a
31819 popup menu, but is needless clutter on the command line, and
31820 @code{info os} omits it.)
31822 @subheading The @code{-add-inferior} Command
31823 @findex -add-inferior
31825 @subheading Synopsis
31831 Creates a new inferior (@pxref{Inferiors and Programs}). The created
31832 inferior is not associated with any executable. Such association may
31833 be established with the @samp{-file-exec-and-symbols} command
31834 (@pxref{GDB/MI File Commands}). The command response has a single
31835 field, @samp{inferior}, whose value is the identifier of the
31836 thread group corresponding to the new inferior.
31838 @subheading Example
31843 ^done,inferior="i3"
31846 @subheading The @code{-interpreter-exec} Command
31847 @findex -interpreter-exec
31849 @subheading Synopsis
31852 -interpreter-exec @var{interpreter} @var{command}
31854 @anchor{-interpreter-exec}
31856 Execute the specified @var{command} in the given @var{interpreter}.
31858 @subheading @value{GDBN} Command
31860 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
31862 @subheading Example
31866 -interpreter-exec console "break main"
31867 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
31868 &"During symbol reading, bad structure-type format.\n"
31869 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
31874 @subheading The @code{-inferior-tty-set} Command
31875 @findex -inferior-tty-set
31877 @subheading Synopsis
31880 -inferior-tty-set /dev/pts/1
31883 Set terminal for future runs of the program being debugged.
31885 @subheading @value{GDBN} Command
31887 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
31889 @subheading Example
31893 -inferior-tty-set /dev/pts/1
31898 @subheading The @code{-inferior-tty-show} Command
31899 @findex -inferior-tty-show
31901 @subheading Synopsis
31907 Show terminal for future runs of program being debugged.
31909 @subheading @value{GDBN} Command
31911 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
31913 @subheading Example
31917 -inferior-tty-set /dev/pts/1
31921 ^done,inferior_tty_terminal="/dev/pts/1"
31925 @subheading The @code{-enable-timings} Command
31926 @findex -enable-timings
31928 @subheading Synopsis
31931 -enable-timings [yes | no]
31934 Toggle the printing of the wallclock, user and system times for an MI
31935 command as a field in its output. This command is to help frontend
31936 developers optimize the performance of their code. No argument is
31937 equivalent to @samp{yes}.
31939 @subheading @value{GDBN} Command
31943 @subheading Example
31951 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31952 addr="0x080484ed",func="main",file="myprog.c",
31953 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
31955 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
31963 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
31964 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
31965 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
31966 fullname="/home/nickrob/myprog.c",line="73"@}
31971 @chapter @value{GDBN} Annotations
31973 This chapter describes annotations in @value{GDBN}. Annotations were
31974 designed to interface @value{GDBN} to graphical user interfaces or other
31975 similar programs which want to interact with @value{GDBN} at a
31976 relatively high level.
31978 The annotation mechanism has largely been superseded by @sc{gdb/mi}
31982 This is Edition @value{EDITION}, @value{DATE}.
31986 * Annotations Overview:: What annotations are; the general syntax.
31987 * Server Prefix:: Issuing a command without affecting user state.
31988 * Prompting:: Annotations marking @value{GDBN}'s need for input.
31989 * Errors:: Annotations for error messages.
31990 * Invalidation:: Some annotations describe things now invalid.
31991 * Annotations for Running::
31992 Whether the program is running, how it stopped, etc.
31993 * Source Annotations:: Annotations describing source code.
31996 @node Annotations Overview
31997 @section What is an Annotation?
31998 @cindex annotations
32000 Annotations start with a newline character, two @samp{control-z}
32001 characters, and the name of the annotation. If there is no additional
32002 information associated with this annotation, the name of the annotation
32003 is followed immediately by a newline. If there is additional
32004 information, the name of the annotation is followed by a space, the
32005 additional information, and a newline. The additional information
32006 cannot contain newline characters.
32008 Any output not beginning with a newline and two @samp{control-z}
32009 characters denotes literal output from @value{GDBN}. Currently there is
32010 no need for @value{GDBN} to output a newline followed by two
32011 @samp{control-z} characters, but if there was such a need, the
32012 annotations could be extended with an @samp{escape} annotation which
32013 means those three characters as output.
32015 The annotation @var{level}, which is specified using the
32016 @option{--annotate} command line option (@pxref{Mode Options}), controls
32017 how much information @value{GDBN} prints together with its prompt,
32018 values of expressions, source lines, and other types of output. Level 0
32019 is for no annotations, level 1 is for use when @value{GDBN} is run as a
32020 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
32021 for programs that control @value{GDBN}, and level 2 annotations have
32022 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
32023 Interface, annotate, GDB's Obsolete Annotations}).
32026 @kindex set annotate
32027 @item set annotate @var{level}
32028 The @value{GDBN} command @code{set annotate} sets the level of
32029 annotations to the specified @var{level}.
32031 @item show annotate
32032 @kindex show annotate
32033 Show the current annotation level.
32036 This chapter describes level 3 annotations.
32038 A simple example of starting up @value{GDBN} with annotations is:
32041 $ @kbd{gdb --annotate=3}
32043 Copyright 2003 Free Software Foundation, Inc.
32044 GDB is free software, covered by the GNU General Public License,
32045 and you are welcome to change it and/or distribute copies of it
32046 under certain conditions.
32047 Type "show copying" to see the conditions.
32048 There is absolutely no warranty for GDB. Type "show warranty"
32050 This GDB was configured as "i386-pc-linux-gnu"
32061 Here @samp{quit} is input to @value{GDBN}; the rest is output from
32062 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
32063 denotes a @samp{control-z} character) are annotations; the rest is
32064 output from @value{GDBN}.
32066 @node Server Prefix
32067 @section The Server Prefix
32068 @cindex server prefix
32070 If you prefix a command with @samp{server } then it will not affect
32071 the command history, nor will it affect @value{GDBN}'s notion of which
32072 command to repeat if @key{RET} is pressed on a line by itself. This
32073 means that commands can be run behind a user's back by a front-end in
32074 a transparent manner.
32076 The @code{server } prefix does not affect the recording of values into
32077 the value history; to print a value without recording it into the
32078 value history, use the @code{output} command instead of the
32079 @code{print} command.
32081 Using this prefix also disables confirmation requests
32082 (@pxref{confirmation requests}).
32085 @section Annotation for @value{GDBN} Input
32087 @cindex annotations for prompts
32088 When @value{GDBN} prompts for input, it annotates this fact so it is possible
32089 to know when to send output, when the output from a given command is
32092 Different kinds of input each have a different @dfn{input type}. Each
32093 input type has three annotations: a @code{pre-} annotation, which
32094 denotes the beginning of any prompt which is being output, a plain
32095 annotation, which denotes the end of the prompt, and then a @code{post-}
32096 annotation which denotes the end of any echo which may (or may not) be
32097 associated with the input. For example, the @code{prompt} input type
32098 features the following annotations:
32106 The input types are
32109 @findex pre-prompt annotation
32110 @findex prompt annotation
32111 @findex post-prompt annotation
32113 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
32115 @findex pre-commands annotation
32116 @findex commands annotation
32117 @findex post-commands annotation
32119 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
32120 command. The annotations are repeated for each command which is input.
32122 @findex pre-overload-choice annotation
32123 @findex overload-choice annotation
32124 @findex post-overload-choice annotation
32125 @item overload-choice
32126 When @value{GDBN} wants the user to select between various overloaded functions.
32128 @findex pre-query annotation
32129 @findex query annotation
32130 @findex post-query annotation
32132 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
32134 @findex pre-prompt-for-continue annotation
32135 @findex prompt-for-continue annotation
32136 @findex post-prompt-for-continue annotation
32137 @item prompt-for-continue
32138 When @value{GDBN} is asking the user to press return to continue. Note: Don't
32139 expect this to work well; instead use @code{set height 0} to disable
32140 prompting. This is because the counting of lines is buggy in the
32141 presence of annotations.
32146 @cindex annotations for errors, warnings and interrupts
32148 @findex quit annotation
32153 This annotation occurs right before @value{GDBN} responds to an interrupt.
32155 @findex error annotation
32160 This annotation occurs right before @value{GDBN} responds to an error.
32162 Quit and error annotations indicate that any annotations which @value{GDBN} was
32163 in the middle of may end abruptly. For example, if a
32164 @code{value-history-begin} annotation is followed by a @code{error}, one
32165 cannot expect to receive the matching @code{value-history-end}. One
32166 cannot expect not to receive it either, however; an error annotation
32167 does not necessarily mean that @value{GDBN} is immediately returning all the way
32170 @findex error-begin annotation
32171 A quit or error annotation may be preceded by
32177 Any output between that and the quit or error annotation is the error
32180 Warning messages are not yet annotated.
32181 @c If we want to change that, need to fix warning(), type_error(),
32182 @c range_error(), and possibly other places.
32185 @section Invalidation Notices
32187 @cindex annotations for invalidation messages
32188 The following annotations say that certain pieces of state may have
32192 @findex frames-invalid annotation
32193 @item ^Z^Zframes-invalid
32195 The frames (for example, output from the @code{backtrace} command) may
32198 @findex breakpoints-invalid annotation
32199 @item ^Z^Zbreakpoints-invalid
32201 The breakpoints may have changed. For example, the user just added or
32202 deleted a breakpoint.
32205 @node Annotations for Running
32206 @section Running the Program
32207 @cindex annotations for running programs
32209 @findex starting annotation
32210 @findex stopping annotation
32211 When the program starts executing due to a @value{GDBN} command such as
32212 @code{step} or @code{continue},
32218 is output. When the program stops,
32224 is output. Before the @code{stopped} annotation, a variety of
32225 annotations describe how the program stopped.
32228 @findex exited annotation
32229 @item ^Z^Zexited @var{exit-status}
32230 The program exited, and @var{exit-status} is the exit status (zero for
32231 successful exit, otherwise nonzero).
32233 @findex signalled annotation
32234 @findex signal-name annotation
32235 @findex signal-name-end annotation
32236 @findex signal-string annotation
32237 @findex signal-string-end annotation
32238 @item ^Z^Zsignalled
32239 The program exited with a signal. After the @code{^Z^Zsignalled}, the
32240 annotation continues:
32246 ^Z^Zsignal-name-end
32250 ^Z^Zsignal-string-end
32255 where @var{name} is the name of the signal, such as @code{SIGILL} or
32256 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
32257 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
32258 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
32259 user's benefit and have no particular format.
32261 @findex signal annotation
32263 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
32264 just saying that the program received the signal, not that it was
32265 terminated with it.
32267 @findex breakpoint annotation
32268 @item ^Z^Zbreakpoint @var{number}
32269 The program hit breakpoint number @var{number}.
32271 @findex watchpoint annotation
32272 @item ^Z^Zwatchpoint @var{number}
32273 The program hit watchpoint number @var{number}.
32276 @node Source Annotations
32277 @section Displaying Source
32278 @cindex annotations for source display
32280 @findex source annotation
32281 The following annotation is used instead of displaying source code:
32284 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
32287 where @var{filename} is an absolute file name indicating which source
32288 file, @var{line} is the line number within that file (where 1 is the
32289 first line in the file), @var{character} is the character position
32290 within the file (where 0 is the first character in the file) (for most
32291 debug formats this will necessarily point to the beginning of a line),
32292 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
32293 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
32294 @var{addr} is the address in the target program associated with the
32295 source which is being displayed. The @var{addr} is in the form @samp{0x}
32296 followed by one or more lowercase hex digits (note that this does not
32297 depend on the language).
32299 @node JIT Interface
32300 @chapter JIT Compilation Interface
32301 @cindex just-in-time compilation
32302 @cindex JIT compilation interface
32304 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
32305 interface. A JIT compiler is a program or library that generates native
32306 executable code at runtime and executes it, usually in order to achieve good
32307 performance while maintaining platform independence.
32309 Programs that use JIT compilation are normally difficult to debug because
32310 portions of their code are generated at runtime, instead of being loaded from
32311 object files, which is where @value{GDBN} normally finds the program's symbols
32312 and debug information. In order to debug programs that use JIT compilation,
32313 @value{GDBN} has an interface that allows the program to register in-memory
32314 symbol files with @value{GDBN} at runtime.
32316 If you are using @value{GDBN} to debug a program that uses this interface, then
32317 it should work transparently so long as you have not stripped the binary. If
32318 you are developing a JIT compiler, then the interface is documented in the rest
32319 of this chapter. At this time, the only known client of this interface is the
32322 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
32323 JIT compiler communicates with @value{GDBN} by writing data into a global
32324 variable and calling a fuction at a well-known symbol. When @value{GDBN}
32325 attaches, it reads a linked list of symbol files from the global variable to
32326 find existing code, and puts a breakpoint in the function so that it can find
32327 out about additional code.
32330 * Declarations:: Relevant C struct declarations
32331 * Registering Code:: Steps to register code
32332 * Unregistering Code:: Steps to unregister code
32333 * Custom Debug Info:: Emit debug information in a custom format
32337 @section JIT Declarations
32339 These are the relevant struct declarations that a C program should include to
32340 implement the interface:
32350 struct jit_code_entry
32352 struct jit_code_entry *next_entry;
32353 struct jit_code_entry *prev_entry;
32354 const char *symfile_addr;
32355 uint64_t symfile_size;
32358 struct jit_descriptor
32361 /* This type should be jit_actions_t, but we use uint32_t
32362 to be explicit about the bitwidth. */
32363 uint32_t action_flag;
32364 struct jit_code_entry *relevant_entry;
32365 struct jit_code_entry *first_entry;
32368 /* GDB puts a breakpoint in this function. */
32369 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
32371 /* Make sure to specify the version statically, because the
32372 debugger may check the version before we can set it. */
32373 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
32376 If the JIT is multi-threaded, then it is important that the JIT synchronize any
32377 modifications to this global data properly, which can easily be done by putting
32378 a global mutex around modifications to these structures.
32380 @node Registering Code
32381 @section Registering Code
32383 To register code with @value{GDBN}, the JIT should follow this protocol:
32387 Generate an object file in memory with symbols and other desired debug
32388 information. The file must include the virtual addresses of the sections.
32391 Create a code entry for the file, which gives the start and size of the symbol
32395 Add it to the linked list in the JIT descriptor.
32398 Point the relevant_entry field of the descriptor at the entry.
32401 Set @code{action_flag} to @code{JIT_REGISTER} and call
32402 @code{__jit_debug_register_code}.
32405 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
32406 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
32407 new code. However, the linked list must still be maintained in order to allow
32408 @value{GDBN} to attach to a running process and still find the symbol files.
32410 @node Unregistering Code
32411 @section Unregistering Code
32413 If code is freed, then the JIT should use the following protocol:
32417 Remove the code entry corresponding to the code from the linked list.
32420 Point the @code{relevant_entry} field of the descriptor at the code entry.
32423 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
32424 @code{__jit_debug_register_code}.
32427 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
32428 and the JIT will leak the memory used for the associated symbol files.
32430 @node Custom Debug Info
32431 @section Custom Debug Info
32432 @cindex custom JIT debug info
32433 @cindex JIT debug info reader
32435 Generating debug information in platform-native file formats (like ELF
32436 or COFF) may be an overkill for JIT compilers; especially if all the
32437 debug info is used for is displaying a meaningful backtrace. The
32438 issue can be resolved by having the JIT writers decide on a debug info
32439 format and also provide a reader that parses the debug info generated
32440 by the JIT compiler. This section gives a brief overview on writing
32441 such a parser. More specific details can be found in the source file
32442 @file{gdb/jit-reader.in}, which is also installed as a header at
32443 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
32445 The reader is implemented as a shared object (so this functionality is
32446 not available on platforms which don't allow loading shared objects at
32447 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
32448 @code{jit-reader-unload} are provided, to be used to load and unload
32449 the readers from a preconfigured directory. Once loaded, the shared
32450 object is used the parse the debug information emitted by the JIT
32454 * Using JIT Debug Info Readers:: How to use supplied readers correctly
32455 * Writing JIT Debug Info Readers:: Creating a debug-info reader
32458 @node Using JIT Debug Info Readers
32459 @subsection Using JIT Debug Info Readers
32460 @kindex jit-reader-load
32461 @kindex jit-reader-unload
32463 Readers can be loaded and unloaded using the @code{jit-reader-load}
32464 and @code{jit-reader-unload} commands.
32467 @item jit-reader-load @var{reader}
32468 Load the JIT reader named @var{reader}, which is a shared
32469 object specified as either an absolute or a relative file name. In
32470 the latter case, @value{GDBN} will try to load the reader from a
32471 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
32472 system (here @var{libdir} is the system library directory, often
32473 @file{/usr/local/lib}).
32475 Only one reader can be active at a time; trying to load a second
32476 reader when one is already loaded will result in @value{GDBN}
32477 reporting an error. A new JIT reader can be loaded by first unloading
32478 the current one using @code{jit-reader-unload} and then invoking
32479 @code{jit-reader-load}.
32481 @item jit-reader-unload
32482 Unload the currently loaded JIT reader.
32486 @node Writing JIT Debug Info Readers
32487 @subsection Writing JIT Debug Info Readers
32488 @cindex writing JIT debug info readers
32490 As mentioned, a reader is essentially a shared object conforming to a
32491 certain ABI. This ABI is described in @file{jit-reader.h}.
32493 @file{jit-reader.h} defines the structures, macros and functions
32494 required to write a reader. It is installed (along with
32495 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
32496 the system include directory.
32498 Readers need to be released under a GPL compatible license. A reader
32499 can be declared as released under such a license by placing the macro
32500 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
32502 The entry point for readers is the symbol @code{gdb_init_reader},
32503 which is expected to be a function with the prototype
32505 @findex gdb_init_reader
32507 extern struct gdb_reader_funcs *gdb_init_reader (void);
32510 @cindex @code{struct gdb_reader_funcs}
32512 @code{struct gdb_reader_funcs} contains a set of pointers to callback
32513 functions. These functions are executed to read the debug info
32514 generated by the JIT compiler (@code{read}), to unwind stack frames
32515 (@code{unwind}) and to create canonical frame IDs
32516 (@code{get_Frame_id}). It also has a callback that is called when the
32517 reader is being unloaded (@code{destroy}). The struct looks like this
32520 struct gdb_reader_funcs
32522 /* Must be set to GDB_READER_INTERFACE_VERSION. */
32523 int reader_version;
32525 /* For use by the reader. */
32528 gdb_read_debug_info *read;
32529 gdb_unwind_frame *unwind;
32530 gdb_get_frame_id *get_frame_id;
32531 gdb_destroy_reader *destroy;
32535 @cindex @code{struct gdb_symbol_callbacks}
32536 @cindex @code{struct gdb_unwind_callbacks}
32538 The callbacks are provided with another set of callbacks by
32539 @value{GDBN} to do their job. For @code{read}, these callbacks are
32540 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
32541 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
32542 @code{struct gdb_symbol_callbacks} has callbacks to create new object
32543 files and new symbol tables inside those object files. @code{struct
32544 gdb_unwind_callbacks} has callbacks to read registers off the current
32545 frame and to write out the values of the registers in the previous
32546 frame. Both have a callback (@code{target_read}) to read bytes off the
32547 target's address space.
32549 @node In-Process Agent
32550 @chapter In-Process Agent
32551 @cindex debugging agent
32552 The traditional debugging model is conceptually low-speed, but works fine,
32553 because most bugs can be reproduced in debugging-mode execution. However,
32554 as multi-core or many-core processors are becoming mainstream, and
32555 multi-threaded programs become more and more popular, there should be more
32556 and more bugs that only manifest themselves at normal-mode execution, for
32557 example, thread races, because debugger's interference with the program's
32558 timing may conceal the bugs. On the other hand, in some applications,
32559 it is not feasible for the debugger to interrupt the program's execution
32560 long enough for the developer to learn anything helpful about its behavior.
32561 If the program's correctness depends on its real-time behavior, delays
32562 introduced by a debugger might cause the program to fail, even when the
32563 code itself is correct. It is useful to be able to observe the program's
32564 behavior without interrupting it.
32566 Therefore, traditional debugging model is too intrusive to reproduce
32567 some bugs. In order to reduce the interference with the program, we can
32568 reduce the number of operations performed by debugger. The
32569 @dfn{In-Process Agent}, a shared library, is running within the same
32570 process with inferior, and is able to perform some debugging operations
32571 itself. As a result, debugger is only involved when necessary, and
32572 performance of debugging can be improved accordingly. Note that
32573 interference with program can be reduced but can't be removed completely,
32574 because the in-process agent will still stop or slow down the program.
32576 The in-process agent can interpret and execute Agent Expressions
32577 (@pxref{Agent Expressions}) during performing debugging operations. The
32578 agent expressions can be used for different purposes, such as collecting
32579 data in tracepoints, and condition evaluation in breakpoints.
32581 @anchor{Control Agent}
32582 You can control whether the in-process agent is used as an aid for
32583 debugging with the following commands:
32586 @kindex set agent on
32588 Causes the in-process agent to perform some operations on behalf of the
32589 debugger. Just which operations requested by the user will be done
32590 by the in-process agent depends on the its capabilities. For example,
32591 if you request to evaluate breakpoint conditions in the in-process agent,
32592 and the in-process agent has such capability as well, then breakpoint
32593 conditions will be evaluated in the in-process agent.
32595 @kindex set agent off
32596 @item set agent off
32597 Disables execution of debugging operations by the in-process agent. All
32598 of the operations will be performed by @value{GDBN}.
32602 Display the current setting of execution of debugging operations by
32603 the in-process agent.
32607 * In-Process Agent Protocol::
32610 @node In-Process Agent Protocol
32611 @section In-Process Agent Protocol
32612 @cindex in-process agent protocol
32614 The in-process agent is able to communicate with both @value{GDBN} and
32615 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
32616 used for communications between @value{GDBN} or GDBserver and the IPA.
32617 In general, @value{GDBN} or GDBserver sends commands
32618 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
32619 in-process agent replies back with the return result of the command, or
32620 some other information. The data sent to in-process agent is composed
32621 of primitive data types, such as 4-byte or 8-byte type, and composite
32622 types, which are called objects (@pxref{IPA Protocol Objects}).
32625 * IPA Protocol Objects::
32626 * IPA Protocol Commands::
32629 @node IPA Protocol Objects
32630 @subsection IPA Protocol Objects
32631 @cindex ipa protocol objects
32633 The commands sent to and results received from agent may contain some
32634 complex data types called @dfn{objects}.
32636 The in-process agent is running on the same machine with @value{GDBN}
32637 or GDBserver, so it doesn't have to handle as much differences between
32638 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
32639 However, there are still some differences of two ends in two processes:
32643 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
32644 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
32646 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
32647 GDBserver is compiled with one, and in-process agent is compiled with
32651 Here are the IPA Protocol Objects:
32655 agent expression object. It represents an agent expression
32656 (@pxref{Agent Expressions}).
32657 @anchor{agent expression object}
32659 tracepoint action object. It represents a tracepoint action
32660 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
32661 memory, static trace data and to evaluate expression.
32662 @anchor{tracepoint action object}
32664 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
32665 @anchor{tracepoint object}
32669 The following table describes important attributes of each IPA protocol
32672 @multitable @columnfractions .30 .20 .50
32673 @headitem Name @tab Size @tab Description
32674 @item @emph{agent expression object} @tab @tab
32675 @item length @tab 4 @tab length of bytes code
32676 @item byte code @tab @var{length} @tab contents of byte code
32677 @item @emph{tracepoint action for collecting memory} @tab @tab
32678 @item 'M' @tab 1 @tab type of tracepoint action
32679 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
32680 address of the lowest byte to collect, otherwise @var{addr} is the offset
32681 of @var{basereg} for memory collecting.
32682 @item len @tab 8 @tab length of memory for collecting
32683 @item basereg @tab 4 @tab the register number containing the starting
32684 memory address for collecting.
32685 @item @emph{tracepoint action for collecting registers} @tab @tab
32686 @item 'R' @tab 1 @tab type of tracepoint action
32687 @item @emph{tracepoint action for collecting static trace data} @tab @tab
32688 @item 'L' @tab 1 @tab type of tracepoint action
32689 @item @emph{tracepoint action for expression evaluation} @tab @tab
32690 @item 'X' @tab 1 @tab type of tracepoint action
32691 @item agent expression @tab length of @tab @ref{agent expression object}
32692 @item @emph{tracepoint object} @tab @tab
32693 @item number @tab 4 @tab number of tracepoint
32694 @item address @tab 8 @tab address of tracepoint inserted on
32695 @item type @tab 4 @tab type of tracepoint
32696 @item enabled @tab 1 @tab enable or disable of tracepoint
32697 @item step_count @tab 8 @tab step
32698 @item pass_count @tab 8 @tab pass
32699 @item numactions @tab 4 @tab number of tracepoint actions
32700 @item hit count @tab 8 @tab hit count
32701 @item trace frame usage @tab 8 @tab trace frame usage
32702 @item compiled_cond @tab 8 @tab compiled condition
32703 @item orig_size @tab 8 @tab orig size
32704 @item condition @tab 4 if condition is NULL otherwise length of
32705 @ref{agent expression object}
32706 @tab zero if condition is NULL, otherwise is
32707 @ref{agent expression object}
32708 @item actions @tab variable
32709 @tab numactions number of @ref{tracepoint action object}
32712 @node IPA Protocol Commands
32713 @subsection IPA Protocol Commands
32714 @cindex ipa protocol commands
32716 The spaces in each command are delimiters to ease reading this commands
32717 specification. They don't exist in real commands.
32721 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
32722 Installs a new fast tracepoint described by @var{tracepoint_object}
32723 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
32724 head of @dfn{jumppad}, which is used to jump to data collection routine
32729 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
32730 @var{target_address} is address of tracepoint in the inferior.
32731 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
32732 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
32733 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
32734 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
32741 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
32742 is about to kill inferiors.
32750 @item probe_marker_at:@var{address}
32751 Asks in-process agent to probe the marker at @var{address}.
32758 @item unprobe_marker_at:@var{address}
32759 Asks in-process agent to unprobe the marker at @var{address}.
32763 @chapter Reporting Bugs in @value{GDBN}
32764 @cindex bugs in @value{GDBN}
32765 @cindex reporting bugs in @value{GDBN}
32767 Your bug reports play an essential role in making @value{GDBN} reliable.
32769 Reporting a bug may help you by bringing a solution to your problem, or it
32770 may not. But in any case the principal function of a bug report is to help
32771 the entire community by making the next version of @value{GDBN} work better. Bug
32772 reports are your contribution to the maintenance of @value{GDBN}.
32774 In order for a bug report to serve its purpose, you must include the
32775 information that enables us to fix the bug.
32778 * Bug Criteria:: Have you found a bug?
32779 * Bug Reporting:: How to report bugs
32783 @section Have You Found a Bug?
32784 @cindex bug criteria
32786 If you are not sure whether you have found a bug, here are some guidelines:
32789 @cindex fatal signal
32790 @cindex debugger crash
32791 @cindex crash of debugger
32793 If the debugger gets a fatal signal, for any input whatever, that is a
32794 @value{GDBN} bug. Reliable debuggers never crash.
32796 @cindex error on valid input
32798 If @value{GDBN} produces an error message for valid input, that is a
32799 bug. (Note that if you're cross debugging, the problem may also be
32800 somewhere in the connection to the target.)
32802 @cindex invalid input
32804 If @value{GDBN} does not produce an error message for invalid input,
32805 that is a bug. However, you should note that your idea of
32806 ``invalid input'' might be our idea of ``an extension'' or ``support
32807 for traditional practice''.
32810 If you are an experienced user of debugging tools, your suggestions
32811 for improvement of @value{GDBN} are welcome in any case.
32814 @node Bug Reporting
32815 @section How to Report Bugs
32816 @cindex bug reports
32817 @cindex @value{GDBN} bugs, reporting
32819 A number of companies and individuals offer support for @sc{gnu} products.
32820 If you obtained @value{GDBN} from a support organization, we recommend you
32821 contact that organization first.
32823 You can find contact information for many support companies and
32824 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
32826 @c should add a web page ref...
32829 @ifset BUGURL_DEFAULT
32830 In any event, we also recommend that you submit bug reports for
32831 @value{GDBN}. The preferred method is to submit them directly using
32832 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
32833 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
32836 @strong{Do not send bug reports to @samp{info-gdb}, or to
32837 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
32838 not want to receive bug reports. Those that do have arranged to receive
32841 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
32842 serves as a repeater. The mailing list and the newsgroup carry exactly
32843 the same messages. Often people think of posting bug reports to the
32844 newsgroup instead of mailing them. This appears to work, but it has one
32845 problem which can be crucial: a newsgroup posting often lacks a mail
32846 path back to the sender. Thus, if we need to ask for more information,
32847 we may be unable to reach you. For this reason, it is better to send
32848 bug reports to the mailing list.
32850 @ifclear BUGURL_DEFAULT
32851 In any event, we also recommend that you submit bug reports for
32852 @value{GDBN} to @value{BUGURL}.
32856 The fundamental principle of reporting bugs usefully is this:
32857 @strong{report all the facts}. If you are not sure whether to state a
32858 fact or leave it out, state it!
32860 Often people omit facts because they think they know what causes the
32861 problem and assume that some details do not matter. Thus, you might
32862 assume that the name of the variable you use in an example does not matter.
32863 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
32864 stray memory reference which happens to fetch from the location where that
32865 name is stored in memory; perhaps, if the name were different, the contents
32866 of that location would fool the debugger into doing the right thing despite
32867 the bug. Play it safe and give a specific, complete example. That is the
32868 easiest thing for you to do, and the most helpful.
32870 Keep in mind that the purpose of a bug report is to enable us to fix the
32871 bug. It may be that the bug has been reported previously, but neither
32872 you nor we can know that unless your bug report is complete and
32875 Sometimes people give a few sketchy facts and ask, ``Does this ring a
32876 bell?'' Those bug reports are useless, and we urge everyone to
32877 @emph{refuse to respond to them} except to chide the sender to report
32880 To enable us to fix the bug, you should include all these things:
32884 The version of @value{GDBN}. @value{GDBN} announces it if you start
32885 with no arguments; you can also print it at any time using @code{show
32888 Without this, we will not know whether there is any point in looking for
32889 the bug in the current version of @value{GDBN}.
32892 The type of machine you are using, and the operating system name and
32896 The details of the @value{GDBN} build-time configuration.
32897 @value{GDBN} shows these details if you invoke it with the
32898 @option{--configuration} command-line option, or if you type
32899 @code{show configuration} at @value{GDBN}'s prompt.
32902 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
32903 ``@value{GCC}--2.8.1''.
32906 What compiler (and its version) was used to compile the program you are
32907 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
32908 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
32909 to get this information; for other compilers, see the documentation for
32913 The command arguments you gave the compiler to compile your example and
32914 observe the bug. For example, did you use @samp{-O}? To guarantee
32915 you will not omit something important, list them all. A copy of the
32916 Makefile (or the output from make) is sufficient.
32918 If we were to try to guess the arguments, we would probably guess wrong
32919 and then we might not encounter the bug.
32922 A complete input script, and all necessary source files, that will
32926 A description of what behavior you observe that you believe is
32927 incorrect. For example, ``It gets a fatal signal.''
32929 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
32930 will certainly notice it. But if the bug is incorrect output, we might
32931 not notice unless it is glaringly wrong. You might as well not give us
32932 a chance to make a mistake.
32934 Even if the problem you experience is a fatal signal, you should still
32935 say so explicitly. Suppose something strange is going on, such as, your
32936 copy of @value{GDBN} is out of synch, or you have encountered a bug in
32937 the C library on your system. (This has happened!) Your copy might
32938 crash and ours would not. If you told us to expect a crash, then when
32939 ours fails to crash, we would know that the bug was not happening for
32940 us. If you had not told us to expect a crash, then we would not be able
32941 to draw any conclusion from our observations.
32944 @cindex recording a session script
32945 To collect all this information, you can use a session recording program
32946 such as @command{script}, which is available on many Unix systems.
32947 Just run your @value{GDBN} session inside @command{script} and then
32948 include the @file{typescript} file with your bug report.
32950 Another way to record a @value{GDBN} session is to run @value{GDBN}
32951 inside Emacs and then save the entire buffer to a file.
32954 If you wish to suggest changes to the @value{GDBN} source, send us context
32955 diffs. If you even discuss something in the @value{GDBN} source, refer to
32956 it by context, not by line number.
32958 The line numbers in our development sources will not match those in your
32959 sources. Your line numbers would convey no useful information to us.
32963 Here are some things that are not necessary:
32967 A description of the envelope of the bug.
32969 Often people who encounter a bug spend a lot of time investigating
32970 which changes to the input file will make the bug go away and which
32971 changes will not affect it.
32973 This is often time consuming and not very useful, because the way we
32974 will find the bug is by running a single example under the debugger
32975 with breakpoints, not by pure deduction from a series of examples.
32976 We recommend that you save your time for something else.
32978 Of course, if you can find a simpler example to report @emph{instead}
32979 of the original one, that is a convenience for us. Errors in the
32980 output will be easier to spot, running under the debugger will take
32981 less time, and so on.
32983 However, simplification is not vital; if you do not want to do this,
32984 report the bug anyway and send us the entire test case you used.
32987 A patch for the bug.
32989 A patch for the bug does help us if it is a good one. But do not omit
32990 the necessary information, such as the test case, on the assumption that
32991 a patch is all we need. We might see problems with your patch and decide
32992 to fix the problem another way, or we might not understand it at all.
32994 Sometimes with a program as complicated as @value{GDBN} it is very hard to
32995 construct an example that will make the program follow a certain path
32996 through the code. If you do not send us the example, we will not be able
32997 to construct one, so we will not be able to verify that the bug is fixed.
32999 And if we cannot understand what bug you are trying to fix, or why your
33000 patch should be an improvement, we will not install it. A test case will
33001 help us to understand.
33004 A guess about what the bug is or what it depends on.
33006 Such guesses are usually wrong. Even we cannot guess right about such
33007 things without first using the debugger to find the facts.
33010 @c The readline documentation is distributed with the readline code
33011 @c and consists of the two following files:
33014 @c Use -I with makeinfo to point to the appropriate directory,
33015 @c environment var TEXINPUTS with TeX.
33016 @ifclear SYSTEM_READLINE
33017 @include rluser.texi
33018 @include hsuser.texi
33022 @appendix In Memoriam
33024 The @value{GDBN} project mourns the loss of the following long-time
33029 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
33030 to Free Software in general. Outside of @value{GDBN}, he was known in
33031 the Amiga world for his series of Fish Disks, and the GeekGadget project.
33033 @item Michael Snyder
33034 Michael was one of the Global Maintainers of the @value{GDBN} project,
33035 with contributions recorded as early as 1996, until 2011. In addition
33036 to his day to day participation, he was a large driving force behind
33037 adding Reverse Debugging to @value{GDBN}.
33040 Beyond their technical contributions to the project, they were also
33041 enjoyable members of the Free Software Community. We will miss them.
33043 @node Formatting Documentation
33044 @appendix Formatting Documentation
33046 @cindex @value{GDBN} reference card
33047 @cindex reference card
33048 The @value{GDBN} 4 release includes an already-formatted reference card, ready
33049 for printing with PostScript or Ghostscript, in the @file{gdb}
33050 subdirectory of the main source directory@footnote{In
33051 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
33052 release.}. If you can use PostScript or Ghostscript with your printer,
33053 you can print the reference card immediately with @file{refcard.ps}.
33055 The release also includes the source for the reference card. You
33056 can format it, using @TeX{}, by typing:
33062 The @value{GDBN} reference card is designed to print in @dfn{landscape}
33063 mode on US ``letter'' size paper;
33064 that is, on a sheet 11 inches wide by 8.5 inches
33065 high. You will need to specify this form of printing as an option to
33066 your @sc{dvi} output program.
33068 @cindex documentation
33070 All the documentation for @value{GDBN} comes as part of the machine-readable
33071 distribution. The documentation is written in Texinfo format, which is
33072 a documentation system that uses a single source file to produce both
33073 on-line information and a printed manual. You can use one of the Info
33074 formatting commands to create the on-line version of the documentation
33075 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
33077 @value{GDBN} includes an already formatted copy of the on-line Info
33078 version of this manual in the @file{gdb} subdirectory. The main Info
33079 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
33080 subordinate files matching @samp{gdb.info*} in the same directory. If
33081 necessary, you can print out these files, or read them with any editor;
33082 but they are easier to read using the @code{info} subsystem in @sc{gnu}
33083 Emacs or the standalone @code{info} program, available as part of the
33084 @sc{gnu} Texinfo distribution.
33086 If you want to format these Info files yourself, you need one of the
33087 Info formatting programs, such as @code{texinfo-format-buffer} or
33090 If you have @code{makeinfo} installed, and are in the top level
33091 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
33092 version @value{GDBVN}), you can make the Info file by typing:
33099 If you want to typeset and print copies of this manual, you need @TeX{},
33100 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
33101 Texinfo definitions file.
33103 @TeX{} is a typesetting program; it does not print files directly, but
33104 produces output files called @sc{dvi} files. To print a typeset
33105 document, you need a program to print @sc{dvi} files. If your system
33106 has @TeX{} installed, chances are it has such a program. The precise
33107 command to use depends on your system; @kbd{lpr -d} is common; another
33108 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
33109 require a file name without any extension or a @samp{.dvi} extension.
33111 @TeX{} also requires a macro definitions file called
33112 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
33113 written in Texinfo format. On its own, @TeX{} cannot either read or
33114 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
33115 and is located in the @file{gdb-@var{version-number}/texinfo}
33118 If you have @TeX{} and a @sc{dvi} printer program installed, you can
33119 typeset and print this manual. First switch to the @file{gdb}
33120 subdirectory of the main source directory (for example, to
33121 @file{gdb-@value{GDBVN}/gdb}) and type:
33127 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
33129 @node Installing GDB
33130 @appendix Installing @value{GDBN}
33131 @cindex installation
33134 * Requirements:: Requirements for building @value{GDBN}
33135 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
33136 * Separate Objdir:: Compiling @value{GDBN} in another directory
33137 * Config Names:: Specifying names for hosts and targets
33138 * Configure Options:: Summary of options for configure
33139 * System-wide configuration:: Having a system-wide init file
33143 @section Requirements for Building @value{GDBN}
33144 @cindex building @value{GDBN}, requirements for
33146 Building @value{GDBN} requires various tools and packages to be available.
33147 Other packages will be used only if they are found.
33149 @heading Tools/Packages Necessary for Building @value{GDBN}
33151 @item ISO C90 compiler
33152 @value{GDBN} is written in ISO C90. It should be buildable with any
33153 working C90 compiler, e.g.@: GCC.
33157 @heading Tools/Packages Optional for Building @value{GDBN}
33161 @value{GDBN} can use the Expat XML parsing library. This library may be
33162 included with your operating system distribution; if it is not, you
33163 can get the latest version from @url{http://expat.sourceforge.net}.
33164 The @file{configure} script will search for this library in several
33165 standard locations; if it is installed in an unusual path, you can
33166 use the @option{--with-libexpat-prefix} option to specify its location.
33172 Remote protocol memory maps (@pxref{Memory Map Format})
33174 Target descriptions (@pxref{Target Descriptions})
33176 Remote shared library lists (@xref{Library List Format},
33177 or alternatively @pxref{Library List Format for SVR4 Targets})
33179 MS-Windows shared libraries (@pxref{Shared Libraries})
33181 Traceframe info (@pxref{Traceframe Info Format})
33183 Branch trace (@pxref{Branch Trace Format},
33184 @pxref{Branch Trace Configuration Format})
33188 @cindex compressed debug sections
33189 @value{GDBN} will use the @samp{zlib} library, if available, to read
33190 compressed debug sections. Some linkers, such as GNU gold, are capable
33191 of producing binaries with compressed debug sections. If @value{GDBN}
33192 is compiled with @samp{zlib}, it will be able to read the debug
33193 information in such binaries.
33195 The @samp{zlib} library is likely included with your operating system
33196 distribution; if it is not, you can get the latest version from
33197 @url{http://zlib.net}.
33200 @value{GDBN}'s features related to character sets (@pxref{Character
33201 Sets}) require a functioning @code{iconv} implementation. If you are
33202 on a GNU system, then this is provided by the GNU C Library. Some
33203 other systems also provide a working @code{iconv}.
33205 If @value{GDBN} is using the @code{iconv} program which is installed
33206 in a non-standard place, you will need to tell @value{GDBN} where to find it.
33207 This is done with @option{--with-iconv-bin} which specifies the
33208 directory that contains the @code{iconv} program.
33210 On systems without @code{iconv}, you can install GNU Libiconv. If you
33211 have previously installed Libiconv, you can use the
33212 @option{--with-libiconv-prefix} option to configure.
33214 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
33215 arrange to build Libiconv if a directory named @file{libiconv} appears
33216 in the top-most source directory. If Libiconv is built this way, and
33217 if the operating system does not provide a suitable @code{iconv}
33218 implementation, then the just-built library will automatically be used
33219 by @value{GDBN}. One easy way to set this up is to download GNU
33220 Libiconv, unpack it, and then rename the directory holding the
33221 Libiconv source code to @samp{libiconv}.
33224 @node Running Configure
33225 @section Invoking the @value{GDBN} @file{configure} Script
33226 @cindex configuring @value{GDBN}
33227 @value{GDBN} comes with a @file{configure} script that automates the process
33228 of preparing @value{GDBN} for installation; you can then use @code{make} to
33229 build the @code{gdb} program.
33231 @c irrelevant in info file; it's as current as the code it lives with.
33232 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
33233 look at the @file{README} file in the sources; we may have improved the
33234 installation procedures since publishing this manual.}
33237 The @value{GDBN} distribution includes all the source code you need for
33238 @value{GDBN} in a single directory, whose name is usually composed by
33239 appending the version number to @samp{gdb}.
33241 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
33242 @file{gdb-@value{GDBVN}} directory. That directory contains:
33245 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
33246 script for configuring @value{GDBN} and all its supporting libraries
33248 @item gdb-@value{GDBVN}/gdb
33249 the source specific to @value{GDBN} itself
33251 @item gdb-@value{GDBVN}/bfd
33252 source for the Binary File Descriptor library
33254 @item gdb-@value{GDBVN}/include
33255 @sc{gnu} include files
33257 @item gdb-@value{GDBVN}/libiberty
33258 source for the @samp{-liberty} free software library
33260 @item gdb-@value{GDBVN}/opcodes
33261 source for the library of opcode tables and disassemblers
33263 @item gdb-@value{GDBVN}/readline
33264 source for the @sc{gnu} command-line interface
33266 @item gdb-@value{GDBVN}/glob
33267 source for the @sc{gnu} filename pattern-matching subroutine
33269 @item gdb-@value{GDBVN}/mmalloc
33270 source for the @sc{gnu} memory-mapped malloc package
33273 The simplest way to configure and build @value{GDBN} is to run @file{configure}
33274 from the @file{gdb-@var{version-number}} source directory, which in
33275 this example is the @file{gdb-@value{GDBVN}} directory.
33277 First switch to the @file{gdb-@var{version-number}} source directory
33278 if you are not already in it; then run @file{configure}. Pass the
33279 identifier for the platform on which @value{GDBN} will run as an
33285 cd gdb-@value{GDBVN}
33286 ./configure @var{host}
33291 where @var{host} is an identifier such as @samp{sun4} or
33292 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
33293 (You can often leave off @var{host}; @file{configure} tries to guess the
33294 correct value by examining your system.)
33296 Running @samp{configure @var{host}} and then running @code{make} builds the
33297 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
33298 libraries, then @code{gdb} itself. The configured source files, and the
33299 binaries, are left in the corresponding source directories.
33302 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
33303 system does not recognize this automatically when you run a different
33304 shell, you may need to run @code{sh} on it explicitly:
33307 sh configure @var{host}
33310 If you run @file{configure} from a directory that contains source
33311 directories for multiple libraries or programs, such as the
33312 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
33314 creates configuration files for every directory level underneath (unless
33315 you tell it not to, with the @samp{--norecursion} option).
33317 You should run the @file{configure} script from the top directory in the
33318 source tree, the @file{gdb-@var{version-number}} directory. If you run
33319 @file{configure} from one of the subdirectories, you will configure only
33320 that subdirectory. That is usually not what you want. In particular,
33321 if you run the first @file{configure} from the @file{gdb} subdirectory
33322 of the @file{gdb-@var{version-number}} directory, you will omit the
33323 configuration of @file{bfd}, @file{readline}, and other sibling
33324 directories of the @file{gdb} subdirectory. This leads to build errors
33325 about missing include files such as @file{bfd/bfd.h}.
33327 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
33328 However, you should make sure that the shell on your path (named by
33329 the @samp{SHELL} environment variable) is publicly readable. Remember
33330 that @value{GDBN} uses the shell to start your program---some systems refuse to
33331 let @value{GDBN} debug child processes whose programs are not readable.
33333 @node Separate Objdir
33334 @section Compiling @value{GDBN} in Another Directory
33336 If you want to run @value{GDBN} versions for several host or target machines,
33337 you need a different @code{gdb} compiled for each combination of
33338 host and target. @file{configure} is designed to make this easy by
33339 allowing you to generate each configuration in a separate subdirectory,
33340 rather than in the source directory. If your @code{make} program
33341 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
33342 @code{make} in each of these directories builds the @code{gdb}
33343 program specified there.
33345 To build @code{gdb} in a separate directory, run @file{configure}
33346 with the @samp{--srcdir} option to specify where to find the source.
33347 (You also need to specify a path to find @file{configure}
33348 itself from your working directory. If the path to @file{configure}
33349 would be the same as the argument to @samp{--srcdir}, you can leave out
33350 the @samp{--srcdir} option; it is assumed.)
33352 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
33353 separate directory for a Sun 4 like this:
33357 cd gdb-@value{GDBVN}
33360 ../gdb-@value{GDBVN}/configure sun4
33365 When @file{configure} builds a configuration using a remote source
33366 directory, it creates a tree for the binaries with the same structure
33367 (and using the same names) as the tree under the source directory. In
33368 the example, you'd find the Sun 4 library @file{libiberty.a} in the
33369 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
33370 @file{gdb-sun4/gdb}.
33372 Make sure that your path to the @file{configure} script has just one
33373 instance of @file{gdb} in it. If your path to @file{configure} looks
33374 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
33375 one subdirectory of @value{GDBN}, not the whole package. This leads to
33376 build errors about missing include files such as @file{bfd/bfd.h}.
33378 One popular reason to build several @value{GDBN} configurations in separate
33379 directories is to configure @value{GDBN} for cross-compiling (where
33380 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
33381 programs that run on another machine---the @dfn{target}).
33382 You specify a cross-debugging target by
33383 giving the @samp{--target=@var{target}} option to @file{configure}.
33385 When you run @code{make} to build a program or library, you must run
33386 it in a configured directory---whatever directory you were in when you
33387 called @file{configure} (or one of its subdirectories).
33389 The @code{Makefile} that @file{configure} generates in each source
33390 directory also runs recursively. If you type @code{make} in a source
33391 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
33392 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
33393 will build all the required libraries, and then build GDB.
33395 When you have multiple hosts or targets configured in separate
33396 directories, you can run @code{make} on them in parallel (for example,
33397 if they are NFS-mounted on each of the hosts); they will not interfere
33401 @section Specifying Names for Hosts and Targets
33403 The specifications used for hosts and targets in the @file{configure}
33404 script are based on a three-part naming scheme, but some short predefined
33405 aliases are also supported. The full naming scheme encodes three pieces
33406 of information in the following pattern:
33409 @var{architecture}-@var{vendor}-@var{os}
33412 For example, you can use the alias @code{sun4} as a @var{host} argument,
33413 or as the value for @var{target} in a @code{--target=@var{target}}
33414 option. The equivalent full name is @samp{sparc-sun-sunos4}.
33416 The @file{configure} script accompanying @value{GDBN} does not provide
33417 any query facility to list all supported host and target names or
33418 aliases. @file{configure} calls the Bourne shell script
33419 @code{config.sub} to map abbreviations to full names; you can read the
33420 script, if you wish, or you can use it to test your guesses on
33421 abbreviations---for example:
33424 % sh config.sub i386-linux
33426 % sh config.sub alpha-linux
33427 alpha-unknown-linux-gnu
33428 % sh config.sub hp9k700
33430 % sh config.sub sun4
33431 sparc-sun-sunos4.1.1
33432 % sh config.sub sun3
33433 m68k-sun-sunos4.1.1
33434 % sh config.sub i986v
33435 Invalid configuration `i986v': machine `i986v' not recognized
33439 @code{config.sub} is also distributed in the @value{GDBN} source
33440 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
33442 @node Configure Options
33443 @section @file{configure} Options
33445 Here is a summary of the @file{configure} options and arguments that
33446 are most often useful for building @value{GDBN}. @file{configure} also has
33447 several other options not listed here. @inforef{What Configure
33448 Does,,configure.info}, for a full explanation of @file{configure}.
33451 configure @r{[}--help@r{]}
33452 @r{[}--prefix=@var{dir}@r{]}
33453 @r{[}--exec-prefix=@var{dir}@r{]}
33454 @r{[}--srcdir=@var{dirname}@r{]}
33455 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
33456 @r{[}--target=@var{target}@r{]}
33461 You may introduce options with a single @samp{-} rather than
33462 @samp{--} if you prefer; but you may abbreviate option names if you use
33467 Display a quick summary of how to invoke @file{configure}.
33469 @item --prefix=@var{dir}
33470 Configure the source to install programs and files under directory
33473 @item --exec-prefix=@var{dir}
33474 Configure the source to install programs under directory
33477 @c avoid splitting the warning from the explanation:
33479 @item --srcdir=@var{dirname}
33480 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
33481 @code{make} that implements the @code{VPATH} feature.}@*
33482 Use this option to make configurations in directories separate from the
33483 @value{GDBN} source directories. Among other things, you can use this to
33484 build (or maintain) several configurations simultaneously, in separate
33485 directories. @file{configure} writes configuration-specific files in
33486 the current directory, but arranges for them to use the source in the
33487 directory @var{dirname}. @file{configure} creates directories under
33488 the working directory in parallel to the source directories below
33491 @item --norecursion
33492 Configure only the directory level where @file{configure} is executed; do not
33493 propagate configuration to subdirectories.
33495 @item --target=@var{target}
33496 Configure @value{GDBN} for cross-debugging programs running on the specified
33497 @var{target}. Without this option, @value{GDBN} is configured to debug
33498 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
33500 There is no convenient way to generate a list of all available targets.
33502 @item @var{host} @dots{}
33503 Configure @value{GDBN} to run on the specified @var{host}.
33505 There is no convenient way to generate a list of all available hosts.
33508 There are many other options available as well, but they are generally
33509 needed for special purposes only.
33511 @node System-wide configuration
33512 @section System-wide configuration and settings
33513 @cindex system-wide init file
33515 @value{GDBN} can be configured to have a system-wide init file;
33516 this file will be read and executed at startup (@pxref{Startup, , What
33517 @value{GDBN} does during startup}).
33519 Here is the corresponding configure option:
33522 @item --with-system-gdbinit=@var{file}
33523 Specify that the default location of the system-wide init file is
33527 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
33528 it may be subject to relocation. Two possible cases:
33532 If the default location of this init file contains @file{$prefix},
33533 it will be subject to relocation. Suppose that the configure options
33534 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
33535 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
33536 init file is looked for as @file{$install/etc/gdbinit} instead of
33537 @file{$prefix/etc/gdbinit}.
33540 By contrast, if the default location does not contain the prefix,
33541 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
33542 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
33543 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
33544 wherever @value{GDBN} is installed.
33547 If the configured location of the system-wide init file (as given by the
33548 @option{--with-system-gdbinit} option at configure time) is in the
33549 data-directory (as specified by @option{--with-gdb-datadir} at configure
33550 time) or in one of its subdirectories, then @value{GDBN} will look for the
33551 system-wide init file in the directory specified by the
33552 @option{--data-directory} command-line option.
33553 Note that the system-wide init file is only read once, during @value{GDBN}
33554 initialization. If the data-directory is changed after @value{GDBN} has
33555 started with the @code{set data-directory} command, the file will not be
33559 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
33562 @node System-wide Configuration Scripts
33563 @subsection Installed System-wide Configuration Scripts
33564 @cindex system-wide configuration scripts
33566 The @file{system-gdbinit} directory, located inside the data-directory
33567 (as specified by @option{--with-gdb-datadir} at configure time) contains
33568 a number of scripts which can be used as system-wide init files. To
33569 automatically source those scripts at startup, @value{GDBN} should be
33570 configured with @option{--with-system-gdbinit}. Otherwise, any user
33571 should be able to source them by hand as needed.
33573 The following scripts are currently available:
33576 @item @file{elinos.py}
33578 @cindex ELinOS system-wide configuration script
33579 This script is useful when debugging a program on an ELinOS target.
33580 It takes advantage of the environment variables defined in a standard
33581 ELinOS environment in order to determine the location of the system
33582 shared libraries, and then sets the @samp{solib-absolute-prefix}
33583 and @samp{solib-search-path} variables appropriately.
33585 @item @file{wrs-linux.py}
33586 @pindex wrs-linux.py
33587 @cindex Wind River Linux system-wide configuration script
33588 This script is useful when debugging a program on a target running
33589 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
33590 the host-side sysroot used by the target system.
33594 @node Maintenance Commands
33595 @appendix Maintenance Commands
33596 @cindex maintenance commands
33597 @cindex internal commands
33599 In addition to commands intended for @value{GDBN} users, @value{GDBN}
33600 includes a number of commands intended for @value{GDBN} developers,
33601 that are not documented elsewhere in this manual. These commands are
33602 provided here for reference. (For commands that turn on debugging
33603 messages, see @ref{Debugging Output}.)
33606 @kindex maint agent
33607 @kindex maint agent-eval
33608 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
33609 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
33610 Translate the given @var{expression} into remote agent bytecodes.
33611 This command is useful for debugging the Agent Expression mechanism
33612 (@pxref{Agent Expressions}). The @samp{agent} version produces an
33613 expression useful for data collection, such as by tracepoints, while
33614 @samp{maint agent-eval} produces an expression that evaluates directly
33615 to a result. For instance, a collection expression for @code{globa +
33616 globb} will include bytecodes to record four bytes of memory at each
33617 of the addresses of @code{globa} and @code{globb}, while discarding
33618 the result of the addition, while an evaluation expression will do the
33619 addition and return the sum.
33620 If @code{-at} is given, generate remote agent bytecode for @var{location}.
33621 If not, generate remote agent bytecode for current frame PC address.
33623 @kindex maint agent-printf
33624 @item maint agent-printf @var{format},@var{expr},...
33625 Translate the given format string and list of argument expressions
33626 into remote agent bytecodes and display them as a disassembled list.
33627 This command is useful for debugging the agent version of dynamic
33628 printf (@pxref{Dynamic Printf}).
33630 @kindex maint info breakpoints
33631 @item @anchor{maint info breakpoints}maint info breakpoints
33632 Using the same format as @samp{info breakpoints}, display both the
33633 breakpoints you've set explicitly, and those @value{GDBN} is using for
33634 internal purposes. Internal breakpoints are shown with negative
33635 breakpoint numbers. The type column identifies what kind of breakpoint
33640 Normal, explicitly set breakpoint.
33643 Normal, explicitly set watchpoint.
33646 Internal breakpoint, used to handle correctly stepping through
33647 @code{longjmp} calls.
33649 @item longjmp resume
33650 Internal breakpoint at the target of a @code{longjmp}.
33653 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
33656 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
33659 Shared library events.
33663 @kindex maint info bfds
33664 @item maint info bfds
33665 This prints information about each @code{bfd} object that is known to
33666 @value{GDBN}. @xref{Top, , BFD, bfd, The Binary File Descriptor Library}.
33668 @kindex set displaced-stepping
33669 @kindex show displaced-stepping
33670 @cindex displaced stepping support
33671 @cindex out-of-line single-stepping
33672 @item set displaced-stepping
33673 @itemx show displaced-stepping
33674 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
33675 if the target supports it. Displaced stepping is a way to single-step
33676 over breakpoints without removing them from the inferior, by executing
33677 an out-of-line copy of the instruction that was originally at the
33678 breakpoint location. It is also known as out-of-line single-stepping.
33681 @item set displaced-stepping on
33682 If the target architecture supports it, @value{GDBN} will use
33683 displaced stepping to step over breakpoints.
33685 @item set displaced-stepping off
33686 @value{GDBN} will not use displaced stepping to step over breakpoints,
33687 even if such is supported by the target architecture.
33689 @cindex non-stop mode, and @samp{set displaced-stepping}
33690 @item set displaced-stepping auto
33691 This is the default mode. @value{GDBN} will use displaced stepping
33692 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
33693 architecture supports displaced stepping.
33696 @kindex maint check-psymtabs
33697 @item maint check-psymtabs
33698 Check the consistency of currently expanded psymtabs versus symtabs.
33699 Use this to check, for example, whether a symbol is in one but not the other.
33701 @kindex maint check-symtabs
33702 @item maint check-symtabs
33703 Check the consistency of currently expanded symtabs.
33705 @kindex maint expand-symtabs
33706 @item maint expand-symtabs [@var{regexp}]
33707 Expand symbol tables.
33708 If @var{regexp} is specified, only expand symbol tables for file
33709 names matching @var{regexp}.
33711 @kindex maint set catch-demangler-crashes
33712 @kindex maint show catch-demangler-crashes
33713 @cindex demangler crashes
33714 @item maint set catch-demangler-crashes [on|off]
33715 @itemx maint show catch-demangler-crashes
33716 Control whether @value{GDBN} should attempt to catch crashes in the
33717 symbol name demangler. The default is to attempt to catch crashes.
33718 If enabled, the first time a crash is caught, a core file is created,
33719 the offending symbol is displayed and the user is presented with the
33720 option to terminate the current session.
33722 @kindex maint cplus first_component
33723 @item maint cplus first_component @var{name}
33724 Print the first C@t{++} class/namespace component of @var{name}.
33726 @kindex maint cplus namespace
33727 @item maint cplus namespace
33728 Print the list of possible C@t{++} namespaces.
33730 @kindex maint deprecate
33731 @kindex maint undeprecate
33732 @cindex deprecated commands
33733 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
33734 @itemx maint undeprecate @var{command}
33735 Deprecate or undeprecate the named @var{command}. Deprecated commands
33736 cause @value{GDBN} to issue a warning when you use them. The optional
33737 argument @var{replacement} says which newer command should be used in
33738 favor of the deprecated one; if it is given, @value{GDBN} will mention
33739 the replacement as part of the warning.
33741 @kindex maint dump-me
33742 @item maint dump-me
33743 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
33744 Cause a fatal signal in the debugger and force it to dump its core.
33745 This is supported only on systems which support aborting a program
33746 with the @code{SIGQUIT} signal.
33748 @kindex maint internal-error
33749 @kindex maint internal-warning
33750 @kindex maint demangler-warning
33751 @cindex demangler crashes
33752 @item maint internal-error @r{[}@var{message-text}@r{]}
33753 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
33754 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
33756 Cause @value{GDBN} to call the internal function @code{internal_error},
33757 @code{internal_warning} or @code{demangler_warning} and hence behave
33758 as though an internal problem has been detected. In addition to
33759 reporting the internal problem, these functions give the user the
33760 opportunity to either quit @value{GDBN} or (for @code{internal_error}
33761 and @code{internal_warning}) create a core file of the current
33762 @value{GDBN} session.
33764 These commands take an optional parameter @var{message-text} that is
33765 used as the text of the error or warning message.
33767 Here's an example of using @code{internal-error}:
33770 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
33771 @dots{}/maint.c:121: internal-error: testing, 1, 2
33772 A problem internal to GDB has been detected. Further
33773 debugging may prove unreliable.
33774 Quit this debugging session? (y or n) @kbd{n}
33775 Create a core file? (y or n) @kbd{n}
33779 @cindex @value{GDBN} internal error
33780 @cindex internal errors, control of @value{GDBN} behavior
33781 @cindex demangler crashes
33783 @kindex maint set internal-error
33784 @kindex maint show internal-error
33785 @kindex maint set internal-warning
33786 @kindex maint show internal-warning
33787 @kindex maint set demangler-warning
33788 @kindex maint show demangler-warning
33789 @item maint set internal-error @var{action} [ask|yes|no]
33790 @itemx maint show internal-error @var{action}
33791 @itemx maint set internal-warning @var{action} [ask|yes|no]
33792 @itemx maint show internal-warning @var{action}
33793 @itemx maint set demangler-warning @var{action} [ask|yes|no]
33794 @itemx maint show demangler-warning @var{action}
33795 When @value{GDBN} reports an internal problem (error or warning) it
33796 gives the user the opportunity to both quit @value{GDBN} and create a
33797 core file of the current @value{GDBN} session. These commands let you
33798 override the default behaviour for each particular @var{action},
33799 described in the table below.
33803 You can specify that @value{GDBN} should always (yes) or never (no)
33804 quit. The default is to ask the user what to do.
33807 You can specify that @value{GDBN} should always (yes) or never (no)
33808 create a core file. The default is to ask the user what to do. Note
33809 that there is no @code{corefile} option for @code{demangler-warning}:
33810 demangler warnings always create a core file and this cannot be
33814 @kindex maint packet
33815 @item maint packet @var{text}
33816 If @value{GDBN} is talking to an inferior via the serial protocol,
33817 then this command sends the string @var{text} to the inferior, and
33818 displays the response packet. @value{GDBN} supplies the initial
33819 @samp{$} character, the terminating @samp{#} character, and the
33822 @kindex maint print architecture
33823 @item maint print architecture @r{[}@var{file}@r{]}
33824 Print the entire architecture configuration. The optional argument
33825 @var{file} names the file where the output goes.
33827 @kindex maint print c-tdesc
33828 @item maint print c-tdesc
33829 Print the current target description (@pxref{Target Descriptions}) as
33830 a C source file. The created source file can be used in @value{GDBN}
33831 when an XML parser is not available to parse the description.
33833 @kindex maint print dummy-frames
33834 @item maint print dummy-frames
33835 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
33838 (@value{GDBP}) @kbd{b add}
33840 (@value{GDBP}) @kbd{print add(2,3)}
33841 Breakpoint 2, add (a=2, b=3) at @dots{}
33843 The program being debugged stopped while in a function called from GDB.
33845 (@value{GDBP}) @kbd{maint print dummy-frames}
33846 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
33850 Takes an optional file parameter.
33852 @kindex maint print registers
33853 @kindex maint print raw-registers
33854 @kindex maint print cooked-registers
33855 @kindex maint print register-groups
33856 @kindex maint print remote-registers
33857 @item maint print registers @r{[}@var{file}@r{]}
33858 @itemx maint print raw-registers @r{[}@var{file}@r{]}
33859 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
33860 @itemx maint print register-groups @r{[}@var{file}@r{]}
33861 @itemx maint print remote-registers @r{[}@var{file}@r{]}
33862 Print @value{GDBN}'s internal register data structures.
33864 The command @code{maint print raw-registers} includes the contents of
33865 the raw register cache; the command @code{maint print
33866 cooked-registers} includes the (cooked) value of all registers,
33867 including registers which aren't available on the target nor visible
33868 to user; the command @code{maint print register-groups} includes the
33869 groups that each register is a member of; and the command @code{maint
33870 print remote-registers} includes the remote target's register numbers
33871 and offsets in the `G' packets.
33873 These commands take an optional parameter, a file name to which to
33874 write the information.
33876 @kindex maint print reggroups
33877 @item maint print reggroups @r{[}@var{file}@r{]}
33878 Print @value{GDBN}'s internal register group data structures. The
33879 optional argument @var{file} tells to what file to write the
33882 The register groups info looks like this:
33885 (@value{GDBP}) @kbd{maint print reggroups}
33898 This command forces @value{GDBN} to flush its internal register cache.
33900 @kindex maint print objfiles
33901 @cindex info for known object files
33902 @item maint print objfiles @r{[}@var{regexp}@r{]}
33903 Print a dump of all known object files.
33904 If @var{regexp} is specified, only print object files whose names
33905 match @var{regexp}. For each object file, this command prints its name,
33906 address in memory, and all of its psymtabs and symtabs.
33908 @kindex maint print user-registers
33909 @cindex user registers
33910 @item maint print user-registers
33911 List all currently available @dfn{user registers}. User registers
33912 typically provide alternate names for actual hardware registers. They
33913 include the four ``standard'' registers @code{$fp}, @code{$pc},
33914 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
33915 registers can be used in expressions in the same way as the canonical
33916 register names, but only the latter are listed by the @code{info
33917 registers} and @code{maint print registers} commands.
33919 @kindex maint print section-scripts
33920 @cindex info for known .debug_gdb_scripts-loaded scripts
33921 @item maint print section-scripts [@var{regexp}]
33922 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
33923 If @var{regexp} is specified, only print scripts loaded by object files
33924 matching @var{regexp}.
33925 For each script, this command prints its name as specified in the objfile,
33926 and the full path if known.
33927 @xref{dotdebug_gdb_scripts section}.
33929 @kindex maint print statistics
33930 @cindex bcache statistics
33931 @item maint print statistics
33932 This command prints, for each object file in the program, various data
33933 about that object file followed by the byte cache (@dfn{bcache})
33934 statistics for the object file. The objfile data includes the number
33935 of minimal, partial, full, and stabs symbols, the number of types
33936 defined by the objfile, the number of as yet unexpanded psym tables,
33937 the number of line tables and string tables, and the amount of memory
33938 used by the various tables. The bcache statistics include the counts,
33939 sizes, and counts of duplicates of all and unique objects, max,
33940 average, and median entry size, total memory used and its overhead and
33941 savings, and various measures of the hash table size and chain
33944 @kindex maint print target-stack
33945 @cindex target stack description
33946 @item maint print target-stack
33947 A @dfn{target} is an interface between the debugger and a particular
33948 kind of file or process. Targets can be stacked in @dfn{strata},
33949 so that more than one target can potentially respond to a request.
33950 In particular, memory accesses will walk down the stack of targets
33951 until they find a target that is interested in handling that particular
33954 This command prints a short description of each layer that was pushed on
33955 the @dfn{target stack}, starting from the top layer down to the bottom one.
33957 @kindex maint print type
33958 @cindex type chain of a data type
33959 @item maint print type @var{expr}
33960 Print the type chain for a type specified by @var{expr}. The argument
33961 can be either a type name or a symbol. If it is a symbol, the type of
33962 that symbol is described. The type chain produced by this command is
33963 a recursive definition of the data type as stored in @value{GDBN}'s
33964 data structures, including its flags and contained types.
33966 @kindex maint set dwarf2 always-disassemble
33967 @kindex maint show dwarf2 always-disassemble
33968 @item maint set dwarf2 always-disassemble
33969 @item maint show dwarf2 always-disassemble
33970 Control the behavior of @code{info address} when using DWARF debugging
33973 The default is @code{off}, which means that @value{GDBN} should try to
33974 describe a variable's location in an easily readable format. When
33975 @code{on}, @value{GDBN} will instead display the DWARF location
33976 expression in an assembly-like format. Note that some locations are
33977 too complex for @value{GDBN} to describe simply; in this case you will
33978 always see the disassembly form.
33980 Here is an example of the resulting disassembly:
33983 (gdb) info addr argc
33984 Symbol "argc" is a complex DWARF expression:
33988 For more information on these expressions, see
33989 @uref{http://www.dwarfstd.org/, the DWARF standard}.
33991 @kindex maint set dwarf2 max-cache-age
33992 @kindex maint show dwarf2 max-cache-age
33993 @item maint set dwarf2 max-cache-age
33994 @itemx maint show dwarf2 max-cache-age
33995 Control the DWARF 2 compilation unit cache.
33997 @cindex DWARF 2 compilation units cache
33998 In object files with inter-compilation-unit references, such as those
33999 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
34000 reader needs to frequently refer to previously read compilation units.
34001 This setting controls how long a compilation unit will remain in the
34002 cache if it is not referenced. A higher limit means that cached
34003 compilation units will be stored in memory longer, and more total
34004 memory will be used. Setting it to zero disables caching, which will
34005 slow down @value{GDBN} startup, but reduce memory consumption.
34007 @kindex maint set profile
34008 @kindex maint show profile
34009 @cindex profiling GDB
34010 @item maint set profile
34011 @itemx maint show profile
34012 Control profiling of @value{GDBN}.
34014 Profiling will be disabled until you use the @samp{maint set profile}
34015 command to enable it. When you enable profiling, the system will begin
34016 collecting timing and execution count data; when you disable profiling or
34017 exit @value{GDBN}, the results will be written to a log file. Remember that
34018 if you use profiling, @value{GDBN} will overwrite the profiling log file
34019 (often called @file{gmon.out}). If you have a record of important profiling
34020 data in a @file{gmon.out} file, be sure to move it to a safe location.
34022 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
34023 compiled with the @samp{-pg} compiler option.
34025 @kindex maint set show-debug-regs
34026 @kindex maint show show-debug-regs
34027 @cindex hardware debug registers
34028 @item maint set show-debug-regs
34029 @itemx maint show show-debug-regs
34030 Control whether to show variables that mirror the hardware debug
34031 registers. Use @code{on} to enable, @code{off} to disable. If
34032 enabled, the debug registers values are shown when @value{GDBN} inserts or
34033 removes a hardware breakpoint or watchpoint, and when the inferior
34034 triggers a hardware-assisted breakpoint or watchpoint.
34036 @kindex maint set show-all-tib
34037 @kindex maint show show-all-tib
34038 @item maint set show-all-tib
34039 @itemx maint show show-all-tib
34040 Control whether to show all non zero areas within a 1k block starting
34041 at thread local base, when using the @samp{info w32 thread-information-block}
34044 @kindex maint set target-async
34045 @kindex maint show target-async
34046 @item maint set target-async
34047 @itemx maint show target-async
34048 This controls whether @value{GDBN} targets operate in synchronous or
34049 asynchronous mode (@pxref{Background Execution}). Normally the
34050 default is asynchronous, if it is available; but this can be changed
34051 to more easily debug problems occurring only in synchronous mode.
34053 @kindex maint set per-command
34054 @kindex maint show per-command
34055 @item maint set per-command
34056 @itemx maint show per-command
34057 @cindex resources used by commands
34059 @value{GDBN} can display the resources used by each command.
34060 This is useful in debugging performance problems.
34063 @item maint set per-command space [on|off]
34064 @itemx maint show per-command space
34065 Enable or disable the printing of the memory used by GDB for each command.
34066 If enabled, @value{GDBN} will display how much memory each command
34067 took, following the command's own output.
34068 This can also be requested by invoking @value{GDBN} with the
34069 @option{--statistics} command-line switch (@pxref{Mode Options}).
34071 @item maint set per-command time [on|off]
34072 @itemx maint show per-command time
34073 Enable or disable the printing of the execution time of @value{GDBN}
34075 If enabled, @value{GDBN} will display how much time it
34076 took to execute each command, following the command's own output.
34077 Both CPU time and wallclock time are printed.
34078 Printing both is useful when trying to determine whether the cost is
34079 CPU or, e.g., disk/network latency.
34080 Note that the CPU time printed is for @value{GDBN} only, it does not include
34081 the execution time of the inferior because there's no mechanism currently
34082 to compute how much time was spent by @value{GDBN} and how much time was
34083 spent by the program been debugged.
34084 This can also be requested by invoking @value{GDBN} with the
34085 @option{--statistics} command-line switch (@pxref{Mode Options}).
34087 @item maint set per-command symtab [on|off]
34088 @itemx maint show per-command symtab
34089 Enable or disable the printing of basic symbol table statistics
34091 If enabled, @value{GDBN} will display the following information:
34095 number of symbol tables
34097 number of primary symbol tables
34099 number of blocks in the blockvector
34103 @kindex maint space
34104 @cindex memory used by commands
34105 @item maint space @var{value}
34106 An alias for @code{maint set per-command space}.
34107 A non-zero value enables it, zero disables it.
34110 @cindex time of command execution
34111 @item maint time @var{value}
34112 An alias for @code{maint set per-command time}.
34113 A non-zero value enables it, zero disables it.
34115 @kindex maint translate-address
34116 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
34117 Find the symbol stored at the location specified by the address
34118 @var{addr} and an optional section name @var{section}. If found,
34119 @value{GDBN} prints the name of the closest symbol and an offset from
34120 the symbol's location to the specified address. This is similar to
34121 the @code{info address} command (@pxref{Symbols}), except that this
34122 command also allows to find symbols in other sections.
34124 If section was not specified, the section in which the symbol was found
34125 is also printed. For dynamically linked executables, the name of
34126 executable or shared library containing the symbol is printed as well.
34130 The following command is useful for non-interactive invocations of
34131 @value{GDBN}, such as in the test suite.
34134 @item set watchdog @var{nsec}
34135 @kindex set watchdog
34136 @cindex watchdog timer
34137 @cindex timeout for commands
34138 Set the maximum number of seconds @value{GDBN} will wait for the
34139 target operation to finish. If this time expires, @value{GDBN}
34140 reports and error and the command is aborted.
34142 @item show watchdog
34143 Show the current setting of the target wait timeout.
34146 @node Remote Protocol
34147 @appendix @value{GDBN} Remote Serial Protocol
34152 * Stop Reply Packets::
34153 * General Query Packets::
34154 * Architecture-Specific Protocol Details::
34155 * Tracepoint Packets::
34156 * Host I/O Packets::
34158 * Notification Packets::
34159 * Remote Non-Stop::
34160 * Packet Acknowledgment::
34162 * File-I/O Remote Protocol Extension::
34163 * Library List Format::
34164 * Library List Format for SVR4 Targets::
34165 * Memory Map Format::
34166 * Thread List Format::
34167 * Traceframe Info Format::
34168 * Branch Trace Format::
34169 * Branch Trace Configuration Format::
34175 There may be occasions when you need to know something about the
34176 protocol---for example, if there is only one serial port to your target
34177 machine, you might want your program to do something special if it
34178 recognizes a packet meant for @value{GDBN}.
34180 In the examples below, @samp{->} and @samp{<-} are used to indicate
34181 transmitted and received data, respectively.
34183 @cindex protocol, @value{GDBN} remote serial
34184 @cindex serial protocol, @value{GDBN} remote
34185 @cindex remote serial protocol
34186 All @value{GDBN} commands and responses (other than acknowledgments
34187 and notifications, see @ref{Notification Packets}) are sent as a
34188 @var{packet}. A @var{packet} is introduced with the character
34189 @samp{$}, the actual @var{packet-data}, and the terminating character
34190 @samp{#} followed by a two-digit @var{checksum}:
34193 @code{$}@var{packet-data}@code{#}@var{checksum}
34197 @cindex checksum, for @value{GDBN} remote
34199 The two-digit @var{checksum} is computed as the modulo 256 sum of all
34200 characters between the leading @samp{$} and the trailing @samp{#} (an
34201 eight bit unsigned checksum).
34203 Implementors should note that prior to @value{GDBN} 5.0 the protocol
34204 specification also included an optional two-digit @var{sequence-id}:
34207 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
34210 @cindex sequence-id, for @value{GDBN} remote
34212 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
34213 has never output @var{sequence-id}s. Stubs that handle packets added
34214 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
34216 When either the host or the target machine receives a packet, the first
34217 response expected is an acknowledgment: either @samp{+} (to indicate
34218 the package was received correctly) or @samp{-} (to request
34222 -> @code{$}@var{packet-data}@code{#}@var{checksum}
34227 The @samp{+}/@samp{-} acknowledgments can be disabled
34228 once a connection is established.
34229 @xref{Packet Acknowledgment}, for details.
34231 The host (@value{GDBN}) sends @var{command}s, and the target (the
34232 debugging stub incorporated in your program) sends a @var{response}. In
34233 the case of step and continue @var{command}s, the response is only sent
34234 when the operation has completed, and the target has again stopped all
34235 threads in all attached processes. This is the default all-stop mode
34236 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
34237 execution mode; see @ref{Remote Non-Stop}, for details.
34239 @var{packet-data} consists of a sequence of characters with the
34240 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
34243 @cindex remote protocol, field separator
34244 Fields within the packet should be separated using @samp{,} @samp{;} or
34245 @samp{:}. Except where otherwise noted all numbers are represented in
34246 @sc{hex} with leading zeros suppressed.
34248 Implementors should note that prior to @value{GDBN} 5.0, the character
34249 @samp{:} could not appear as the third character in a packet (as it
34250 would potentially conflict with the @var{sequence-id}).
34252 @cindex remote protocol, binary data
34253 @anchor{Binary Data}
34254 Binary data in most packets is encoded either as two hexadecimal
34255 digits per byte of binary data. This allowed the traditional remote
34256 protocol to work over connections which were only seven-bit clean.
34257 Some packets designed more recently assume an eight-bit clean
34258 connection, and use a more efficient encoding to send and receive
34261 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
34262 as an escape character. Any escaped byte is transmitted as the escape
34263 character followed by the original character XORed with @code{0x20}.
34264 For example, the byte @code{0x7d} would be transmitted as the two
34265 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
34266 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
34267 @samp{@}}) must always be escaped. Responses sent by the stub
34268 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
34269 is not interpreted as the start of a run-length encoded sequence
34272 Response @var{data} can be run-length encoded to save space.
34273 Run-length encoding replaces runs of identical characters with one
34274 instance of the repeated character, followed by a @samp{*} and a
34275 repeat count. The repeat count is itself sent encoded, to avoid
34276 binary characters in @var{data}: a value of @var{n} is sent as
34277 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
34278 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
34279 code 32) for a repeat count of 3. (This is because run-length
34280 encoding starts to win for counts 3 or more.) Thus, for example,
34281 @samp{0* } is a run-length encoding of ``0000'': the space character
34282 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
34285 The printable characters @samp{#} and @samp{$} or with a numeric value
34286 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
34287 seven repeats (@samp{$}) can be expanded using a repeat count of only
34288 five (@samp{"}). For example, @samp{00000000} can be encoded as
34291 The error response returned for some packets includes a two character
34292 error number. That number is not well defined.
34294 @cindex empty response, for unsupported packets
34295 For any @var{command} not supported by the stub, an empty response
34296 (@samp{$#00}) should be returned. That way it is possible to extend the
34297 protocol. A newer @value{GDBN} can tell if a packet is supported based
34300 At a minimum, a stub is required to support the @samp{g} and @samp{G}
34301 commands for register access, and the @samp{m} and @samp{M} commands
34302 for memory access. Stubs that only control single-threaded targets
34303 can implement run control with the @samp{c} (continue), and @samp{s}
34304 (step) commands. Stubs that support multi-threading targets should
34305 support the @samp{vCont} command. All other commands are optional.
34310 The following table provides a complete list of all currently defined
34311 @var{command}s and their corresponding response @var{data}.
34312 @xref{File-I/O Remote Protocol Extension}, for details about the File
34313 I/O extension of the remote protocol.
34315 Each packet's description has a template showing the packet's overall
34316 syntax, followed by an explanation of the packet's meaning. We
34317 include spaces in some of the templates for clarity; these are not
34318 part of the packet's syntax. No @value{GDBN} packet uses spaces to
34319 separate its components. For example, a template like @samp{foo
34320 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
34321 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
34322 @var{baz}. @value{GDBN} does not transmit a space character between the
34323 @samp{foo} and the @var{bar}, or between the @var{bar} and the
34326 @cindex @var{thread-id}, in remote protocol
34327 @anchor{thread-id syntax}
34328 Several packets and replies include a @var{thread-id} field to identify
34329 a thread. Normally these are positive numbers with a target-specific
34330 interpretation, formatted as big-endian hex strings. A @var{thread-id}
34331 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
34334 In addition, the remote protocol supports a multiprocess feature in
34335 which the @var{thread-id} syntax is extended to optionally include both
34336 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
34337 The @var{pid} (process) and @var{tid} (thread) components each have the
34338 format described above: a positive number with target-specific
34339 interpretation formatted as a big-endian hex string, literal @samp{-1}
34340 to indicate all processes or threads (respectively), or @samp{0} to
34341 indicate an arbitrary process or thread. Specifying just a process, as
34342 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
34343 error to specify all processes but a specific thread, such as
34344 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
34345 for those packets and replies explicitly documented to include a process
34346 ID, rather than a @var{thread-id}.
34348 The multiprocess @var{thread-id} syntax extensions are only used if both
34349 @value{GDBN} and the stub report support for the @samp{multiprocess}
34350 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
34353 Note that all packet forms beginning with an upper- or lower-case
34354 letter, other than those described here, are reserved for future use.
34356 Here are the packet descriptions.
34361 @cindex @samp{!} packet
34362 @anchor{extended mode}
34363 Enable extended mode. In extended mode, the remote server is made
34364 persistent. The @samp{R} packet is used to restart the program being
34370 The remote target both supports and has enabled extended mode.
34374 @cindex @samp{?} packet
34376 Indicate the reason the target halted. The reply is the same as for
34377 step and continue. This packet has a special interpretation when the
34378 target is in non-stop mode; see @ref{Remote Non-Stop}.
34381 @xref{Stop Reply Packets}, for the reply specifications.
34383 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
34384 @cindex @samp{A} packet
34385 Initialized @code{argv[]} array passed into program. @var{arglen}
34386 specifies the number of bytes in the hex encoded byte stream
34387 @var{arg}. See @code{gdbserver} for more details.
34392 The arguments were set.
34398 @cindex @samp{b} packet
34399 (Don't use this packet; its behavior is not well-defined.)
34400 Change the serial line speed to @var{baud}.
34402 JTC: @emph{When does the transport layer state change? When it's
34403 received, or after the ACK is transmitted. In either case, there are
34404 problems if the command or the acknowledgment packet is dropped.}
34406 Stan: @emph{If people really wanted to add something like this, and get
34407 it working for the first time, they ought to modify ser-unix.c to send
34408 some kind of out-of-band message to a specially-setup stub and have the
34409 switch happen "in between" packets, so that from remote protocol's point
34410 of view, nothing actually happened.}
34412 @item B @var{addr},@var{mode}
34413 @cindex @samp{B} packet
34414 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
34415 breakpoint at @var{addr}.
34417 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
34418 (@pxref{insert breakpoint or watchpoint packet}).
34420 @cindex @samp{bc} packet
34423 Backward continue. Execute the target system in reverse. No parameter.
34424 @xref{Reverse Execution}, for more information.
34427 @xref{Stop Reply Packets}, for the reply specifications.
34429 @cindex @samp{bs} packet
34432 Backward single step. Execute one instruction in reverse. No parameter.
34433 @xref{Reverse Execution}, for more information.
34436 @xref{Stop Reply Packets}, for the reply specifications.
34438 @item c @r{[}@var{addr}@r{]}
34439 @cindex @samp{c} packet
34440 Continue at @var{addr}, which is the address to resume. If @var{addr}
34441 is omitted, resume at current address.
34443 This packet is deprecated for multi-threading support. @xref{vCont
34447 @xref{Stop Reply Packets}, for the reply specifications.
34449 @item C @var{sig}@r{[};@var{addr}@r{]}
34450 @cindex @samp{C} packet
34451 Continue with signal @var{sig} (hex signal number). If
34452 @samp{;@var{addr}} is omitted, resume at same address.
34454 This packet is deprecated for multi-threading support. @xref{vCont
34458 @xref{Stop Reply Packets}, for the reply specifications.
34461 @cindex @samp{d} packet
34464 Don't use this packet; instead, define a general set packet
34465 (@pxref{General Query Packets}).
34469 @cindex @samp{D} packet
34470 The first form of the packet is used to detach @value{GDBN} from the
34471 remote system. It is sent to the remote target
34472 before @value{GDBN} disconnects via the @code{detach} command.
34474 The second form, including a process ID, is used when multiprocess
34475 protocol extensions are enabled (@pxref{multiprocess extensions}), to
34476 detach only a specific process. The @var{pid} is specified as a
34477 big-endian hex string.
34487 @item F @var{RC},@var{EE},@var{CF};@var{XX}
34488 @cindex @samp{F} packet
34489 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
34490 This is part of the File-I/O protocol extension. @xref{File-I/O
34491 Remote Protocol Extension}, for the specification.
34494 @anchor{read registers packet}
34495 @cindex @samp{g} packet
34496 Read general registers.
34500 @item @var{XX@dots{}}
34501 Each byte of register data is described by two hex digits. The bytes
34502 with the register are transmitted in target byte order. The size of
34503 each register and their position within the @samp{g} packet are
34504 determined by the @value{GDBN} internal gdbarch functions
34505 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
34506 specification of several standard @samp{g} packets is specified below.
34508 When reading registers from a trace frame (@pxref{Analyze Collected
34509 Data,,Using the Collected Data}), the stub may also return a string of
34510 literal @samp{x}'s in place of the register data digits, to indicate
34511 that the corresponding register has not been collected, thus its value
34512 is unavailable. For example, for an architecture with 4 registers of
34513 4 bytes each, the following reply indicates to @value{GDBN} that
34514 registers 0 and 2 have not been collected, while registers 1 and 3
34515 have been collected, and both have zero value:
34519 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
34526 @item G @var{XX@dots{}}
34527 @cindex @samp{G} packet
34528 Write general registers. @xref{read registers packet}, for a
34529 description of the @var{XX@dots{}} data.
34539 @item H @var{op} @var{thread-id}
34540 @cindex @samp{H} packet
34541 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
34542 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
34543 should be @samp{c} for step and continue operations (note that this
34544 is deprecated, supporting the @samp{vCont} command is a better
34545 option), and @samp{g} for other operations. The thread designator
34546 @var{thread-id} has the format and interpretation described in
34547 @ref{thread-id syntax}.
34558 @c 'H': How restrictive (or permissive) is the thread model. If a
34559 @c thread is selected and stopped, are other threads allowed
34560 @c to continue to execute? As I mentioned above, I think the
34561 @c semantics of each command when a thread is selected must be
34562 @c described. For example:
34564 @c 'g': If the stub supports threads and a specific thread is
34565 @c selected, returns the register block from that thread;
34566 @c otherwise returns current registers.
34568 @c 'G' If the stub supports threads and a specific thread is
34569 @c selected, sets the registers of the register block of
34570 @c that thread; otherwise sets current registers.
34572 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
34573 @anchor{cycle step packet}
34574 @cindex @samp{i} packet
34575 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
34576 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
34577 step starting at that address.
34580 @cindex @samp{I} packet
34581 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
34585 @cindex @samp{k} packet
34588 The exact effect of this packet is not specified.
34590 For a bare-metal target, it may power cycle or reset the target
34591 system. For that reason, the @samp{k} packet has no reply.
34593 For a single-process target, it may kill that process if possible.
34595 A multiple-process target may choose to kill just one process, or all
34596 that are under @value{GDBN}'s control. For more precise control, use
34597 the vKill packet (@pxref{vKill packet}).
34599 If the target system immediately closes the connection in response to
34600 @samp{k}, @value{GDBN} does not consider the lack of packet
34601 acknowledgment to be an error, and assumes the kill was successful.
34603 If connected using @kbd{target extended-remote}, and the target does
34604 not close the connection in response to a kill request, @value{GDBN}
34605 probes the target state as if a new connection was opened
34606 (@pxref{? packet}).
34608 @item m @var{addr},@var{length}
34609 @cindex @samp{m} packet
34610 Read @var{length} bytes of memory starting at address @var{addr}.
34611 Note that @var{addr} may not be aligned to any particular boundary.
34613 The stub need not use any particular size or alignment when gathering
34614 data from memory for the response; even if @var{addr} is word-aligned
34615 and @var{length} is a multiple of the word size, the stub is free to
34616 use byte accesses, or not. For this reason, this packet may not be
34617 suitable for accessing memory-mapped I/O devices.
34618 @cindex alignment of remote memory accesses
34619 @cindex size of remote memory accesses
34620 @cindex memory, alignment and size of remote accesses
34624 @item @var{XX@dots{}}
34625 Memory contents; each byte is transmitted as a two-digit hexadecimal
34626 number. The reply may contain fewer bytes than requested if the
34627 server was able to read only part of the region of memory.
34632 @item M @var{addr},@var{length}:@var{XX@dots{}}
34633 @cindex @samp{M} packet
34634 Write @var{length} bytes of memory starting at address @var{addr}.
34635 The data is given by @var{XX@dots{}}; each byte is transmitted as a two-digit
34636 hexadecimal number.
34643 for an error (this includes the case where only part of the data was
34648 @cindex @samp{p} packet
34649 Read the value of register @var{n}; @var{n} is in hex.
34650 @xref{read registers packet}, for a description of how the returned
34651 register value is encoded.
34655 @item @var{XX@dots{}}
34656 the register's value
34660 Indicating an unrecognized @var{query}.
34663 @item P @var{n@dots{}}=@var{r@dots{}}
34664 @anchor{write register packet}
34665 @cindex @samp{P} packet
34666 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
34667 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
34668 digits for each byte in the register (target byte order).
34678 @item q @var{name} @var{params}@dots{}
34679 @itemx Q @var{name} @var{params}@dots{}
34680 @cindex @samp{q} packet
34681 @cindex @samp{Q} packet
34682 General query (@samp{q}) and set (@samp{Q}). These packets are
34683 described fully in @ref{General Query Packets}.
34686 @cindex @samp{r} packet
34687 Reset the entire system.
34689 Don't use this packet; use the @samp{R} packet instead.
34692 @cindex @samp{R} packet
34693 Restart the program being debugged. The @var{XX}, while needed, is ignored.
34694 This packet is only available in extended mode (@pxref{extended mode}).
34696 The @samp{R} packet has no reply.
34698 @item s @r{[}@var{addr}@r{]}
34699 @cindex @samp{s} packet
34700 Single step, resuming at @var{addr}. If
34701 @var{addr} is omitted, resume at same address.
34703 This packet is deprecated for multi-threading support. @xref{vCont
34707 @xref{Stop Reply Packets}, for the reply specifications.
34709 @item S @var{sig}@r{[};@var{addr}@r{]}
34710 @anchor{step with signal packet}
34711 @cindex @samp{S} packet
34712 Step with signal. This is analogous to the @samp{C} packet, but
34713 requests a single-step, rather than a normal resumption of execution.
34715 This packet is deprecated for multi-threading support. @xref{vCont
34719 @xref{Stop Reply Packets}, for the reply specifications.
34721 @item t @var{addr}:@var{PP},@var{MM}
34722 @cindex @samp{t} packet
34723 Search backwards starting at address @var{addr} for a match with pattern
34724 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
34725 There must be at least 3 digits in @var{addr}.
34727 @item T @var{thread-id}
34728 @cindex @samp{T} packet
34729 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
34734 thread is still alive
34740 Packets starting with @samp{v} are identified by a multi-letter name,
34741 up to the first @samp{;} or @samp{?} (or the end of the packet).
34743 @item vAttach;@var{pid}
34744 @cindex @samp{vAttach} packet
34745 Attach to a new process with the specified process ID @var{pid}.
34746 The process ID is a
34747 hexadecimal integer identifying the process. In all-stop mode, all
34748 threads in the attached process are stopped; in non-stop mode, it may be
34749 attached without being stopped if that is supported by the target.
34751 @c In non-stop mode, on a successful vAttach, the stub should set the
34752 @c current thread to a thread of the newly-attached process. After
34753 @c attaching, GDB queries for the attached process's thread ID with qC.
34754 @c Also note that, from a user perspective, whether or not the
34755 @c target is stopped on attach in non-stop mode depends on whether you
34756 @c use the foreground or background version of the attach command, not
34757 @c on what vAttach does; GDB does the right thing with respect to either
34758 @c stopping or restarting threads.
34760 This packet is only available in extended mode (@pxref{extended mode}).
34766 @item @r{Any stop packet}
34767 for success in all-stop mode (@pxref{Stop Reply Packets})
34769 for success in non-stop mode (@pxref{Remote Non-Stop})
34772 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
34773 @cindex @samp{vCont} packet
34774 @anchor{vCont packet}
34775 Resume the inferior, specifying different actions for each thread.
34776 If an action is specified with no @var{thread-id}, then it is applied to any
34777 threads that don't have a specific action specified; if no default action is
34778 specified then other threads should remain stopped in all-stop mode and
34779 in their current state in non-stop mode.
34780 Specifying multiple
34781 default actions is an error; specifying no actions is also an error.
34782 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
34784 Currently supported actions are:
34790 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
34794 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
34797 @item r @var{start},@var{end}
34798 Step once, and then keep stepping as long as the thread stops at
34799 addresses between @var{start} (inclusive) and @var{end} (exclusive).
34800 The remote stub reports a stop reply when either the thread goes out
34801 of the range or is stopped due to an unrelated reason, such as hitting
34802 a breakpoint. @xref{range stepping}.
34804 If the range is empty (@var{start} == @var{end}), then the action
34805 becomes equivalent to the @samp{s} action. In other words,
34806 single-step once, and report the stop (even if the stepped instruction
34807 jumps to @var{start}).
34809 (A stop reply may be sent at any point even if the PC is still within
34810 the stepping range; for example, it is valid to implement this packet
34811 in a degenerate way as a single instruction step operation.)
34815 The optional argument @var{addr} normally associated with the
34816 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
34817 not supported in @samp{vCont}.
34819 The @samp{t} action is only relevant in non-stop mode
34820 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
34821 A stop reply should be generated for any affected thread not already stopped.
34822 When a thread is stopped by means of a @samp{t} action,
34823 the corresponding stop reply should indicate that the thread has stopped with
34824 signal @samp{0}, regardless of whether the target uses some other signal
34825 as an implementation detail.
34827 The stub must support @samp{vCont} if it reports support for
34828 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
34829 this case @samp{vCont} actions can be specified to apply to all threads
34830 in a process by using the @samp{p@var{pid}.-1} form of the
34834 @xref{Stop Reply Packets}, for the reply specifications.
34837 @cindex @samp{vCont?} packet
34838 Request a list of actions supported by the @samp{vCont} packet.
34842 @item vCont@r{[};@var{action}@dots{}@r{]}
34843 The @samp{vCont} packet is supported. Each @var{action} is a supported
34844 command in the @samp{vCont} packet.
34846 The @samp{vCont} packet is not supported.
34849 @item vFile:@var{operation}:@var{parameter}@dots{}
34850 @cindex @samp{vFile} packet
34851 Perform a file operation on the target system. For details,
34852 see @ref{Host I/O Packets}.
34854 @item vFlashErase:@var{addr},@var{length}
34855 @cindex @samp{vFlashErase} packet
34856 Direct the stub to erase @var{length} bytes of flash starting at
34857 @var{addr}. The region may enclose any number of flash blocks, but
34858 its start and end must fall on block boundaries, as indicated by the
34859 flash block size appearing in the memory map (@pxref{Memory Map
34860 Format}). @value{GDBN} groups flash memory programming operations
34861 together, and sends a @samp{vFlashDone} request after each group; the
34862 stub is allowed to delay erase operation until the @samp{vFlashDone}
34863 packet is received.
34873 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
34874 @cindex @samp{vFlashWrite} packet
34875 Direct the stub to write data to flash address @var{addr}. The data
34876 is passed in binary form using the same encoding as for the @samp{X}
34877 packet (@pxref{Binary Data}). The memory ranges specified by
34878 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
34879 not overlap, and must appear in order of increasing addresses
34880 (although @samp{vFlashErase} packets for higher addresses may already
34881 have been received; the ordering is guaranteed only between
34882 @samp{vFlashWrite} packets). If a packet writes to an address that was
34883 neither erased by a preceding @samp{vFlashErase} packet nor by some other
34884 target-specific method, the results are unpredictable.
34892 for vFlashWrite addressing non-flash memory
34898 @cindex @samp{vFlashDone} packet
34899 Indicate to the stub that flash programming operation is finished.
34900 The stub is permitted to delay or batch the effects of a group of
34901 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
34902 @samp{vFlashDone} packet is received. The contents of the affected
34903 regions of flash memory are unpredictable until the @samp{vFlashDone}
34904 request is completed.
34906 @item vKill;@var{pid}
34907 @cindex @samp{vKill} packet
34908 @anchor{vKill packet}
34909 Kill the process with the specified process ID @var{pid}, which is a
34910 hexadecimal integer identifying the process. This packet is used in
34911 preference to @samp{k} when multiprocess protocol extensions are
34912 supported; see @ref{multiprocess extensions}.
34922 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
34923 @cindex @samp{vRun} packet
34924 Run the program @var{filename}, passing it each @var{argument} on its
34925 command line. The file and arguments are hex-encoded strings. If
34926 @var{filename} is an empty string, the stub may use a default program
34927 (e.g.@: the last program run). The program is created in the stopped
34930 @c FIXME: What about non-stop mode?
34932 This packet is only available in extended mode (@pxref{extended mode}).
34938 @item @r{Any stop packet}
34939 for success (@pxref{Stop Reply Packets})
34943 @cindex @samp{vStopped} packet
34944 @xref{Notification Packets}.
34946 @item X @var{addr},@var{length}:@var{XX@dots{}}
34948 @cindex @samp{X} packet
34949 Write data to memory, where the data is transmitted in binary.
34950 Memory is specified by its address @var{addr} and number of bytes @var{length};
34951 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
34961 @item z @var{type},@var{addr},@var{kind}
34962 @itemx Z @var{type},@var{addr},@var{kind}
34963 @anchor{insert breakpoint or watchpoint packet}
34964 @cindex @samp{z} packet
34965 @cindex @samp{Z} packets
34966 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
34967 watchpoint starting at address @var{address} of kind @var{kind}.
34969 Each breakpoint and watchpoint packet @var{type} is documented
34972 @emph{Implementation notes: A remote target shall return an empty string
34973 for an unrecognized breakpoint or watchpoint packet @var{type}. A
34974 remote target shall support either both or neither of a given
34975 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
34976 avoid potential problems with duplicate packets, the operations should
34977 be implemented in an idempotent way.}
34979 @item z0,@var{addr},@var{kind}
34980 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
34981 @cindex @samp{z0} packet
34982 @cindex @samp{Z0} packet
34983 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
34984 @var{addr} of type @var{kind}.
34986 A memory breakpoint is implemented by replacing the instruction at
34987 @var{addr} with a software breakpoint or trap instruction. The
34988 @var{kind} is target-specific and typically indicates the size of
34989 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
34990 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
34991 architectures have additional meanings for @var{kind};
34992 @var{cond_list} is an optional list of conditional expressions in bytecode
34993 form that should be evaluated on the target's side. These are the
34994 conditions that should be taken into consideration when deciding if
34995 the breakpoint trigger should be reported back to @var{GDBN}.
34997 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
34998 for how to best report a memory breakpoint event to @value{GDBN}.
35000 The @var{cond_list} parameter is comprised of a series of expressions,
35001 concatenated without separators. Each expression has the following form:
35005 @item X @var{len},@var{expr}
35006 @var{len} is the length of the bytecode expression and @var{expr} is the
35007 actual conditional expression in bytecode form.
35011 The optional @var{cmd_list} parameter introduces commands that may be
35012 run on the target, rather than being reported back to @value{GDBN}.
35013 The parameter starts with a numeric flag @var{persist}; if the flag is
35014 nonzero, then the breakpoint may remain active and the commands
35015 continue to be run even when @value{GDBN} disconnects from the target.
35016 Following this flag is a series of expressions concatenated with no
35017 separators. Each expression has the following form:
35021 @item X @var{len},@var{expr}
35022 @var{len} is the length of the bytecode expression and @var{expr} is the
35023 actual conditional expression in bytecode form.
35027 see @ref{Architecture-Specific Protocol Details}.
35029 @emph{Implementation note: It is possible for a target to copy or move
35030 code that contains memory breakpoints (e.g., when implementing
35031 overlays). The behavior of this packet, in the presence of such a
35032 target, is not defined.}
35044 @item z1,@var{addr},@var{kind}
35045 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
35046 @cindex @samp{z1} packet
35047 @cindex @samp{Z1} packet
35048 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
35049 address @var{addr}.
35051 A hardware breakpoint is implemented using a mechanism that is not
35052 dependant on being able to modify the target's memory. The @var{kind}
35053 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
35055 @emph{Implementation note: A hardware breakpoint is not affected by code
35068 @item z2,@var{addr},@var{kind}
35069 @itemx Z2,@var{addr},@var{kind}
35070 @cindex @samp{z2} packet
35071 @cindex @samp{Z2} packet
35072 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
35073 The number of bytes to watch is specified by @var{kind}.
35085 @item z3,@var{addr},@var{kind}
35086 @itemx Z3,@var{addr},@var{kind}
35087 @cindex @samp{z3} packet
35088 @cindex @samp{Z3} packet
35089 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
35090 The number of bytes to watch is specified by @var{kind}.
35102 @item z4,@var{addr},@var{kind}
35103 @itemx Z4,@var{addr},@var{kind}
35104 @cindex @samp{z4} packet
35105 @cindex @samp{Z4} packet
35106 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
35107 The number of bytes to watch is specified by @var{kind}.
35121 @node Stop Reply Packets
35122 @section Stop Reply Packets
35123 @cindex stop reply packets
35125 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
35126 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
35127 receive any of the below as a reply. Except for @samp{?}
35128 and @samp{vStopped}, that reply is only returned
35129 when the target halts. In the below the exact meaning of @dfn{signal
35130 number} is defined by the header @file{include/gdb/signals.h} in the
35131 @value{GDBN} source code.
35133 As in the description of request packets, we include spaces in the
35134 reply templates for clarity; these are not part of the reply packet's
35135 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
35141 The program received signal number @var{AA} (a two-digit hexadecimal
35142 number). This is equivalent to a @samp{T} response with no
35143 @var{n}:@var{r} pairs.
35145 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
35146 @cindex @samp{T} packet reply
35147 The program received signal number @var{AA} (a two-digit hexadecimal
35148 number). This is equivalent to an @samp{S} response, except that the
35149 @samp{@var{n}:@var{r}} pairs can carry values of important registers
35150 and other information directly in the stop reply packet, reducing
35151 round-trip latency. Single-step and breakpoint traps are reported
35152 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
35156 If @var{n} is a hexadecimal number, it is a register number, and the
35157 corresponding @var{r} gives that register's value. The data @var{r} is a
35158 series of bytes in target byte order, with each byte given by a
35159 two-digit hex number.
35162 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
35163 the stopped thread, as specified in @ref{thread-id syntax}.
35166 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
35167 the core on which the stop event was detected.
35170 If @var{n} is a recognized @dfn{stop reason}, it describes a more
35171 specific event that stopped the target. The currently defined stop
35172 reasons are listed below. The @var{aa} should be @samp{05}, the trap
35173 signal. At most one stop reason should be present.
35176 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
35177 and go on to the next; this allows us to extend the protocol in the
35181 The currently defined stop reasons are:
35187 The packet indicates a watchpoint hit, and @var{r} is the data address, in
35190 @cindex shared library events, remote reply
35192 The packet indicates that the loaded libraries have changed.
35193 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
35194 list of loaded libraries. The @var{r} part is ignored.
35196 @cindex replay log events, remote reply
35198 The packet indicates that the target cannot continue replaying
35199 logged execution events, because it has reached the end (or the
35200 beginning when executing backward) of the log. The value of @var{r}
35201 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
35202 for more information.
35205 @anchor{swbreak stop reason}
35206 The packet indicates a memory breakpoint instruction was executed,
35207 irrespective of whether it was @value{GDBN} that planted the
35208 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
35209 part must be left empty.
35211 On some architectures, such as x86, at the architecture level, when a
35212 breakpoint instruction executes the program counter points at the
35213 breakpoint address plus an offset. On such targets, the stub is
35214 responsible for adjusting the PC to point back at the breakpoint
35217 This packet should not be sent by default; older @value{GDBN} versions
35218 did not support it. @value{GDBN} requests it, by supplying an
35219 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35220 remote stub must also supply the appropriate @samp{qSupported} feature
35221 indicating support.
35223 This packet is required for correct non-stop mode operation.
35226 The packet indicates the target stopped for a hardware breakpoint.
35227 The @var{r} part must be left empty.
35229 The same remarks about @samp{qSupported} and non-stop mode above
35234 @itemx W @var{AA} ; process:@var{pid}
35235 The process exited, and @var{AA} is the exit status. This is only
35236 applicable to certain targets.
35238 The second form of the response, including the process ID of the exited
35239 process, can be used only when @value{GDBN} has reported support for
35240 multiprocess protocol extensions; see @ref{multiprocess extensions}.
35241 The @var{pid} is formatted as a big-endian hex string.
35244 @itemx X @var{AA} ; process:@var{pid}
35245 The process terminated with signal @var{AA}.
35247 The second form of the response, including the process ID of the
35248 terminated process, can be used only when @value{GDBN} has reported
35249 support for multiprocess protocol extensions; see @ref{multiprocess
35250 extensions}. The @var{pid} is formatted as a big-endian hex string.
35252 @item O @var{XX}@dots{}
35253 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
35254 written as the program's console output. This can happen at any time
35255 while the program is running and the debugger should continue to wait
35256 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
35258 @item F @var{call-id},@var{parameter}@dots{}
35259 @var{call-id} is the identifier which says which host system call should
35260 be called. This is just the name of the function. Translation into the
35261 correct system call is only applicable as it's defined in @value{GDBN}.
35262 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
35265 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
35266 this very system call.
35268 The target replies with this packet when it expects @value{GDBN} to
35269 call a host system call on behalf of the target. @value{GDBN} replies
35270 with an appropriate @samp{F} packet and keeps up waiting for the next
35271 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
35272 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
35273 Protocol Extension}, for more details.
35277 @node General Query Packets
35278 @section General Query Packets
35279 @cindex remote query requests
35281 Packets starting with @samp{q} are @dfn{general query packets};
35282 packets starting with @samp{Q} are @dfn{general set packets}. General
35283 query and set packets are a semi-unified form for retrieving and
35284 sending information to and from the stub.
35286 The initial letter of a query or set packet is followed by a name
35287 indicating what sort of thing the packet applies to. For example,
35288 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
35289 definitions with the stub. These packet names follow some
35294 The name must not contain commas, colons or semicolons.
35296 Most @value{GDBN} query and set packets have a leading upper case
35299 The names of custom vendor packets should use a company prefix, in
35300 lower case, followed by a period. For example, packets designed at
35301 the Acme Corporation might begin with @samp{qacme.foo} (for querying
35302 foos) or @samp{Qacme.bar} (for setting bars).
35305 The name of a query or set packet should be separated from any
35306 parameters by a @samp{:}; the parameters themselves should be
35307 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
35308 full packet name, and check for a separator or the end of the packet,
35309 in case two packet names share a common prefix. New packets should not begin
35310 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
35311 packets predate these conventions, and have arguments without any terminator
35312 for the packet name; we suspect they are in widespread use in places that
35313 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
35314 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
35317 Like the descriptions of the other packets, each description here
35318 has a template showing the packet's overall syntax, followed by an
35319 explanation of the packet's meaning. We include spaces in some of the
35320 templates for clarity; these are not part of the packet's syntax. No
35321 @value{GDBN} packet uses spaces to separate its components.
35323 Here are the currently defined query and set packets:
35329 Turn on or off the agent as a helper to perform some debugging operations
35330 delegated from @value{GDBN} (@pxref{Control Agent}).
35332 @item QAllow:@var{op}:@var{val}@dots{}
35333 @cindex @samp{QAllow} packet
35334 Specify which operations @value{GDBN} expects to request of the
35335 target, as a semicolon-separated list of operation name and value
35336 pairs. Possible values for @var{op} include @samp{WriteReg},
35337 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
35338 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
35339 indicating that @value{GDBN} will not request the operation, or 1,
35340 indicating that it may. (The target can then use this to set up its
35341 own internals optimally, for instance if the debugger never expects to
35342 insert breakpoints, it may not need to install its own trap handler.)
35345 @cindex current thread, remote request
35346 @cindex @samp{qC} packet
35347 Return the current thread ID.
35351 @item QC @var{thread-id}
35352 Where @var{thread-id} is a thread ID as documented in
35353 @ref{thread-id syntax}.
35354 @item @r{(anything else)}
35355 Any other reply implies the old thread ID.
35358 @item qCRC:@var{addr},@var{length}
35359 @cindex CRC of memory block, remote request
35360 @cindex @samp{qCRC} packet
35361 @anchor{qCRC packet}
35362 Compute the CRC checksum of a block of memory using CRC-32 defined in
35363 IEEE 802.3. The CRC is computed byte at a time, taking the most
35364 significant bit of each byte first. The initial pattern code
35365 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
35367 @emph{Note:} This is the same CRC used in validating separate debug
35368 files (@pxref{Separate Debug Files, , Debugging Information in Separate
35369 Files}). However the algorithm is slightly different. When validating
35370 separate debug files, the CRC is computed taking the @emph{least}
35371 significant bit of each byte first, and the final result is inverted to
35372 detect trailing zeros.
35377 An error (such as memory fault)
35378 @item C @var{crc32}
35379 The specified memory region's checksum is @var{crc32}.
35382 @item QDisableRandomization:@var{value}
35383 @cindex disable address space randomization, remote request
35384 @cindex @samp{QDisableRandomization} packet
35385 Some target operating systems will randomize the virtual address space
35386 of the inferior process as a security feature, but provide a feature
35387 to disable such randomization, e.g.@: to allow for a more deterministic
35388 debugging experience. On such systems, this packet with a @var{value}
35389 of 1 directs the target to disable address space randomization for
35390 processes subsequently started via @samp{vRun} packets, while a packet
35391 with a @var{value} of 0 tells the target to enable address space
35394 This packet is only available in extended mode (@pxref{extended mode}).
35399 The request succeeded.
35402 An error occurred. The error number @var{nn} is given as hex digits.
35405 An empty reply indicates that @samp{QDisableRandomization} is not supported
35409 This packet is not probed by default; the remote stub must request it,
35410 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35411 This should only be done on targets that actually support disabling
35412 address space randomization.
35415 @itemx qsThreadInfo
35416 @cindex list active threads, remote request
35417 @cindex @samp{qfThreadInfo} packet
35418 @cindex @samp{qsThreadInfo} packet
35419 Obtain a list of all active thread IDs from the target (OS). Since there
35420 may be too many active threads to fit into one reply packet, this query
35421 works iteratively: it may require more than one query/reply sequence to
35422 obtain the entire list of threads. The first query of the sequence will
35423 be the @samp{qfThreadInfo} query; subsequent queries in the
35424 sequence will be the @samp{qsThreadInfo} query.
35426 NOTE: This packet replaces the @samp{qL} query (see below).
35430 @item m @var{thread-id}
35432 @item m @var{thread-id},@var{thread-id}@dots{}
35433 a comma-separated list of thread IDs
35435 (lower case letter @samp{L}) denotes end of list.
35438 In response to each query, the target will reply with a list of one or
35439 more thread IDs, separated by commas.
35440 @value{GDBN} will respond to each reply with a request for more thread
35441 ids (using the @samp{qs} form of the query), until the target responds
35442 with @samp{l} (lower-case ell, for @dfn{last}).
35443 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
35446 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
35447 initial connection with the remote target, and the very first thread ID
35448 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
35449 message. Therefore, the stub should ensure that the first thread ID in
35450 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
35452 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
35453 @cindex get thread-local storage address, remote request
35454 @cindex @samp{qGetTLSAddr} packet
35455 Fetch the address associated with thread local storage specified
35456 by @var{thread-id}, @var{offset}, and @var{lm}.
35458 @var{thread-id} is the thread ID associated with the
35459 thread for which to fetch the TLS address. @xref{thread-id syntax}.
35461 @var{offset} is the (big endian, hex encoded) offset associated with the
35462 thread local variable. (This offset is obtained from the debug
35463 information associated with the variable.)
35465 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
35466 load module associated with the thread local storage. For example,
35467 a @sc{gnu}/Linux system will pass the link map address of the shared
35468 object associated with the thread local storage under consideration.
35469 Other operating environments may choose to represent the load module
35470 differently, so the precise meaning of this parameter will vary.
35474 @item @var{XX}@dots{}
35475 Hex encoded (big endian) bytes representing the address of the thread
35476 local storage requested.
35479 An error occurred. The error number @var{nn} is given as hex digits.
35482 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
35485 @item qGetTIBAddr:@var{thread-id}
35486 @cindex get thread information block address
35487 @cindex @samp{qGetTIBAddr} packet
35488 Fetch address of the Windows OS specific Thread Information Block.
35490 @var{thread-id} is the thread ID associated with the thread.
35494 @item @var{XX}@dots{}
35495 Hex encoded (big endian) bytes representing the linear address of the
35496 thread information block.
35499 An error occured. This means that either the thread was not found, or the
35500 address could not be retrieved.
35503 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
35506 @item qL @var{startflag} @var{threadcount} @var{nextthread}
35507 Obtain thread information from RTOS. Where: @var{startflag} (one hex
35508 digit) is one to indicate the first query and zero to indicate a
35509 subsequent query; @var{threadcount} (two hex digits) is the maximum
35510 number of threads the response packet can contain; and @var{nextthread}
35511 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
35512 returned in the response as @var{argthread}.
35514 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
35518 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
35519 Where: @var{count} (two hex digits) is the number of threads being
35520 returned; @var{done} (one hex digit) is zero to indicate more threads
35521 and one indicates no further threads; @var{argthreadid} (eight hex
35522 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
35523 is a sequence of thread IDs, @var{threadid} (eight hex
35524 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
35528 @cindex section offsets, remote request
35529 @cindex @samp{qOffsets} packet
35530 Get section offsets that the target used when relocating the downloaded
35535 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
35536 Relocate the @code{Text} section by @var{xxx} from its original address.
35537 Relocate the @code{Data} section by @var{yyy} from its original address.
35538 If the object file format provides segment information (e.g.@: @sc{elf}
35539 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
35540 segments by the supplied offsets.
35542 @emph{Note: while a @code{Bss} offset may be included in the response,
35543 @value{GDBN} ignores this and instead applies the @code{Data} offset
35544 to the @code{Bss} section.}
35546 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
35547 Relocate the first segment of the object file, which conventionally
35548 contains program code, to a starting address of @var{xxx}. If
35549 @samp{DataSeg} is specified, relocate the second segment, which
35550 conventionally contains modifiable data, to a starting address of
35551 @var{yyy}. @value{GDBN} will report an error if the object file
35552 does not contain segment information, or does not contain at least
35553 as many segments as mentioned in the reply. Extra segments are
35554 kept at fixed offsets relative to the last relocated segment.
35557 @item qP @var{mode} @var{thread-id}
35558 @cindex thread information, remote request
35559 @cindex @samp{qP} packet
35560 Returns information on @var{thread-id}. Where: @var{mode} is a hex
35561 encoded 32 bit mode; @var{thread-id} is a thread ID
35562 (@pxref{thread-id syntax}).
35564 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
35567 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
35571 @cindex non-stop mode, remote request
35572 @cindex @samp{QNonStop} packet
35574 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
35575 @xref{Remote Non-Stop}, for more information.
35580 The request succeeded.
35583 An error occurred. The error number @var{nn} is given as hex digits.
35586 An empty reply indicates that @samp{QNonStop} is not supported by
35590 This packet is not probed by default; the remote stub must request it,
35591 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35592 Use of this packet is controlled by the @code{set non-stop} command;
35593 @pxref{Non-Stop Mode}.
35595 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
35596 @cindex pass signals to inferior, remote request
35597 @cindex @samp{QPassSignals} packet
35598 @anchor{QPassSignals}
35599 Each listed @var{signal} should be passed directly to the inferior process.
35600 Signals are numbered identically to continue packets and stop replies
35601 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
35602 strictly greater than the previous item. These signals do not need to stop
35603 the inferior, or be reported to @value{GDBN}. All other signals should be
35604 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
35605 combine; any earlier @samp{QPassSignals} list is completely replaced by the
35606 new list. This packet improves performance when using @samp{handle
35607 @var{signal} nostop noprint pass}.
35612 The request succeeded.
35615 An error occurred. The error number @var{nn} is given as hex digits.
35618 An empty reply indicates that @samp{QPassSignals} is not supported by
35622 Use of this packet is controlled by the @code{set remote pass-signals}
35623 command (@pxref{Remote Configuration, set remote pass-signals}).
35624 This packet is not probed by default; the remote stub must request it,
35625 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35627 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
35628 @cindex signals the inferior may see, remote request
35629 @cindex @samp{QProgramSignals} packet
35630 @anchor{QProgramSignals}
35631 Each listed @var{signal} may be delivered to the inferior process.
35632 Others should be silently discarded.
35634 In some cases, the remote stub may need to decide whether to deliver a
35635 signal to the program or not without @value{GDBN} involvement. One
35636 example of that is while detaching --- the program's threads may have
35637 stopped for signals that haven't yet had a chance of being reported to
35638 @value{GDBN}, and so the remote stub can use the signal list specified
35639 by this packet to know whether to deliver or ignore those pending
35642 This does not influence whether to deliver a signal as requested by a
35643 resumption packet (@pxref{vCont packet}).
35645 Signals are numbered identically to continue packets and stop replies
35646 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
35647 strictly greater than the previous item. Multiple
35648 @samp{QProgramSignals} packets do not combine; any earlier
35649 @samp{QProgramSignals} list is completely replaced by the new list.
35654 The request succeeded.
35657 An error occurred. The error number @var{nn} is given as hex digits.
35660 An empty reply indicates that @samp{QProgramSignals} is not supported
35664 Use of this packet is controlled by the @code{set remote program-signals}
35665 command (@pxref{Remote Configuration, set remote program-signals}).
35666 This packet is not probed by default; the remote stub must request it,
35667 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35669 @item qRcmd,@var{command}
35670 @cindex execute remote command, remote request
35671 @cindex @samp{qRcmd} packet
35672 @var{command} (hex encoded) is passed to the local interpreter for
35673 execution. Invalid commands should be reported using the output
35674 string. Before the final result packet, the target may also respond
35675 with a number of intermediate @samp{O@var{output}} console output
35676 packets. @emph{Implementors should note that providing access to a
35677 stubs's interpreter may have security implications}.
35682 A command response with no output.
35684 A command response with the hex encoded output string @var{OUTPUT}.
35686 Indicate a badly formed request.
35688 An empty reply indicates that @samp{qRcmd} is not recognized.
35691 (Note that the @code{qRcmd} packet's name is separated from the
35692 command by a @samp{,}, not a @samp{:}, contrary to the naming
35693 conventions above. Please don't use this packet as a model for new
35696 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
35697 @cindex searching memory, in remote debugging
35699 @cindex @samp{qSearch:memory} packet
35701 @cindex @samp{qSearch memory} packet
35702 @anchor{qSearch memory}
35703 Search @var{length} bytes at @var{address} for @var{search-pattern}.
35704 Both @var{address} and @var{length} are encoded in hex;
35705 @var{search-pattern} is a sequence of bytes, also hex encoded.
35710 The pattern was not found.
35712 The pattern was found at @var{address}.
35714 A badly formed request or an error was encountered while searching memory.
35716 An empty reply indicates that @samp{qSearch:memory} is not recognized.
35719 @item QStartNoAckMode
35720 @cindex @samp{QStartNoAckMode} packet
35721 @anchor{QStartNoAckMode}
35722 Request that the remote stub disable the normal @samp{+}/@samp{-}
35723 protocol acknowledgments (@pxref{Packet Acknowledgment}).
35728 The stub has switched to no-acknowledgment mode.
35729 @value{GDBN} acknowledges this reponse,
35730 but neither the stub nor @value{GDBN} shall send or expect further
35731 @samp{+}/@samp{-} acknowledgments in the current connection.
35733 An empty reply indicates that the stub does not support no-acknowledgment mode.
35736 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
35737 @cindex supported packets, remote query
35738 @cindex features of the remote protocol
35739 @cindex @samp{qSupported} packet
35740 @anchor{qSupported}
35741 Tell the remote stub about features supported by @value{GDBN}, and
35742 query the stub for features it supports. This packet allows
35743 @value{GDBN} and the remote stub to take advantage of each others'
35744 features. @samp{qSupported} also consolidates multiple feature probes
35745 at startup, to improve @value{GDBN} performance---a single larger
35746 packet performs better than multiple smaller probe packets on
35747 high-latency links. Some features may enable behavior which must not
35748 be on by default, e.g.@: because it would confuse older clients or
35749 stubs. Other features may describe packets which could be
35750 automatically probed for, but are not. These features must be
35751 reported before @value{GDBN} will use them. This ``default
35752 unsupported'' behavior is not appropriate for all packets, but it
35753 helps to keep the initial connection time under control with new
35754 versions of @value{GDBN} which support increasing numbers of packets.
35758 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
35759 The stub supports or does not support each returned @var{stubfeature},
35760 depending on the form of each @var{stubfeature} (see below for the
35763 An empty reply indicates that @samp{qSupported} is not recognized,
35764 or that no features needed to be reported to @value{GDBN}.
35767 The allowed forms for each feature (either a @var{gdbfeature} in the
35768 @samp{qSupported} packet, or a @var{stubfeature} in the response)
35772 @item @var{name}=@var{value}
35773 The remote protocol feature @var{name} is supported, and associated
35774 with the specified @var{value}. The format of @var{value} depends
35775 on the feature, but it must not include a semicolon.
35777 The remote protocol feature @var{name} is supported, and does not
35778 need an associated value.
35780 The remote protocol feature @var{name} is not supported.
35782 The remote protocol feature @var{name} may be supported, and
35783 @value{GDBN} should auto-detect support in some other way when it is
35784 needed. This form will not be used for @var{gdbfeature} notifications,
35785 but may be used for @var{stubfeature} responses.
35788 Whenever the stub receives a @samp{qSupported} request, the
35789 supplied set of @value{GDBN} features should override any previous
35790 request. This allows @value{GDBN} to put the stub in a known
35791 state, even if the stub had previously been communicating with
35792 a different version of @value{GDBN}.
35794 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
35799 This feature indicates whether @value{GDBN} supports multiprocess
35800 extensions to the remote protocol. @value{GDBN} does not use such
35801 extensions unless the stub also reports that it supports them by
35802 including @samp{multiprocess+} in its @samp{qSupported} reply.
35803 @xref{multiprocess extensions}, for details.
35806 This feature indicates that @value{GDBN} supports the XML target
35807 description. If the stub sees @samp{xmlRegisters=} with target
35808 specific strings separated by a comma, it will report register
35812 This feature indicates whether @value{GDBN} supports the
35813 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
35814 instruction reply packet}).
35817 This feature indicates whether @value{GDBN} supports the swbreak stop
35818 reason in stop replies. @xref{swbreak stop reason}, for details.
35821 This feature indicates whether @value{GDBN} supports the hwbreak stop
35822 reason in stop replies. @xref{swbreak stop reason}, for details.
35825 Stubs should ignore any unknown values for
35826 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
35827 packet supports receiving packets of unlimited length (earlier
35828 versions of @value{GDBN} may reject overly long responses). Additional values
35829 for @var{gdbfeature} may be defined in the future to let the stub take
35830 advantage of new features in @value{GDBN}, e.g.@: incompatible
35831 improvements in the remote protocol---the @samp{multiprocess} feature is
35832 an example of such a feature. The stub's reply should be independent
35833 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
35834 describes all the features it supports, and then the stub replies with
35835 all the features it supports.
35837 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
35838 responses, as long as each response uses one of the standard forms.
35840 Some features are flags. A stub which supports a flag feature
35841 should respond with a @samp{+} form response. Other features
35842 require values, and the stub should respond with an @samp{=}
35845 Each feature has a default value, which @value{GDBN} will use if
35846 @samp{qSupported} is not available or if the feature is not mentioned
35847 in the @samp{qSupported} response. The default values are fixed; a
35848 stub is free to omit any feature responses that match the defaults.
35850 Not all features can be probed, but for those which can, the probing
35851 mechanism is useful: in some cases, a stub's internal
35852 architecture may not allow the protocol layer to know some information
35853 about the underlying target in advance. This is especially common in
35854 stubs which may be configured for multiple targets.
35856 These are the currently defined stub features and their properties:
35858 @multitable @columnfractions 0.35 0.2 0.12 0.2
35859 @c NOTE: The first row should be @headitem, but we do not yet require
35860 @c a new enough version of Texinfo (4.7) to use @headitem.
35862 @tab Value Required
35866 @item @samp{PacketSize}
35871 @item @samp{qXfer:auxv:read}
35876 @item @samp{qXfer:btrace:read}
35881 @item @samp{qXfer:btrace-conf:read}
35886 @item @samp{qXfer:features:read}
35891 @item @samp{qXfer:libraries:read}
35896 @item @samp{qXfer:libraries-svr4:read}
35901 @item @samp{augmented-libraries-svr4-read}
35906 @item @samp{qXfer:memory-map:read}
35911 @item @samp{qXfer:sdata:read}
35916 @item @samp{qXfer:spu:read}
35921 @item @samp{qXfer:spu:write}
35926 @item @samp{qXfer:siginfo:read}
35931 @item @samp{qXfer:siginfo:write}
35936 @item @samp{qXfer:threads:read}
35941 @item @samp{qXfer:traceframe-info:read}
35946 @item @samp{qXfer:uib:read}
35951 @item @samp{qXfer:fdpic:read}
35956 @item @samp{Qbtrace:off}
35961 @item @samp{Qbtrace:bts}
35966 @item @samp{Qbtrace-conf:bts:size}
35971 @item @samp{QNonStop}
35976 @item @samp{QPassSignals}
35981 @item @samp{QStartNoAckMode}
35986 @item @samp{multiprocess}
35991 @item @samp{ConditionalBreakpoints}
35996 @item @samp{ConditionalTracepoints}
36001 @item @samp{ReverseContinue}
36006 @item @samp{ReverseStep}
36011 @item @samp{TracepointSource}
36016 @item @samp{QAgent}
36021 @item @samp{QAllow}
36026 @item @samp{QDisableRandomization}
36031 @item @samp{EnableDisableTracepoints}
36036 @item @samp{QTBuffer:size}
36041 @item @samp{tracenz}
36046 @item @samp{BreakpointCommands}
36051 @item @samp{swbreak}
36056 @item @samp{hwbreak}
36063 These are the currently defined stub features, in more detail:
36066 @cindex packet size, remote protocol
36067 @item PacketSize=@var{bytes}
36068 The remote stub can accept packets up to at least @var{bytes} in
36069 length. @value{GDBN} will send packets up to this size for bulk
36070 transfers, and will never send larger packets. This is a limit on the
36071 data characters in the packet, including the frame and checksum.
36072 There is no trailing NUL byte in a remote protocol packet; if the stub
36073 stores packets in a NUL-terminated format, it should allow an extra
36074 byte in its buffer for the NUL. If this stub feature is not supported,
36075 @value{GDBN} guesses based on the size of the @samp{g} packet response.
36077 @item qXfer:auxv:read
36078 The remote stub understands the @samp{qXfer:auxv:read} packet
36079 (@pxref{qXfer auxiliary vector read}).
36081 @item qXfer:btrace:read
36082 The remote stub understands the @samp{qXfer:btrace:read}
36083 packet (@pxref{qXfer btrace read}).
36085 @item qXfer:btrace-conf:read
36086 The remote stub understands the @samp{qXfer:btrace-conf:read}
36087 packet (@pxref{qXfer btrace-conf read}).
36089 @item qXfer:features:read
36090 The remote stub understands the @samp{qXfer:features:read} packet
36091 (@pxref{qXfer target description read}).
36093 @item qXfer:libraries:read
36094 The remote stub understands the @samp{qXfer:libraries:read} packet
36095 (@pxref{qXfer library list read}).
36097 @item qXfer:libraries-svr4:read
36098 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
36099 (@pxref{qXfer svr4 library list read}).
36101 @item augmented-libraries-svr4-read
36102 The remote stub understands the augmented form of the
36103 @samp{qXfer:libraries-svr4:read} packet
36104 (@pxref{qXfer svr4 library list read}).
36106 @item qXfer:memory-map:read
36107 The remote stub understands the @samp{qXfer:memory-map:read} packet
36108 (@pxref{qXfer memory map read}).
36110 @item qXfer:sdata:read
36111 The remote stub understands the @samp{qXfer:sdata:read} packet
36112 (@pxref{qXfer sdata read}).
36114 @item qXfer:spu:read
36115 The remote stub understands the @samp{qXfer:spu:read} packet
36116 (@pxref{qXfer spu read}).
36118 @item qXfer:spu:write
36119 The remote stub understands the @samp{qXfer:spu:write} packet
36120 (@pxref{qXfer spu write}).
36122 @item qXfer:siginfo:read
36123 The remote stub understands the @samp{qXfer:siginfo:read} packet
36124 (@pxref{qXfer siginfo read}).
36126 @item qXfer:siginfo:write
36127 The remote stub understands the @samp{qXfer:siginfo:write} packet
36128 (@pxref{qXfer siginfo write}).
36130 @item qXfer:threads:read
36131 The remote stub understands the @samp{qXfer:threads:read} packet
36132 (@pxref{qXfer threads read}).
36134 @item qXfer:traceframe-info:read
36135 The remote stub understands the @samp{qXfer:traceframe-info:read}
36136 packet (@pxref{qXfer traceframe info read}).
36138 @item qXfer:uib:read
36139 The remote stub understands the @samp{qXfer:uib:read}
36140 packet (@pxref{qXfer unwind info block}).
36142 @item qXfer:fdpic:read
36143 The remote stub understands the @samp{qXfer:fdpic:read}
36144 packet (@pxref{qXfer fdpic loadmap read}).
36147 The remote stub understands the @samp{QNonStop} packet
36148 (@pxref{QNonStop}).
36151 The remote stub understands the @samp{QPassSignals} packet
36152 (@pxref{QPassSignals}).
36154 @item QStartNoAckMode
36155 The remote stub understands the @samp{QStartNoAckMode} packet and
36156 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
36159 @anchor{multiprocess extensions}
36160 @cindex multiprocess extensions, in remote protocol
36161 The remote stub understands the multiprocess extensions to the remote
36162 protocol syntax. The multiprocess extensions affect the syntax of
36163 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
36164 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
36165 replies. Note that reporting this feature indicates support for the
36166 syntactic extensions only, not that the stub necessarily supports
36167 debugging of more than one process at a time. The stub must not use
36168 multiprocess extensions in packet replies unless @value{GDBN} has also
36169 indicated it supports them in its @samp{qSupported} request.
36171 @item qXfer:osdata:read
36172 The remote stub understands the @samp{qXfer:osdata:read} packet
36173 ((@pxref{qXfer osdata read}).
36175 @item ConditionalBreakpoints
36176 The target accepts and implements evaluation of conditional expressions
36177 defined for breakpoints. The target will only report breakpoint triggers
36178 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
36180 @item ConditionalTracepoints
36181 The remote stub accepts and implements conditional expressions defined
36182 for tracepoints (@pxref{Tracepoint Conditions}).
36184 @item ReverseContinue
36185 The remote stub accepts and implements the reverse continue packet
36189 The remote stub accepts and implements the reverse step packet
36192 @item TracepointSource
36193 The remote stub understands the @samp{QTDPsrc} packet that supplies
36194 the source form of tracepoint definitions.
36197 The remote stub understands the @samp{QAgent} packet.
36200 The remote stub understands the @samp{QAllow} packet.
36202 @item QDisableRandomization
36203 The remote stub understands the @samp{QDisableRandomization} packet.
36205 @item StaticTracepoint
36206 @cindex static tracepoints, in remote protocol
36207 The remote stub supports static tracepoints.
36209 @item InstallInTrace
36210 @anchor{install tracepoint in tracing}
36211 The remote stub supports installing tracepoint in tracing.
36213 @item EnableDisableTracepoints
36214 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
36215 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
36216 to be enabled and disabled while a trace experiment is running.
36218 @item QTBuffer:size
36219 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
36220 packet that allows to change the size of the trace buffer.
36223 @cindex string tracing, in remote protocol
36224 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
36225 See @ref{Bytecode Descriptions} for details about the bytecode.
36227 @item BreakpointCommands
36228 @cindex breakpoint commands, in remote protocol
36229 The remote stub supports running a breakpoint's command list itself,
36230 rather than reporting the hit to @value{GDBN}.
36233 The remote stub understands the @samp{Qbtrace:off} packet.
36236 The remote stub understands the @samp{Qbtrace:bts} packet.
36238 @item Qbtrace-conf:bts:size
36239 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
36242 The remote stub reports the @samp{swbreak} stop reason for memory
36246 The remote stub reports the @samp{hwbreak} stop reason for hardware
36252 @cindex symbol lookup, remote request
36253 @cindex @samp{qSymbol} packet
36254 Notify the target that @value{GDBN} is prepared to serve symbol lookup
36255 requests. Accept requests from the target for the values of symbols.
36260 The target does not need to look up any (more) symbols.
36261 @item qSymbol:@var{sym_name}
36262 The target requests the value of symbol @var{sym_name} (hex encoded).
36263 @value{GDBN} may provide the value by using the
36264 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
36268 @item qSymbol:@var{sym_value}:@var{sym_name}
36269 Set the value of @var{sym_name} to @var{sym_value}.
36271 @var{sym_name} (hex encoded) is the name of a symbol whose value the
36272 target has previously requested.
36274 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
36275 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
36281 The target does not need to look up any (more) symbols.
36282 @item qSymbol:@var{sym_name}
36283 The target requests the value of a new symbol @var{sym_name} (hex
36284 encoded). @value{GDBN} will continue to supply the values of symbols
36285 (if available), until the target ceases to request them.
36290 @itemx QTDisconnected
36297 @itemx qTMinFTPILen
36299 @xref{Tracepoint Packets}.
36301 @item qThreadExtraInfo,@var{thread-id}
36302 @cindex thread attributes info, remote request
36303 @cindex @samp{qThreadExtraInfo} packet
36304 Obtain from the target OS a printable string description of thread
36305 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
36306 for the forms of @var{thread-id}. This
36307 string may contain anything that the target OS thinks is interesting
36308 for @value{GDBN} to tell the user about the thread. The string is
36309 displayed in @value{GDBN}'s @code{info threads} display. Some
36310 examples of possible thread extra info strings are @samp{Runnable}, or
36311 @samp{Blocked on Mutex}.
36315 @item @var{XX}@dots{}
36316 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
36317 comprising the printable string containing the extra information about
36318 the thread's attributes.
36321 (Note that the @code{qThreadExtraInfo} packet's name is separated from
36322 the command by a @samp{,}, not a @samp{:}, contrary to the naming
36323 conventions above. Please don't use this packet as a model for new
36342 @xref{Tracepoint Packets}.
36344 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
36345 @cindex read special object, remote request
36346 @cindex @samp{qXfer} packet
36347 @anchor{qXfer read}
36348 Read uninterpreted bytes from the target's special data area
36349 identified by the keyword @var{object}. Request @var{length} bytes
36350 starting at @var{offset} bytes into the data. The content and
36351 encoding of @var{annex} is specific to @var{object}; it can supply
36352 additional details about what data to access.
36354 Here are the specific requests of this form defined so far. All
36355 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
36356 formats, listed below.
36359 @item qXfer:auxv:read::@var{offset},@var{length}
36360 @anchor{qXfer auxiliary vector read}
36361 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
36362 auxiliary vector}. Note @var{annex} must be empty.
36364 This packet is not probed by default; the remote stub must request it,
36365 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36367 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
36368 @anchor{qXfer btrace read}
36370 Return a description of the current branch trace.
36371 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
36372 packet may have one of the following values:
36376 Returns all available branch trace.
36379 Returns all available branch trace if the branch trace changed since
36380 the last read request.
36383 Returns the new branch trace since the last read request. Adds a new
36384 block to the end of the trace that begins at zero and ends at the source
36385 location of the first branch in the trace buffer. This extra block is
36386 used to stitch traces together.
36388 If the trace buffer overflowed, returns an error indicating the overflow.
36391 This packet is not probed by default; the remote stub must request it
36392 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36394 @item qXfer:btrace-conf:read::@var{offset},@var{length}
36395 @anchor{qXfer btrace-conf read}
36397 Return a description of the current branch trace configuration.
36398 @xref{Branch Trace Configuration Format}.
36400 This packet is not probed by default; the remote stub must request it
36401 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36403 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
36404 @anchor{qXfer target description read}
36405 Access the @dfn{target description}. @xref{Target Descriptions}. The
36406 annex specifies which XML document to access. The main description is
36407 always loaded from the @samp{target.xml} annex.
36409 This packet is not probed by default; the remote stub must request it,
36410 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36412 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
36413 @anchor{qXfer library list read}
36414 Access the target's list of loaded libraries. @xref{Library List Format}.
36415 The annex part of the generic @samp{qXfer} packet must be empty
36416 (@pxref{qXfer read}).
36418 Targets which maintain a list of libraries in the program's memory do
36419 not need to implement this packet; it is designed for platforms where
36420 the operating system manages the list of loaded libraries.
36422 This packet is not probed by default; the remote stub must request it,
36423 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36425 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
36426 @anchor{qXfer svr4 library list read}
36427 Access the target's list of loaded libraries when the target is an SVR4
36428 platform. @xref{Library List Format for SVR4 Targets}. The annex part
36429 of the generic @samp{qXfer} packet must be empty unless the remote
36430 stub indicated it supports the augmented form of this packet
36431 by supplying an appropriate @samp{qSupported} response
36432 (@pxref{qXfer read}, @ref{qSupported}).
36434 This packet is optional for better performance on SVR4 targets.
36435 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
36437 This packet is not probed by default; the remote stub must request it,
36438 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36440 If the remote stub indicates it supports the augmented form of this
36441 packet then the annex part of the generic @samp{qXfer} packet may
36442 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
36443 arguments. The currently supported arguments are:
36446 @item start=@var{address}
36447 A hexadecimal number specifying the address of the @samp{struct
36448 link_map} to start reading the library list from. If unset or zero
36449 then the first @samp{struct link_map} in the library list will be
36450 chosen as the starting point.
36452 @item prev=@var{address}
36453 A hexadecimal number specifying the address of the @samp{struct
36454 link_map} immediately preceding the @samp{struct link_map}
36455 specified by the @samp{start} argument. If unset or zero then
36456 the remote stub will expect that no @samp{struct link_map}
36457 exists prior to the starting point.
36461 Arguments that are not understood by the remote stub will be silently
36464 @item qXfer:memory-map:read::@var{offset},@var{length}
36465 @anchor{qXfer memory map read}
36466 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
36467 annex part of the generic @samp{qXfer} packet must be empty
36468 (@pxref{qXfer read}).
36470 This packet is not probed by default; the remote stub must request it,
36471 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36473 @item qXfer:sdata:read::@var{offset},@var{length}
36474 @anchor{qXfer sdata read}
36476 Read contents of the extra collected static tracepoint marker
36477 information. The annex part of the generic @samp{qXfer} packet must
36478 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
36481 This packet is not probed by default; the remote stub must request it,
36482 by supplying an appropriate @samp{qSupported} response
36483 (@pxref{qSupported}).
36485 @item qXfer:siginfo:read::@var{offset},@var{length}
36486 @anchor{qXfer siginfo read}
36487 Read contents of the extra signal information on the target
36488 system. The annex part of the generic @samp{qXfer} packet must be
36489 empty (@pxref{qXfer read}).
36491 This packet is not probed by default; the remote stub must request it,
36492 by supplying an appropriate @samp{qSupported} response
36493 (@pxref{qSupported}).
36495 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
36496 @anchor{qXfer spu read}
36497 Read contents of an @code{spufs} file on the target system. The
36498 annex specifies which file to read; it must be of the form
36499 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
36500 in the target process, and @var{name} identifes the @code{spufs} file
36501 in that context to be accessed.
36503 This packet is not probed by default; the remote stub must request it,
36504 by supplying an appropriate @samp{qSupported} response
36505 (@pxref{qSupported}).
36507 @item qXfer:threads:read::@var{offset},@var{length}
36508 @anchor{qXfer threads read}
36509 Access the list of threads on target. @xref{Thread List Format}. The
36510 annex part of the generic @samp{qXfer} packet must be empty
36511 (@pxref{qXfer read}).
36513 This packet is not probed by default; the remote stub must request it,
36514 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36516 @item qXfer:traceframe-info:read::@var{offset},@var{length}
36517 @anchor{qXfer traceframe info read}
36519 Return a description of the current traceframe's contents.
36520 @xref{Traceframe Info Format}. The annex part of the generic
36521 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
36523 This packet is not probed by default; the remote stub must request it,
36524 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36526 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
36527 @anchor{qXfer unwind info block}
36529 Return the unwind information block for @var{pc}. This packet is used
36530 on OpenVMS/ia64 to ask the kernel unwind information.
36532 This packet is not probed by default.
36534 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
36535 @anchor{qXfer fdpic loadmap read}
36536 Read contents of @code{loadmap}s on the target system. The
36537 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
36538 executable @code{loadmap} or interpreter @code{loadmap} to read.
36540 This packet is not probed by default; the remote stub must request it,
36541 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36543 @item qXfer:osdata:read::@var{offset},@var{length}
36544 @anchor{qXfer osdata read}
36545 Access the target's @dfn{operating system information}.
36546 @xref{Operating System Information}.
36553 Data @var{data} (@pxref{Binary Data}) has been read from the
36554 target. There may be more data at a higher address (although
36555 it is permitted to return @samp{m} even for the last valid
36556 block of data, as long as at least one byte of data was read).
36557 It is possible for @var{data} to have fewer bytes than the @var{length} in the
36561 Data @var{data} (@pxref{Binary Data}) has been read from the target.
36562 There is no more data to be read. It is possible for @var{data} to
36563 have fewer bytes than the @var{length} in the request.
36566 The @var{offset} in the request is at the end of the data.
36567 There is no more data to be read.
36570 The request was malformed, or @var{annex} was invalid.
36573 The offset was invalid, or there was an error encountered reading the data.
36574 The @var{nn} part is a hex-encoded @code{errno} value.
36577 An empty reply indicates the @var{object} string was not recognized by
36578 the stub, or that the object does not support reading.
36581 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
36582 @cindex write data into object, remote request
36583 @anchor{qXfer write}
36584 Write uninterpreted bytes into the target's special data area
36585 identified by the keyword @var{object}, starting at @var{offset} bytes
36586 into the data. The binary-encoded data (@pxref{Binary Data}) to be
36587 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
36588 is specific to @var{object}; it can supply additional details about what data
36591 Here are the specific requests of this form defined so far. All
36592 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
36593 formats, listed below.
36596 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
36597 @anchor{qXfer siginfo write}
36598 Write @var{data} to the extra signal information on the target system.
36599 The annex part of the generic @samp{qXfer} packet must be
36600 empty (@pxref{qXfer write}).
36602 This packet is not probed by default; the remote stub must request it,
36603 by supplying an appropriate @samp{qSupported} response
36604 (@pxref{qSupported}).
36606 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
36607 @anchor{qXfer spu write}
36608 Write @var{data} to an @code{spufs} file on the target system. The
36609 annex specifies which file to write; it must be of the form
36610 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
36611 in the target process, and @var{name} identifes the @code{spufs} file
36612 in that context to be accessed.
36614 This packet is not probed by default; the remote stub must request it,
36615 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36621 @var{nn} (hex encoded) is the number of bytes written.
36622 This may be fewer bytes than supplied in the request.
36625 The request was malformed, or @var{annex} was invalid.
36628 The offset was invalid, or there was an error encountered writing the data.
36629 The @var{nn} part is a hex-encoded @code{errno} value.
36632 An empty reply indicates the @var{object} string was not
36633 recognized by the stub, or that the object does not support writing.
36636 @item qXfer:@var{object}:@var{operation}:@dots{}
36637 Requests of this form may be added in the future. When a stub does
36638 not recognize the @var{object} keyword, or its support for
36639 @var{object} does not recognize the @var{operation} keyword, the stub
36640 must respond with an empty packet.
36642 @item qAttached:@var{pid}
36643 @cindex query attached, remote request
36644 @cindex @samp{qAttached} packet
36645 Return an indication of whether the remote server attached to an
36646 existing process or created a new process. When the multiprocess
36647 protocol extensions are supported (@pxref{multiprocess extensions}),
36648 @var{pid} is an integer in hexadecimal format identifying the target
36649 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
36650 the query packet will be simplified as @samp{qAttached}.
36652 This query is used, for example, to know whether the remote process
36653 should be detached or killed when a @value{GDBN} session is ended with
36654 the @code{quit} command.
36659 The remote server attached to an existing process.
36661 The remote server created a new process.
36663 A badly formed request or an error was encountered.
36667 Enable branch tracing for the current thread using bts tracing.
36672 Branch tracing has been enabled.
36674 A badly formed request or an error was encountered.
36678 Disable branch tracing for the current thread.
36683 Branch tracing has been disabled.
36685 A badly formed request or an error was encountered.
36688 @item Qbtrace-conf:bts:size=@var{value}
36689 Set the requested ring buffer size for new threads that use the
36690 btrace recording method in bts format.
36695 The ring buffer size has been set.
36697 A badly formed request or an error was encountered.
36702 @node Architecture-Specific Protocol Details
36703 @section Architecture-Specific Protocol Details
36705 This section describes how the remote protocol is applied to specific
36706 target architectures. Also see @ref{Standard Target Features}, for
36707 details of XML target descriptions for each architecture.
36710 * ARM-Specific Protocol Details::
36711 * MIPS-Specific Protocol Details::
36714 @node ARM-Specific Protocol Details
36715 @subsection @acronym{ARM}-specific Protocol Details
36718 * ARM Breakpoint Kinds::
36721 @node ARM Breakpoint Kinds
36722 @subsubsection @acronym{ARM} Breakpoint Kinds
36723 @cindex breakpoint kinds, @acronym{ARM}
36725 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
36730 16-bit Thumb mode breakpoint.
36733 32-bit Thumb mode (Thumb-2) breakpoint.
36736 32-bit @acronym{ARM} mode breakpoint.
36740 @node MIPS-Specific Protocol Details
36741 @subsection @acronym{MIPS}-specific Protocol Details
36744 * MIPS Register packet Format::
36745 * MIPS Breakpoint Kinds::
36748 @node MIPS Register packet Format
36749 @subsubsection @acronym{MIPS} Register Packet Format
36750 @cindex register packet format, @acronym{MIPS}
36752 The following @code{g}/@code{G} packets have previously been defined.
36753 In the below, some thirty-two bit registers are transferred as
36754 sixty-four bits. Those registers should be zero/sign extended (which?)
36755 to fill the space allocated. Register bytes are transferred in target
36756 byte order. The two nibbles within a register byte are transferred
36757 most-significant -- least-significant.
36762 All registers are transferred as thirty-two bit quantities in the order:
36763 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
36764 registers; fsr; fir; fp.
36767 All registers are transferred as sixty-four bit quantities (including
36768 thirty-two bit registers such as @code{sr}). The ordering is the same
36773 @node MIPS Breakpoint Kinds
36774 @subsubsection @acronym{MIPS} Breakpoint Kinds
36775 @cindex breakpoint kinds, @acronym{MIPS}
36777 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
36782 16-bit @acronym{MIPS16} mode breakpoint.
36785 16-bit @acronym{microMIPS} mode breakpoint.
36788 32-bit standard @acronym{MIPS} mode breakpoint.
36791 32-bit @acronym{microMIPS} mode breakpoint.
36795 @node Tracepoint Packets
36796 @section Tracepoint Packets
36797 @cindex tracepoint packets
36798 @cindex packets, tracepoint
36800 Here we describe the packets @value{GDBN} uses to implement
36801 tracepoints (@pxref{Tracepoints}).
36805 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
36806 @cindex @samp{QTDP} packet
36807 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
36808 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
36809 the tracepoint is disabled. The @var{step} gives the tracepoint's step
36810 count, and @var{pass} gives its pass count. If an @samp{F} is present,
36811 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
36812 the number of bytes that the target should copy elsewhere to make room
36813 for the tracepoint. If an @samp{X} is present, it introduces a
36814 tracepoint condition, which consists of a hexadecimal length, followed
36815 by a comma and hex-encoded bytes, in a manner similar to action
36816 encodings as described below. If the trailing @samp{-} is present,
36817 further @samp{QTDP} packets will follow to specify this tracepoint's
36823 The packet was understood and carried out.
36825 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
36827 The packet was not recognized.
36830 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
36831 Define actions to be taken when a tracepoint is hit. The @var{n} and
36832 @var{addr} must be the same as in the initial @samp{QTDP} packet for
36833 this tracepoint. This packet may only be sent immediately after
36834 another @samp{QTDP} packet that ended with a @samp{-}. If the
36835 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
36836 specifying more actions for this tracepoint.
36838 In the series of action packets for a given tracepoint, at most one
36839 can have an @samp{S} before its first @var{action}. If such a packet
36840 is sent, it and the following packets define ``while-stepping''
36841 actions. Any prior packets define ordinary actions --- that is, those
36842 taken when the tracepoint is first hit. If no action packet has an
36843 @samp{S}, then all the packets in the series specify ordinary
36844 tracepoint actions.
36846 The @samp{@var{action}@dots{}} portion of the packet is a series of
36847 actions, concatenated without separators. Each action has one of the
36853 Collect the registers whose bits are set in @var{mask},
36854 a hexadecimal number whose @var{i}'th bit is set if register number
36855 @var{i} should be collected. (The least significant bit is numbered
36856 zero.) Note that @var{mask} may be any number of digits long; it may
36857 not fit in a 32-bit word.
36859 @item M @var{basereg},@var{offset},@var{len}
36860 Collect @var{len} bytes of memory starting at the address in register
36861 number @var{basereg}, plus @var{offset}. If @var{basereg} is
36862 @samp{-1}, then the range has a fixed address: @var{offset} is the
36863 address of the lowest byte to collect. The @var{basereg},
36864 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
36865 values (the @samp{-1} value for @var{basereg} is a special case).
36867 @item X @var{len},@var{expr}
36868 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
36869 it directs. The agent expression @var{expr} is as described in
36870 @ref{Agent Expressions}. Each byte of the expression is encoded as a
36871 two-digit hex number in the packet; @var{len} is the number of bytes
36872 in the expression (and thus one-half the number of hex digits in the
36877 Any number of actions may be packed together in a single @samp{QTDP}
36878 packet, as long as the packet does not exceed the maximum packet
36879 length (400 bytes, for many stubs). There may be only one @samp{R}
36880 action per tracepoint, and it must precede any @samp{M} or @samp{X}
36881 actions. Any registers referred to by @samp{M} and @samp{X} actions
36882 must be collected by a preceding @samp{R} action. (The
36883 ``while-stepping'' actions are treated as if they were attached to a
36884 separate tracepoint, as far as these restrictions are concerned.)
36889 The packet was understood and carried out.
36891 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
36893 The packet was not recognized.
36896 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
36897 @cindex @samp{QTDPsrc} packet
36898 Specify a source string of tracepoint @var{n} at address @var{addr}.
36899 This is useful to get accurate reproduction of the tracepoints
36900 originally downloaded at the beginning of the trace run. The @var{type}
36901 is the name of the tracepoint part, such as @samp{cond} for the
36902 tracepoint's conditional expression (see below for a list of types), while
36903 @var{bytes} is the string, encoded in hexadecimal.
36905 @var{start} is the offset of the @var{bytes} within the overall source
36906 string, while @var{slen} is the total length of the source string.
36907 This is intended for handling source strings that are longer than will
36908 fit in a single packet.
36909 @c Add detailed example when this info is moved into a dedicated
36910 @c tracepoint descriptions section.
36912 The available string types are @samp{at} for the location,
36913 @samp{cond} for the conditional, and @samp{cmd} for an action command.
36914 @value{GDBN} sends a separate packet for each command in the action
36915 list, in the same order in which the commands are stored in the list.
36917 The target does not need to do anything with source strings except
36918 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
36921 Although this packet is optional, and @value{GDBN} will only send it
36922 if the target replies with @samp{TracepointSource} @xref{General
36923 Query Packets}, it makes both disconnected tracing and trace files
36924 much easier to use. Otherwise the user must be careful that the
36925 tracepoints in effect while looking at trace frames are identical to
36926 the ones in effect during the trace run; even a small discrepancy
36927 could cause @samp{tdump} not to work, or a particular trace frame not
36930 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
36931 @cindex define trace state variable, remote request
36932 @cindex @samp{QTDV} packet
36933 Create a new trace state variable, number @var{n}, with an initial
36934 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
36935 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
36936 the option of not using this packet for initial values of zero; the
36937 target should simply create the trace state variables as they are
36938 mentioned in expressions. The value @var{builtin} should be 1 (one)
36939 if the trace state variable is builtin and 0 (zero) if it is not builtin.
36940 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
36941 @samp{qTsV} packet had it set. The contents of @var{name} is the
36942 hex-encoded name (without the leading @samp{$}) of the trace state
36945 @item QTFrame:@var{n}
36946 @cindex @samp{QTFrame} packet
36947 Select the @var{n}'th tracepoint frame from the buffer, and use the
36948 register and memory contents recorded there to answer subsequent
36949 request packets from @value{GDBN}.
36951 A successful reply from the stub indicates that the stub has found the
36952 requested frame. The response is a series of parts, concatenated
36953 without separators, describing the frame we selected. Each part has
36954 one of the following forms:
36958 The selected frame is number @var{n} in the trace frame buffer;
36959 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
36960 was no frame matching the criteria in the request packet.
36963 The selected trace frame records a hit of tracepoint number @var{t};
36964 @var{t} is a hexadecimal number.
36968 @item QTFrame:pc:@var{addr}
36969 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
36970 currently selected frame whose PC is @var{addr};
36971 @var{addr} is a hexadecimal number.
36973 @item QTFrame:tdp:@var{t}
36974 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
36975 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
36976 is a hexadecimal number.
36978 @item QTFrame:range:@var{start}:@var{end}
36979 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
36980 currently selected frame whose PC is between @var{start} (inclusive)
36981 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
36984 @item QTFrame:outside:@var{start}:@var{end}
36985 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
36986 frame @emph{outside} the given range of addresses (exclusive).
36989 @cindex @samp{qTMinFTPILen} packet
36990 This packet requests the minimum length of instruction at which a fast
36991 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
36992 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
36993 it depends on the target system being able to create trampolines in
36994 the first 64K of memory, which might or might not be possible for that
36995 system. So the reply to this packet will be 4 if it is able to
37002 The minimum instruction length is currently unknown.
37004 The minimum instruction length is @var{length}, where @var{length}
37005 is a hexadecimal number greater or equal to 1. A reply
37006 of 1 means that a fast tracepoint may be placed on any instruction
37007 regardless of size.
37009 An error has occurred.
37011 An empty reply indicates that the request is not supported by the stub.
37015 @cindex @samp{QTStart} packet
37016 Begin the tracepoint experiment. Begin collecting data from
37017 tracepoint hits in the trace frame buffer. This packet supports the
37018 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
37019 instruction reply packet}).
37022 @cindex @samp{QTStop} packet
37023 End the tracepoint experiment. Stop collecting trace frames.
37025 @item QTEnable:@var{n}:@var{addr}
37027 @cindex @samp{QTEnable} packet
37028 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
37029 experiment. If the tracepoint was previously disabled, then collection
37030 of data from it will resume.
37032 @item QTDisable:@var{n}:@var{addr}
37034 @cindex @samp{QTDisable} packet
37035 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
37036 experiment. No more data will be collected from the tracepoint unless
37037 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
37040 @cindex @samp{QTinit} packet
37041 Clear the table of tracepoints, and empty the trace frame buffer.
37043 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
37044 @cindex @samp{QTro} packet
37045 Establish the given ranges of memory as ``transparent''. The stub
37046 will answer requests for these ranges from memory's current contents,
37047 if they were not collected as part of the tracepoint hit.
37049 @value{GDBN} uses this to mark read-only regions of memory, like those
37050 containing program code. Since these areas never change, they should
37051 still have the same contents they did when the tracepoint was hit, so
37052 there's no reason for the stub to refuse to provide their contents.
37054 @item QTDisconnected:@var{value}
37055 @cindex @samp{QTDisconnected} packet
37056 Set the choice to what to do with the tracing run when @value{GDBN}
37057 disconnects from the target. A @var{value} of 1 directs the target to
37058 continue the tracing run, while 0 tells the target to stop tracing if
37059 @value{GDBN} is no longer in the picture.
37062 @cindex @samp{qTStatus} packet
37063 Ask the stub if there is a trace experiment running right now.
37065 The reply has the form:
37069 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
37070 @var{running} is a single digit @code{1} if the trace is presently
37071 running, or @code{0} if not. It is followed by semicolon-separated
37072 optional fields that an agent may use to report additional status.
37076 If the trace is not running, the agent may report any of several
37077 explanations as one of the optional fields:
37082 No trace has been run yet.
37084 @item tstop[:@var{text}]:0
37085 The trace was stopped by a user-originated stop command. The optional
37086 @var{text} field is a user-supplied string supplied as part of the
37087 stop command (for instance, an explanation of why the trace was
37088 stopped manually). It is hex-encoded.
37091 The trace stopped because the trace buffer filled up.
37093 @item tdisconnected:0
37094 The trace stopped because @value{GDBN} disconnected from the target.
37096 @item tpasscount:@var{tpnum}
37097 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
37099 @item terror:@var{text}:@var{tpnum}
37100 The trace stopped because tracepoint @var{tpnum} had an error. The
37101 string @var{text} is available to describe the nature of the error
37102 (for instance, a divide by zero in the condition expression); it
37106 The trace stopped for some other reason.
37110 Additional optional fields supply statistical and other information.
37111 Although not required, they are extremely useful for users monitoring
37112 the progress of a trace run. If a trace has stopped, and these
37113 numbers are reported, they must reflect the state of the just-stopped
37118 @item tframes:@var{n}
37119 The number of trace frames in the buffer.
37121 @item tcreated:@var{n}
37122 The total number of trace frames created during the run. This may
37123 be larger than the trace frame count, if the buffer is circular.
37125 @item tsize:@var{n}
37126 The total size of the trace buffer, in bytes.
37128 @item tfree:@var{n}
37129 The number of bytes still unused in the buffer.
37131 @item circular:@var{n}
37132 The value of the circular trace buffer flag. @code{1} means that the
37133 trace buffer is circular and old trace frames will be discarded if
37134 necessary to make room, @code{0} means that the trace buffer is linear
37137 @item disconn:@var{n}
37138 The value of the disconnected tracing flag. @code{1} means that
37139 tracing will continue after @value{GDBN} disconnects, @code{0} means
37140 that the trace run will stop.
37144 @item qTP:@var{tp}:@var{addr}
37145 @cindex tracepoint status, remote request
37146 @cindex @samp{qTP} packet
37147 Ask the stub for the current state of tracepoint number @var{tp} at
37148 address @var{addr}.
37152 @item V@var{hits}:@var{usage}
37153 The tracepoint has been hit @var{hits} times so far during the trace
37154 run, and accounts for @var{usage} in the trace buffer. Note that
37155 @code{while-stepping} steps are not counted as separate hits, but the
37156 steps' space consumption is added into the usage number.
37160 @item qTV:@var{var}
37161 @cindex trace state variable value, remote request
37162 @cindex @samp{qTV} packet
37163 Ask the stub for the value of the trace state variable number @var{var}.
37168 The value of the variable is @var{value}. This will be the current
37169 value of the variable if the user is examining a running target, or a
37170 saved value if the variable was collected in the trace frame that the
37171 user is looking at. Note that multiple requests may result in
37172 different reply values, such as when requesting values while the
37173 program is running.
37176 The value of the variable is unknown. This would occur, for example,
37177 if the user is examining a trace frame in which the requested variable
37182 @cindex @samp{qTfP} packet
37184 @cindex @samp{qTsP} packet
37185 These packets request data about tracepoints that are being used by
37186 the target. @value{GDBN} sends @code{qTfP} to get the first piece
37187 of data, and multiple @code{qTsP} to get additional pieces. Replies
37188 to these packets generally take the form of the @code{QTDP} packets
37189 that define tracepoints. (FIXME add detailed syntax)
37192 @cindex @samp{qTfV} packet
37194 @cindex @samp{qTsV} packet
37195 These packets request data about trace state variables that are on the
37196 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
37197 and multiple @code{qTsV} to get additional variables. Replies to
37198 these packets follow the syntax of the @code{QTDV} packets that define
37199 trace state variables.
37205 @cindex @samp{qTfSTM} packet
37206 @cindex @samp{qTsSTM} packet
37207 These packets request data about static tracepoint markers that exist
37208 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
37209 first piece of data, and multiple @code{qTsSTM} to get additional
37210 pieces. Replies to these packets take the following form:
37214 @item m @var{address}:@var{id}:@var{extra}
37216 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
37217 a comma-separated list of markers
37219 (lower case letter @samp{L}) denotes end of list.
37221 An error occurred. The error number @var{nn} is given as hex digits.
37223 An empty reply indicates that the request is not supported by the
37227 The @var{address} is encoded in hex;
37228 @var{id} and @var{extra} are strings encoded in hex.
37230 In response to each query, the target will reply with a list of one or
37231 more markers, separated by commas. @value{GDBN} will respond to each
37232 reply with a request for more markers (using the @samp{qs} form of the
37233 query), until the target responds with @samp{l} (lower-case ell, for
37236 @item qTSTMat:@var{address}
37238 @cindex @samp{qTSTMat} packet
37239 This packets requests data about static tracepoint markers in the
37240 target program at @var{address}. Replies to this packet follow the
37241 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
37242 tracepoint markers.
37244 @item QTSave:@var{filename}
37245 @cindex @samp{QTSave} packet
37246 This packet directs the target to save trace data to the file name
37247 @var{filename} in the target's filesystem. The @var{filename} is encoded
37248 as a hex string; the interpretation of the file name (relative vs
37249 absolute, wild cards, etc) is up to the target.
37251 @item qTBuffer:@var{offset},@var{len}
37252 @cindex @samp{qTBuffer} packet
37253 Return up to @var{len} bytes of the current contents of trace buffer,
37254 starting at @var{offset}. The trace buffer is treated as if it were
37255 a contiguous collection of traceframes, as per the trace file format.
37256 The reply consists as many hex-encoded bytes as the target can deliver
37257 in a packet; it is not an error to return fewer than were asked for.
37258 A reply consisting of just @code{l} indicates that no bytes are
37261 @item QTBuffer:circular:@var{value}
37262 This packet directs the target to use a circular trace buffer if
37263 @var{value} is 1, or a linear buffer if the value is 0.
37265 @item QTBuffer:size:@var{size}
37266 @anchor{QTBuffer-size}
37267 @cindex @samp{QTBuffer size} packet
37268 This packet directs the target to make the trace buffer be of size
37269 @var{size} if possible. A value of @code{-1} tells the target to
37270 use whatever size it prefers.
37272 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
37273 @cindex @samp{QTNotes} packet
37274 This packet adds optional textual notes to the trace run. Allowable
37275 types include @code{user}, @code{notes}, and @code{tstop}, the
37276 @var{text} fields are arbitrary strings, hex-encoded.
37280 @subsection Relocate instruction reply packet
37281 When installing fast tracepoints in memory, the target may need to
37282 relocate the instruction currently at the tracepoint address to a
37283 different address in memory. For most instructions, a simple copy is
37284 enough, but, for example, call instructions that implicitly push the
37285 return address on the stack, and relative branches or other
37286 PC-relative instructions require offset adjustment, so that the effect
37287 of executing the instruction at a different address is the same as if
37288 it had executed in the original location.
37290 In response to several of the tracepoint packets, the target may also
37291 respond with a number of intermediate @samp{qRelocInsn} request
37292 packets before the final result packet, to have @value{GDBN} handle
37293 this relocation operation. If a packet supports this mechanism, its
37294 documentation will explicitly say so. See for example the above
37295 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
37296 format of the request is:
37299 @item qRelocInsn:@var{from};@var{to}
37301 This requests @value{GDBN} to copy instruction at address @var{from}
37302 to address @var{to}, possibly adjusted so that executing the
37303 instruction at @var{to} has the same effect as executing it at
37304 @var{from}. @value{GDBN} writes the adjusted instruction to target
37305 memory starting at @var{to}.
37310 @item qRelocInsn:@var{adjusted_size}
37311 Informs the stub the relocation is complete. The @var{adjusted_size} is
37312 the length in bytes of resulting relocated instruction sequence.
37314 A badly formed request was detected, or an error was encountered while
37315 relocating the instruction.
37318 @node Host I/O Packets
37319 @section Host I/O Packets
37320 @cindex Host I/O, remote protocol
37321 @cindex file transfer, remote protocol
37323 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
37324 operations on the far side of a remote link. For example, Host I/O is
37325 used to upload and download files to a remote target with its own
37326 filesystem. Host I/O uses the same constant values and data structure
37327 layout as the target-initiated File-I/O protocol. However, the
37328 Host I/O packets are structured differently. The target-initiated
37329 protocol relies on target memory to store parameters and buffers.
37330 Host I/O requests are initiated by @value{GDBN}, and the
37331 target's memory is not involved. @xref{File-I/O Remote Protocol
37332 Extension}, for more details on the target-initiated protocol.
37334 The Host I/O request packets all encode a single operation along with
37335 its arguments. They have this format:
37339 @item vFile:@var{operation}: @var{parameter}@dots{}
37340 @var{operation} is the name of the particular request; the target
37341 should compare the entire packet name up to the second colon when checking
37342 for a supported operation. The format of @var{parameter} depends on
37343 the operation. Numbers are always passed in hexadecimal. Negative
37344 numbers have an explicit minus sign (i.e.@: two's complement is not
37345 used). Strings (e.g.@: filenames) are encoded as a series of
37346 hexadecimal bytes. The last argument to a system call may be a
37347 buffer of escaped binary data (@pxref{Binary Data}).
37351 The valid responses to Host I/O packets are:
37355 @item F @var{result} [, @var{errno}] [; @var{attachment}]
37356 @var{result} is the integer value returned by this operation, usually
37357 non-negative for success and -1 for errors. If an error has occured,
37358 @var{errno} will be included in the result specifying a
37359 value defined by the File-I/O protocol (@pxref{Errno Values}). For
37360 operations which return data, @var{attachment} supplies the data as a
37361 binary buffer. Binary buffers in response packets are escaped in the
37362 normal way (@pxref{Binary Data}). See the individual packet
37363 documentation for the interpretation of @var{result} and
37367 An empty response indicates that this operation is not recognized.
37371 These are the supported Host I/O operations:
37374 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
37375 Open a file at @var{filename} and return a file descriptor for it, or
37376 return -1 if an error occurs. The @var{filename} is a string,
37377 @var{flags} is an integer indicating a mask of open flags
37378 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
37379 of mode bits to use if the file is created (@pxref{mode_t Values}).
37380 @xref{open}, for details of the open flags and mode values.
37382 @item vFile:close: @var{fd}
37383 Close the open file corresponding to @var{fd} and return 0, or
37384 -1 if an error occurs.
37386 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
37387 Read data from the open file corresponding to @var{fd}. Up to
37388 @var{count} bytes will be read from the file, starting at @var{offset}
37389 relative to the start of the file. The target may read fewer bytes;
37390 common reasons include packet size limits and an end-of-file
37391 condition. The number of bytes read is returned. Zero should only be
37392 returned for a successful read at the end of the file, or if
37393 @var{count} was zero.
37395 The data read should be returned as a binary attachment on success.
37396 If zero bytes were read, the response should include an empty binary
37397 attachment (i.e.@: a trailing semicolon). The return value is the
37398 number of target bytes read; the binary attachment may be longer if
37399 some characters were escaped.
37401 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
37402 Write @var{data} (a binary buffer) to the open file corresponding
37403 to @var{fd}. Start the write at @var{offset} from the start of the
37404 file. Unlike many @code{write} system calls, there is no
37405 separate @var{count} argument; the length of @var{data} in the
37406 packet is used. @samp{vFile:write} returns the number of bytes written,
37407 which may be shorter than the length of @var{data}, or -1 if an
37410 @item vFile:unlink: @var{filename}
37411 Delete the file at @var{filename} on the target. Return 0,
37412 or -1 if an error occurs. The @var{filename} is a string.
37414 @item vFile:readlink: @var{filename}
37415 Read value of symbolic link @var{filename} on the target. Return
37416 the number of bytes read, or -1 if an error occurs.
37418 The data read should be returned as a binary attachment on success.
37419 If zero bytes were read, the response should include an empty binary
37420 attachment (i.e.@: a trailing semicolon). The return value is the
37421 number of target bytes read; the binary attachment may be longer if
37422 some characters were escaped.
37427 @section Interrupts
37428 @cindex interrupts (remote protocol)
37430 When a program on the remote target is running, @value{GDBN} may
37431 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
37432 a @code{BREAK} followed by @code{g},
37433 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
37435 The precise meaning of @code{BREAK} is defined by the transport
37436 mechanism and may, in fact, be undefined. @value{GDBN} does not
37437 currently define a @code{BREAK} mechanism for any of the network
37438 interfaces except for TCP, in which case @value{GDBN} sends the
37439 @code{telnet} BREAK sequence.
37441 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
37442 transport mechanisms. It is represented by sending the single byte
37443 @code{0x03} without any of the usual packet overhead described in
37444 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
37445 transmitted as part of a packet, it is considered to be packet data
37446 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
37447 (@pxref{X packet}), used for binary downloads, may include an unescaped
37448 @code{0x03} as part of its packet.
37450 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
37451 When Linux kernel receives this sequence from serial port,
37452 it stops execution and connects to gdb.
37454 Stubs are not required to recognize these interrupt mechanisms and the
37455 precise meaning associated with receipt of the interrupt is
37456 implementation defined. If the target supports debugging of multiple
37457 threads and/or processes, it should attempt to interrupt all
37458 currently-executing threads and processes.
37459 If the stub is successful at interrupting the
37460 running program, it should send one of the stop
37461 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
37462 of successfully stopping the program in all-stop mode, and a stop reply
37463 for each stopped thread in non-stop mode.
37464 Interrupts received while the
37465 program is stopped are discarded.
37467 @node Notification Packets
37468 @section Notification Packets
37469 @cindex notification packets
37470 @cindex packets, notification
37472 The @value{GDBN} remote serial protocol includes @dfn{notifications},
37473 packets that require no acknowledgment. Both the GDB and the stub
37474 may send notifications (although the only notifications defined at
37475 present are sent by the stub). Notifications carry information
37476 without incurring the round-trip latency of an acknowledgment, and so
37477 are useful for low-impact communications where occasional packet loss
37480 A notification packet has the form @samp{% @var{data} #
37481 @var{checksum}}, where @var{data} is the content of the notification,
37482 and @var{checksum} is a checksum of @var{data}, computed and formatted
37483 as for ordinary @value{GDBN} packets. A notification's @var{data}
37484 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
37485 receiving a notification, the recipient sends no @samp{+} or @samp{-}
37486 to acknowledge the notification's receipt or to report its corruption.
37488 Every notification's @var{data} begins with a name, which contains no
37489 colon characters, followed by a colon character.
37491 Recipients should silently ignore corrupted notifications and
37492 notifications they do not understand. Recipients should restart
37493 timeout periods on receipt of a well-formed notification, whether or
37494 not they understand it.
37496 Senders should only send the notifications described here when this
37497 protocol description specifies that they are permitted. In the
37498 future, we may extend the protocol to permit existing notifications in
37499 new contexts; this rule helps older senders avoid confusing newer
37502 (Older versions of @value{GDBN} ignore bytes received until they see
37503 the @samp{$} byte that begins an ordinary packet, so new stubs may
37504 transmit notifications without fear of confusing older clients. There
37505 are no notifications defined for @value{GDBN} to send at the moment, but we
37506 assume that most older stubs would ignore them, as well.)
37508 Each notification is comprised of three parts:
37510 @item @var{name}:@var{event}
37511 The notification packet is sent by the side that initiates the
37512 exchange (currently, only the stub does that), with @var{event}
37513 carrying the specific information about the notification, and
37514 @var{name} specifying the name of the notification.
37516 The acknowledge sent by the other side, usually @value{GDBN}, to
37517 acknowledge the exchange and request the event.
37520 The purpose of an asynchronous notification mechanism is to report to
37521 @value{GDBN} that something interesting happened in the remote stub.
37523 The remote stub may send notification @var{name}:@var{event}
37524 at any time, but @value{GDBN} acknowledges the notification when
37525 appropriate. The notification event is pending before @value{GDBN}
37526 acknowledges. Only one notification at a time may be pending; if
37527 additional events occur before @value{GDBN} has acknowledged the
37528 previous notification, they must be queued by the stub for later
37529 synchronous transmission in response to @var{ack} packets from
37530 @value{GDBN}. Because the notification mechanism is unreliable,
37531 the stub is permitted to resend a notification if it believes
37532 @value{GDBN} may not have received it.
37534 Specifically, notifications may appear when @value{GDBN} is not
37535 otherwise reading input from the stub, or when @value{GDBN} is
37536 expecting to read a normal synchronous response or a
37537 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
37538 Notification packets are distinct from any other communication from
37539 the stub so there is no ambiguity.
37541 After receiving a notification, @value{GDBN} shall acknowledge it by
37542 sending a @var{ack} packet as a regular, synchronous request to the
37543 stub. Such acknowledgment is not required to happen immediately, as
37544 @value{GDBN} is permitted to send other, unrelated packets to the
37545 stub first, which the stub should process normally.
37547 Upon receiving a @var{ack} packet, if the stub has other queued
37548 events to report to @value{GDBN}, it shall respond by sending a
37549 normal @var{event}. @value{GDBN} shall then send another @var{ack}
37550 packet to solicit further responses; again, it is permitted to send
37551 other, unrelated packets as well which the stub should process
37554 If the stub receives a @var{ack} packet and there are no additional
37555 @var{event} to report, the stub shall return an @samp{OK} response.
37556 At this point, @value{GDBN} has finished processing a notification
37557 and the stub has completed sending any queued events. @value{GDBN}
37558 won't accept any new notifications until the final @samp{OK} is
37559 received . If further notification events occur, the stub shall send
37560 a new notification, @value{GDBN} shall accept the notification, and
37561 the process shall be repeated.
37563 The process of asynchronous notification can be illustrated by the
37566 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
37569 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
37571 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
37576 The following notifications are defined:
37577 @multitable @columnfractions 0.12 0.12 0.38 0.38
37586 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
37587 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
37588 for information on how these notifications are acknowledged by
37590 @tab Report an asynchronous stop event in non-stop mode.
37594 @node Remote Non-Stop
37595 @section Remote Protocol Support for Non-Stop Mode
37597 @value{GDBN}'s remote protocol supports non-stop debugging of
37598 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
37599 supports non-stop mode, it should report that to @value{GDBN} by including
37600 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
37602 @value{GDBN} typically sends a @samp{QNonStop} packet only when
37603 establishing a new connection with the stub. Entering non-stop mode
37604 does not alter the state of any currently-running threads, but targets
37605 must stop all threads in any already-attached processes when entering
37606 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
37607 probe the target state after a mode change.
37609 In non-stop mode, when an attached process encounters an event that
37610 would otherwise be reported with a stop reply, it uses the
37611 asynchronous notification mechanism (@pxref{Notification Packets}) to
37612 inform @value{GDBN}. In contrast to all-stop mode, where all threads
37613 in all processes are stopped when a stop reply is sent, in non-stop
37614 mode only the thread reporting the stop event is stopped. That is,
37615 when reporting a @samp{S} or @samp{T} response to indicate completion
37616 of a step operation, hitting a breakpoint, or a fault, only the
37617 affected thread is stopped; any other still-running threads continue
37618 to run. When reporting a @samp{W} or @samp{X} response, all running
37619 threads belonging to other attached processes continue to run.
37621 In non-stop mode, the target shall respond to the @samp{?} packet as
37622 follows. First, any incomplete stop reply notification/@samp{vStopped}
37623 sequence in progress is abandoned. The target must begin a new
37624 sequence reporting stop events for all stopped threads, whether or not
37625 it has previously reported those events to @value{GDBN}. The first
37626 stop reply is sent as a synchronous reply to the @samp{?} packet, and
37627 subsequent stop replies are sent as responses to @samp{vStopped} packets
37628 using the mechanism described above. The target must not send
37629 asynchronous stop reply notifications until the sequence is complete.
37630 If all threads are running when the target receives the @samp{?} packet,
37631 or if the target is not attached to any process, it shall respond
37634 If the stub supports non-stop mode, it should also support the
37635 @samp{swbreak} stop reason if software breakpoints are supported, and
37636 the @samp{hwbreak} stop reason if hardware breakpoints are supported
37637 (@pxref{swbreak stop reason}). This is because given the asynchronous
37638 nature of non-stop mode, between the time a thread hits a breakpoint
37639 and the time the event is finally processed by @value{GDBN}, the
37640 breakpoint may have already been removed from the target. Due to
37641 this, @value{GDBN} needs to be able to tell whether a trap stop was
37642 caused by a delayed breakpoint event, which should be ignored, as
37643 opposed to a random trap signal, which should be reported to the user.
37644 Note the @samp{swbreak} feature implies that the target is responsible
37645 for adjusting the PC when a software breakpoint triggers, if
37646 necessary, such as on the x86 architecture.
37648 @node Packet Acknowledgment
37649 @section Packet Acknowledgment
37651 @cindex acknowledgment, for @value{GDBN} remote
37652 @cindex packet acknowledgment, for @value{GDBN} remote
37653 By default, when either the host or the target machine receives a packet,
37654 the first response expected is an acknowledgment: either @samp{+} (to indicate
37655 the package was received correctly) or @samp{-} (to request retransmission).
37656 This mechanism allows the @value{GDBN} remote protocol to operate over
37657 unreliable transport mechanisms, such as a serial line.
37659 In cases where the transport mechanism is itself reliable (such as a pipe or
37660 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
37661 It may be desirable to disable them in that case to reduce communication
37662 overhead, or for other reasons. This can be accomplished by means of the
37663 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
37665 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
37666 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
37667 and response format still includes the normal checksum, as described in
37668 @ref{Overview}, but the checksum may be ignored by the receiver.
37670 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
37671 no-acknowledgment mode, it should report that to @value{GDBN}
37672 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
37673 @pxref{qSupported}.
37674 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
37675 disabled via the @code{set remote noack-packet off} command
37676 (@pxref{Remote Configuration}),
37677 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
37678 Only then may the stub actually turn off packet acknowledgments.
37679 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
37680 response, which can be safely ignored by the stub.
37682 Note that @code{set remote noack-packet} command only affects negotiation
37683 between @value{GDBN} and the stub when subsequent connections are made;
37684 it does not affect the protocol acknowledgment state for any current
37686 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
37687 new connection is established,
37688 there is also no protocol request to re-enable the acknowledgments
37689 for the current connection, once disabled.
37694 Example sequence of a target being re-started. Notice how the restart
37695 does not get any direct output:
37700 @emph{target restarts}
37703 <- @code{T001:1234123412341234}
37707 Example sequence of a target being stepped by a single instruction:
37710 -> @code{G1445@dots{}}
37715 <- @code{T001:1234123412341234}
37719 <- @code{1455@dots{}}
37723 @node File-I/O Remote Protocol Extension
37724 @section File-I/O Remote Protocol Extension
37725 @cindex File-I/O remote protocol extension
37728 * File-I/O Overview::
37729 * Protocol Basics::
37730 * The F Request Packet::
37731 * The F Reply Packet::
37732 * The Ctrl-C Message::
37734 * List of Supported Calls::
37735 * Protocol-specific Representation of Datatypes::
37737 * File-I/O Examples::
37740 @node File-I/O Overview
37741 @subsection File-I/O Overview
37742 @cindex file-i/o overview
37744 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
37745 target to use the host's file system and console I/O to perform various
37746 system calls. System calls on the target system are translated into a
37747 remote protocol packet to the host system, which then performs the needed
37748 actions and returns a response packet to the target system.
37749 This simulates file system operations even on targets that lack file systems.
37751 The protocol is defined to be independent of both the host and target systems.
37752 It uses its own internal representation of datatypes and values. Both
37753 @value{GDBN} and the target's @value{GDBN} stub are responsible for
37754 translating the system-dependent value representations into the internal
37755 protocol representations when data is transmitted.
37757 The communication is synchronous. A system call is possible only when
37758 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
37759 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
37760 the target is stopped to allow deterministic access to the target's
37761 memory. Therefore File-I/O is not interruptible by target signals. On
37762 the other hand, it is possible to interrupt File-I/O by a user interrupt
37763 (@samp{Ctrl-C}) within @value{GDBN}.
37765 The target's request to perform a host system call does not finish
37766 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
37767 after finishing the system call, the target returns to continuing the
37768 previous activity (continue, step). No additional continue or step
37769 request from @value{GDBN} is required.
37772 (@value{GDBP}) continue
37773 <- target requests 'system call X'
37774 target is stopped, @value{GDBN} executes system call
37775 -> @value{GDBN} returns result
37776 ... target continues, @value{GDBN} returns to wait for the target
37777 <- target hits breakpoint and sends a Txx packet
37780 The protocol only supports I/O on the console and to regular files on
37781 the host file system. Character or block special devices, pipes,
37782 named pipes, sockets or any other communication method on the host
37783 system are not supported by this protocol.
37785 File I/O is not supported in non-stop mode.
37787 @node Protocol Basics
37788 @subsection Protocol Basics
37789 @cindex protocol basics, file-i/o
37791 The File-I/O protocol uses the @code{F} packet as the request as well
37792 as reply packet. Since a File-I/O system call can only occur when
37793 @value{GDBN} is waiting for a response from the continuing or stepping target,
37794 the File-I/O request is a reply that @value{GDBN} has to expect as a result
37795 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
37796 This @code{F} packet contains all information needed to allow @value{GDBN}
37797 to call the appropriate host system call:
37801 A unique identifier for the requested system call.
37804 All parameters to the system call. Pointers are given as addresses
37805 in the target memory address space. Pointers to strings are given as
37806 pointer/length pair. Numerical values are given as they are.
37807 Numerical control flags are given in a protocol-specific representation.
37811 At this point, @value{GDBN} has to perform the following actions.
37815 If the parameters include pointer values to data needed as input to a
37816 system call, @value{GDBN} requests this data from the target with a
37817 standard @code{m} packet request. This additional communication has to be
37818 expected by the target implementation and is handled as any other @code{m}
37822 @value{GDBN} translates all value from protocol representation to host
37823 representation as needed. Datatypes are coerced into the host types.
37826 @value{GDBN} calls the system call.
37829 It then coerces datatypes back to protocol representation.
37832 If the system call is expected to return data in buffer space specified
37833 by pointer parameters to the call, the data is transmitted to the
37834 target using a @code{M} or @code{X} packet. This packet has to be expected
37835 by the target implementation and is handled as any other @code{M} or @code{X}
37840 Eventually @value{GDBN} replies with another @code{F} packet which contains all
37841 necessary information for the target to continue. This at least contains
37848 @code{errno}, if has been changed by the system call.
37855 After having done the needed type and value coercion, the target continues
37856 the latest continue or step action.
37858 @node The F Request Packet
37859 @subsection The @code{F} Request Packet
37860 @cindex file-i/o request packet
37861 @cindex @code{F} request packet
37863 The @code{F} request packet has the following format:
37866 @item F@var{call-id},@var{parameter@dots{}}
37868 @var{call-id} is the identifier to indicate the host system call to be called.
37869 This is just the name of the function.
37871 @var{parameter@dots{}} are the parameters to the system call.
37872 Parameters are hexadecimal integer values, either the actual values in case
37873 of scalar datatypes, pointers to target buffer space in case of compound
37874 datatypes and unspecified memory areas, or pointer/length pairs in case
37875 of string parameters. These are appended to the @var{call-id} as a
37876 comma-delimited list. All values are transmitted in ASCII
37877 string representation, pointer/length pairs separated by a slash.
37883 @node The F Reply Packet
37884 @subsection The @code{F} Reply Packet
37885 @cindex file-i/o reply packet
37886 @cindex @code{F} reply packet
37888 The @code{F} reply packet has the following format:
37892 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
37894 @var{retcode} is the return code of the system call as hexadecimal value.
37896 @var{errno} is the @code{errno} set by the call, in protocol-specific
37898 This parameter can be omitted if the call was successful.
37900 @var{Ctrl-C flag} is only sent if the user requested a break. In this
37901 case, @var{errno} must be sent as well, even if the call was successful.
37902 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
37909 or, if the call was interrupted before the host call has been performed:
37916 assuming 4 is the protocol-specific representation of @code{EINTR}.
37921 @node The Ctrl-C Message
37922 @subsection The @samp{Ctrl-C} Message
37923 @cindex ctrl-c message, in file-i/o protocol
37925 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
37926 reply packet (@pxref{The F Reply Packet}),
37927 the target should behave as if it had
37928 gotten a break message. The meaning for the target is ``system call
37929 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
37930 (as with a break message) and return to @value{GDBN} with a @code{T02}
37933 It's important for the target to know in which
37934 state the system call was interrupted. There are two possible cases:
37938 The system call hasn't been performed on the host yet.
37941 The system call on the host has been finished.
37945 These two states can be distinguished by the target by the value of the
37946 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
37947 call hasn't been performed. This is equivalent to the @code{EINTR} handling
37948 on POSIX systems. In any other case, the target may presume that the
37949 system call has been finished --- successfully or not --- and should behave
37950 as if the break message arrived right after the system call.
37952 @value{GDBN} must behave reliably. If the system call has not been called
37953 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
37954 @code{errno} in the packet. If the system call on the host has been finished
37955 before the user requests a break, the full action must be finished by
37956 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
37957 The @code{F} packet may only be sent when either nothing has happened
37958 or the full action has been completed.
37961 @subsection Console I/O
37962 @cindex console i/o as part of file-i/o
37964 By default and if not explicitly closed by the target system, the file
37965 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
37966 on the @value{GDBN} console is handled as any other file output operation
37967 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
37968 by @value{GDBN} so that after the target read request from file descriptor
37969 0 all following typing is buffered until either one of the following
37974 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
37976 system call is treated as finished.
37979 The user presses @key{RET}. This is treated as end of input with a trailing
37983 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
37984 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
37988 If the user has typed more characters than fit in the buffer given to
37989 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
37990 either another @code{read(0, @dots{})} is requested by the target, or debugging
37991 is stopped at the user's request.
37994 @node List of Supported Calls
37995 @subsection List of Supported Calls
37996 @cindex list of supported file-i/o calls
38013 @unnumberedsubsubsec open
38014 @cindex open, file-i/o system call
38019 int open(const char *pathname, int flags);
38020 int open(const char *pathname, int flags, mode_t mode);
38024 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
38027 @var{flags} is the bitwise @code{OR} of the following values:
38031 If the file does not exist it will be created. The host
38032 rules apply as far as file ownership and time stamps
38036 When used with @code{O_CREAT}, if the file already exists it is
38037 an error and open() fails.
38040 If the file already exists and the open mode allows
38041 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
38042 truncated to zero length.
38045 The file is opened in append mode.
38048 The file is opened for reading only.
38051 The file is opened for writing only.
38054 The file is opened for reading and writing.
38058 Other bits are silently ignored.
38062 @var{mode} is the bitwise @code{OR} of the following values:
38066 User has read permission.
38069 User has write permission.
38072 Group has read permission.
38075 Group has write permission.
38078 Others have read permission.
38081 Others have write permission.
38085 Other bits are silently ignored.
38088 @item Return value:
38089 @code{open} returns the new file descriptor or -1 if an error
38096 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
38099 @var{pathname} refers to a directory.
38102 The requested access is not allowed.
38105 @var{pathname} was too long.
38108 A directory component in @var{pathname} does not exist.
38111 @var{pathname} refers to a device, pipe, named pipe or socket.
38114 @var{pathname} refers to a file on a read-only filesystem and
38115 write access was requested.
38118 @var{pathname} is an invalid pointer value.
38121 No space on device to create the file.
38124 The process already has the maximum number of files open.
38127 The limit on the total number of files open on the system
38131 The call was interrupted by the user.
38137 @unnumberedsubsubsec close
38138 @cindex close, file-i/o system call
38147 @samp{Fclose,@var{fd}}
38149 @item Return value:
38150 @code{close} returns zero on success, or -1 if an error occurred.
38156 @var{fd} isn't a valid open file descriptor.
38159 The call was interrupted by the user.
38165 @unnumberedsubsubsec read
38166 @cindex read, file-i/o system call
38171 int read(int fd, void *buf, unsigned int count);
38175 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
38177 @item Return value:
38178 On success, the number of bytes read is returned.
38179 Zero indicates end of file. If count is zero, read
38180 returns zero as well. On error, -1 is returned.
38186 @var{fd} is not a valid file descriptor or is not open for
38190 @var{bufptr} is an invalid pointer value.
38193 The call was interrupted by the user.
38199 @unnumberedsubsubsec write
38200 @cindex write, file-i/o system call
38205 int write(int fd, const void *buf, unsigned int count);
38209 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
38211 @item Return value:
38212 On success, the number of bytes written are returned.
38213 Zero indicates nothing was written. On error, -1
38220 @var{fd} is not a valid file descriptor or is not open for
38224 @var{bufptr} is an invalid pointer value.
38227 An attempt was made to write a file that exceeds the
38228 host-specific maximum file size allowed.
38231 No space on device to write the data.
38234 The call was interrupted by the user.
38240 @unnumberedsubsubsec lseek
38241 @cindex lseek, file-i/o system call
38246 long lseek (int fd, long offset, int flag);
38250 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
38252 @var{flag} is one of:
38256 The offset is set to @var{offset} bytes.
38259 The offset is set to its current location plus @var{offset}
38263 The offset is set to the size of the file plus @var{offset}
38267 @item Return value:
38268 On success, the resulting unsigned offset in bytes from
38269 the beginning of the file is returned. Otherwise, a
38270 value of -1 is returned.
38276 @var{fd} is not a valid open file descriptor.
38279 @var{fd} is associated with the @value{GDBN} console.
38282 @var{flag} is not a proper value.
38285 The call was interrupted by the user.
38291 @unnumberedsubsubsec rename
38292 @cindex rename, file-i/o system call
38297 int rename(const char *oldpath, const char *newpath);
38301 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
38303 @item Return value:
38304 On success, zero is returned. On error, -1 is returned.
38310 @var{newpath} is an existing directory, but @var{oldpath} is not a
38314 @var{newpath} is a non-empty directory.
38317 @var{oldpath} or @var{newpath} is a directory that is in use by some
38321 An attempt was made to make a directory a subdirectory
38325 A component used as a directory in @var{oldpath} or new
38326 path is not a directory. Or @var{oldpath} is a directory
38327 and @var{newpath} exists but is not a directory.
38330 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
38333 No access to the file or the path of the file.
38337 @var{oldpath} or @var{newpath} was too long.
38340 A directory component in @var{oldpath} or @var{newpath} does not exist.
38343 The file is on a read-only filesystem.
38346 The device containing the file has no room for the new
38350 The call was interrupted by the user.
38356 @unnumberedsubsubsec unlink
38357 @cindex unlink, file-i/o system call
38362 int unlink(const char *pathname);
38366 @samp{Funlink,@var{pathnameptr}/@var{len}}
38368 @item Return value:
38369 On success, zero is returned. On error, -1 is returned.
38375 No access to the file or the path of the file.
38378 The system does not allow unlinking of directories.
38381 The file @var{pathname} cannot be unlinked because it's
38382 being used by another process.
38385 @var{pathnameptr} is an invalid pointer value.
38388 @var{pathname} was too long.
38391 A directory component in @var{pathname} does not exist.
38394 A component of the path is not a directory.
38397 The file is on a read-only filesystem.
38400 The call was interrupted by the user.
38406 @unnumberedsubsubsec stat/fstat
38407 @cindex fstat, file-i/o system call
38408 @cindex stat, file-i/o system call
38413 int stat(const char *pathname, struct stat *buf);
38414 int fstat(int fd, struct stat *buf);
38418 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
38419 @samp{Ffstat,@var{fd},@var{bufptr}}
38421 @item Return value:
38422 On success, zero is returned. On error, -1 is returned.
38428 @var{fd} is not a valid open file.
38431 A directory component in @var{pathname} does not exist or the
38432 path is an empty string.
38435 A component of the path is not a directory.
38438 @var{pathnameptr} is an invalid pointer value.
38441 No access to the file or the path of the file.
38444 @var{pathname} was too long.
38447 The call was interrupted by the user.
38453 @unnumberedsubsubsec gettimeofday
38454 @cindex gettimeofday, file-i/o system call
38459 int gettimeofday(struct timeval *tv, void *tz);
38463 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
38465 @item Return value:
38466 On success, 0 is returned, -1 otherwise.
38472 @var{tz} is a non-NULL pointer.
38475 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
38481 @unnumberedsubsubsec isatty
38482 @cindex isatty, file-i/o system call
38487 int isatty(int fd);
38491 @samp{Fisatty,@var{fd}}
38493 @item Return value:
38494 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
38500 The call was interrupted by the user.
38505 Note that the @code{isatty} call is treated as a special case: it returns
38506 1 to the target if the file descriptor is attached
38507 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
38508 would require implementing @code{ioctl} and would be more complex than
38513 @unnumberedsubsubsec system
38514 @cindex system, file-i/o system call
38519 int system(const char *command);
38523 @samp{Fsystem,@var{commandptr}/@var{len}}
38525 @item Return value:
38526 If @var{len} is zero, the return value indicates whether a shell is
38527 available. A zero return value indicates a shell is not available.
38528 For non-zero @var{len}, the value returned is -1 on error and the
38529 return status of the command otherwise. Only the exit status of the
38530 command is returned, which is extracted from the host's @code{system}
38531 return value by calling @code{WEXITSTATUS(retval)}. In case
38532 @file{/bin/sh} could not be executed, 127 is returned.
38538 The call was interrupted by the user.
38543 @value{GDBN} takes over the full task of calling the necessary host calls
38544 to perform the @code{system} call. The return value of @code{system} on
38545 the host is simplified before it's returned
38546 to the target. Any termination signal information from the child process
38547 is discarded, and the return value consists
38548 entirely of the exit status of the called command.
38550 Due to security concerns, the @code{system} call is by default refused
38551 by @value{GDBN}. The user has to allow this call explicitly with the
38552 @code{set remote system-call-allowed 1} command.
38555 @item set remote system-call-allowed
38556 @kindex set remote system-call-allowed
38557 Control whether to allow the @code{system} calls in the File I/O
38558 protocol for the remote target. The default is zero (disabled).
38560 @item show remote system-call-allowed
38561 @kindex show remote system-call-allowed
38562 Show whether the @code{system} calls are allowed in the File I/O
38566 @node Protocol-specific Representation of Datatypes
38567 @subsection Protocol-specific Representation of Datatypes
38568 @cindex protocol-specific representation of datatypes, in file-i/o protocol
38571 * Integral Datatypes::
38573 * Memory Transfer::
38578 @node Integral Datatypes
38579 @unnumberedsubsubsec Integral Datatypes
38580 @cindex integral datatypes, in file-i/o protocol
38582 The integral datatypes used in the system calls are @code{int},
38583 @code{unsigned int}, @code{long}, @code{unsigned long},
38584 @code{mode_t}, and @code{time_t}.
38586 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
38587 implemented as 32 bit values in this protocol.
38589 @code{long} and @code{unsigned long} are implemented as 64 bit types.
38591 @xref{Limits}, for corresponding MIN and MAX values (similar to those
38592 in @file{limits.h}) to allow range checking on host and target.
38594 @code{time_t} datatypes are defined as seconds since the Epoch.
38596 All integral datatypes transferred as part of a memory read or write of a
38597 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
38600 @node Pointer Values
38601 @unnumberedsubsubsec Pointer Values
38602 @cindex pointer values, in file-i/o protocol
38604 Pointers to target data are transmitted as they are. An exception
38605 is made for pointers to buffers for which the length isn't
38606 transmitted as part of the function call, namely strings. Strings
38607 are transmitted as a pointer/length pair, both as hex values, e.g.@:
38614 which is a pointer to data of length 18 bytes at position 0x1aaf.
38615 The length is defined as the full string length in bytes, including
38616 the trailing null byte. For example, the string @code{"hello world"}
38617 at address 0x123456 is transmitted as
38623 @node Memory Transfer
38624 @unnumberedsubsubsec Memory Transfer
38625 @cindex memory transfer, in file-i/o protocol
38627 Structured data which is transferred using a memory read or write (for
38628 example, a @code{struct stat}) is expected to be in a protocol-specific format
38629 with all scalar multibyte datatypes being big endian. Translation to
38630 this representation needs to be done both by the target before the @code{F}
38631 packet is sent, and by @value{GDBN} before
38632 it transfers memory to the target. Transferred pointers to structured
38633 data should point to the already-coerced data at any time.
38637 @unnumberedsubsubsec struct stat
38638 @cindex struct stat, in file-i/o protocol
38640 The buffer of type @code{struct stat} used by the target and @value{GDBN}
38641 is defined as follows:
38645 unsigned int st_dev; /* device */
38646 unsigned int st_ino; /* inode */
38647 mode_t st_mode; /* protection */
38648 unsigned int st_nlink; /* number of hard links */
38649 unsigned int st_uid; /* user ID of owner */
38650 unsigned int st_gid; /* group ID of owner */
38651 unsigned int st_rdev; /* device type (if inode device) */
38652 unsigned long st_size; /* total size, in bytes */
38653 unsigned long st_blksize; /* blocksize for filesystem I/O */
38654 unsigned long st_blocks; /* number of blocks allocated */
38655 time_t st_atime; /* time of last access */
38656 time_t st_mtime; /* time of last modification */
38657 time_t st_ctime; /* time of last change */
38661 The integral datatypes conform to the definitions given in the
38662 appropriate section (see @ref{Integral Datatypes}, for details) so this
38663 structure is of size 64 bytes.
38665 The values of several fields have a restricted meaning and/or
38671 A value of 0 represents a file, 1 the console.
38674 No valid meaning for the target. Transmitted unchanged.
38677 Valid mode bits are described in @ref{Constants}. Any other
38678 bits have currently no meaning for the target.
38683 No valid meaning for the target. Transmitted unchanged.
38688 These values have a host and file system dependent
38689 accuracy. Especially on Windows hosts, the file system may not
38690 support exact timing values.
38693 The target gets a @code{struct stat} of the above representation and is
38694 responsible for coercing it to the target representation before
38697 Note that due to size differences between the host, target, and protocol
38698 representations of @code{struct stat} members, these members could eventually
38699 get truncated on the target.
38701 @node struct timeval
38702 @unnumberedsubsubsec struct timeval
38703 @cindex struct timeval, in file-i/o protocol
38705 The buffer of type @code{struct timeval} used by the File-I/O protocol
38706 is defined as follows:
38710 time_t tv_sec; /* second */
38711 long tv_usec; /* microsecond */
38715 The integral datatypes conform to the definitions given in the
38716 appropriate section (see @ref{Integral Datatypes}, for details) so this
38717 structure is of size 8 bytes.
38720 @subsection Constants
38721 @cindex constants, in file-i/o protocol
38723 The following values are used for the constants inside of the
38724 protocol. @value{GDBN} and target are responsible for translating these
38725 values before and after the call as needed.
38736 @unnumberedsubsubsec Open Flags
38737 @cindex open flags, in file-i/o protocol
38739 All values are given in hexadecimal representation.
38751 @node mode_t Values
38752 @unnumberedsubsubsec mode_t Values
38753 @cindex mode_t values, in file-i/o protocol
38755 All values are given in octal representation.
38772 @unnumberedsubsubsec Errno Values
38773 @cindex errno values, in file-i/o protocol
38775 All values are given in decimal representation.
38800 @code{EUNKNOWN} is used as a fallback error value if a host system returns
38801 any error value not in the list of supported error numbers.
38804 @unnumberedsubsubsec Lseek Flags
38805 @cindex lseek flags, in file-i/o protocol
38814 @unnumberedsubsubsec Limits
38815 @cindex limits, in file-i/o protocol
38817 All values are given in decimal representation.
38820 INT_MIN -2147483648
38822 UINT_MAX 4294967295
38823 LONG_MIN -9223372036854775808
38824 LONG_MAX 9223372036854775807
38825 ULONG_MAX 18446744073709551615
38828 @node File-I/O Examples
38829 @subsection File-I/O Examples
38830 @cindex file-i/o examples
38832 Example sequence of a write call, file descriptor 3, buffer is at target
38833 address 0x1234, 6 bytes should be written:
38836 <- @code{Fwrite,3,1234,6}
38837 @emph{request memory read from target}
38840 @emph{return "6 bytes written"}
38844 Example sequence of a read call, file descriptor 3, buffer is at target
38845 address 0x1234, 6 bytes should be read:
38848 <- @code{Fread,3,1234,6}
38849 @emph{request memory write to target}
38850 -> @code{X1234,6:XXXXXX}
38851 @emph{return "6 bytes read"}
38855 Example sequence of a read call, call fails on the host due to invalid
38856 file descriptor (@code{EBADF}):
38859 <- @code{Fread,3,1234,6}
38863 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
38867 <- @code{Fread,3,1234,6}
38872 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
38876 <- @code{Fread,3,1234,6}
38877 -> @code{X1234,6:XXXXXX}
38881 @node Library List Format
38882 @section Library List Format
38883 @cindex library list format, remote protocol
38885 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
38886 same process as your application to manage libraries. In this case,
38887 @value{GDBN} can use the loader's symbol table and normal memory
38888 operations to maintain a list of shared libraries. On other
38889 platforms, the operating system manages loaded libraries.
38890 @value{GDBN} can not retrieve the list of currently loaded libraries
38891 through memory operations, so it uses the @samp{qXfer:libraries:read}
38892 packet (@pxref{qXfer library list read}) instead. The remote stub
38893 queries the target's operating system and reports which libraries
38896 The @samp{qXfer:libraries:read} packet returns an XML document which
38897 lists loaded libraries and their offsets. Each library has an
38898 associated name and one or more segment or section base addresses,
38899 which report where the library was loaded in memory.
38901 For the common case of libraries that are fully linked binaries, the
38902 library should have a list of segments. If the target supports
38903 dynamic linking of a relocatable object file, its library XML element
38904 should instead include a list of allocated sections. The segment or
38905 section bases are start addresses, not relocation offsets; they do not
38906 depend on the library's link-time base addresses.
38908 @value{GDBN} must be linked with the Expat library to support XML
38909 library lists. @xref{Expat}.
38911 A simple memory map, with one loaded library relocated by a single
38912 offset, looks like this:
38916 <library name="/lib/libc.so.6">
38917 <segment address="0x10000000"/>
38922 Another simple memory map, with one loaded library with three
38923 allocated sections (.text, .data, .bss), looks like this:
38927 <library name="sharedlib.o">
38928 <section address="0x10000000"/>
38929 <section address="0x20000000"/>
38930 <section address="0x30000000"/>
38935 The format of a library list is described by this DTD:
38938 <!-- library-list: Root element with versioning -->
38939 <!ELEMENT library-list (library)*>
38940 <!ATTLIST library-list version CDATA #FIXED "1.0">
38941 <!ELEMENT library (segment*, section*)>
38942 <!ATTLIST library name CDATA #REQUIRED>
38943 <!ELEMENT segment EMPTY>
38944 <!ATTLIST segment address CDATA #REQUIRED>
38945 <!ELEMENT section EMPTY>
38946 <!ATTLIST section address CDATA #REQUIRED>
38949 In addition, segments and section descriptors cannot be mixed within a
38950 single library element, and you must supply at least one segment or
38951 section for each library.
38953 @node Library List Format for SVR4 Targets
38954 @section Library List Format for SVR4 Targets
38955 @cindex library list format, remote protocol
38957 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
38958 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
38959 shared libraries. Still a special library list provided by this packet is
38960 more efficient for the @value{GDBN} remote protocol.
38962 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
38963 loaded libraries and their SVR4 linker parameters. For each library on SVR4
38964 target, the following parameters are reported:
38968 @code{name}, the absolute file name from the @code{l_name} field of
38969 @code{struct link_map}.
38971 @code{lm} with address of @code{struct link_map} used for TLS
38972 (Thread Local Storage) access.
38974 @code{l_addr}, the displacement as read from the field @code{l_addr} of
38975 @code{struct link_map}. For prelinked libraries this is not an absolute
38976 memory address. It is a displacement of absolute memory address against
38977 address the file was prelinked to during the library load.
38979 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
38982 Additionally the single @code{main-lm} attribute specifies address of
38983 @code{struct link_map} used for the main executable. This parameter is used
38984 for TLS access and its presence is optional.
38986 @value{GDBN} must be linked with the Expat library to support XML
38987 SVR4 library lists. @xref{Expat}.
38989 A simple memory map, with two loaded libraries (which do not use prelink),
38993 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
38994 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
38996 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
38998 </library-list-svr>
39001 The format of an SVR4 library list is described by this DTD:
39004 <!-- library-list-svr4: Root element with versioning -->
39005 <!ELEMENT library-list-svr4 (library)*>
39006 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
39007 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
39008 <!ELEMENT library EMPTY>
39009 <!ATTLIST library name CDATA #REQUIRED>
39010 <!ATTLIST library lm CDATA #REQUIRED>
39011 <!ATTLIST library l_addr CDATA #REQUIRED>
39012 <!ATTLIST library l_ld CDATA #REQUIRED>
39015 @node Memory Map Format
39016 @section Memory Map Format
39017 @cindex memory map format
39019 To be able to write into flash memory, @value{GDBN} needs to obtain a
39020 memory map from the target. This section describes the format of the
39023 The memory map is obtained using the @samp{qXfer:memory-map:read}
39024 (@pxref{qXfer memory map read}) packet and is an XML document that
39025 lists memory regions.
39027 @value{GDBN} must be linked with the Expat library to support XML
39028 memory maps. @xref{Expat}.
39030 The top-level structure of the document is shown below:
39033 <?xml version="1.0"?>
39034 <!DOCTYPE memory-map
39035 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
39036 "http://sourceware.org/gdb/gdb-memory-map.dtd">
39042 Each region can be either:
39047 A region of RAM starting at @var{addr} and extending for @var{length}
39051 <memory type="ram" start="@var{addr}" length="@var{length}"/>
39056 A region of read-only memory:
39059 <memory type="rom" start="@var{addr}" length="@var{length}"/>
39064 A region of flash memory, with erasure blocks @var{blocksize}
39068 <memory type="flash" start="@var{addr}" length="@var{length}">
39069 <property name="blocksize">@var{blocksize}</property>
39075 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
39076 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
39077 packets to write to addresses in such ranges.
39079 The formal DTD for memory map format is given below:
39082 <!-- ................................................... -->
39083 <!-- Memory Map XML DTD ................................ -->
39084 <!-- File: memory-map.dtd .............................. -->
39085 <!-- .................................... .............. -->
39086 <!-- memory-map.dtd -->
39087 <!-- memory-map: Root element with versioning -->
39088 <!ELEMENT memory-map (memory | property)>
39089 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
39090 <!ELEMENT memory (property)>
39091 <!-- memory: Specifies a memory region,
39092 and its type, or device. -->
39093 <!ATTLIST memory type CDATA #REQUIRED
39094 start CDATA #REQUIRED
39095 length CDATA #REQUIRED
39096 device CDATA #IMPLIED>
39097 <!-- property: Generic attribute tag -->
39098 <!ELEMENT property (#PCDATA | property)*>
39099 <!ATTLIST property name CDATA #REQUIRED>
39102 @node Thread List Format
39103 @section Thread List Format
39104 @cindex thread list format
39106 To efficiently update the list of threads and their attributes,
39107 @value{GDBN} issues the @samp{qXfer:threads:read} packet
39108 (@pxref{qXfer threads read}) and obtains the XML document with
39109 the following structure:
39112 <?xml version="1.0"?>
39114 <thread id="id" core="0">
39115 ... description ...
39120 Each @samp{thread} element must have the @samp{id} attribute that
39121 identifies the thread (@pxref{thread-id syntax}). The
39122 @samp{core} attribute, if present, specifies which processor core
39123 the thread was last executing on. The content of the of @samp{thread}
39124 element is interpreted as human-readable auxilliary information.
39126 @node Traceframe Info Format
39127 @section Traceframe Info Format
39128 @cindex traceframe info format
39130 To be able to know which objects in the inferior can be examined when
39131 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
39132 memory ranges, registers and trace state variables that have been
39133 collected in a traceframe.
39135 This list is obtained using the @samp{qXfer:traceframe-info:read}
39136 (@pxref{qXfer traceframe info read}) packet and is an XML document.
39138 @value{GDBN} must be linked with the Expat library to support XML
39139 traceframe info discovery. @xref{Expat}.
39141 The top-level structure of the document is shown below:
39144 <?xml version="1.0"?>
39145 <!DOCTYPE traceframe-info
39146 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
39147 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
39153 Each traceframe block can be either:
39158 A region of collected memory starting at @var{addr} and extending for
39159 @var{length} bytes from there:
39162 <memory start="@var{addr}" length="@var{length}"/>
39166 A block indicating trace state variable numbered @var{number} has been
39170 <tvar id="@var{number}"/>
39175 The formal DTD for the traceframe info format is given below:
39178 <!ELEMENT traceframe-info (memory | tvar)* >
39179 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
39181 <!ELEMENT memory EMPTY>
39182 <!ATTLIST memory start CDATA #REQUIRED
39183 length CDATA #REQUIRED>
39185 <!ATTLIST tvar id CDATA #REQUIRED>
39188 @node Branch Trace Format
39189 @section Branch Trace Format
39190 @cindex branch trace format
39192 In order to display the branch trace of an inferior thread,
39193 @value{GDBN} needs to obtain the list of branches. This list is
39194 represented as list of sequential code blocks that are connected via
39195 branches. The code in each block has been executed sequentially.
39197 This list is obtained using the @samp{qXfer:btrace:read}
39198 (@pxref{qXfer btrace read}) packet and is an XML document.
39200 @value{GDBN} must be linked with the Expat library to support XML
39201 traceframe info discovery. @xref{Expat}.
39203 The top-level structure of the document is shown below:
39206 <?xml version="1.0"?>
39208 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
39209 "http://sourceware.org/gdb/gdb-btrace.dtd">
39218 A block of sequentially executed instructions starting at @var{begin}
39219 and ending at @var{end}:
39222 <block begin="@var{begin}" end="@var{end}"/>
39227 The formal DTD for the branch trace format is given below:
39230 <!ELEMENT btrace (block)* >
39231 <!ATTLIST btrace version CDATA #FIXED "1.0">
39233 <!ELEMENT block EMPTY>
39234 <!ATTLIST block begin CDATA #REQUIRED
39235 end CDATA #REQUIRED>
39238 @node Branch Trace Configuration Format
39239 @section Branch Trace Configuration Format
39240 @cindex branch trace configuration format
39242 For each inferior thread, @value{GDBN} can obtain the branch trace
39243 configuration using the @samp{qXfer:btrace-conf:read}
39244 (@pxref{qXfer btrace-conf read}) packet.
39246 The configuration describes the branch trace format and configuration
39247 settings for that format. The following information is described:
39251 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
39254 The size of the @acronym{BTS} ring buffer in bytes.
39258 @value{GDBN} must be linked with the Expat library to support XML
39259 branch trace configuration discovery. @xref{Expat}.
39261 The formal DTD for the branch trace configuration format is given below:
39264 <!ELEMENT btrace-conf (bts?)>
39265 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
39267 <!ELEMENT bts EMPTY>
39268 <!ATTLIST bts size CDATA #IMPLIED>
39271 @include agentexpr.texi
39273 @node Target Descriptions
39274 @appendix Target Descriptions
39275 @cindex target descriptions
39277 One of the challenges of using @value{GDBN} to debug embedded systems
39278 is that there are so many minor variants of each processor
39279 architecture in use. It is common practice for vendors to start with
39280 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
39281 and then make changes to adapt it to a particular market niche. Some
39282 architectures have hundreds of variants, available from dozens of
39283 vendors. This leads to a number of problems:
39287 With so many different customized processors, it is difficult for
39288 the @value{GDBN} maintainers to keep up with the changes.
39290 Since individual variants may have short lifetimes or limited
39291 audiences, it may not be worthwhile to carry information about every
39292 variant in the @value{GDBN} source tree.
39294 When @value{GDBN} does support the architecture of the embedded system
39295 at hand, the task of finding the correct architecture name to give the
39296 @command{set architecture} command can be error-prone.
39299 To address these problems, the @value{GDBN} remote protocol allows a
39300 target system to not only identify itself to @value{GDBN}, but to
39301 actually describe its own features. This lets @value{GDBN} support
39302 processor variants it has never seen before --- to the extent that the
39303 descriptions are accurate, and that @value{GDBN} understands them.
39305 @value{GDBN} must be linked with the Expat library to support XML
39306 target descriptions. @xref{Expat}.
39309 * Retrieving Descriptions:: How descriptions are fetched from a target.
39310 * Target Description Format:: The contents of a target description.
39311 * Predefined Target Types:: Standard types available for target
39313 * Standard Target Features:: Features @value{GDBN} knows about.
39316 @node Retrieving Descriptions
39317 @section Retrieving Descriptions
39319 Target descriptions can be read from the target automatically, or
39320 specified by the user manually. The default behavior is to read the
39321 description from the target. @value{GDBN} retrieves it via the remote
39322 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
39323 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
39324 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
39325 XML document, of the form described in @ref{Target Description
39328 Alternatively, you can specify a file to read for the target description.
39329 If a file is set, the target will not be queried. The commands to
39330 specify a file are:
39333 @cindex set tdesc filename
39334 @item set tdesc filename @var{path}
39335 Read the target description from @var{path}.
39337 @cindex unset tdesc filename
39338 @item unset tdesc filename
39339 Do not read the XML target description from a file. @value{GDBN}
39340 will use the description supplied by the current target.
39342 @cindex show tdesc filename
39343 @item show tdesc filename
39344 Show the filename to read for a target description, if any.
39348 @node Target Description Format
39349 @section Target Description Format
39350 @cindex target descriptions, XML format
39352 A target description annex is an @uref{http://www.w3.org/XML/, XML}
39353 document which complies with the Document Type Definition provided in
39354 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
39355 means you can use generally available tools like @command{xmllint} to
39356 check that your feature descriptions are well-formed and valid.
39357 However, to help people unfamiliar with XML write descriptions for
39358 their targets, we also describe the grammar here.
39360 Target descriptions can identify the architecture of the remote target
39361 and (for some architectures) provide information about custom register
39362 sets. They can also identify the OS ABI of the remote target.
39363 @value{GDBN} can use this information to autoconfigure for your
39364 target, or to warn you if you connect to an unsupported target.
39366 Here is a simple target description:
39369 <target version="1.0">
39370 <architecture>i386:x86-64</architecture>
39375 This minimal description only says that the target uses
39376 the x86-64 architecture.
39378 A target description has the following overall form, with [ ] marking
39379 optional elements and @dots{} marking repeatable elements. The elements
39380 are explained further below.
39383 <?xml version="1.0"?>
39384 <!DOCTYPE target SYSTEM "gdb-target.dtd">
39385 <target version="1.0">
39386 @r{[}@var{architecture}@r{]}
39387 @r{[}@var{osabi}@r{]}
39388 @r{[}@var{compatible}@r{]}
39389 @r{[}@var{feature}@dots{}@r{]}
39394 The description is generally insensitive to whitespace and line
39395 breaks, under the usual common-sense rules. The XML version
39396 declaration and document type declaration can generally be omitted
39397 (@value{GDBN} does not require them), but specifying them may be
39398 useful for XML validation tools. The @samp{version} attribute for
39399 @samp{<target>} may also be omitted, but we recommend
39400 including it; if future versions of @value{GDBN} use an incompatible
39401 revision of @file{gdb-target.dtd}, they will detect and report
39402 the version mismatch.
39404 @subsection Inclusion
39405 @cindex target descriptions, inclusion
39408 @cindex <xi:include>
39411 It can sometimes be valuable to split a target description up into
39412 several different annexes, either for organizational purposes, or to
39413 share files between different possible target descriptions. You can
39414 divide a description into multiple files by replacing any element of
39415 the target description with an inclusion directive of the form:
39418 <xi:include href="@var{document}"/>
39422 When @value{GDBN} encounters an element of this form, it will retrieve
39423 the named XML @var{document}, and replace the inclusion directive with
39424 the contents of that document. If the current description was read
39425 using @samp{qXfer}, then so will be the included document;
39426 @var{document} will be interpreted as the name of an annex. If the
39427 current description was read from a file, @value{GDBN} will look for
39428 @var{document} as a file in the same directory where it found the
39429 original description.
39431 @subsection Architecture
39432 @cindex <architecture>
39434 An @samp{<architecture>} element has this form:
39437 <architecture>@var{arch}</architecture>
39440 @var{arch} is one of the architectures from the set accepted by
39441 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
39444 @cindex @code{<osabi>}
39446 This optional field was introduced in @value{GDBN} version 7.0.
39447 Previous versions of @value{GDBN} ignore it.
39449 An @samp{<osabi>} element has this form:
39452 <osabi>@var{abi-name}</osabi>
39455 @var{abi-name} is an OS ABI name from the same selection accepted by
39456 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
39458 @subsection Compatible Architecture
39459 @cindex @code{<compatible>}
39461 This optional field was introduced in @value{GDBN} version 7.0.
39462 Previous versions of @value{GDBN} ignore it.
39464 A @samp{<compatible>} element has this form:
39467 <compatible>@var{arch}</compatible>
39470 @var{arch} is one of the architectures from the set accepted by
39471 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
39473 A @samp{<compatible>} element is used to specify that the target
39474 is able to run binaries in some other than the main target architecture
39475 given by the @samp{<architecture>} element. For example, on the
39476 Cell Broadband Engine, the main architecture is @code{powerpc:common}
39477 or @code{powerpc:common64}, but the system is able to run binaries
39478 in the @code{spu} architecture as well. The way to describe this
39479 capability with @samp{<compatible>} is as follows:
39482 <architecture>powerpc:common</architecture>
39483 <compatible>spu</compatible>
39486 @subsection Features
39489 Each @samp{<feature>} describes some logical portion of the target
39490 system. Features are currently used to describe available CPU
39491 registers and the types of their contents. A @samp{<feature>} element
39495 <feature name="@var{name}">
39496 @r{[}@var{type}@dots{}@r{]}
39502 Each feature's name should be unique within the description. The name
39503 of a feature does not matter unless @value{GDBN} has some special
39504 knowledge of the contents of that feature; if it does, the feature
39505 should have its standard name. @xref{Standard Target Features}.
39509 Any register's value is a collection of bits which @value{GDBN} must
39510 interpret. The default interpretation is a two's complement integer,
39511 but other types can be requested by name in the register description.
39512 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
39513 Target Types}), and the description can define additional composite types.
39515 Each type element must have an @samp{id} attribute, which gives
39516 a unique (within the containing @samp{<feature>}) name to the type.
39517 Types must be defined before they are used.
39520 Some targets offer vector registers, which can be treated as arrays
39521 of scalar elements. These types are written as @samp{<vector>} elements,
39522 specifying the array element type, @var{type}, and the number of elements,
39526 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
39530 If a register's value is usefully viewed in multiple ways, define it
39531 with a union type containing the useful representations. The
39532 @samp{<union>} element contains one or more @samp{<field>} elements,
39533 each of which has a @var{name} and a @var{type}:
39536 <union id="@var{id}">
39537 <field name="@var{name}" type="@var{type}"/>
39543 If a register's value is composed from several separate values, define
39544 it with a structure type. There are two forms of the @samp{<struct>}
39545 element; a @samp{<struct>} element must either contain only bitfields
39546 or contain no bitfields. If the structure contains only bitfields,
39547 its total size in bytes must be specified, each bitfield must have an
39548 explicit start and end, and bitfields are automatically assigned an
39549 integer type. The field's @var{start} should be less than or
39550 equal to its @var{end}, and zero represents the least significant bit.
39553 <struct id="@var{id}" size="@var{size}">
39554 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
39559 If the structure contains no bitfields, then each field has an
39560 explicit type, and no implicit padding is added.
39563 <struct id="@var{id}">
39564 <field name="@var{name}" type="@var{type}"/>
39570 If a register's value is a series of single-bit flags, define it with
39571 a flags type. The @samp{<flags>} element has an explicit @var{size}
39572 and contains one or more @samp{<field>} elements. Each field has a
39573 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
39577 <flags id="@var{id}" size="@var{size}">
39578 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
39583 @subsection Registers
39586 Each register is represented as an element with this form:
39589 <reg name="@var{name}"
39590 bitsize="@var{size}"
39591 @r{[}regnum="@var{num}"@r{]}
39592 @r{[}save-restore="@var{save-restore}"@r{]}
39593 @r{[}type="@var{type}"@r{]}
39594 @r{[}group="@var{group}"@r{]}/>
39598 The components are as follows:
39603 The register's name; it must be unique within the target description.
39606 The register's size, in bits.
39609 The register's number. If omitted, a register's number is one greater
39610 than that of the previous register (either in the current feature or in
39611 a preceding feature); the first register in the target description
39612 defaults to zero. This register number is used to read or write
39613 the register; e.g.@: it is used in the remote @code{p} and @code{P}
39614 packets, and registers appear in the @code{g} and @code{G} packets
39615 in order of increasing register number.
39618 Whether the register should be preserved across inferior function
39619 calls; this must be either @code{yes} or @code{no}. The default is
39620 @code{yes}, which is appropriate for most registers except for
39621 some system control registers; this is not related to the target's
39625 The type of the register. It may be a predefined type, a type
39626 defined in the current feature, or one of the special types @code{int}
39627 and @code{float}. @code{int} is an integer type of the correct size
39628 for @var{bitsize}, and @code{float} is a floating point type (in the
39629 architecture's normal floating point format) of the correct size for
39630 @var{bitsize}. The default is @code{int}.
39633 The register group to which this register belongs. It must
39634 be either @code{general}, @code{float}, or @code{vector}. If no
39635 @var{group} is specified, @value{GDBN} will not display the register
39636 in @code{info registers}.
39640 @node Predefined Target Types
39641 @section Predefined Target Types
39642 @cindex target descriptions, predefined types
39644 Type definitions in the self-description can build up composite types
39645 from basic building blocks, but can not define fundamental types. Instead,
39646 standard identifiers are provided by @value{GDBN} for the fundamental
39647 types. The currently supported types are:
39656 Signed integer types holding the specified number of bits.
39663 Unsigned integer types holding the specified number of bits.
39667 Pointers to unspecified code and data. The program counter and
39668 any dedicated return address register may be marked as code
39669 pointers; printing a code pointer converts it into a symbolic
39670 address. The stack pointer and any dedicated address registers
39671 may be marked as data pointers.
39674 Single precision IEEE floating point.
39677 Double precision IEEE floating point.
39680 The 12-byte extended precision format used by ARM FPA registers.
39683 The 10-byte extended precision format used by x87 registers.
39686 32bit @sc{eflags} register used by x86.
39689 32bit @sc{mxcsr} register used by x86.
39693 @node Standard Target Features
39694 @section Standard Target Features
39695 @cindex target descriptions, standard features
39697 A target description must contain either no registers or all the
39698 target's registers. If the description contains no registers, then
39699 @value{GDBN} will assume a default register layout, selected based on
39700 the architecture. If the description contains any registers, the
39701 default layout will not be used; the standard registers must be
39702 described in the target description, in such a way that @value{GDBN}
39703 can recognize them.
39705 This is accomplished by giving specific names to feature elements
39706 which contain standard registers. @value{GDBN} will look for features
39707 with those names and verify that they contain the expected registers;
39708 if any known feature is missing required registers, or if any required
39709 feature is missing, @value{GDBN} will reject the target
39710 description. You can add additional registers to any of the
39711 standard features --- @value{GDBN} will display them just as if
39712 they were added to an unrecognized feature.
39714 This section lists the known features and their expected contents.
39715 Sample XML documents for these features are included in the
39716 @value{GDBN} source tree, in the directory @file{gdb/features}.
39718 Names recognized by @value{GDBN} should include the name of the
39719 company or organization which selected the name, and the overall
39720 architecture to which the feature applies; so e.g.@: the feature
39721 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
39723 The names of registers are not case sensitive for the purpose
39724 of recognizing standard features, but @value{GDBN} will only display
39725 registers using the capitalization used in the description.
39728 * AArch64 Features::
39731 * MicroBlaze Features::
39734 * Nios II Features::
39735 * PowerPC Features::
39736 * S/390 and System z Features::
39741 @node AArch64 Features
39742 @subsection AArch64 Features
39743 @cindex target descriptions, AArch64 features
39745 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
39746 targets. It should contain registers @samp{x0} through @samp{x30},
39747 @samp{sp}, @samp{pc}, and @samp{cpsr}.
39749 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
39750 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
39754 @subsection ARM Features
39755 @cindex target descriptions, ARM features
39757 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
39759 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
39760 @samp{lr}, @samp{pc}, and @samp{cpsr}.
39762 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
39763 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
39764 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
39767 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
39768 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
39770 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
39771 it should contain at least registers @samp{wR0} through @samp{wR15} and
39772 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
39773 @samp{wCSSF}, and @samp{wCASF} registers are optional.
39775 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
39776 should contain at least registers @samp{d0} through @samp{d15}. If
39777 they are present, @samp{d16} through @samp{d31} should also be included.
39778 @value{GDBN} will synthesize the single-precision registers from
39779 halves of the double-precision registers.
39781 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
39782 need to contain registers; it instructs @value{GDBN} to display the
39783 VFP double-precision registers as vectors and to synthesize the
39784 quad-precision registers from pairs of double-precision registers.
39785 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
39786 be present and include 32 double-precision registers.
39788 @node i386 Features
39789 @subsection i386 Features
39790 @cindex target descriptions, i386 features
39792 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
39793 targets. It should describe the following registers:
39797 @samp{eax} through @samp{edi} plus @samp{eip} for i386
39799 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
39801 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
39802 @samp{fs}, @samp{gs}
39804 @samp{st0} through @samp{st7}
39806 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
39807 @samp{foseg}, @samp{fooff} and @samp{fop}
39810 The register sets may be different, depending on the target.
39812 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
39813 describe registers:
39817 @samp{xmm0} through @samp{xmm7} for i386
39819 @samp{xmm0} through @samp{xmm15} for amd64
39824 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
39825 @samp{org.gnu.gdb.i386.sse} feature. It should
39826 describe the upper 128 bits of @sc{ymm} registers:
39830 @samp{ymm0h} through @samp{ymm7h} for i386
39832 @samp{ymm0h} through @samp{ymm15h} for amd64
39835 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel(R)
39836 Memory Protection Extension (MPX). It should describe the following registers:
39840 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
39842 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
39845 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
39846 describe a single register, @samp{orig_eax}.
39848 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
39849 @samp{org.gnu.gdb.i386.avx} feature. It should
39850 describe additional @sc{xmm} registers:
39854 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
39857 It should describe the upper 128 bits of additional @sc{ymm} registers:
39861 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
39865 describe the upper 256 bits of @sc{zmm} registers:
39869 @samp{zmm0h} through @samp{zmm7h} for i386.
39871 @samp{zmm0h} through @samp{zmm15h} for amd64.
39875 describe the additional @sc{zmm} registers:
39879 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
39882 @node MicroBlaze Features
39883 @subsection MicroBlaze Features
39884 @cindex target descriptions, MicroBlaze features
39886 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
39887 targets. It should contain registers @samp{r0} through @samp{r31},
39888 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
39889 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
39890 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
39892 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
39893 If present, it should contain registers @samp{rshr} and @samp{rslr}
39895 @node MIPS Features
39896 @subsection @acronym{MIPS} Features
39897 @cindex target descriptions, @acronym{MIPS} features
39899 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
39900 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
39901 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
39904 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
39905 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
39906 registers. They may be 32-bit or 64-bit depending on the target.
39908 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
39909 it may be optional in a future version of @value{GDBN}. It should
39910 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
39911 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
39913 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
39914 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
39915 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
39916 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
39918 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
39919 contain a single register, @samp{restart}, which is used by the
39920 Linux kernel to control restartable syscalls.
39922 @node M68K Features
39923 @subsection M68K Features
39924 @cindex target descriptions, M68K features
39927 @item @samp{org.gnu.gdb.m68k.core}
39928 @itemx @samp{org.gnu.gdb.coldfire.core}
39929 @itemx @samp{org.gnu.gdb.fido.core}
39930 One of those features must be always present.
39931 The feature that is present determines which flavor of m68k is
39932 used. The feature that is present should contain registers
39933 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
39934 @samp{sp}, @samp{ps} and @samp{pc}.
39936 @item @samp{org.gnu.gdb.coldfire.fp}
39937 This feature is optional. If present, it should contain registers
39938 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
39942 @node Nios II Features
39943 @subsection Nios II Features
39944 @cindex target descriptions, Nios II features
39946 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
39947 targets. It should contain the 32 core registers (@samp{zero},
39948 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
39949 @samp{pc}, and the 16 control registers (@samp{status} through
39952 @node PowerPC Features
39953 @subsection PowerPC Features
39954 @cindex target descriptions, PowerPC features
39956 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
39957 targets. It should contain registers @samp{r0} through @samp{r31},
39958 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
39959 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
39961 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
39962 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
39964 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
39965 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
39968 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
39969 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
39970 will combine these registers with the floating point registers
39971 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
39972 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
39973 through @samp{vs63}, the set of vector registers for POWER7.
39975 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
39976 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
39977 @samp{spefscr}. SPE targets should provide 32-bit registers in
39978 @samp{org.gnu.gdb.power.core} and provide the upper halves in
39979 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
39980 these to present registers @samp{ev0} through @samp{ev31} to the
39983 @node S/390 and System z Features
39984 @subsection S/390 and System z Features
39985 @cindex target descriptions, S/390 features
39986 @cindex target descriptions, System z features
39988 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
39989 System z targets. It should contain the PSW and the 16 general
39990 registers. In particular, System z targets should provide the 64-bit
39991 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
39992 S/390 targets should provide the 32-bit versions of these registers.
39993 A System z target that runs in 31-bit addressing mode should provide
39994 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
39995 register's upper halves @samp{r0h} through @samp{r15h}, and their
39996 lower halves @samp{r0l} through @samp{r15l}.
39998 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
39999 contain the 64-bit registers @samp{f0} through @samp{f15}, and
40002 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
40003 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
40005 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
40006 contain the register @samp{orig_r2}, which is 64-bit wide on System z
40007 targets and 32-bit otherwise. In addition, the feature may contain
40008 the @samp{last_break} register, whose width depends on the addressing
40009 mode, as well as the @samp{system_call} register, which is always
40012 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
40013 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
40014 @samp{atia}, and @samp{tr0} through @samp{tr15}.
40016 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
40017 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
40018 combined by @value{GDBN} with the floating point registers @samp{f0}
40019 through @samp{f15} to present the 128-bit wide vector registers
40020 @samp{v0} through @samp{v15}. In addition, this feature should
40021 contain the 128-bit wide vector registers @samp{v16} through
40024 @node TIC6x Features
40025 @subsection TMS320C6x Features
40026 @cindex target descriptions, TIC6x features
40027 @cindex target descriptions, TMS320C6x features
40028 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
40029 targets. It should contain registers @samp{A0} through @samp{A15},
40030 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
40032 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
40033 contain registers @samp{A16} through @samp{A31} and @samp{B16}
40034 through @samp{B31}.
40036 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
40037 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
40039 @node Operating System Information
40040 @appendix Operating System Information
40041 @cindex operating system information
40047 Users of @value{GDBN} often wish to obtain information about the state of
40048 the operating system running on the target---for example the list of
40049 processes, or the list of open files. This section describes the
40050 mechanism that makes it possible. This mechanism is similar to the
40051 target features mechanism (@pxref{Target Descriptions}), but focuses
40052 on a different aspect of target.
40054 Operating system information is retrived from the target via the
40055 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
40056 read}). The object name in the request should be @samp{osdata}, and
40057 the @var{annex} identifies the data to be fetched.
40060 @appendixsection Process list
40061 @cindex operating system information, process list
40063 When requesting the process list, the @var{annex} field in the
40064 @samp{qXfer} request should be @samp{processes}. The returned data is
40065 an XML document. The formal syntax of this document is defined in
40066 @file{gdb/features/osdata.dtd}.
40068 An example document is:
40071 <?xml version="1.0"?>
40072 <!DOCTYPE target SYSTEM "osdata.dtd">
40073 <osdata type="processes">
40075 <column name="pid">1</column>
40076 <column name="user">root</column>
40077 <column name="command">/sbin/init</column>
40078 <column name="cores">1,2,3</column>
40083 Each item should include a column whose name is @samp{pid}. The value
40084 of that column should identify the process on the target. The
40085 @samp{user} and @samp{command} columns are optional, and will be
40086 displayed by @value{GDBN}. The @samp{cores} column, if present,
40087 should contain a comma-separated list of cores that this process
40088 is running on. Target may provide additional columns,
40089 which @value{GDBN} currently ignores.
40091 @node Trace File Format
40092 @appendix Trace File Format
40093 @cindex trace file format
40095 The trace file comes in three parts: a header, a textual description
40096 section, and a trace frame section with binary data.
40098 The header has the form @code{\x7fTRACE0\n}. The first byte is
40099 @code{0x7f} so as to indicate that the file contains binary data,
40100 while the @code{0} is a version number that may have different values
40103 The description section consists of multiple lines of @sc{ascii} text
40104 separated by newline characters (@code{0xa}). The lines may include a
40105 variety of optional descriptive or context-setting information, such
40106 as tracepoint definitions or register set size. @value{GDBN} will
40107 ignore any line that it does not recognize. An empty line marks the end
40110 @c FIXME add some specific types of data
40112 The trace frame section consists of a number of consecutive frames.
40113 Each frame begins with a two-byte tracepoint number, followed by a
40114 four-byte size giving the amount of data in the frame. The data in
40115 the frame consists of a number of blocks, each introduced by a
40116 character indicating its type (at least register, memory, and trace
40117 state variable). The data in this section is raw binary, not a
40118 hexadecimal or other encoding; its endianness matches the target's
40121 @c FIXME bi-arch may require endianness/arch info in description section
40124 @item R @var{bytes}
40125 Register block. The number and ordering of bytes matches that of a
40126 @code{g} packet in the remote protocol. Note that these are the
40127 actual bytes, in target order and @value{GDBN} register order, not a
40128 hexadecimal encoding.
40130 @item M @var{address} @var{length} @var{bytes}...
40131 Memory block. This is a contiguous block of memory, at the 8-byte
40132 address @var{address}, with a 2-byte length @var{length}, followed by
40133 @var{length} bytes.
40135 @item V @var{number} @var{value}
40136 Trace state variable block. This records the 8-byte signed value
40137 @var{value} of trace state variable numbered @var{number}.
40141 Future enhancements of the trace file format may include additional types
40144 @node Index Section Format
40145 @appendix @code{.gdb_index} section format
40146 @cindex .gdb_index section format
40147 @cindex index section format
40149 This section documents the index section that is created by @code{save
40150 gdb-index} (@pxref{Index Files}). The index section is
40151 DWARF-specific; some knowledge of DWARF is assumed in this
40154 The mapped index file format is designed to be directly
40155 @code{mmap}able on any architecture. In most cases, a datum is
40156 represented using a little-endian 32-bit integer value, called an
40157 @code{offset_type}. Big endian machines must byte-swap the values
40158 before using them. Exceptions to this rule are noted. The data is
40159 laid out such that alignment is always respected.
40161 A mapped index consists of several areas, laid out in order.
40165 The file header. This is a sequence of values, of @code{offset_type}
40166 unless otherwise noted:
40170 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
40171 Version 4 uses a different hashing function from versions 5 and 6.
40172 Version 6 includes symbols for inlined functions, whereas versions 4
40173 and 5 do not. Version 7 adds attributes to the CU indices in the
40174 symbol table. Version 8 specifies that symbols from DWARF type units
40175 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
40176 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
40178 @value{GDBN} will only read version 4, 5, or 6 indices
40179 by specifying @code{set use-deprecated-index-sections on}.
40180 GDB has a workaround for potentially broken version 7 indices so it is
40181 currently not flagged as deprecated.
40184 The offset, from the start of the file, of the CU list.
40187 The offset, from the start of the file, of the types CU list. Note
40188 that this area can be empty, in which case this offset will be equal
40189 to the next offset.
40192 The offset, from the start of the file, of the address area.
40195 The offset, from the start of the file, of the symbol table.
40198 The offset, from the start of the file, of the constant pool.
40202 The CU list. This is a sequence of pairs of 64-bit little-endian
40203 values, sorted by the CU offset. The first element in each pair is
40204 the offset of a CU in the @code{.debug_info} section. The second
40205 element in each pair is the length of that CU. References to a CU
40206 elsewhere in the map are done using a CU index, which is just the
40207 0-based index into this table. Note that if there are type CUs, then
40208 conceptually CUs and type CUs form a single list for the purposes of
40212 The types CU list. This is a sequence of triplets of 64-bit
40213 little-endian values. In a triplet, the first value is the CU offset,
40214 the second value is the type offset in the CU, and the third value is
40215 the type signature. The types CU list is not sorted.
40218 The address area. The address area consists of a sequence of address
40219 entries. Each address entry has three elements:
40223 The low address. This is a 64-bit little-endian value.
40226 The high address. This is a 64-bit little-endian value. Like
40227 @code{DW_AT_high_pc}, the value is one byte beyond the end.
40230 The CU index. This is an @code{offset_type} value.
40234 The symbol table. This is an open-addressed hash table. The size of
40235 the hash table is always a power of 2.
40237 Each slot in the hash table consists of a pair of @code{offset_type}
40238 values. The first value is the offset of the symbol's name in the
40239 constant pool. The second value is the offset of the CU vector in the
40242 If both values are 0, then this slot in the hash table is empty. This
40243 is ok because while 0 is a valid constant pool index, it cannot be a
40244 valid index for both a string and a CU vector.
40246 The hash value for a table entry is computed by applying an
40247 iterative hash function to the symbol's name. Starting with an
40248 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
40249 the string is incorporated into the hash using the formula depending on the
40254 The formula is @code{r = r * 67 + c - 113}.
40256 @item Versions 5 to 7
40257 The formula is @code{r = r * 67 + tolower (c) - 113}.
40260 The terminating @samp{\0} is not incorporated into the hash.
40262 The step size used in the hash table is computed via
40263 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
40264 value, and @samp{size} is the size of the hash table. The step size
40265 is used to find the next candidate slot when handling a hash
40268 The names of C@t{++} symbols in the hash table are canonicalized. We
40269 don't currently have a simple description of the canonicalization
40270 algorithm; if you intend to create new index sections, you must read
40274 The constant pool. This is simply a bunch of bytes. It is organized
40275 so that alignment is correct: CU vectors are stored first, followed by
40278 A CU vector in the constant pool is a sequence of @code{offset_type}
40279 values. The first value is the number of CU indices in the vector.
40280 Each subsequent value is the index and symbol attributes of a CU in
40281 the CU list. This element in the hash table is used to indicate which
40282 CUs define the symbol and how the symbol is used.
40283 See below for the format of each CU index+attributes entry.
40285 A string in the constant pool is zero-terminated.
40288 Attributes were added to CU index values in @code{.gdb_index} version 7.
40289 If a symbol has multiple uses within a CU then there is one
40290 CU index+attributes value for each use.
40292 The format of each CU index+attributes entry is as follows
40298 This is the index of the CU in the CU list.
40300 These bits are reserved for future purposes and must be zero.
40302 The kind of the symbol in the CU.
40306 This value is reserved and should not be used.
40307 By reserving zero the full @code{offset_type} value is backwards compatible
40308 with previous versions of the index.
40310 The symbol is a type.
40312 The symbol is a variable or an enum value.
40314 The symbol is a function.
40316 Any other kind of symbol.
40318 These values are reserved.
40322 This bit is zero if the value is global and one if it is static.
40324 The determination of whether a symbol is global or static is complicated.
40325 The authorative reference is the file @file{dwarf2read.c} in
40326 @value{GDBN} sources.
40330 This pseudo-code describes the computation of a symbol's kind and
40331 global/static attributes in the index.
40334 is_external = get_attribute (die, DW_AT_external);
40335 language = get_attribute (cu_die, DW_AT_language);
40338 case DW_TAG_typedef:
40339 case DW_TAG_base_type:
40340 case DW_TAG_subrange_type:
40344 case DW_TAG_enumerator:
40346 is_static = (language != CPLUS && language != JAVA);
40348 case DW_TAG_subprogram:
40350 is_static = ! (is_external || language == ADA);
40352 case DW_TAG_constant:
40354 is_static = ! is_external;
40356 case DW_TAG_variable:
40358 is_static = ! is_external;
40360 case DW_TAG_namespace:
40364 case DW_TAG_class_type:
40365 case DW_TAG_interface_type:
40366 case DW_TAG_structure_type:
40367 case DW_TAG_union_type:
40368 case DW_TAG_enumeration_type:
40370 is_static = (language != CPLUS && language != JAVA);
40378 @appendix Manual pages
40382 * gdb man:: The GNU Debugger man page
40383 * gdbserver man:: Remote Server for the GNU Debugger man page
40384 * gcore man:: Generate a core file of a running program
40385 * gdbinit man:: gdbinit scripts
40391 @c man title gdb The GNU Debugger
40393 @c man begin SYNOPSIS gdb
40394 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
40395 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
40396 [@option{-b}@w{ }@var{bps}]
40397 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
40398 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
40399 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
40400 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
40401 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
40404 @c man begin DESCRIPTION gdb
40405 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
40406 going on ``inside'' another program while it executes -- or what another
40407 program was doing at the moment it crashed.
40409 @value{GDBN} can do four main kinds of things (plus other things in support of
40410 these) to help you catch bugs in the act:
40414 Start your program, specifying anything that might affect its behavior.
40417 Make your program stop on specified conditions.
40420 Examine what has happened, when your program has stopped.
40423 Change things in your program, so you can experiment with correcting the
40424 effects of one bug and go on to learn about another.
40427 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
40430 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
40431 commands from the terminal until you tell it to exit with the @value{GDBN}
40432 command @code{quit}. You can get online help from @value{GDBN} itself
40433 by using the command @code{help}.
40435 You can run @code{gdb} with no arguments or options; but the most
40436 usual way to start @value{GDBN} is with one argument or two, specifying an
40437 executable program as the argument:
40443 You can also start with both an executable program and a core file specified:
40449 You can, instead, specify a process ID as a second argument, if you want
40450 to debug a running process:
40458 would attach @value{GDBN} to process @code{1234} (unless you also have a file
40459 named @file{1234}; @value{GDBN} does check for a core file first).
40460 With option @option{-p} you can omit the @var{program} filename.
40462 Here are some of the most frequently needed @value{GDBN} commands:
40464 @c pod2man highlights the right hand side of the @item lines.
40466 @item break [@var{file}:]@var{functiop}
40467 Set a breakpoint at @var{function} (in @var{file}).
40469 @item run [@var{arglist}]
40470 Start your program (with @var{arglist}, if specified).
40473 Backtrace: display the program stack.
40475 @item print @var{expr}
40476 Display the value of an expression.
40479 Continue running your program (after stopping, e.g. at a breakpoint).
40482 Execute next program line (after stopping); step @emph{over} any
40483 function calls in the line.
40485 @item edit [@var{file}:]@var{function}
40486 look at the program line where it is presently stopped.
40488 @item list [@var{file}:]@var{function}
40489 type the text of the program in the vicinity of where it is presently stopped.
40492 Execute next program line (after stopping); step @emph{into} any
40493 function calls in the line.
40495 @item help [@var{name}]
40496 Show information about @value{GDBN} command @var{name}, or general information
40497 about using @value{GDBN}.
40500 Exit from @value{GDBN}.
40504 For full details on @value{GDBN},
40505 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
40506 by Richard M. Stallman and Roland H. Pesch. The same text is available online
40507 as the @code{gdb} entry in the @code{info} program.
40511 @c man begin OPTIONS gdb
40512 Any arguments other than options specify an executable
40513 file and core file (or process ID); that is, the first argument
40514 encountered with no
40515 associated option flag is equivalent to a @option{-se} option, and the second,
40516 if any, is equivalent to a @option{-c} option if it's the name of a file.
40518 both long and short forms; both are shown here. The long forms are also
40519 recognized if you truncate them, so long as enough of the option is
40520 present to be unambiguous. (If you prefer, you can flag option
40521 arguments with @option{+} rather than @option{-}, though we illustrate the
40522 more usual convention.)
40524 All the options and command line arguments you give are processed
40525 in sequential order. The order makes a difference when the @option{-x}
40531 List all options, with brief explanations.
40533 @item -symbols=@var{file}
40534 @itemx -s @var{file}
40535 Read symbol table from file @var{file}.
40538 Enable writing into executable and core files.
40540 @item -exec=@var{file}
40541 @itemx -e @var{file}
40542 Use file @var{file} as the executable file to execute when
40543 appropriate, and for examining pure data in conjunction with a core
40546 @item -se=@var{file}
40547 Read symbol table from file @var{file} and use it as the executable
40550 @item -core=@var{file}
40551 @itemx -c @var{file}
40552 Use file @var{file} as a core dump to examine.
40554 @item -command=@var{file}
40555 @itemx -x @var{file}
40556 Execute @value{GDBN} commands from file @var{file}.
40558 @item -ex @var{command}
40559 Execute given @value{GDBN} @var{command}.
40561 @item -directory=@var{directory}
40562 @itemx -d @var{directory}
40563 Add @var{directory} to the path to search for source files.
40566 Do not execute commands from @file{~/.gdbinit}.
40570 Do not execute commands from any @file{.gdbinit} initialization files.
40574 ``Quiet''. Do not print the introductory and copyright messages. These
40575 messages are also suppressed in batch mode.
40578 Run in batch mode. Exit with status @code{0} after processing all the command
40579 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
40580 Exit with nonzero status if an error occurs in executing the @value{GDBN}
40581 commands in the command files.
40583 Batch mode may be useful for running @value{GDBN} as a filter, for example to
40584 download and run a program on another computer; in order to make this
40585 more useful, the message
40588 Program exited normally.
40592 (which is ordinarily issued whenever a program running under @value{GDBN} control
40593 terminates) is not issued when running in batch mode.
40595 @item -cd=@var{directory}
40596 Run @value{GDBN} using @var{directory} as its working directory,
40597 instead of the current directory.
40601 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
40602 @value{GDBN} to output the full file name and line number in a standard,
40603 recognizable fashion each time a stack frame is displayed (which
40604 includes each time the program stops). This recognizable format looks
40605 like two @samp{\032} characters, followed by the file name, line number
40606 and character position separated by colons, and a newline. The
40607 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
40608 characters as a signal to display the source code for the frame.
40611 Set the line speed (baud rate or bits per second) of any serial
40612 interface used by @value{GDBN} for remote debugging.
40614 @item -tty=@var{device}
40615 Run using @var{device} for your program's standard input and output.
40619 @c man begin SEEALSO gdb
40621 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
40622 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
40623 documentation are properly installed at your site, the command
40630 should give you access to the complete manual.
40632 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
40633 Richard M. Stallman and Roland H. Pesch, July 1991.
40637 @node gdbserver man
40638 @heading gdbserver man
40640 @c man title gdbserver Remote Server for the GNU Debugger
40642 @c man begin SYNOPSIS gdbserver
40643 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
40645 gdbserver --attach @var{comm} @var{pid}
40647 gdbserver --multi @var{comm}
40651 @c man begin DESCRIPTION gdbserver
40652 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
40653 than the one which is running the program being debugged.
40656 @subheading Usage (server (target) side)
40659 Usage (server (target) side):
40662 First, you need to have a copy of the program you want to debug put onto
40663 the target system. The program can be stripped to save space if needed, as
40664 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
40665 the @value{GDBN} running on the host system.
40667 To use the server, you log on to the target system, and run the @command{gdbserver}
40668 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
40669 your program, and (c) its arguments. The general syntax is:
40672 target> gdbserver @var{comm} @var{program} [@var{args} ...]
40675 For example, using a serial port, you might say:
40679 @c @file would wrap it as F</dev/com1>.
40680 target> gdbserver /dev/com1 emacs foo.txt
40683 target> gdbserver @file{/dev/com1} emacs foo.txt
40687 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
40688 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
40689 waits patiently for the host @value{GDBN} to communicate with it.
40691 To use a TCP connection, you could say:
40694 target> gdbserver host:2345 emacs foo.txt
40697 This says pretty much the same thing as the last example, except that we are
40698 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
40699 that we are expecting to see a TCP connection from @code{host} to local TCP port
40700 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
40701 want for the port number as long as it does not conflict with any existing TCP
40702 ports on the target system. This same port number must be used in the host
40703 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
40704 you chose a port number that conflicts with another service, @command{gdbserver} will
40705 print an error message and exit.
40707 @command{gdbserver} can also attach to running programs.
40708 This is accomplished via the @option{--attach} argument. The syntax is:
40711 target> gdbserver --attach @var{comm} @var{pid}
40714 @var{pid} is the process ID of a currently running process. It isn't
40715 necessary to point @command{gdbserver} at a binary for the running process.
40717 To start @code{gdbserver} without supplying an initial command to run
40718 or process ID to attach, use the @option{--multi} command line option.
40719 In such case you should connect using @kbd{target extended-remote} to start
40720 the program you want to debug.
40723 target> gdbserver --multi @var{comm}
40727 @subheading Usage (host side)
40733 You need an unstripped copy of the target program on your host system, since
40734 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
40735 would, with the target program as the first argument. (You may need to use the
40736 @option{--baud} option if the serial line is running at anything except 9600 baud.)
40737 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
40738 new command you need to know about is @code{target remote}
40739 (or @code{target extended-remote}). Its argument is either
40740 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
40741 descriptor. For example:
40745 @c @file would wrap it as F</dev/ttyb>.
40746 (gdb) target remote /dev/ttyb
40749 (gdb) target remote @file{/dev/ttyb}
40754 communicates with the server via serial line @file{/dev/ttyb}, and:
40757 (gdb) target remote the-target:2345
40761 communicates via a TCP connection to port 2345 on host `the-target', where
40762 you previously started up @command{gdbserver} with the same port number. Note that for
40763 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
40764 command, otherwise you may get an error that looks something like
40765 `Connection refused'.
40767 @command{gdbserver} can also debug multiple inferiors at once,
40770 the @value{GDBN} manual in node @code{Inferiors and Programs}
40771 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
40774 @ref{Inferiors and Programs}.
40776 In such case use the @code{extended-remote} @value{GDBN} command variant:
40779 (gdb) target extended-remote the-target:2345
40782 The @command{gdbserver} option @option{--multi} may or may not be used in such
40786 @c man begin OPTIONS gdbserver
40787 There are three different modes for invoking @command{gdbserver}:
40792 Debug a specific program specified by its program name:
40795 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
40798 The @var{comm} parameter specifies how should the server communicate
40799 with @value{GDBN}; it is either a device name (to use a serial line),
40800 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
40801 stdin/stdout of @code{gdbserver}. Specify the name of the program to
40802 debug in @var{prog}. Any remaining arguments will be passed to the
40803 program verbatim. When the program exits, @value{GDBN} will close the
40804 connection, and @code{gdbserver} will exit.
40807 Debug a specific program by specifying the process ID of a running
40811 gdbserver --attach @var{comm} @var{pid}
40814 The @var{comm} parameter is as described above. Supply the process ID
40815 of a running program in @var{pid}; @value{GDBN} will do everything
40816 else. Like with the previous mode, when the process @var{pid} exits,
40817 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
40820 Multi-process mode -- debug more than one program/process:
40823 gdbserver --multi @var{comm}
40826 In this mode, @value{GDBN} can instruct @command{gdbserver} which
40827 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
40828 close the connection when a process being debugged exits, so you can
40829 debug several processes in the same session.
40832 In each of the modes you may specify these options:
40837 List all options, with brief explanations.
40840 This option causes @command{gdbserver} to print its version number and exit.
40843 @command{gdbserver} will attach to a running program. The syntax is:
40846 target> gdbserver --attach @var{comm} @var{pid}
40849 @var{pid} is the process ID of a currently running process. It isn't
40850 necessary to point @command{gdbserver} at a binary for the running process.
40853 To start @code{gdbserver} without supplying an initial command to run
40854 or process ID to attach, use this command line option.
40855 Then you can connect using @kbd{target extended-remote} and start
40856 the program you want to debug. The syntax is:
40859 target> gdbserver --multi @var{comm}
40863 Instruct @code{gdbserver} to display extra status information about the debugging
40865 This option is intended for @code{gdbserver} development and for bug reports to
40868 @item --remote-debug
40869 Instruct @code{gdbserver} to display remote protocol debug output.
40870 This option is intended for @code{gdbserver} development and for bug reports to
40873 @item --debug-format=option1@r{[},option2,...@r{]}
40874 Instruct @code{gdbserver} to include extra information in each line
40875 of debugging output.
40876 @xref{Other Command-Line Arguments for gdbserver}.
40879 Specify a wrapper to launch programs
40880 for debugging. The option should be followed by the name of the
40881 wrapper, then any command-line arguments to pass to the wrapper, then
40882 @kbd{--} indicating the end of the wrapper arguments.
40885 By default, @command{gdbserver} keeps the listening TCP port open, so that
40886 additional connections are possible. However, if you start @code{gdbserver}
40887 with the @option{--once} option, it will stop listening for any further
40888 connection attempts after connecting to the first @value{GDBN} session.
40890 @c --disable-packet is not documented for users.
40892 @c --disable-randomization and --no-disable-randomization are superseded by
40893 @c QDisableRandomization.
40898 @c man begin SEEALSO gdbserver
40900 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
40901 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
40902 documentation are properly installed at your site, the command
40908 should give you access to the complete manual.
40910 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
40911 Richard M. Stallman and Roland H. Pesch, July 1991.
40918 @c man title gcore Generate a core file of a running program
40921 @c man begin SYNOPSIS gcore
40922 gcore [-o @var{filename}] @var{pid}
40926 @c man begin DESCRIPTION gcore
40927 Generate a core dump of a running program with process ID @var{pid}.
40928 Produced file is equivalent to a kernel produced core file as if the process
40929 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
40930 limit). Unlike after a crash, after @command{gcore} the program remains
40931 running without any change.
40934 @c man begin OPTIONS gcore
40936 @item -o @var{filename}
40937 The optional argument
40938 @var{filename} specifies the file name where to put the core dump.
40939 If not specified, the file name defaults to @file{core.@var{pid}},
40940 where @var{pid} is the running program process ID.
40944 @c man begin SEEALSO gcore
40946 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
40947 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
40948 documentation are properly installed at your site, the command
40955 should give you access to the complete manual.
40957 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
40958 Richard M. Stallman and Roland H. Pesch, July 1991.
40965 @c man title gdbinit GDB initialization scripts
40968 @c man begin SYNOPSIS gdbinit
40969 @ifset SYSTEM_GDBINIT
40970 @value{SYSTEM_GDBINIT}
40979 @c man begin DESCRIPTION gdbinit
40980 These files contain @value{GDBN} commands to automatically execute during
40981 @value{GDBN} startup. The lines of contents are canned sequences of commands,
40984 the @value{GDBN} manual in node @code{Sequences}
40985 -- shell command @code{info -f gdb -n Sequences}.
40991 Please read more in
40993 the @value{GDBN} manual in node @code{Startup}
40994 -- shell command @code{info -f gdb -n Startup}.
41001 @ifset SYSTEM_GDBINIT
41002 @item @value{SYSTEM_GDBINIT}
41004 @ifclear SYSTEM_GDBINIT
41005 @item (not enabled with @code{--with-system-gdbinit} during compilation)
41007 System-wide initialization file. It is executed unless user specified
41008 @value{GDBN} option @code{-nx} or @code{-n}.
41011 the @value{GDBN} manual in node @code{System-wide configuration}
41012 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
41015 @ref{System-wide configuration}.
41019 User initialization file. It is executed unless user specified
41020 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
41023 Initialization file for current directory. It may need to be enabled with
41024 @value{GDBN} security command @code{set auto-load local-gdbinit}.
41027 the @value{GDBN} manual in node @code{Init File in the Current Directory}
41028 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
41031 @ref{Init File in the Current Directory}.
41036 @c man begin SEEALSO gdbinit
41038 gdb(1), @code{info -f gdb -n Startup}
41040 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41041 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41042 documentation are properly installed at your site, the command
41048 should give you access to the complete manual.
41050 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41051 Richard M. Stallman and Roland H. Pesch, July 1991.
41057 @node GNU Free Documentation License
41058 @appendix GNU Free Documentation License
41061 @node Concept Index
41062 @unnumbered Concept Index
41066 @node Command and Variable Index
41067 @unnumbered Command, Variable, and Function Index
41072 % I think something like @@colophon should be in texinfo. In the
41074 \long\def\colophon{\hbox to0pt{}\vfill
41075 \centerline{The body of this manual is set in}
41076 \centerline{\fontname\tenrm,}
41077 \centerline{with headings in {\bf\fontname\tenbf}}
41078 \centerline{and examples in {\tt\fontname\tentt}.}
41079 \centerline{{\it\fontname\tenit\/},}
41080 \centerline{{\bf\fontname\tenbf}, and}
41081 \centerline{{\sl\fontname\tensl\/}}
41082 \centerline{are used for emphasis.}\vfill}
41084 % Blame: doc@@cygnus.com, 1991.